Report

ASR	Air Sensitive Receiver
BMP	Best Management Practice
BOD₅	5-Day Biochemical Oxygen Demand
COD	Chemical Oxygen Demand
CRTN	Calculation of Road Traffic Noise
DIA	Drainage Impact Assessment
DO	Dissolved Oxygen
DP	Designated Project
EIA	Environmental Impact Assessment
EIAO	Environmental Impact Assessment Ordinance
EPD	Environmental Protection Department
ETWBTC	Environment, Transport and Works Bureau Technical Circular
GCL	Geosynthetic clay liner
HDPE	High density polyethylene
HKPSG	Hong Kong Planning Standards and Guidelines
IWMF	Integrated Waste Management Facilities
MSW	Municipal solid waste
NCO	Noise Control Ordinance
NENT	North East New Territories
NSR	Noise Sensitive Receiver
OZP	Outline Zoning Plan
PCB	Polychlorinated Biphenyl
ProPECC	Environmental Protection Department Practice Note for Professional Persons
SBA	Stockpile and Borrow Area
SBR	Sequencing Batch Reactor
SENT	South East New Territories
SPL	Sound Pressure Levels
SS	Suspended Solid
SWHSTW	Shek Wu Hui Sewage Treatment Works
SWL	Sound Power Levels
TKN	Total Kjeldahl Nitrogen
TM-EIAO	Technical Memorandum on Environmental Impact Assessment Process (Environmental Impact Assessment Ordinance, Cap. 499, S.16)
TM-Places	TM for the Assessment of Noise from Places other than Domestic Premises, Public Places or Construction Sites
TM-PP	Technical Memorandum on Noise from Percussive Piling
TM-DA	Technical Memorandum on Noise from Construction Work in Designated Areas
TM-GW	Technical Memorandum on Noise from Construction Work other than Percussive Piling
TM-Water	Technical Memorandum on Standards for Effluent Discharged into Drainage and Sewerage System, Inland and Coastal Waters
TN	Total Nitrogen
TOC	Total Organic Carbon
TSS	Total Suspended Solid
TTSAS	Tong To Shan Archaeological Site
USEPA	United State Environmental Protection Agency
WCZ	Water Control Zone
WENT	West New Territories
WHO	World Health Organization
WPCO	Water Pollution Control Ordinance
WRFP	Waste Reduction Framework Plan
WSR	Water Sensitive Receiver
WQI	Water Quality Indexes
WQO	Water Quality Objective

1 Introduction

1.1 Project Background

Currently, about 6 million tonnes of waste are disposed each year at the three strategic landfills in Hong Kong, including the West New Territories (WENT) Landfill, the South East New Territories (SENT) Landfill, and the North East New Territories (NENT) Landfill.

At time of commissioning, the three landfills with a total capacity in the order of 140 Mm³ were expected to be able to meet the waste disposal needs of Hong Kong until 2020 or beyond. The actual waste disposal rate at the landfills has been, however, higher than expected. It is thus projected that the three existing landfills would last only until early-to-mid next decade.

To tackle the problem, further efforts have been taken to reduce and recycle waste. Also, the HKSAR Government has planned to develop Integrated Waste Management Facilities (IWMF) to substantially reduce the volume of waste requiring landfill disposal. Yet these measures could not obviate totally the need for new landfill capacity in Hong Kong, especially as the implementation of IWMF will take time and as its residues will still need to be disposed.

The Environmental Protection Department (EPD) of the HKSAR Government therefore commissioned a Study in Year 2000 on the Extension of Existing Landfills and Identification of Potential New Waste Disposal Sites. Amongst the potential sites recommended in this territory-wide study is an extension of the existing NENT Landfill, with a target capacity of about 19 Mm³. As shown in the attached Drawing No. 24315/01/001, the proposed Extension, of about 70 ha, is located immediately east of the existing NENT Landfill. A large proportion of the Extension area is in fact the borrow/stockpiling area of the existing landfill. Drawing No. 24315/01/005 depicts the general topography at/around the Extension site, showing that it is generally in the form of a bowl bounded by Robin’s Nest and Wo Keng Shan.

In February 2005, EPD appointed Ove Arup & Partners Hong Kong Ltd. to undertake a detailed feasibility study for the NENT Landfill Extension (hereafter referred to “the Project”), with the following key tasks: formulation and evaluation of layout options for the landfill extension; EIA study; and conceptual design of landfill facilities.

1.2 Purpose and Scope of the EIA Study

The purpose of this EIA Study is to provide information on the nature and extent of environmental impacts arising from the construction, operation, restoration and aftercare stages of the NENT Landfill Extension, and to contribute to decisions on the overall acceptability of the Project, after the implementation of environmental mitigation measures.

The NENT Landfill Extension is a Designated Project under Schedule 2, G.1, of the EIAO : “A landfill for waste as defined in the Waste Disposal Ordinance (Cap. 354)”. The EIA study, undertaken under the NENT Landfill Extension Feasibility Study, has therefore been carried out in strict accordance with the EIAO, including the requirements stipulated in EIA Study Brief No. ESB-114/2004 issued under the EIAO.

Drawing No. 24315/01/001 shows the location of the Project site.

1.3 EIA Study Area

The EIA study areas for the impact assessments on air quality, noise, water quality, landfill gas, ecology, landscape & visual and cultural heritage as defined in accordance with the requirements in the EIA Study Brief and are presented in Table 1.1 below.

Table 1.1: Study areas for various assessments

Aspect	Study Area	Remarks
Air Quality	within 500m from the Project Boundary	According to the study brief requirements with additional ASRs selected between 500 to 2000m.
Noise	within 300m from the Project Boundary	According to the study brief requirements with additional NSRs selected between 300 to 1800m.
Water Quality and Aquatic Ecology	within 500m from the Project Boundary	According to the study brief requirements, with additional WSRs such as nearby watercourses, the associated water systems and the coastal water of Deep Bay and Starling Inlet.
Landfill gas	within 250m from the Project Boundary	According to the study brief requirements
Landscape	within 500m from the Project Boundary	According to the study brief requirements
Visual	visual envelope	According to the study brief requirements
Cultural Heritage	within 50m from the Project Boundary	According to the study brief requirements
Terrestrial Ecology	within 500m from the Project Boundary	According to the study brief requirements.

1.4 The Approach

The EIA study has been prepared in accordance with the guidelines provided in Annex 11 of the TM-EIAO for the report contents and Annexes 12 to 19 for the impact assessments of various environmental issues. The general approaches and methodologies adopted for this EIA study are described below.

1.4.1 Description of the Environment

The characteristics of the existing environment were reviewed for identification and prediction of environmental impacts. Baseline surveys were conducted to determine the existing environmental conditions on the Project site and in any environs likely to be affected by the Project. The baseline conditions of the key issues as identified in the EIA Study Brief including air quality, noise, water quality, landscape & visual, cultural heritage and ecology are described in the assessment.

1.4.2 Impact Prediction

The EIA Study was undertaken in accordance with the guidelines on assessment methodologies given in Annexes 12 to 19 of the TM-EIAO. Quantitative predicting tools were employed for assessing the environmental impacts in respect of construction dust, operational air quality, construction noise, operational noise and water quality. The predictions were conducted based on well-recognized methods such as Arup plant noise impact analysis for construction activities, CRTN for evaluating operational road traffic noise impact, ISCST3 for evaluating fugitive and odorous source impacts, and hydrogeological model for evaluating the change of groundwater flow regime.

The applied methodologies for the Project had previously been adopted in other EIA studies. They have been generally accepted for use in predicting environmental impacts and for comparison of assessment results with the TM-EIAO requirements. Limitations are however envisaged of these methodologies. The accuracy of the prediction result will be affected by the degree of uncertainty in input data such as construction plant, air emission inventories and predicted traffic flow. Quantitative uncertainties in the prediction have been considered when drawing conclusion from the assessment results. In carrying out the prediction, realistic worst-case assumptions have been made in order to provide a conservative assessment of environmental impacts.

1.4.3 Impact Evaluation

The predicted changes and effects as a result of the Project were evaluated with respect to the criteria described in Annexes 4 to 10 of the TM-EIAO, and were in quantitative terms as far as practicable.

1.4.4 Impact Mitigation

Mitigation measures have been identified and evaluated to avoid, minimize or remedy the impacts. Priority was given to avoidance of impacts as a primary means of mitigation. The effectiveness of mitigation measures was assessed and the residual environmental impacts identified. Evaluation of impact was made with respect to the criteria described in Annexes 4 to 10 of the TM-EIAO, in quantitative terms as far as practicable.

1.5 Structure of the EIA Report

The structure of this EIA Report is outlined below for ease of reference:

Chapter	Title	Aims
1	Introduction	To provide project background, purpose and scope of the EIA Study and to define the EIA study area.
2	Description of the Project	To describe the project requirements, consideration of alternative and major activities in the Project.
3	Air Quality Impact	To assess the potential air quality impact of the Project and suggest mitigation measures.
4	Noise Impact	To assess the potential noise impact of the Project and suggest mitigation measures.
5	Water Quality Impact	To assess the potential water quality impact of the Project and suggest mitigation measures.
6	Waste Management Implications	To assess the potential waste management implications of the Project and suggest mitigation measures.
7	Landfill Gas Hazards	To assess the potential hazards arising from landfill gas migration and suggest precautionary measures.
8	Landscape and Visual Impact	To assess the potential landscape and visual impacts of the Project and suggest mitigation measures.
9	Impact on Cultural Heritage	To assess the potential impacts of the Project on cultural heritage and suggest mitigation measures.
10	Ecological Impact	To assess the potential ecological impacts of the Project and suggest mitigation measures.
11	Summary of Environmental Outcome	To summarise the key environmental outcomes arising from the EIA Study.
12	Environmental Monitoring and Audit Requirements	To define the scope of the EM&A requirements for the Project.
13	3-Dimensional EIA	To describe the 3-Dimensional EIA for this Study.
14	Conclusion	To conclude the assessment results of the EIA Study.

2 Description of the Project

2.1 General Description of the Project

The development of the NENT Landfill Extension (hereafter referred to “the Project”) will involve the following works:

· Site formation and preparation.

· Installation of liner system.

· Installation of leachate collection, treatment and disposal facilities.

· Installation of gas collection, utilization and management facilities.

· Utilities provisions and drainage diversion.

· Operation of landfill.

· Restoration and aftercare in subsequent stages.

· Measures to mitigate environmental impacts as well as environmental monitoring and auditing to be implemented.

2.2 Key Project Requirements

The key project requirements for the NENT Landfill Extension are:

· Development of a sanitary landfill that covers an area of about 70 ha with an estimated void space (landfill capacity) of 19Mm³;

· Provision of a liner system for the landfill to prevent contamination of land and water resources;

· Provision of a leachate collection, treatment and disposal facilities with sufficient capacity for handling the leachate arising from the landfill extension;

· Provision of landfill gas collection, utilisation and management facilities;

· Provision of utilities, drainage and road network necessary for the proper operation of the Project;

· Provision of facilities (both civil works and electrical & mechanical equipment) for waste reception, inspection, charging, handling and compaction, and plant maintenance;

· Provision of facilities for site administration;

· Operation of the landfill in compliance with all relevant engineering, geotechnical and environmental standards;

· Restoration of the landfill in compliance with all relevant engineering, geotechnical and environmental standards;

· Provision of aftercare for the landfill for a period of about 30 years;

· Carrying out environmental monitoring and audits throughout construction, operation, restoration and aftercare of the landfill; and

· Implementation of environmental measures necessary for the protection of the surrounding environment.

2.3 Need for the Project

2.3.1 Growing Wasteloads

Waste is a common problem of affluent societies. Especially when people can afford greater convenience and more purchases, they tend to generate a higher volume of waste per capita. Hong Kong is no exception to this. Like many other modern cities, Hong Kong has seen its wasteloads increase following the economic growth. Municipal wasteloads have grown on average of about 3% per year since 1986. With the population growth at 0.9% each year, the waste generation rate has risen from 1.96 kg per person per day in 1996, to 2.27 kg in 2004 (Figure 2.1).

Text Box:

MSW Generation: 3% average annual growth

Population: 0.9% average annual growth

Figure 2.1 Waste line grew from 1996 to 2004 [extracted from EPD” Policy Framework for the Management of MSW (2005-2014)”]

Hong Kong’s waste arising have exceeded the expected amount. At the time when the three existing strategic landfills, SENT Landfill, NENT Landfill and WENT Landfill, were planned, it was forecasted that the daily amount of waste to be disposed of at landfills would rise from 12,500 tonnes in 1989, to 14,000 tonnes in 1997 and 16,700 tonnes by 2001. By 1997 the three strategic landfills were already taking in 16,000 tonnes of waste every day. Should this trend continue, the landfills will be full by 2015, instead of lasting until 2020 as they were originally designed for.

Although all measures outlined in the Policy Framework for the Management of Municipal Solid Waste (2005-2014) including source separation, MSW charging, waste recycling, IWMF, etc. would help extend the lives of the three landfills, the residues from the IWMF will still require sites for final disposal and landfill site is therefore necessary.

The reality is that HK, like all other developed cities around the world, will need landfills as the final means of disposal. Assuming the Government’s target of reducing the waste going to landfill site from 60% in 2004 to 25% by 2014 will be achieved, some 4000 tonnes per day of waste still needs to be disposed of at landfill sites. Therefore, outlets for landfill sites for final disposal of solid waste are still required. Extensions of existing landfill sites have been identified as an indispensable element for the management of waste in Hong Kong. Justifications of the need for providing additional void space for waste disposal by developing extension at the existing NENT Landfill are provided in the following sections.

2.3.2 Justification of Developing Extension at NENT Landfill

With a clear Government strategy to achieve sustainable management of the MSW in the next 10 years, it is anticipated that the amount of solid waste requiring landfill disposal will start to reduce gradually. Having said that, there will still be millions of tonnes of un-recyclable or unrecoverable waste requiring disposal each year. With the three existing strategic landfills envisaged to be exhausted between Year 2011 to 2015 and the long lead time required for developing new landfills, there is a need to identify an intermediate solution.

EPD had therefore commissioned a study in February 2000 to explore the potential of extending the existing landfills and identify potential new landfill sites.

Given that it will take many years to confirm suitability of a new landfill location, extensions of the existing landfills were considered a practicable, necessary and urgent intermediate solution. Key advantages of the extension schemes include:

· Availability of existing supporting infrastructure and therefore less lead time for the development.

· Availability of existing supporting infrastructure and therefore more cost effective for the development.

· Availability of accurate information and hence lower level of risk in capital and operating costs estimation.

· Availability of existing environmental monitoring data and hence more reliable for confirming environmental acceptability of the Project.

· Availability of existing supporting infrastructure and therefore less requirements on land resumption for the development.

· Availability of existing supporting infrastructure and therefore potentially less impact on the environment in comparison with a new green field site scheme.

· Established site specific procedures for operation and environmental impact control.

These key advantages are recognised at the NENT Landfill for the proposed extension.

2.4 Consideration of Alternatives

2.4.1 Alternative Extension Layout

In working out the most desirable layout for NENT Landfill Extension, a number of layout options were formulated, evaluated and then compared for selection, based on various evaluation criteria and an evaluation framework agreed with relevant stakeholders in advance.

The key issues and constraints identified during the course of study were taken into account in formulation of landfill extension layout options. A total of 4 broad options (as well as related sub-options) were thoroughly evaluated and discussed at a Value Management Workshop on 2 December 2005, attended by relevant stakeholders. Key features of the various options are recapitulated below.

2.4.2 Broad Layout Option 1

2.4.2.1 Option 1

Option 1 adopts a similar rationale as the proposed conforming scheme in the EPD’s preliminary study under “Agreement No. CE45/99, Extension of Existing Landfills and Identification of Potential Waste Disposal Sites, Final Strategic Environmental Assessment Report”. It achieves a landfill capacity of 17Mm³, and infringes a minor part of the Tong To Shan Archaeological Site (TTSAS). The area of built heritage affected will only be limited to the secondary features of boulder paths and stone terraces. The main archaeological features will be untouched (see Drawing No. 24315/01/101 for layout). The key parametric indicators of this option are outlined below in Table 2.1.

Table 2.1: Summary of Option 1

Waste receiving area	60 ha
Maximum fill level	+245 mPD
Site formation complexity	Cut volume 5.9 Mm³, Fill volume 2.3 Mm³
Landfill capacity	17.4 Mm³

2.4.2.2 Option 1a

Option 1a is similar to Option 1 except with the slight extension to the southern boundary and the increase in fill level to meet the target landfill capacity of 19Mm³. The design is achieved by raising the eastern part of the landfill extension by approximate 10m relative to the original design to reach a maximum level of +255mPD (see Drawing No. 24315/01/102). The maximum height of the adjacent Wo Keng Shan is about +297mPD. It is envisaged that the visual impact due to a 10m raise would be insignificant. The key parametric indicators of this option are outlined in Table 2.2.

Table 2.2: Summary of Option 1a

Waste receiving area	61 ha
Maximum fill level	+255 mPD
Site formation complexity	Cut volume 6.0 Mm³, Fill volume 2.2 Mm³
Landfill capacity	20.2 Mm³

2.4.2.3 Option 1b

Option 1b is derived based on Options 1 and 1a, with the same encroachment to TTSAS, to further increase the landfill capacity. The design is achieved by the slight extension to the south boundary and the increase in fill level to +300mPD (see Drawing No. 24315/01/103). This roughly matches with the maximum elevation of +297mPD of the adjacent Wo Keng Shan. The key parametric indicators of this option are outlined in Table 2.3.

Table 2.3: Summary of Option 1b

Waste receiving area	61 ha
Maximum fill level	+300 mPD
Site formation complexity	Cut volume 6.0 Mm³, Fill volume 2.2 Mm³
Landfill capacity	25.2 Mm³

2.4.3 Broad Layout Option 2

2.4.3.1 Option 2

Option 2 avoids the encroachment on TTSAS and keeps the peak level the same as Option 1 (i.e. +245mPD). This will reduce the actual landfill capacity to 16.8Mm³ (see Drawing No. 24315/01/104). The key parametric indicators of this option are outlined in Table 2.4.

Table 2.4: Summary of Option 2

Waste receiving area	55 ha
Maximum fill level	+245 mPD
Site formation complexity	Cut volume 4.7 Mm³, Fill volume 2.0 Mm³
Landfill capacity	16.8 Mm³

2.4.3.2 Option 2a

Similar to Option 2, Option 2a also avoids the encroachment on TTSAS and again falls short of meeting the target capacity of 19Mm³. The design deviates from Option 2 by raising the eastern part of the landfill extension by approximate 10m to reach a maximum level of +255mPD (see Drawing No. 24315/01/105). The key parametric indicators of this option are outlined in Table 2.5.

Table 2.5: Summary of Option 2a

Waste receiving area	55 ha
Maximum fill level	+255 mPD
Site formation complexity	Cut volume 4.7 Mm³, Fill volume 2.0 Mm³
Landfill capacity	18.4 Mm³

2.4.4 Broad Layout Option 3

Archaeological survey conducted on the site has identified a number of large graves in the heart of the landfill extension. Option 3 is developed with extensive reinforced earth wall at the northern boundary to avoid the need for clearance of these existing large graves (Drawing No. 24315/01/106). The landfill capacity will however be reduced to only 11.1Mm³. The key parametric indicators of this option are outlined in Table 2.6.

Table 2.6: Summary of Option 3

Waste receiving area	50 ha
Maximum fill level	+245 mPD
Site formation complexity	Cut volume 3.7 Mm³, Fill volume 2.8 Mm³
Landfill capacity	11.1 Mm³

2.4.5 Broad Layout Option 4

Option 4 is developed with the northwestern and southeastern boundary extended to reach the ridgeline to maximize the landfill capacity. The northern boundary is also set back to minimize the impact to woodland as well as TTSAS (see Drawing No. 24315/01/107). The landfill capacity can achieve 21.4Mm³ while encroachment on the Lin Ma Hang catchment can be totally avoided. The key parametric indicators of this option are outlined in Table 2.7.

Table 2.7: Summary of Option 4

Waste receiving area	63 ha
Maximum fill level	+255 mPD
Site formation complexity	Cut volume 6.2 Mm³, Fill volume 2.2 Mm³
Landfill capacity	21.4 Mm³

2.4.6 Selection of Preferred Scenario

2.4.6.1 Evaluation Criteria

These options were evaluated / assessed in accordance with the following factors and main criteria :

· Waste management needs of 19Mm³void space for the NENT Landfill Extension;

· Engineering considerations including site formation complexity, constructability, drainage impact and maintenance;

· Environmental issues such as noise, air quality, ecology, landscape and visual, waste management, cultural heritage, water quality, etc.

· Social issues such as afteruse flexibility, cost of disposal, land resumption and graves clearance.

2.4.6.2 Waste Management Needs

Under the previous study ”Agreement No. CE45/99, Extension of Existing Landfills and Identification of Potential Waste Disposal Sites, Final Strategic Environmental Assessment Report”, the “Strategic Plan” for the development of NENT Landfill Extension required a void space (landfill capacity) of 19Mm³ to be provided. Options 1, 2, 2a and 3 cannot achieve this target volume. Options 1a, 1b and 4 can achieve this target and are therefore preferred.

2.4.6.3 Engineering Considerations

The major engineering considerations relate to construction practicability, drainage impact to downstream rivers and requirements on operation and maintenance of the various facilities are discussed as follows:

Construction Practicability

The optimum engineering design of a landfill site is to maintain a balance in cut and fill material over the entire construction and operation periods. Importing or exporting construction material is not preferred. In this regard, all the four broad options including sub-options can achieve this requirement.

According to the recent ground investigation (GI) data, there is no particular geological constraint in the proposed landfill extension site. Site formation and retaining structures for all options are feasible to construct. All options will experience the same founding condition and reinforced fill slopes will be adopted for retaining structures taller than 10m.

Although Options 1, 1a, 1b, 2, 2a and 4 require the construction of reinforced earth wall, they do not affect the site formation planning and are therefore preferred. By contrast, Option 3 requires construction of a long reinforced earth wall at the north within a small site area, hence imposing great difficulties on the phasing and sequencing of the site formation works. Option 3 is therefore less preferable.

Drainage Impact to Downstream

All options affect the existing landform and may have impact to the adjacent drainage systems at both Lin Ma Hang Stream and Ping Yuen River.

According to the Drainage Impact Assessment (DIA) conducted for this Project, the diversion of catchment in some options will result in increased water level in Ping Yuen River and decreased water level in Lin Ma Hang Stream. In other words, the less the impact on stream and river, the more preferable the option.

Options 2, 2a, Option 3 and Option 4 that have no drainage impact to Lin Ma Hang Stream are therefore preferred. Option 1, 1a and 1b have drainage impact to both Lin Ma Hang Stream and Ping Yuen River and are therefore less preferable.

Operation and Maintenance

The operation and maintenance requirements for various facilities such as treatment facilities, drainage system, E&M equipment, water quality, leachate and landfill gas monitoring equipment, etc. are similar for all the 4 options.

Option 1, 1a and 1b are preferred as they have only a small section of reinforced earth wall, which requires less maintenance works. Options 2, 2a, 3 and 4 require more substantial maintenance works for the reinforced earth wall and the associated drainage system, and are therefore less preferable.

2.4.6.4 Environmental Issues

The major environmental considerations relate to water quality, ecology, archaeology and cultural heritage, landscape and visual etc. at various project phases are discussed as follows:

Water Quality Impact

Some of the landfill extension options may encroach to both Lin Ma Hang and Ping Yuen Catchments. There may be certain degree of influence of water flow/yield on Lin Ma Hang Stream and Ping Yuen River. In case of any accidental overflow from the treatment plant or accidental leakage through the liner, there might be short-term impact on the adjacent streams.

Options 2, 2a, 3 and 4 with no encroachment to Lin Ma Hang Catchment are therefore preferred whereas, Option 1, 1a and 1b with encroachment to both Lin Ma Hang Catchment and Ping Yuen Catchment are less preferable.

Ecological Impact

Some of the landfill extension options may cause minor ecological impacts to the Lin Ma Hang Stream due to reduction in water level and loss of woodland and shrubland. Option 1, 1a and 1b will cause minor ecological impacts to Lin Ma Hang Stream due to a 15mm drop in water level and are therefore less preferable. Options 2, 2a, 3 and 4 will have neither encroachment nor ecological impacts on Lin Ma Hang Stream, and are preferred options.

Woodland of over 1 ha is considered as an important habitat. Option 1, 1a and 1b will cause a significant loss of woodland of more than 5ha and are thus less preferable. For other options, the impact on loss of woodland, ranging from 2 to 4 ha, are considered to be moderate in term of ecological value. Compensatory woodland planting would be provided. These options are therefore preferred with mitigation measures being in place.

With consideration of a cumulative combination of ecological impacts (drop in water level and loss in woodland), Options 1, 1a, 1b and 4 are less preferable. Options 2, 2a and 3 are preferred.

Archaeological and heritage Impact

Some of the landfill extension options may encroach into TTSAS affecting secondary features such as boulder paths and boulder terraces. A total of 21 graves including 10 old graves will be affected and will need to be removed. In terms of impacts to graves, all options have the same grade as these can be mitigated by detailed preservation by record as agreed with AMO, LCSD.

Option 1, 1a and 1b will encroach into TTSAS by about 5 ha, affecting of 200m boulder paths and 2 numbers of boulder terraces. Nonetheless, these affected areas comprise mainly secondary features and can be mitigated by detailed preservation by record (as agreed with AMO). Therefore, these options are less preferable.

Options 2, 2a and 3 will have no impact to the TTSAS and are therefore preferred. Similarly, Option 4 affects only 30m of boulder path (secondary feature only) which can be mitigated by detailed preservation by record. The impact on Option 4 is therefore also minimal and this option is preferred.

Landscape and Visual Impact

Option 1a will have a total area of about 61 ha which encroaches into about 5.16 ha of woodland near the ridge of Wong Mau Hang Shan, Shui Ngau Tso and northeast of Wo Keng Shan. The final height of the landfill is about +255mPD.

Option 2a will have a total area of about 54 ha which encroaches into about 3.08 ha woodland near the ridge of Shui Ngau Tso and northeast of Wo Keng Shan. The final height of the landfill is about +255mPD.

Option 3 will have a total area of about 50 ha which encroaches into about 3.05 ha of woodland near Shui Ngau Tso and northeast of Wo Keng Shan. The final height of the landfill is about +245mPD which is similar to the adjacent Wong Mau Hang Shan.

Option 4 will have a total area of about 63 ha and encroach into about 3.7ha of woodland near the ridge of Shui Ngau Tso and northeast of Wo Keng Shan.

In fact, the visual impact to the adjacent areas for all options is similar with slight impact (also see Chapter 8).

Other environmental considerations

Other environmental considerations, including air, noise, waste, landfill gas, have been reviewed. The potential impacts for all options are similar in order and can all be mitigated by suitable mitigation measures.

2.4.6.5 Impact on Community

The major community considerations relate to flexibility for aftercare, unit cost per disposal, needs for land resumption and needs for graves clearance at various project phases are discussed as follows:

Flexibility for Afteruse

The proposed extension is expected to last for about 10 to 12 years. Options that can offer higher flexibility to the potential afteruse of the landfill are preferred.

Options 1, 1a, 1b and 4 will cover areas of 60 ha to 63ha in size. The gradients of the final landfill profile for these options are gentle and suitable for all type of afteruse activities. These options would not impose any restriction/limitation to the afteruse planning. They are the preferred options.

Option 2 and 2a will cover an area of 55 ha only. The gradient of the final landfill profile is gentle with slight variation. This option would not impose any restriction/limitation to the afteruse planning. However, this option has less planning flexibility in view of the smaller landfill area and is therefore less preferable.

Similarly, Option 3 has the smallest landfill area of only 50 ha with steep gradient at certain locations. The steep slope may inevitably impose additional constraints to the potential afteruse and the planning flexibility of other facilities such as bowling greens and multi-purposes grass pitches. This option is therefore also less preferable.

Unit Cost per Disposal

The unit cost per disposal is the capital cost divided by the actual landfill capacity, which is the cost required to produce a 1m³ landfill capacity. The higher the unit cost per disposal, the higher the chance of illegal dumping.

The anticipated unit cost per disposal (m³) for Options 1, 1a, 1b, 2, 2a and 4 are of similar order, which is about half of that for Option 3. Based on the above cost estimation, Options 1, 1a, 1b, 2, 2a and 4 are “preferred”; while Option 3 is “less preferable”.

Needs for Land Resumption

All Options will affect the same number of private lots. Nonetheless, Option 1, 1a and 1b affect a Government Hilltop Survey Tri-Station (GLA) and are therefore less preferable. Hence, Options 2, 2a, 3 and 4 are preferred.

Needs for Graves Clearance

According to recent survey, there are a large number of graves including some old graves lying within the extension site. All options affect almost the same number of graves including old graves except for Option 3 which affect a much smaller number of graves (9 to 10 graves less). Option 3 is therefore preferred. All other options are less preferable since a longer lead time would be required on liaison in the graves clearance process.

2.4.6.6 Overall

Amongst the three options in Broad Layout Option 1, Option 1a is the most preferred. Similarly, Option 2a is the most preferred option under Broad Layout Option 2. Accordingly, Option 1a and Option 2a were therefore directly compared with Option 3 and Option 4, so as to arrive at the most favourable layout for NENT Landfill Extension. A summary of the final round of layout options selection is tabulated below.

Table 2.8: Summary of reasons for option evaluation

Criteria

Option 1a

Option 2a

Option 3

Option 4

(A) Waste Management Needs

20.2 Mm³ - achieving the target requirement of 19Mm³ .

(Preferred)

18.4 Mm³ - marginally falls short of meeting target requirement of 19Mm³ .

(Less Preferred)

11.1 Mm³ - falls short of meeting target requirement of 19Mm³ .

(Less Preferred)

21.4 Mm³ - achieving the target requirement of 19Mm³ .

(Preferred)

(B) Engineering

Construction Practicability

No imported fill material is required for the site formation works;

Require short (100m) reinforced earth wall with max. height of 15m.

(Preferred)

No imported fill material is required for the site formation works;

Require relatively long (400m) reinforced earth wall with max. height of 25m.

(Preferred)

No imported fill material is required for the site formation works;

Require relatively long reinforced earth wall (with max. height of 25m) in a relatively small site and impose difficulties in site formation phasing.

(Less Preferred)

No imported fill material is required for the site formation works;

Require relatively long reinforced earth wall (with max. height of 25m) but will not impose difficulties in site formation phasing.

(Preferred)

Drainage Impact to Downstream

Impact to both Lin Ma Hang Stream and Ping Yuen River.

(Less Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang).

(Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang).

(Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang).

(Preferred)

Operation and Maintenance

Require maintenance of a short reinforced earth wall and associated drainage system (100m).

(Preferred)

Require maintenance of a relatively long reinforced earth wall and associated drainage system (400m).

(Less Preferred)

Require maintenance of a relatively long reinforced earth wall and associated drainage system (510m).

(Less Preferred)

Require maintenance of a relatively long reinforced earth wall and associated drainage system (590m).

(Less Preferred)

(C) Environmental

Water Quality Impact

Impact to both Lin Ma Hang Stream and Ping Yuen River

(Less Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang)

(Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang)

(Preferred)

Impact to Ping Yuen River (no impact on Lin Ma Hang)

(Preferred)

Ecology Impacts

Minor impact to the Lin Ma Hang Stream & its catchment;

Relatively large scale of woodland loss (5.16ha);

No impact to Lin Ma Hang Lead Mines;

Minor impact to the Robin’s Nest countryside;

(Less Preferred)

No impact to the Lin Ma Hang Stream & its catchment;

Small scale of woodland loss (3.08ha)

No impact to Lin Ma Hang Lead Mines;

Minor impact to the Robin’s Nest countryside;

(Preferred)

No impact to the Lin Ma Hang Stream & its catchment;

Small scale of woodland loss (3.05ha)

No impact to Lin Ma Hang Lead Mines;

Minor impact to the Robin’s Nest countryside;

(Preferred)

No impact to the Lin Ma Hang Stream & its catchment;

Medium scale of woodland loss (4.01ha)

No impact to Lin Ma Hang Lead Mines;

Minor impact to the Robin’s Nest countryside;

(Less Preferred)

Archaeological and Heritage Impact

Encroach into small (non-core) portion of TTSAS (5ha).

Affect 21 graves including 10 old graves (no impact on cultural heritage value).

(Less Preferred)

No impact to TTSAS.

Affect 20 graves including 9 old graves (no impact on cultural heritage value).

(Preferred)

No impact to TTSAS.

Affect only 9 graves and avoid all old graves (no impact on cultural heritage value).

(Preferred)

Encroach into very small (non-core) portion of TTSAS (2ha).

Affect 20 graves including 9 old graves (no impact on cultural heritage value).

(Preferred)

Landscape & Visual

Total landfill area is 61ha; final fill level at +255mPD.

(Insignificant landscape & visual impact)

Total landfill area is 55ha; final fill level at +255mPD.

(Insignificant landscape & visual impact)

Total landfill area is 50ha; final fill level at +245mPD.

(Insignificant landscape & visual impact)

Total landfill area is 63ha; final fill level at +255mPD.

(Insignificant landscape & visual impact)

Other Environmental Considerations, such as air, noise, landfill gas, waste

Neutral to various options – minor impact which can be mitigated by suitable mitigation measures.

(similar impact to other options)

Neutral to various options – minor impact which can be mitigated by suitable mitigation measures.

(similar impact to other options)

Neutral to various options – minor impact which can be mitigated by suitable mitigation measures.

(similar impact to other options)

Neutral to various options – minor impact which can be mitigated by suitable mitigation measures.

(similar impact to other options)

(D) Impact on Community

Flexibility for afteruse

Largest landfill area (61ha) with gentle slopes/ gradient – good for all kinds of afteruse.

(Preferred)

Smaller landfill area (55ha) with gentle slopes/gradient, but vary in landfill profile and hence less planning flexibility.

(Less Preferred)

Smallest landfill area (50ha) with steep slope and extensive earth wall. Hence, impose constraints to the potential afteruses.

(Less Preferred)

Highest landfill area (63ha) with gentle slopes/ gradient – good for all kinds of afteruse.

(Preferred)

Unit Cost per Disposal

Comparable with other options except Option 3.

(Preferred)

Comparable with other options except Option 3.

(Preferred)

Higher disposal cost leading to higher chance of illegal dumping.

(Less Preferred)

Comparable with other options except Option 3.

(Preferred)

Need for Land Resumption

Affect private lands and survey station

(Less Preferred)

Affect only private lands (no impact on survey station)

(Preferred)

Affect only private lands (no impact on survey station)

(Preferred)

Affect only private lands (no impact on survey station)

(Preferred)

Need for Graves Clearance

Affect 21 graves including 10 old graves (no impact on cultural heritage value)

(Less Preferred)

Affect 20 graves including 9 old graves (no impact on cultural heritage value)

(Less Preferred)

Affect 9 graves and aovid all old graves (no impact on cultural heritage value)

(Preferred)

Affect 20 graves including 9 old graves (no impact on cultural heritage value)

(Less Preferred)

As Option 4 was evaluated as a preferred option for the largest number of aspects, it was selected as the overall most preferred option. See Drawing No. 24315/01/107 for the layout of Option 4.

2.4.7 Alternative Construction Methods and Sequences of Works

Different construction methodology and sequences of works were studied, giving careful consideration on environmental impacts including noise, ecology, archaeology, etc.

It is recommended to adopt a balanced cut-and-fill site formation for constructing the landfill bowl within the existing valley.

The NENT Landfill Extension will be developed in three phases to allow progressive use of the overall landfill area. Each phase will be constructed, operated and restored at a rate dependent on the delivery of waste. Simultaneous construction, operation and capping activities will therefore occur in different parts of the site.

During the construction stage, mobilisation & preparation / establishment will be carried out by the DBO Contractor. A balance between cut-and-fill quantities will be adopted to optimise the reuse of excavated materials, i.e. to minimise import or export of materials. The process involves temporarily stockpiling of excavated materials on site for use as daily cover during the operation phase and final capping during the restoration phase. This will reduce construction materials / waste to be delivered to public fill bank. Where necessary (to be triggered by EM&A programme), daily cover and temporary cover will be provided to reduce potential impact on air and water qualities during the operation phase of the Project.

Alternative construction methods such as blasting have also been evaluated but found to be not desirable from an engineering perspective. The balancing of cut-and-fill limits the usable area of the landfill site and therefore the amount of stockpiled materials. Blasting will generate a significantly larger volume of excavated and stockpiled materials, and the usable area of the landfill site will be much reduced. There is also a safety concern if blasting is conducted in close proximity to the tipping area, as refuse collection vehicles and operators might be at risk if the buffer distance provided is not sufficient.

2.5 Site Location and Site History

2.5.1 Site Location

The landfill extension site of the selected layout is approximately 70 ha in size and located in a valley to the south of the existing NENT Landfill. The valley is encircled by three ridgelines and exits to the southwest through a small gorge, at approximately +50mPD.

On its south-eastern side, the site is enclosed by a major ridgeline, which runs from Wo Keng Shan (+297mPD) to Robins Nest (+492mPD). A smaller ridge intersects this main ridgeline and forms the northern flank of the Project area. This ridge overlooks To Tong Shan Settlement District and Lin Ma Hang Village. It reaches an elevation of +205mPD at its western end, just beyond the boundary between the existing NENT Landfill and the extension site. Two saddles, with minimum elevations of approximately +120mPD, are located about half way along this smaller ridge.

The ridge separating the site from the existing NENT Landfill forms the north-western boundary of the Project area. This ridge runs from an elevation of +205mPD at its northern end to a level of +65mPD at the point where it intersects the existing haul road in the south-western corner of the site (Drawing No. 24315/01/001).

The slopes overlooking the main valley of the site are sparsely vegetated with a cover of grass and shrubland. Occasional groups of pine trees and localised dense vegetation are also found along stream courses.

2.5.2 Site History

The proposed extension is mainly covered by the existing NENT Landfill Stockpile and Borrow Area that was formed to the east of the existing landfill as part of the original landfill development. The aerial photographs of the site reveals that several large cut slopes, many of which have been subsequently covered with stockpiled material, and a haul road (Shek Tsai Ha Road) have been formed within. The stockpile area is mostly located within the eastern portion of the site and is bound by concrete drainage channels. Other than the haul road and scattered gravesites, the remaining site area comprises natural terrain that has seen little interference from human activity.

2.6 Nature, Scope and Benefits of the Project

2.6.1 Nature of the Project

The nature of the Project is to develop a landfill extension for waste as defined in the Waste Disposal Ordinance (Cap. 354).

2.6.2 Scope of the Project

The scope of the Project is to provide a landfill extension of about 70 hectares with a target void space of at least 19 million cubic metres on the eastern side of the existing NENT Landfill. On top of site formation and preparation works; there will be provision of installation of liner system; leachate collection, treatment and disposal; gas collection and management; utilities provisions; drainage diversion; restoration and aftercare. Environmental mitigation measures, monitoring and auditing are provided.

2.6.3 Benefits of the Project

The development of NENT Landfill Extension ensures the continued provision of final disposal site for solid waste after the three existing landfills are full by 2015.

It also avoids illegal dumping of construction waste and municipal waste that may cause serious environmental problems.

With waste-to-energy facility (such as Landfill Gas Export Scheme), landfill gas can be converted to reusable energy that brings benefits to the community.

The Project site is equipped with waste handling facilities at NENT Landfill, waste recycling factories in the nearby area, sewage treatment facility at Shek Wu Hui Sewage Treatment Works, and a landfill gas waste-to-energy facility nearby. The availability of these existing supporting facilities can shorten the lead time and land resumption requirement for a new landfill development in a green field site.

Substantial saving in cost can also be achieved by pooling together the existing NENT Landfill infrastructure and facilities by carrying out suitable conversion works under suitable contractual arrangement.

There are some small-scale waste recycling factories around the existing NENT Landfill, skilful workers and special equipments have been allocated in the region. Therefore, there will be social and economic benefit of the Project, if these workers and equipments can be tied in with the NENT Landfill Extension (e.g. sustainable for local employment).

2.7 Size, Scale, Shape and Design of the Project

The landfill extension site is a bowl-shape area with a large void space in the middle for waste filling. The northwestern and southeastern boundaries of the landfill extension site follow the ridgelines to maximize the landfill capacity. Some set back of the northern boundary is included to minimize the impact to woodland and Lin Ma Hang Catchment. The total site area is about 70 ha and the final height of the landfill would be +255mPD (see Drawing No. 24315/01/107).

The key design features are listed as follows and summarised in Table 2.10:

· Bottom liner system - to separate rubbish and leachate from groundwater;

· Landfill cells – to store waste within the unit;

· Storm water drainage system - to collect rain water run off on the landfill;

· Leachate collection system - to collect liquid leaching from the waste mass and convey it to a leachate treatment plant prior to discharging to Shek Wu Hui Sewage Treatment Works;

· Gas collection system - to collect gases formed during the decompositon of waste. These gases will be treated and utilised for production of electricity on site.

· Covering and capping - to seal off the top of the landfill with a gas venting layer, an impermeable mineral layer, a drainage layer of at least 0.5 metre and at least one metre of top soil.

Table 2.10: Summary of key design elements

Total size	63 ha
Final height	+255 mPD
Shape	Bowl shape at the existing NENT Landfill Stockpile and Borrow Area
Site formation complexity	Cut volume 6.2 Mm³, Fill volume 2.2 Mm³
Actual waste capacity	21.4 Mm³
Key elements of design	• Site formation and preparation • Installation of liner system • Installation of leachate collection, treatment and disposal facilities • Installation of gas collection, utilization and management facilities • Utilities provisions and drainage diversion

Various activities during construction, operation, restoration and aftercare of landfill are discussed in the following sub-sections.

2.7.1 Construction Phase and Activities

Simple excavation and slope formation works will be carried out during the construction stage. The permanent works comprise cut and fill earthworks, slope formation and earth wall construction. The temporary works will involve the formation of temporary ditches along the sides of the excavations and associated drainage works, and material storage areas.

During site formation, sediment will be contained in permanent detention ponds/silt traps that will be constructed according to landfill phasing. Final design and location of sediment traps are yet to be decided, but are likely to be down gradient of each landfill phase or in the downstream valleys near the existing waste reception area. Where possible they will be maintained during the operation of each phase to ensure the effective control of operational soil erosion problem.

2.7.2 Operation Phase and Activities

During operation, waste will be disposed of at individual landfill cells. Deposited waste will be compacted to thin layers. The works will be maintained at a gradient of not greater than 1 in 3 to ensure the effectiveness of the compaction equipment. Daily cover (about 150mm if soil cover used) will be applied to control environmental nuisances such as windblown litter, odour, vermin, flies and birds.

There are other more effective alternative biodegradable materials for use as daily cover. They include:

· heavy duty reusable and biodegradable sheets;

· non reusable plastic films;

· geotextiles; and

· foams and sprays.

Advantages of using alternative daily cover over traditional methods include preservation of landfill capacity and soil material; biodegradable and less permeable to water and gas (reduce water infiltration, odour and dust emission).

2.7.3 Restoration Phase and Activities

Restoration is a process to restore a landfill site to a condition suitable for afteruse.

After completion of waste filling, final capping will be applied to minimise infiltration of rainwater into the waste body thus reducing the amount of leachate generated. The capping system normally includes a number of components including topsoil, subsoil, drainage layer and barrier layer.

2.7.4 Aftercare Phase and Activities

Aftercare is the work done after the replacement of the soil and includes cultivations, fertilisation, planting, construction of pathways, access points, vegetation maintenance and monitoring.

Landscaped berms will be created and tree planting will be provided during the aftercare period for aesthetic purpose.

2.8 Project Timetable

The Landfill Extension will start receiving waste only when the existing NENT Landfill has ceased operation. The timing of this has yet to be determined as it depends on the rate of waste deliveries in the forthcoming period. Based on current prediction, the Existing Landfill will probably run out by early-to-mid next decade, by which time the Landfill Extension shall start operation.

Taking account of the time needed for mobilization and preparatory works prior to commencement of receipt of waste, it may be necessary to award the Landfill Extension contract towards the end of this decade, in order to ensure that new landfill space will be available before the capacity of the existing landfill runs out.

It is anticipated that the DBO (Design-Build-Operate) contract form, which has hitherto worked well for the existing waste management contracts (notably the three strategic landfill contracts and the refuse transfer station contracts), will be adopted for NENT Landfill Extension. Detailed design and formulation of technical details for the construction, operation, restoration and aftercare of the NENT Landfill Extension will be carried out by the DBO Contractor, in accordance with requirements stipulated in the Specification and other documents of the DBO Contract.

Even though there will not be any overlapping in operation between the Landfill Extension and the Existing Landfill, the two contracts will still overlap. Clearly the initial development (notably the initial site formation) for the NENT Landfill Extension will overlap and hence interface with the final operational period of the Existing NENT Landfill as well as part of its restoration & aftercare, whereas the early operation period of the NENT Landfill Extension plus continuation of its development works will overlap/interface with the remaining restoration of the Existing Landfill and the main part of its aftercare.

A tentative outline programme for implementation of the NENT Landfill Extension is shown in Appendix 2.2. As pointed out above, the exact timing of the various activities may vary, depending on actual volume of waste to be delivered in the forthcoming years.

2.9 Related Projects

The existing NENT Landfill would be the only related project for the purpose of this study.

2.10 “No Project” Scenario

The current site mainly located within the borrow area of the existing NENT Landfill. Based on the site inspection, some of the nearby areas are used for waste recycling activities. Under the “no project” scenario, the site will be operated as a restored landfill for 30 aftercare period. During this period, raw leachate will still be generated and collected to the open lagoons. Landfill gas will also generate during this period. Part of the LFG will be extracted for leachate treatment in the Ammonia Stripping Plant. Restoration planting will be carried out in phase after the final capping. Maintenance vehicle will be visiting the site for periodic inspection and maintenance. Subject to the detailed design for restoration, the area might be used for recreational use in the medium-term future after the soil is settled and stabilised.

3 Air Quality Impact

3.1 Introduction

This chapter presents the impact assessment on potential air quality aspects for the construction, operation and restoration and aftercare stages of the Project. Control measures for construction related activities have been recommended, in accordance with the requirements specified in the Air Pollution Control (Construction Dust) Regulation. Proper emission control limits for stack emissions from ammonia stripping plant, flare and landfill gas (LFG) power generator will be in place for the extension site, similar to the current NENT Landfill operation. Together with the implementation of good site practice for the tipping operation, the air quality impact will be controlled to within Hong Kong Air Quality Objectives (HKAQOs).

The assessment has been conducted in accordance with the requirements of Annex 4 and Annex 12 of the TM-EIAO, as well as the requirements set out under Clause 3.4.1 of the EIA Study Brief.

3.2 Environmental Legislation, Standards and Guideline

The relevant legislation and associated guidance notes applicable to the study for the assessment of air quality implications include:

· Environmental Impact Assessment Ordinance (Cap. 499) and Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO);

· Air Pollution Control Ordinance (APCO) (Cap. 311) Air Pollution Control (Construction Dust) Regulation (Cap. 311R);

· Hong Kong Planning Standards and Guidelines (HKPSG);

· World Health Organisation (WHO); and

· United State Environmental Protection Agency (USEPA) references.

3.2.1 Air Quality Objectives

The principal legislation for controlling air pollutants is the Air Pollution Control Ordinance (Cap. 311) and its subsidiary regulations, which define statutory Air Quality Objectives (AQOs) for 7 common air pollutants. The AQOs for these air pollutants are tabulated in Table 3.1 below.

Table 3.1 : Hong Kong Air Quality Objectives

Pollutant	Concentration in micrograms per cubic metre ^[1] (Parts per million, ppm in brackets)
Pollutant	1 Hour ^[2]	8 Hour ^(3]	24 Hours ^[3]	3 Months ^[4]	1 Year ^[4]
Sulphur Dioxide	800 (0.3)		350 (0.13)		80 (0.03)
Total Suspended Particulates (TSP)	500 ^[7]		260		80
Respirable Suspended Particulates (RSP) ^[5]			180		55
Carbon Monoxide	30,000 (26.2)	10,000 (8.7)
Nitrogen Dioxide	300 (0.16)		150 (0.08)		80 (0.04)
Photochemical Oxidants (as ozone) ^[6]	240
Lead				1.5

Notes:

[1] Measured at 298°K and 101.325 kPa.

[2] Not to be exceeded more than three times per year.

[3] Not to be exceeded more than once per year.

[4] Arithmetic mean.

[5] Respirable suspended particulates means suspended particulates in air with a nominal aerodynamic diameter of 10 micrometres or smaller.

[6] Photochemical oxidants are determined by measurement of ozone only.

[7] Not an AQO. TM-EIAO suggested short-term averaging level for 1 hour is 500ug/m³. There is no exceedance allowance for 1-hour TSP guideline level.

3.2.2 Air Pollution Control (Construction Dust) Regulation

The Air Pollution Control (Construction Dust) Regulation identifies those processes that require special dust control. The Contractor of this Landfill Extension is required to inform the EPD prior to carrying out such processes and to adopt dust reduction measures while carrying out "Notifiable Works" or “Regulatory Works”, as defined under the regulation. Works relevant to this Project are the site formation activities, for which TSP concentration shall not exceed 500 ug/m³.

3.2.3 Odour Criteria

In accordance with Annex 4 of TM-EIAO, the limit of 5 odour units (OU) based on an averaging time of 5 seconds for odour prediction assessment shall not be exceeded at any receivers.

3.2.4 Other Pollutants

Other pollutants that are not covered by the Hong Kong AQOs but may impose a health risk concern have also been considered. The criteria / guideline values related to carcinogenic and non-carcinogenic health risk evaluation are established from the following order of reference:

· World Health Organization (WHO);

· United States Environmental Protection Agency (USEPA); and

· California Environmental Protection Agency (CEPA).

The guidelines for the assessment of carcinogenic health risk from exposure to air toxics are based on the WHO and USEPA Integrated Risk Information System (IRIS)’s acceptable lifetime risk.

Long-term monitoring for 38 species of VOC relating to the landfilling operation is being conducted by NENT Landfill. Nonetheless, emission for 18 species of these VOC is found to be insignificant and below the detection limit. Out of the remaining 20 species of VOC, only 8 species have documentary concern related to carcinogenic and non-carcinogenic health risk. The unit risk factor and reference dosage for the 8 related VOCs are tabulated in Table 3.2.

Table 3.2: Unit factors and reference dosage from available WHO/IRIS/CEPA database on related VOCs

Substance ^[1]	Molecular Weight g/mol ^[4]	Unit Factor per μg/m³ ^[3]	Reference dosage ^{[2,4,5,6, 7]}
Benzene (CASRN 71-43-2)	78.11	6x10^-6	Chronic Inhalation Exposure (RfC): 30 μg/m³ (9.4ppbv) (IRIS) Acute: 1.3 x 10³ μg/m³(406.9ppbv) (CEPA)
1,4-Dichlorobenzene (CASRN 106-46-7)	147.01	-	Chronic Inhalation Exposure (RfC): 8x10² μg/m³(133.1ppbv) (IRIS)
Ethyl Benzene (CASRN 100-41-4)	106.16		Chronic: 22,000 μg/m³for 1 year averaged All based on WHO (Geneva) Chronic Inhalation Exposure (RfC): 1000 μg/m³ (230.3ppbv) (IRIS)
Toluene (CASRN 108-88-3)	92.14	-	Acute: 1 x 10³ μg/m³for 30min averaged(odour threshold) (265.4ppbv), based on S5.14 of WHO Chronic: 260 μg/m³(69ppbv) of 1 week, based on S5.14 of WHO
Vinyl chloride (CASRN 75-01-4)	62.5	1.0x10^-6	Chronic Inhalation Exposure (RfC): 100 μg/m³ (IRIS) Acute: 1.8x10⁵ μg/m³ (70,416ppbv) (CEPA)
Xylenes (CASRN 1330-20-7)	106.16	-	Acute: 4800 μg/m³for 24 hour averaged Chronic: 870 μg/m³for 1 year averaged All based on WHO (Geneva) Chronic Inhalation Exposure (RfC): 100 μg/m³ (23.0ppbv) (IRIS)
Tetrachloroethylene (CASRN 127-18-4)	165.8	-	Acute: 8000 μg/m³for 30 min averaged; 250 μg/m³for 24 hour averaged based on WHO (Geneva)
Methylene Chloride / Dichloromethane (CASRN 75-09-2)	84.93	-	Acute: 3mg/m³ for 24 hour guideline; Chronic: 0.45mg/m³ for a weekly guideline All based on S5.7 of WHO

Note: [1]. CASRN – Chemical Abstracts Service Registry Number

[2]. RfC – Reference Concentration

[3]. If WHO standard is available, it will be applied first

[4]. C _ppbv = C _ug/m3 x 24.45 / Molecular Weight

[5]. WHO represents Air Qualiy Guideline for Europe, WHO

[6]. WHO (Geneva) represents Guidelines for Air Quality, WHO, Geneva, 2000

[7]. CEPA represents California Environmental Protection Agency

3.2.4.1 Carcinogenic Health Risk Assessment

Emissions pertinent to this Project are benzene and vinyl chloride which are key control parameters from the Ammonia Stripping Plant (ASP), flares and LFG generators. Tables 3.3 and 3.4 show the unit risk factors for non-criteria key pollutants of benzene and vinyl chloride and guidelines for assessment of individual risk.

Table 3.3: Unit risk factors guideline for non-criteria pollutants

Pollutant	Unit Risk ((μgm^-3 ) ^-1 )
Benzene	6x10^-6
Vinyl Chloride	1.0x10^-6

Table 3.4: Risk guidelines for carcinogenic health risk assessment

Acceptability of Cancer Risk	Estimated Individual Cancer Risk Level
Acceptability of Cancer Risk	Individual Lifetime Risk (A)	Individual Risk Per Year (B) = (A)/70
Significant	>10^-4	>1.4x10^-6
Risk should be reduced to As Low As Reasonably Practicable (ALARP)	>10^-6 & <= 10^-4	>1.4x10^-8 & <= 1.4x10^-6
Insignificant	£10^-6	£1.4x10^-8

3.2.4.2 Non-Carcinogenic Health Risk Assessment

Non-carcinogenic health risk guidelines apply to the assessment of chronic and acute health risks.

Chronic Health Risks

Using the chronic health risk assessment approach, the chronic reference concentrations for benzene and vinyl chloride are summarized in Table 3.5 and their acceptability criteria in Table 3.6.

Table 3.5: Chronic reference concentrations for benzene and vinyl chloride

Pollutant

Chronic Reference Concentration (AC_A )

(Annual Average)

Benzene

30 μg/m³ (9.4ppbv) ^(a)

Vinyl Chloride

100 μg/m³ (39.12ppbv) ^(a)

Note: ^(a)Yr 2000 updated standard from Integrated Risk Information System (IRIS), USEPA

Table 3.6: Acceptability criteria for chronic non-cancer health risks

Acceptability	Assessment Results ^(a)
Chronic non-cancer risks are considered “Insignificant”	AC_A £RC_C
Chronic non-cancer health risks are considered ‘Significant”. Detailed assessment of the control requirements and further mitigation measures are needed	AC_A >RC_C

Note: ^(a) AC_A and RC_C represent annual average concentration and chronic reference concentration respectively.

Acute Health Risks

Using the acute health risk assessment approach, the acute reference concentrations for benzene and vinyl chloride are summarized in Table 3.7 and their acceptability criteria in Table 3.8.

Table 3.7: Acute reference concentrations

Pollutant

Acute Reference Concentration (AC_HM)

(1-hour average, μg m^-3 )

Benzene

1.3 x 10^{3 (a)}

Vinyl Chloride

1.8x10⁵ ^(a)

Note : ^(a) California Air Resources Board – Air Toxic Hot Spots Program Risk Assessment Guidelines, Part I – Technical Support Document for the Determination of Acute Reference Exposure Levels for Airborne Toxicants, May 2000.

Table 3.8: Acceptability criteria for acute non-cancer health risks

Acceptability	Assessment Results ^(a)
Acute non-cancer risks are considered “Insignificant”.	AC_HM £RC_A
Acute non-caner health risks are considered “Significant”. Detailed assessment of the control requirements, and further mitigation measures are needed.	AC_HM >RC_A

Note: ^(a) AC_HM and RC_A represent maximum hourly average concentration and acute reference concentration respectively.

3.3 Description of the Existing NENT Landfill and the Extension

3.3.1 Existing vehicles trips generated from NENT Landfill

Based on the latest information, daily vehicular trip generation is in the order of 500 veh/day (or max peak hourly flow of 90 veh/hr) travelling to and from the existing NENT Landfill. Owing to the low traffic flow, vehicular emission impact is not a key issue for the existing NENT Landfill operation.

In addition, most of the refuse collection vehicles (RCV) for MSW and sludge are of enclosed-type and odorous gases are well contained during transit under normal circumstances. For sludge vehicles / special vehicles that required admission ticket, special condition can be imposed on the cleanliness of vehicle and disposal period to avoid adverse cumulative impact. With reference to the existing NENT Landfill experience, potential odour impact from RCVs can be adequately controlled and unlikely to be an issue.

3.3.2 Existing plants operation

Current NENT Landfill operation emits gaseous emissions from Ammonia Stripping Plant (ASP), flare system and landfill engine. The flare system operates only when the ASP is not in use or when excessive LFG is pending for treatment. With the development of Landfill Gas Export Scheme (LFGES), the need for flaring over any extensive period would be unlikely in practice. Monthly monitoring at the inlet and outlet of the flaring system is conducted to verify the destruction efficiency. Past monitoring results suggest that emission from flaring system has complied with the control limits.

3.3.3 Existing monitoring and audit findings

EM&A records for TSP and VOCs monitoring over the previous 9 years have been reviewed. TSP monitoring is conducted once every 6 days in three locations (See Drawing 24315/13/504 for existing dust monitoring locations D1 to D3). Whereas, VOC monitoring is conducted once every 3 months in four locations around the site boundary (See Drawing 24315/13/504 for existing VOC monitoring locations V1 to V4), and one location at source within the gas well (See Drawing 24315/13/504 for existing gas wells locations W1 to W30).

The sampling methodology was stipulated in Section 35.10.2 of the NENT Landfill Monitoring Plan. Equipment specified in Method T014/T015 of USEPA and corresponding methods for the determination of Toxic Organic Compounds in ambient air were adopted for monitoring the existing landfill. VOC will be collected in 6L stainless steel canisters coated internally with silica. Methane will be trapped using a low-flow rate pump to a 1L Tedlar bag for direct analysis on a gas chromatography. Analysis will be carried out by a laboratory equipped with a capillary gas chromatography linked to a mass spectrometer.

Key observations from the past monitoring records are summarised in Table 3.9 for TSP and Table 3.10 for VOC. The dust and LFG monitoring locations of the existing NENT Landfill is shown in Drawing No. 24315/13/504. In accordance with the long-term monitoring record, there is no exceedance of TSP since Year 1996. With the implementation of dust control measures and periodic EM&A monitoring, the performance of dust suppression measures are found to be sufficient and no adverse impact would be anticipated.

Table 3.9: Dust monitoring record for existing NENT Landfill operation

Monitoring ID	Location	Monitoring Parameters	Frequency	Observations	Mitigation Measures
D1	beside canteen	TSP/RSP	Once very 6 days. Increase to 3 days cycle in case of exceedance event	No exceedance since 1996	Increase water spraying frequency in tipping area and haul road by water trucks and sweeper trucks Apply automatic water spraying system Minimize the exposure duration of cut slopes and temporary capped areas by early hydroseeding.
D2	grassland beside Lagoon#1			No exceedance since 1996
D3	near Tung Lo Hang Village			There were 2 abnormalities occurred from 97 until present due to dry weather and high traffic rate of haul road M3. The abnormalities were rectified immediately and Independent Consultant was satisfied with the results.

Remark : The established EM&A mechanism and good site practice in existing NENT Landfill effectively contain any dust problem on site in a timely manner.

Table 3.10: VOC monitoring information for existing NENT Landfill operation

Monitoring ID	Location	Monitoring Parameters	Frequency	Observations	Mitigation Measures
V1	East of the landfill area	38 VOCs including 8 prominent VOCs: • Benzene; • Dichlorobenzenes; • Dichlorodifluor-methane; • Ethylbenzene;	Quarterly basis in March, June, September and December at four boundary locations and one gas well.	Only one abnormality was observed out of 1440 data ( 9-year monitoring data) ^[1]	Site investigation has identified neither potential leakage from the pipelines nor defect in extraction system. No exceedance was identified in subsequent special monitoring.
V2	North of the landfill area	• Methylene Chloride; • Toluene; and • Methane.	If the monitoring results show abnormality, site inspection and special monitoring will be conducted.	Only four abnormalities were observed out of 1440 data ( 9-year monitoring data) ^[1]
V3	West of the landfill area			Only five abnormalities were observed out of 1440 data ( 9-year monitoring data) ^[1]
V4	South of the landfill area			Only one abnormality was observed out of 1440 data ( 9-year monitoring data) ^[1]

Remark : [1] - VOC monitoring data and emission trend at source (within gas well) were compared with the results at the site boundary. Independent Consultant (IC) confirmed that the handful number of abnormal readings were not caused by / related to landfill operation.

Only 11 abnormalities out of 7200 monitoring data were observed over the past 9 years. For all these 11 abnormalities, the VOC levels at the gas well (source) were lower than that at the site boundary. Special monitoring had been conducted immediately and no exceedance was observed. An Independent Consultant (IC) had reviewed all these monitoring results and the findings for the site inspection by Environmental Team. It was concluded that the abnormal readings of VOC were not due to the operation of existing landfill. There were existing pig farm, recycling workshops and woodland in the nearby area that would also have emission of the same VOC elements. The reasons for the cause of the abnormality were originated from external sources. The reasons were justified and accepted by the IC, and these IC reports have been sent to EPD for review. Therefore, these abnormalities (i.e. non genuine cases) in VOCs have been discarded in this assessment.

The 9-year VOCs concentrations at the 4 monitoring points of the NENT Landfill site boundary are also tabulated in Table 3.11. It is observed that all VOC levels were within the contractual trigger levels which had been verified by the Independent Consultant.

The nearest ASR is located more than 300m away from the NENT Landfill site boundary. Taking into consideration the dispersion from the boundary to the ASRs, it is envisaged that the VOC level at ASRs will be further reduced significantly. During landfill restoration, the existing NENT Landfill will be capped with plastic sheet together with a thick layer of covering soil similar to other landfill under restoration, the VOC emission will be insignificant.

By the time when the NENT Landfill Extension is in operation, existing NENT will be capped with thick soil and equipped with active LFG extraction system, the surface emission from existing NENT will not be an issue based on the observation from the restored landfills in HK. In order words, the ambient VOC level would be significantly lower than the past monitoring data after restoration of existing NENT.

Table 3.11: 9-year averaged VOC concentration at the site boundary of the existing NENT Landfill (from Year 1997 to Year 2005)

Pollutants	Events	9-year monitoring data at the site boundary (in ppbv except methane) [a]
Pollutants		V1	V2	V3	V4
1_2-Dibromoethane (CASRN 106-93-4)	Monitoring result range	<1 *	<1 *	<1 *	<1 *
1_2-Dibromoethane (CASRN 106-93-4)	Long-term average	<1 *	<1 *	<1 *	<1 *
1_1_1-Trichloroethane (CASRN 71-55-6)	Monitoring result range	<1 * – 1.2	1	<1 * – 1.2	<1 * – 1.1
1_1_1-Trichloroethane (CASRN 71-55-6)	Long-term average	1	1	1	1
Benzene (CASRN 71-43-2)	Monitoring result range	<1 * – 2.8	<1 * – 1.8	<1 * – 8.2	<1 * – 2
Benzene (CASRN 71-43-2)	Long-term average	1.2	1.1	1.5	1.1
Butan-2-ol (CASRN 71-36-3)	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Butan-2-ol (CASRN 71-36-3)	Long-term average	<1 *	<1 *	<1 *	<1 *
Butanethiol	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Butanethiol	Long-term average	<1 *	<1 *	<1 *	<1 *
Butyl acetate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Butyl acetate	Long-term average	<1 *	<1 *	<1 *	<1 *
Butyl benzenes	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Butyl benzenes	Long-term average	<1 *	<1 *	<1 *	<1 *
Carbon Disulphide	Monitoring result range	<1 *	<1 *	<1 *	<1 *
(CASRN 75-15-0)	Long-term average	<1 *	<1 *	<1 *	<1 *
Chloroform (CASRN 67-66-3)	Monitoring result range	<1 * – 13	<1 * – 1.9	<1 * – 14	<1 *
Chloroform (CASRN 67-66-3)	Long-term average	1.6	1.1	1.3	<1 *
Decanes	Monitoring result range	<1 *	<1 * – 1.1	<1 *	<1 * – 3.2
Decanes	Long-term average	<1 *	1	<1 *	1.1
Dichlorobenzene (CASRN 106-46-7)	Monitoring result range	<1 * – 8.1	<1 * – 16	<1 * – 16	<1 * – 17
Dichlorobenzene (CASRN 106-46-7)	Long-term average	1.4	2.4	2.7	3.4
Dichlorodifluoromethane (CASRN 75-71-8)	Monitoring result range	<1 * – 21	<1 * – 83	<1 * – 82	<1 * – 12
Dichlorodifluoromethane (CASRN 75-71-8)	Long-term average	3.5	12.3	6.4	2.0
Dimethyl sulfide	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Dimethyl sulfide	Long-term average	<1 *	<1 *	<1 *	<1 *
Dipropyl ether (CASRN 111-43-3)	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Dipropyl ether (CASRN 111-43-3)	Long-term average	<1 *	<1 *	<1 *	<1 *
Ethanethiol	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Ethanethiol	Long-term average	<1 *	<1 *	<1 *	<1 *
Ethanol	Monitoring result range	<100 *	<100 *	<100 *	<100 *
Ethanol	Long-term average	<100 *	<100 *	<100 *	<100 *
Ethyl Benzene (CASRN 100-41-4)	Monitoring result range	<1 * – 44	<1 * – 6.4	<1 * – 70	<1 * – 65
Ethyl Benzene (CASRN 100-41-4)	Long-term average	3.4	2.1	6.2	5.1
Ethyl Butyrate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Ethyl Butyrate	Long-term average	<1 *	<1 *	<1 *	<1 *
Ethyl Propionate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Ethyl Propionate	Long-term average	<1 *	<1 *	<1 *	<1 *
Limonene (CASRN 5989-27-5)	Monitoring result range	<1 *	<1 * 4.2	<1 * – 3.5	<1 * – 2.8
Limonene (CASRN 5989-27-5)	Long-term average	<1 *	1.5	1.1	1.1
Methane	Monitoring result range in ppmv	0.5 – 32	0.05 – 55	1.8 – 56	0.5 – 57
Methane	Long-term average in ppmv	6.7	7.1	9.0	13.9
Methanethiol	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Methanethiol	Long-term average	<1 *	<1 *	<1 *	<1 *
Methanol (CASRN 67-56-1)	Monitoring result range	<100 *	<100 *	<100 *	<100 *
Methanol (CASRN 67-56-1)	Long-term average	<100 *	<100 *	<100 *	<100 *
Methyl Butyrate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Methyl Butyrate	Long-term average	<1 *	<1 *	<1 *	<1 *
Methyl Propionate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Methyl Propionate	Long-term average	<1 *	<1 *	<1 *	<1 *
Methylene chloride	Monitoring result range	<1 * – 53	<1 * – 73	<1* – 230	<1 * – 84
Methylene chloride	Long-term average	9.1	12.5	27.8	12.1
n-Heptane (CASRN 142-82-5)	Monitoring result range	<1 * – 5.4	<1* – 900	1 – 95	<1 * – 23
n-Heptane (CASRN 142-82-5)	Long-term average	1.2	44	7.2	2.6
n-Octane	Monitoring result range	<1 *	<1* – 760	<1 * – 54	<1 * – 5.8
n-Octane	Long-term average	<1 *	37.2	3.5	1.2
Nonane	Monitoring result range	<1 *	1 – 92	1– 18	1– 2.3
Nonane	Long-term average	<1 *	5.3	1.8	1.1
Propyl Benzene	Monitoring result range	<1*– 36	<1* – 21	<1* – 6.6	<1* – 28
Propyl Benzene	Long-term average	3.2	3.5	1.4	3.5
Propyl Propionate	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Propyl Propionate	Long-term average	<1 *	<1 *	<1 *	<1 *
Terpenes	Monitoring result range	<1* – 1.7	<1* – 1.5	<1* – 1.5	<1* – 2
Terpenes	Long-term average	1.0	1.0	1.0	1.1
Tetrachloroethylene (CASRN 127-18-4)	Monitoring result range	<1* – 2.6	<1 * – 2.9	<1 * – 2.7	<1 *
Tetrachloroethylene (CASRN 127-18-4)	Long-term average	1.1	1.1	1.1	<1 *
Toluene (CASRN 108-88-3)	Monitoring result range	<1* – 120	<1* – 42	<1* – 160	<1* – 78
Toluene (CASRN 108-88-3)	Long-term average	15.1	11.1	23.4	18.6
Trichloroethylene (CASRN 79-01-6)	Monitoring result range	<1 *	<1 * – 2.8	<1 *	<1 * – 1.7
Trichloroethylene (CASRN 79-01-6)	Long-term average	<1 *	1.1	<1 *	1.0
Undecane	Monitoring result range	<1 *	<1 *	<1 *	<1 *
Undecane	Long-term average	<1 *	<1 *	<1 *	<1 *
Vinyl chloride (CASRN 75-01-4)	Monitoring result range	<1* – 2.8	<1 *	1 – 13	<1 *
Vinyl chloride (CASRN 75-01-4)	Long-term average	1.1	<1 *	1.6	<1 *
Xylenes (CASRN 1330-20-7)	Monitoring result range	<1* – 64	<1* – 12	<1* – 110	<1* –120
Xylenes (CASRN 1330-20-7)	Long-term average	5.1	3.6	10.7	8.7

Remark (a) : lowest detection limit is 1ppbv for all pollutants; except for methanol and ethanol which is 100ppbv.

* : Below detection limits (assume to take the lowest detection limit as the monitoring result)

Owing to the lack of background monitoring data at the region/ASR, the long-term monitoring data of benzene and vinyl chloride at the site boundary are taken as the background as a conservative estimation. A background benzene and vinyl chloride concentrations of 1.225ppbv (3.9ug/m³) and 1.175ppbv (3ug/m³) are adopted, respectively. In fact, these values have included the contribution from surface gas emission, if any, from the tipping area.

Odour complaint records from existing NENT Landfill site office and EPD Environmental Compliance Division have been checked, and there were only 2 odour complaints in the existing NENT Landfill region in the past 5 years. Detailed investigations were conducted by the Independent Consultant and Environmental Team of the existing NENT Landfill and it was concluded that NENT Landfill was not the source of the odour nuisance.

Benzene, Vinyl Chloride and Non-methane Organic Carbon (NMOC) have also been monitored at the flare of the existing NENT Landfill, and the monitoring results are summarised below.

Table 3.12: Monitoring data from flare system

Pollutants	NMOC		Vinyl Chloride		Benzene
6-year Monitoring Results	Inlet	Outlet	Inlet	Outlet	Inlet	Outlet
Max (ppmv)	4800	33	1.6	<0.006	1	<0.006
Min (ppmv)	330	0.03	0.2	<0.001	0.2	<0.001
Average (ppmv)	2182	6.1	0.553 (1413 mg/m³)	0.0026 (6.646 mg/m³)	0.493 (1574.98 mg/m³)	0.0029 (9.265 mg/m³)
Removal Efficiency [aver value (inlet - outlet)/inlet]	99.7%		99.5%		99.4%

Owing to the lack of monitoring data for ASP and power generator, reference has been made with the typical control efficiency under Table 2.4-3, AP-42 of USEPA as the best estimate. The typical controlled efficiency of 99.6% and 99.8% are proposed for halogenated species and non-halogenated species for boiler/stream turbine. As compared to the controlled efficiency of 99.5% and 99.4% for halogenated species and non-halogenated species for flare, the efficiency in flare is on a conservative side. Therefore, the controlled efficiency for ASP and power generator will assume to be the same as that for the flare.

3.3.4 Proposed Plant for Landfill Gas Export Scheme in Existing NENT Landfill

The contractor of the existing NENT Landfill has signed an agreement with Hong Kong China Gas Co. (HKCG) for the Landfill Gas Export Scheme (LFGES). Under this LFGES, NENT Landfill shall supply a large quantity of LFG as fuel for production of towngas. The ultimate aim of the scheme is to enhance the environment and utilise as much LFG as possible as fuel. The entire system will extract most of the LFG from gas wells.

In order to maximise the extraction to achieve a cost-effective export scheme, the following practices have been implemented since Year 2007 to improve the extraction efficiency (means higher LFG production rate and higher energy recovery) as much as possible:

· Formulation of a working team to review all processes, control practice and extraction system in order to maximum the efficiency of the system.

· Maintain a slightly negative pressure within the entire tipping area (by suction).

· Increase the number of gas-extraction wells by reducing the radius of the catchment from 50m each to 25m.

· Improve the extraction efficiency by checking/reinstating gas wells with abnormally low extraction rate as a result of blockage/soil movement or sedimentation.

· Increase the coverage of inactive tipping area with HDPE sheet which can enhance the anaerobic decomposition (reduce air getting in).

· Extract LFG at newly-opened active tipping area (the only free opening for surface VOC emission).

At the restoration phase, no surface gaseous emission is anticipated after laying of plastic sheet and thick soil cover based on the observations from other restored landfills in HK.

3.3.5 Ambient air quality from EPD monitoring station

The nearest EPD air quality monitoring station to this Project is the Tai Po Monitoring station at Tai Po Government Office Building. According to EPD’s report on “Air Quality in Hong Kong” the area type of NENT Landfill Extension is under the “New Town” category.

Air quality data at the Tai Po Monitoring Station between 2000 to 2005 has been extracted. Table 3.13 below shows the average concentration of major air pollutants at the monitoring station.

Table 3.13: Background pollutant concentrations (5-year annual averaged)

Pollutant/ Year	2000	2001	2002	2003	2004 ^(a)	2005	5-year Averaged Concentration (ug/m³)
NO₂	47	50	48	52	N.A.	49	49.2
SO₂	12	13	11	14	N.A.	19	13.8
TSP	63	68	61	71	N.A.	61	64.8
RSP	48	50	46	54	N.A.	51	49.8

Note: (a) Annual averaged monitoring data for Tai Po is not available at Year 2004 due to upgrading of system.

3.4 Air Sensitive Receivers

Air sensitive receivers (ASRs) were identified in accordance with the guidelines in Annex 12 of the TM-EIAO. Existing ASRs were confirmed through site visits and review of survey maps. There were no planned ASRs on the latest Outline Zoning Plan. Representative ASRs within a distance of 500m from the Project boundary have been selected for the assessment. Their respective locations are shown in Drawing No. 24315/13/101 and Table 3.14 below.

Table 3.14: Summary of representative air sensitive receivers

Assessment Point No.	Assessment Point Description	Use	No. of Storey (including roof)	Shortest Horizontal Distance to Waste Boundary, m
ASR1	Wo Keng Shan Tsuen	Residential	3	420
ASR2	Village houses at Junction of Ng Chow Road and Wo Keng Shan Road	Residential	3	1040
ASR3	Cheung Shan Monastery	Religions	1	820
ASR4	Man Uk Pin	Residential	3	1130
ASR5	Man Uk Pin	Residential	3	1200
ASR6	Miu Keng	Residential	3	990
ASR7	Heung Yuen Wai	Residential	3	1240
ASR8	Tsung Yuen Ha	Residential	3	1790
ASR9	Ha Heung Yuen	Residential	3	1330
ASR10	Lin Ma Hang	Residential	3	900
ASR11	Tung Lo Hang	Pig Farm/ Residential	2	800
ASR12	Chuk Yuen	Residential	3	2000
ASR13	Nga Yiu Ha	Residential	3	1080
ASR14	Ping Yeung	Residential	3	960
ASR15	Ping Che	Residential	3	1890
ASR16	Ping Che Kat Tin	Residential	3	1870
ASR17	Kan Tau Wai	Residential	3	2250
ASR18	Tong Fong	Residential	3	2150
ASR19	Fung Wong Wu	Residential	2	2500
ASR20	Lei Uk	Residential	2	2450
ASR21	Chow Tin Tsuen	Residential	2	2750
ASR22	Tai Po Tin	Residential	2	2400
ASR23	Ha Shan Kai Wat	Residential	2	2800
ASR24	Sheung Shan Kai Wat	Residential	2	3000
ASR25	Tai Tong Wu	Residential	2	1650
ASR26	Loi Tung	Residential	2	1700
ASR27	Tong To Shan Tsuen (derelict and vacant)	Derelict and Vacant	3	450

　　　　　　3.5 Identification of Air Pollution Source and Environmental Impact

3.5.1 General Modes of Construction/Operation

Based on the practice in existing NENT Landfill operation and the construction/operational programme for future NENT Landfill Extension operation, the construction and operational events are summarised in Tables 3.15, 3.15a and 3.16 respectively. The existing and future landfill development phasing is illustrated in Appendix 2.2 and Drawing 24315/13/203.

Table 3.15: Summary of general modes of construction / capping activities

Stage	Mode of Construction	Period	Dust Impact	Remark
1	• Operation + Capping of Existing NENT Landfill – from end 2008 (assumed as worst case) • Site clearance - end 2008 to mid 2009 • Excavation & site formation - mid 2009 to end 2009 • Installation of liner, leachate & LFG systems - end 2009 to end 2010	About 24 months	• Existing NENT Landfill : About 3,000m^² of active area for capping/stockpiling; including the 40m x 30m operation area. • Phase 1 area of NENT Landfill Extension : About 20% of Phase I area under active site formation works. • Phase 2 area of NENT Landfill Extension : No activity. • Phase 3 area of NENT Landfill Extension : No activity.	• Worst-case scenario with the cumulative impact from existing NENT Landfill and its extension, active site areas in NENT and NENT Extension are closest to ASR. • Need advance work and involve larger construction area during critical period. • Setback distance of Stage 1 is closest to ASR.
2	• Site clearance – early 2010 to end 2010 • Excavation & site formation - end 2010 to mid 2012 • Installation of liner, leachate & LFG systems- mid 2011 to end 2012	About 36 months	• Existing NENT Landfill : Aftercare and no construction activity. • Phase 1 area of NENT Landfill Extension : 40m x 30m operation area. • Phase 2 area of NENT Landfill Extension : About 20% of Phase 2 area under active site formation works. • Phase 3 area of NENT Landfill Extension : No activity.	• More float time for construction and smaller construction area Setback distance of Stage 2 to ASR is further away than Stage 1. • Less impact than Stage 1 and detailed model will not be conducted.
3	• Site clearance - early 2013 to end 2013 • Excavation & site formation - mid 2013 to end 2014 • Installation of liner, leachate & LFG systems – early 2014 to end 2015	About 36 months	• Existing NENT Landfill : Aftercare and no construction activity. • Phase 1 & 2 areas of NENT Landfill Extension : 40m x 30m operation area. • Phase 3 area of NENT Landfill Extension : About 20% of Phase 3 area under active site formation works.	• Less impact than Stage 1 and detailed model will not be conducted.
4	• Installation of final capping - early 2020 to end 2021 • Planting and Landscaping - early 2021 to end 2022	about 24 months for capping and 24 months for planting	• Existing NENT Landfill : Aftercare and no construction activity. • NENT Landfill Extension : About 3,000m² of active excavated area for capping.	• Less impact than Stage 1 and detailed model will not be conducted.

Table 3.15a: Identification of worst-case scenario for construction / capping activities

	Existing NENT Landfill / Landfill Extension	Existing NENT Landfill	Landfill Extension Phase 1 Area	Landfill Extension Phase 2 Area	Landfill Extension Phase 3 Area
Earthwork activities	Operation 0.00018 Mm³ (40x30x0.15 m³ )	Capping 0.7 Mm³ (0.7 Mm³ fill)	Site formation 2.7 Mm³ (1.5 Mm³ cut + 1.2 Mm³ fill)	Site formation 2.8 Mm³ (1.9 Mm³ cut + 0.9 Mm³ fill)	Site formation 2.9 Mm³ (2.8 Mm³ cut + 0.1 Mm³ fill)
Programme	Everyday	24 months	15 months	30 months	24 months
Earthwork activities per month (Dust Impact)	0.0054 Mm³	0.03 Mm³	0.18 Mm³	0.10 Mm³	0.12 Mm³

Notes :

1. The earthwork activity in operation is considered negligible in comparison with the site formation activities.

2. In Stage 1 (Existing NENT + Extension Phase 1), total earthwork involved is estimated to be 0.21 Mm³ per month, and is close (~ 500m) to Wo Keng Shan Village.

3. In Stage 2 (only Extension Phase 2 with dusty construction), total earthwork involved is estimated to be 0.10 Mm³ per month. Phase 2 has more float time and thus the active construction area can be reduced. Thus the impact will be less than that in Stage 1.

Table 3.16: Summary of general modes of operation activities and identification of worst-case scenario

Stage	Mode of Operation	Period	Gaseous Emission and Odour Impact	Remark
A	• Existing NENT Landfill close down without tipping activities • Waste filling (within Phase 1 area) - end 2010 to end 2012	about 27 months	• Existing NENT Landfill : No operational activity. • Phase 1 area of NENT Landfill Extension : In operation with active tipping area about 40m x 30m. • Phase 2 area of NENT Landfill Extension : No operational activity. • Phase 3 area of NENT Landfill Extension : No operational activity.	• Existing NENT will be capped with no detectable surface gas and odour emission. • Less landfill gas and leachate generation than Stage C due to smaller waste filling volume. • Odour from the same active tipping area.
B	• Waste filling (within Phases 1 and 2 areas) - early 2013 to end 2015	About 36 months	• Existing NENT Landfill : No operational activity. • Phase 1 & 2 areas of NENT Landfill Extension : In operation with active tipping area about 40m x 30m. • Phase 3 area of NENT Landfill Extension : No operational activity.	• Less landfill gas and leachate generation than Stage C due to smaller waste filling volume. • Odour from the same active tipping area.
C	• Waste filling (within Phases 1 to 3 areas) -early 2016 to end 2020	About 60 months	• Existing NENT Landfill : No operational activity. • Phase 1, 2 & 3 areas of NENT Landfill Extension : In operation with active tipping area about 40m x 30m – worst-case with largest area (both active and inactive tipping areas) – can be controlled by good extraction system and coverage by plastic sheet. • Max number of operational plants adopted for the entire lifecycle (LFG, ASP and flares) – in practice with largest amount of gas generation due to cumulative of waste and maturity of the landfilling condition.	• Worst case for gaseous emission assessment. • Odour from the same active tipping area.
D	• Aftercare (Landfill gas and Leachate will be reduced) 2023 (for 30 years)	About 30 years	• Very light activities within the capped area. Active control system for landfill gas and leachate will be operated without causing adverse environmental impact. • No detectable surface gas and odour emission will be anticipated based on the observations from other restored landfills in HK.	• Less impact than Stage C. • No odour from restored landfill.

3.5.2 Source Identification

On-site and off-site air pollution sources during construction, operation, restoration and aftercare of the Project are summarised in Table 3.17 and 3.18 below:

Table 3.17: Sources of air pollution from Construction and Restoration Phases

Sources of air pollution
· Various construction activities during daytime · Wind erosion

Sources of air pollution

· Various construction activities during daytime

· Wind erosion

Table 3.18: Sources of air pollution from Operation Phase

Sources of air pollution

· Road traffic (insignificant due to very low traffic flow. There is no increase in total flow between the existing landfill and its future extension).

· Potential dust emission arising from daily operations (included in the general construction activities)

· VOC emission from active tipping area.

· Gases emission from flare, LFG power generator and ammonia stripping plants.

· Odour emission from leachate treatment facilities.

· Odour emission and surface gas emission from waste tipping operation.

3.5.3 Construction Phase

Heavy construction activities during daytime include site clearance, ground excavation, cut and fill (i.e. earth moving) operations, construction of the associated facilities and temporary road access within the site. In addition, wind erosion of all open sites including stockpiling will have potential impact.

Quantitative assessment on the impact of the identified sources on the ASRs is conducted.

3.5.4 Operation Phase

3.5.4.1 Vehicles

Current daily vehicular trip generation travelling to and from the existing NENT Landfill site along Wo Keng Shan Road is in the order of 500 veh/day. About 90 veh/hour is predicted from the NENT Landfill Extension during the peak operation hour. Given the more than 5m setback distances between Wo Keng Shan Road and ASRs, it is in compliance with the HKPSG requirements for vehicular emission control. As there will not be any overlapping of operation phases between NENT Landfill and its extension, adverse vehicular emission impact is not anticipated and quantitative assessment is not required.

In general, most of the refuse collection vehicles (RCV) for MSW and sludge are of enclosed-type and odorous gases are well contained during transit under normal circumstances. Sludge vehicles / special vehicles that required admission ticket, and special condition can be imposed on the cleanliness of vehicle and disposal period to avoid adverse cumulative impact. With reference to the existing NENT Landfill experience, potential odour impact from RCVs can be adequately controlled and unlikely to be an issue. Quantitative assessment is therefore not required.

In accordance with the HKPSG requirements, the minimum setback distance from earth moving activities to ASRs is 50m. Since the distance between the NENT Landfill Extension and the nearest ASRs is more than 300m, dust emission impact from landfill will be insignificant. In addition, all vehicles will be cleansed by wheel washing facility up to half of the vehicle height before leaving landfill, and soil brought away from landfill is thus not anticipated. Vehicle containing dusty material will also be covered by sheet to avoid any potential nuisance. Any dusty discharge on road is a violation of the Public Health & Municipal Ordinance. Therefore adverse off site dust impact is not anticipated.

3.5.4.2 Ammonia Stripping Plant, LFG Power Generator and Flaring Systems

The ammonia stripping plant and the thermal destructor at the existing NENT Landfill is an integrated unit (Figure 3.1 for illustrative diagram). When raw leachate passes through the ammonia stripping tower, ammonia dissolved in leachate will be removed. The ammonia laden air is combusted with landfill gas in the thermal destructor. Given particulate matter in the combustion process is negligible, emissions of ASP from the stacks are expected to be insignificant.

In accordance with US Environmental Protection Agency, AP-42 "Compilation of Air Pollutant Emission Factors" data, the thermal destructor is designed to destroy over 99% of VOCs (including methane, vinyl chloride, benzene and other non-methane hydrocarbons) in the landfill gas and exhaust from the ammonia stripping tower. Resulting discharge of benzene and vinyl chloride is reduced to a low limit. Similarly, all gaseous ammonia are completely oxidised to nitrogen and water.

Text Box:

Figure 3.1 Schematic Diagram of the Thermal Destructor (Within Ammonia Stripping Plant)

LFG extracted from NENT Landfill is utilised on site as the fuel source for LFG power generator and will be exported to HKCG for commercial use. The existing LFG power generator plant consists of 2 JGC 320 GS-B21 engine modules which can produce approximately 1.8 MW of electricity. The plant is running in pure isolated operation 24 hours a day because system connection to power grid is not allowed.

An agreement was formed between the contractor of the existing NENT Landfill and The Hong Kong & China Gas Company (HKCG) to export the LFG from NENT Landfill for towngas production. Landfill gas flaring system is installed in the existing NENT Landfill purely for the thermal destruction of surplus landfill gas. Under normal operating condition, all the available LFG will be fully utilised and no surplus LFG will be incinerated in the flaring system. As it is still early stage to formulate a LFG Export Scheme from future NENT Landfill Extension, the following assessment using similar flaring system as the existing landfill will be the worst-case scenario. In fact the flaring system for the extension site would be much smaller than the existing landfill because the total waste volume of the extension site is much less than the existing landfill.

NO₂, SO₂, Vinyl Chloride and Benzene as the key control parameters will be quantitatively modelled to assess their potential impact.

3.5.4.3 Leachate Treatment Facilities

Raw leachate temperature rises as a result of the bacteriological reaction during decomposition of waste. Its temperature is further increased by mixing with the treated effluent from the ammonia stripping plant (heating process). Leachate temperature is therefore well above the atmospheric temperature. Effect of atmospheric temperature variation has little influence on odour emission from leachate treatment plant. Odour samples collected for quantitative analysis is therefore not subjected to temperature adjustment.

To plan for the worst case scenario with cumulative impact from the restored landfill and the NENT Landfill Extension, a new on-site leachate treatment facility is assumed within the NENT Landfill Extension to serve the extension site, while the existing leachate treatment plant is retained to serve the existing landfill under restoration. The new leachate treatment facilities are located at the lowest elevation in order to cater for a gravity leachate collection system. It will be located close to the waste reception area of the existing NENT Landfill and Wo Keng Shan Tsuen. A quantitative assessment model is adopted for the odour impact evaluation of the two leachate treatment plants.

It is also noted that there would be upgrading works under the existing NENT Landfill Project to improve the existing leachate treatment plant. The proposed improvements include:

· Provision of ventilated cover for the existing lagoons and emissions are extracted to suitable odour removal filters with odour removal efficiency of 99%.

· Ferric nitrate or sodium hypochlorite can be added to oxidise the odourous chemical in the leachate. The pH value of leachate can be controlled to a suitable value from future on-site experiment such that the generation of any odourous H₂S and ammonia can be optimised.

· For the gaseous extraction system, the wind speed immediately above the leachate surface should be kept to minimal (in the order of 1E^-3 m/s) such that the odour emission strength from lagoon can be minimised. Suitable treatment system should be provided for odour removal. The ventilated gaseous emission from lagoons should be provided with 5-10 air change per hour for further dilution before discharge.

· The notional centre of the future discharge point (e.g. stack) shall be located at a location with maximum setback distance from the ASRs and further away from the notional centre of the lagoons. The location of discharge point and discharge height should be determined at the detailed design stage to ensure that the odour criterion at the ASRs will not be exceeded.

This will provide an environmental benefit to nearby environment in terms of visual and odour improvement.

As regards the leachate treatment facilities for the Landfill Extension (assuming conservatively that a new plant will be implemented), it is anticipated that the new plant will be built to the improved condition as described above, right from the beginning of its operation. Treatment method such as Sequencing Batch Reactor could be adopted for future lagoon.

Based on the preliminary estimation, owing to the capping of the existing NENT Landfill, leachate generation will be much reduced from currently 800m³/day to 350m³/day in the future. Most of the existing plants in NENT Landfill will not be operated in full scale. The leachate generation from NENT Landfill Extension will be gradually increased from 0 to about 800m³/day when all three phases of the landfill site are fully filled.

3.5.4.4 Waste Tipping Operation

Based on long-term operational practice in existing NENT Landfill, active tipping face during daily operation is normally exercised in a cell of 40mx30m in size while most of the inactive areas are covered by impermeable sheets. Dust emissions from the operation plants are minor and have been included as a cumulative source in the construction dust assessment. Potential odour impact is associated with the prevailing climate condition and is expected to be the worst-case in stable and calm weather. A quantitative assessment model is adopted for the odour impact evaluation of waste tipping operation.

Most of the waste received at NENT Landfill is municipal solid waste, with moisture content varies from 35 to 70%. There are other waste types with extremely high moisture
content of 70-85% (e.g. sludge, livestock waste and dredged mud) disposed
of at NENT. Waste received in NENT Landfill is wet in nature in particular during humid and wet season in Hong Kong.

Previous waste-statistical data have been reviewed as shown in Table 3.19. Such data on waste composition show that Special-Waste + Sludge amount to approximately 10% or less of the total.

Table 3.19 : Composition of Waste Disposal to NENT Landfill (in tpd)

Year	2000	2001	2002	2003	2004	2005
Landfilled Construction Wastes (LCW) + Municipal Solid Wastes (MSW)	3441	3452	3530	3064	2721	2656
Special-Waste + Sludge	132	144	149	186	215	303
TOTAL	3573	3596	3679	3250	2936	2959
% of LCW + MSW	96.3%	96.0%	96.0%	94.3%	92.7%	89.8%
% of Special Waste + Sludge	3.7%	4.0%	4.0%	5.7%	7.3%	10.2%

Owing to the future implementation of Integrated Waste Management Facilities (IWMF) and Sludge Treatment Facilities, much of the MSW will not be ended up at landfill and some of the sludge will be diverted elsewhere, the current 1:9 (Special-Waste & Sludge) : (LCW & MSW) composition is considered to be the worst-case condition in odour assessment.

3.5.4.5 Surface Gas Emissions

Surface emission is controlled by extracting LFG from the waste mass to the flaring system for final destruction. Active extraction system by pumping will be applied and the inactive tipping area/cell will be mostly sealed and covered by impermeable plastic sheet cover. The edge of plastic sheet cover will be buried and covered underground. For safety reason, the oxygen contents in the LFG need to be controlled to minimum so as to reduce the risk of explosion at the flare. Therefore, the chance of oxygen infiltration or LFG migration at the edge of the covering sheet will be kept to minimum. Periodic monitoring is conducted at the site boundary to ensure the ambient VOCs concentration is within the health and safety limit. In accordance with the site investigation records for the past 9 years, there were no genuine exceedance of VOCs limits at the site boundary.

As discussed in Section 3.3.4, surface emission from existing NENT will not be an issue after capping. For future NENT extension, contractor will enhance the LFG collection and treatment efficiency, a very small portion of VOC would be escaped from the active tipping area.

The additional large separation distance from site boundary of NENT Landfill Extension to ASRs will provide further protection. Subject to future engineering design, the arrangement of the landfill gas collection system and surface covering material for inactive tipping area could be further improved by modern technology. The event action limit for VOC can be lowered such that LFG surface mitigation can be better controlled. Regular VOC monitoring will be conducted during the construction, operation, restoration and aftercare stages of the NENT Landfill Extension. The trend of the VOC emission can be monitored at the site boundary. If there were abnormal building up of VOC at certain locations, special monitoring can be triggered. In order to ensure the surface VOC emission at ASRs can meet the “tightened” long-term chronic criteria from WHO, once every 3 months VOC monitoring at ASRs is recommended before the commissioning of NENT extension (as base-line) and on the 1^st year of tipping operation, during the period when the ASP and flare are not in operation. By comparing the monitoring data at the boundary and at ASRs, the cause of VOC and the general downwind dispersion effect from the boundary to the ASRs can be established.

The effects of Alternative Daily Cover Material (ADC), such as membrane daily cover, degradable polyethylene film and ConCover (spray type) on odour and VOCs emission control have been reviewed. As gas infiltration is directly dependant on the porosity of covering material and the porosity of ADC is less than conventional materials, the use of ADC in lieu will have positive effect on surface gas emission control. For the purpose of quantitative assessment, conventional covering method as the worst-case scenario is assumed.

ADC will be adopted as supplementary mitigation measure to be triggered by EM&A Programme on adverse meteorological conditions.

3.5.5 Restoration and Aftercare Phase

In view of the nature and scale of the final capping operation, lesser plant will be employed for dusty operations during the restoration phase for final capping. During aftercare period, only a few number of plant will be required for regular maintenance.

In terms of gaseous emission, there will be very light activities within the capped area. Active control system for landfill gas and leachate will be operational without causing adverse environmental impact. In accordance with the observations from some restored landfills, detectable surface gas and odour emission will not be anticipated.

As both the emission strength and scale of the operation will be less compared to the construction and operation phases, detailed assessment is not required since the impacts from construction and operation phases at the worse case have been assessed.

3.6 Assessment Methodology

3.6.1 Construction Phase

3.6.1.1 Dust Emission

The prediction of dust emissions is based on typical values and emission factors from USEPA, AP-42 "Compilation of Air Pollutant Emission Factors". References of the calculations of dust emission factors for different dust generating activities are listed in Table 3.20.

Table 3.20: References of dust emission factors for different activities

Activities	Reference	Operating Sites	Equations & Assumptions
Heavy construction activities including land clearance, ground excavation, cut and fill operations, construction of the facilities, drill & blast, plant movement and hauling over the site areas	S.13.2.3.3	All construction and excavation sites	E = 1.2 tons/acre/month of activity or = 2.69 Mg/hectare/month of activity
Wind Erosion	S.11.9, Table 11.9.4	All construction sites, and stockpile areas, (all open sites)	E = 0.85 Mg/hectare/yr (24 hour emission)

Activities

Reference

Operating Sites

Equations & Assumptions

Heavy construction activities including land clearance, ground excavation, cut and fill operations, construction of the facilities, drill & blast, plant movement and hauling over the site areas

S.13.2.3.3

All construction and excavation sites

E = 1.2 tons/acre/month of activity or

= 2.69 Mg/hectare/month of activity

Wind Erosion

S.11.9, Table 11.9.4

All construction sites, and stockpile areas, (all open sites)

E = 0.85 Mg/hectare/yr (24 hour emission)

As all the inactive areas within the landfill will be covered with impermeable sheets, wind erosion and general construction in the active area are the major sources of dust generation from the site. The construction periods are assumed 26 days a month and 12 hours a day. Whereas, there will be a 24 hours emission for wind erosion.

An ISCST3 model is adopted for air impact assessment in accordance with the Study Brief requirement. In accordance with the information from existing NENT Landfill, the area and plant used during construction phases have been identified. The development programme planned for future extension has also been reviewed, and worst-case scenarios has been identified and assessed:

· Worst-case Scenario: Cumulative impact of existing NENT Landfill under capping and Phase 1 site formation of NENT Landfill Extension (i.e. Stage 1 as refer to Table 3.15 and Table 3.15a). At that time, the existing NENT Landfill is almost filled up. To assess the worst-case condition, it is assumed that operation / capping / stockpiling will be occurred at NENT Landfill, whereas, site formation at NENT Landfill Extension will be occurred in Phase 1 area, which is closed to the ASRs at the east.

3.6.1.2 Dispersion Modelling

Dust impact assessment has been undertaken using the ISCST3 model. Table 3.21 gives the list of modelling parameters. Details of the emission rates are listed in Appendix 3.1. Location of dust emission sources are shown in Drawing No. 24315/13/102.

Table 3.21: Modeling parameters

Parameters	Input	Remark
Particle size distribution	1.25um = 3.06% 6.25um = 27.55% 20um = 69.39%	Major dominant dust emission source in Landfill is from unpaved road/working area. Owing to the lack of on-site monitoring data for particle distribution, it is the best estimate to assume the particle size distribution is the same as that for unpaved road. Table 13.2.2-2 of Section 13.2, USEPA AP-42, for unpaved road is adopted
Particle density	2.5g/m³	From Fugitive Dust Model (FDM) Manual
Background Concentration	5-year annual averaged value recorded at EPD’s Tai Po monitoring station (64.8µg/m³)	'TOTAL' Air Quality Guideline
Modeling mode	Rural with terrain effect Dry deposit mode activated	-
Meteorological data	Ta Kwu Ling (TKL) weather station	Mixing height of 500m adopted in accordance with EPD “Guidelines on Choice of Models and Model Parameters”
Emission period	General construction activities during daytime working hours (7am to 7pm) Site erosion over 24-hour period	-
ASR calculating levels	1.5m, 5m and 10m above local ground	-
Good Site Practice – Standard Precautionary Measures	Assume a 50% dust removal efficiency as in general practice based on AP-42 reference.	Periodic watering and covering of inactive construction area with plastic sheet cover. The effectiveness will be monitored in the EM&A.

3.6.2 Operation Phase

3.6.2.1 Emission from the Ammonia Stripping Plant, LFG Power Generator and Flaring Systems

Three operational modes have been considered (see Table 3.22). Monitoring and emission data from existing NENT Landfill has been requested from the existing NENT Landfill contractor and the project proponent; the emission inventory are summarised in Table 3.23 and detailed in Appendix 3.2. New plants have been planned in the future for the Landfill Gas Export Scheme (LFGES).

Referring to the monitoring data from the existing NENT Landfill, emission inventory from NENT Landfill Extension facilities are summarised in Table 3.24 and detailed in Appendix 3.2. For the worst-case scenario, it is assumed that a new LFGES will not be in place for the NENT Landfill Extension.

It is also noted from the existing NENT Landfill operation practices that the flare will only be operated when there is surplus of LFG. During the operation of ASP, the flare will not be operated. There are two set of power generators installed, one duty and one standby.

The locations of emission sources are shown in Drawing No. 24315/13/103.

Table 3.22: Modes of operation for various LFG facilities

		Modes of operation
	Plants (See Appendix 3.2 for details)	Case 1 – ASP On	Case 2 – ASP Off	Case 3 ^(d) – LFGES Off
Existing NENT ^(a)	Thermal Destructor in Ammonia Stripping Plant	ü	û	ü
	Two Existing Landfill Gas Flare (one on duty and one standby)	û	û	ü
	Existing LFG Power Generator (Electricity Generation –one on duty and one standby) ^(b)	ü	ü	ü
	New Landfill Gas Flare at later stage ^(b)	û	û	ü
New LFGES Facilities ^(a)	Future LFG Power Generator (Only one Electricity Generation)	ü	ü	ü
New LFGES Facilities ^(a)	New LFG Treatment Unit (LGFTU) from LFGES (2 compressor engines for two parallel processing streams of the LFG TU – purifying methane in LFG)	ü	ü	û
NENT Extension	Thermal Destructor in Ammonia Stripping Plant	ü	û	ü
	Two small Landfill Gas Flare at start - one on duty and one standby ^(b)	û	ü	ü
	New Landfill Gas Flare at later stage^{(b) (c)}	û	ü	ü
	LFG Power Generator (Electricity Generation – one on duty and one standby)	ü	ü	ü

Notes:

(a) The LFG Export Scheme aims to utilise all available gas collected from NENT. LFG will not be flared under normal condition. It is anticipated that maintenance of the LFG Export Scheme will occur only a few times in a year and each will last for a few days.

(b) Based on the long-term monitoring data, the flares system was not in operation all the time during the year (utilization rate is not high).

(c) The flare should be a smaller rating than that in the existing NENT Landfill in view of the smaller waste capacity of the landfill extension.

(d) In fact, the peak gaseous emission for existing landfill and the landfill extension will not overlap, due to the different time frame of the project implementation. The assessment is thus on conservative side.

Table 3.23: Pollutants emission rates from plants in Existing NENT Landfill

Source	Operating Conditions ^(a)	Pollutant	Estimated Emission (µg/m³) ^(e)	Emission Rates in atmosphere (g/s)
Thermal Destructor in Ammonia Stripping Plant (existing NENT)	1123K (dry condition), stack height= 19.5m, internal chimney diameter =3.5m, flow rate=223,000 m³/hr, gas exit velocity = 6.44m/s	Vinyl Chloride ^(c,f)	81.8	5.067 x 1E-3
		Benzene ^{(c, f)}	64.1	3.97 x 1E-3
		TNMOC as C	13,1926.4	8.172
		NO_x from Thermal Destructor	200,000	12.389
		NO₂ from Thermal Destructor	60,000^(b)	3.7167
		SO₂ from Thermal Destructor ^{(d, e)}	64,000	3.964
Two Existing Landfill Gas Flares – one duty and one standby(only operated during maintenance period of the LFG Export Scheme and zero emission under normal operation)	Existing (each): 1473K (dry condition), flow rate 138,491m³/hr, stack height= 8.105m, internal chimney diameter =1.835m, gas exit velocity = 14.546m/s	Vinyl Chloride ^(c)	81.8	3.147 x 1E-3
		Benzene ^(c)	64.1	2.466 x 1E-3
		TNMOC as C	13,1926	5.075156574
		NOx from Landfill Gas Flare	80,000	3.0776
		NO₂ from Landfill Gas Flare	24,000^(b)	0.9233
		SO₂ from Landfill Gas Flare	64,000 ^{(d, e)}	2.462
New Landfill Gas Flare (only operated during maintenance period of LFG Export Scheme and zero emission under normal operation)	One new stack: 1473K (dry condition), flow rate 387,774 m³/hr, stack height= 17m, internal chimney diameter =3.25m, gas exit velocity = 12.983m/s	Vinyl Chloride ^(c)	81.8	8.811 x 1E-3
		Benzene ^(c)	64.1	6.905 x 1E-3
		TNMOC as C	13,1926	14.21040909
		NOx from Landfill Gas Flare	80,000	8.6172
		NO₂ from Landfill Gas Flare	24,000^(b)	2.5852
		SO₂ from Landfill Gas Flare	64,000 ^{(d, e)}	6.894
Existing LFG Power Generator (Electricity Generation – one duty and one standby)	853K (dry condition), flow rate 10,839 m³/hr, stack height= 5.5m, internal chimney diameter =0.3m, gas exit velocity = 42.595m/s	Vinyl Chloride ^(c,f)	81.8	2.46 x 1E-4
		Benzene ^(c,f)	64.1	1.93 x 1E-4
		TNMOC as C	13,1926.4	0.3972
		NO_x from LFG power generator	500,000	1.5054
		NO₂ from LFG power generator	150,000^(b)	0.4516
		SO₂ from LFG power generator	64,000 ^{(d, e)}	0.1927
Future LFG Power Generator (Only One Electricity Generator)	853K (dry condition), flow rate 10,839 m³/hr, stack height= 5.5m, internal chimney diameter =0.3m, gas exit velocity = 42.595m/s	Vinyl Chloride ^(c,f)	81.8	2.46 x 1E-4
		Benzene ^(c,f)	64.1	1.93 x 1E-4
		TNMOC as C	13,1926.4	0.3972
		NO_x from LFG power generator	500,000	1.5054
		NO₂ from LFG power generator	150,000^(b)	0.4516
		SO₂ from LFG power generator	64,000 ^{(d, e)}	0.1927
New LFG Treatment Unit (LFGTU) of the LFGES (2 compressor engines for two parallel processing streams of the LFG TU) – Will not be operated during maintenance period of LFG Export Scheme	723K (dry condition), flow rate 10,896 m³/hr each, stack height= 6m, internal chimney diameter =0.5m, gas exit velocity = 15.415m/s ^(h)	NO_x from LFG power generator	500,000	1.5133
		NO₂ from LFG power generator	150,000^(b)	0.454
		SO₂ from LFG power generator	64,000 ^{(d, e)}	0.1937
		Vinyl Chloride ^(c,f)	81.8	2.47 x 1E-4
		Benzene ^(c,f)	64.1	1.94 x 1E-4
		TNMOC as C	13,1926.4	0.3993

Notes:

(a) Information on NENT Landfill thermal destructor, LFG flare and LFG power generator data are obtained from existing NENT. Real monitoring data is adopted for the model which has taken into account the actual oxygen content, pressure, etc. Modelling has taken a conservative assumption on conversion on molecular volume under high temperature. It is also assumed that oxygen content is sufficient for oxidation/combustion. The effect on the minor change in operating condition will be insignificant due to large margin in results before reaching criteria.

(b) Assuming NOx to NO₂ conversion factor is 30%

(d) Corresponding to monitoring result of 32 mg/m3 for H2S (i.e. 64mg/m3 SO2)

(e) Owing to the lack of monitoring data, assume zero SO2 removal efficiency under the worst-case scenario.

(f) The controlled efficiency for ASP and power generator will assume to be the same as that for the flare.

Table 3.24: Estimated pollutants emission rates from plants in NENT Landfill Extension (Assume no LFG Export Scheme)

Source	Operating Conditions	Pollutant	Estimated Emission (µg/m³) ^(e)	Emission Rates in atmosphere (g/s)
Thermal Destructor in Ammonia Stripping Plant (NENT Extension)	1123K (dry condition), stack height= 19.5m, internal chimney diameter =3.5m, flow rate=223,000 m³/hr, gas exit velocity= 6.44m/s	Vinyl Chloride ^(c)	81.8	5.067 x 1E-3
		Benzene ^(c)	64.1	3.97 x 1E-3
		TNMOC as C	13,1926.4	8.172
		NO₂ from Thermal Destructor	60,000^(b)	3.7167
		SO₂ from Thermal Destructor ^{(d, e)}	64,000	3.964
Two Landfill Gas Flare – one standby and one duty (NENT Extension)	Each: 1473K (dry condition), flow rate 138,491m³/hr, stack height= 8.105m, internal chimney diameter =1.835m, gas exit velocity = 14.546m/s	Vinyl Chloride ^(c)	81.8	3.147 x 1E-3
		Benzene ^(c)	64.1	2.466 x 1E-3
		TNMOC as C	13,1926.4	5.0752
		NOx from Landfill Gas Flare	80,000	3.0776
		NO₂ from Landfill Gas Flare	24,000^(b)	0.9233
		SO₂ from Landfill Gas Flare ^{(d, e)}	64,000	2.462
Additional Landfill Gas Flare at later stage ^(f)	1473K (dry condition), flow rate 138,491m³/hr, stack height= 8.105m, internal chimney diameter =1.835m, gas exit velocity = 14.546m/s	Vinyl Chloride ^(c)	81.8	3.147 x 1E-3
		Benzene ^(c)	64.1	2.466 x 1E-3
		TNMOC as C	13,1926.4	5.0752
		NO₂ from Landfill Gas Flare	24,000^(b)	0.9233
		SO₂ from Landfill Gas Flare ^{(d, e)}	64,000	2.462
LFG Power Generator (Electricity Generation – one standby and one duty)	853K (dry condition), flow rate 10,839 m³/hr, stack height= 5.5m, internal chimney diameter =0.3m, gas exit velocity = 42.595m/s	Vinyl Chloride ^(c)	81.8	2.46 x 1E-4
		Benzene ^(c)	64.1	1.93 x 1E-4
		TNMOC as C	13,1926.4	0.3972
		NO₂ from LFG power generator	150,000^(b)	0.4516
		SO₂ from LFG power generator ^{(d, e)}	64,000	0.1927

Notes:

(a) For conservative estimate, LFG flare, LFG power generator and ASP are assumed to be the same as that in existing NENT Landfill. Modelling has taken a conservative assumption on conversion on molecular volume under high temperature. It is also assumed that oxygen content is sufficient for oxidation/combustion. The effect on the minor change in operating condition will be insignificant due to large margin in results before reaching criteria.

(b) Assuming NOx to NO₂ conversion factor is 30%

(d) Corresponding to monitoring result of 32 mg/m³ for H₂S (i.e. 64mg/m³ SO₂)

(e) Owing to the lack of monitoring data, assume zero SO₂ removal efficiency under the worst-case scenario.

(f) The flare should be a smaller rating than that in the existing NENT Landfill in view of the smaller waste capacity of the landfill extension. However, for conservative assessment, the size of flare is assumed to be the same as the existing NENT Landfill.

3.6.2.2 Dispersion Modelling

Gaseous emissions have been assessed by ISCST3 model. The cumulative impacts from both the existing NENT Landfill and its future Extension are taken into account. The modelling parameters are listed in Tables 3.25.

Table 3.25: Modeling Parameters

Parameters	Input	Remark
Background Concentration	5-year annual averaged value recorded from NENT Landfill statistical Data	Follow 'TOTAL' Air Quality Guideline and health risk approach
Modeling mode	Rural with terrain effect
Meteorological data	Ta Kwu Ling (TKL) weather station; mixing height of 500m adopted in accordance with EPD Guidelines on Choice of Models and Model Parameters
Emission period	24-hour operation
ASR calculating levels	1.5m, 5m and 10m above local ground

Modelling results are compared with the respective criteria. A summary of the relevant criteria is listed in Table 3.26.

Table 3.26: Modeling Criteria

Parameters/ Pollutants

Relevant Criteria/Remark

· NO₂

· SO₂

(Remark : Adopt AQOs as criteria)

· 1-hour averaged criteria

· 24-hour averaged criteria

· Annual averaged criteria

· Benzene

· Vinyl Chloride

WHO, USEPA

(Remarks:

· Carcinogenic Risk: Annual average concentrations have been multiplied by the Unit Risk Factors to obtain the maximum individual lifetime risk. The individual annual risk could be obtained from the individual lifetime risk divided by 70 years which is the assumed average lifetime. The calculated individual lifetime risk has been compared with assessment criteria to check the acceptability of the risks at the identified ASRs.

· Non-carcinogenic risk: Annual average and maximum 1-hour average concentrations should be directly compared with the chronic reference concentration and the acute reference concentration.)

3.6.2.3 Cumulative Odour Impact from Open Tipping Area and Leachate Treatment Plant

3.6.2.3.1 Critical Weather Condition for Odour Impact Assessment

To determine the reasonably worst case scenario for odour impact assessment, the following steps have been taken:

(i) Meteorological data for the Years 2001 to 2004 from the Ta Kwu Ling (TKL) Weather Station were checked to identify the hours at which the worst stability class (i.e. Class F) tend to occur;

(ii) Odour emission strength measurements were taken for various sources, including daytime sampling for tipped waste not yet covered, lagoons; and night time / early morning sampling for daily cover overlying tipped waste. The odour strength from the highest emission source was identified.

The foregoing steps reveal the following:

(i) As shown in Appendix 3.3A, the vast majority of occurrences of stability Class F were at night or in the early morning hours.

(ii) Table 3.27 shows that odour emission strength measured from the surface of daily cover overlying tipped wastes (i.e. waste deposited for a number of hours) is higher than that from other emission sources.

Table 3.27 : Nominal odour emission rates during day time and night time

Time Period	Odour Sources	Odour Emission Strength OU/m²/s (extracted from Appendix 3.4)	Active Area (m²)	Nominal Odour Emission Rate (OU/s)
Night (28°C)	Daily cover overlying tipped waste	5.09	40 x 30	6108
Day (28°C)	Tipped (Aggregated)	4.34	40 x 3	521
	Compacted	3.04	40 x 17	2067
	Manoeuvring	1.41	40 x 10	564
	Equivalent for Day Time = (521+2067+564=) 3152 (i.e. Emission Rate Day time << Night time)
Day (32°C)	Tipped (Aggregated)	4.34+0.56 = 4.90	40 x 3	588
	Compacted	3.04+0.56 = 3.60	40 x 17	2448
	Manoeuvring	1.41+0.56 = 1.97	40 x 10	788
	Equivalent for Day Time = (588+2448+788=) 3824 (i.e. Emission Rate Day time << Night time

Notes : 1. Results show that the worst-case occurs at night time or early morning with stable and calm weather.

2. Night time emission source is found to be the worst-case

3. Statistical analysis of the 4 year meteorological data has been conducted. The maximum averaged temperature during operating hours (0700 to 1900 Hour) in the hottest month (Jul to Sept) is found to be 30 deg C. For conservative analysis, sensitivity test has been conducted using a hypothetical odour emission from tipping area at 32 deg C. This emission strength is estimated by linear extrapolation of odour strength from 28 deg C to 32deg C (0.56 OU increment for 4 deg increase in temp). As shown in the table above, the calculated OU/s for 32 degC is much lower than that of the night/early-morning case, with a large margin/difference in between. Even if the OU incremental rate may not exactly be linear, any variance should still be well within the aforementioned large margin. Hence, the worst case scenario should remain as the night-time/early-morning case.

In view of the above, the reasonably worst case scenario for odour impact assessment should be taken at night or early morning hours. The aforementioned meteorological data have also been checked for determining the temperature at such hours. In this regard, relevant average temperature data are tabulated below :

Table 3.27a : Averaged Temperature during night time for the summer months

Year	Average temperature from 1900 till 0700 Hours (from night to early morning hours) for the summer months (July to September)
2001	26°C
2002	26°C
2003	26°C
2004	27°C

To be conservative, the temperature is taken as 28°C for the reasonably worst case scenario. For completeness, the odour impact assessment covers all the hours in the 4 years of the meteorological data for different stability classes. The summary of results is tabulated in Appendix 3.10.

As concluded from the above analysis, the highest odour unit thus calculated correspond to the case of “28°C and stability Class F”.

3.6.2.3.2 In-situ Odour Sampling

In-situ odour sampling was adopted to collect odour strength for landfill site in Hong Kong. It is also noted that there is only one accredited laboratory in HK that can conduct such In-situ odour measurement (i.e. Odour Research Laboratory of HKPU).

The odour sampling and subsequent olfactometry tests were conducted by qualified odour panellists from the HKPU. The qualified odour panellists shall have their individual odour threshold of n-butanol in nitrogen gas in the range of 20 to 80 ppb/v as required by the European Standard Method (EN 13725). These panellists also fulfilled the following criteria:

- Odour panellists shall be at least 16 years of age and willing and able to follow instructions.

- Odour panellists shall be free from any respiratory diseases and are not normally working at or living in the area in the vicinity of NENT Landfill Extension.

At the time of sampling in early to mid 2006, the best and the only available apparatus for odour sampling is the wind tunnel hood method which applies blow fan to extract the odorous gas into a sample bag for subsequent olfactometry analysis. It was comprehensively studied in a research paper “Theoretical and Practical Considerations in the Use of Wind Tunnel for Odour Emission Measurement, Jay Witherspoon et al, Jun 2002 Annual Conference & Exhibition Proceedings, AWMA” that this wind tunnel hood technique would overestimate the emission strength due to high suction velocity and will produce very conservative odour results.

Under this wind tunnel hood method for odour emission strength assessment, air samples are taken in-situ by a wind-tunnel hood. The hood, with an internal height of 250mm, is placed over the air-sampling location such that the air to be sampled is drawn and collected from this 250mm high space inside the hood. The odour-strength thus measured therefore represents the odour-strength of an air-sample at an average height of 125mm above ground. Therefore, a reference ground wind speed at 0.125m above ground was adopted for subsequent analysis of the reasonable worst-case scenario to tally with the configuration of the wind tunnel hood used.

3.6.2.3.3 Dispersion Modelling

A total of 17 odour samples from the active tipping areas, inactive areas and the leachate lagoons of the NENT Landfill were collected by Lam Geotechnics and Odour Research Lab of HKPU for the assessment. The ambient surface odour emission fluxes and pollutant concentrations have been measured during the reasonable worst-case temperature. All odour samplings and subsequent olfactometry tests were conducted by qualified specialists and odour panellists. The odour sampling locations are shown in Figure 3.2 below.

Detail of the derivation of odour strength is listed in Table A of Appendix 3.3.

Figure 3.2 Odour Sampling Locations in Existing NENT Landfill

Details of the emission strength and modelling input parameters are listed in Appendix 3.4 and summarised in Table 3.28. For ease of odour modelling, odour emission strengths adopted in the ISCST3 model have been normalised at 0.5m/s.

Table 3.28 : Odour strength applied in the model (Temperature under reasonable worst-case condition)

Sampling Location	Modelled Odour Source Emission Strength normalised at 0.5m/s ground wind speed, OU/m² –s
Day time samplings :
Tipping – Special-Waste + Sludge	8.21
Tipping – MSW	3.91
Tipping – compacted waste	3.04
Tipping – aggregated (90% of MSW and 10% of Special-Waste + Sludge)	4.34
Manoeuvring (at tipping area)	1.41
Raw Leachate Lagoon – before ASP	27.86
Leachate Lagoon – after ASP	10.32
Aeration Lagoon	3.95
Effluent Lagoon	2.83
Night time sampling :
Daily cover overlying tipped waste	5.09

These air samples for odour assessment were taken at the sampling locations tabulated in Table 3.28 above using a Wind Tunnel Hood, the only method available in Hong Kong then. [The taking of samples, together with the subsequent laboratory assessment, were carried out by Hong Kong Polytechnic University (HKPU), also the only service provider available.]

It has been published in numerous papers that the Wind Tunnel Hood method of sampling is suitable for odour assessment. However, it is also widely published that the odour emission concentration measured from samples taken by a Wind Tunnel Hood will need to be corrected, before being used for odour assessment. This is because the Wind Tunnel Hood utilises a fan to draw-in odorous gas, whereas in reality odorous gas is emitted under natural ground wind.

In this regard, two relevant documents* recommended that the following equation be applied for such correction:

………………………………………….Equation (1)

where SOER₁ = odour emission concentration under Condition 1, i.e. as measured from samples taken by the Wind Tunnel Hood;

SOER₂ = odour emission concentration under Condition 2, i.e. the corrected figure;

V₁ = wind velocity under measurement Condition 1, i.e. the wind speed due to the aforementioned draw-in by fan;

V₂ = wind velocity under Condition 2, i.e. the natural ground wind speed.

[* : The two documents are :

(a) Odour assessment at the NENT Landfill Site, by the Odour Research Laboratory, Hong Kong Polytechnic, 22 March 2006;

(b) Odour emission factors for assessment and prediction of Italian MSW landfills odour impact, by Selena Sironi et al, 25 May 2005 ]

In particular, Paper (b) above specifically stated that the Wind Tunnel Hood method of sampling, together with the application of Equation (1) above, were applied exactly for odour assessment for landfills in Italy. This renders Paper (b) all the more relevant, in serving as a reference on the applicability of both the Wind Tunnel Hood and Equation (1) above.

The following points should also be noted:

(1) There is one overseas case (Review of Odour Management in New Zealand Technical Report August 2002) stating that different approaches should be adopted for odour assessment on solid and liquid surfaces, with the former based on diffusion consideration instead of adopting Equation (1) above. However, the relevance of this overseas case is doubtful in view of the following points:

(1.1) The aforementioned Paper (b) referred specifically to landfill projects; its relevance to the NENT Landfill Extension project is therefore considered to be stronger than that of the New Zealand case.

(1.2) The odour of landfill wastes is contributed by both the solid and the liquid contents. It would be impracticable to classify the surface precisely as “solid”, or “liquid”, or “which way in between”, for applying the New Zealand case as a reference.

(1.3) As far as the landfill wastes in Hong Kong are concerned, a large proportion of the odour obviously comes from wastes of high moisture contents (see also Section 3.5.4.4). Even if the wastes are overlain by daily cover, the odour sample taken by the Wind Tunnel Hood still predominantly reflects odour originated from high moisture wastes anyway.

(2) Very recently, a new type of odour sampling apparatus namely flux chamber sampling method has become available in Hong Kong, adopting diffusion as the sampling method (instead of using a fan to draw-in a sample). It is widely documented that odour emission rates obtained by wind tunnel hood methodology are grossly over estimates when compared with results obtained by using flux chamber sampling method. In local context, comparison of odour emission rates from waste / landfill obtained by the two methodologies revealed that odour emission rates by the wind tunnel hood method [before applying Equation (1)] is about 10 to 20 times higher than those using flux chamber method [without applying Equation (1)] under similar field conditions. On the other hand, the effect of applying Equation (1) is found to be of a similar order as applying a factor of about ¹/₁₀ to ¹/₂₀.

(3) The application of Equation (1) has been limited to a lower bound ground wind velocity of 0.001m/s. In practice, this is equivalent to a maximum wind speed adjustment factor of 1/20, tally with the observation in local context (see (2) above). For cases where the assessed ground wind speed is lower than 0.001 m/s, the value for V₂ will be capped as 0.001 m/s for the purpose of applying Equation (1). It must, however, be noted that the aforementioned [1/10 to 1/20] ratios between wind tunnel hood results (before applying Equation (1)) and flux chamber results refer STRICTLY to odour sampling at landfills only.

Owing to the boundary layer effect, the wind velocity near ground level would be very low. With site observations of topographic condition, the surface roughness is estimated to be 0.1245m (see Appendix 3.5). The hourly wind velocities near ground level were estimated using an advanced meteorological equation with reference to the 35,040 hourly (4 years) ground wind speeds from the TKL weather station. The hourly emission concentration is then calculated by the above Equation (1). Details are listed in Appendix 3.6.

Other modelling parameters were determined according to EPD’s “Guidelines on Choice of Models and Model Parameters”. The 5-second Odour Unit (OU) at the ASRs was assessed by ISCST3 model.

Based on dispersion curve in the ISCST3 manual, the modelling results will be representative for period between 1 hour to 15-minutes averaging time. A conversion factor was applied to convert the average time from 15-minute to 3-minute in accordance with a stability dependent power law relationship as follows:

where X_l = concentration for the longer time averaging time;

X_s = concentration for the shorter time averaging time;

t_s= shorter averaging time;

t_l = longer averaging time;

P = power law exponent (Stability Class A: 0.5, B: 0.5, C: 0.333, D: 0.2, E:0.167, F: 0.167)

The 3-minutes averaged value was then converted to a 5-second averaged value, in response to the requirement of the odour level criterion under TM-EIAO. In accordance with the reference papers stated in EPD “Guidelines on Choice of Models and Model Parameters”, the conversion factors from 15-minutes to 3-minutes and then 3- minutes to 5-seconds have been determined and tabulated in Table 3.29.

Table 3.29: Multiplying factors for averaging time correction for odour assessment (taking account of EPD’s Guideline on Choice of Models and Model Parameters)

Atmospheric Stability Class	Conversion Factor from 1 hour to 15 min	Conversion Factor from 15 min to 3 min	Conversion Factor from 3 min to 5s	Resultant Conversion Factor from 1 hour to 5s
A	1	2.236	10	22.36
B	1	2.236	10	22.36
C	1	1.709	5	8.545
D	1	1.380	5	6.9
E	1	1.308	5	6.54
F	1	1.308	5	6.54

Odour emission has been assessed by ISCST3 air quality model taking into account the Resultant Conversion Factor into account. However, referring to other overseas reference, the Resultant Conversion Factor tabulated above is on the conservative side. For instance, a conversion factor of 3.0 is adopted for Class D condition in Australia. In addition, “Workbook of Atmospheric Dispersion Estimates” also stated that ISCST3 results already represent 3 min averaged condition, a resultant Conversion Factor of 10 for A/B and 5 for C to F Classes should have been adopted.

The overall modelling parameters are summarised in Table 3.30 for ease reference.

Table 3.30: Modelling parameters

Parameters	Input	Remark
Background Concentration	No (major source from landfill)	In accordance with the preliminary design information, three scenarios have been assessed (also see Remark below):
Modeling mode	Rural model with elevated terrain	· Central zone scenario: tipping at the central part of the NENT Landfill Extension site. In view of the existing topography (landfill bowl shape), the central part is the highest occurrence zone during the operation life.
Meteorological data	Ta Kwu Ling (TKL) weather station, mixing height of 500m adopted in accordance with EPD Guidelines on Choice of Models and Model Parameters
Emission period	· Daytime emission from tipping at active cell · Night time emission from daily cover overlying tipped waste	· Northern zone scenario: tipping at the northern part of the NENT Landfill Extension site close to Tong To Shan Tsuen.
	· Whole day for emission from leachate treatment plant · Effective temporary covers with impermeable plastic sheets will be applied at the inactive tipping areas, and no emission is anticipated. · Active LFG extraction system with an engineering cap will be applied at the restored NENT Landfill and no emission is anticipated.	· Western zone scenario: tipping at the western part of the NENT Landfill Extension site close to Wo Keng Shan Tsuen. Owing to the limitation of the ISCST3 model, all circular lagoons are simulated as rectangular area sources with same surface area.
ASR calculating levels	1.5m, 5m and 10m above local ground
Odour strength/results	Input data using odour strength at normalised ground wind speed	The actual odour strength/results are then calculated based on ground wind speed Equation (1) for wind tunnel hood sampling method.

Remark: Eastern zone scenario is NOT assessed since there is only steep hill slope in the area. No ASR in the vicinity was identified.

The locations of emission sources from existing NENT Landfill and its extension are shown in Drawing No. 24315/13/104.

3.7 Prediction and Evaluation of Air Quality Impact

3.7.1 Construction Phase

With the provision of good site practice, such as covering of the inactive area by impermeable sheets and periodic watering, a dust removal efficiency of 50% has been adopted as in other approved EIA reports, such as Kowloon Southern Link. The predicted maximum 1-hour and 24-hour average TSP concentration at the ASRs will be within the 500µg/m³ and 260 µg/m³ criterion, respectively. No adverse construction dust impact is anticipated. When the actual construction programme and methodology is finalised by the DBO Contractor, the precautionary measures can be further reviewed and verified by the EM&A monitoring.

Tables 3.31 and 3.32 show the 1-hour and 24-hour averaged TSP levels at the identified ASRs. Details of the assessment results are given in Appendix 3.7. The 1-hour and 24-hour averaged TSP contours at the worst affected level (1.5m above ground) is illustrated in Drawing 24315/13/105 and 24315/13/106.

Table 3.31: Predicted TSP levels at various ASRs

ASRID	Predicted 1-hour TSP concentration µg/m³, when NENT Landfill is under restoration and Phase 1 of NENT Landfill Extension is in site formation ^(1&2)
ASRID	1.5m	5m	10m
ASR1	230	212	167
ASR2	142	138	128
ASR3	162	157	144
ASR4	185	181	170
ASR5	154	151	143
ASR6	157	154	143
ASR7	180	176	166
ASR8	91	91	89
ASR9	163	161	152
ASR10	138	135	126
ASR11	240	231	205
ASR12	127	126	122
ASR13	175	171	159
ASR14	155	151	139
ASR15	111	111	107
ASR16	114	113	110
ASR17	116	115	112
ASR18	117	116	113
ASR19	101	100	98
ASR20	112	111	109
ASR21	107	106	104
ASR22	106	105	103
ASR23	101	100	99
ASR24	94	94	92
ASR25	124	123	118
ASR26	141	140	135
ASR27	183	174	151

Remark : ⁽¹⁾ TSP background of 64.8µg/m³ has been incorporated.

⁽²⁾ Adopted good site practice of periodic watering and covering inactive area with plastic sheet as the precautionary measures, a 50% dust removal efficiency is applied as in other approved EIA Reports. This can be verified by subsequent EM&A monitoring.

Table 3.32: Predicted max 24-hour averaged TSP levels at various ASRs

ASRID	Predicted 24-hour TSP concentration µg/m³, when NENT Landfill is under restoration and Phase 1 of NENT Landfill Extension is in site formation ^{(1& 2)}
ASRID	1.5m	5m	10m
ASR1	102	99	90
ASR2	82	82	80
ASR3	96	95	92
ASR4	81	81	80
ASR5	80	80	79
ASR6	85	84	83
ASR7	83	83	81
ASR8	72	72	71
ASR9	81	81	80
ASR10	77	77	76
ASR11	103	102	97
ASR12	76	76	76
ASR13	86	85	83
ASR14	82	81	79
ASR15	74	74	73
ASR16	72	72	72
ASR17	74	74	74
ASR18	71	71	71
ASR19	69	69	69
ASR20	71	71	70
ASR21	70	70	70
ASR22	71	71	71
ASR23	70	70	70
ASR24	69	69	69
ASR25	83	82	81
ASR26	77	76	76
ASR27	105	103	97

Remark : ⁽¹⁾ TSP background of 64.8µg/m³ has been incorporated

⁽²⁾ Adopted good site practice of periodic watering and covering inactive area with plastic sheet as the precautionary measures, a 50% dust removal efficiency is applied as in other approved EIA reports. This can be verified by subsequent EM&A monitoring.

3.7.2 Operation Phase

3.7.2.1 AQO Criteria Pollutant

The maximum 1-hour averaged NO₂ and SO₂ concentrations at the ASRs were predicted under three operating modes; namely LFGES Off, ASP On (normal condition with ASP in operation) and ASP Off (with flare in operation). The 1-hour averaged NO₂ and SO₂ contours at the worst affected level (10m above ground) for the Normal Operation with ASP in operation are illustrated in Drawing 24315/13/107 and 24315/13/108 respectively.

Tables 3.33 to 3.35 show the NO₂ and SO₂ levels at the identified ASRs for various modes of operation. Detailed results are listed in Appendix 3.8. The maximum 1-hour averaged NO₂ and SO₂ concentrations are 120 µg/m³and 50 µg/m³(during the normal operation with ASP “On”), which would be 40% and 6% of the AQOs. The maximum 24-hour and annual averaged NO₂ and SO₂ concentrations are also well within the AQO. Based on these preliminary results with a large margin, NO₂and SO₂ emission will not be a concern.

Table 3.33: Predicted NO₂ and SO₂ levels at various ASRs (Case 3 ─ LFGES Off)

ASRID	Predicted NO₂ concentrations at the worst affected height (all at 10m above ground) ⁽¹⁾			Predicted SO₂ concentrations at the worst affected height (all at 10m above ground) ⁽¹⁾
ASRID	max 1-hr averaged NO₂ (µg/m³)	max 24-hr averaged NO₂ (µg/m³)	max Annual Averaged NO₂ (µg/m³)	max 1-hr averaged SO₂ (µg/m³)	max 24-hr averaged SO₂ (µg/m³)	Max Annual Averaged SO₂ (µg/m³)
ASR1	59.8	52.4	49.6	25.2	15.9	14.1
ASR2	59.5	51.8	49.6	29.7	16.0	14.2
ASR3	62.1	53.4	49.8	32.4	17.5	14.3
ASR4	61.3	53.5	49.4	31.4	17.7	14.1
ASR5	60.8	53.8	49.5	30.4	18.0	14.1
ASR6	61.8	52.1	49.5	31.8	17.3	14.1
ASR7	61.5	51.5	49.4	29.6	15.9	13.9
ASR8	67.0	53.0	49.7	37.6	16.7	14.2
ASR9	63.9	51.5	49.4	32.6	16.0	14.0
ASR10	71.2	57.8	49.6	28.6	19.9	14.2
ASR11	66.3	55.2	50.4	31.1	16.3	14.4
ASR12	65.4	53.1	50.1	35.4	17.1	14.6
ASR13	60.1	51.8	49.7	29.8	16.1	14.2
ASR14	60.0	53.4	49.8	30.5	16.5	14.2
ASR15	57.2	51.8	49.5	25.8	16.6	14.1
ASR16	57.6	52.3	49.5	26.4	16.2	14.1
ASR17	57.8	51.2	49.7	24.7	16.1	14.4
ASR18	57.3	51.0	49.6	24.9	15.7	14.3
ASR19	56.9	50.9	49.7	24.4	16.0	14.4
ASR20	56.5	51.1	49.7	23.8	15.8	14.3
ASR21	56.4	51.1	49.7	24.1	16.1	14.4
ASR22	55.9	51.5	49.5	24.2	16.4	14.1
ASR23	55.8	51.9	49.4	24.0	16.5	14.1
ASR24	55.8	52.0	49.5	24.3	16.9	14.1
ASR25	58.7	51.9	49.6	27.2	17.5	14.2
ASR26	60.0	51.8	49.5	29.5	16.8	14.1
ASR27	91.7	72.3	50.0	47.0	33.8	14.5

Remark : ⁽¹⁾ NO₂ background of 49.2µg/m³ has been incorporated;

⁽²⁾ SO₂ background of 13.8µg/m³ has been incorporated; and

Table 3.34: Predicted NO₂ and SO₂ levels at various ASRs (Case 1 ─ ASP On) – worst-case condition

ASRID	Predicted NO₂ concentrations at the worst affected height (in general 10m above ground unless otherwise stated) ^{(1) & (3)}			Predicted SO₂ concentrations at the worst affected height (all at 10m above ground) ⁽¹⁾
ASRID	max 1-hr averaged NO₂ (µg/m³)	max 24-hr averaged NO₂ (µg/m³)	max Annual Averaged NO₂ (µg/m³)	max 1-hr averaged SO₂ (µg/m³)	max 24-hr averaged SO₂ (µg/m³)	Max Annual Averaged SO₂ (µg/m³)
ASR1	70.4	55.7	49.8	23.0	16.6	14.1
ASR2	59.8	54.0	49.7	21.5	16.1	14.1
ASR3	67.5	56.1	49.8	23.7	17.0	14.1
ASR4	64.3	54.2	49.5	22.6	16.5	13.9
ASR5	64.0	55.6	49.6	22.6	17.4	14.0
ASR6	59.1	52.9	49.5	22.9	16.0	14.0
ASR7	69.2	53.2	49.5	23.1	15.6	13.9
ASR8	68.6	54.7	49.9	27.4	16.4	14.1
ASR9	71.1	53.7	49.5	24.0	15.8	14.0
ASR10	87.0	62.9	49.8	33.2	20.8	14.1
ASR11	81.3	57.3	50.5	21.3	15.7	14.2
ASR12	63.9	54.6	50.4	26.5	16.4	14.5
ASR13	68.7	54.2	49.8	22.2	16.0	14.1
ASR14	65.4	57.3	49.9	22.9	17.5	14.1
ASR15	55.8	52.9	49.5	19.5	16.0	14.0
ASR16	60.4	54.5	49.6	19.6	16.3	14.0
ASR17	60.4	51.5	49.8	21.1	15.1	14.2
ASR18	59.1	51.2	49.6	20.8	14.9	14.1
ASR19	59.3	51.5	49.7	20.3	14.9	14.1
ASR20	58.3	51.3	49.6	20.0	14.9	14.1
ASR21	58.2	51.5	49.7	19.9	15.0	14.1
ASR22	59.4	53.6	49.5	19.3	15.7	14.0
ASR23	57.4	52.8	49.5	19.1	15.9	14.0
ASR24	60.0	54.4	49.5	19.0	16.1	14.0
ASR25	57.6	52.8	49.6	21.2	15.6	14.0
ASR26	58.4	52.6	49.5	21.8	15.5	14.0
ASR27	119.6	76.7	50.0	50.4	28.3	14.2

Remark : ⁽¹⁾ NO₂ background of 49.2µg/m³ has been incorporated;

⁽²⁾ SO₂ background of 13.8µg/m³ has been incorporated; and

⁽³⁾ Max 1hr NO2 : ASR27 at 1.5m

Table 3.35: Predicted NO₂ and SO₂ levels at various ASRs (Case 2 ─ ASP Off)

ASRID	Predicted NO₂ concentrations at the worst affected height (in general 10m above ground unless otherwise stated) ^{(1) & (3)}			Predicted SO₂ concentrations at the worst affected height (in general 10m above ground unless otherwise stated) ^{(2) & (4)}
ASRID	max 1-hr averaged NO₂ (µg/m³)	max 24-hr averaged NO₂ (µg/m³)	max Annual Averaged NO₂ (µg/m³)	max 1-hr averaged SO₂ (µg/m³)	max 24-hr averaged SO₂ (µg/m³)	Max Annual Averaged SO₂ (µg/m³)
ASR1	70.1	55.6	49.8	22.7	16.5	14.1
ASR2	59.2	53.7	49.7	25.8	15.7	14.0
ASR3	67.3	56.0	49.8	25.1	16.8	14.2
ASR4	64.2	53.6	49.4	22.9	16.5	14.0
ASR5	63.9	54.4	49.5	23.1	16.5	14.0
ASR6	58.2	52.7	49.5	24.1	15.5	14.0
ASR7	68.9	53.0	49.5	23.4	15.8	13.9
ASR8	68.7	54.6	49.9	26.8	16.8	14.2
ASR9	70.9	53.6	49.5	25.5	15.7	14.0
ASR10	81.9	61.2	49.7	27.7	19.3	14.1
ASR11	80.9	57.2	50.5	26.4	16.2	14.3
ASR12	64.0	54.5	50.3	25.0	16.7	14.5
ASR13	68.5	54.0	49.7	24.3	15.9	14.2
ASR14	65.4	57.0	49.9	25.4	17.1	14.2
ASR15	55.2	52.1	49.4	21.6	15.1	13.9
ASR16	60.3	54.2	49.5	22.2	15.9	14.0
ASR17	60.1	51.5	49.7	20.5	15.2	14.1
ASR18	58.8	50.9	49.6	21.0	15.2	14.1
ASR19	58.9	51.5	49.6	20.1	15.1	14.1
ASR20	57.8	50.9	49.6	20.5	15.3	14.1
ASR21	58.1	51.4	49.6	20.5	15.3	14.1
ASR22	59.3	53.5	49.5	20.2	15.6	14.0
ASR23	57.3	52.0	49.4	19.9	15.0	13.9
ASR24	60.0	54.3	49.5	20.6	16.0	14.0
ASR25	55.1	52.5	49.5	22.0	16.2	14.0
ASR26	57.6	52.4	49.4	21.5	15.4	14.0
ASR27	110.2	73.0	49.9	42.3	30.1	14.3

Remark : ⁽¹⁾ NO₂ background of 49.2µg/m³ has been incorporated;

⁽²⁾ SO₂ background of 13.8µg/m³ has been incorporated;

⁽³⁾ Max 1hr NO₂ : ASR 19 and ASR 27 at 1.5m; Max 24hr NO₂ : ASR 27 at 1.5m; and

⁽⁴⁾ Max 1hr SO₂ : ASR 9; Max 24hr SO₂ : ASR 23 at 1.5m

3.7.2.2 Non-criteria Pollutants

The maximum hourly and annual averaged concentrations of non-criteria pollutants (vinyl chloride and benzene) were predicted. The cumulative cancer risk for benzene and vinyl chloride (i.e. cancer risk of vinyl chloride plus that of benzene) is also within the cancer risk criteria. The contribution from the ASP, flare and generator plants are insignificant. Tables 3.36 to 3.38 show the non-criterion pollutant levels at the identified ASRs. Detailed results for non-criteria pollutants are given in Appendix 3.9. The predicted 1-hour and annual averaged contours for benzene are illustrated in Drawing Nos. 24315/13/109 and 24315/13/110; whereas, 1-hour and annual averaged contours for vinyl chloride are illustrated in Drawing Nos. 24315/13/111 and 24315/13/112.The emission impacts at the ASR are within the acute and chronic health risk criteria.

Table 3.36: Predicted health risk level for benzene and vinyl chloride at various ASRs (Case 3 – LFGES Off)

ASRID	Predicted max vinyl chloride concentrations at the worst affected height			Predicted max benzene concentrations at the worst affected height
ASRID	max 1-hr and annual averaged vinyl chloride (µg/m³ ) (with background)⁽¹⁾	Predicted Individual Risk Level per Year for Vinyl Chloride Chronic Effect	Within Acute and Chronic Reference Conc and Individual Risk Level	max 1-hr and annual averaged benzene level (µg/m³ ) (with background) ⁽²⁾	Predicted Individual Risk Level per Year for Benzene Chronic Effect	Within Acute and Chronic Reference Conc and Individual Risk Level
ASR1	~3	5.29E-12	within	~3.9	6.21E-12	within
ASR2	~3	6.57E-12	within	~3.9	7.71E-12	within
ASR3	~3	9.14E-12	within	~3.9	1.071E-11	within
ASR4	~3	4.57E-12	within	~3.9	5.36E-12	within
ASR5	~3	5.86E-12	within	~3.9	6.86E-12	within
ASR6	~3	6.29E-12	within	~3.9	7.29E-12	within
ASR7	~3	2.57E-12	within	~3.9	3.E-12	within
ASR8	~3	7.71E-12	within	~3.9	9.21E-12	within
ASR9	~3	3.71E-12	within	~3.9	4.29E-12	within
ASR10	~3	6.86E-12	within	~3.9	7.93E-12	within
ASR11	~3	1.657E-11	within	~3.9	1.95E-11	within
ASR12	~3	1.529E-11	within	~3.9	1.8E-11	within
ASR13	~3	7.71E-12	within	~3.9	9.E-12	within
ASR14	~3	8.14E-12	within	~3.9	9.43E-12	within
ASR15	~3	5.E-12	within	~3.9	5.79E-12	within
ASR16	~3	4.71E-12	within	~3.9	5.57E-12	within
ASR17	~3	1.014E-11	within	~3.9	1.2E-11	within
ASR18	~3	9.14E-12	within	~3.9	1.071E-11	within
ASR19	~3	1.043E-11	within	~3.9	1.221E-11	within
ASR20	~3	1.0E-11	within	~3.9	1.179E-11	within
ASR21	~3	1.129E-11	within	~3.9	1.329E-11	within
ASR22	~3	6.29E-12	within	~3.9	7.29E-12	within
ASR23	~3	4.57E-12	within	~3.9	5.36E-12	within
ASR24	~3	5.57E-12	within	~3.9	6.43E-12	within
ASR25	~3	7.43E-12	within	~3.9	8.79E-12	within
ASR26	~3	5.86E-12	within	~3.9	6.86E-12	within
ASR27	~3	1.286E-11	within	~3.9	1.5E-11	within

Remark :

⁽¹⁾ Future Vinyl chloride background of 3µg/m³ has been incorporated; and

⁽²⁾ Benzene background of 3.9µg/m³ has been incorporated

Table 3.37: Predicted health risk level for benzene and vinyl chloride at various ASRs (Case 1 – ASP On) : worst-case condition

ASRID	Predicted max vinyl chloride concentrations at the worst affected height			Predicted max benzene concentrations at the worst affected height
ASRID	max 1-hr and annual averaged vinyl chloride (µg/m³ ) (with background)⁽¹⁾	Predicted Individual Risk Level per Year for Vinyl Chloride Chronic Effect ⁽¹⁾	Within Acute and Chronic Reference Conc and Individual Risk Level	max 1-hr and annual averaged benzene level (µg/m³ ) (with background)⁽²⁾	Predicted Individual Risk Level per Year for Benzene Chronic Effect	Within Acute and Chronic Reference Conc and Individual Risk Level
ASR1	~3	5.29E-12	within	~3.9	2.49E-11	within
ASR2	~3	5.14E-12	within	~3.9	2.49E-11	within
ASR3	~3	6.29E-12	within	~3.9	3.E-11	within
ASR4	~3	2.71E-12	within	~3.9	1.29E-11	within
ASR5	~3	3.71E-12	within	~3.9	1.71E-11	within
ASR6	~3	3.57E-12	within	~3.9	1.71E-11	within
ASR7	~3	2.43E-12	within	~3.9	1.11E-11	within
ASR8	~3	6.29E-12	within	~3.9	3.E-11	within
ASR9	~3	2.71E-12	within	~3.9	1.29E-11	within
ASR10	~3	6.14E-12	within	~3.9	2.91E-11	within
ASR11	~3	1.17E-11	within	~3.9	5.49E-11	within
ASR12	~3	1.19E-11	within	~3.9	5.57E-11	within
ASR13	~3	5.43E-12	within	~3.9	2.57E-11	within
ASR14	~3	6.29E-12	within	~3.9	2.91E-11	within
ASR15	~3	3.43E-12	within	~3.9	1.54E-11	within
ASR16	~3	3.86E-12	within	~3.9	1.8E-11	within
ASR17	~3	6.43E-12	within	~3.9	3.E-11	within
ASR18	~3	5.E-12	within	~3.9	2.4E-11	within
ASR19	~3	6.E-12	within	~3.9	2.83E-11	within
ASR20	~3	5.14E-12	within	~3.9	2.4E-11	within
ASR21	~3	6.14E-12	within	~3.9	2.91E-11	within
ASR22	~3	3.57E-12	within	~3.9	1.71E-11	within
ASR23	~3	3.29E-12	within	~3.9	1.54E-11	within
ASR24	~3	3.43E-12	within	~3.9	1.63E-11	within
ASR25	~3	4.14E-12	within	~3.9	1.97E-11	within
ASR26	~3	3.E-12	within	~3.9	1.46E-11	within
ASR27	~3	7.86E-12	within	~3.9	3.69E-11	within

Remark :

⁽¹⁾ Future Vinyl chloride background of 3µg/m³ has been incorporated; and

⁽²⁾ Benzene background of 3.9µg/m³ has been incorporated

Table 3.38: Predicted health risk level for benzene and vinyl chloride at various ASRs (Case 2 – ASP Off)

ASRID	Predicted max vinyl chloride concentrations at the worst affected height			Predicted max benzene concentrations at the worst affected height
ASRID	max 1-hr and annual averaged vinyl chloride (µg/m³ ) (with background)⁽¹⁾	Predicted Individual Risk Level per Year for Vinyl Chloride Chronic Effect	Within Acute and Chronic Reference Conc and Individual Risk Level	max 1-hr and annual averaged benzene level (µg/m³ ) (with background)⁽²⁾	Predicted Individual Risk Level per Year for Benzene Chronic Effect	Within Acute and Chronic Reference Conc and Individual Risk Level
ASR1	~3	4.86E-12	within	~3.9	2.31E-11	within
ASR2	~3	4.43E-12	within	~3.9	2.06E-11	within
ASR3	~3	6.71E-12	within	~3.9	3.17E-11	within
ASR4	~3	3.E-12	within	~3.9	1.37E-11	within
ASR5	~3	3.86E-12	within	~3.9	1.8E-11	within
ASR6	~3	3.71E-12	within	~3.9	1.8E-11	within
ASR7	~3	2.57E-12	within	~3.9	1.2E-11	within
ASR8	~3	7.43E-12	within	~3.9	3.51E-11	within
ASR9	~3	3.57E-12	within	~3.9	1.71E-11	within
ASR10	~3	4.86E-12	within	~3.9	2.31E-11	within
ASR11	~3	1.57E-11	within	~3.9	7.46E-11	within
ASR12	~3	1.23E-11	within	~3.9	5.74E-11	within
ASR13	~3	6.86E-12	within	~3.9	3.26E-11	within
ASR14	~3	7.29E-12	within	~3.9	3.43E-11	within
ASR15	~3	2.57E-12	within	~3.9	1.2E-11	within
ASR16	~3	3.14E-12	within	~3.9	1.46E-11	within
ASR17	~3	6.29E-12	within	~3.9	2.91E-11	within
ASR18	~3	5.71E-12	within	~3.9	2.66E-11	within
ASR19	~3	5.71E-12	within	~3.9	2.66E-11	within
ASR20	~3	6.E-12	within	~3.9	2.83E-11	within
ASR21	~3	6.E-12	within	~3.9	2.83E-11	within
ASR22	~3	3.86E-12	within	~3.9	1.89E-11	within
ASR23	~3	2.14E-12	within	~3.9	1.03E-11	within
ASR24	~3	3.29E-12	within	~3.9	1.54E-11	within
ASR25	~3	4.29E-12	within	~3.9	1.97E-11	within
ASR26	~3	3.29E-12	within	~3.9	1.54E-11	within
ASR27	~3	9.43E-12	within	~3.9	4.46E-11	within

Remarks :

⁽¹⁾ Future Vinyl chloride background of 3µg/m³ has been incorporated; and

⁽²⁾ Benzene background of 3.9µg/m³ has been incorporated

3.7.2.3 Odour

Based on the assumption that the existing leachate treatment plant will be improved under the existing NENT Landfill Project (as discussed in Section 3.5.4.3) and a proposal that similar odour control measurements will be adopted for the leachate treatment facilities for NENT Landfill Extension.

The proposed leachate treatment facilities include :

· Adopted updated treatment method such as Sequencing Batch Reactor for future leachate treatment. Provision of ventilated cover for the leachate storage lagoons / tanks and emissions extracted to suitable odour removal filters with odour removal efficiency of 99%.

· The notional centre of the future discharge point (e.g. stack) shall be located at a location with maximum setback distance from the ASRs and further away from the notional centre of the leachate storage lagoons / tanks. The location of discharge point and discharge height should be determined at the detailed design stage to ensure that the odour criterion at the ASRs will not be exceeded.

The maximum 5-sec averaged odour concentrations at the ASRs were predicted for three representative operating scenarios; namely central tipping, northern tipping and western tipping.

The maximum odour level will only occur at the northern tipping under low wind speed stability condition during night time / early morning. Details are listed in Table 3.39. The predicted maximum odour level is estimated to be 7.4 OU (at ASR27 with only a derelict isolated single house) which will occur during night time with stable and calm condition only.

For the other ASRs, all the assessed odour concentration results are within the 5 OU (5 sec. averaged) criterion.

Table 3.39: Predicted Odour Concentration (OU, 5s averaging) under reasonably worst-case condition

ASR ID	Predicted cumulative odour concentrations for ASRs at height above local ground, OU
	Central tipping + night time daily cover overlying tipped waste + existing & future (enclosed) lagoons			Western tipping + night time daily cover overlying tipped waste + existing & future (enclosed) lagoons			Northern tipping + night time daily cover overlying tipped waste + existing & future (enclosed) lagoons
	1.5m	5m	10m	1.5m	5m	10m	1.5m	5m	10m
ASR1	0.5	0.4	0.3	3.7	3.1	1.8	1.4	1.3	1.1
ASR2	0.1	0.1	0.1	2.2	2.1	1.8	1.2	1.2	1.1
ASR3	0.1	0.1	0.1	0.6	0.5	0.5	0.1	0.1	0.1
ASR4	0.1	0.1	0.1	0.2	0.2	0.2	0.9	0.8	0.8
ASR5	0.9	0.9	0.8	0.9	0.9	0.8	0.1	0.1	0.1
ASR6	1.4	1.3	1.2	0.1	0.1	0.1	0.2	0.2	0.2
ASR7	0.2	0.2	0.1	0.2	0.2	0.1	0.2	0.2	0.1
ASR8	0.5	0.5	0.4	0.8	0.8	0.7	0.1	0.1	0.1
ASR9	0.7	0.7	0.6	1.0	0.9	0.8	1.1	1.1	1.0
ASR10	0.4	0.3	0.3	0.2	0.2	0.1	1.7	1.6	1.2
ASR11	0.6	0.3	0.2	0.6	0.3	0.2	0.9	0.8	0.7
ASR12	0.1	0.1	0.1	0.8	0.8	0.7	0.3	0.3	0.3
ASR13	0.9	0.8	0.7	2.1	2.0	1.7	0.5	0.4	0.4
ASR14	1.6	1.5	1.3	0.3	0.2	0.2	1.5	1.5	1.3
ASR15	0.6	0.6	0.6	0.2	0.2	0.1	0.2	0.2	0.2
ASR16	0.7	0.7	0.6	0.5	0.5	0.5	0.1	0.1	0.1
ASR17	0.1	0.1	0.1	0.2	0.2	0.2	0.6	0.6	0.5
ASR18	0.7	0.6	0.6	0.8	0.8	0.7	0.1	0.1	0.1
ASR19	0.3	0.3	0.3	0.3	0.3	0.3	0.1	0.1	0.1
ASR20	0.2	0.2	0.2	0.1	0.1	0.1	0.3	0.3	0.3
ASR21	0.5	0.5	0.5	0.6	0.6	0.5	0.1	0.1	0.1
ASR22	0.5	0.5	0.4	0.0	0.0	0.0	0.0	0.0	0.0
ASR23	0.4	0.4	0.4	0.1	0.1	0.1	0.0	0.0	0.0
ASR24	0.1	0.1	0.1	0.5	0.5	0.5	0.4	0.4	0.4
ASR25	0.7	0.7	0.7	0.8	0.8	0.7	0.4	0.4	0.4
ASR26	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.1
ASR27	1.8	1.7	1.2	2.4	2.3	1.9	7.4 (on average 8 hours per year)	6.2 (on average5 hours per year)	3.4
Max:	1.8	1.7	1.3	3.7	3.1	1.9	7.4	6.2	3.4

Residual Odour Impact

As regards the only case in which the 5 OU (5-sec. averaged) criterion is exceeded, i.e. at isolated occasions at ASR 27, the following points should be noted with reference to EIAO-TM Clause 4.4.3 and its Annex 20 Clause 7:

(a) Factors in EIAO-TM Clause 4.4.3:

(i) effects on public health and health of biota or risk to life – Although there is one minor occurrence (occurring at only one ASR, and only on rare occasions) of exceedance, it will not entail any significant health effect, as ASR 27 is a derelict isolated single house. Even in the event that the house is redeveloped, the aforementioned exceedance is readily avoidable because it occurs only at rare occasions (on average 8 hours a year, during night time at stable and calm weather conditions). For the whole operating life of the NENT landfill extension, the tipping face located at the worst "northern tipping" should be much less than 2 years. Landfilling could be planned to operate at locations far enough away from ASR 27 under such rare oaccasions, should the house be redeveloped in the future.

(ii) the magnitude of the adverse environment impacts – The assessed worst case odour concentration is 7.4 OU (5-sec. averaged) does exceed the 5 OU criterion, but as stated above, it occurs only at ASR 27 which is a derelict house.

(iii) the geographic extent of the adverse environmental impacts – The exceedance occurs at only one ASR.

(iv) the duration and frequency of the adverse environmental impacts – As stated above, the exceedance occurs on average 8 hours a year, in other words at a frequency of 0.09% or 1 in 1062, which is obviously a very low frequency.

(v) the likely size of the community or the environment that may be affected by the adverse impacts – ASR 27 is a derelict isolated single house.

(vi) the degree to which the adverse environmental impacts are reversible or irreversible – Odour impact is transient in nature; moreover, as stated above since only one ASR is involved, it is readily practicable to adjust the landfill operation to avoid the exceedance in case the derelict house at ASR 27 is redeveloped.

(vii) the ecological context – The exceedance does not involve ecological context.

(viii) the degree of disruption to sites of cultural heritage – The exceedance does not involve cultural heritage context.

(ix) international and regional importance – The exceedance does not involve international and regional importance.

(x) both the likelihood and degree of uncertainty of adverse environmental impacts – The exceedance does not involve such uncertainty.

(b) Questions in Annex 20 Clause 7:

Have the available standards, assumptions and criteria which can be used to evaluate the impacts been discussed?	Yes
Have the predicted impacts been compared to the available standards and criteria?	Yes
Have the residual impacts, which are the net impacts with the mitigation measures in place, been described and evaluated against the available Government policies, standards and criteria?	Yes
Have the residual impacts been discussed and evaluated in terms of the impact on the health and welfare of the local community and on the protection of environmental resources?	Yes
Have the magnitude, location and duration of the residual impacts been discussed in conjunction with the value, sensitivity and rarity of the resource?	Yes, See (a) above
Where there are no generally accepted standards or criteria for the evaluation of residual impacts, have alternative approaches been discussed and, if so, is a clear distinction made between fact, assumption and professional judgment?	Not applicable
Have the residual impacts, if any, arising from the implementation of the proposed mitigation measures, been considered?	Yes

In view of the rarity or low frequency of occurrence of the exceedance, and the fact that it occurs only at one ASR, which is a derelict house without any inhabitant, the exceedance ought not be considered as an issue of environmental concern.

The predicted 5-sec averaged odour contour for the worst-case scenario at northern tipping and western tipping are shown in Drawing No. 24315/13/113 and 24315/13/114.

From a practical point of view, much of the odour would be originated from odorous VOC. In accordance with the long-term VOC monitoring record, the VOC levels at NENT Landfill have been kept at low level as a result of the good site practices and effective control in inactive tipping areas. The odour prediction results are in line with the long-term observation from VOC monitoring data (odorous source). With sufficient setback distance of the nearby ASRs from the NENT Landfill Extension, odour would not be a key issue of the extension site. Nonetheless, good site practices and odour patrol are recommended to monitor the future condition.

3.8 Precautionary Measures

3.8.1 Construction Phase

Dust emission from construction vehicle movement is confined within the worksites area. Watering facilities will be provided at every designated vehicular exit point.

Good site practice is recommended during construction phase. Covering with impermeable sheet should be provided for the inactive tipping area. Periodic dust monitoring at the nearby ASRs should be conducted and detailed in the EM&A manual.

In case of non-compliance, additional mitigation measures in accordance with the EM&A requirements will be implemented.

3.8.2 Operation Phase

3.8.2.1 Stack Discharge from ASP, Flare and LFG Power Generator

Similar to the existing NENT Landfill operation, the maximum allowable discharge limit for ASP, flare and LFG power generator should be specified in the specification. Subject to the subsequent EPD’s requirement on chimney installation, once every 3 months regular stack monitoring of vinyl chloride, benzene, TOC, NO_xand SO₂ shall be carried out to demonstrate compliance during the operations.

3.8.2.2 Odour from Leachate Treatment Facilities

As mentioned in Section 3.7.2.3, the proposed leachate treatment facilities in NENT Landfill Extension include :

· The overall arrangement should be investigated in details by the DBO Contractor and agreed with IEC and EPD. As such, the odour emission from the future leachate treatment facilities will be insignificant.

3.8.2.3 Odour from Waste Transfer and Tipping Activities

The following are some odour precautionary measures that shall be considered by EPD and FEHD as environmental initiatives:

· As an improvement measure to enhance to environmental standard for waste transfer, EPD could take the initiative to recommend others to use enclosed type RCVs (dominantly government vehicles and sludge vehicles).

· Cleaning / watering of the surface and clearing of the waste water receptor of government RCV is recommended before leaving refuse transfer station or government Refuse Collection Point (FEHD).

· The use of alternative daily cover (less permeable layer) instead of inert material should be considered under worst-case weather condition, subject to EM&A Programme.

· The use of immediate daily cover for odorous waste such as sewage sludge, animal waste etc. under critical condition should also be considered, subject to EM&A Programme.

· For the time being, there is no population in the derelict Tong To Shan Tsuen. If there is new residents moving in, thicker daily cover / alternative daily cover should be applied at phase 3 of the extension site such that the emission strength for the night time can be reduced (similar performance as that in the inactive tipping area). Odour patrol at Tong To Shan Tsuen should be arranged during night time / early morning in order to ensure the effectiveness of the measures.

· In accordance with some reference from New Zealand, odour from active tipping area can be much reduced if the waste is covered by sandwich covering material such that it is confined in a solid/semi solid condition. Such covering material will be acted as sandwich protective layers to block the interaction of waste. Only diffusion mode (small scale) will be present. These would be applied during very hot and stable weather condition. Thicker daily cover can be arranged in case odour patrol identify potential odour nuisance, subject to EM&A Programme.

· During stable and calm weather condition and subject to EM&A programme, tipping could be arranged to further increase the setback distance.

3.8.2.4 VOC Surface Emission and Future Ambient Level

· Similar to other restored landfill, the existing NENT Landfill will be capped by plastic covering sheet and a thick layer of soil during restoration period. Surface gas emission from existing restored landfill is insignificant. With the installation of permanent capping, together with the LFG management system, there are double preventive measures against surface emission. Odour and VOC emission from the restored NENT Landfill is not anticipated.

· For the NENT Landfill Extension, with an effective temporary covers, together with LFG management system (active extraction to collect LFG within the landfill cells), natural escape of odourous VOC to the nearby ASRs is negligible.

· EM&A will be conducted to review the future VOC ambient concentration and effectiveness of the extraction system. VOC monitoring at ASRs to be conducted once every 3 month is recommended before the commissioning of NENT Landfill Extension (as base-line) and in the 1st year of tipping operation, during the period when the ASP and flare are not in operation. By comparing the monitoring data at the boundary and at ASR, the cause of VOC and the general downwind dispersion effect from the boundary to the ASR can be established.

· Development of LFG Export Scheme / energy recovery scheme will be encouraged for the NENT Landfill Extension.

3.8.3 Restoration and Aftercare Phase

Similar measures as in construction and operation phases will be applied.

3.9 Residual Environmental Impact

There is no residual environmental impact during construction phase, operation and aftercare/restoration phases.

3.10 Implication of IWMF Implementation

If the potential of Integrated Waste Management Facility (IWMF) implementation were considered in 2010’s, the incoming waste characteristics to the NENT Landfill Extension site would be altered substantially, mainly with inert incinerator ashes. Based on the observation from other similar facilities such as Chemical Waste Treatment Centre at Tsing Yi, the incinerator ashes will be in the form of fused solid sludge. The flying ash issue will not be a concern. The air quality impact (VOC and odour from both active tipping and leachate treatment plant) is anticipated to reduce significantly.

3.11 Conclusion

The potential air quality impacts during construction, operation, restoration and aftercare phases of the NENT Landfill Extension Project have been assessed.

3.11.1 Construction Phase

Construction dust modelling results show that there would be no adverse construction dust impact on the ASRs in the vicinity of the NENT Landfill Extension site. Good site practices, however, are still recommended throughout the construction period to further eliminate any dust problem. Requirements for regular monitoring of dust concentration are detailed in the EM&A Manual.

3.11.2 Operation Phase

3.11.2.1 Stack Gas and Surface Gas Emission

Dispersion modelling results show that gaseous emissions from ammonia stripping plant, LFG power generator and flaring system of the NENT Landfill Extension will have no adverse impact on the ASRs throughout the operational period of the NENT Landfill Extension. Subject to the subsequent EPD’s requirement on chimney installation, once every 3 months regular stack monitoring of vinyl chloride, benzene, TOC, NOx and SO₂ shall be carried out to demonstrate compliance during the operations.

By adopting the best practice using effective active extraction system, plastic sheet cover at inactive tipping area plus periodic EM&A monitoring, the surface gas emission can be significant reduced. With the provision of these measures, no adverse health risk impact is anticipated.

Regular emission monitoring of these facilities is recommended to ensure their proper functioning.

3.11.2.2 Odour

Odour assessment results show that there would be no adverse impact on the ASRs during the operational period of the Project, except the derelict and vacant Tong To Shan Tsuen. Residual impact at Tong To Shan Tsuen is considered to be very scarce and transient in nature and can be mitigated with good site practices (including application of thicker daily cover, progressive restoration for inactive tipping face.), as well as periodic odour patrol should be carried out during active tipping period. In case the weather condition is poor (stable and calm weather), tipping should be arranged at area further away from the ASRs as far as practicable, and/or thicker daily cover / alternative daily cover should be applied subject to EM&A programme.

Ventilated cover with emissions extracted to suitable odour removal filters for odour removal has been proposed for existing lagoons. Updated treatment method such as Sequencing Batch Reactor has been proposed for future lagoon. Ventilated cover shall be provided with emissions extracted and diverted to suitable filters with odour removal efficiency of 99%. Ferric nitrate or sodium hypochlorite shall be added to oxidise the odourous chemical in the leachate. The pH value of leachate can be controlled to a suitable value from future on-site experiment such that the generation of any odourous H₂S and ammonia can be optimised.

For the gaseous extraction system, the wind speed immediately above the leachate surface should be kept to minimal such that the odour emission strength from lagoon can be minimised. Suitable treatment system should be provided for odour removal. The ventilated gaseous emission from lagoons should be provided with 5-10 air change per hour for further dilution before discharge.

The notional centre of the future discharge point (e.g. stack) shall be located at a location with maximum setback distance from the ASRs and further away from the notional centre of the lagoons. The location of discharge point and discharge height should be determined at the detailed design stage to ensure that the odour criterion at the ASRs will not be exceeded.

For the time being, there is no population in the derelict Tong To Shan Tsuen. If there is new resident moving into this derelict village, thicker daily cover / alternative daily cover should be applied at phase 3 of the extension site such that the emission strength can be reduced (similar to that in the inactive tipping area). Site walk should be conducted once every three months to the Tong To Shan Tsuen to verify whether there is new resident moving in during the operational stage. Once, there is any new resident, night time / early morning odour patrol at Tong To Shan Tsuen should be arranged to ensure that daily covering material is sufficient without causing odour nuisance. These will be specified in the EM&A manual.

3.11.3 Restoration and Aftercare Phases

The scale of construction activities during the restoration and aftercare phases of the NENT Landfill Extension will be small when compared with the construction phase. Construction dust is therefore not anticipated to be an issue.

The impact of stack gas emissions from treatment facilities will be much reduced during these phases given the gradual reduction in leachate and LFG generation rates over time.

Odour in restored landfill will not be a concern.

Air quality conditions will not be worse than during the operation phase and hence no adverse impact is anticipated.

4 Noise Impact

4.1 Introduction

This chapter presents the assessment of potential noise impacts which may arise during the construction, operation and restoration & aftercare stages of the NENT Landfill Extension. Noise impacts associated with the construction activities and the use of powered mechanical equipment during the construction, operation and restoration phases are all within the noise criteria. The implementation of good site practices as recommended will provide further protection of the sensitive receivers.

The noise impact assessment has been conducted in accordance with the requirements of Annex 5 and Annex 13 of the TM-EIAO as well as the requirements set out under Clause 3.4.2 of the EIA Study Brief.

4.2 Environmental Legislation, Standards and Guidelines

The relevant legislation and associated guidance notes applicable to the study for the assessment of noise implications include:

· Noise Control Ordinance (NCO), Cap 400;

· TM for the Assessment of Noise from Places other than Domestic Premises, Public Places or Construction Sites (TM-Places);

· Technical Memorandum on Noise from Construction Work other than Percussive Piling (TM-GW); and

· Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO).

4.2.1 Construction, Restoration & Aftercare Noise

Noise during construction, restoration and aftercare phases is governed by the Noise Control Ordinance (NCO) (Cap 400) and the EIAO. Guidelines concerning the assessment methodology and relevant criteria are provided in the relevant Technical Memoranda (TMs). These TMs prescribe the maximum permitted noise levels for the use of Powered Mechanical Equipment (PME) and certain construction activities and processes, according to the type of activity or equipment used, the perceived noise climate of the area, and the working hours of equipment operation and usage. The following TMs are applicable to the control of noise from construction and restoration activities:

· TM-GW; and

· TM-EIAO.

4.2.1.1 Daytime Noise Standards

Noise generated by general construction works during normal working hours (i.e. 0700 to 1900 hours on any day not being a Sunday or public holiday) is governed by TM-EIAO. The recommended noise standards are presented in Table 4.1.

Table 4.1: Daytime construction noise limit

Uses	Noise Standard (L_{eq, 30 min} dB(A))
Domestic Premises	75
Educational Institutions (normal periods)	70
Educational institutions (during examination periods)	65

Note: The standard above applies to uses which rely on open window for ventilation

4.2.1.2 Noise Standards for Restricted Hours

The NCO provides statutory controls on general construction works during the restricted hours (i.e. 1900 to 0700 hours from Monday to Saturday and any time on Sundays or public holidays). The use of PME for construction works during the restricted hours would require a CNP. The TM-GW details the procedures adopted by EPD for assessing such application. The granting of a CNP is subject to conditions stated in the permit and it may be revoked at any time for failure to comply with the permit conditions.

The study area does not fall within any designated area under the NCO, and construction noise criteria set out in the TM-GW should therefore be applicable to this NENT Landfill Extension Project.

Maximum allowable noise levels from construction activities during restricted hours at the affected NSRs are governed by the TMs and shall not exceed the specified Acceptable Noise Levels (ANLs). These ANLs are stipulated in accordance with the Area Sensitivity Ratings (ASR) established for the NSRs, and the Basic Noise Levels (BNLs) is stated in Table 4.2.

Table 4.2 : BNLs for construction noise other than percussive piling

Time Period	Basic Noise Levels for Area Sensitivity Ratings, dB(A)
Time Period	A	B	C
All weekdays during the evening (1900 to 2300 hours), and general holidays (including Sundays) during the day and evening (0700 to 2300 hours)	60	65	70
All days during the night-time (2300 to 0700 hours)	45	50	55

4.2.1.3 Construction Noise Permits

Despite any description or assessment made in this EIA Report on construction noise aspects, there is no guarantee that a CNP will be issued for the landfill construction. The Noise Control Authority will consider a well-justified CNP application, once filed, for construction works within restricted hours as guided by the relevant TMs issued under the NCO.

The Noise Control Authority will take into account contemporary conditions / situations of adjoining land uses and any previous complaints against construction activities at the site before making a decision in granting a CNP. Nothing in the EIA report shall bind the Noise Control Authority in making a decision. If a CNP is to be issued, the Noise Control Authority shall include in it any conditions demand. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

4.2.2 Operational Noise

4.2.2.1 Road Traffic Noise

The TM-EIAO provides guidance on acceptable road traffic noise levels for uses which rely on open windows for ventilation. The relevant criteria are shown in Table 4.3.

Table 4.3: Road traffic noise standards

Uses	Road Traffic Noise, L_{10, 1hr} dB(A)
Domestic Premises	70
Hotel and Hostels	70
Offices	70
Educational Institutions	65
Hospital & Clinics	55
Places of public worship and courts of law	65

Note: The above criteria apply to noise sensitive uses measured at 1m from external façade of premises which rely on open window for ventilation.

4.2.2.2 On-Site Operational Noise

On-site operational noise sources including fixed noise sources, such as ammonia stripping plant and leachate treatment plant, on-site traffic noise due to refuse vehicle movement and waste filling noise are controlled under the NCO and TM-Places. For planning purpose, the TM-EIAO has specified the following standards:

· 5 dB(A) below the appropriate ANLs in the TM-Places; or

· the prevailing background noise levels for quiet areas with ambient noise level at more than 5 dB(A) below the ANL.

The ANLs for different Area Sensitivity Ratings are summarised in Table 4.4 below.

Table 4.4: Operational noise criteria for fixed noise sources

Time Period	ANL, dB(A)			ANL-5, dB(A)
Time Period	ASR A	ASR B	ASR C	ASR A	ASR B	ASR C
Day (0700 to 1900 hours)	60	65	70	55	60	65
Evening (1900 to 2300 hours)	60	65	70	55	60	65
Night (2300 to 0700 hours)	50	55	60	45	50	55

A number of noise surveys were conducted at representative noise sensitive receivers (NSRs) in February 2005 and March 2006 to determine the prevailing noise levels. Results indicated that the daytime time noise levels were in the range of 44 to 71 dB(A), evening time noise levels were below 50 dB(A); and the nighttime noise levels were in the range of 39-49 dB(A). Other than SR1, SR2, SR3, SR5 & SR10, the background noise levels for daytime, evening & nighttime at the surveyed locations was generally lower than the relevant ANL. The prevailing background noise levels at these locations would therefore be adopted as the assessment criteria. Applicable daytime background noise levels at SR2, SR3 & SR5 and nighttime background noise level at SR1 & SR10 are the planning criteria of 55 dB(A) and 45 dB(A) respectively. A summary of the prevailing noise levels at the NSRs and the noise criteria for operation noise is given in Table 4.5.

Table 4.5: Summary of noise criteria for operational noise

NSR	Time Period ^[1]	Prevailing Noise Level, dB(A) (1)	Area Sensitivity Rating	ANL-5 dB(A) (2)	Criteria dB(A) Min. of (1) & (2)
SR1	Day	51	A	55	51
	Evening	47	A	55	47
	Night	46	A	45	45
SR2	Day	57	A	55	55
	Evening	42	A	55	42
	Night	41	A	45	41
SR3	Day	63	A	55	55
	Evening	40	A	55	40
	Night	39	A	45	39
SR4	Day	53	A	55	53
	Evening	50	A	55	50
	Night	45	A	45	45
SR5	Day	71	A	55	55
	Evening	43	A	55	43
	Night	42	A	45	42
SR6	Day	43	A	55	43
	Evening	42	A	55	42
	Night	40	A	45	40
SR7	Day	52	A	55	52
	Evening	48	A	55	48
	Night	44	A	45	44
SR8	Day	44	A	55	44
	Evening	42	A	55	42
	Night	41	A	45	41
SR9	Day	44	A	55	44
	Evening	40	A	55	40
	Night	39	A	45	39
SR10	Day	53	A	55	53
	Evening	49	A	55	49
	Night	49	A	45	45

Note:

^[1] Day: 0700 to 1900 hours, Evening: 1900 to 2300 hours, Night: 2300 to 0700 hours

4.3 Description of the Environment

4.3.1 Baseline Condition

The NENT Landfill Extension site is located to the southeast of the existing NENT Landfill, which is at the northern part of the New Territories near Ta Kwu Ling. An ambient noise survey was conducted in March 2006 to obtain the existing noise profile of the surrounding environment. All the noise measurements were conducted in accordance with TM-Places. The measured noise levels at the selected locations ranged from 39 to 71 L_{eq, 30-min} dB(A). A summary of the measured noise levels at each sensitive receiver location is given in Table 4.6.

No audible plant operation noise from the existing NENT Landfill was perceived or recorded at the measuring locations during the noise survey.

Table 4.6: Prevailing noise levels

NSR	Description	Prevailing Noise Levels, dB(A) L_{Aeq, 30 min}			Remarks
NSR	Description	Day	Evening	Night	Remarks
SR1	Wo Keng Shan Tsuen	51	47	46	Insect, traffic noise
SR2	Village houses at Junction of Ng Chow Road and Wo Keng Shan Road	57	42	41	Traffic, Bird, Insect noise
SR3	Cheung Shan Monastery	63	40	39	Traffic, Bird, Insect noise
SR4	Miu Keng	53	50	45	Insect noise
SR5	Wing Fai Yuen	71	43	42	Insect noise
SR6	Heung Yuen Wai	43	42	40	Insect noise
SR7	Tsung Yuen Ha	52	48	44	Insect, bird noise
SR8	Ha Heung Yuen	44	42	41	Insect, bird noise
SR9	Lin Ma Hang	44	40	39	Insect, bird noise
SR10	Tung Lo Hang	53	49	49	Insect, Pig noise

Note:

^[1] Day: 0700 to 1900 hours, Evening: 1900 to 2300 hours, Night: 2300 to 0700 hours

^[2] Prevailing noise levels include +3dB(A) façade effect

Weekly plant noise monitoring for the existing NENT Landfill has been conducted by the contractor of the existing NENT Landfill since 1996. A brief summary of the findings at the noise monitoring locations are listed in Table 4.7. Based on the statistical records, there is no justified exceedance from the NENT Landfill operation.

Table 4.7: Summary of noise monitoring locations and exceedance incidents

Monitoring Location	No. of Exceedance incidents	Date	Reasons
NSR1 Wo Keng Shan	1	13 October 1996 Exceed 1.9dB(A)	Measurements were taken near an operating air sampling unit and under strong wind condition. Therefore, the abnormality was not justified as non-compliance.
NSR2 Ha Heung Yuen	0	N/A	N/A
NSR3 Tung Lo Hang	0	N/A	N/A
NSR4 Ping Yeung	1	14 June 1998 Exceed 5dB(A)	Measured noise level was influenced by firecracker burning in the village. Therefore the abnormality was not justified as non-compliance.

4.4 Noise Sensitive Receivers

Noise sensitive receivers (NSRs) were identified in accordance with Annex 13 of the TM-EIAO. Both existing and planned uses during the construction, operation, restoration and aftercare periods of the NENT Landfill Extension are included as appropriate. The existing NSRs were identified through desktop review and site survey. There were no planned NSRs on the latest Outline Zoning Plan.

The land uses in the vicinity of the extension site include temple and residential developments. The key representative NSRs for noise assessment are given in Table 4.8 and their respective locations are shown in Drawing No. 24315/13/201.

Table 4.8: Representative noise sensitive receivers (NSRs)

NSR No.	NSR Description	Use	No. of Storey (including roof)	Shortest Horizontal Distance to NENT Landfill Extension Site Boundary, m
SR1	Wo Keng Shan Tsuen	Residential	3	420
SR2	Village houses at Junction of Ng Chow Road and Wo Keng Shan Road	Residential	3	1040
SR3	Cheung Shan Monastery	Religious	1	820
SR4	Miu Keng	Residential	3	990
SR5	Wing Fai Yuen	Residential	2	980
SR6	Heung Yuen Wai	Residential	3	1240
SR7	Tsung Yuen Ha	Residential	3	1790
SR8	Ha Heung Yuen	Residential	3	1330
SR9	Lin Ma Hang	Residential	3	900
SR10	Tung Lo Hang	Pig Farm / Residential	2	800

　　　　　　4.5 Assessment Methodologies

4.5.1 Construction, Restoration and Aftercare Noise

Construction, restoration and aftercare noise impacts have been assessed by adopting the standard acoustic principles and the methodologies described in the relevant TMs issued under the NCO, primarily the TM-GW. The following general procedures were applied to the construction, restoration and aftercare noise assessment.

· Determine the assessment area;

· Identify and locate representative NSRs that may be affected by the works;

· Obtain the methodology and work sequence for the construction period;

· Obtain the plant items for each corresponding work sequence;

· Determine the sound power levels (SWLs) of the plant items according to the information stated in the TM-GW or other recognised sources of reference;

· Calculate the correction factors based on the distance between the NSRs and the notional noise source positions of the work sites;

· Apply corrections for façade, distance, barrier attenuation, acoustic reflection where applicable. For assessment of NSRs exceeding 300m, atmospheric and ground corrections will be applied with reference to ISO 9613;

· Assess the construction and restoration works noise impacts;

· Predict noise levels at the NSRs;

· Quantify the level of impact at the NSRs in accordance with TM-GW; and

· Predict the cumulative noise impacts for activities associated with the construction phasing and restoration works at the existing landfill.

4.5.2 Road Traffic Noise

Road traffic noise calculation method is based on the UK Department of Transport “Calculation of road Traffic Noise (CRTN)”. The predicted noise levels at the sensitive receivers include 2.5dB(A) facade reflection and correction factors for effects due to gradient, distance, view angle, road surface and barriers.

The CRTN compliance computer programme, RoadNoise 2000, has been used to model traffic noise on the road networks. Road traffic noise levels are presented in terms of noise levels exceeded for 10% of the one-hour period during the peak traffic flow, i.e. L_10,1hr dB(A). Traffic noise levels at the NSRs for scenarios with and without the NENT Landfill Extension are predicted.

4.5.3 On-site Operational Noise

Major sources of operational noise are generated from the aeration lagoon of leachate treatment plant, ammonia stripping plant, refuse vehicle movement and waste filling. The sound power levels of these activities / facilities were measured at the existing NENT Landfill. The following general procedures will apply to the operational noise assessment.

· Determine the assessment area;

· Identify and locate representative NSRs that may be affected by the works;

· Obtain the plant items;

· Determine the sound power levels (SWLs) of the plant for fixed noise sources and the vehicular movement SWLs on the haul roads in accordance with BS5228;

· Calculate the correction factors based on the distance between the NSRs and the noise source positions;

· Predict fixed source noise levels at the NSRs; and

· Quantify the level of impact at the NSRs in accordance with TM-Places.

4.6 Construction, Restoration & Aftercare Noise Impact Assessment

4.6.1 Construction Plant Inventory

Sections 2.7 present a detailed description of the key construction activities at each phase of the NENT Landfill Extension. The construction of the landfill extension would include the following activities:

· Site clearance & formation;

· Installation of liner;

· Construction of leachate treatment facilities;

· Construction of ammonia stripping plant;

· Cumulative construction noise impact for construction activities associated with the construction/operation in the extension and restoration in the existing landfill; and

· Restoration & Aftercare

The above construction activities will involve the use of Powered Mechanical Equipment (PME) including excavators, truck, crane truck, compactor, dozer, generator, loader, etc. Their respective Sound Power Levels (SWLs) are given in Appendix 4.1.

The plant inventory provided in Appendix 4.2 indicates the total number of PME for each construction activity. Prediction is made with respect to the distance of NSRs from the notional source locations. Appendix 4.3 shows the locations of the NSRs and their respective distances from the notional sources.

4.6.2 Prediction and Evaluation of Noise Impact

Assessment results indicate that, under “unmitigated” scenario, the construction noise levels at the NSRs are within the criteria. The maximum unmitigated construction noise levels against the stipulated criteria at the NSRs are shown in Table 4.9. Detailed results of the construction noise assessment are given in Appendix 4.4.

Table 4.9: Predicted maximum construction noise levels at the NSRs – “unmitigated” scenario

NSR No.	NSR Description	Max Predicted Noise Level, dB(A)	Criteria	Compliance (Y/N)
SR1	Wo Keng Shan Tsuen	69	75	Y
SR2	Village houses at Junction of Ng Chow Road and Wo Keng Shan Road	57	75	Y
SR3	Cheung Shan Monastery	58	75	Y
SR4	Miu Keng	63	75	Y
SR5	Wing Fai Yuen	57	75	Y
SR6	Heung Yuen Wai	53	75	Y
SR7	Tsung Yuen Ha	60	75	Y
SR8	Ha Heung Yuen	53	75	Y
SR9	Lin Ma Hang	67	75	Y
SR10	Tung Lo Hang	66	75	Y

4.6.3 Precautionary Measures

4.6.3.1 Construction, Restoration & Aftercare Phase

The assessment results have demonstrated that daytime noise criteria would not be exceeded by the predicted construction noise levels under the unmitigated scenario. Good practices for the control of noise emissions from construction sites are still recommended to further eliminate the potential of noise impact. These include:

· Good site practices to limit noise emissions at source;

· Use of quiet plant and working methods, whenever practicable.

The above precautionary measures should be implemented in all work sites as good practices. Detailed descriptions of these precautionary measures are given in the following sections.

4.6.3.2 Good Site Practices and Noise Management Techniques

Good site practice and noise management techniques could considerably reduce the noise impact from construction site activities on nearby NSRs. The following precautionary measures should be followed during each phase of construction:

· Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction programme;

· Machines and plant (such as trucks, cranes) that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;

· Plant known to emit noise strongly in one direction, where possible, be orientated so that the noise is directed away from nearby NSRs;

· Silencers or mufflers on construction equipment should be properly fitted and maintained during the construction works;

· Mobile plant should be sited as far away from NSRs as possible and practicable; and

· Material stockpiles, site office and other structures should be effectively utilised, where practicable, to screen noise from on-site construction activities.

The above good practice to further eliminate the potential of noise impact from construction equipment will be incorporated into the contract specification. The benefits of these techniques can vary according to specific site conditions and operations. The environmental noise climate would certainly be improved through these control practices, although the improvement can only be quantified during implementation when specific site parameters are known.

4.6.3.3 Use of “Quiet” Plant and Working Methods

The use of quiet plant is a feasible solution to promote better noise impact management of the work activities. It is generally known (supported by field measurement) that particular models of construction equipment are quieter than standard types given in the TM-GW. Whilst it is generally considered too restrictive to specify that the DBO Contractor has to use specific models or items of plant, it is reasonable and practicable to set plant noise performance specifications for specific PME so that some flexibility in selection of plant is allowed. A pragmatic approach would be to request that the DBO Contractor independently verifies the noise level of the plant proposed to be used and demonstrates through furnishing of these results, that the plant proposed to be used on the site meets the requirements.

The use of quiet plant associated with the construction works is prescribed in British Standard “Noise Control on Construction and Open Sites, BS5228: Part 1: 1997” which contains the SWLs for specific quiet PME. It should be noted that while various types of silenced equipment could be found in Hong Kong, EPD when processing a CNP application for evening or night time works may choose to apply the noise data stipulated in the TM-GW as appropriate. CNP applications which contain sufficient details of any particularly quiet items of PME or any special noise control measures which the CNP applicant proposes to employ on the site may be given special consideration by the Noise Control Authority.

Routine noise monitoring will be stipulated in the EM&A requirement to counter check the noise performance at NSR, and the preference for adopting quiet plant will be stipulated when the noise impact from construction activities exceed the limit level.

4.6.4 Daytime Cumulative Construction Noise Impacts from Construction in Landfill Extension and Restoration in Existing Landfill

Overlap between Phases 1 & 2 construction activities of the landfill extension and leachate treatment facilities and restoration works at the existing landfill will occur. Construction activities at the landfill extension site would involve the use of PME such as excavator, compactor, generators, loader, crane truck, dump truck, etc. Restoration works at the existing landfill would involve the laying of a gas venting layer, an impermeable mineral layer, a drainage layer and top soil on the top of the waste body.

A sound power level of 127 dB(A) at the notional source position of the existing landfill site was assumed for the assessment of cumulative construction noise impact for the landfill extension, in reference to the estimated type and number of plant for the restoration works. The predicted cumulative noise levels at the NSRs are summarised in Table 4.10 below and detailed calculations are shown in Appendix 4.5. Results show that the predicted cumulative noise levels are within the noise criteria and residual impact is not anticipated.

Table 4.10: Cumulative construction noise impacts from existing landfill

NSR No.	Notional Distance to Existing Landfill, m	Predicted Noise Level, dB(A)			Noise Criteria	Compliance (Y/N)
NSR No.	Notional Distance to Existing Landfill, m	NENT Landfill Extension	Existing NENT Landfill	Cumulative	Noise Criteria	Compliance (Y/N)
SR1	707	64	55	65	75	Y
SR2	1326	57	55	59	75	Y
SR3	1624	58	48	58	75	Y
SR4	2182	63	45	63	75	Y
SR5	1927	57	46	57	75	Y
SR6	623	53	66	66	75	Y
SR7	995	57	62	63	75	Y
SR8	641	53	66	66	75	Y
SR9	975	67	52	67	75	Y
SR10	239	63	74	75	75	Y

4.7 Operational Noise Impact Assessment

4.7.1 Road Traffic Noise Impact Assessment

4.7.1.1 Prediction of Road Traffic Noise Levels

Road traffic noise levels associated with the NENT Landfill Extension are predicted based on the traffic data forecast. The number of vehicle trips increases gradually from 2005 to 2012 and the traffic volume will have reached the maximum level at Year 2012 due to natural waste growth. After 2012, there will be a decrease in waste as well as vehicle trips due to the change in waste catchment distribution with some wastes being diverted to other landfill sites. In 2013 when the South East Kowloon Refuse Transfer Station (SEKRTS) commissioned, wastes from the East Kowloon will be diverted to WENT landfill through SEKRTS.

Wo Keng Shan Road is an access road for refuse vehicles to the NENT Landfill. Besides refuse vehicles, other vehicular type traffic volume along this road is expected to be low. A conservative estimate of 5 light vehicles (i.e. private car or taxi) per hour is assumed. The traffic data adopted for assessment of the “with” and “without” Project scenarios are summarized in Table 4.11.

Table 4.11: Peak Traffic flow data at Wo Keng Shan Road

	Without the Project	With the Project Peak traffic flow at Year 2012
No. of Refuse Vehicle / hour	0	90
No. of Light Vehicle per hour	5	5
Total No. of Vehicle / hour	5	95
Percentage of Heavy Vehicle	0%	95%
Speed, kph	50	50

The predicted facade noise levels at the existing NSRs are presented in Table 4.12. Roadplot and output files are shown in Appendix 4.6. As SR6 to SR10 are more than 700m away from Wo Keng Shan Road and are sufficiently screened by natural topography, the road traffic noise impact would be insignificant. In addition, a visual screen planter should be erected near the Cheung Shan Monastery by the DBO Contractor during construction phase. The extent of the planter is shown in Drawing No. 24315/13/202. Results indicate that all NSRs will be in compliance with the noise criteria of 70dB(A) L₁₀.

Table 4.12: Predicted maximum traffic noise levels at NSRs – “unmitigated” scenario

NSR No.	NSR Description	Noise Criteria	Predicted Noise Level, L₁₀ dB(A) (without the Project)	Predicted Noise Level, L₁₀ dB(A) (with the Project)	Contribution from the Project (Exceedance)
SR1	Wo Keng Shan Tsuen	70	<40	46	>1.0 dB(A) Exceedance: 0
SR2	Village houses at Junction of Ng Chow Road and Wo Keng Shan Road	70	<40	59	>1.0 dB(A) Exceedance: 0
SR3	Cheung Shan Monastery	65	46	65	>1.0 dB(A) Exceedance: 0
SR4	Miu Keng	70	<40	56	>1.0 dB(A) Exceedance: 0
SR5	Wing Fai Yuen	70	47	70	>1.0 dB(A) Exceedance: 0

4.7.2 On-site Operational Noise Impact Assessment

4.7.2.1 Identification of Noise Sources

The major on-site noise sources during operation of the Project will be the aeration process in the lagoon of the leachate treatment plant, the operation of the ammonia stripping plant, refuse vehicle movement and waste filling. For the waste filing operation, all PMEs will operate at the bottom of valley during the early stage of tipping operation. Natural topography will provide sufficient screening effect for all NSRs. The worst-case scenario will only be occurred at the later stage when the bottom part of the valley is filled up. When there is a direct line of sight of the tipping face, the natural topography cannot provide sufficient screening for NSR and noise exceedance will be encountered. The worst-affect period will be occurred during the daily cover operation when relatively large-scale compression is required.

These noise emission inventories of the landfill site operation are summarized in Table 4.13. The locations of the noise sources are shown in Drawing No. 24315/13/203.

Table 4.13: Noise inventories for the landfill site operation

Description	Qty	SWL, dB(A) / unit	Subtotal SWL, dB(A)	Operation period^[4]
Leachate treatment plant	1	75^[1]	75	Daytime, Evening & Nighttime
Ammonia stripping plant	1	88^[2]	88	Daytime, Evening & Nighttime
Refuse vehicle / hour	90	97^[3]	117	Daytime
Waste filling
Compactor (CNP050)	2	105
Dump truck, e.g.5.5 tonne < gross vehicle weight≤38 tonne, (CNP068)	1	105
Dozer (CNP030)	2	115
Backhoe (CNP081)	1	112	119

Note:

^[1]Measurement details are shown in Appendix 4.7

^[2] Measurement details are shown in Appendix 4.8

^[3] Measurement details are shown in Appendix 4.9

^[4] Daytime (0700 to 1900), Evening (1900 to 2300) and Night time (2300 to 0700)

The use of quieter equipment/plant is a feasible solution to promote better noise impact management of the work activities. It is generally known (supported by field measurement) that particular models of powered mechanical equipment are quieter than standard types given in the TM-GW. Whilst it is generally considered too restrictive to specify that the DBO Contractor have to use specific models or items of equipment/plant, it is reasonable and practicable to set noise performance specifications for specific equipment/plant so that flexibility in selection of equipment is allowed. A pragmatic approach would be to request that the DBO Contractor independently verifies the noise level of the equipment/plant to be used and demonstrates through furnishing of these results, that the equipment/plant to be used on the site meets the requirements. The preference for adopting quieter equipment/plant will be stipulated in the contract specification. It shall be applied whenever practicable to further eliminate the potential of noise impact from construction activities.

4.7.2.2 Prediction of Noise Levels from Operational Noise

Assessment results indicate that under “unmitigated” scenario, the operational noise impact will comply with the noise criteria during early stage of tipping/daily covering when the topography screening effect is adequate (Table 4.14a). For the later stage of tipping/daily covering when the topography is insufficient to screen the noise impact, there are two NSRs exceeding the daytime criteria (Table 4.14b). Exceedance of noise criteria was predicted at SR1 and SR9 when plants are mobilized for daily covering operation at the later stage of landfill life.

The predicted evening & nighttime noise levels will comply with the evening and night time noise criteria at all NSRs during the entire landfill operating period (Table 4.15). Detailed calculations for operational noise under the un-mitigated scenario are shown in Appendix 4.10.

Table 4.14a: Predicted daytime facade noise levels without mitigation measures during the early stage of tipping/daily covering when the effect of topography screening is adequate

NSR ID	Predicted facade Noise Levels, (Leq, 30min dB(A))				CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
NSR ID	Leachate Treatment Plant	Ammonia stripping plant	On-site refuse vehicle movement	Waste filling	CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
SR1	<15	26	45	48	50	51	Y
SR2	<10	16	27	40	40	55	Y
SR3	<10	<15	26	41	41	55	Y
SR4	<10	<10	24	38	38	53	Y
SR5	<10	<10	24	39	39	55	Y
SR6	<10	<15	21	38	38	43	Y
SR7	<10	<10	17	34	34	52	Y
SR8	<10	<15	21	37	37	44	Y
SR9	<10	<10	28	43	43	44	Y
SR10	<10	19	27	43	43	53	Y

Table 4.14b: Predicted daytime facade noise levels without mitigation measures during the later stage of tipping/daily covering when the effect of topography screening is inadequate

NSR ID	Predicted facade Noise Levels, (Leq, 30min dB(A))				CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
NSR ID	Leachate Treatment Plant	Ammonia stripping plant	On-site refuse vehicle movement	Waste filling	CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
SR1	<15	26	45	53	53	51	N
SR2	<10	16	27	40	40	55	Y
SR3	<10	<15	26	41	41	55	Y
SR4	<10	<10	24	38	38	53	Y
SR5	<10	<10	24	39	39	55	Y
SR6	<10	<15	21	38	38	43	Y
SR7	<10	<10	17	34	34	52	Y
SR8	<10	<15	21	37	37	44	Y
SR9	<10	<10	28	48	48	44	N
SR10	<10	19	27	43	43	53	Y

Table 4.15: Predicted evening/nighttime facade noise levels without mitigation measures

NSR ID	Predicted facade Noise Levels, (Leq, 30min dB(A))		CNL, Leq (30min) dB(A)	Criteria (Evening / Nighttime)	Compliance (Y/N)
NSR ID	Leachate Treatment Plant	Ammonia stripping plant	CNL, Leq (30min) dB(A)	Criteria (Evening / Nighttime)	Compliance (Y/N)
SR1	<15	26	26	47 / 45	Y
SR2	<10	16	17	42 / 41	Y
SR3	<10	<15	16	40 / 39	Y
SR4	<10	<10	<15	50 / 45	Y
SR5	<10	<10	<15	43 / 42	Y
SR6	<10	<15	16	42 / 40	Y
SR7	<10	<10	<15	48 / 44	Y
SR8	<10	<15	16	42 / 41	Y
SR9	<10	<10	<15	40 / 39	Y
SR10	<10	19	20	49 / 45	Y

4.7.3 Mitigation Measures

Assessment results indicate that the exceedance of noise criteria at SR1 & SR9 are caused by the daily covering activities involving the use of PMEs during the later stage of the landfill operation when the effect of topography screening is inadequate. Noise mitigation measures are therefore required to alleviate the noise impacts at that stage of the landfill development. Noise emissions from the entire site could be minimised by use of quiet plant and working methods.

Routine noise monitoring will be stipulated in the EM&A programme to monitor the noise performance at NSRs, and quiet plant shall be used when the noise impact from operational activities exceed the trigger level. The type of quiet plant shall be proposed by the DBO Contractor and verified by the IEC.

The mitigation measures would need to be implemented in all work sites as good practices. Detailed descriptions of these mitigation measures are given in the following sections.

4.7.3.1 Use of “Quiet” Plant and Working Methods

British Standard “Noise Control on Construction and Open Sites, BS5228: Part 1: 1997” contains the SWLs for specific quiet PME. The SWL for quiet PME adopted for the assessment are detailed in Table 4.16.

Table 4.16: Sound power levels of quiet plant

Equipment	BS5228 Part 1 Identification	Sound Power Level, dB(A)
Dozer	BS Table C9 Ref 2	104

4.7.3.2 Assessment Results for “Mitigated” Scenario

Noise reduction from the use of quiet dozer during waste filling/daily cover operation in the operation phase has been applied in the assessment. Detailed results of operational noise assessment for “mitigated” scenario are given in Appendix 4.11. The predicted noise levels over daytime noise criteria are summarised in the following Table 4.17.

Table 4.17: Predicted facade noise levels with mitigation measures at NSRs

NSR ID	Predicted facade Noise Levels, (Leq, 30min dB(A))				CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
NSR ID	Leachate Treatment Plant	Ammonia stripping plant	On-site refuse vehicle movement	Waste filling	CNL, Leq (30min) dB(A)	Criteria	Compliance (Y/N)
SR1	<15	26	45	48	50	51	Y
SR2	<10	16	27	41	41	55	Y
SR3	<10	<15	26	37	37	55	Y
SR4	<10	<10	24	38	38	53	Y
SR5	<10	<10	24	40	40	55	Y
SR6	<10	<15	21	34	34	43	Y
SR7	<10	<10	17	34	34	52	Y
SR8	<10	<15	21	33	33	44	Y
SR9	<10	<10	28	43	43	44	Y
SR10	<10	19	27	43	43	53	Y

4.7.4 Cumulative Operational Noise Impacts from Concurrent Projects

Cumulative operational noise sources of the Project include aeration lagoon of leachate treatment plant, ammonia stripping plant and flare station at the existing landfill. The cumulative noise levels at NSRs are summarised in Table 4.18 to 4.19 below. Detailed calculations are given in Appendix 4.12. Results show that the predicted cumulative noise levels are within the noise criteria and residual impact is not anticipated.

Table 4.18: Cumulative operational noise impacts from existing landfill (Daytime)

NSR No.	Predicted Noise Level, dB(A)			Noise Criteria	Compliance (Y/N)
NSR No.	The Project	Existing Landfill	Cumulative	Noise Criteria	Compliance (Y/N)
SR1	50	31	50	51	Y
SR2	41	25	41	55	Y
SR3	37	22	37	55	Y
SR4	38	18	38	53	Y
SR5	40	19	40	55	Y
SR6	34	25	34	43	Y
SR7	34	31	36	52	Y
SR8	33	33	36	44	Y
SR9	43	13	43	44	Y
SR10	43	39	45	53	Y

Table 4.19: Cumulative operational noise impacts from existing landfill (Evening and Nighttime)

NSR No.	Predicted Noise Level, dB(A)			Criteria (Evening / Nighttime)	Compliance (Y/N)
NSR No.	The Project	Existing Landfill	Cumulative	Criteria (Evening / Nighttime)	Compliance (Y/N)
SR1	26	31	32	47 / 45	Y
SR2	17	25	26	42 / 41	Y
SR3	16	22	23	40 / 39	Y
SR4	<15	18	20	50 / 45	Y
SR5	<15	19	20	43 / 42	Y
SR6	16	25	26	42 / 40	Y
SR7	<15	31	31	48 / 44	Y
SR8	16	33	33	42 / 41	Y
SR9	<15	13	17	40 / 39	Y
SR10	20	39	39	49 / 45	Y

4.8 Residual Environmental Impact

Construction noise impact is predicted to be within the noise criterion. At the later stage of landfill operation, operational noise from the landfill activities will adopt quiet plant working method to control noise impact to within the criteria. Refuse vehicle traffic along Wo Keng Shan Road will comply with the traffic noise criterion. Residual noise impact is therefore not anticipated.

4.9 Conclusion

Potential noise sources and representative NSRs for the construction and operation phases have been identified. Noise prediction has been conducted to assess the impact with reference to established methodologies.

4.9.1 Construction and Restoration Phase

The assessment has been conducted based on daytime noise criteria specified in the TM-EIAO. It is predicted that the construction noise impacts associated with the construction activities on the Project site would not exceed the criteria. No adverse construction noise impact is anticipated.

4.9.2 Operation Phase

4.9.2.1 Road Traffic noise Impact

Road traffic noise at Wo Keng Shan Road has been assessed to be insignificant. Noise assessment results indicate that road traffic noise levels will comply with the noise criterion. Residual road traffic noise impact is therefore not anticipated.

4.9.2.2 On-site Operational Noise Impact

Assessment results also indicate that under “unmitigated” scenario, the operational noise impact will comply with the noise criteria during early stage of tipping when the topography screening effect is adequate. At the later stage of tipping when the topography is insufficient to screen the noise impact, assessment results indicate that the predicted noise levels at 2 sensitive receivers (SR1 & SR9) will exceed the noise criterion. With the adoption of quiet plants, operational fixed noise impacts will be controlled to within the noise criterion.

5 Water Quality Impact

5.1 Introduction

This chapter presents the assessment of potential water quality impacts, which may arise during the construction, operation, restoration and aftercare of the Project. Mitigation measures have been proposed to alleviate the potential water quality impact. The residual water quality impact was assessed to be acceptable.

T he water quality impact assessment has been conducted in accordance with Annexes 6 and 14 of the TM-EIAO and the EIA Study Brief for the Project.

5.2 Environmental Legislation, Standards and Guidelines

The following relevant legislation and associated guidelines are applicable to the evaluation of water quality impacts associated with the construction, operation, restoration and aftercare of the Project:

· Environmental Impact Assessment Ordinance (Cap.499, S.16), Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO), Annex 6 and 14;

· Water Pollution Control Ordinance (WPCO, Cap 358);

· Technical Memorandum on Standards for Effluent Discharged into Drainage and Sewerage System, Inland and Coastal Waters (WPCO, Cap. 358, S.21);

· Hong Kong Planning Standards and Guidelines (HKPSG);

· Practice Note for Professional Persons (ProPECC), Construction Site Drainage (PN1/94)

The Water Pollution Control Ordinance (WPCO, Cap 358) provides the major statutory framework for the protection and control of water quality in Hong Kong. According to the Ordinance and its subsidiary legislation, the entire Hong Kong waters are divided into ten Water Control Zones (WCZs) and four supplementary WCZs. The existing NENT Landfill at Ta Kwu Ling and the proposed site for NENT Landfill Extension lie within Ganges Subzone of Deep Bay WCZ and the Water Sensitive Receivers which may be affected by the Project works are located within the same subzone. Table 5.1 shows the Water Quality Objectives (WQO) for Ganges Subzone of Deep Bay WCZ.

Table 5.1: Water Quality Objectives for Ganges Subzone of Deep Bay WCZ

Parameter	Water Quality Objectives for Ganges Subzone of Deep Bay WCZ
Aesthetic Appearance	(a) Waste discharges shall cause no objectionable odours or discolouration of the water. (b) Tarry residues, floating wood, articles made of glass, plastic, rubber or of any other substances should be absent. (c) Mineral oil should not be visible on the surface. Surfactants should not give rise to a lasting foam. (d) There should be no recognisable sewage-derived debris. (e) Floating, submerged and semi-submerged objects of a size likely to interfere with the free movement of vessels, or cause damage to vessels, should be absent. (f) Waste discharges shall not cause the water to contain substances which settle to form objectionable deposits.
Bacteria	The level of Escherichia coli should be zero per 100ml, calculated as the running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days.
Colour	Waste discharges shall not cause the colour of water to exceed 30 Hazen units.
pH	Waste discharges shall not cause the pH of the water to exceed the range of 6.5-8.5 units.
Temperature	Waste discharges shall not cause the natural daily temperature range to change by more than 2.0 degrees Celsius.
SS	Waste discharges shall not cause the annual median of suspended solids to exceed 20 mg/L.
DO	Waste discharges shall not cause the level of dissolved oxygen to be less than 4 mg/L
BOD₅	Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 3 mg/L.
COD	Waste discharges shall not cause the chemical oxygen demand to exceed 15 mg/L
NH₃-N	The un-ionized ammoniacal nitrogen level should not be more than 0.021mg/L, calculated as the annual average (arithmetic mean).
Toxins	(a) Waste discharges shall not cause the toxins in water to attain such levels as to produce significant toxic carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to toxicant interactions with each other. (b) Waste discharge shall not cause a risk to any beneficial uses of the aquatic environment.

5.3 Baseline Conditions

5.3.1 Groundwater Condition

5.3.1.1 Groundwater Condition at Existing NENT Landfill

Regular groundwater monitoring along the boundary of the landfill site has been conducted since the commencement of the existing NENT Landfill in June 1995. The groundwater sampling locations are presented in Drawing no. 24315/13/301. Groundwater monitoring data presented in NENT Landfill’s monthly reports showed that the results were in compliance with the specified trigger levels except at several occasions of abnormal observations of COD in 1996 and 1997. After detailed assessment by the Independent Consultant, it was concluded that the causes were not originated from landfill leachate.

Groundwater monitoring data from January 2005 to March 2006 are summarised in Appendix 5.1.

5.3.1.2 Groundwater Condition at NENT Landfill Extension Site

The water quality monitoring data for groundwater has been included in Appendix 5.1. It is observed that there is no contamination of leachate to the groundwater during the operation life of the existing landfill. The current engineering design of leachate management system is proven to be effective and the water quality monitoring data measured in the past 10 year were all within the compliance criteria.

Groundwater samplings have been conducted for a period of 7-days on the NENT Landfill Extension site. Drawing No. 24315/13/302 shows the locations of the boreholes, and Table 5.2 summarises the results of groundwater monitoring.

Table 5.2: Summary of groundwater monitoring results

Borehole No.	Ground Level (mPD)	Groundwater Level (mPD)	Groundwater Depth from Ground (m)
BH1	51.19	50.12	1.07
BH2	135.06	128.48	6.58
BH3	146.98	141.22	5.76
BH4	144.65	137.22	7.43
BH5	106.21	---	Dry
BH6	151.20	---	Dry
BH7	154.10	146.87	7.23
BH8	119.60	109.04	10.56
BH9	194.88	---	Dry
BH10	198.02	---	Dry
BH11	214.63	193.75	20.88
BH12	211.69	199.66	12.03
BH13	187.31	172.28	15.03
BH14	119.76	---	Dry
BH15	115.60	112.93	2.67
BH16	143.05	128.70	14.35
BH17	141.75	135.30	6.45
BH18	189.23	165.18	24.05
BH19	191.28	183.78	7.50
BH20	183.69	159.38	24.31
BH21	172.51	161.36	11.15
BH22	139.32	123.91	15.41
BH23	98.02	---	Dry
BH24	143.46	138.67	4.79
BH25	207.62	---	Dry
BH26	62.20	---	Dry
BH27	62.58	50.6	11.98
ABH1	73.74	59.52	14.22
ABH2	48.85	47.17	1.68
ABH3	63.99	52.04	11.95
ABH4	64.78	60.50	4.28
ABH5	83.60	79.00	4.60
ABH6	121.99	106.25	15.74
ABH7	123.59	116.34	7.25
ABH8	137.26	111.61	25.65
ABH9	171.63	139.48	32.15
ABH10	72.96	71.57	1.39
ABH11	97.47	90.26	7.21
ABH12	99.99	97.28	2.71
ABH13	127.78	111.17	16.61
ABH14	150.93	134.98	15.95
ABH15	189.75	162.20	27.55

From the above groundwater monitoring data and the spatial distribution of the borehole locations, it could be observed that all groundwater flows within the site are directed towards the Ping Yuen River Catchment and will not fall into the Lin Ma Hang Stream Catchment.

5.3.2 River Water and Sediment Quality

5.3.2.1 River Water Quality

At present, the routine monitoring programme conducted by EPD provides the most comprehensive spatial and temporal river water quality data, and these data may be used to represent the baseline water quality condition of the concerned water system. The nearest EPD water quality monitoring sampling point located around the existing NENT Landfill is “GR3” on a tributary of Ping Yuen River. The river water quality monitoring results, as extracted from the “Annual River Water Quality Reports” published by EPD, are summarised in Table 5.3.

Table 5.3: Summary of monthly water quality monitoring results at upper stream of Ping Yuen River (GR3)

Year	Annual Average Concentration
Year	DO (mg/L)	pH	Conduct-ivity (μS/cm)	TSS (mg/L)	BOD₅ (mg/L)	COD (mg/L)	E. coli * (cfu/100ml)	NH₃-N (mg/L)	TOC (mg/L)
1998	7.8	7.3	191.2	199.8	5.6	12.6	1,070	0.1	6.4
1999	8.0	7.3	197.7	52.8	6.3	15.5	5,360	0.2	4.8
2000	7.6	7.0	188.8	41.4	3.5	10.9	5,870	0.2	3.3
2001	7.7	6.9	153.0	11.0	2.8	7.3	5,960	0.1	2.2
2002	6.3	7.1	172.0	38.7	5.6	9.8	1,840	0.2	3.3
2003	7.4	7.0	149.1	11.7	2.8	5.9	910	0.2	2.3
2004	7.3	7.0	141.8	11.2	4.9	7.9	840	0.1	2.3
2005	7.7	7.1	143.3	48.0	1.5	6.7	2,610	0.1	2.5
Max. Value	10.9	7.6	401	1200	20	110	410000	0.54	33
Min. Value	4.3	6.5	93	2.1	1	2	10	0.016	1
Std. Dev	1.21	0.25	49.8	177	4.20	13.2	63600	0.10	4.14

* - Geometric mean value

EPD’s Annual River Water Quality Reports showed that the Water Quality Indexes (WQI) at GR3 from 1998 to 2004 were either “Good” or “Excellent”, the mean E. coli concentration at GR3 in 2004 was 840 cfu/100mL.

EPD’s monitoring data suggested that there was no sign of river water contamination at upstream of Ping Yuen River by any leachate leaking from the existing NENT Landfill, given the low concentrations of NH₃-N and COD.

A stream water quality survey was conducted in early 2006 by Arup to obtain baseline condition of the streams in the vicinity of the existing NENT Landfill and to identify if there is any sign of leachate seepage from the landfill site to the surrounding water bodies.

Seven samples were taken from the existing stream nearby. Samples were taken from streams running through Lin Ma Hang (WS1, WS2, WS3 and WS4) and those within the boundary of the existing NENT Landfill (WS5, WS6 and WS7). Drawing No. 24315/13/303 shows the locations of the sampling points. The samplings and testing are conducted by accredited laboratory under the HOKLAS. Table 5.4 summarises the sampling results.

Table 5.4: Summary of stream water analysis results

Parameter	Unit	Rep Limit	Lin Ma Hang Stream				Ping Yuen River
Parameter	Unit	Rep Limit	WS1	WS2	WS3	WS4	WS5	WS6	WS7
pH @25°C	---	0.1	6.6	6.9	6.3	6.7	6.2	7.1	7.3
Conductivity @ 25°C	μS/cm	1	76	59	42	49	24	67	175
SS	mg/L	0.5	0.8	4.7	7.3	6.7	46.7	162	12.8
CaCO₃	mg/L	1	<1	<1	<1	<1	<1	<1	<1
Chloride	mg/L	0.5	5	4	4	3	3	4	5
Zinc	μg/L	10	<10	<10	<10	<10	<10	<10	<10
Iron	μg/L	50	280	340	230	310	70	170	<50
Magnesium	μg/L	50	690	520	290	510	120	620	2470
Ammonia-N	μg/L	10	< 10	< 10	11	19	40	52	34
Nitrite-N	μg/L	10	< 10	< 10	< 10	< 10	< 10	< 10	< 10
Nitrate-N	μg/L	10	< 10	< 10	< 10	29	10	42	62
TKN-N	mg/L	0.1	0.2	<0.1	0.2	0.2	0.2	0.6	0.5
TOC	mg/L	1	2	2	<1	<1	<1	2	<1
DO	mg/L	0.1	5.6	10.1	7.8	8.5	10.7	10.1	7.0
COD	mg/L	2	9	3	4	3	3	15	7
BOD₅	mg/L	1	3	3	4	2	3	5	4

Note: The “<” sign denotes that the actual value was below reporting limit.

It could be observed from the above table that the sampled streams were free from leachate contamination at the moment of monitoring given the low concentrations of Ammonia-N, BOD₅ and COD recorded, as landfill leachate is usually characterised by high concentrations of these parameters. Previous groundwater and surface water monitoring records were also compared. The data also indicates that there is no contamination on the nearby water body from existing landfill.

The possible reason for the high SS concentration at WS6 is that it is at the downstream locations. Sediments from upstream due to soil erosion are being carried downstream hence resulting in a higher concentration of SS at this point. Measures to prevent pollution of nearby stream water during the construction and operation of the landfill extension are described in 5.8.

5.3.2.2 Sediment Quality

Measurement of river sediment quality was not covered by EPD’s river monitoring programme; therefore no past record on river sediment quality was obtained from EPD’s monitoring data.

During the water quality survey in early 2006, samples of sediment from the bottom of the streams were also taken and analysed. The analysed results are presented in Table 5.5.

Table 5.5: Summary of sediment analysis results

Parameter	Unit	Rep. Limit	LCEL	UCEL	Lin Ma Hang Stream				Ping Yuen River
Parameter	Unit	Rep. Limit	LCEL	UCEL	WS1	WS2	WS3	WS4	WS5	WS6	WS7
Redox Potential	mV	1	--	--	228	235	220	205	230	209	228
Silver	mg/kg	0.1	1	2	<0.1	<0.1	0.4	0.2	0.4	<0.1	<0.1
Arsenic	mg/kg	0.1	12	42	4.6	4.6	5.6	18.2	19.9	9.7	4.4
Cadmium	mg/kg	0.02	1.5	4	0.07	0.10	0.31	1.43	0.21	0.17	0.16
Chromium	mg/kg	0.2	80	160	11.8	6.1	8.2	7.5	7.6	3.3	5.2
Copper	mg/kg	0.2	65	110	3.3	4.7	8.0	14.0	3.4	2.8	3.3
Nickel	mg/kg	0.1	40	40	0.6	0.8	1.8	5.3	1.6	1.9	0.8
Lead	mg/kg	0.1	75	110	21.6	28.3	60.4	24	76.1	20.2	42.9
Zinc	mg/kg	0.1	200	270	24.0	35.5	56.2	155	39.6	37.3	65.4
Mercury	mg/kg	0.02	0.5	1	0.02	0.03	0.33	<0.02	0.04	<0.02	<0.02
TOC	%	0.05	--	--	0.12	<0.05	0.66	0.47	1.23	0.22	0.18
COD	mg/kg	2	--	--	5530	3060	22400	26700	26700	27500	4130
Total PCB	mg/kg	0.05	23	180	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05
Category of Sediment					L	L	L	M	M	L	L

Note: The “<” sign means the actual value was below detection limit.

Pollution of streambed sediment would be of concern only when they were disturbed. In normal condition, stream water quality would not be directly affected by sediment quality so long as dredging or filling of sediment is not involved. Nonetheless, the sediment samples from the above monitoring points were assessed against the Environment Transport & Works Bureau Technical Circular (TC) No 34/2002 Management of Dredged/Excavated Sediment to determine whether the concentrations of various key parameters in the sediment sample would be a cause of concern.

Table 5.5 above shows that the sediments from most of the sampling locations were of the least contaminated sediment category (Category L), with the exception of sediments at WS4 and WS5 which were of Category M. It means that one or more contaminant levels has exceeded the Lower Chemical Exceedance Level (LCEL) but not exceeded the Upper Chemical Exceedance Level (UCEL).

5.4 Water Sensitive Receivers

Water sensitive receivers (WSRs) under this Project include:

· Lin Ma Hang Stream to the northeast of the site;

· Shenzhen River to the north of the site; and

· Ping Yuen River to the southwest of the site.

· WSD Flood Pumping Station at Ping Yuen River

The beneficial use of Ping Yuen River is mainly water abstraction for irrigation on the surrounding agricultural lands. The flow direction of Ping Yuen River is towards River Indus, then Shenzhen River, and ultimately to Deep Bay while Lin Ma Hang Stream drains directly to Shenzhen River. Drawing no. 24315/13/303 shows the locations of the WSRs.

5.5 Assessment Methodology

5.5.1 Groundwater Flow

The ground conditions of the study area have been identified from the results of past and recent ground investigation works. The surface water movements in the catchment areas have also been studied.

A hydrogeological model of the Project site has been developed based on available records and monitoring data of existing ground water levels and distribution across the Project site. In order to obtain reasonable estimations of various quantities of each parameter, the following input data have been collated:

· Rainfall

· Evaporation

· Effective Rainfall

· Surface Runoff

· Infiltration and Aquifer Recharge

· Groundwater Flow

· Groundwater Storage

o Surface Water in Streams and Channels

o Soil Moisture in Vadose Zone

· Outflow through Extraction Wells

5.6 Identification and Evaluation of Water Quality Impacts

5.6.1 Pollution Sources from Construction Activities

Potential water pollution sources arising from construction activities include sources mainly from land-based activities, such as:

· Construction site runoff;

· Sewage effluent due to workforce on site;

· Drainage diversion; and

· Groundwater seepage.

5.6.1.1 Construction Site Runoff

Construction site runoff comprises:

· Runoff and erosion from excavation areas, drainage channels, and stockpiles;

· Wash water from dust suppression sprays and wheel washing facilities;

· Fuel, oil, solvent and lubricants from maintenance of construction machinery and equipment.

Construction runoff may cause physical, biological and chemical impacts. Physical impacts include potential blockage of drainage channels and increase of SS concentration in the receiving drainage channel. Local flooding may occur during heavy rainfall if construction runoff is not properly drained. Chemical and biological effects caused by the construction runoff are highly dependent upon the chemical and nutrient contents of the runoff. Runoff containing significant amounts of concrete and cement-derived material may cause primary chemical effects such as increase in turbidity and discoloration, elevation in pH, and accretion of solids. Secondary impacts, such as toxic effects to water biota due to the elevated pH values, and reduction in decay rate of faecal micro-organisms and photosynthetic rate due to the decreased light penetration may result.

5.6.1.2 Sewage Effluent from Workforce on Site

Sewage effluents will be generated from the sanitary facilities provided for on-site construction workforce. The characteristics for such sewage are its high BOD₅, Ammonia and E. coli levels.

5.6.1.3 Drainage Diversion

The potential water quality impact associated with drainage diversion will be from the run-off and erosion from site surfaces and earthwork areas. All existing upstream channel will be diverted off site and discharged to the downstream river.

5.6.1.4 Groundwater Seepage

Ground investigation has been carried out to determine the groundwater levels within the Project site. Groundwater seepage would not be an issue for the project of NENT Landfill Extension as deep excavation, tunnel boring or other underground works are not anticipated.

5.6.2 Environmental Risk Due to Seepage of Leachate

5.6.2.1 Theory

The composite liner system for the NENT Landfill Extension forms a critical component of the landfill design for protection of groundwater and the surrounding environment.

The assessment of leachate seepage is based on the properties of liner materials as shown in Table 5.6.

Table 5.6: Properties of liner materials

Material	Thickness	Hydraulic Conductivity (m/s)
HDPE	2.0 mm	10^-15
Bentonite Matting	6.0 mm	10^-9

A geomembrane has an extremely low permeability, and therefore, the rate of seepage due to permeability is negligible as compared to the rate of seepage through defects (Giroud and Bonaparte 1989) or due to accidental damage during landfill operation. Therefore, seepage through defects or due to accidental damage will be the dominant source. Accidental damage of liner during landfill operation may potentially cause significant leakage of leachate but this could be minimized by good practice, management and regular inspection on site. In case of leachate leakage due to accidental damage of lining system, the Contingency Plan in place, as described in Section 5.8.2.1 would help prevent any contamination of the surrounding natural environment. Therefore only seepage of leachate due to defect in geomembrane will be assessed.

If there is a defect in the geomembrane, it will flow laterally for some distance between the geomembrane and the bentonite matting, and finally infiltrate in the low permeability soil. The flow between geomembrane and the bentonite matting is referred to as the interface flow, which is highly dependent upon the quality of contact between the two components. If the geomembrane is laid with as few wrinkle as possible on top of a bentonite matting layer that has been adequately compacted and has a smooth surface, it is considered to have good contact condition. In the case of the liner system at NENT Landfill Extension site, which will consist of geomembrane and bentonite, good contact conditions can be assumed because the bentonite slurry that may exude from a hydrated geosynthetic clay liner (GCL) contributes to establishing a close contact between geomembrane and the GCL.

There are mainly two types of defects; namely: manufacturing defects and installation defects. Typically geomembranes may have about 1 to 2 pinholes per hectare from manufacturing defect (pinholes are defects with a diameter equal or smaller than the geomembrane thickness). The frequency of occurrence of installation defects is a function of the quality of installation, testing, material, surface preparation, equipment and QA/QC programme.

Studies by Giroud and Bonaparte (1989) have shown that geomembrane liners installed with strict construction quality assurance could have one to two defects per 4000m² with a typical defect diameter of 2mm.

When assessing the potential seepage of leachate across a composite liner (made up of a 2mm geomembrane on a layer of 6mm bentonite), the following assumptions have been made:

· The GCL has a saturated hydraulic conductivity of 1X10^-9m/s, which is the minimum requirement in the existing NENT Landfill. (The minimum requirements in USEPA 40 CFR Part 258 is 1 x 10^-7 cm/s).

· 4 defects are assumed in every hectare, which represents “Good” installation quality. (Schroeder et al., 1994)

· Contact quality factor of 0.21 (i.e. good contact conditions) is assumed. It corresponds to a geomembrane installed, with as few wrinkles as possible, on top of low permeability soil layer that has been adequately compacted and has a smooth surface. (Bonaparte et al., 1989)

· Giroud et al. (1997)’s equation for calculating the flow through a composite liner having circular defect with diameter of 2mm.

- Equation 1

Where Q= Seepage rate through the considered geomembrane defect (m³/s)

A= Considered geomembrane area (m²)

n= Number of defects per considered geomembrane area (A)

C_qo= Contact quality factor

h= Hydraulic head on top of the geomembrane (m)

t_s= Thickness of the low-permeability soil component of the composite liner (m)

d= Diameter of circular defect (m)

k_s= Conductivity of liner

There are two limitations in applying the above equation to predict seepage of leachate through a defect (Giroud et al. 1997):

· The diameter of the circular defect should not be less than 0.5mm or greater than 25mm

· The liquid head on top of the geomembrane should be equal to or less than 3m

5.6.2.2 Assessment Results

Assessment results show that for a composite liner with good contact condition between geomembrane and bentonite matting which has a saturated hydraulic conductivity of
1x10^-9m/s, the rate of seepage would be 7.73 litres per hectare per day. The flow rate could be further reduced by lowering the conductivity of the bentonite matting and the number of defects per unit area through better QA/QC programme to improve the installation quality to “Excellent” (Schroeder et al., 1994). A conductivity of 1x10^-11 m/s should generally be adopted for bentonite in a modern landfill. (SENT landfill has been adopting lining system with bentonite of the conductivity of 1x10^-11 m/s.)

The potential amount of leaked leachate from the NENT Landfill Extension site reaching the groundwater collection layer would be 0.26 litres per hectare per day, if bentonite conductivity of 1x10^-11 m/s is assumed. The depth of leaked leachate mixing with groundwater would be 0.0019mm per year. The “Working Paper on Assessment of Existing Groundwater Regime and Potential Changes Resulting from Future Landfill Operation” has predicted the depth of water that will infiltrate into the groundwater system to be 126mm. For leachate with typical COD and NH₃-N concentrations of 4,485mg/L and 2,863mg/L^5-[1] , the increase in COD and NH₃-N concentrations of the groundwater will be 0.33mg/L and 0.21mg/L respectively, which are negligible and well within the respective trigger levels of 30mg/L and 5mg/L. Table 5.7 shows the potential impact on groundwater quality under various defect conditions.

Table 5.7: Potential impacts of leachate seepage on groundwater quality

No. of Defects /ha	Conductivity (m/s)	Rate of seepage (l/h/d)	Depth infiltrated (mm/yr)	Groundwater Quality
No. of Defects /ha	Conductivity (m/s)	Rate of seepage (l/h/d)	Depth infiltrated (mm/yr)	COD (mg/L)	NH₃-N (mg/L)
4	1 x10^-11	0.26	0.0093	0.33	0.21
3	1 x10^-11	0.19	0.0070	0.25	0.16
2	1 x10^-11	0.13	0.0047	0.17	0.11
1	1 x10^-11	0.06	0.0023	0.08	0.05

In practice, an average of 4 defects per ha of liner could be easily achieved by good manufacturing quality and QA/QC programme (Girond and Bonaparte, 1989). The impact on groundwater quality, in particular COD and NH₃-N concentrations, due to seepage of leachate will then be less than 0.33mg/L and 0.21mg/L respectively, which is negligible.

In case of seepage / leakage, the leaked leachate will be collected via the groundwater collection layer and will be drained to the on-site leachate treatment plant. The impact on groundwater quality due to seepage / leakage of leachate is therefore assessed to be unlikely.

5.6.2.3 Risk Due to Accidental Leakage of Leachate

The selected layout (Option 4) will have no encroachment on the Lin Ma Hang Stream and its catchment as well as Shenzhen River, the landfill extension works will have no impact on these rivers and the environmental risk to these water bodies due to seepage of leachate or other wastewater is considered unlikely. Nevertheless, the potential impacts of accidental leakage of leachate due to rupture of leachate pipelines, failure of pipe joint sealing and damage of geomembrane are catered in the contingency plan to be discussed in Section 5.8.2.1. With the prompt and effective implementation of the contingency plan, no adverse impact on groundwater quality of the Project site is anticipated.

5.6.3 Potential Impacts on Groundwater Regime

5.6.3.1 General

A separate hydrogeology assessment had been carried out to assess the existing groundwater regime in the region and to evaluate the potential changes resulting from future landfill operation. The assessment results are summarised in the following sub-sections.

5.6.3.2 Site Geology

A separate ground investigation was carried out to obtain the existing ground conditions of the site.

For superficial geology, fill deposits were encountered within a number of drill-holes during the recent ground investigation. The nature of the deposits was mainly gravel. It is apparent that these deposits have been formed as a result of stockpiling by the existing NENT Landfill site. Thin layers of colluvium were identified during the ground investigation. The typical nature of the deposits was silt. It is apparent that the colluvium is mostly located within natural drainage channels / topographic depressions and is typically of thickness of not exceeding 2.0m. Weathered tuff was also identified at some drill-holes during field inspections.

For solid geology, volcanic tuff rock or metamorphosed tuff was identified in most of the drill-holes. Metasedimentary rock in the form of sandstone was identified in only one drill-hole during the recent ground investigation.

For structural geology, a number of faults were identified based on aerial photograph interpretation. Desktop study, visual inspections of the site and the recent ground investigation work have confirmed the following:

· The first fault (Fault 1) was located along the northern boundary of the study area and was striking approximately west-northwest.

· The second fault (Fault 2) strikes north-northeast through the study area, most likely extending through the existing waste reception area to the south of the site and then following the topographic valley northeast from this.

· The third fault (Fault 3) follows the approximate alignment of the existing haul road through the centre of the site, trending west-northwest to east-southeast, and extends beyond the site boundaries.

· The fourth fault (Fault 4) is most likely a large splay fault associated with Fault 2.

5.6.3.3 Catchment Areas

The proposed NENT Landfill Extension is located at the north-eastern end of a large catchment area surrounding a low-lying alluvial valley running from Ta Kwu Ling to Pak Hok Shan. The catchment area is bound on its north-eastern side by the major topographic ridgelines running between Wong Mau Hang Shan, Wo Keng Shan and Cheung Shan, and along its south-western side by the ridges between Cham Shan, Wa Shan and Tsung Shan. The catchment has a total area in the order of 1,250 ha.

The existing catchment areas in the vicinity of the NENT Landfill Extension are shown in Drawing No. 24315/13/304. As shown in the drawing, the landfill extension will not encroach into the catchment for Lin Ma Hang Stream.

The NENT Landfill Extension area is located at the upstream catchments of Ping Yuen River. The topography within Catchment Area GE01A where the majority of the site area will be located consists largely of relatively steep sided hill slopes that are likely to result in higher occurrence of run-off than infiltration of rainfall. The two downstream catchments, namely GE02A and GE03A are mainly low-lying areas with shallow gradient. The potential for direct run-off of groundwater will be the infiltration of rainfall into the groundwater system. This means that these two downstream catchments potentially form a larger recharge resource for the groundwater table than the area within the proposed landfill extension site and thus the impact on groundwater flow would unlikely be significant.

Since there is no encroachment into the Lin Ma Hang Stream Catchment, the landfill extension works will have no impact on the groundwater level within and downstream of the Lin Ma Hang catchment.

5.6.3.4 Groundwater Resources

There is no available record showing the past yields of ground water extraction wells within any vicinity villages. Investigation has been conducted to identify the number of villages in the vicinity of the NENT Landfill Extension site that are relying on extraction wells to provide groundwater supply. According to the water main record plan from WSD, most of the villages in the vicinity areas are supplied with fresh water supply. The number of villages potentially affected by the Project would be minimal.

5.6.3.5 Groundwater Model

A conceptual groundwater model for the study area was established in accordance with the procedures described in Section 5.5.2 to predict the potential impact to the future groundwater flow pattern of the site. The prediction results are presented in the following sub-sections.

5.6.3.6 Impact on Surface Water Runoff

For the purpose of this study, the most substantial impact on stream flow would be during the landfill operation period, during which time all surface runoff flow generated from the active tipping face would require collection and discharge to the leachate treatment plant for preliminary treatment prior to disposal at Shek Wu Hui Sewage Treatment Works while the remaining surface runoff within the site will be collected by surface drainage channels and discharged into downstream watercourses. The quality of surface runoff discharged to downstream watercourses from the existing NENT Landfill is monitored on a quarterly basis. Table 5.7a summarises the surface water monitoring results in 2005.

Table 5.7a: Quarterly surface water monitoring results in 2005

Parameters	Annual Average (Range)
Parameters	SP1 (near waste reception area with the Stockpile & Borrow Area at upstream)		SP2 (near leachate treatment plant with the existing landfill at upstream)
Sample Temperature, °C ^[3]	22.5	(18.3-26.1) SD=3.5	27.5	(24-30) SD =26
pH	7	(6.6-7.2) SD=0.27	7.5	(6.9-8) SD = 0.45
E. C., μS/cm	145	(123-186) SD =28	589.8	(440-839) SD=187
SS, mg/L	7.5	(4-12) SD = 4.1	4.5	(4-5) SD=0.96
Alkalinity, mg/L	35.8	(29-40) SD=4.8	138.5	(102-165) SD=26.7
COD, mg/L	4	(2-6) SD=2	5	(2-8) SD=3.46
BOD₅ , mg/L	2	SD = NA^[1]	2	SD = NA^[1]
TOC, mg/L	1	SD = NA^[1]	<1	SD = NA^[1]
Ca, mg/L	16.8	(11.6-26.6) SD=6.7	96.1	(62.1-140) SD=36.9
Mg, mg/L	2.0	(1.6-2.7) SD=0.49	4.8	(3.3-5.9) SD =1.08
Na, mg/L	5.1	(3.7-5.9) SD=0.99	13.8	(11.8-18.6) SD =3.23
Cu, mg/L ^[4]	<0.01	SD = NA^[1]	<0.01	SD = NA^[1]
Fe, mg/L	1.8	(0.42-3.8) SD=1.7	0.30	(0.19-0.42) SD=0.17
Mn, mg/L	1.0	(0.002-1.86) SD=0.88	0.79	(0.002-1.79) SD=0.84
Ni, mg/L^[4]	<0.01	SD = NA^[1]	<0.01	SD = NA^[1]
Zn, mg/L	0.04	(0.022-0.06) SD =0.024	<0.01	SD = NA^[1]
Pb, mg/L	0.001	(0.001- 0.01) SD=0.005	<0.001	SD = NA^[1]
Cd, mg/L	<0.001	SD = NA^[1]	<0.001	SD = NA^[1]
Cr, mg/L^[4]	<0.01	SD = NA ^[1]	<0.01	SD = NA^[1]
Cl^-, mg/L	6.5	(2-13)	8.8	(4-12) SD=3.6
SO₃^2-, mg/L	<2	SD = NA^[1]	<2	SD = NA^[1]
SO₄^2-, mg/L	22.3	(7-60) SD=25.3	119.5	(50-199) SD=64.6
PO₄^3-, mg/L	0.02	(0.01-0.03) SD=0.01	0.01	SD=NA¹
NH₃, mg/L	0.11	(0.05-0.17) SD=0.051	0.16	(0.08-0.27) SD=0.09
NO₃‾ , mg/L	0.19	(0.17-0.23) SD=0.053	0.63	(0.4-0.72) SD=0.15
TKN, mg/L	0.27	(0.2-0.4) SD=0.13	0.3	(0.2-0.4) SD=0.08
Total Coliform, CFU/100ml^[2]	67	(13-660) SD=5.3	119	(26-4600) SD=11.6

Note [1] : SD=NA indicates that standard derivation is not applicable due to the monitoring data is lower than the detection limit

[2] : Geometric mean and standard derivation are performed for Total Coliform

[3]: SP1 and SP2 are under different catchments, the sources of the water and the flow conditions are different. Therefore, there is a difference in parameters for the two different drainage systems.

[4]: The Yr 2004 and part of Yr 2005 sampling data were carried out by two different laboratories with different instruments and the detection limit for the two instruments was not the same.

Table 5.7b: Quarterly surface water monitoring results in 2004

Parameters	Annual Average (Range)
Parameters	SP1 (near waste reception area with the Stockpile & Borrow Area at upstream)		SP2 (near leachate treatment plant with the existing landfill at upstream)
Sample Temperature, °C^[3]	21	(16.4 –25.9) SD = 4.8	25.9	(22.2 – 29.7) SD = 3.3
pH	7.0	(6.9 – 7.3) SD = 0.2	8.0	(7.6 – 8.2)SD = 0.3
E. C., μS/cm	114	(78 – 130) SD= 24	465	(446 - 477) SD = 13
SS, mg/L	6.8	(4 – 10) SD = 2.5	6.0	( 3 – 11) SD = 3.6
Alkalinity, mg/L	38	(32 – 46) SD = 6	132	(107 – 154) SD = 20
COD, mg/L	2.3	(2 – 3) SD = 0.5	< 2	SD = NA^[1]
BOD₅ , mg/L	< 2	SD = NA^[1]	< 2	SD = NA^[1]
TOC, mg/L	1.3	(1- 2)SD = 0.5	< 1	SD = NA^[1]
Ca, mg/L	12.9	(8.9 – 16.4) SD = 3.2	76.7	(72 – 84.5) SD = 5.8
Mg, mg/L	1.6	(1 – 2) SD = 0.4	4.1	(4.0 – 4.6)SD = 0.33
Na, mg/L	5.4	(4.7 – 5.9)SD = 0.5	12.2	(9.5 – 13.6) SD = 2.0
Cu, mg/L	< 0.001	SD = NA^[1]	0.0013	(0.001 – 0.002) SD = 0.0005
Fe, mg/L	2.1	(0.06 – 3.2) SD = 1.4	0.28	(0.05 – 0.71) SD = 0.31
Mn, mg/L	1.5	(1.2 – 1.9) SD = 0.4	1.0	(0.273 – 1.7) SD = 0.62
Ni, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Zn, mg/L	0.012	(0.01 – 0.016) SD = 0.003	< 0.001	SD = NA^[1]
Pb, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Cd, mg/L	< 0.0002	SD = NA^[1]	0.0003	(0.0002 – 0.0006) SD = 0.0002
Cr, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Cl^-, mg/L	5.3	(4 – 7) SD = 1.5	8.5	(4-13) SD = 3.9
SO₃^2-, mg/L	< 2	SD = NA^[1]	< 2	SD = NA^[1]
SO₄^2-, mg/L	13	(3 –20) SD = 8.4	102	(58 –181)SD = 55
PO₄^3-, mg/L	0.015	(0.01 – 0.03) SD = 0.01	0.01	SD = NA^[1]
NH₃, mg/L	0.14	(0. – 0.19) SD = 0.06	0.22	(0.12 – 0.3)SD = 0.1
NO₃‾, mg/L	0.18	(0.1 – 0.25)SD = 0.08	0.50	(0.35 – 0.7) SD = 0.15
TKN, mg/L	0.18	(0.1 – 0.2) SD = 0.05	0.38	(0.2 – 0.6) SD = 0.2
Total Coliform, CFU/100ml^[2]	156	(72 – 320)SD = 112	1005	(100 – 3300) SD = 1535

Note [1] : SD=NA indicates that standard derivation is not applicable due to the monitoring data is lower than the detection limit

[2] : Geometric mean and standard derivation are performed for Total Coliform

[3]: SP1 and SP2 are under different catchments, the sources of the water and the flow conditions are different. Therefore, there is a difference in parameters for the two different drainage systems.

Table 5.7c: Quarterly surface water monitoring results in 2003

Parameters	Annual Average (Range)
Parameters	SP1 (near waste reception area with the Stockpile & Borrow Area at upstream)		SP2 (near leachate treatment plant with the existing landfill at upstream)
Sample Temperature, °C^[3]	22.3	(17.6 – 25.3) SD = 3.4	26.6	(24 – 29) SD = 2.6
pH	7.1	(6.8 – 7.3) SD = 0.2	7.7	(7.2 – 7.9) SD = 0.3
E. C., μS/cm	124	(112 – 156) SD = 21.4	440	(388 – 527) SD = 63.0
SS, mg/L	7.6	(1.5 – 14) SD = 5.5	6.5	(5 – 8) SD = 1.29
Alkalinity, mg/L	36.5	( 35 – 38) SD = 1.3	135	(111 – 151) SD = 17.1
COD, mg/L	2.8	(2 – 4) SD = 1.0	2.8	(2-4) SD = 1.0
BOD₅ , mg/L	2.3	(2-3) SD = 0.5	2.3	(2-3) SD = 0.5
TOC, mg/L	1.3	(1 – 2) SD = 0.5	< 1	SD = NA^[1]
Ca, mg/L	26.3	(10.7 – 63.1) SD = 24.7	42.2	(12.5 – 77.3)SD = 34.3
Mg, mg/L	2.5	(1.5 – 4.7) SD = 1.5	3.6	(1.8 – 5.1) SD = 1.4
Na, mg/L	16.5	(5.0 – 43.1) SD = 18.1	9.2	(5.5 –11.8) SD = 3.0
Cu, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Fe, mg/L	1.3	(0.025 – 2.85) SD = 1.3	1.07	(0.025 – 2.55) SD = 1.1
Mn, mg/L	1.8	(1.1 – 2.77) SD = 0.7	2.1	(1.49 – 2.56) SD =0.5
Ni, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Zn, mg/L	< 0.01	SD = NA^[1]	< 0.01	SD = NA^[1]
Pb, mg/L	0.0013	(0.001 – 0.002) SD = 0.0005	< 0.001	NA^[1]
Cd, mg/L	0.00023	(0.0002 – 0.0003) SD = 0.00005	0.0004	(0.0002 – 0.001) SD = 0.0004
Cr, mg/L	< 0.001	SD = NA^[1]	< 0.001	SD = NA^[1]
Cl^-, mg/L	7.5	(5 – 10) SD = 2.4	9	(7 – 13) SD = 2.7
SO₃^2-, mg/L	< 2	SD = NA^[1]	< 2	SD = NA^[1]
SO₄^2-, mg/L	12.3	(9 – 20) SD = 5.2	58.8	(42 – 85)SD = 18.5
PO₄^3-, mg/L	< 0.01	SD = NA^[1]	< 0.01	SD = NA^[1]
NH₃, mg/L	0.19	(0.07 – 0.33)SD = 0.12	0.4	(0.32 – 0.5)SD = 0.08
NO₃‾, mg/L	0.16	(0.1 – 0.21) SD = 0.05	0.33	(0.22 – 0.51)SD = 0.14
TKN, mg/L	0.3	(0.2 – 0.4) SD = 0.1	0.48	(0.4 – 0.6) SD = 0.1
Total Coliform, CFU/100ml^[2]	212	(48 – 540) SD = 223	66	(13 –120) SD = 52

Note [1] : SD=NA indicates that standard derivation is not applicable due to the monitoring data is lower than the detection limit.

[2] : Geometric mean and standard derivation are performed for Total Coliform

[3]: SP1 and SP2 are under different catchments, the sources of the water and the flow conditions are different. Therefore, there is a difference in parameters for the two different drainage systems.

Drops in stream flow within surface drainage system at Wo Keng Shan are anticipated during the operation stage as the landfill extension site forms a major portion of upstream catchment for this village. Further downstream in Ta Kwu Ling valley, streams will also be substantially fed by run-off from other catchments in the vicinity. The degree of impact on the stream flow in Ta Kwu Ling will be significantly less than that of Wo Keng Shan.

Upon completion of the landfill works, the Project site will be capped for afteruse. Any surface runoff generated over the area will then be collected within surface drainage channels and discharged into downstream river systems. New drainage channel will be provided along the site boundary to convey all surface runoff to Ping Yuen River. Water quality monitoring will be continued during restoration and aftercare periods.

Given that there will be no deep infiltration of groundwater after capping; all precipitation will be entered into the hydraulic system as either surface runoff or interflow through the topsoil material. The resultant surface water flow for the Ping Yuen Catchment will therefore be comparable to the existing condition prior to the landfill extension development.

5.6.3.7 Impact on Groundwater Regime

Local Impact at Project Site

The formation of a fully-lined and capped landfill within the proposed landfill extension area will mean that any infiltration that currently occurs within the stockpile and borrow area will be removed from the hydrological system. Although upon completion of the landfill operation this volume of water will be diverted to the surface water, there will be some resultant loss of recharge to the main groundwater body beneath the site area as the main recharge source at upstream will have been lost.

A conservative assessment had been carried out, the calculated depth of aquifer recharge that would be lost to the hydrogeological system is about 126mm per year. It means that the groundwater level beneath the extension site may potentially fall up to 1.5m during the operational lifetime of the landfill extension, which is estimated to be 10 to 12 years. After completion of waste filling, a permanent final capping layer will be installed and the sites will be recharged.

Regional Impact on Surrounding Area

Only two of the villages downstream of the landfill extension area, namely Wo Keng Shan and Ping Yeung, are located in areas where a large portion of their catchments are formed by the landfill extension site.

While the reduction in ground water level in the downstream areas will not be as significant as those directly beneath the landfill extension site, some resultant draw down of groundwater can be anticipated. It is estimated that ground water levels at Wo Keng Shan could fall by 0.5m to 1m over the operational lifetime of the landfill extension whereas a drop of 0.6m can be expected at Ping Yeung over the period. This estimation is considered to be conservative as the groundwater table downstream will be recharged by adjacent catchments. In view of the minimal impact anticipated on these areas (only 1 m fall in Wo Keng Shan Village), a full-scale hydrogeological investigation for the entire catchment (1,250 ha) is considered not necessary at the feasibility study stage but will be included in the NENT Landfill Extension Contract.

5.6.3.8 Recommendations

A number of measures to mitigate the potential loss of groundwater yields to Ping Yeung and Wo Keng Shan areas, where necessary, have been proposed as follows:

· Provision of adequate water supply for irrigation purposes to the affected villages downstream during the operational lifetime of the landfill extension, i.e. 10 to 12 years. Such provision should be included in the landfill extension contract document;

· Installation of a network of monitoring stations to keep track of the stream flow volumes. Should monitoring of stream flow indicate insufficient quantities to provide sufficient water for irrigation downstream, a contractual requirement for the DBO Contractor to “tank in” water from an external source could be imposed. This is the system currently in place for the existing NENT Landfill;

· Diversion of flow from other catchments outside the site boundary. The surface runoff generated in the catchments with abandoned agricultural lands could be collected and conveyed to the active agricultural lands;

· Formation of new extraction wells that extend deeper down within the aquifer; and

· Artificial recharge by surface spreading, spray irrigation or pumping water directly into the ground via vertical shafts.

5.6.4 Leachate Collection and Treatment System

5.6.4.1 Background

Raw leachate is collected and conveyed to the existing on-site leachate treatment plant for treatment. The existing leachate treatment plant consists of six leachate lagoons and an ammonia stripping plant for nitrogen removal. The design capacity of the leachate treatment plant is about 1,200m³/day. The total storage capacities of the existing leachate lagoons are about 84,500m³. Treated leachate is pumped to the existing DSD Pumping Station and then conveyed to the Shek Wu Hui Sewage Treatment Works for further treatment. The layout of existing leachate treatment plant is shown below.

According to the existing monitoring data, the characteristics of raw leachate entering the leachate treatment plant are shown in Table 5.8.

The Water Discharge Licence W5/2G32/5 granted to the existing leachate treatment plant at NENT Landfill has specified the discharge limits on various parameters as well as the maximum effluent flow rate (Table 5.9).

Table 5.8: Characteristics of raw leachate at existing NENT Landfill in 2004 and 2005

Parameters	Average^[1] (Range)
Parameters	2004	2005
Leachate Temperature (°C)	23.2 (16.7 – 30.1), SD=5.5	25.0 (19.1 – 30.1), SD=4.9
pH	8.4 (8.4 – 8.5), SD=0.05	8.3 (8.2 – 8.4), SD=0.1
BOD₅ (mg/L)	814 (780 – 840), SD=25	1665 (900 – 2940), SD=957
COD (mg/L)	3418 (2700 – 4050), SD=554	4485 (3610 – 4970), SD=623
SS (mg/L)	30 (21 – 44), SD=10.7	84 (39 – 157), SD=51
NH₃-N (mg-N/L)	3395 (2800 – 4060), SD=552	2863 (2000 – 4560), SD=1187
Nitrate (mg-N/L)	<0.1, SD=NA^[2]	<0.1, SD=NA^[2]
TN (mg-N/L)	3685 (3100 – 4120), SD=445	2980 (2000 – 4620), SD=1171

Note: [1] monitoring was conducted on a quarterly basis.

[2] SD=NA indicates that standard derivation is not applicable due to the monitoring data is lower than the detection limit

Table 5.9: Discharge limits on effluent from NENT Landfill Leachate Treatment Plant

Parameters	Limit	Average Effluent Quality (Range)
Parameters	Limit	2004	2005
Daily Flow Rate	800 m³/day (Nov to May) 1,200 m³/day (June to Oct)	626 (345 - 1251), SD=188 852 (460 – 1577), SD=244	696 (455 – 1196), SD=195 1293* (1009 – 1552), SD=245
BOD₅	400 mg/L	10 (3 – 25), SD=4.5	14 (3 – 34), SD=8.6
COD	2,000 mg/L	1205 (940 – 1720), SD=359	987 (424 – 1620), SD=388
NH₃-N	5 mg/L	0.8 (0.5 – 1.05), SD=0.23	0.9 (0.45 – 3.6), SD=0.86
TN	200 mg/L	121 (100 – 149), SD=20.6	121 (57 – 193), SD=43

Note: 1. Monitoring was conducted on a monthly basis.

2. * Buffer storage lagoons had been provided on site to store the treated-effluent before discharging to the DSD SWHSTW. There is no exceedance of discharge limit in the past.

According to monitoring data from the existing NENT Landfill (see Table 5.9), abnormalities in flow rate were recorded during extremely bad weather in wet season. Nevertheless, sufficient on-site storage lagoons have been provided to cater for the worst-case weather condition, and there is no overflow or discharge of leachate to Ping Yuen River and its tributaries during the operation life of the existing landfill.

5.6.4.2 Leachate Generated from NENT Landfill Extension

The leachate generated by the NENT Landfill Extension has been estimated. Under normal meteorological condition (i.e. with an average annual rainfall of 1,875 mm, data taken from Ta Kwu Ling Station from 1999 to 2005), the peak leachate flow rate from restored NENT Landfill and NENT Landfill Extension (under fully operation in Year 10) is estimated to be (265+860 =) 1,105 m³ /day in wet season, which is within the design capacity of the existing leachate treatment plant (i.e. 1,200 m³ /day).

Under severe meteorological condition with an ultimate annual rainfall of 2,503 mm in Year 2001 (the worst-case scenario from 1999 to 2005), the peak leachate flow rate could reach a max of (350+1,150 =) 1,500m³ /day in wet season (during the Year 10 of the operation). To minimise the impact to the downstream infrastructure (including the DSD pumping station, downstream rising main and SWHSTW), the excess leachate of (1,500 – 1,200=) 300m³/day will be temporarily stored on site. Similar to the existing NENT Landfill (Table 5.9), storage tanks / lagoons will be provided to store the excess leachate flow for detention before on-site treatment. Temporary leachate storage lagoons will be constructed to cater for the abnormalities in flow rate due to extremely severe storm in wet season, and will be designed with sufficient detention time to control the outflow to comply with the Discharge Licence.

As discussed in the previous section, the peak leachate generation rate from both landfill sites will be about 1,500 m³/day under severe storm events, including 1,150 m³/day from the NENT Landfill Extension and 350 m³/day from the restored NENT Landfill. Nonetheless, the maximum leachate flow of 1,150m³/day will only be generated during full-scale operation of NENT Landfill Extension. Prior to the full-scale operation, the amount of leachate generated will be much less.

After restoration of existing NENT Landfill, a maximum leachate flow of 350m³/day from the restored NENT Landfill is anticipated during the initial period of aftercare. With the full development of final impermeable capping, rainwater infiltration will be much reduced leading to reduction in leachate amount. In reality, the full-scale operation of NENT Landfill Extension will not coincide with the initial aftercare phase of the existing NENT Landfill. The peak leachate flow of 1,500m³/day for the two landfills is therefore only a theoretical maximum.

5.6.4.3 Leachate Minimization

The proposed landfill extension will adopt even more strengthen operation mode to control the leachate generation.

The leachate generation rate is greatly dependent on the meteorological conditions and phasing of the landfill extension. In order to minimise leachate generation, the phasing of landfill extension will be controlled with detailed planning. The following leachate minimization program will be specified in the DBO Contract for implementation by the DBO Contractor:

- Phased development and closure to minimize the active area footprint;

- Temporary geosynthetic covers to minimize infiltration in active cells;

- Run-on and runoff control systems for active and inactive tipping areas;

- Sub-surface drainage systems to control groundwater seepage;

- Low permeability final cover systems to minimize infiltration during post-closure, and

- Cell construction techniques that promote surface runoff rather than infiltration.

Nevertheless, progressive restoration is encouraged where practicable. With detailed planning on temporary and permanent restored area, leachate generation rate could be under control and greatly reduced. No discharge or overflow of leachate to the adjacent streams, rivers and culverts is anticipated.

5.6.4.4 Leachate Treatment Schemes

Various options for future treatment of the leachate have also been considered. Due to the close proximity and similar applications (similar catchment area, similar waste quantity per day, similar waste composition) of the two landfills, qualities of leachate generated from the two sites are expected to be similar.

Two leachate treatment scenarios have been considered. The first option is to deploy the existing treatment facility for both sites while the second option is to build a new plant for the NENT Landfill Extension.

Utilization of the existing leachate treatment plant and building a new storage lagoon to store any excess leachate under the severe storm event is considered the preferred treatment option. This will minimise further impact to the existing DSD Pumping Station and the downstream Shek Wu Hui Sewage Treatment Works.

The raw leachate generated from the NENT Landfill Extension will be conveyed to the existing treatment plant fully utilising its remaining capacity. Temporary storage lagoons will also be provided to cater for the period of peak leachate generation rate on the excess leachate under the severe storm event. The total outflows to DSD Pumping Station as well as to the SWHSTW will be kept to 1,200 m³/day to minimise the impact to downstream network.

Under the worst-case contractual scenario, new leachate treatment facilities with a capacity of 1,200 m³/day is planned to cater for the flows from the NENT Landfill Extension, while the existing treatment plant will continue to serve the restored landfill. The new leachate treatment facilities will consist of an ammonia stripping plant and a sequencing batch reactor (SBR). The treated leachate from the new treatment plant would then be pumped to the existing DSD pumping station within the existing leachate treatment plant for subsequent conveyance to the SWHSTW for further treatment.

The new leachate treatment for the NENT Landfill Extension will be located near the waste reception area of the existing NENT Landfill due to the topography constraints for gravity leachate collection system. The proposed locations are indicated in Drawing No. 24315/01/005. Approximately 2 ha of land area is required for the construction of new leachate treatment facilities. If more advanced treatment technology is available at the time of implementation, the area of the leachate treatment facilities could be much reduced.

Treated leachate discharged from the two leachate treatment plants will be collected in storage lagoons before connecting to DSD’s existing discharge point. The discharge limit of 1,200 m³/day will remain unchanged (i.e. the total amount of treated leachate to be discharged to DSD’s sewerage network will not exceed 1,200 m³/day). Regular leachate flow monitoring will be conducted. Impact on the capacity of the downstream sewerage infrastructure system due to the NENT Landfill Extension is not expected.

5.6.5 Implication of IWMF Implementation

If the IWMF would be commissioned around the same time as the NENT Landfill Extension, NENT Landfill Extension will be receiving residues from IWMF. The waste as well as the leachate characteristics will vary significantly from the existing ones. Due to its low biodegradable content, residue from IWMF usually generates less leachate than common municipal waste, although it may however contain higher concentrations of heavy metal and toxic substances. Given that the final cover will consist of an impermeable mineral layer, a drainage layer of at least 0.5 metre and at least one metre of top soil, the leakage of the IWMF waste is not anticipated.

Table 5.10 presents the characteristics of the leachate generated from a typical landfill in Japan which contains over 75% of incinerated residue (K Ushikoshi et al., 2002).

Table 5.10: Characteristics of raw leachate from landfill with mainly incinerated residue

Parameters	Range
pH	7.1 - 10.5
Turbidity, turb. unit	2.8 - 39.9
Colour, colour unit	14 - 80
Electric conductivity, mS/m	237 - 2,980
M-alkalinity, mg CaCO₃/L	30.1 - 101
Total hardness, mg CaCO₃/L	642 - 8,961
Ca, mg/L	232 - 3,560
Mg, mg/L	2.5 - 78
Na, mg/L	167 - 2,760
K, mg/L	104 - 2,470
Free CO₂, mg/L	0 - 15.7
Cl, mg/L	655 - 11,700
SO₄, mg/L	31.1 - 207
SiO₂, mg/L	2.4 - 26.3
Mn, mg/L	0.6 - 4.77
Fe, mg/L	0.01 - 5.3
Ba, mg/L	0.18 - 6.08
Sr, mg/L	1.1 - 17.6
B, mg/L	0.06 - 8
Total Salinity	2,190 - 27,300
BOD₅ , mg O₂/L	<5 - 155
COD, mg O₂/L	7.9 - 97.4
Total-N, mg N/L	2.2 - 82
NH3-N, mg N/L	0.96 - 33.7
SS, mg/L	9 – 67
Dioxins + Furans, pg-TEQ/L	2.2
Coplanar PCBs, pg-TEQ/L	0.15

It can be observed from the above table that leachate generated from waste consisting of mainly incinerated residue was characterized by its very low concentrations in COD and NH₃-N but relatively high concentrations in salinity and persistent organics, such as dioxins and endocrine disrupting chemicals.

Given the low BOD₅, COD and NH₃-N concentrations, leachate treatment methods being currently adopted in NENT Landfill, namely aerobic biological treatment and ammonia stripping, may no longer be suitable for treating leachate from IWMF residue. As a worst-case scenario, the leachate from the residues may not be suitable to the bacteria in the aerobic biological treatment. Other treatment technologies such as chemical precipitation, ion exchange, reversed osmosis and membrane process should be considered instead. Similar to other IWMF overseas, suitable engineering design and precautionary measures (such as liner and treatment facility) will be provided in the market such that the effluent can fulfill the current discharge criteria. With the anticipated development in advance technology in the next 10 years, more options for advanced treatment facilities can be made available.

Given the uncertainty of the implementation programme for IWMF and on the exactness of data on compositions/volume and final disposal location for the residue, the impact on the future leachate treatment facilities at NENT Landfill Extension will be assessed when the actual framework is better defined. If NENT Landfill Extension is finally considered as a suitable site for the disposal of IWMF residues, pilot and bench-scale tests are recommended (to be included in the NENT Landfill Extension Contract) before any full-scale operation. Leachate test for any hazardous waste/ash, such as Toxicity Characteristic Leaching Procedure (TCLP), should be conducted before dumping on the NENT Landfill Extension.

5.6.6 Hazardous Waste Diverted from Other Landfills

In 2005, HK generated a total waste of 17,679 tonnes per day (tpd) with 95 tpd (0.5%) classified under hazardous wastes. Leachate generated from hazardous waste will therefore not have significant impact on the treatment capacity of the treatment works.

The NENT Landfill Extension and the leachate treatment facilities have also been designed to handle the hazardous wastes and the associated leachate. As a worst-case scenario, other than construction waste and municipal waste, NENT Landfill Extension may also receive hazardous waste (e.g. animal carcasses, asbestos waste, stabilised chemical waste, clinical waste, CWTC stabilised residue and dewatered sludge) diverted from other landfills (e.g. SENT) after their closure. The handling and disposal of these special wastes will follow the Waste Disposal Ordinance (Cap. 354). The amount of hazardous wastes from other landfills is anticipated to be small and co-disposal with typical municipal waste will be adopted. In addition, an impermeable mineral layer, a drainage layer of at least 0.5 m and at least 1m top soil will form the capping. Hence, the leakage of the hazardous wastes is not anticipated.

The leachate generated from the hazardous wastes will be mixed with those of municipal waste in the landfill cell. Leachate generated from the landfill may also contain hazardous material and would be diluted by the leachate from domestic waste as well as the contaminated surface water. Leachate will then be transported to the leachate treatment facilities for treatment. The collected leachate will be temporarily stored in buffer lagoons as equalization tanks, and then diverted to thermally driven ammonia stripping process for the removal of high ammonia concentration. After the stripping process, the leachate will be diverted to SBR basin for COD, BOD₅ and SS removal. After completing these treatment processes, the effluent will be discharged to the buffer lagoon for onward pumping to Shek Wu Hui Sewage Treatment Works. Given that the discharge limit of the leachate treatment facilities will be maintained, the impact of leachate on the environment will be minimal.

5.6.7 Sewage Impact

5.6.7.1 Construction Phase

Sewage generated due to the presence of site staff and construction workers would have the potential to cause water pollution if it was to be discharged directly into adjacent water bodies without appropriate treatment. The characteristics of sewage include high level of BOD₅, Ammonia and E. coli counts. Temporary sanitary toilets will be specified in the contract requirements.

5.6.7.2 Operation Phase

Sewage will be generated from both staff working on active construction/tipping area and staff working in the site office. Permanent toilet with flushing system will be provided at the site office. The sewage collected will be conveyed to public sewerage network leading to the SWHSTW. The DBO Contractor will provide temporary sanitary toilets for their own staff. These toilets will be cleaned on a regular basis to comply with the relevant sanitary requirements. For other areas on the site where no temporary toilets are provided, workers on the sites will use the toilets at the site office. The characteristics of the sewage generated during this stage will be very much similar to that generated during construction stage. No sewage impact on the surrounding water systems is anticipated during operation phase.

5.6.7.3 Restoration and Aftercare Phases

Sewage will be generated from staff working on the site and site office during restoration and aftercare phases. Similar to the operation phase, all site staff will use the permanent toilet provided at the site office. No sewage impact on the surrounding water systems is anticipated.

5.6.7.4 Impact on Existing Sewerage Infrastructure System

Given that the existing NENT Landfill will be closed prior to the operation of the NENT Landfill Extension, increase in leachate generation rate is not expected (ceiling rate kept at 1200m³/day as stated in 5.6.4.3). Therefore, the existing leachate treatment plant as well as the sewerage infrastructure system downstream will not be overloaded.

5.7 Cumulative Impacts

Under the current design, the NENT Landfill Extension will not be in operation before the existing NENT Landfill is full (i.e. the two landfills will not receive waste at the same time). Cumulative impact due to concurrent operation of the two landfills will therefore not be an issue.

Due to the topography of the existing landfill and the future extension, the two landfills are situated in two different catchments. The surface runoff generated in the existing landfill will fall toward Kong Yiu River while surface runoff generated in the extension site will fall toward Ping Yuen River. Cumulative impact due to surface water will therefore consider unlikely.

Cumulative impact on leachate treatment would, however, occur during the restoration of the existing landfill and operation of the landfill extension. During restoration of the existing landfill, small amount of leachate will still be generated due to the decomposition of waste body. However, the amount of leachate generated would be greatly reduced in compare with an active landfill. See Appendix 5.2 for the estimation of leachate. In the landfill extension, given the fact that the landfill extension will be developed in phases, leachate generated in the early stage of the landfill extension would be small. The existing leachate treatment system and new on-site treatment facilities (if any) will be designed to cater leachate from both existing landfill and its extension. Cumulative impact during the restoration of existing landfill and operation of landfill extension is considered minimal.

Besides, there is contract provision in the extension site to provide temporary leachate storage to cater one-off event during extreme rainfall incident. The size of the storage tank will be sufficient to cater the contaminated surface water for corrective action. The quantity of leachate discharged to the on-site leachate treatment plant will be controlled and will not overload the treatment system.

During the restoration of existing landfill, regular monitoring on leachate flows will be carried out, excess leachate generated in the restored landfill is not anticipated. Hence the cumulative impact will be minor.

The fact that no adverse cumulative water quality impact arising from the phased development of the existing NENT Landfill has been recorded. It is suggested that cumulative water quality impact resulting from concurrent construction and operation activities at NENT Landfill Extension will not be an issue, given the proper implementation of the site drainage management system as mentioned in Sections 5.8.1.1 and 5.8.2.3 below.

In addition, given a proper management and containment of the surfacing water runoff at the NENT Landfill Extension will be provided, no cumulative impact on the WSRs (in particular Lin Ma Hang – with no physical encroachment in catchment area) is expected.

5.8 Precautionary Measures

5.8.1 Construction Phase

5.8.1.1 Construction Runoff

In accordance with the Practice Note for Professional Persons on Construction Site Drainage, Environmental Protection Department, 1994 (ProPECC PN 1/94), and DSD Technical Circular TC14/2000, construction phase precautionary measures, where appropriate, will include the following:

· At the start of site establishment, perimeter cut-off drains to direct off-site water around the site will be constructed with internal drainage works and erosion and sedimentation control facilities implemented. Channels (both temporary and permanent drainage pipes and culverts), earth bunds or sand bag barriers will be provided on site to direct stormwater to silt removal facilities. The design of the temporary on-site drainage system will be undertaken by the DBO Contractor prior to the commencement of construction.

· The dikes or embankments for flood protection will be implemented around the boundaries of earthwork areas. Temporary ditches will be provided to facilitate the runoff discharge into an appropriate watercourse, through a silt/sediment trap. The silt/sediment traps will be incorporated in the permanent drainage channels to enhance deposition rates.

· The design of efficient silt removal facilities will be based on the guidelines in Appendix A1 of ProPECC PN 1/94, which states that the retention time for silt/sand traps should be 5 minutes under maximum flow conditions. Sizes may vary depending upon the development phases and associated flow rate, but for a flow rate of 0.1 m³/s a sedimentation basin of 30m³ would be provided and for a flow rate of 0.5 m³/s the basin would be 150 m³. The detailed design of the sand/silt traps will be undertaken by the DBO Contractor prior to the commencement of construction.

· Construction works will be programmed to minimize surface excavation works during the rainy seasons (April to September). All exposed earth areas will be temporary covered as soon as possible after earthworks have been completed. If excavation of soil cannot be avoided during the rainy season, or at any time of year when rainstorms are likely, exposed slope surfaces will be covered by tarpaulin or other means.

· The overall slope of the site will be kept to a minimum to reduce the erosive potential of surface water flows, and all trafficked areas and access roads protected by coarse stone ballast.

· All drainage facilities and erosion and sediment control structures will be regularly inspected and maintained to ensure proper and efficient operation at all times and particularly following rainstorms. Deposited silt and grit will be removed regularly and disposed of by spreading evenly over stable, vegetated areas.

· Measures will be taken to minimise the ingress of site drainage into excavations. If the excavation of trenches in wet periods is necessary, they will be dug and backfilled in short sections wherever practicable. Water pumped out from trenches or foundation excavations will be discharged into storm drains via silt removal facilities.

· Open stockpiles of construction materials (for example, aggregates, sand and fill material) of more than 50m³ will be covered with tarpaulin or similar fabric during rainstorms. Measures will be taken to prevent the washing away of construction materials, soil, silt or debris into any drainage system.

· Manholes (including newly constructed ones) will always be adequately covered and temporarily sealed so as to prevent silt, construction materials or debris being washed into the drainage system and storm runoff being directed into foul sewers.

· Precaution measures will be taken at any time of year when rainstorms are likely, actions to be taken when a rainstorm is imminent or forecasted, and actions to be taken during or after rainstorms are summarised in Appendix A2 of ProPECC PN 1/94. Particular attention will be paid to the control of silty surface runoff during storm events, especially for areas located near steep slopes.

· All vehicles and plant will be cleaned before leaving the construction site to ensure no earth, mud, debris and the like is deposited on roads. An adequately designed and sited wheel washing facilities will be provided at every construction site exit where practicable. Wash-water should have sand and silt settled out and removed at least on a weekly basis to ensure the continued efficiency of the process. The section of access road leading to, and exiting from, the wheel-wash bay to the public road will be paved with sufficient back fall toward the wheel-wash bay to prevent vehicle tracking of soil and silty water to public roads and drains.

· Oil interceptors will be provided in the drainage system downstream of any oil/fuel pollution sources. The oil interceptors will be emptied and cleaned regularly to prevent the release of oil and grease into the storm water drainage system after accidental spillage. A bypass will be provided for the oil interceptors to prevent flushing during heavy rain.

· Construction solid waste, debris and rubbish on site will be collected, handled and disposed of properly to avoid water quality impacts.

· All fuel tanks and storage areas will be provided with locks and sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank to prevent spilled fuel oils from reaching water sensitive receivers nearby.

· In order to prevent the pollution risks arising from works area (waste reception area) and haul roads of NENT Landfill, intercepting bund or barrier along the roadside will be constructed.

By adopting the above precautionary measures with Best Management Practices (BMPs) it is anticipated that the impacts of runoff from the construction site will be reduced to satisfactory levels before discharges.

The construction runoff discharged from the landfill site shall fully comply with the standards stated in Section 5.2, otherwise the discharge shall be collected and conveyed to the on-site leachate treatment and eventually discharged to Shek Wu Hui Sewage Treatment Works.

5.8.1.2 Sewage from Workforce

Portable chemical toilets and sewage holding tanks will be provided for handling the sewage generated by the workforce. A licensed contractor will be employed to provide appropriate and adequate portable toilets and be responsible for appropriate disposal and maintenance.

Notices will be posted at conspicuous locations to remind the workers not to discharge any sewage or wastewater into the nearby environment during the construction phase of the Project. Regular environmental audit on the construction site can provide an effective control of any malpractices and can achieve continual improvement of environmental performance on site. It is anticipated that sewage generation during the construction phase of the Project would not cause water quality impact after undertaking all required measures.

5.8.1.3 Accidental Spillage of Chemical

Any service workshops and maintenance facilities will be located within a bunding area, and sumps and oil interceptors will be provided. Maintenance of equipment involving activities with potential for leakage and spillage will only be undertaken within the areas appropriately equipped to control these discharges.

5.8.2 Operation Phase

5.8.2.1 Contingency Plan on Accidental Leakage of Leachate

Existing Contingency Plan for Groundwater Contamination

Under the existing contingency plan (under Landfill Monitoring Plan) for NENT Landfill, groundwater within and around the site will be monitored in accordance with the groundwater monitoring programme proposed in the EM&A Manual. The parameters to be monitored include groundwater level and groundwater quality. The objective of the monitoring programme is to ensure that the trigger levels in Table 5.11 below are not exceeded.

Table 5.11: Trigger levels for groundwater monitoring

Parameter	Trigger Level
Ammonia Nitrogen	5 mg/L
COD	30 mg/L

In the event that the above trigger levels are exceeded, the DBO Contractor will implement a Corrective Action Programme, which shall include:

· groundwater interception and diversion; and

· groundwater extraction (by active pumping of leachate from leachate and groundwater collection layers) and treatment prior to discharge.

The existing Contingency Plan is comprehensive and well-developed. It will be used as basis for developing the Contingency Plan for the extension site.

Proposed Modifications to Contingency Plan for Groundwater Contamination

Potential actions to be taken in case of identification of groundwater contamination should also include:

· Installation of additional ground-water monitoring well;

· Increased frequency of ground-water quality testing;

· Installation of ground-water extraction wells to remove contaminated groundwater for treatment;

· Installation of subsurface barriers, such as bentonite;

· Detailed investigation of the potential impact to be performed within six months of the first detection of the justified impact.

Contingency Plan for Surface Water Contamination

Surface water monitoring will be conducted to keep the ammonia-nitrogen and COD below the following trigger levels:

· Ammonia nitrogen: 0.5 mg/L

· COD: 30 mg/L

· suspended Solid: 20 mg/L.

In the event that any one of the above parameters was exceeded, the landfill operation should implement a Corrective Action Programme. The key elements shall include:

· Surface water interception and temporary storage of the contaminated surface water;

· Installation of surface barriers, such as sand bund along the surface water channel / site boundary to avoid overflow off-site.

· Active pumping of the contaminated surface water to the leachate lagoons / leachate recirculation system / on-site leachate treatment plant;

· Additional monitoring locations will be selected to determine the pollution source;

· Installation of surface barriers, such as intercepting bund to separate the active and inactive tipping area.

· Change of working methods to prevent surface water contamination; and

· Implementation of diversionary works.

5.8.2.2 Erosion Control

There are lots erosion control methods available. The DBO Contractor shall devise a soil erosion control plan during the detailed design stage so as to define the site-specific measures and procedures (including the specific operation plan, implementation frequency, monitoring procedures, maintenance schedules, etc). Such requirement shall be specified in contract documents. The followings summarize the most popular erosion control methods for reference:

a. Preserve Natural Vegetation

This Best Management Practices will involve preserving natural vegetation to the greatest extent possible during the construction process, and after construction where appropriate. Maintaining natural vegetation is the most effective and inexpensive form of erosion prevention control.

b. Provision of Buffer Zone

A buffer zone consists of an undisturbed area or strip of natural vegetation or an established suitable planting adjacent to a disturbed area that reduces erosion and runoff. The rooted vegetation holds soils acts as a wind break and filters runoff that may leave the site.

c. Seeding (Temporary/Permanent)

A well-established vegetative cover is one of the most effective methods of reducing erosion. Vegetation should be established on construction sites as the slopes are finished, rather than waiting until all the grading is complete. Besides, Hydroseeding will be applied on the surface of stockpiled soil and on temporary soil covers for inactive tipping areas to prevent soil erosion during rainy season.

d. Ground Cover

Ground Cover is a protective layer of straw or other suitable material applied to the soil surface. Straw mulch and/or hydromulch are also used in conjunction with seeding of critical areas for the establishment of temporary or permanent vegetation. Ground cover provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures.

e. Hydraulic Application

Hydraulic application is a mechanical method of applying erosion control materials to bare soil in order to establish erosion-resistant vegetation on disturbed areas and critical slopes. By using hydraulic equipment, soil amendments, mulch, tackifying agents, Bonded Fiber Matrix (BFM) and liquid co-polymers can be uniformly broadcast, as homogenous slurry, onto the soil. These erosion and dust control materials can often be applied in one operation.

f. Sod

Establishes permanent turf for immediate erosion protection and stabilizes rainageways.

g. Matting

There are numerous erosion control products available that can be described in various ways, such as matting, blankets, fabric and nets. These products are referred as matting. A wide range of materials and combination of materials are used to produce matting including, but not limited to: straw, jute, wood fiber, coir (coconut fiber), plastic netting, and Bonded Fiber Matrix. The selection of matting materials for a site can make a significant difference in the effectiveness of the Best Management Practices.

h. Plastic Sheeting

Plastic Sheeting will provide immediate protection to slopes and stockpiles. However, it has been known to transfer erosion problems because water will sheet flow off the plastic at high velocity. This is usually attributable to poor application, installation and maintenance.

i. Dust Control

Dust Control is one preventative measure to minimize the wind transport of soil, prevent traffic hazards and reduce sediment transported by wind and deposited in water resources.

Apart from above erosion control methods, it should be noted that the greater the volume and velocity of surface water runoff on landfill sites, the more sediment and other pollutants are transported to streams. Diverting runoff away from exposed soils can greatly reduce the amount of soil eroded from a site. Decreasing runoff velocities reduces erosion and the amount of pollutants carried off-site. For the division of run-off from exposed areas, the common practices include the use of pipe slope drains and diversion swales. For the reduction of runoff velocities, the common practices will include check dams and sediment traps.

5.8.2.3 Surface Water Drainage System

A temporary surface water drainage system to manage runoff will be adopted during construction and operation. This system will consist of channels as constructed around the perimeter of the site area. This system will collect surface water from the areas of higher elevations to those of lower elevations and ultimately to the point of discharge. Erosion will therefore be minimised.

The temporary surface water management system will include the use of a silt fence around the soil stockpile areas to prevent sediment from entering the system. Regular cleaning will be carried out to prevent blockage of the passage of water flow in silt fence.

Intermediate drainage system will be installed for filled cell/phase. The major purpose of the intermediate drainage system is to prevent the clean surface water run-off from the filled phases coming into contact with the waste mass in active cell and to prevent excessive surface water infiltration through the intermediate cover, thus contribute to increasing volume of leachate.

The intermediate drainage system will collect the clean surface water run-off and divert it to the permanent discharge channels connected to the public drainage system.

In addition, surface flow from the haul road (especially near the wheel washing facility) will be collected to a dry weather flow interceptor and conveyed to the leachate treatment plant for further treatment.

The surface flow discharge from the landfill site shall fully comply with the standards stated in Section 5.2, otherwise the contaminated surface flow shall be collected and disposed of to the on-site leachate treatment plant and eventually discharged to the Shek Wu Hui Sewage Treatment Works.

5.8.2.4 Monitoring

Monthly monitoring of the surface water discharges will form part of the environmental monitoring programme. The results of the monitoring will show if contamination of surface water by leachate is occurring. If surface water is contaminated, further monitoring will be undertaken to locate the source of contamination, and remediation measures will then be carried out. Once the source of contamination has been identified, various remediation measures will be considered, for example, conveying the contaminated surface water runoff directly to the leachate treatment plant.

In addition, monitoring of the surface water quality at the upstream of Lin Ma Hang Catchment is also recommended in order to ensure there is no leachate leakage during operation phase.

Detailed monitoring plan including sampling locations, parameters and frequency are presented in the EM&A Manual for this Project.

5.8.3 Restoration and Aftercare Phases

A permanent surface water drainage system is designed to convey the water running through the final restoration slopes to perimeter channel as quick as possible.

The design of the diversion channels located on the final cover is such that their construction involves no disturbance below the cap cover soil.

5.9 Residual Impacts

Construction site runoff will be managed in accordance with the guidelines specified in ProPECC PN 1/94, no residual water quality impact during construction phase is anticipated.

All site staff will either use portable toilets provided on site or the permanent toilets provided at the site office. No residual sewage impact on the surrounding water systems is anticipated.

The rate of leachate seepage is assessed to be negligible. With the implementation of the contingency plan on leachate seepage, no residual groundwater quality impact is anticipated.

The surface drainage management system is designed to collect, carry and discharge the clean surface water run-off from NENT Landfill Extension and its immediate surroundings to the public drainage network. The discharge of surface water from the landfill drainage system will not have any adverse impacts on the water quality of the surrounding streams and rivers.

The declination of groundwater table within and downstream of the site is considered the only residual hydrological impact. The declination in groundwater level may affect the supply of irrigation water. However, it will not induce insurmountable water quality impact. With the implementation of the measures recommended in Section 5.6.3.8, the impact on irrigation water will be minimized.

5.10 Conclusion

The potential water quality impacts of the Project have been assessed. No overflow or discharge of raw leachate, treated leachate and contaminated surface runoff from the tipping face to Ping Yuen River and its tributaries will be allowed under any circumstances.

With proper implementation of construction site runoff control measures, adverse water quality impact during construction phase is not expected.

Under normal installation condition, the rate of leachate seepage is potentially 0.06 litres per hectare per day, which is considered to be insignificant. With the implementation of the measures proposed in the Contingency Plan on Accidental Leakage of Leachate (including active pumping of leachate from leachate and groundwater collection layers to the on-site leachate treatment plant), impact on the groundwater quality is insignificant. Nevertheless, monthly monitoring of the surface and groundwater discharges will form part of the EM&A programme. If groundwater or surface water is contaminated, further monitoring will be undertaken to locate the source of contamination, and remediation measures will then be carried out.

Assessment results on groundwater flow impact shows that the groundwater level beneath the site may potentially fall by 1.5m over the operational lifetime of the landfill extension. Ground water levels at Wo Keng Shan could fall by 0.5m to 1m over the operational lifetime of the landfill extension whereas a drop of 0.6m can be expected at Ping Yeung over the same period. However, it should be noted the groundwater table downstream will be recharged by adjacent catchments and therefore the potential impact predicted above would be conservative. A number of measures to mitigate the potential loss of groundwater yields have also been proposed (including provision of water supply for irrigation to affected downstream villages). The draw down of groundwater level will not induce insurmountable water quality impact.

The amount of leachate generated from the NENT Landfill Extension has been estimated. The average peak leachate generated from both landfills is estimated to be 1,200 m³/day, which is within the treatment capacity of the existing leachate treatment plant. The maximum peak leachate generated from both landfills during a severe storm event is estimated to be 1,500m³/day, and new temporary storage lagoons will be constructed to store the additional leachate for further treatment. It is therefore concluded that no adverse impact on the downstream sewerage network is expected.

Sewage will be generated by workforce on site throughout the construction, operation, restoration and aftercare stages. Adverse impact is not anticipated as both portable toilets and permanent toilets at the site office will be provided to collect all sewage generated.

If IWMF would be commissioned around the same time as the NENT Landfill Extension, NENT Landfill Extension will be receiving residues from IWMF. The waste as well as the leachate characteristics will vary significantly from the existing ones. Given the uncertainty of the implementation programme for IWMF and on the exactness of data on compositions/volume and final disposal location for the residue, the impact on the future leachate treatment plant at NENT Landfill Extension will be assessed when the actual framework is better defined. If NENT Landfill Extension is finally considered as a suitable site for the disposal of IWMF residues, pilot and bench-scale tests are recommended (to be included in the NENT Landfill Extension Contract) before any full-scale operation. Leachate test for any hazardous waste/ash, such as Toxicity Characteristic Leaching Procedure (TCLP), should be conducted before dumping on the NENT Landfill Extension. The leachate generated from the hazardous wastes will be mixed with those of municipal waste in the landfill cell. Leachate generated from the landfill may also contain hazardous material and would be diluted by the leachate from domestic waste as well as the contaminated surface water. Leachate will then be transported to the leachate treatment works for NH₃, COD, BOD₅ and SS removal. After completing these treatment processes, the effluent will be discharged to the buffer lagoon for onward pumping to Shek Wu Hui Sewage Treatment Works. These processes are similar to the treatment process being adopted by the existing NENT Landfill. Given that the discharge limit of the leachate treatment will be maintained, the impact of leachate on the environment will be minimal.

Given that the landfill extension will only be in operation after the closure of the existing landfill, no cumulative water quality impact due to the construction / operation of the two landfills will occur. Nonetheless, cumulative impact will occur when restoration in existing landfill and operation in the extension take place concurrently. As the two landfills fall into different drainage catchments (NENT Landfill Extension falls within Ping Yuen River Catchment while the existing NENT Landfill falls within Kong Yiu River Catchment), with the proper implementation of leachate management system as proposed in this chapter, no adverse cumulative impact is anticipated. The leachate management system includes :

- Contract provision to provide leachate storage tank for flow balancing and for detention before on-site leachate treatment.

- Sizing of the storage tank to be sufficient to cater the contaminated surface water for corrective action.

- Design capacity of the leachate treatment plant shall be planned to accommodate the worst-case scenarios and cater for treating leachate from both landfills and contaminated surface water as stated in the Contingency Plan on Accidental Leakage of Leachate.

- Perimeter bund shall be provided around the tipping face to prevent overflow during extreme rainfall.

5.11 Reference

1. J.P. Giroud and R. Bonaparte, "Leakage Through Liners Constructed with Geomembranes, Part I", Geomembrane Liners, Geotextiles and Geomembranes, 8, 1: 27-67, 1989

2. P.R. Schroeder, T.S. Dozier, P.A. Zappi, B.M. McEnroe, J.W. Sjostrom, and R.L. Peton, " The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering Documentation for Version 3", EPA/600/R-94/168b, US. Environmental Protection Agency, Risk Reduction Engineering Laboratory, Cincinnati, OH.(1994)

3. J.P. Giroud, "Equations for Calculating the Rate of Liquid Migration Through Composite Liners Due to Geomembrane Defects", Geosynthetics International, Vol. 4, Nos. 3-4, pp.335-348, 1997.

4. Giroud, J.P., King, T.D., Sanglerat, T.R., Hadj-hamou, T. and Khire, M.V., 1997, “Rate of Liquid Migration Through Defects in a Geomembrane Placed on a Semi-Permeable Medium”, Geosynthetics International, Vol. 4, Nos. 3-4, pp. 349-372.

5. Ruhl, J. L., and Daniel, D.E. (1997). “Geosynthetic clay liners permeated with chemical solutions and leachate.” J. Geotech. and Geoevnvir. Engrg., ASCE, 123(4), 369-381.

6. Gary J. Foose, Craig H. Benson, and Tuncer B. Edil (2001). “Predicting leakage through composite landfill liners.” J. Geotech. and Geoevnvir. Engrg., ASCE, 127(6), 510-520.

7. K. Ushikoshi et al. (2002). ”Leachate treatment by the reverse osmosis system” Desalination, 150 (2002), 121-129.

6 Waste Management Implications

6.1 Introduction

This chapter presents the findings of the assessment of waste management implications arising from the NENT Landfill Extension during the construction, operation, restoration and aftercare phases. Opportunities for waste avoidance, minimisation, reuse, recycling and disposal were examined. With the construction material import/export balancing design approach and the appropriate mitigation measures implemented during the different phases of the Project, potential environmental impacts associated with waste management would be insignificant.

The waste management implication assessment has been conducted in accordance with the requirements of Annexes 7 and 15 of the TM-EIAO and Clause 3.4.4 of the EIA Study Brief for the Project.

6.2 Legislation, Standards and Guidelines

The relevant legislation and associated guidance notes applicable to the study for the assessment of waste management implications include:

· Waste Disposal Ordinance (Cap.354) and subsidiary Regulations;

· Environmental Impact Assessment Ordinance (Cap 499) and subsidiary Regulations;

· Land (Miscellaneous Provisions) Ordinance (Cap 28);

· Public Health and Municipal Services Ordinance (Cap 132);

· Hong Kong Planning Standards and Guidelines (HKPSG), Chapter 9 – Environment;

· A Policy Framework for the Management of Municipal Solid Waste (2005-2014);

· Waste Reduction Framework Plan, 1998 – 2007, Planning Environment and Lands Branch, Government Secretariat;

· Code of Practice on the Packaging, Labeling and Storage of Chemical Wastes, EPD (1992);

· Environment, Transport and Works Bureau Technical Circular (Works) (ETWB TC(W)) No. 33/2002 Management of Construction and Demolition Material Including Rock;

· ETWB TC(W) No.31/2004 Trip Ticket System for Disposal of Construction and Demolition Materials;

· ETWB TC(W) No. 19/2005 Environmental Management on Construction Sites;

· WBTC No. 12/2002, Specifications Facilitating the Use of Recycled Aggregates;

· WBTC Nos. 25/99, 25/99A and 25/99C. Incorporation of Information on Construction and Demolition Material Management in Public Works Subcommittee Papers; and

6.3 Assessment Methodology

The waste management hierarchy principle was adopted following the order of preference: avoidance > minimisation > reuse > recycling > treatment > disposal. Opportunities for reducing waste generation have been critically assessed for:

· Avoiding or minimising waste generation through changes in the design;

· Implementing management practices to promote segregation of wastes; and

· Reuse and recycling.

Waste types and quantities estimation are made reference to the existing capacities of the waste disposal facilities. Disposal options for each waste type consider the environmental implications of handling, collection and disposal of such wastes.

The assessment of waste management implication comprises the following:

· Analysis of activities and waste generation to identify the quantity, quality and timing of the waste arising as a result of the construction, operation, restoration and aftercare activities of the Project, based on the sequence and duration of these activities:

- Construction and operation phases – excavated construction materials from site preparation; chemical waste arising from maintenance of plant and equipment; sludge from leachate treatment plant; general waste from daily activities; and

- Restoration and aftercare phases – chemical waste arising from maintenance of plant and equipment; sludge from leachate treatment plant; general waste from daily activities.

· Proposal for waste management:

- Prior to considering the disposal options for various types of wastes, opportunities for reducing waste generation, on-site or off-site re-use and recycling are fully evaluated. Measures which can be taken in the planning and design stages e.g. by modifying the design approach and in the construction stage for maximising waste reduction were individually considered;

- After considering all the opportunities for reducing waste generation and maximising re-use, the types and quantities of the wastes required to be disposed of as a consequence are estimated and the disposal options for each type of waste described in detail. Pretreatment processes for slurry before disposal are addressed in details. The disposal method recommended for each type of waste has been considered for the result of the assessment below; and

- The impact caused by handling (including labelling, packaging and storage), collection, and reuse/disposal of wastes is addressed in detail and appropriate mitigation measures have been proposed. The assessment covers the potential hazard, air and odour emissions, noise, wastewater discharge and public transport.

6.4 Identification and Evaluation of Waste Management Implications

6.4.1 Analysis of Activities and Waste Generation

6.4.1.1 Construction and Operation Phases

During the construction and operation phases between 2009 and 2019, a variety of wastes will be generated including excavated construction materials, chemical waste, general refuse and sludge from leachate treatment plant.

Excavated Construction Material

Given the remote location of the site, the site formation works will be based on a material balance approach and no significant import or export of soil materials is expected. To construct the landfill bowl, ~6.2Mm³ of construction materials will be excavated from the existing Stockpile and Borrow Area, ~2.2Mm³ of which will be used as fill material for site formation while the remaining will be stockpiled on-site for future use during operation phase as daily cover and final capping materials. 6-1

The DBO Contractor will be responsible for sorting construction materials into inert and non-inert portions. Inert portion of construction materials should be reused on-site as far as practicable, whilst any non-inert portion should be reused whenever possible and be disposed of as a last resort. The contract documents should specify that no excavated materials are to be removed from the site.

Chemical Waste

The Waste Disposal (Chemical Waste) (General) Regulation defines chemical waste as any substance being scrap material or unwanted substances specified in its Schedule 1, and provides a complete list of such substances. Substances likely to be generated by construction and operation activities would mainly arise from the maintenance of plants and equipment. These include:

· Scrap batteries or spent acid/alkali;

· Used engine oils, lubricating and hydraulic fluids and waste fuel;

· Spent mineral oils/ cleaning fluids from mechanical machinery; and

· Spent solvents/ solutions, some of which may be halogenated, from equipment cleaning activities.

The volume of chemical waste arising will depend upon the total number of plants and equipment and the level of maintenance. Chemical waste data of the existing NENT Landfill is benchmarked for a conservative estimation of waste quantity arising from the future extension. The typical quantities of chemical waste arising during construction and operation phases of existing NENT Landfill in 2005 are summarised in Table 6.1.

Table 6.1: Estimated quantities of chemical waste arising during construction and operation phases of NENT Landfill Extension

Description	Existing NENT Landfill (in 2005)	NENT Landfill Extension (Estimated for 10 years)
Waste battery	50 pieces	500 pieces
Spent lube oil filters and rag from mobile plants	150kg	1,500kg
Spent lube oil from routine operation	30,000L	300,000L
Spent acid from laboratory	80L	800L

General Refuse

The general refuse during the construction and operation of the existing NENT Landfill encompasses a wide variety of waste, e.g. site office activities, kitchen refuse, packaging of equipment and construction materials, maintenance of plants and equipment, etc, and the total volume would depend on the employed workforce on-site.

The typical quantities of general refuse arising from ~100 staff during the construction and operation phases of the existing NENT Landfill was 280 tonnes in 2005.

Assuming the number of staff during the construction and operation of future NENT landfill extension would be similar, the total quantity of general refuse arising from the 10-year construction and operation phases is ~2,800 tonnes.

Sludge

Though it is preferable to use the existing leachate treatment plant for the future landfill extension, a new treatment plant with a capacity of 1,200 m³ per day is planned as a worst-case scenario.

The typical quantity of sludge arising from the leachate treatment plant during the construction and operation phases of the existing NENT Landfill was 3,270 m³ in 2005.

Assuming the same treatment capacity (i.e. 1,200 m³ per day) throughout the 10-year of construction and operation phases of the future NENT Landfill Extension, the total quantity of sludge generated would be ~32,700 m³.

6.4.1.2 Restoration and Aftercare Phases

During the restoration and aftercare phases between 2019 and 2049, chemical waste, sludge from leachate treatment plant, and general refuse will be the major waste stream anticipated. The DBO Contractor should also consider the reuse and recycling of wastes as far as practicable, thereby reducing the level of generation.

Chemical Waste

With reference to the existing NENT Landfill, the estimated quantity of chemical waste generated from the restoration and aftercare phases is assumed to be approximately 30% of that during construction and operation phases of NENT Landfill Extension due to the substantial reduction of number of plants and equipment on-site, as summarised in Table 6.2.

Table 6.2: Total estimated quantity of chemical waste arising during restoration and aftercare phases of NENT Landfill Extension

Description	Construction & Operation (Estimated for 10 years)	Restoration & Aftercare (Estimated for 30 years)
Waste battery	500 pieces	450 pieces
Spent lube oil filters and rag from mobile plants	1,500kg	1,350kg
Spent lube oil from routine operation	300,000L	270,000L
Spent acid from laboratory	800L	720L

General Refuse

Based on the above estimated quantity of general waste (~2,800 tonnes) for 100 workers during the 10-year construction and operation phases and assuming on average ~20 workers would also be present on site for 6 days a week during the 30-year restoration and aftercare phases, the total general refuse arising would be ~1,680 tonnes.

Sludge

The quantity of leachate generated from the existing landfill during restoration and aftercare phases is estimated to be ~300m³/day. On pro-rata from the estimated quantity of sludge in section 6.4.1.1, the total sludge arising from the 30 years of restoration and aftercare phases would be ~25,000 m³.

6.4.2 Waste Management Proposal

6.4.2.1 Construction and Operation Phases

Excavated Construction Materials

Although significant amount of excavated construction materials will be generated during site formation stage, there would be no significant import or export of soil materials. With the implementation of proper preventive and mitigation measures for handling, transport and disposal, no insurmountable environmental impact is anticipated.

It is not anticipated to have any significant quantities of excavated construction materials requiring off-site disposal. Notwithstanding this, a trip-ticket system should be put in place in accordance with ETWB TC(W) No.31/2004. Copies/counterfoils from trip-tickets (showing the quantities of construction Materials taken off-site) should be kept for record purposes.

Chemical Waste

Chemical waste can pose serious environmental, health and safety hazards if not properly managed. Such hazards include toxic effects to workers, adverse effects on water quality from spills, fire hazards, and disruption of sewage treatment plant should the chemical waste enter the sewerage system. Plant and equipment maintenance schedules should be optimised to minimise the generation of chemical wastes.

The DBO Contractor should register with EPD as a chemical waste producer. Where possible, chemical wastes (e.g. waste lubricants) should be recycled at an appropriate facility. Any transport for off-site treatment and disposal must be conducted by licensed collectors to licensed disposal facilities, e.g. Chemical Waste Treatment Centre in Tsing Yi.

Landfilling of chemical waste should be avoided. Collection receipts issued by the licensed chemical waste collector showing the quantities and types of chemical waste taken off-site and details of the treatment facility should be kept for record purposes. With the implementation of proper preventive and mitigation measures for the handling, transport and disposal of chemcial waste, no insurmountable environmental impacts would be anticipated.

General Refuse

Potential environmental impacts of general refuse include odour (if the waste is not collected frequently), windblown litter, water quality impacts (if the waste enters water bodies), and visual impacts. The refuse can also attract pests and vermin if the storage areas are not well maintained and regularly cleaned.

Waste disposal at sites other than approved waste transfer or disposal facilities can also lead to environmental impacts. Handling and disposal of general refuse should cope with the presence of peak workforce during the construction period. Receipts of refuse collection should be kept for record purposes.

Regular in-house training for the staff of the DBO Contractor should be conducted to advocate the avoidance, reduction, reuse and recycling of general refuse. Recycling bins for separate collection of paper, plastic bottles and aluminium cans should be provided. Provided that the refuse will be stored and transported in accordance with proper practices and disposed at licensed landfills, no insurmountable environmental impact is anticipated.

Sludge from Leachate Treatment Plant

Although there are rare opportunities to consider the reuse or recycling of sludge from NENT Landfill Extension, there are other ways to reduce the quantity of sludge generated.

The quantity of sludge arising from the operation of the leachate treatment plant will depend on the technology selected, namely conventional aeration lagoon, sequencing batch reactor, membrane biological filter, biological aerated filter, etc. Preference will be given to technology which generates low sludge yield, but the decision will be made by the DBO Contractor. Sludge generated will be disposed of at NENT Landfill Extension and receipts of disposal should be kept for record purposes. Co-disposal with ordinary solid waste would be adopted to reduce the average water content of the waste mass.

Provided that the sludge will be stored and transported in accordance with proper practices, no insurmountable environmental impact is anticipated.

6.4.2.2 Restoration and Aftercare Phases

Chemical Waste

With the implementation of proper preventive and mitigation measures similar to the construction management approach for the handling, transport and disposal of chemical waste, no insurmountable environmental impact is anticipated during the restoration and aftercare phases.

General Refuse

With the implementation of proper preventive and mitigation measures similar to the construction management approach for the handling, transport and disposal of general refuse, no insurmountable environmental impact is anticipated during the restoration and aftercare phases.

Sludge from Leachate Treatment Plant

With the implementation of proper preventive and mitigation measures similar to the construction management approach for the handling, transport and disposal of sludge, no insurmountable environmental impact is anticipated during the restoration and aftercare phases.

6.5 Mitigation Measures

6.5.1.1 Excavated Construction Materials

As the design has adopted a construction material balance approach, the impact on the handling, collection, transportation and disposal of construction material is insignificant. Excavated slope, stockpiled material and bund walls will be covered (e.g. by a tarpaulin) until used in order to prevent wind-blown dust during dry weather, and to reduce muddy runoff during wet weather. If any topsoil-like materials need to be stockpiled for any length of time, consideration should be given to hydroseeding of the topsoil on the stockpile to improve its visual appearance and prevent soil erosion.

6.5.1.2 Chemical Waste

Plant/ equipment maintenance schedule should be designed to optimise maintenance effectiveness and to minimise the generation of chemical wastes. Chemical waste should be properly stored and transported off-site for treatment by a licensed collector. The DBO Contractor should register with EPD as a chemical waste producer. Where possible, chemical wastes (e.g. waste lube oil) should be recycled by licensed treatment facilities.

6.5.1.3 General Refuse

All recyclable materials (separated from the general waste) should be stored on-site in appropriate containers with cover prior to collection by a local recycler for subsequent reuse and recycling. Residual, non-recyclable, general waste should be stored in appropriate containers to avoid odour. Regular collection should be arranged by an approved waste collector in purpose-built vehicles that minimise environmental impacts during transportation.

6.5.1.4 Sludge

Sludge should be collected by a licensed collector at regular intervals, to suit the operation schedule of the leachate treatment plant. The use of purpose-built sludge tankers can minimise the potential of environmental impacts during transportation.

6.6 Residual Impacts

Potential environmental impacts due to wastes generation from the Project will be controlled by means of a construction material balance approach with the implementation of appropriate mitigation measures, which are practical, proven and cost-effective for controlling potential impacts from the waste types. Provided that these measures are adopted and properly implemented during the construction, operation, restoration and aftercare phases, no residual impact is anticipated.

　　　　　　6.7 Environmental Audit

Auditing of each waste stream should be carried out periodically to determine if waste is being managed in accordance with the prescribed procedures in the Waste Management Plan (WMP). The audits will examine all aspects of waste management including waste generation, storage, recycling, treatment, transportation, and disposal. The general site inspections including waste management issues will be undertaken weekly by Environmental Team to check all construction activities for compliance with all appropriate environmental protection and pollution control measures, including those stimulated in the WMP. Monthly waste management audit will be carried out by the IEC.

6.8 Implication of IWMF Implementation

If the Integrated Waste Management Facility (IWMF) implementation were considered in Year 2010s, the incoming waste characteristics to the NENT Landfill Extension site would be altered substantially, mainly with inert incinerator ashes.

Due to its inherent characteristics changes of waste to the NENT Landfill Extension, the leachate quality might be affected with higher concentration of heavy metals. Alternative treatment technology such as metal precipitation will be considered to fulfil the requirements of discharge license.

It is anticipated that any incoming incinerator ashes would comply with the Toxicity Characteristic Leaching Procedure (TCLP) limits for landfill disposal, but the leachate quality and hence the amount of precipitate and sludge arising from the metal treatment process would be affected. Depending on the sludge treatment and disposal arrangement of the territory at time of operation of the extension landfill, non-landfill disposal or pretreatment of the sludge arising from leachate treatment works should also be considered.

Assuming metal precipitation process will be adopted in the leachate treatment works, the sludge so arising will be concentrated and hazardous in nature, special disposal arrangement will be required, e.g. disposal at designated trenches within future NENT Landfill Extension site and/or co-disposed of in designated trenches.

6.9 Conclusion

The waste management assessment has reviewed the potential impacts from various types of wastes generated from the construction, operation, restoration and aftercare stages of the NENT Landfill Extension. Through the analysis of the Project activities, the quantity, quality and timing of waste arising have been identified, including excavated materials from site preparation, chemical waste arising from maintenance of plant and equipment, general waste from daily activities, and sludge from leachate treatment plant. By adopting a material balance approach (e.g. balance cut-and-fill in site formation design, general waste from daily activities to be collected and recycled, etc.) and with the appropriate mitigation measures in place, no adverse environmental impact is anticipated.

7 Landfill Gas Hazards

7.1 Introduction

This chapter presents the risk assessment of landfill gas (LFG) hazards arising from the construction, operation, restoration and aftercare phases of the Project. Appropriate protective and precautionary measures will be implemented during various phases of the Project to control the LFG hazards to a minimum and acceptable level. No adverse impact is anticipated.

The landfill gas impact assessment has been conducted in accordance with the requirements in ProPECC PN 3/96 and EPD/TR8/97, and Clause 3.4.5 of the EIA Study Brief for the Project.

7.2 Legislation, Standards and Guidelines

The relevant legislation and associated guidance notes applicable to the study for the assessment of landfill gas implications include:

· Annex 7 and Annex 19 of the Technical Memorandum on EIAO (TM-EIAO).

· ProPECC PN 3/96 – Landfill Gas Hazard Assessment for Development Adjacent to Landfill

· EPD/TR8/97 Landfill Gas Hazard Assessment Guidance Note (LFG Guidance Note), which sets out the conditions and provide guidance to carry out LFG hazard assessment.

These guidance notes recommend that in general, assessment of LFG hazard will be required for proposed developments within the 250m consultation zone of a landfill. The landfill extension site is located within the 250m consultation zone of the existing NENT Landfill, and the Project site itself is a potential source of landfill gas generation.

7.3 Background Information

7.3.1 Desktop Study

A comprehensive desktop review study of literature information and study reports has been undertaken to appreciate the site characteristics and determine the likelihood of potential LFG impacts on the sensitive receivers. Other sources of information include topographical and geological maps, aerial photographs, utilities plan (gas, electricity, drainage, etc), information from previous ground investigations, engineering and operation details regarding NENT Landfill, gas monitoring data, visual data at landfill extension site, etc. The following documents have been reviewed:

· Development of the North East New Territories Landfill Final Report

· Environmental Review for NENT Landfill

· NENT Landfill: Supplementary Environmental Impact Assessment Final Report

· EP/SP/12/92 Development and Management of North East New Territories (NENT) Landfill monthly and annual reports (1996 to 2005)

· EP/SP/12/92 NENT Landfill – Landfill Monitoring Plan

· NENT Landfill Leachate Treatment Phase I and Village Sewerage – Final Environmental Impact Assessment Update Report

· CE45/99 Extension of Existing Landfills and Identification of Potential New Waste Disposal Sites – Final Strategic Environmental Assessment Report

· EP/SP/12/92 Development and Management of NENT Landfill Contract documents

· FP99/055 Study on the Waste Management Plan – Collection and Forecast of Waste Data – Resource Document

· EP/SP/12/92 Monthly Monitoring of Waste Phase 1, 2 and 4 Reports

· Supplementary Environmental Impact Assessment for NENT Landfill Leachate Treatment Works Final Report

· NENT Landfill Leachate Disposal Study

· CE20/2004 NENT Landfill Extension Feasibility Study – Submission Ref 008: Ground Investigation Desk Study Report

· CE20/2004 NENT Landfill Extension Feasibility Study – Submission Ref 036: Final Ground Investigation Report

7.3.2 History of Existing NENT Landfill

NENT Landfill was commissioned in 1995 and receives waste from the North East New Territories, and Kowloon Bay and Sha Tin Refuse Transfer Stations solely by road, with an overall capacity of 35 Mm³ occupying about 61 ha of land.

The site was first developed under the former Civil Engineering Department (now as Civil Engineering and Development Department)’s management and formed an initial area of the site ready for waste deposition, and also created a Stockpile and Borrow Area, where spoil from the initial excavation was stored for later re-use. It is being developed in 4 phases with construction, operation, restoration and aftercare occurring concurrently in various periods. Based on the information at the end of Year 2005, the existing landfill is being operated in Phase 2 and will be filled up by Year 2010.

About 3 Mm³ of soil and rock excavated from the development of the landfill void was stored in the Stockpile and Borrow Area that lies about 1 km to the east of the existing landfill.

The landfill includes a leachate treatment plant in the northwest corner of the site that operates at treatment capacity of 800 m³/day during the dry season (November to April) and 1,200 m³/day during wet season (May to October). The system includes six aeration / storage lagoons with associated dosing and desludging facilities, and an ammonia stripping processing plant. After treatment, the effluent is discharged via a dedicated rising main to Shek Wu Hui Sewage Treatment Works (SWHSTW) in Sheung Shui.

A LFG management system is also in place for daily operation. LFG generated from the deposited waste is pumped to a LFG utilisation plant, where the gas is used to generate electricity for site needs. LFG is also utilised as a heat source for the ammonia stripping processing plant used in the leachate treatment process. Surplus LFG will be completely burnt in the flaring system.

The contractor for the existing NENT Landfill and HKCG have conducted a pilot study to utilise methane recovered from LFG as an energy source for town gas production.

In the near future, arrangement will be put in place to export LFG from the existing NENT Landfill to Tai Po Gas plant for use as a fuel source.

7.3.3 Geology

7.3.3.1 Existing NENT Landfill Site

Drawing No. 24315/13/501 is a geological map of the existing NENT Landfill site and surrounding area, which are composed entirely of the Tai Mo Shan Formation of the Upper Jurassic Repulse Bay Volcanic Group. The formation is dominantly a lapilli to coarse-ash crystal tuff with intercalated sedimentary rocks, most of which have been metamorphosed.

The intercalations of sedimentary rocks in the Tai Mo Shan Formation are well exposed on Wong Mau Hang Shan and 200m north of Ngong Tong. These rocks are composed of mainly purple or brown fine-grained sericitic sandstone and greenish grey or reddish brown phyllite. At Heung Yuen Wai, 600m north of Wong Mau Hang Shan, the outcrops are mainly phyllite (siltstone or mudstone if in an unmetamorphosed state).

There are four faults identified in the landfill site area. Both the volcanic tuffs and metasediments contain well defined joint (discontinuity) systems, and the movement of groundwater in the bedrock materials beneath the site is controlled by the discontinuities. The depth of weathering is generally in excess of 22m on the crest of ridges surrounding the site, but the volcanic tuffs in the fault zones may be geochemically more resistant to weathering. The superficial materials comprises colluvium, alluvium and fill, which form local thin infills along the valley floors.

7.3.3.2 NENT Landfill Extension Site

A desktop and ground investigation was undertaken at the landfill extension site currently designated as the Stockpile and Borrow Area for the existing landfill (Drawing No. 24315/13/501).

The site has a variable thickness of superficial deposits across the majority of its area, comprising fill, colluvium and soils derived from in-situ weathering. The solid geology of the site comprises a mixture of volcanic tuff deposits, slightly metamorphosed volcanic tuff deposits and a small area of meta-sedimentary rock. The rockhead levels within the site are largely reflected by the topography, with low-lying valleys typically having been formed due to the presence of geological faults.

Four major geological faults are present within the site:

· Fault 1 is located along the northern boundary of the study area and striking approximately west-northwest.

· Fault 2 strikes north-northeast through the study area, most likely extending through the existing waste reception area to the south of the site and then following the topographic valley northeast from this. Previous work has recorded this fault as dipping at 80° to the southeast, with the material on the southeastern side having been downthrown.

· Fault 3 follows the approximate alignment of the existing haul road through the centre of the site area, trending west-northwest to east-southeast, and extends beyond the site boundaries.

· Fault 4 is most likely a large splay fault associated with Fault 2. The main trend of the fault is north-northeast along the topographic valley to the east of Fault 2, with a small portion trending east-northeast to the south of the haul road before joining with Fault 2 in the low-lying area within the southern part of the site.

7.4 LFG Hazard Assessment

7.4.1 Approach

Qualitative assessment on the risk of LFG hazards at the receivers has been undertaken for each of the identified source-pathway-receiver combinations. Qualitative LFG hazard assessment was undertaken following the method recommended in the LFG Guidance Note. This method is based on the “Source-Pathway-Receiver” model as described below:

· Source – location, nature and likely quantities/ concentrations of LFG which has the potential to affect the landfill extension.

· Pathway – the ground and groundwater conditions, through which LFG must pass in order to reach the landfill extension.

· Receiver – elements of the development that are sensitive to the effects of LFG.

The LFG sources, pathways and receivers are categorised for the hazard assessment. In accordance with the LFG Guidance Note, an assessment of the overall risk is made based on the risk category as summarised in Table 7.1, following determination of which category of source, pathway and receiver, the combination of existing NENT Landfill and its extension fall into during the construction, operation, restoration and aftercare stages.

For the purpose of categorising the landfill extension site, the category is based upon the highest level of risk determined for any of the potential impacts identified in Table 7.1, in which the general implications fall into different overall risk categories as shown in Table 7.2.

The findings of this LFG hazards are also adopted for the impact assessment of wildlife especially at Lin Ma Hang Stream due to accidental LFG migration from the NENT Landfill Extension site.

Table 7.1: Classification of risk category

Source	Pathway	Receiver Sensitivity	Risk Category
Major	Very Short/ Direct	High	Very high
		Medium	High
		Low	Medium
	Moderately Short/ Direct	High	High
		Medium	Medium
		Low	Low
	Long/ Indirect	High	High
		Medium	Medium
		Low	Low
Medium	Very Short/ Direct	High	High
		Medium	Medium
		Low	Low
	Moderately Short/ Direct	High	High
		Medium	Medium
		Low	Low
	Long/ Indirect	High	Medium
		Medium	Low
		Low	Very low
Minor	Very Short/ Direct	High	High
		Medium	Medium
		Low	Low
	Moderately Short/ Direct	High	Medium
		Medium	Low
		Low	Very low
	Long/ Indirect	High	Medium
		Medium	Low
		Low	Very Low

Table 7.2: Summary of general categorisations of risk

Category	Level of Risk	Implication
A	Very high (undesirable)	The type of development being proposed is very undesirable and a less sensitive form of development should be considered. At the very least, extensive engineering measures, alarm systems and emergency action plans are likely to be required.
B	High	Significant engineering measures will be required to protect the planned development.
C	Medium	Engineering measures will be required to protect the proposed development.
D	Low	Some precautionary measures will be required to ensure that the planned development is safe.
E	Very low (insignificant)	The risk is so low that no precautionary measures are required.

7.4.2 Sources

7.4.2.1 Existing Landfill

According to the EP/SP/12/92 Development and Management of NENT Landfill Monthly Reports in the recent 3 years, the LFG recovery statistics in terms of utilisation (for power generation, Ammonia Stripping Plant and other uses) and flaring processes are tabulated in Table 7.3, indicating a significant quantity of LFG generation.

The contractor of the existing NENT Landfill is required to carry out LFG monitoring during landfill operation from gas wells, boreholes and surface emissions for methane (CH₄), carbon dioxide (CO₂) and oxygen (O₂) as specified in the EP/SP/12/92 NENT Landfill – Landfill Monitoring Plan (LMP). Table 7.4 shows the compliance summary of LFG monitoring between 1996 and 2005 for CH₄, CO₂ and O₂ monitoring data extracted from the relevant EP/SP/12/92 Development and Management of NENT Landfill Monthly Reports.

Table 7.3: Recent LFG recovery statistics of existing NENT Landfill

	LFG Volume (m³)
	2001*	2002	2003	2004	2005
GenSet	567,408	2,585,544	2,500,824	2,765,592	2,639,904
Ammonia Stripping Plant	5,604,000	23,862,000	22,828,800	23,590,800	23,001,600
Flaring	144,024	1,797,024	1,201,152	1,318,224	1,556,784
Other Uses	348,000	230,400	1,528,152	1,884,408	38,544
Total recovery (m³)	6,663,432	28,474,968	28,058,928	29,559,024	27,236,832
Recovery rate (m³/hr)	3,085	3,595	3,248	3,421	3,152

* Available LFG data only for Aug, Nov & Dec in 2001

Table 7.4: Compliance summary of LFG monitoring

Year	Organic Emission (VOC)	LFG (CH₄, CO₂ and O₂)
Year	Organic Emission (VOC)	Borehole	Surface
1996	No exceedance of trigger level ⁽¹⁾	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
1997	No exceedance of trigger level	No exceedance of trigger level⁽²⁾	Abnormalities at certain locations ⁽³⁾
1998	No exceedance of trigger level⁽⁴⁾	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
1999	No exceedance of trigger level⁽⁵⁾	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2000	No exceedance of trigger level	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2001	No exceedance of trigger level	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2002	No exceedance of trigger level⁽⁶⁾	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2003	No exceedance of trigger level⁽⁷⁾	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2004	No exceedance of trigger level	No exceedance of trigger level⁽²⁾	No exceedance of trigger level
2005	No exceedance of trigger level	No exceedance of trigger level⁽²⁾	No exceedance of trigger level

Notes:

(1) Abnormality of chloroform level was recorded at one location, but it was considered erroneous and not due to landfill activities.

(2) Abnormality of CO₂ levels was recorded in some boreholes, but it was considered due to natural source and not due to landfill activities.

(3) Abnormality of flammable gas was detected at some locations in October, November and December 1997.

(4) Abnormality of methanethiols, ethanethiols and buthanethiol were recorded, but they were considered originating from external sources and not due to landfill activities.

(5) Abnormality of ethyl butanoate at one location was recorded, but it was considered originating from external source and not due to landfill activities.

(6) Abnormality was considered originating from external source and not due to landfill activities.

(7) Abnormality of propyl benzene was recorded at one location, but it was considered originating from external sources and not due to landfill activities.

(8) All the abnormalities had been reviewed by the IC and it was concluded that all of them were not originated from the existing NENT Landfill.

It is acknowledged from the NENT Landfill Monthly Reports that the only justifiable exceedances recorded for surface gas monitoring in October to December 1997 were likely due to the proximities of monitoring locations to the active tipping faces. It was also recorded that the frequency of surface gas monitoring had been increased in accordance with the corrective actions of LMP when exceedances occurred. With reference to the LFG Guidance Note, the source of LFG at the existing landfill is categorised as Medium, considering the following reasons:

· Active gas extraction system is an essential element of LFG protection measure at the existing NENT Landfill; and

· Gas control systems have been installed and proven to be effective by comprehensive monitoring which has demonstrated that there is no migration of gas beyond the landfill boundary.

The existing NENT Landfill has been incorporated with an efficient and effective LFG management system (Appendix 7.1), in which a coordinated approach to LFG monitoring, collection, extraction, flaring and utilisation is being implemented to achieve the following requirements:

· To eliminate the risk of explosion or combustion due to the presence of LFG within, below, above and inside the landfill site;

· To eliminate the hazards to flora or fauna due to toxicity or asphyxiation effect of LFG presence external to the landfill site;

· To minimise the effect of odours from LFG causing nuisance in the vicinity of the landfill site;

· To minimise the uncontrolled egress of LFG from the landfill site;

· To eliminate migration of LFG to service ducts or enclosed/confined spaces of any on-site buildings;

· To protect any temporary or permanent structures or chambers on the landfill site;

· To prevent unnecessary air ingress into the landfill;

· To prevent unnecessary build-up of LFG pressure within the landfill;

· To relieve positive pressures of LFG at the landfill boundary and near the surface;

· To facilitate the controlled extraction of LFG from the landfill;

· To facilitate the ultimate flaring and utilisation of LFG; and

· To provide signs designating hazards and precautions to avoid on-site accidents.

LFG barrier

The existing NENT Landfill was designed and constructed as a secure containment facility incorporating multi-layer composite liner systems covering the entire surface area of the site. The liner system and future final cap at the existing NENT Landfill form effective barriers against LFG migration. A final cap will be installed during the restoration stage to minimise uncontrolled egress of LFG from the landfill site, control of LFG arising from the landfill site, and minimise uncontrolled ingress of air into the landfill site and avoid any impact on the quality of potentially exploitable LFG.

LFG collection system

The LFG collection system at the existing NENT Landfill comprises vertical collection wells progressively constructed within the buried waste in conjunction with landfilling activities. The wells have radiant horizontal collection trenches throughout the depth of waste connecting with the extraction wells at regular intervals. The system also includes facilities to fulfil the performance requirements for the overall LFG management system, e.g. components to allow the coordination of LFG collection and extraction systems, prevent unnecessary build-up of LFG pressure within the landfill, relieve positive pressures of LFG at the landfill boundary and near surface, and control migration of LFG off-site.

LFG extraction system

The LFG extraction system at the existing NENT Landfill removes LFG collected from the buried waste for efficient and effective removal and conveyance to the LFG flaring and utilisation facilities. The system includes extraction wells and pipework installed within the landfill cap connecting a pumping station on-site. It also incorporates a separate collection system connected to perimeter extraction wells isolated from the main system so that it is operated independently for migration control. The system also allows LFG to be pumped in a minimum of 2 directions to provide flexibility and security of extraction, chemical duty isolating valves suitable for flow control with status indication, reservoir-/gravity drainage-type condensate traps at low points on the connecting pipework, and independent pumps for the operation of gas extraction system and perimeter control system.

LFG treatment by flaring

The LFG flaring system in the existing NENT Landfill is used for combustion of the extracted LFG such that it can be efficiently and effectively consumed, which comprises a pumping station with gas flares for heat production. LFG is extracted from the landfill and conveyed by a blower through a pipeline system to create a negative pressure for low emission controlled combustion. The wet saturated LFG is dewatered in a condensate separator so that it can be burnt off in the high temperature flare. The collected condensate is discharged into the on-site leachate treatment plant. The total LFG treated by the flaring system was 1.6 Mm³ in 2005. When required, a mobile flaring unit will be mobilised for LFG treatment.

LFG utilisation for power generation

A Genset system in the existing NENT Landfill is used for combustion of the extracted LFG such that it can be efficiently and effectively consumed for power generation. The Genset system is a water-cooled, 20-cylinder four-stroke spark ignition engine with mixture turbo-charging and a shaft output of maximum 950kW. The total LFG utilised by the Genset system was 2.6Mm³ in 2005. The system operates to prevent generation of toxic emissions by admitting especially low fuel gas/air mixture to the combustion chamber.

LFG utilisation at ammonia stripping plant

An ammonia stripping plant has been installed and operated (24 hours per day) at upstream of the biological treatment system of the leachate treatment works for advance removal of ammonia by thermal destruction with LFG as fuel. The thermal destructor thus destroys and renders harmless the LFG and ammonia LFG is introduced into to the burners after passing through a flame arrestor, which is designed to operate at a maximum LFG flow of 6,000m³ per hour with about 50% methane concentration. Total LFG utilisation at ASP was 23 Mm³ in 2005.

LFG recovery system

The contractor of the existing NENT Landfill and HKCG have conducted a pilot study to utilise methane recovered from LFG as an energy source for town gas production. The necessary facilities are currently being installed including a 19 km gas pipeline from NENT Landfill to Tai Po Gas Plant and relevant modification works to gas production equipment, and the use of LFG is anticipated to commence in 2007. Similar initiative shall be proposed for implementation in the NENT Landfill Extension Project.

LFG monitoring programme

The results from the routine and long-term LFG monitoring programme for the existing NENT Landfill operation indicate that the landfill has been operating satisfactorily and considered adequate with the proven LFG collection system and control plant in place to minimise any potential impact to the concerned sensitive receivers. The scope of LFG monitoring at the existing NENT Landfill covers the following:

· The quantity and quality of LFG extracted from the existing NENT Landfill site is monitored and the effectiveness of landfill liner system is regularly checked to prevent uncontrolled egress of LFG from the landfill site;

· The quantity of LFG emanating from the landfill site is automatically monitored at the LFG pumping station. The suction pressure at gas pumping station is monitored and the alarm will be activated when the pressure increased above or decreased below acceptable pre-determined levels;

· The well heads are installed with valves, connecting pipework, etc to connect with flow meters for monitoring of LFG extraction rates at individual heads;

· The quality of LFG is monitored by the facilities installed in the LFG pumping station, including CO₂, O₂ , nitrogen and methane concentrations, whilst the LFG composition at the well heads is monitored by gas sampling and laboratory analysis;

· The LFG flaring system is monitored for flare temperature, emissions, and differential pressure across flame arrestors;

· Routine LFG monitoring is conducted at fixed surface and borehole locations along the landfill site boundary and at potential sources of concern to ensure timely implementation of emergency and contingency measures in case LFG migration or exceedance of trigger levels; and

· Implementation of “permit to work” system, monitoring to ensure safe level of LFG concentration, and implementation of sufficient mitigation measures when entering confined spaces within the landfill site.

7.4.2.2 Future Landfill Extension

The future landfill extension itself is a source to generate significant amount of LFG during the operation and aftercare phases. LFG hazards may be prone to front-line workers within the site especially where the LFG are extracted, transported and processed. With the LFG control measures and Waste to Energy Facility in the future NENT Landfill Extension, it is anticipated that the source of LFG will be properly controlled within the site similar to the operation in existing NENT Landfill.

The NENT Landfill Extension will be designed as a containment landfill with LFG collection and management systems to eliminate any off-site migration of LFG. By virtue of the effective control and utilisation of LFG being implemented in the existing NENT Landfill based on the past monitoring data, it is likely that the NENT Landfill Extension will be designed to adopt similar LFG control measures so as to ensure future compliance of environmental and safety requirements. The source of LFG at the future landfill extension was categorised as Medium, considering the following reasons:

· Active gas extraction systems will be installed in the future landfill extension; and

· Gas control systems will be installed which are proven to be effective by comprehensive monitoring to demonstrate no migration of gas beyond the landfill boundary and specific control measures.

7.4.3 Pathways

The type of pathways can be broadly classified based on various geological features of the landfill extension site such as permeability of soil; spacing, tightness and direction of fissures/joints; topography; depth and thickness of the medium through which the gas may migrate (also affected by groundwater level); nature of strata over the potential pathway; number of media involved; and depth to groundwater table and flow patterns, etc. In general, the pathway can be broadly classified as follows depending on the distance from the landfill boundary:

· Very Short/ Direct for path length less than 50m;

· Moderately Short/ Direct for path length of 50-100m; and

· Long/ Indirect for path length of 100-250m

7.4.3.1 Within Landfill Extension Site

Natural pathways

The major concern is the presence of Faults 1 and 3 as shown in Drawing No. 24315/13/501 across the existing NENT Landfill towards the landfill extension site, which as natural pathways for preferential LFG migration. These pathways of fissured rock are less than 50m to the landfill extension site and are categorised as Very Short/ Direct according to the LFG Guidance Note.

The superficial deposits located below the formation level to the south of the landfill extension site may act as natural pathways for LFG migration towards the Waste Reception Area of the existing NENT Landfill. These pathways of unsaturated permeable strata are less than 50m to the landfill extension site and are categorised as Very Short/ Direct.

Man-made pathways

There are man-made pathways in the vicinity of the site consisting of services routes leading to the existing landfill. These pathways to sensitive receivers are classified as Very Short/ Direct towards the landfill extension site, as landfill workers could be the targets during landfill operation, piping/ conduit construction, and/or drilling/boring operation.

7.4.3.2 Outside Landfill Extension Site

Natural pathways

The presence of faults lines in NENT Landfill Extension site are identified as the potential natural pathways for potential LFG migration to the vicinities of sensitive receivers as shown in Drawing No. 24315/13/501. Fault 4 is the nearest fault line to Tong To Shan Tsuen at a distance of ~280m which is classified as “Long/Indirect“ pathway extending from the northern bound of the future landfill extension site. Mitigation measures will include installation of proper liner to act as barriers and sealing of fault line ends to prevent off-site LFG migration.

Man-made pathways

Although there are man-made pathways in the vicinity of the site consisting of services routes leading to the existing landfill, they are far from sensitive receivers and are classified as Long/ Indirect towards the adjacent occupied development.

7.4.4 Receivers

7.4.4.1 Within Landfill Extension Site

Potential receivers sensitive to LFG hazards associated with the NENT Landfill Extension include the workers and staff of NENT Landfill Extension site:

Construction Phase

· Excavation for construction of new landfill bowl;

· Deep unventilated excavations e.g. pile shafts, trenches for utility installation and basement excavations; and

· Outbuildings, sheds and temporary structures such as construction site offices.

These receivers are categorised as High Sensitivity according to the LFG Guidance Note.

Operation, Restoration and Aftercare Phases

· Services ducts or other confined spaces at basements or ground floor levels;

· External manholes, inspection chambers, ducts or other accessible enclosed spaces under the ground;

· Waste Reception Area of the existing NENT Landfill; and

These receivers are categorised as High Sensitivity.

7.4.4.2 Outside Landfill Extension Site

The original consultation zone of the existing NENT Landfill is shown in Drawing No. 24315/13/502. It is overlaid with the proposed new demarcation of a 250m consultation zone corresponding to the latest footprint of NENT Landfill Extension site area. In general, the land area encroached by the new consultation zone of the landfill extension site is a steep hilly terrain. The landuse of the area is not defined and the demarcation of consultation zone will impose constraints on any future developments.

According to the Wo Keng Shan Outline Zoning Plan (OZP) S/NE-WKS/7 (draft amendment) extracted from the “Statutory Planning Portal” of Planning Department (PlanD) website at http://www.ozp.tpb.gov.hk/default.aspx, the planned landuse to the south of the landfill extension site consists mainly of “Green Belt” with minor area for “Agriculture” and “Village Type Development” with the landuse governed by the Town Planning Ordinance:

Green Belt

Use always permitted

· Agricultural use; barbecue spot; government use (police reporting centre only); nature reserve; nature trail; on-farm domestic structure; picnic area; public convenience; tent camping ground; wild animal protection area.

Use that may be permitted with/without conditions on application to Town Planning Board

· Animal boarding establishment; broadcasting, television and/or film studio; columbarium (within a religious institution or extension of existing columbarium only); field study/ education/ visitor centre; government refuse collection point; government use (not elsewhere specified); helicopter landing pad; holiday camp; house (New Territories exempted house only, other than rebuilding of NT exempted house or replacement of existing domestic building by NT exempted house permitted under the covering notes); petrol filling station; place of recreation, sports or culture; public transport terminus or station; public utility installation; public vehicle park (excluding container vehicle); radar, telecommunications electronic microwave repeater, television and/or radio transmitter installation; religious institution; residential institution; school; service reservoir; social welfare facility; utility installation for private project.

Agriculture

Use always permitted

· Agricultural use; government use (police reporting centre only); on-farm domestic structure; public convenience; religious institution (ancestral hall only); rural committee/village office.

Use that may be permitted with/without conditions on application to Town Planning Board

· Animal boarding establishment; barbecue spot; field study/ education/ visitor centre; government refuse collection point; government use (not elsewhere specified); house (New Territories exempted house only, other than rebuilding of NT exempted house or replacement of existing domestic building by NT exempted house permitted under the covering notes); picnic area; place of recreation, sports or culture (horse riding school, hobby farm, fishing ground only); public utility installation; religious institution (not elsewhere specified); school; utility installation for private project.

Village Type Development

Use always permitted

· Agricultural use; government use (police reporting centre, post office only); house (New Territories exempted house only); on-farm domestic structure; religious institution (ancestral hall only); rural committee/village office.

Use that may be permitted with/without conditions on application to Town Planning Board

· Eating place; government refuse collection point; government use (not elsewhere specified); house (not elsewhere specified); institutional use (not elsewhere specified); place of recreation, sports or culture; public picnic; public convenience; public transport terminus or station; public utility installation; public vehicle park (excluding container vehicle); religious institution (not elsewhere specified); residential institution; school; shop and services; social welfare facility; utility installation for private project.

The northern part of the consultation zone of NENT Landfill Extension site falls within the Tong To Shan Archaeological Site which also imposes restrictions on any proposed development/ re-developments.

All existing and future planned developments within the newly proposed 250m consultation zone will be the potential targets prone to the risk of LFG migration. As of the submission of this EIA Report, there were no identified proposed/ planned new developments or re-developments within this boundary.

A detailed site survey has revealed 2 nearest LFG receivers outside the NENT Landfill extension site including LFG1 (Wo Keng Shan Tsuen) and LFG2 (Tong To Shan Tsuen), as depicted in Drawing No. 24315/13/502. LFG1 lies within the original 250m consultation zone of NENT Landfill site (at ~100m from the landfill site boundary). It is therefore categorised under “High Sensitivity”.

LFG2 is a village house marginally outside the proposed new demarcation of 250m consultation zone corresponding to the latest footprint of NENT Landfill extension site area (at ~270m from the landfill extension site boundary). Although it is currently abandoned and unoccupied, it will be prudent to pay due attention to the implementation of all necessary protective measures if LFG2 were occupied in future.

7.4.5 Qualitative Risk Assessment

With all the information regarding the sources, pathways and receivers identified in the previous sections, a qualitative risk assessment of LFG hazards is summarised in Table 7.5 based on the criteria in stipulated in Table 7.1. According to the LFG Guidance Note, for the purposes of categorising the site at the planning stage, the category is based upon the highest level of risk nominated for any of the potential impacts identified.

The overall risk level of LFG hazards to receivers within the landfill extension site is categorised as ‘High’ (Category B). Significant engineering measures will be required to protect the planned development and activities within. Active gas control system supported by gas barriers and monitoring systems will be required for Category B risk level.

The overall risk level of LFG hazards to receivers outside the landfill extension site is categorised as ‘Medium’ (Category C). Adequate engineering measures will be required to protect the proposed development. The use of ‘semi-active’ or enhanced passive gas controls and detection system (in some situations) will be required for Category C risk level.

Table 7.5: Qualitative risk assessment of LFG hazards associated with NENT Landfill Extension

Source	Pathway	Receiver Sensitivity	Risk
*Within NENT Landfill Extension Site*
LFG from existing NENT Landfill and NENT Landfill Extension : Medium	Natural (faults): Very Short/ Direct	Excavation works during construction and landfill operation: High	High
	Man-made (services routes): Very Short/ Direct	Excavation works during construction and landfill operation: High	High
*Outside NENT Landfill Extension Site*
From future NENT Landfill Extension : Medium	Natural (faults): Long/ Indirect	Adjacent residents: High	Medium
From future NENT Landfill Extension : Medium	Man-made (services routes): Long/ Indirect	Adjacent residents: High	Medium

7.5 Protective and Precautionary Measures

The design of suitable level of precautionary measures and contingency plans for the landfill extension and the potential receivers will be incorporated. Future landfill liner, leachate collection and treatment system, LFG control devices, landfill capping will be designed with reference to the specifications of existing NENT Landfill. An Emergency and Contingency Plan will be devised by the DBO Contractor for implementation of appropriate actions in case any LFG migration detected. Such measures include those currently being adopted in the existing NENT Landfill, e.g. installation of double layer liner, LFG extraction/ collection/treatment/export systems, gas sensors, etc. The protective and precautionary measures proposed would also provide information for the ecological impact assessment on the potential risk on wildlife due to accidental LFG migration.

A comprehensive review of the previous monthly and annual reports of landfill operation for the environmental and operational monitoring data, and operation and incident records of mitigation and protective measures adopted in the existing NENT Landfill (Appendix 7.1) has provided the basis for the following conclusions:

· LFG liner: effective barrier to prevent LFG migration off-site;

· LFG collection and extraction system: effective to convey LFG from buried waste location to treatment and utilisation systems;

· LFG treatment by flaring: effective to convert LFG to harmless CO₂;

· LFG utilisation for power generation: effective to convert LFG to electrical power;

· LFG utilisation at ammonia stripping plant: effective to convert LFG to heat energy for combustion and removal of toxic ammonia; and

· LFG recovery system: effective to deliver LFG off-site for energy source of towngas production.

Based on these review findings, the mitigation and protective measures adopted in the existing NENT Landfill are proposed for the future NENT Landfill Extension site, in consideration of the following key factors:

· The NENT Landfill Extension site has similar geological features to the existing NENT Landfill;

· The NENT Landfill Extension site is anticipated to receive waste of similar nature to the existing NENT Landfill;

· The NENT Landfill Extension site has comparable capacity to the existing NENT Landfill; and

· The existing NENT Landfill operation has demonstrated the capability and success of the implemented mitigation and protective measures as precedent of the NENT Landfill Extension.

In case LFG migration is detected and confirmed, the Emergency and Contingency Plan will be triggered for implementation of the necessary action, which include but not limited to the necessary evacuation of occupants, provision of forced ventilation to the concerned sensitive receiver, investigation of potential source of LFG, increase LFG extraction rate on-site, etc. Details of the procedures will be documented in the Emergency and Contingency Plan.

7.5.1 Within Landfill Extension Site

According to the LFG Guidance Note, engineering measures will be required to protect the planned development with risk category at “High“ level (Table 7.2). Recommendations for protection and precautionary measures for implementation in NENT Landfill Extension during the various Project phases are discussed as follows.

7.5.1.1 Construction Phase

Special precautions should be taken in all respects of works against the possible presence of LFG due to close proximity of the landfill extension site to the existing NENT Landfill. Potential hazards of exposure to LFG, e.g. ignition, explosion, asphyxiation, toxicity, etc. should be fully aware and alerted.

Prominent LFG safety warning signs should be erected on-site to alert all personnel and visitors of the hazards during excavation works. No smoking or burning should be permitted on-site in the working area, and prominent ‘No smoking’ and ‘No Naked Flames’ signs should be erected on-site where appropriate. No worker should be allowed to work alone at any time in excavated trenches or confined areas on-site.

Adequate fire fighting equipment should be provided on-site. Construction equipment should be equipped with a vertical exhaust at least 0.6m above ground installed with spark arrestors. Electrical motors and extension cords should be explosion-proof and intrinsically safe when being used on-site.

‘Permit to Work’ system should be implemented in accordance with the guidance on entry into confined spaces provided in ‘Code of Practice on Safety and Health at Work in Confined Spaces’ issued by Labour Department of HKSAR Government. Welding, flame-cutting or other hot works should be conducted only under ‘Permit to Work’ system following clear safety requirements, gas monitoring procedures and in the presence of qualified persons to oversee the works.

For piping assembly or conduit construction, all valves and seals should be closed immediately after installation to avoid accumulation and migration of LFG. If installation of large diameter pipes (diameter >600mm) is required, the pipe ends should be sealed on one side during installation. Forced ventilation is required prior to operation of the installed pipeline. Forced ventilation should also be required for works inside trenches deeper than 1m.

The frequency and location of LFG monitoring within the excavation area should be determined prior to commencement of works. LFG monitoring in excavations should be conducted at no more than 10mm from the exposed ground surface. For excavation works, LFG monitoring should be conducted (1) at ground surface prior to excavation, (2) immediately before workers entering excavations, (3) at the beginning of each half-day work, and (4) periodically throughout the working day when workers are in the excavation. Any cracks on ground level encountered on-site should be monitored for LFG periodically. Appropriate action should be taken in accordance with the action plan shown in Table 7.6.

LFG precautionary measures involved in excavation and piping works should be provided in accordance with the LFG Guidance Note and included in the Safety Plan for the construction phase of the Project. Temporary offices or buildings should be located where free LFG has been proven or raised clear of ground at a separation distance of at least 500mm.

For large development such as NENT Landfill Extension, a Safety Officer trained in the use of gas detection equipment and landfill gas-related hazards should be present on-site throughout the groundwork phase. The Safety Officer should be provided with an intrinsically safe portable instrument appropriately calibrated and capable of measuring the following gases:

· Methane (CH₄)	0-100% Lower Explosion Limit (LEL) and 0-100% v/v;
· CO₂	0-100%; and
· O₂	0-21%

Periodically during groundwork construction, CH₄, CO₂ and O₂ should be monitored in the works area by using appropriately calibrated portable gas detection equipment. The monitoring frequency and areas to be monitored should be set down prior to commencement of groundwork either by the Safety Officer or by an appropriately qualified person. Routine monitoring should be carried out at all excavations, manholes and chambers and any other confined spaces that may have been created by the temporary storage of building materials on-site. All measurements in excavations should be made with the monitoring tube located not more than 10mm from the exposed ground surface.

For excavations deeper than 1m, measurements should be conducted:

· At ground surface before excavation commences;

· Immediately before any worker enters the excavation;

· At the beginning of each working day for the entire period the excavation remains open; and

· Periodically throughout the working day whilst workers are in the excavation.

For excavations between 300mm and 1m, measurements should be conducted:

· Directly after the exvation has been completed; and

· Periodically whilst the excavation remains open.

For excavations less than 300mm, monitoring may be omitted at the discretion of the Safety Officer or other appropriately qualified person.

Table 7.6: Action plan for LFG monitoring during construction phase

Parameter	Monitoring Result	Action
O₂	<19%	Ventilate trench/ void to restore O₂ level to >19%
	<18%	Stop works, evacuate personnel/ prohibit entry, and increase ventilation to restore O₂ level to >19%
CH₄	>10% LEL*	Post ‘No smoking’ signs, prohibit hot works, and ventilate to attenuate CH₄ level to <10% LEL
	>20% LEL	Stop works, evacuate personnel/ prohibit entry, and ventilate to attenuate CH₄ level to <10% LEL
CO₂	>0.5%	Ventilate to attenuate CO₂ level to <0.5%
	>1.5%	Stop works, evacuate personnel/ prohibit entry, and ventilate to attenuate CO₂ level to <0.5%

* LEL: Lower Explosion Limit

7.5.1.2 Operation, Restoration and Aftercare Phases

Where any service voids, manholes and inspection chambers within the landfill extension site are entered for maintenance and LFG monitoring, all the safety requirements in accordance with the ‘Code of Practice on Safety and Health at Work in Confined Spaces’ issued by Labour Department of HKSAR Government should be strictly followed.

Buildings onsite should be incorporated with passive system relying on natural air movement to prevent gas build-up and active system requiring energy input to mechanically move air to protect against LFG build-up. Design measures for sub-surface building services should include generic measures such as gas barriers, gas vents and strategic routing of any service utilities away from the potential LFG migration pathways.

Any new-built permanent building structures within the landfill extension site, forced ventilation and gas detection system with audible alarm should be installed. When the internal atmosphere is detected with >10% of CH₄, forced ventilation should be triggered automatically. No person should be allowed to enter or remain in any confined areas when CO₂ levels >1.5%/v or O₂ levels <18%/v is detected. Access to confined spaces in the landfill extension site should be controlled to only authorised persons.

Specific types of gas protection measures which can be applied to building services have been provided in accordance with the LFG Guidance Note as included in Appendix 7.2. They generally include gas barriers, gas vents, location of service entries above ground, and service conduits passing through consultation zone.

7.5.2 Outside Landfill Extension Site

The administrative control on development adjacent to the future NENT Landfill Extension site shall be defined by the 250m consultation zone, which is a line running parallel to and 250m away from the edge of the landfill site boundary. If a proposed development or re-development is to be located within the future 250m consultation zone of NENT Landfill Extension site, the project proponent will be required to conduct an LFG hazard assessment and submit the assessment report to the EPD for consultation and vetting in accordance with ProPECC PN 3/96 and LFG Guidance Note. The project proponent should:

· Carry out an LFG hazard assessment to evaluate the degree of risk associate with the proposed development;

· Design suitable precautionary/ protection measures to render the proposed development as safe as reasonably practicable;

· Ensure that the precautionary/ protection measures to be fully implemented according to the design; and

· Establish a maintenance and monitoring programme to ensure the continued performance of implemented protection measures.

Based on the latest design, a preliminary 250m consultation zone is proposed as depicted in Drawing No. 24315/13/502. The final demarcation of this zone should be updated for the LFG Guidance Note with respect to the final footprint of NENT Landfill Extension. This 250m consultation zone acts as a precautionary measure, within which any development or re-development projects falling in whole or in part should give attention to the procedures, requirements and guidelines so that potential hazards associated with LFG for the proposed development can be minimised or avoided at an early stage.

As illustrated in Drawing No. 24315/13/502, the extension of the consultation zone will attribute to the additional encroachment of totally ~15 ha of land to the north within the steep hilly terrain near Tong To Shan Archaeological Site and south bound of the landfill extension site near Wo Keng Shan Tsuen. However, these areas are imposed with various extent of development contraints, e.g. their landuse not yet being defined, low development potential due to steep hill slopes and terrain, as part of the Tong To Shan Archaeological Site, etc. The anticipated LFG mitigation and protective measures required for any new developments or re-developments in the extended consultation zone will be similar to those within the original area. Protective measures required will be dependent on the location, distance, landuse, etc relative to the NENT Landfill Extension site. Possible gas protection measures that may be applied to new development in accordance with the LFG Guidance Note are summarised below :

General Protection Measures

Passive systems

The most common way of preventing gas from entering an area of ground is to set a “gas barrier” into the ground which is either keyed into low permeability strata or extended at least 1m below the lowest groundwater level.

The presence of a gas barrier to the movement of gas may lead to a gradual build up of gas on the landfill side of the barrier if the gas migration pathway is covered by low permeability materials. To relieve the potential build up of gas, it may be necessary to install additional measures for venting the gas such as trenches filled with no-fines, granular material, e.g. gravel, connected to venting pipes which will provide a preferential pathway for the release of gas to atmosphere.

Active systems

Active systems for preventing gas entering an area of land usually comprise a series of vertical wells arranged in a line across the route of gas migration. By applying suction to the wells, gas is drawn out of the ground and gas which is migrating horizontally not employed, unless there are substantial volume of gas migrating through the ground.

Gas monitoring

With either passive or active systems, it is usual to install monitoring wells into the ground on the development side of the barrier or extraction wells. These are used to measure the concentrations of CH₄ and CO₂ within the ground and hence determine the effectiveness of the measures in preventing LFG migration.

Building Protection Design Measures

Passive systems

· Gas-resistant polymeric membranes which can be incorporated into the floor or wall construction as a continuous sealed layer. Membranes should be able to demonstrate low gas permeability and resistant to possible chemical attack and may incorporate aluminum wafers to improve performance.

· Other building materials, e.g. dense well-compacted concrete or steel shuttering which provide a measure of resistance to gas permeation.

· Creation of a clear void under the structure which is ventilated by natural structure and provide preferential pathways for release of gas.

· Synthetic composite geotextile which provide a free-venting cellular structure and provide preferential pathways for release of gas.

Passive control measures may be used in low and medium risk situations where gas emissions are expected to be at relatively low rates and concentrations and venting to atmosphere is unlikely to cause a hazard or nuisance due to the low concentration or high dilution which will occur.

Active systems

· A void under the structure like passive control, but it is continuously ventilated by a fan such that any emissions of gas from the ground are mixed and diluted in the air flow before discharge to atmosphere. The rate of ventilation is usually expressed in terms of the volume of air changes (volume of void) per hour and is designed to ensure that, based on the estimated rate at which gas will enter the void, the LFG will be diluted to safe concentrations. Discharge to atmosphere usually takes place above eaves level of the building.

· Construction of a granular layer incorporating perforated collector pipes which is continually ventilated by a fan, such that any emissions of gas from the ground are drawn towards the end of the pipes and diluted in the air flow before discharge to atmosphere above the eaves level of the building.

· Creation of a positive pressure zone below the building structure by injection of migrated LFG into the granular layer.

· Creation of positive air pressure zones within building structures to counteract possible LFG migration into the building from the ground.

Active control measures should be used in conjunction with passive barriers, e.g. membranes in floors, in order that there is no migration of air / gas flow through a floor or wall into a structure. Gas detection systems should also be used to monitor gas in extracted air flow, and to monitor internal spaces inside buildings. Active systems are normally required for high risk sites where gas has been measured in the ground at or close to the development site, and buildings are close to the source of gas.

Gas detection system

· A series of sensors located in appropriate positions within a structure where gas has the potential to accumulate, e.g. near service entries, inside ventilation basements, cupboards or ducts. The sensors detect flammable gas by catalytic oxidation or infra-red principles, and pass data back to a control panel by electrical cabling. The control panel can be set to have two triggers activating alarms and may also be linked by wirless telemetry or internet off-site.

· A series of sampling tubes which are located in appropriate positions and run back to a single measurement station operating on infra-red measurment principles. A pump automatically draws samples of air/gas along each tube in a pre-set pattern such that measuremens of flammable and/or other gases (e.g. CO₂) can be taken at regular and frequent intervals. Triggers, alarms, wireless telemetry and internet systems can be incorporated.

· Manual monitoring can be conducted using a range of portable instruments. Instruments used in areas where flammable gas may be present should be intrinsically safe.

Gas detection system should only be proposed where there is an organisation involved n the long-term use of the development which can be relied upon to maintain and calibrate the system on a regular basis. Where a detection system is used as a final defence, it must be ensured that appropriate emergency action, to be taken in the event of the trigger levels being exceeded, are specified explicitly in an Emergency and Contingency Plan.

Maintenance of control measures

Fundamental to the success of gas protection measures is the means by which they are monitored, managed and maintained, and thus all designs must be accompanied by a statement or set of procedures showing how the measures proposed can be confidently expected to operate satisfactorily for the duration of the potential gas-producing lifetime of the landfill.

Design Measures for Sub-surface Building Services

Generic Protection Measures

· As for barriers used to prevent movement of gas through the ground, use may be made of clay (or clay-rich soils), bentonite or polymeric membranes (e.g. HDPE). A gas barrier used to prevent movement of gas through services may form part of a more extensive barrier to prevent general mitigation towards the development. In the case of water pipes and sewers which are not always fully filled, water traps e.g. U-bends, should be provided to effectively seal off the conduit and prevent gas-phase transport.

· Vent pipes or gridded manhole covers may be used to avoid build-up of gas in underground utilities manholes. Venting stacks may be built into inspection chambers or connected to collection pipes within high permeability drainage layers adjacent to gas barriers. Under all circumstances, care should be taken in accessing any manhole chambers especially those which are not fitted with vents and necessary safety procedures must be followed.

· In some cases it is possible to route service entries into a building above ground level, therby providing a discontinuity in the gas migration pathway and thus eliminating the risk of gas entry to the building interior.

Services Conduits Passing through Consultation Zone

· For all service runs, the aim should be to provide a protection barrier located at the point where the trenches passes through the perimeter of the consultation zone.

· The service run through the consultation zone may remain “unprotected” since the risks will be minimised by the protection measures installed at the perimeter of the consultation zone and as the general public may not have access to such underground features.

· The service run should be designated as a “special route” and the utility companies should be informed to that effect so that they may implement precautionary measures.

· Any future works e.g. maintenance or extension should be subject to the recommendations specified in the LFG guidance Note.

· Any above ground (minor) termination features e.g. telecom cabinets should be considered to be “buildings” and should be protected by e.g. membrane barriers to minimise the possibility of gas ingress.

Guidance for Entry into Manholes and Chambers

· Any chamber, manhole or culvert which is large enough to permit access to personnel should be subject to entry safety procedures. Such work in confined spaces is controlled by the Factory and Industrial Undertakings (F&IU) (Confined Spaces) Regulations of the F&IU Ordinance. The key issues with regards to the confined spaces which are at risk of LFG build-up have been addressed in section 7.5.1.1 above.

Further details of these measures have been provided in the LFG Guidance Note.

　　　　　　7.6 Monitoring Requirement

LFG monitoring should be conducted in various phases of NENT Landfill Extension with the following key objectives:

· To ensure the safety and health of workers during the construction stage of landfill extension.

· To determine the performance and effectiveness of LFG mitigation measures and control systems on preventing uncontrolled LFG migration.

· To establish a monitoring regime for buildings within the landfill site services routes and other enclosed areas as a warning system for detection of any potential build-up of hazardous LFG concentrations.

· To ascertain the characteristics of the landfill and estimate the quantity and quality of the LFG production in order to assess the potential for future utilisation.

The LFG monitoring programme of the existing NENT Landfill including the monitoring frequency and location was reviewed to suit the future landfill extension. Detailed LFG monitoring requirements will be established in the EM&A Manual for NENT Landfill Extension including the specifications of monitoring locations, parameters, equipment, procedures, frequency, reporting format, Action and Limit (A/L) Levels, Event and Action Plan (EAP), and Emergency and Contingency Plan, etc. With reference to the monitoring data of the existing landfill operation, monitoring for a suite of LFG parameters will be continued, including:

· Surface gas:	CH₄, CO₂, O₂;
· Monitoring holes:	Pressure, methane, carbon dioxide, oxygen, flammable gas;
· Well head:	Pressure, oxygen, methane, carbon dioxide, flammable gas, volatile organic compounds (VOCs);

As mentioned in Table 7.4, the continuous ‘false’ exceedances of CO₂ levels measured at some boreholes due to natural sources as reported in the monthly reports should be fully addressed in the future LMP for NENT Landfill Extension. Drawing No. 24315/13/503 illustrates the monitoring results of background CO₂ levels at 25 boreholes constructed in the ground investigation. As elevated background CO₂ levels were noticeable at certain locations within the landfill extension site, it would be prudent to rationalise the Action and Limit Levels with reference to these geographical/ geological variations of CO₂ levels.

The LFG monitoring locations of the existing NENT Landfill site is shown in Drawing No. 24315/13/504. The proposed tentative monitoring locations for the future NENT Landfill Extension site are also shown in Drawing No. 24315/13/504, which are subject to changes depending on the design and modification by the DBO Contractor.

In general, the LFG monitoring programme should include on-site and off-site monitoring for the above parameters at frequency specified in the future LMP. Similar to that being practised in the existing NENT Landfill, on-site and off-site monitoring for LFG should be conducted including:

· Quantity and quality of extracted LFG at individual well head;

· Quantity of LFG automatically monitored at LFG pumping station;

· Fixed surface and borehole locations along the landfill site boundary and at potential sources of concern;

· Monitoring safe level of LFG concentration, and implementation of sufficient mitigation measures when entering confined spaces within the landfill site.

· Off-site monitoring for LFG at highly sensitive receivers, e.g. LFG1 Wo Keng Shan Tsuen and LFG2 Tong To Shan (if occupied); and

· Detailed requirements of LFG monitoring shall be defined in the EM&A Manual and LMP.

The measured LFG results will be checked for compliance against the pre-defined A/L Levels established in the EM&A Manual and in the Landfill Monitoring Plan developed by the DBO Contractor. In case exceedance of compliance level is detected at any locations, the EAP will be triggered for necessary action to be taken.

If abnormally high LFG level is detected at any off-site sensitive receivers, the Emergency and Contingency Plan will be strictly followed to trigger the planned action without delay, which may include but not limited to the evacuation of occupants, provision of forced ventilation to the concerned sensitive receiver, investigation of potential source of LFG, increase LFG extraction rate on-site to minimise migration etc. Details of the procedures will be documented in the Emergency and Contingency Plan.

7.7 Implication of IWMF Implementation

If the Integrated Waste Management Facility (IWMF) implementation were considered in 2010’s, the incoming waste characteristics to the NENT Landfill Extension site would be altered substantially, mainly with inert incinerator ashes. The LFG generation potential, hence its associated risk to nearby environment, would be anticipated to reduce accordingly.

7.8 Conclusion

The results of this qualitative risk assessment for LFG hazards associated with the construction, operation, restoration and aftercare phases indicate that the overall risks to the receivers within the NENT Landfill Extension would be categorised as ‘High’ and that to the receivers outside the NENT Landfill Extension would be ‘Medium’. The sensitive receivers falling within the newly proposed 250m consultation zone shall be prone to LFG potential risk and appropriate protective and precautionary measures including engineering design and monitoring programme have been proposed to reduce such risk to acceptable levels. With these measures in place, no adverse impact would be anticipated.

8 Landscape and Visual Impact

8.1 Introduction

This chapter assesses the landscape and visual impacts associated with the NENT Landfill Extension during the construction, operation, restoration and aftercare phases.

The landscape and visual impact assessment (LVIA) has been carried out in accordance with the guidelines contained in Annexes 10 and 18 of the TM-EIAO as well as the requirements set out under clauses 3.4.6.

The proposed development will have impacts ranging from slight to moderate to the upland landscape at the northwest facing slope of Wo Keng, rural settlement Landscape of Tong To Shan Tsuen & Ngong Tong, grassland, shrubland and woodland within the Project site. The lost of 1.5 ha of existing landscape resource woodland and 5.8 ha of shrubland will be compensated by 26.83 ha (about 43% of the Project site) of woodland mix progressively planted in phases with about 148,100 nos. of tree seedlings/ whips. In addition, 19 ha of shrubland mix planting and 17.55 ha of grassland will be created in the restoration phase. The entire landfill extension will ultimately be restored and vegetated to match with its surrounding landform and vegetation patterns in the restoration and aftercare phases. The overall landscape and visual impact of the Project is acceptable with mitigation measures implemented.

8.2 Legislation, Standards and Guidelines

The relevant legislation and associated guidance notes applicable to the study for the assessment of landscape and visual implications include:

· EIAO Guidance Notes 8/2002 on Preparation of Landscape and Visual Impact Assessment under the EIAO.

· ETWB TC(W) No. 29/2004 on Registration of Old and Valuable Trees, and Guidelines for their Preservation.

· ETWB TC(W) No. 24/2004 on Specification Facilitating the Use of Concrete Paving Units Made of Recycle Aggregates.

· ETWB TC(W) No. 11/2004 on Cyber Manual for Greening

· ETWB TC(W) No. 2/2004 on Maintenance of Vegetation and Hard Landscape Features. (to be read in conjunction with WBTC(W) No. 14/2002).

· ETWB TC(W) No. 34/2003 on Community Involvement in Greening Works

· ETWB TC(W) No. 8/2005 on Aesthetic Design of Ancillary Buildings in Engineering Projects

· WBTC No. 7/2002 on Tree Planting in Public Works.

· WBTC No. 17/2000 Improvement to the Appearance of Slope.

· WBTC No. 25/1993 Control of Visual Impact of Slope.

· GEO Publication No. 1/2000 on Technical Guidelines on Landscape Treatment and Bio-Engineering for Man-made Slope and Retaining Walls.

· HyDTC No. 5/2000 on Control in the use of Shotcrete (Sprayed Concrete) in Slope Works.

· HyDGN No. LU/GN/001 on Management and Maintenance of Landscape Works along Public Roads

· Hong Kong Planning Standards and Guidelines.

8.3 Landscape And Visual Impact Assessment Methodology

8.3.1 General Methodology

Landscape impact assessment evaluates the source and magnitude of developmental effects on the existing landscape resources, character and quality in the context of the site and its environs; and visual impact assessment evaluates the source and magnitude of effects caused by the proposed development on the existing views, visual amenity, character and quality of views to the visually sensitive receptors within the context of the site and its environs.

The significant thresholds for the landscape and visual impacts are assessed for the construction phase and operation phase both with and without mitigation measures.

These residual impacts are then evaluated in accordance with Annex 10 of the Technical Memorandum to the EIAO. In order to illustrate these landscape and visual impacts and to demonstrate the effectiveness of the proposed landscape and visual mitigation measures, photomontages at selected representative viewpoints have been prepared to illustrate:

· existing baseline condition

· unmitigated impacts (day 1)

· mitigated impacts (day 1)

· mitigated impacts (year 10)

8.3.2 Baseline Study Methodology

8.3.2.1 Landscape Baseline Study Methodology

In accordance with the Study Brief, a baseline survey of the existing landscape character zones and landscape resources within 500m from the proposed development has been undertaken by a combination of site inspections and desktop surveys. Planned developments for both within the study area and adjacent to it are also considered.

The baseline survey forms the basis of the landscape context by describing broadly homogenous units of similar character. Environmental capital approach is adapted to classify the landscape into distinct landscape character areas (LCAs) based on distinct patterns or combinations of landscape resources / elements that occur consistently in a particular landscape. The landscape elements considered include:

· local topography;

· woodland and other vegetation types;

· built form, land use and patterns of settlement;

· scenic spots;

· details of local materials, architectural styles and streetscapes;

· natural coastline;

· prominent watercourses; and

· cultural and religious identity, including fung shui features.

The individual landscape character areas (LCAs) / landscape resources (LRs) are described qualitatively and quantitatively. The individual LRs at baseline study and those to be affected due to the Project will be quantified. Their sensitivities are then evaluated and rated as low, medium or high based on the following factors:

· quality and value of landscape character/ resources;

· importance and rarity of special landscape resources;

· ability of the landscape to accommodate change without compromising its essential nature.

· significance of the change in local and regional context; and

· maturity of the landscape.

The sensitivity of the landscape character areas (LCAs) / landscape resources (LRs) has been assessed against the scale shown in Table 8.1.

Table 8.1: Sensitivity of landscape character area/ landscape resources

High	e.g. important components of a landscape of particularly distinctive character susceptible to relatively small changes.
Medium	e.g. a landscape of moderately valued characteristics reasonably tolerant to change.
Low	e.g. a relatively unimportant landscape able to absorb significant change.

8.3.2.2 Visual Baseline Study Methodology

The baseline survey of views towards the proposed development will be carried out by identifying:

· The visual envelope (zone of visual influence) which is, according to EIAO GN No. 8/2002, generally the viewshed formed by natural/man-made features such as ridgeline or building blocks. The visual envelope may contain areas, which are fully visible, partly visible and non-visible from the proposed development. The visual envelope of the Project will be presented on relevant plans.

· The visually sensitive receivers (VSRs) within the visual envelope whose views will be affected by the development.

The baseline survey was conducted by taking photographs at typical views and describing and recording their character and value within the visual envelope from low-level viewpoints (street level), high-level viewpoints (high-rise buildings or hillside vantage points) and sea-level viewpoints (ferry passengers). Wherever possible, both present and future VSRs will be considered. Criteria for Ranking Sensitivity of VSRs are:

· Type of representative receiver population;

· Value and quality of existing views;

· Estimated number of representative receiver population;

· Availability and amenity of alternative views;

· Duration or frequency of views; and

· Degree of visibility.

8.3.3 Source of Impact and Impact Assessment Methodology

8.3.3.1 General

The assessment of the potential landscape and visual impacts of the proposed development will result from:

· identification of the sources and magnitude of impacts that would be generated during construction and operation phase, as well as restoration and aftercare phase.

· identification of the principal landscape and visual impacts, primarily in consideration of the degree of change to the baseline conditions.

8.3.3.2 Magnitude of Change (Landscape) Assessment Methodology

Some common factors that will be considered in deriving the magnitude of change in assessing landscape impacts are as follows:

· compatibility of the Project with the surrounding landscape;

· duration of impacts under construction, operation, restoration and aftercare phases;

· scale of development;

· reversibility of change; and

· quantification of landscape resources affected.

The magnitude of change in the landscape will be classified as “negligible”, “small”, “intermediate” and “large” based on the above criteria.

8.3.3.3 Magnitude of Change (Visual) Assessment Methodology

Some common factors that will be considered in deriving the magnitude of change in assessing visual impacts are as follows:

· compatibility of the Project with the surrounding landscape;

· duration of impacts under construction, operation, restoration and aftercare phases;

· scale of development;

· reversibility of change;

· viewing distance; and

· potential blockage of view.

The magnitude of change to the views will be classified as “negligible”, “small”, “intermediate” and “large” based on the above criteria.

8.3.3.4 Significance of Impact Assessment Methodology

Significance of Impact is a function of sensitivity of receptors and magnitude of change. The analysis of the significance threshold for the landscape and visual impacts during construction and operation phase, as well as restoration and aftercare phase will be presented in the form of matrix (Table 8.2).

Table 8.2: Significance of Impact

		Sensitivity of Receptors
		Low	Medium	High
Magnitude of Change caused by development	Large	Moderate	Moderate to Significant	Significant
	Intermediate	Slight to moderate	Moderate	Moderate to Significant
	Small	Slight	Slight to moderate	Moderate
	Negligible	Negligible	Negligible	Negligible

8.3.3.5 Mitigation Measures Approaches

The identification of the landscape and visual impacts will highlight the potential primary sources of impacts and their magnitude of change caused to sensitive receivers. Corresponding mitigation measures will be proposed to avoid and reduce the identified sources of impacts. Furthermore, mitigation measures to remedy and compensate unavoidable impact will be proposed to minimise the magnitude of change caused to sensitive receivers.

8.3.3.6 Residual Impacts Assessment Methodology

Residual impacts are those impacts remaining after the proposed mitigation measures have been implemented. This is often 10 to 15 years after commissioning, when the planting mitigation measures are deemed to have reached a level of maturity, which allow them to perform their original design objectives.

The level of impact is derived from the magnitude of change that the development will cause to the existing view or landscape character and its ability to tolerate change, i.e. the quality and sensitivity of the view or landscape character taking into account the beneficial effects of the proposed mitigation. The significance threshold is derived from the matrix shown above.

In accordance with Annex 10 of the EIAO TM, an overall assessment is also made of the residual landscape and visual impacts for the proposed development (Table 8.3).

Table 8.3: Residual impact assessment methodology

Beneficial	Acceptable	Acceptable with mitigation measures	Unacceptable	Undetermined
If the Project will complement the landscape and visual character of its setting, will follow the relevant planning objectives and will improve overall and visual quality.	If the assessment indicates that there will be no significant effects on the landscape, no significant visual effects caused by the appearance of the Project, or no interference with key views.	If there will be some adverse effects, but these can be eliminated, reduced or offset to a large extent by specific measures.	If the adverse effects are considered too excessive and are unable to mitigate practically.	If significant adverse effects are likely, but the extent to which they may occur or may be mitigated cannot be determined from the study. Further detailed study will be required for the specific effects in question.

8.4 Baseline Study Frameworks

8.4.1 Landscape Baseline Study Frameworks

8.4.1.1 Landscape Character Areas (LCAs) and Landscape Resources (LRs)

Lists of LCAs and LRs are proposed in Tables 8.4 and 8.5 respectively, together with Drawing Nos. 24315/14/002 to 24315/14/004.

Table 8.4: LCAs within 500m from the Project

	Landscape Characters Areas (LCAs)	Quantity (Ha.)	Description	Sensitivity
LCA1	Disturbed land (Existing NENT Landfill Site)	90.2	· Comprise mainly the existing NENT Landfill site under operation and its associated stockpile and borrow area (SBA) to its east. · The landscape character is of typical degraded land made up of landfill site and SBA, together with their associated access haul roads, artificial cut and fill slopes, modified surface drainage system, waste reception area and leachate treatment system. · It is ready to absorb significant change. · The proposed extension is of the same nature and is considered compatible in terms of land use and landscape character.	Low
LCA2A	Rural Settlement Landscape (Tong To Shan Tsuen & Ngong Tong)	66.5	· Comprises lowland with abandoned rural settlement, abandoned agricultural field and associated hillside backdrop. Woodlands and natural stream course are found in this area. · Historical and cultural landscape features of Tong To Shan Archaeological Site (TTSAS) and Ngong Tong are located.	High
LCA2B	Rural Settlement Landscape (Ping Yuen)	15.9	· Comprises lowland with rural settlement, agricultural field and associated hillside backdrop. · The area within study area is only a small portion of the overall LCA with extent beyond study area. · Its landscape value and quality is deteriorated by its proximity to the existing NENT Landfill site, its waste reception area and road network.	Medium
LCA3A	Upland Landscape (NW Facing slope of Robin’s Nest)	32.4	· Natural steep hillside slope covered by mainly grassland and some woodland. · Located to the east of the SBA of the existing NENT Landfill site, its landscape quality and value considered medium.	Medium
LCA3B	Upland Landscape (SE facing slope of Wo Keng Shan)	54.1	· Natural steep hillside slope covered by mainly grassland and some woodland. · Located on the other side of the hill ridge away from the SBA of the existing NENT Landfill site, its landscape quality and value considered high.	High
LCA3C	Upland Landscape (NW facing slope of Wo Keng Shan)	40.1	· Natural steep hillside slope covered by mainly grassland and shrubland. · Half of the area is surrounding by the existing NENT Landfill site, the waste reception area and the SBA, its landscape quality is considered medium.	Medium

Table 8.5: LRs within 500m from the Project

	Landscape Resources (LRs)	Quantity (Ha.)	Description	Sensitivity
LR1	Woodland	72.7	· These woodlands are mainly found near the ravine valley of upland hillside and near the rural area of Tong To Shan. · Due to having high density of individual trees and their distinct landscape pattern on the background of grassland, these woodlands are considered important in terms of landscape character and value. · Refer to section 8.4.1.2 for preliminary tree assessment.	High
LR2	Shrubland	26.1	· Frequent hill fire has been recorded. · Shrubs with grasses. · Major shrub species found included Baeckea frutescens and Rhodomyrtus tomentosa · Regarded as a transitional phase from grassland to woodland in natural succession if not prevented by frequent hill fire.	Medium
LR3	Grassland	95.5	· Frequent hill fire has been recorded. · Major grass species found included Dicranopteris pedata, Arundinella setosa, Ischaemum spp., Cymbopogon spp., and Panicum sp. · Landscape quality and value considered low.	Medium
LR4	Agricultural Field	13.0	· Mainly found in rural settlement areas near Ping Yuen (under cultivation) and near Tong To Shan (abandoned). · These agricultural fields within the study area account only for a small portion of the overall agricultural field beyond the study area. · Landscape value and quality considered medium.	Medium
LR5	Natural Stream course	505m length	· The downstream of Lin Ma Hang Stream which is ecological rich. · The landscape value and quality is considered high and susceptible to incompatible development.	High
LR6	Existing NENT Landfill Site and associated Stockpile and Borrow Area (SBA)	90.2	· Comprise mainly the existing NENT Landfill site under operation and its associated stockpile and borrow area (SBA) to its east. · The landscape elements include mainly landfill site and SBA, together with their associated access haul roads, artificial cut and fill slopes, modified surface drainage system, waste reception area and leachate treatment system. · Bare soil surface are covered mainly with grass by hydro-seeding. · Its landscape value and quality is considered low. · It is ready to absorb significant change.	Low

8.4.1.2 Preliminary Tree Assessment

A tree survey was conducted in 2005 as shown on Drawing No. 24315/14/005. There was a total of 29 species. The majority of the trees surveyed were young at age and small in size. Out of the 2178 nos. of surveyed trees, 1851 nos. (85%) had a diameter at breath height (DBH) equals to or below 0.3m and the remaining 327 nos. (15%) had a DBH in the range of 0.4m to 0.8m inclusive. Most were common native tree species.

According to ETWB TC(W) No. 29/2004 Para. 7, only trees on unleased Government land within built-up areas or tourist attraction spots in village areas are eligible for inclusion in the Register of Old and Valuable Trees. Upon checking against Appendix A (Location of Built-up Areas) of the technical circular, it has been verified that the Project area does not fall into the designated built-up areas. Nevertheless, the surveyed trees, which were under the list of rare and precious trees were highlighted. Based on the result of tree survey, it was confirmed that there were no trees with a DBH exceeding 1000m, a height exceeding 25m or a spread exceeding 25m.

Out of the 2178 numbers of trees surveyed, about 825 were within the Project site. These affected trees were mainly located in woodlands in the southwest part of the Project site. It is stressed that the woodlands to the north and east of the site are largely avoided. The affected trees will be affected by phases due to progressive change in topography of the site during the construction and operation phases of the landfill extension development. Due to the fact that they are located on slopes inaccessible to vehicles and machineries, the majority of them may not be able to be preserved by transplanting.

The technically feasibility of transplantation are based on the following criteria:

· Variety of species : rare and precious species to be considered for transplanting;

· Condition of tree : trees with balanced form, in good health and high amenity value are considered for transplanting;

· Size and maturity : small and younger trees have a better chance of surviving transplanting while larger, mature trees and difficult to transplant both logistically and in terms of survival rate;

· Species : different trees species have better chances of survival or are better suited to transplanting than other and;

· Accessibility : large machinery is required to lift the trees, steep slopes and rocky terrain therefore make it difficult to access trees.

No trees should be felled or transplanted unless they are inevitably affected by the Project. Affected trees should be transplanted under circumstances where technically feasible. The requirement of having a detailed tree survey report and tree felling application will be specified in the NENT Landfill Extension Contract. A detailed tree survey report and a tree felling application (by the DBO Contractor) will be submitted to government for approval before site formation works commence. The numbers, locations, species and sizes of the trees to be transplanted or felled should be clearly addressed.

To compensate for the loss of existing trees, 26.83 ha (about 43% of the Project site) will be planted with woodland mix progressively in phases. Assuming tree seedlings/whips planting at 1.5m spacing in staggered pattern, there will be 148,100 nos. of tree seedlings/ whips planted. In addition, shrubland mix planting and grassland planting areas will also be created.

8.4.2 Visual Baseline Study Frameworks

8.4.2.1 VSRs

The Project site is situated over 6 km north-east of Fanling, in the very northern part of the New Territories and is bordered by the Frontier Closed Area Boundary to the north. It is located in valley enclosed by ridges, screened off from surrounding villages in low land across the ridgelines. There are no large areas of population within the primary visual envelope of the Project site. Views toward the Project site are significantly blocked by natural geological landforms around the site. The maximum final capping level of the adjoining existing NENT Landfill is +245mPD. Similar maximum final capping level is proposed for the landfill extension at the southeast end and gradually steps down north-westwards to less than 100 mPD.

The Project site is located in a valley to the southeast of the existing NENT Landfill site. The valley is encircled by three ridgelines and exits to the southwest through a small gorge, at approximately +40mPD. The Project site currently accommodates the Landfill Stockpile and Borrow Area (SBA) for the existing NENT Landfill site and its associated haul roads.

On its southerly side, the Project site is enclosed by a major ridgeline, which runs from Wo Keng Shan (+297mPD) to Robin’s Nest (+492mPD). A smaller ridge intersects this main ridgeline along the northern boundary of the Project site and merges into Wong Mau Hang Shan (+243mPD) to the east of the existing NENT Landfill site. A saddle, with a minimum elevation of approximately +140mPD, is located approximately half way along this smaller ridge and overlooks To Tong Shan Settlement District and Lin Ma Hang Village.

Table 8.7 shows the identified visual envelope and VSRs. Samples of typical views are presented on Drawing Nos. 24315/14/007 and 24315/14/008. It should be noted that the assessment is based on the final capping landform of the landfill extension. It is stressed that during the majority period of the construction and operation phase, the Project site is much less visible to its VSRs than towards the end of operation phase. This is because during the majority period, the Project site is much lower than its surrounding ridgelines and the new landform which will be higher than some of the surrounding ridgelines has not been formed and made visible to the VSRs. It is also noted that the Project site is likely to be visible to high-rise development viewers across the border, but great viewing distance significant reduces the visual impact.

8.4.2.2 Descriptions of the Typical Views of the Areas Affected by the Project

The existing views of the Project site affected mainly comprise the following visual elements (Table 8.6):

· View of the existing NENT Landfill site and its Stockpile and Borrow Area

· Typical upland landscape view (Shek Tsai Ha, NW facing slope of Wo Keng Shan)

· Typical Rural Settlement view (Ngong Tong)

Table 8.6: Visual Elements

Visual Elements	Description
View of the existing NENT Landfill site and its Stockpile and Borrow Area (SBA)	· Comprise mainly the existing NENT Landfill site under operation and its associated SBA to its east. · The view to it is of typical degraded land made up of landfill site and SBA, together with their associated access haul roads, artificial cut and fill slopes, modified surface drainage system, waste reception area and leachate treatment system. · The visual quality and value is not high
Typical upland landscape view (Shek Tsai Ha, NW facing slope of Wo Keng Shan)	· Natural steep hillside slope covered by mainly grassland and shrubland. · The affected area is Shek Tsai Ha, which form part of the Wo Keng Shan. · Half of the affected area is surrounded by the existing NENT Landfill site, the waste reception area and the SBA, its visual value and quality is medium.
Typical Rural Settlement view (Ngong Tong)	· Typical view of abandoned rural settlement area with extensive grassland and some graves. · The visual quality and value is medium.

Table 8.7: VSRs identified within the visual envelope

	VSR	Type of VSRs	Population of VSRs	Min. Viewing Distance (km)	Sensitivity	Remarks (Key reasons for ranking sensitivity)
VSR1	Tong To Shan Tsuen	Village Residents	None (Abandoned)	0.7	Low	· It is an abandoned village with no residents. · Relative viewing distance.
VSR2	Lin Ma Hang	Village Residents	Very Few	1.4	High	· A glimpse to the Project site through a saddle (+140mPD) located along a ridgeline to the north of the site. · The Project site will be seen between the natural ridge lines of Wong Mau Hang Shan and Hung Fa Leng.
VSR3	Wo Keng Shan Tsuen	Village Residents	Very Few	0.9	High	· Open view to the Project site through a gorge (+40mPD) located at the south-western boundary. · The Project site will be seen with the Wo Keng Shan as foreground on the right. · Very few village residents.
VSR4	Ping Yeung	Village Residents	Medium	1.6	High	· Similar to the view from VSR2-Wo Keng Shan Tsuen but with a longer viewing distance.
VSR5	Ping Che, Ping Che New Village, Pak Hok Shan, Kai Fong Garden	Village Residents	Medium	1.9	Medium	· Partial view of the Project Site. · The Project site is seen entirely behind the Wo Keng Shan, which acts as the prominent foreground. · Cheung Shan also act as foreground to the right. · Long viewing distance. · The Project site is less visually prominent.
VSR6	Sing Ping Village, Tai Po Tin and government farm	Village Residents	Few	2.4	Medium	· Similar to the view from VSR2-Wo Keng Shan Tsuen but with a much longer viewing distance. · The Project site is less visual dominant.
VSR7	Kaw Liu Village, Kan Tau Wai, Ta Kwu Ling Village, Fung Wong Wu, Tong Fong and Chow Tin Tsuen	Village Residents	Medium	2.8	Medium	· Partial view of the Project site as backdrop behind other visually prominent topological features such as Tung Lo Hang, Tung Fung Au and future restored NENT Landfill site. · Long viewing distance.
VSR8	Sheung Shan Kai Wat and Ha Shan Kai Wat	Village Residents	Few	3.2	Low	· Similar to the views from VSR5 but longer viewing distance. · The Project site is even less visually prominent.
VSR9	Hikers at the top of Robin’s Nest	Hikers	Very few	1.3	High	· Open close view to the Project site but likely to be screened by local immediate vegetation. · Not a popular and easily accessible hiking trail.
VSR10	Ha Heung Yuen and Heung Yuen Wai	Village Residents	Medium	1.8	Medium	· The Project site is behind the ridgelines of the Kong Yiu, Wong Mau Hang Shan and future restored NENT Landfill site, which form the foreground and middle ground. · The Project site is less visually prominent.
VSR11	Chuk Yuen	Village Residents	Few	2.8	Medium	· Partial view of the Project site as backdrop behind other visually prominent topological features such as Tung Lo Hang, Tung Fung Au and future restored NENT Landfill site. · Long viewing distance.
VSR12	Potential future users at the existing NENT Landfill site during its aftercare period	Visitors	Few	0.7	Medium	· Close viewing distance. · View to landfill extension can be easily visually screened off locally. · The number of visitors is anticipated to be small.

　　　　　　8.5 Planning and Development Control Review

A review of the relevant planning and development control framework is carried out to ascertain the current and future committed development and associated sensitive receiver groups within the study area.

8.5.1 Reference for Planning and Development Control Frameworks

Reference to the statuary plans covering the study area and its surrounding are listed in Table 8.8.

Table 8.8: Reference for planning

Title of Plans	Reference	Remark
Draft Wo Keng Shan OZP	S/NE-WKS/7 (extracted from PlanD website in May 2006)	The proposed extension site consists of two types of land use zones, namely, “Other Specified Uses (Landfill)” and “Green Belt”

8.5.2 Possible Amendments required to Statutory Plans

The possible amendments to statutory plans arising from the Project will be highlighted according to Para. 3.5 (f) and (g) of EIAO Guidance Note No. 8/2002.

The majority of the Project site (about 43 ha) is covered by the Stockpile and Borrow Area currently zoned “Other Specified Uses (Landfill)”. The remaining part of the Project site (about 20 ha) extends into the surrounding “Green Belt” zone. Approval from Town Planning Board on rezoning of the affected “Green Belt” zone to “Other Specified Uses (Landfill)” zone would be required. The current OZP would also need to be amended accordingly. It is stressed that the affected “Green Belt” zone is a small portion of a much larger entity of the same zoning which is outside the Project site and extends beyond the study area.

To summarize, the areas to be rezoned is adjoining the existing zone of “Other Specified Uses (Landfill)” and the affected “Green Belt” zone accounts only a small portion of the total area of “Green Belt” zone in the Wo Keng Shan OZP. In addition, the essential planning and conservation intentions of the remaining “Green Belt” zone are unaffected because the zone is neither fragmented, discontinued nor substantially reduced in area. Therefore, it is concluded that the proposed Project has no significant and unacceptable impact on the planning and development control frameworks covering the study area.

8.5.3 Interfacing with nearby Robin’s Nest area

The potential interfacing area of Robin’s Nest area close to the NENT extension site is mainly grassland of low ecological value and impact to this area is therefore considered minimal.

8.6 Source of Impacts and Impact Assessment

8.6.1 Source of Impacts and Impact Assessment

In normal situation, waste filling and site formation works will be carried out at the same time, as infilling operations are carried out in previously prepared areas. It is therefore noted that the construction and operation phases of the landfill extension overlap with each other. As a reference, the existing NENT Landfill was constructed in August 1994 and operated in June 1995. The ongoing construction and operation phase is estimated to be 20 years, depending on waste generation trends. To avoid discontinuous waste reception, it is expected that the landfill extension will be ready for use when the capacity of existing NENT Landfill is about to be reached.

The main sources of landscape and visual impact of the Project come from the construction and operation phase of the landfill extension. The construction and operation primarily involve large-scale excavation of soil, change in topography, construction of vehicular road access, operation of large vehicles and machinery, and erection of any associated waste management ancillary facilities over a long period of time.

The daily operation of a landfill site is to spread and compact the waste after unloading from vehicles by waste moving equipment. The waste is normally covered by another layer of waste or by a temporary cover soil of about 0.15m thick and compacted by compactors to maximize the landfill capacity.

A significant element of a landfill operation is the formation of a spoil mound where the excess arising from the excavation of the main landfill bowl is stored. This area is referred to as the Stockpile/ Borrow Area (SBA), and contains the spoil that will ultimately be returned to the landfill as daily cover, formation of haul roads and intermediate/ final capping. The stockpile is normally constructed abutting against the natural hillside. The SBA is normally constructed in a number of phases to match the programme of landfill earthworks. Normally, slopes of stockpiles are formed at approximately 22 degree (1: 2.5) with face lifts of 7 m. Berms are of a minimum of 1.5 width, with every fourth berm being 4m wide, and graded to a minimum gradient of 1 in 50.

After the capacity of a landfill is reached, the site will enter the restoration and afteruse phase. Relatively, the restoration phase (less than a year) is much shorter than the afteruse phase (20-30 years). Restoration works include final cap construction, landscaping and treatment works within the site to restore the site to suit its designated afteruse. The impact in these two phases will be assessed together.

The preliminary potential sources of landscape and visual impacts are listed in Table 8.9 and Drawing No. 24315/14/001. These identified sources of impact will cause either change or loss of the LCAs and LRs, together with change in views. Landscape impact without mitigation is illustrated in Table 8.10 and Drawing No. 24315/14/002 for LCAs. Landscape impact without mitigation is illustrated in Table 8.11 and Drawing No. 24315/14/004 for LRs. Visual impact without mitigation is illustrated in Table 8.12 and Drawing No. 24315/14/006 for VSRs. Photomontages from selected views without mitigation measures are shown on Drawing No. 24315/14/010 to 012.

Table 8.9: Potential Sources of Landscape and Visual Impacts

	Construction and Operation Phase (Overlapping)
1	Large-scale excavation of soil which results in change in topography
2	Construction of vehicular road access and associated operation of large vehicles and machineries
3	Possible erection of any associated waste management ancillary facilities
4	The SBA where excess excavated material from the main landfill bowl is temporarily stored as spoil mound. The SBA is normally constructed in a number of phases to match the programme of landfill earthworks.
	Restoration and Aftercare Phase
5	Final cap construction
6	Grading to achieve final landfill contour

Table 8.10: Landscape Impact Assessment (without mitigation) - LCAs

LCAs	Description	Qty. Loss / Total Qty within study area	Sensitivity	Magnitude of Change		Significance threshold without mitigation
LCAs	Description	Qty. Loss / Total Qty within study area	Sensitivity	During Construction and operation	During restoration and aftercare	During Construction and operation	During restoration and aftercare
LCA1	Disturbed land (Existing NENT Landfill Site)	35.2/90.2	Low	Negligible	Negligible	Negligible	Negligible
LCA2A	Rural Settlement Landscape (Tong To Shan Tsuen & Ngong Tong)	14.2/66.5	High	Large	Intermediate	Significant	Moderate to Significant
LCA2B	Rural Settlement Landscape (Ping Yuen)	0.0/15.9	Medium	Negligible	Negligible	Negligible	Negligible
LCA3A	Upland Landscape (NW Facing slope of Robin’s Nest)	0.78/32.4	Medium	Negligible	Negligible	Negligible	Negligible
LCA3B	Upland Landscape (SE facing slope of Wo Keng Shan)	0.1/54.1	High	Negligible	Negligible	Negligible	Negligible
LCA3C	Upland Landscape (NW facing slope of Wo Keng Shan)	13.1/40.1	Medium	Intermediate	Small	Moderate	Slight to Moderate

Table 8.11: Landscape Impact Assessment (without mitigation) - LRs

LRs	Description	Qty. Loss / Total Qty within study area	Sensitivity	Magnitude of Change		Significance threshold without mitigation
LRs	Description	Qty. Loss / Total Qty within study area	Sensitivity	During Construction and operation	During restoration and aftercare	During Construction and operation	During restoration and aftercare
LR1	Woodland	1.5/ 72.7 Refer section 8.4.1.2 for preliminary tree assessment	High	Small	Small	Moderate	Moderate
LR2	Shrubland	5.8/26.1	Medium	Intermediate	Intermediate	Moderate	Moderate
LR3	Grassland	21.2/95.5	Medium	Intermediate	Intermediate	Moderate	Moderate
LR4	Agricultural Field	0.0/13.0	Medium	Negligible	Negligible	Negligible	Negligible
LR5	Natural Stream course	0m/505m length	High	Negligible	Negligible	Negligible	Negligible
LR6	Existing NENT Landfill Site and associated Stockpile and Borrow Area (SBA)	35.2/90.2	Low	Negligible	Negligible	Negligible	Negligible

Table 8.12: Visual Impact Assessment (without mitigation)

VSRs	Description	Sensitivity	Magnitude of Change		Significance threshold without mitigation
VSRs	Description	Sensitivity	During Construction and operation	During restoration and aftercare	During Construction and operation	During restoration and aftercare
VSR1	Tong To Shan Tsuen	Low	Large	Large	Moderate	Moderate
VSR2	Lin Ma Hang	High	Intermediate	Intermediate	Moderate to Significant	Moderate to Significant
VSR3	Wo Keng Shan Tsuen	High	Small	Small	Moderate	Moderate
VSR4	Ping Yeung	High	Small	Small	Moderate	Moderate
VSR5	Ping Che, Ping Che New Village, Pak Hok Shan, Kai Fong Garden	Medium	Small	Small	Slight to Moderate	Slight to Moderate
VSR6	Sing Ping Village, Tai Po Tin and government farm	Medium	Small	Small	Slight to Moderate	Slight to Moderate
VSR7	Kaw Liu Village, Kan Tau Wai, Ta Kwu Ling Village, Fung Wong Wu, Tong Fong and Chow Tin Tsuen	Medium	Small	Small	Slight to Moderate	Slight to Moderate
VSR8	Sheung Shan Kai Wat and Ha Shan Kai Wat	Low	Small	Small	Slight	Slight
VSR9	Hikers at the top of Robin’s Nest	High	Large	Large	Significant	Significant
VSR10	Ha Heung Yuen and Heung Yuen Wai	Medium	Small	Small	Slight to Moderate	Slight to Moderate
VSR11	Chuk Yuen	Medium	Small	Small	Slight to Moderate	Slight to Moderate
VSR12	Potential future users at the existing NENT Landfill site during its aftercare period	Medium	Large	Large	Moderate to Significant	Moderate to Significant

8.6.2 Cumulative Impacts Assessment Frameworks

The potential concurrent projects that may have cumulative landscape and visual impact on the Project is the existing NENT Landfill Site.

The Project site of the Landfill Extension is mainly made up largely by the Stockpile and Borrow Area and haul roads of the existing NENT Landfill Site. Furthermore, the existing NENT Landfill Site is located immediately adjoining to the northwest of the proposed extension. The existing NENT Landfill site is essentially of the same nature as the Project. They are therefore considered compatible in terms of both land use and landscape character.

It is predicted that shortly after the commencement of the construction and operation of the landfill extension, the existing landfill site will be close to its full capacity and will approach its restoration and aftercare phrase.

Therefore, no insurmountable landscape and visual impact from cumulative impact of concurrent project is anticipated for the Project.

8.6.3 Mitigation Measure and Residual Impact

8.6.3.1 General Mitigation Measures

The restoration and afteruse phases are a form of the mitigation measures of the proposed development. As most of the mitigation measures proposed during the construction and operation phases are temporary and limited, the permanent and effective mitigation measures for the proposed development are implemented in the restoration and afteruse phases. The aftercare phase mainly involves on going monitoring of the environmental indicators, and undertaking of all necessary actions to prevent pollution of the environment and harm to human health.

It is envisaged that the proposed landfill extension will be restored to blend in with the restored NENT Landfill, and both will blend in with the surrounding natural landscape. The restored landfill will be used for low intensity recreational purpose. Therefore, the landscape and visual impact during restoration and afteruse phases are considered minimal.

Mitigation Measures to be applied during construction, operation, restoration and aftercare phases are listed in Table 8.13a and b and Drawing No. 24315/14/009.

Table 8.13a: Mitigation measures in construction and operation phases

Strategies	Mitigation Measures in Construction and Operation Phases
MM1	Advanced screening tree planting · Early planting using fast growing trees and tall shrubs at strategic locations within site to block major view corridors to the site from the VSRs, and to locally screen haul roads, excavation works and site preparation works. · Roadside planter and shrub planting design in front of Cheung Shan Monastery.
MM2	Boundary Green Belt planting · Considerable planting belts proposed around the site perimeter and the construction of temporary soil bunds would screen the landfill operations to a certain degree. Fast growing and fire resistant plant species will be used.
MM3	Temporary landscape treatment as green surface cover · For certain areas where landfilling operations would have to be suspended temporarily for a certain period of time, simple temporary landscape treatment such as temporary green colour slope cover should be considered. The period of temporary suspended operation should be sufficiently explicit in order to undertake appropriate temporary landscape treatment. During construction and operation phases, synthetic covering material of green colour should also be used as a temporary slope cover where applicable. Given the extensive area of the proposed extension, development of the site should be divided into phases to minimize the visual impact.
MM4	Existing tree preservation · No trees should be felled or transplanted unless they are inevitably affected by the Project. Affected trees should be transplanted under circumstances where technically feasible. A tree survey report should be prepared and a tree felling application should be submitted to government during the detail design stage for approval before site formation works commence. The numbers, locations, species and sizes of the trees to be transplanted or felled should be clearly addressed.

Table 8.13b: Mitigation measures in restoration and aftercare phases

Strategies	Mitigation Measures in Restoration and Afteruse Phases
MM5	Sensible final contour grading · The final landfill will provide a structurally stable and visually interesting landform, which is visually compatible with surrounding landscape and contoured to simulate adjacent undeveloped area. Introduction and continuation of natural features such as spurs, ridges and valleys will be considered where appropriate.
MM6	Sufficient cover soil of landfill final capping · Sufficient cover soil of landfill final capping will be placed above the low-permeable layer and drainage layer, so as to sustain the proposed planting. The cover soil layer should be a minimum of 500mm in thickness for grassland, a minimum of 700mm for shrubland and 1000mm for woodland. Immediately after the completion of localized earthworks for the cover soil layer, the soil surface should be stabilized and greened by grass hydroseeding prior to subsequent landscape planting.
MM7	Landscape planting and maintenance · Planting and maintenance to allow vegetation establishment to match the natural vegetation of the surroundings. · Planting layout to establish a coherent pattern of woodland, shrubland and grassland vegetation. · To compensate for the loss of existing trees, 26.83 ha (43% of the Project site) will be planted with woodland mix progressively in phases. Assuming tree seedlings/whips planting at 1.5m spacing in staggered pattern, there will be about 148,100 nos. of tree seedlings/ whipsplanted. In addition, 19 ha of shrubland mix planting and 17.55 ha of grassland are proposed.

A landfill site is closed upon completion of the operation phase when its filling capacity is reached. When a landfill site is closed, it is capped with a low-permeable material. Normally, capping involves an impermeable HDPE liner and then follows by a thick layer of inert soil, usually about 1 to 1.5m thick, and compacted by machinery up to 1.2 tonnes per cubic meter. To further prohibit gas migration and infiltration of rainwater into the landfill, a synthetic impermeable layer will be laid underneath this layer of compacted soil cover. Restoration of a closed landfill site involves placing of cover soil, revegetation and on-going maintenance works.

Landfill cover soil is normally nutrient deficient, especially in nitrogen. Application of fertilizer is therefore necessary. Planting of N-fixing plants can also increase the nutrient level of cover soil. Another feature of landfill cover soil is its high degree of compaction. The level of CO₂ in cover soil is also relatively high.

Due to the presence of the impermeable cap, the moisture retained inside the landfill cannot reach to the cover soil by capillary action. Therefore, water supply for plants is generally inadequate, especially in dry season. Plants should therefore be drought resistant.

Tree planting has not been recommended in closed landfill sites previously as trees were suspected to damage the landfill top liner. However, evidence indicated that tree roots would not penetrate deep into the top cover soil which had a high degree of compaction and a high level of CO₂. A study on the root growth patterns of Acacia confusa and Casuarina equisetifolia in two local completed landfill sites revealed that their roots were mostly confined to the upper 15 cm of topsoil and did not penetrate further down. (G Y S Chan 1997). The proposed 1 m thick landfill cap is unlikely to be damaged by the growth of tree roots.

With high quality of composite cap, leachate contamination and landfill gas migration to cover soil is unlikely. Though the physical and chemical characteristics of cover soil as discussed above are unfavourable to most plants, field observation and experiments have confirmed that there are some tree species suitable for growing in landfill. Most of these trees are legumes which are N-fixing, tolerant to landfill gas and/or leachate, and drought resistant.

Reference is made to many local researches carried out on revegetation of landfill sites, which are listed below:

· G Y S Chan and M H Wong, 2002. Revegetation of Landfill Sites. In: Encyclopaedia of Soil Science, p. 1161 -1166

· G Y S Chan, 1997. Root Growth Patterns of Two Nitrogen-fixing Trees Under Landfill Conditions. In: Land Contamination and Reclamation 5:55-62.

· G Y S Chan, M H Wong and B.A. Whitton, 1996. Effects of Landfill Factors on Tree Cover – A Field Survey at 13 Landfill Sites in Hong Kong. In: Land Contamination and Reclamation 4: 115-128.

The superior performance of Acacia confusa, A. magium and A. auriculiformis on landfill sites was mainly due to their high drought tolerance and the N-fixing property. Due to their high drought tolerance, Tristania conferta, Eucalyptus citriodora and E. torelliana are some of the non-legumes which also showed superior performance in landfill.

However, most native trees had extremely high mortalities on the local test site in the first few years after the capping of landfill. After several years, the pioneer species provide shelter for the native species and the survival rate and growth of native species will improve. Natural ecological succession also takes place as the pioneer species establishes. Therefore, planting of tree seedlings is preferable to be carried out in two phases. The first phase involves planting of landfill pioneers tree species. The second phase, 3 – 5 years after the completion of first phase, involves the planting of seedlings of native tree species of higher ecological values.

To compensate for the loss of existing trees, 26.83 ha of the site (43% of the Project site) will be planted with woodland mix progressively in phases. Assuming tree seedlings/whips planting at 1.5m spacing in staggered pattern, there will be about 148,100 nos. of tree seedlings/ whips planted. In addition, shrubland mix planting and grassland planting areas will also be created.

Table 8.14 shows the trees suggested for initial woodland establishment in subtropical landfill site by G Y S Chan (2002).

Table 8.14: Tree species for woodland mix planting on restored landfill site

Landfill pioneer tree species for woodland mix planting (1^st phase planting – immediately after final capping of landfill)

Acacia auriculiformis *

Acacia confusa*

Acacia mangium*

Albizia lebbek*

Aleurites moluccana

Cassia siamea*

Casuarina equisetifolia*

Cassia spectabilis*

Eucalyptus citriodora

Eucalyptus torelliana

Machilus spp. Schima superba

Castanopsis fissa

Peltophorum pterocarpum*

Tristania conferta

Native tree species with high ecological value for woodland mix planting (2nd phase – 3 to 5 years after the completion of first phase planting)

Note: Trimming or thinning of pioneer trees in the established 1^st phase planting is required immediately before the 2^nd phase planting and after 5 to 10 years from completion of 2^nd phase planting

Aquilaria sinensis#

Antidesma microphyllum#

Ardisia quinquegona#

Bridelia tomentosa#

Castanopsis spp.#

Choerospondias axillaries#

Cinnamomum spp.#

Cyclobalanopsis edithiae#

Cyclobalanopsis neglecta#

Ficus spp.#

Garcinia oblongifolia#

Gordonia axillaries#

Ilex spp.#

Lithocarpus spp#

Litsea glutinosa#

Liquidamber formosana#

Machilus breviflora#

Microcos paniculata#

Myrica rubra#

Reevesia thyroidea#

Sapium discolor#

Schefflera octophylla#

Schima superba#

Sterculia lanceolata #

Syzygium hancei#

Tutcheria championii#

Remark: “*” marks N-fixing species. “#” marks native species.

Based on the shrub community found within and near the existing NENT Landfill site, the following shrubs are proposed for shrubland mix planting.

· Baeckea frutescens#

· Rhodomyrtus tomentosa#

8.6.3.2 Implementation Programming/Sequencing

An implementation programme is prepared as required by the TM of the EIAO. Reference is made to the ETWB TC(W) No. 2/2004 on Maintenance of Vegetation and Hard Landscape Features (to be read in conjunction with WBTC(W) No. 14/2002) which defines the management and maintenance responsibilities for natural vegetation and landscape works, including both softworks and hardworks, and the authorities for tree preservation and felling. The funding, implementation, management and maintenance arrangement is listed in Table 8.15.

Table 8.15: Preliminary funding, implementation, management and maintenance proposal

	Mitigation items	Funding & Implementation unit	Management and maintenance unit
Mitigation Measures in Construction and Operation Phases
MM1	Advanced screening tree planting	DBO Contractor	DBO Contractor
MM2	Boundary Green Belt planting	DBO Contractor	DBO Contractor
MM3	Temporary landscape treatment as green surface cover	DBO Contractor	DBO Contractor
MM4	Existing tree preservation	DBO Contractor	DBO Contractor
Mitigation Measures in Restoration and Aftercare Phases
MM5	Sensible final contour grading	DBO Contractor	DBO Contractor
MM6	Sufficient cover soil of landfill final capping	DBO Contractor	DBO Contractor
MM7	Landscape planting and maintenance	DBO Contractor	DBO Contractor

Note: Details of the mitigation measures are given in Tables 8.13a and 8.13b. The mitigation measures shall be stipulated in the Employer’s Requirements and Environmental Permits when tendering the Design-Build-Operating Contract to ensure that the mitigation measures will be implemented by the DBO Contractor.

8.6.3.3 Residual Landscape Impact Assessment Frameworks (with Mitigation)

The residual landscape impacts (with mitigation) on LCAs are presented in Table 8.16. The residual landscape impacts (with mitigation) on LRs are presented in Table 8.17.

Table 8.16: Summary of residual landscape impacts (with mitigation) on LCAs

LCAs	Significance threshold without mitigation		Residual impact after implementation of mitigation measures
LCAs	Construction and Operation	Restoration and Aftercare	Construction and Operation	Restoration and Aftercare
LCA1 Disturbed land (Existing NENT Landfill Site)	Negligible	Negligible	Negligible	Negligible (Beneficial with mitigation measures)
LCA2A Rural Settlement Landscape (Tong To Shan Tsuen & Ngong Tong)	Significant	Moderate to Significant	Significant	Moderate (Acceptable with mitigation measure)
LCA2B Rural Settlement Landscape (Ping Yuen)	Negligible	Negligible	Negligible	Negligible
LCA3A Upland Landscape (NW Facing slope of Robin’s Nest)	Negligible	Negligible	Negligible	Negligible
LCA3B Upland Landscape (SE facing slope of Wo Keng Shan)	Negligible	Negligible	Negligible	Negligible
LCA3C Upland Landscape (NW facing slope of Wo Keng Shan)	Moderate	Slight to Moderate	Moderate	Slight (Acceptable with mitigation measure)

Table 8.17: Summary of residual landscape impacts (with mitigation) on LRs

LRs	Significance threshold without mitigation		Residual impact after implementation of mitigation measures
LRs	Construction and Operation	Restoration and Aftercare	Construction and Operation	Restoration and Aftercare
LR1 Woodland	Moderate	Moderate	Moderate	Slight to Moderate (Acceptable with mitigation measure)
LR2 Shrubland	Moderate	Moderate	Slight to Moderate	Slight (Acceptable with mitigation measure)
LR3 Grassland	Moderate	Moderate	Slight to Moderate	Slight (Acceptable with mitigation measure)
LR4 Agricultural Field	Negligible	Negligible	Negligible	Negligible
LR5 Natural Stream course	Negligible	Negligible	Negligible	Negligible
LR6 Existing NENT Landfill Site and associated Stockpile and Borrow Area (SBA)	Negligible	Negligible	Negligible	Negligible (Beneficial with mitigation measure)

8.6.3.4 Residual Visual Impact Assessment Frameworks (with Mitigation)

The residual visual impacts (with mitigation) on VSRs are presented in Table 8.18.

Table 8.18: Summary of residual Visual Impacts (with Mitigation) on VSRs

VSRs	Significance threshold without mitigation			Residual impact after implementation of mitigation measures
VSRs	Construction and Operation	Restoration and Aftercare	Construction and Operation		Restoration and Aftercare
VSR1 Tong To Shan Tsuen	Moderate	Moderate	Moderate		Slight to Moderate (Acceptable with mitigation measure)
VSR2 Lin Ma Hang	Moderate to Significant	Moderate to Significant	Moderate to Significant		Moderate (Acceptable with mitigation measure)
VSR3 Wo Keng Shan Tsuen	Moderate	Moderate	Moderate		Slight to Moderate (Acceptable with mitigation measure)
VSR4 Ping Yeung	Moderate	Moderate	Moderate		Slight to Moderate (Acceptable with mitigation measure)
VSR5 Ping Che, Ping Che New Village, Pak Hok Shan, Kai Fong Garden	Slight to Moderate	Slight to Moderate	Slight to Moderate		Slight (Acceptable with mitigation measure)
VSR6 Sing Ping Village, Tai Po Tin and government farm	Slight to Moderate	Slight to Moderate	Slight to Moderate		Slight (Acceptable with mitigation measure)
VSR7 Kaw Liu Village, Kan Tau Wai, Ta Kwu Ling Village, Fung Wong Wu, Tong Fong and Chow Tin Tsuen	Slight to Moderate	Slight to Moderate	Slight to Moderate		Slight (Acceptable with mitigation measure)
VSR8 Sheung Shan Kai Wat and Ha Shan Kai Wat	Slight	Slight	Slight		Slight (Acceptable with mitigation measure)
VSR9 Hikers at the top of Robin’s Nest	Significant	Significant	Significant		Moderate to Significant (Acceptable with mitigation measure)
VSR10 Ha Heung Yuen and Heung Yuen Wai	Slight to Moderate	Slight to Moderate	Slight to Moderate		Slight (Acceptable with mitigation measure)
VSR11 Chuk Yuen	Slight to Moderate	Slight to Moderate	Slight to Moderate		Slight (Acceptable with mitigation measure)
VSR12 Potential future users at the existing NENT Landfill site during its aftercare period	Moderate to Significant	Moderate to Significant	Moderate to Significant		Moderate (Acceptable with mitigation measure)

8.6.3.5 Photomontage Illustration from Selected Views

According to EIAO Guidance Note No. 8/2002, photomontages at selected representative viewpoints are prepared on Drawing Nos. 24315/14/010 to 012 to illustrate the effectiveness of the proposed impact mitigation proposal and residual impacts of the development in both short and long term for:

· Existing baseline condition (Day 1 of Construction and Operation phases)

· Development without mitigation (Day 1 of Afteruse Phase)

· Development with mitigation (Day 1 of Afteruse Phase)

· Development with mitigation (10 years of Afteruse Phase)

A total of 3 representative viewpoints are selected. They are:

· View of VSR2 at Lin Ma Hang

· View of VSR7 at Ta Kwu Ling Village

· View of VSR11 at Chuk Yuen

8.7 Conclusion

The NENT Landfill Extension consists mainly the Stockpile and Borrow Area and haul roads of the existing NENT Landfill Site. Furthermore, the existing NENT Landfill Site is located immediately adjoining to the northwest of the proposed extension. The existing landscape resources and characters of the extension site are therefore largely deteriorated by both the existing NENT Landfill and its Stockpile and Borrow Area.

In terms of residual landscape impact, it is concluded that with implementation of mitigation measures, the NENT Landfill Extension will have slight impact to the upland landscape at the northwest facing slope of Wo Keng Shan (LCA3C) and moderate impact to rural settlement Landscape of Tong To Shan Tsuen & Ngong Tong (LCA2A). Furthermore, it is assessed that there will be slight to moderate residual impact to the woodland (LR1) and slight residual impact to shrubland (LR2) and grassland (LR3) within the Project site. The lost of 1.5 ha of existing woodland and 5.8 ha of shrubland will be compensated by 26.83 ha of woodland mix progressively planted in phases with about 148,100 nos. of tree seedlings / whips. In addition, 19 ha of shrubland mix planting and 17.55 ha of grassland will be created in the restoration phase of the NENT Landfill Extension.

The existing NENT Landfill site, its Stockpile and Borrow Area and the proposed NENT Landfill Extension will affect the same sets of visual sensitive receivers in view of their proximity to each other. It is noted that the landscape character of the NENT Landfill Extension will be similar to that of the existing landfill site and its associated Stockpile and Borrow Area. In terms of residual visual impact, the extension site will have slight impact to the majority of the identified visual sensitive receivers. Moderate to significant impact is expected to hikers at the top of Robin’s Nest (VSR 9), whereas moderate impact is expected to visual sensitive receivers at Lin Ma Hang (VSR 2) and to potential future users at the existing NENT Landfill site during its aftercare period. (VSR12).

The proposed landfill extension will be restored and vegetated to match with its surrounding landform and vegetation patterns in the restoration and aftercare stages. In summary, the overall landscape and visual impact of the Project is acceptable with mitigation measures implemented.

9 Impact on Cultural Heritage

9.1 Introduction

This chapter presents the cultural heritage impact assessment of the Project, identifying cultural heritage resources such as archaeological sites, built heritage structures and cultural and historical landscape features. The archaeological investigation did not identify any archaeological material or cultural layers, thus no mitigation measures are recommended. A number of built heritage resources will be affected by the Project, including 13 graves and 1 boulder path. Mitigation in the form of preservation by detailed record for all of the resources will be required during detailed design stage by the DBO Contractor.

The cultural heritage assessment has been conducted in accordance with the requirements of Annexes 10 and 19 of the TM-EIAO and Claus 3.4.7 of the EIA Study Brief for the Project.

9.2 Environmental Legislation & Standards

The relevant legislation and associated guidance notes applicable to the study for the assessment of impact on cultural heritage include:

· Antiquities and Monuments Ordinance, Cap 53;

· Environmental Impact Assessment Ordinance (EIAO), Cap. 499; and

· Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO).

9.2.1 Antiquities and Monuments Ordinance (Cap.53)

The Antiquities and Monuments Ordinance (Cap. 53) was enacted in 1976. It provides the statutory framework for the preservation of objects of historical, archaeological and palaeontological interest. The Ordinance contains the statutory procedures for the Declaration of Monuments. Monument proposed can be any place, building, site or structure, which is considered to be of public interest by reason of its historical, archaeological or palaeontological significance. It should be noted that the protective measures contained in the ordinance only pertain to Declared or Deemed Monuments.

9.2.2 Environmental Impact Assessment Ordinance (Cap.499)

The EIAO provides additional legislative protection to sites of cultural heritage, which are threatened by development and the EPD is the enforcing authority. It stipulates guidelines and criteria for the assessment of sites of cultural heritage interest.

9.3 Description of the Study Area

The study area for the cultural heritage impact assessment (CHIA) consists of the Project area and all land within 50 metres of its boundary. A map showing the finalised layout plan is shown in Drawing No. 24315/13/601. For the purposes of site investigation, the study area has been divided into four sections, and the divisions are illustrated on Drawing No. 24315/13/602 for ease of reference only.

9.3.1 Ngong Tong (North and West of Shek Tsai Ha Road: western and central section)

Ngong Tong terrain is typical of a landscape underlain by volcanic rocks. The hills in the Ngong Tong area rise to as high as +160 mPD and as can be seen in the photographs in Plates 1 and 2 in Appendix 9.1, the hillsides are very steep with scrubby vegetation, dominated by thick brushy ferns, and shallow soil deposits with outcroppings of rock commonly seen. The existing landscape has also been formed through result of gulley erosion and mass movements (specifically, debris slides). Plate 3 in Appendix 9.1, shows the result of a very recent debris slide.

There are three valleys in this part of the study area. All of the valleys can only be reached by descending down very steep slopes. The valley floors are very narrow ranging from approximately one metre in width at their narrowest points to a maximum of approximately ten metres at their widest points. The valley floors were also found to be marshy and covered by thick vegetation.

9.3.2 Tong To Shan (North of Shek Tsai Ha Road: east section)

Tong To Shan section consists of hillsides to the south of the valley where the primary remains of the historical settlement of Tong To Shan were located during the 2001 HKIA survey. The existing highest point in Tong To Shan is about +158 mPD. The slopes in this area range from very steep to moderate (Plates 4 and 5 in Appendix 9.1). There are short and narrow depressions (1 to 2 metres in width) at the higher elevations, mainly situated in saddles between the hilltops. The highest elevations, (Plate 6 in Appendix 9.1) contain the same scrubby vegetation, shallow soil and rock outcrops as described for the other parts of the NLES, although, not surprisingly, the more sheltered saddle depressions have thicker vegetation. The lower sections of the hillsides, however, are of a different character and contain more substantial vegetation with some sections actually being quite heavily wooded (Plate 7 in Appendix 9.1. Several of the small valleys have been artificially terraced. The valleys also show evidence of water erosion, in the form of gullies and with sections of hillsides washed away.

9.3.3 Shek Tsai Ha (South of Shek Tsai Ha Road: western section)

Shek Tsai Ha area is similar in nature to that of Ngong Tong, though it consists of even steeper mountain sides, again interspersed with narrow valleys. Vegetation is scrubby, except in the relatively sheltered valleys, where stands of trees have taken hold. The highest elevations of the existing range are between 170 and 200mPD (Plates 8 and 9 in Appendix 9.1).

9.3.4 Wo Keng Shan (South of Shek Tsai Ha Road: eastern section)

Wo Keng Shan area consists of a narrow band of land around the south-eastern boundary of the existing NENT Landfill site. The existing terrain is mountainous, being over 200 mPD in elevation (Plates 10 and 11 in Appendix 9.1).

9.4 Archaeology

9.4.1 Assessment Methodology

The methodology for the Archaeological Impact Assessment (AIA) is discussed in the following subsections.

9.4.1.1 Desk-based study

A desk-based study was carried out in order to identify any known or potential sites of archaeological interest. The following resources were consulted: the Antiquities and Monuments Office (AMO) published and unpublished papers and studies; publications on relevant historical, anthropological and other cultural studies; unpublished archival, papers, records; collections and libraries of tertiary institutions; historical documents which can be found in Public Records Office, Lands Registry, District Lands Office, District Office, Museum of History; cartographic and pictorial documentation; and existing geotechnical information. The desk-based study also included a review of all relevant impact assessment studies.

9.4.1.2 Preliminary site investigation

A surface field scan was undertaken to supplement the information gathered during the desk-based study. This was carried out by field walking of the natural landscape in a systematic manner, with attention to areas of exposed soil and recent cuts. This information was used to evaluate the archaeological potential of the study area and to determine if any further field evaluation, i.e. auger testing and test pit excavation would be necessary.

9.4.1.3 Field evaluation programme

As a result of the desk-based study and preliminary site investigation it was decided that an archaeological field evaluation would be required, the scope of which had been agreed with the AMO prior to implementation. The field evaluation consisted of an auger survey and test pit excavation.

9.4.1.4 Impact assessment and mitigation recommendations

An assessment of impacts according to the requirements of Annexes 10 and 19 of the TM-EIAO was undertaken and appropriate mitigation measures were presented where applicable.

9.4.2 Results of the Desk Based Study

9.4.2.1 Geological and topographical information

The solid geology of the study area is dominated by volcanic rocks, specifically, undivided coarse ash crystal tuff. This terrain is typified by moderate to steep slopes with gently concave side slopes and narrow convex ridges (Shaw et al 2000). Superficial deposits consist of unsorted debris flow made up of a mixture of gravely and clayey silt/sand with cobbles and boulders (Drawing No. 24315/13/603).

Topographically, the existing study area is dominated by steeply sloped hills with narrow valleys. The maximum elevations are approximately +180 to +200 mPD with an average around +150 mPD. The lowest elevations associated with the study area are approximately +100 to +110 mPD and are located on the valley floors and at the far northern and north-western sections of the study area, (i.e. to the northwest of Ngong Tong).

An aerial photograph taken in 1999 shows no evidence of any past settlement or agricultural cultivation in the study area (Plate 12 in Appendix 9.1). This is in contrast with another aerial photograph taken in 1999, of the hill slopes to the north of the study area, i.e. between the village of Lin Ma Hang and the abandoned village house at Tong To Shan, (Plate 13 in Appendix 9.1).

9.4.2.2 Previous Investigations

Archaeological material from the following periods has been recorded in the vicinity of the study area:

· Ming Dynasty AD 1368 - 1644

· Qing Dynasty AD 1644 – 1911

This material has been found in the area designated as the “Tong To Shan Archaeological Site”. The historical background of the two villages in the vicinity of the study area, i.e. Tong To Shan and Lin Ma Hang can be found in the Built Heritage section of this report.

An archaeological survey, which included the Project area was carried out by the Hong Kong Institute of Archaeology (HKIA 2001). The survey included excavation of 4 test pits in the Ngong Tong and the boring of 120 auger holes in Ngong Tong and Tong To Shan. Two of the test pits were located on the top of Ngong Tong Shan and revealed a few historical shreds immediately below topsoil. The other test pits were located in the foothills; some glazed historical shreds were recorded from the topsoil layer. The locations of the test pits and auger holes can be found in Drawing No. 24315/13/604 (HKIA 2001).

The 2001 HKIA report noted the importance of the Tong To Shan Archaeological Site as a cultural heritage resource. However, the investigation (HKIA 2001) did not identify any subsurface cultural layers in the CHIA study area. The small numbers of historical shreds found in topsoil were associated with the historical graves, which was neither settlement nor agricultural activity. The extensive auger survey, carried out in Ngong Tong did not identify any areas of archaeological potential. No further survey or testing was recommended.

9.4.3 Results of the Preliminary Archaeological Site Investigation

All sections of the study area for the finalised Layout Plan, Drawing No. 24315/01/107 were visited as part of the field scan. The terrain of much of the study area is mountainous and covered in heavy shrub vegetation. For purposes of this investigation, the study area has been divided into four sections for ease of reference, the divisions are illustrated on Drawing No. 24315/13/602. A summary of the archaeological potential of the four sections is provided below and recommendations for further field evaluation can be found in Table 9.1.

9.4.3.1 Ngong Tong (North and West of Shek Tsai Ha Road: western and central section)

The surface field scan showed the study area to be unchanged from that described in 2001. The previous archaeological investigation did not identify any archaeological deposits in Ngong Tong during either their auger testing programme or test pit excavations. These findings were consistent with the nature of the landscape, i.e. steep hillsides dominated by thin topsoil, numerous rock outcrops and evidence of history of mass movements and gully erosion. The surface field scan also did not identify indications of any previous land usage, apart from the historical grave sites, and sections of a boulder path, thus, reaffirming the 2001 report’s conclusion that the Ngong Tong area has extremely low potential for containing any sub-surface cultural deposits.

9.4.3.2 Tong To Shan (North of Shek Tsai Ha Road: eastern section)

The 2001 survey did not identify any sub-surface archaeological material in this section of the study area and no evidence of archaeological surface material was identified during the current field scan. A number of cultural landscape features were identified, in the form of agricultural terraces and boulder paths and it is possible that sub-surface archaeological resources may exist in proximity to visible features.

9.4.3.3 Shek Tsai Ha (South of Shek Tsai Ha Road: western section)

The surface field scan did not identify any archaeological material and no land use features were identified in this part of the study area. The slopes in this area are steeper and slightly higher than those in Ngong Tong, but otherwise similar in nature. The potential for this area to contain any subsurface cultural deposits is extremely low. The reasons being the same as those stated for Ngong Tong.

9.4.3.4 Wo Keng Shan (South of Shek Tsai Ha Road: eastern section)

Wo Keng Shan consists of two narrow sections of mountain-tops. The surface field scan did not identify any archaeological material. No land use features were identified in this part of the study area. The area is located at very high elevations and the likelihood of any archaeological remains is extremely low.

Table 9.1: Recommendations for further archaeological field evaluation

Location	Description (based on Field Scan)	Archaeological potential, i.e. presence of subsurface cultural layers	Recommendations
Ngong Tong	Steeply sloped hills with scrubby vegetation and numerous rock outcrops and narrow swampy valleys. No evidence of past land usage, apart from the presence of grave sites.	Extremely Low	No further field investigation
Shek Tsai Ha	Steeply sloped hills with scrubby vegetation and numerous rock outcrops. No evidence of past land usage apart from the presence of grave sites.	Extremely Low	No further field investigation
Wo Keng Shan	The upper elevations of steeply sloped hills.	Extremely Low	No further field investigation.
Tong To Shan	The southern part of this section consists of steeply sloped hillsides with a mixture of scrubby vegetation and woodland with numerous rock outcrops. The northern section has hillsides that are less steep and more heavily wooded.	Low	An area has been highlighted for archaeological testing as shown in Drawing No. 24315/13/604. As this area is not large and consists mainly of steep hillslopes. Two 1m x 1m test pit and 10 auger holes were conducted.

9.4.4 Results of the Archaeological Field Evaluation

As a result of the field scan, it was agreed that a field evaluation would be carried out in the Tong To Shan section of the study area. A full report of the archaeological investigation was prepared and approved by AMO prior to the submission of this EIA report. The following section presents a summary of the findings from the archaeological investigation.

9.4.4.1 Results of the auger test programme

A total of ten auger hole tests were conducted within the area identified for further archaeological investigation (Drawing No. 24315/13/604). The results indicated that the hill slope and terraces consist of moderate to deeply weathered colluviums. The auger hole depths ranged between 0.27 and 1.49 metres in depth. No archaeological material was recovered during the auger testing.

9.4.4.2 Results of the Test pit Excavations

A total of two test pits were conducted. Locations of the test pits are shown in Drawing No. 24315/13/604.

Test Pit 1 measured one by one metre and was located near the boulder path (BP2) on boulder terrace (T1). The test pit was hand excavated to a depth of approximately 0.80 metres when the excavation was halted due to safety standards. The temporary benchmark is located to the south of the test pit at the base of the tree marked No. 859. A general view of the test pit area can be seen in the photograph in Plate 14 (in Appendix 9.1).

A total of three contexts were recorded. Context 01: topsoil, was very dark grey very clayey, gravely and slightly sandy silt with many roots. It was recorded for a maximum depth of 0.11 metres. It contained no archaeological material. Context 02 consisted of light brownish grey very clayey and slightly gravely silt subsoil. There were no archaeological finding in this layer; its inclusions were smallish mainly sub-angular rocks and roots. Context 02 had a thickness between 0.19 and 0.32 metres. Context 03 was a light brown sterile colluvial layer, which consisted of very silty, gravely and slightly sandy clay. Context 03 contained many angular to sub-angular rocks and was recorded to a depth of 0.71 metres below the surface. The East and South section drawings are shown in Drawing No. 24315/13/605. A photograph of the East section is given in Plate 15 and the South section in Plate 16 (in Appendix 9.1).

Test Pit 2 measured one by one metre and was located on boulder terrace (T7) between boulder path (BP2) and the stream to the east of the terrace. It was hand excavated to a depth of 0.34 metres when the excavation was halted due to decomposing rock. The temporary benchmark is located to the north of the test pit at the base of the tree marked ‘X’. A general view of the test pit area can be seen in the photograph in Plate 17 (in Appendix 9.1).

A total of three contexts were recorded. Context 01, topsoil was very dark grey clayey, slightly gravely silt with roots. It was recorded for a maximum depth of 0.16 metres. It contained no archaeological material. Context 02 consisted of grey very gravely clayey silt subsoil. There were no archaeological finds in this layer; its inclusions were small mainly angular rocks. Context 02 had a thickness between 0.9 and 0.16 metres. Context 03 was brownish yellow decomposing rock, which consisted of clayey slightly gravely silt. Context 03 was recorded at a depth between 0.19 and 0.29 metres below the surface and contained no archaeological material. The East and South Section drawings for this test pit are shown on Drawing No. 24315/13/605. A photograph of the East section is illustrated in Plate 18 and the South section in Plate 19 (in Appendix 9.1).

9.4.5 Identification and Evaluation of Potential Impacts

Any sub-surface deposits within the NENT Landfill Extension area will be directly impacted by the Project, either through site formation works or during the operation of the landfill extension. The deposits would either be destroyed through site formation works during the construction phase or deemed inaccessible through deposition of waste material during the operation of the landfill extension.

9.4.6 Mitigation Recommendations

The mitigation recommendations are presented in Table 9.2.

Table 9.2: Mitigation recommendations for archaeology

Location

Archaeological Potential

Recommended Mitigation

Ngong Tong

Extremely low (based on the desk-based study and preliminary site investigation)

No further investigation required

Shek Tsai Ha

Extremely low (based on the desk-based study and preliminary site investigation)

No further investigation required

Wo Keng Shan

Extremely low (based on the desk-based study and preliminary site investigation)

No further investigation required

Tong To Shan

Extremely low (based on the findings of the archaeological investigation)

No further investigation required

9.5 Built Heritage

9.5.1 Assessment methodology

The methodology for the Built Heritage Impact Assessment (BHIA) consists of:

9.5.1.1 Desk-Based Study

The first stage of investigation was to undertake a desk-based study to determine the presence of historical occupation of the study area and to assess the potential for built heritage resources to be present. This study includes information gathered from the following sources: -

· The Antiquities and Monuments Office published and unpublished papers and studies;

· Publications on relevant historical, anthropological and other cultural studies;

· Unpublished archival, papers, records; collections and libraries of tertiary institutions;

· Historical documents which can be found in Public Records Office, Lands Registry, District Lands Office, District Office, Museum of History; and

· Cartographic and pictorial documentation.

The desk-based study also included a review of all relevant impact assessment studies.

9.5.1.2 Built Heritage Field Survey

Based on the findings of the desk-based survey it was decided that the existing information was not sufficient for the purposes of assessment and a built heritage field survey was carried out. This survey was undertaken to supplement the information gathered in the desk-based study and to determine the current status of the previously recorded resources as well as identify any resources that had not been previously recorded.

9.5.1.3 Definition of Features within the Scope of the Built Heritage Survey

Features within the scope of the built heritage survey are defined below:

· All pre 1950 structures; these include a wide range of built features such as domestic buildings, ancestral halls, temples, shrines, monasteries and nunneries, village gates, wells, schools, historic walls, bridges and stone tablets;

· Any post 1950 structure deemed to possess features containing architectural or cultural merit; All pre-war clan graves;

· Cultural landscape features, such as fung shui woods, historical tracks and pathways, stone walls and terraces, ponds and other agricultural features.

9.5.1.4 Recording Methodology

The detailed methodology for each of the categories of resources is presented as follows:

Built Features

The recording of resources includes the collection of photographic, oral and written information, on the architecture and history of any structures that may be impacted by the proposed works. Any relevant information is hand recorded in the field and then entered onto type written forms for inclusion in the report. The design of the forms is based on AMO and ICOMOS (International Charter for the Conservation and Restoration of Monuments and Sites) standards for the recording of historical resources with modifications to suit architectural styles and situations encountered in Hong Kong. The forms have also been designed to provide details of all identified resources, including written descriptions of each recorded feature, including; age, details of architectural features, condition, past and present uses, an architectural appraisal, notes on any modifications, direction faced and associations with historical/ cultural events or individuals. The location of each feature must also be highlighted on a 1:1000 scale map.

Graves

Detailed descriptions of pre-war clan graves are recorded on field recording forms, which included a written summary of the structural features, a photographic record, a copy of the inscription, orientation and the dimensions of the grave. The locations of any identified graves are also highlighted on a 1:1000 scale map.

Cultural and Historical Landscape Features

A written description of each recorded feature is made, including information gathered from interviews with local informants (if available). The location of each recorded feature has also been highlighted on a 1:1000 scale map and a photographic record made.

Impact Assessment and Mitigation Recommendations

Once all the resources within the study area have been recorded and mapped, any potential adverse impacts associated with the works will then be identified and assessed, as well as appropriate mitigation measures presented, if required.

9.5.2 Results of the Desk-based Study

A desk-based study was undertaken to review the information contained in previous reports as well as to provide more detailed information, if available. The following information was gathered in the desk-based study.

9.5.2.1 Declared Monuments

There are no Declared Monuments in the study area for the CHIA. This confirms the findings of the previous investigations.

9.5.2.2 Graded Historical Buildings

There are no Graded Historical Buildings in the study area. This also confirms the findings of previous investigations.

9.5.2.3 Ungraded Historical Buildings

There are no Ungraded Historical Buildings in the study area. This also confirms the findings of previous investigations.

9.5.2.4 Graves

The HKIA investigation report (2001) shows the locations of 20 graves or former grave sites in the study area for the finalised layout option. As part of the desk-based study 1:1000 scale maps were examined and more potential graves were identified. Based upon this information it was determined that a field survey would be carried out as part of the CHIA. Aerial photographs were also examined, but only one grave was clearly visible, see Plate 20 (in Appendix 9.1).

9.5.2.5 Cultural Landscape Features

The HKIA investigation report (2001) shows two boulder paths and approximately 20 boulder terraces in the vicinity of study area. A small section of one boulder path is the only cultural landscape feature that falls within the boundary of the Project area.

9.5.2.6 Historical Villages

There are no historical villages in the study area. There are, however, two historical villages located to the North and according to local informants, the boulder paths were used by residents of these villages and the graves identified in the study area are associated with them. A brief historical background of the two villages is provided as follows:

Lin Ma Hang : According to local informants (former and present village representatives), Lin Ma Hang was established approximately about 600 years ago. It was first founded by the Lau and Kwun clans, who were later joined by the Sin clan and lastly by the Hakka Yip clan from Po On, who settled here about 300 years ago. Nowadays, the village is almost occupied entirely by members of the Yip clan. There is only one Lau family still living in the village. Most of the clans, whether resident in the village or not still maintain their ancestral hall and members of the Lau and Kwun clans still come back to visit their ancestral halls every year. The Sin clan ancestral hall collapsed in the 1970s. The name "Lin Ma Hang" was derived from the fact that in the past, a lot of "lin ma" could be found in the stream. The villagers used to grow rice and sweet potatos and regularly took any extra rice and collected wood to Sha Tau Kok Hui and Shenzhen Hui for sale. According to local informants the historical graves at Ngong Tong belong to former residents of Lin Ma Hang, whose descendants immigrated a number of years ago. The informants also noted that a path between Lin Ma Hang and Ngong Tong had once existed, but that today it is not used and graves in Ngong Tong are now accessed through the NENT Landfill site.

Tong To Shan : There are two views on the timing of the founding of Tong To Shan according to local informants. Firstly, it is believed that Tong To Shan was settled by the Hakka Cheung family around the same time as Lin Ma Hang. Another opinion is that the village was settled at some point earlier than Lin Ma Hang. There were three fung shui houses in the village within living memory and all were originally built and occupied by members of the Cheung clan. The Cheungs eventually moved away, as they were no longer able to make a living in the area. A member of the Yip clan purchased all three houses and the surrounding land prior to 1929, with the land currently belonging to his grandson.

9.5.3 Results of the Built Heritage Field Survey

A field survey was undertaken to identify the full range of built heritage resources, as required by the EIA study brief. Two types of resources were identified; cultural landscape features and historical graves. The former consisted of 3 boulder paths, 9 boulder terrace features and the latter of 13 intact graves, 2 damaged graves, and 9 abandoned gravesites. Finally, 8 gravesites identified in the desk-based study, i.e. shown as graves on 1:1000 scale maps, were found to have no evidence remaining on site. The detailed recording forms of the identified resources can be found in Appendix 9.2 (Graves) and Appendix 9.3 (Boulder Terraces and Paths). A summary of the findings from the field survey is presented in this section.

9.5.3.1 Ngong Tong (North and West of Shek Tsai Ha Road: western and central section)

Historical Buildings

No historical buildings were identified in the field survey.

Graves

A total of 24 grave sites (including extant graves and sites of abandoned graves) were identified in the field survey. These included the graves identified in the 2001 HKIA report, as well as some that were not recorded as part of that study. A description of the graves is provided below and a catalogue of all the recorded historical graves, structurally modern graves and abandoned graves, with and without structural remains, is provided in Drawing No. 24315/13/606 (a 1:4000 scale A3 drawing showing the recorded grave sites),

· Grave 2 is a Qing Dynasty grave and consists of a concrete enclosure and platform with green brick wall structure. The grey stone plaque is set into a carved stone frame. The grave has a renovation date of 1801. See Drawing No. 24315/13/606 for location.

· Grave 3: Abandoned gravesite consisting of broken pieces of the concrete enclosure set onto a rubble stone backing, there was no evidence of the plaque. See Drawing No. 24315/13/606 for location.

· Grave 4 is a Qing Grave and consists of a moulded concrete enclosure with grey stone plaque. It was renovated in 1894. See Drawing No. 24315/13/606 for location.

· Grave 5 was renovated in 1966 with no original burial date provided on the plaque. The grave consists of a plain concrete enclosure and platform, it contains no historical structural elements. Location of grave is shown on Drawing No. 24315/13/606.

· Grave 6 is a Qing Dynasty grave with no renovation date given. Moulded concrete enclosure and platform with traces of red paint decoration still visible. See Drawing No. 24315/13/606 for location.

· Grave 7 is another Qing dynasty grave renovated in 1909. It consists of a concrete enclosure with sections covered in whitewash. The grey stone plaque is surrounded by a moulded concrete frame painted red. See Drawing No. 24315/13/606 for location.

· Grave 8 was renovated in 2000. The structure of the grave is modern with moulded concrete enclosure and platform. An historical plaque has been incorporated into the modern structure. Location of grave is shown on Drawing No. 24315/13/606.

· Grave 9: Abandoned gravesite with remnants of a concrete enclosure. The front of the grave has been broken and the remains removed and there was no plaque. See Drawing No. 24315/13/606 for location.

· Grave 10: Abandoned gravesite consisting of empty urns and no structural remains. See Drawing No. 24315/13/606 for location.

· Grave 11: Abandoned gravesite with the only remaining evidence being a cut in the hillside with a few loose bricks and pieces of the enclosure scattered about. See Drawing No. 24315/13/606 for location.

· Grave 12: Abandoned gravesite, grave had been broken and the burial removed. The plaque had been cast aside and the family name had been chipped off it. (Drawing No. 24315/13/606).

· Grave 13: Abandoned gravesite; no burial and again the front section of the grave had been destroyed when the remains were removed. Some sections of the concrete enclosure were intact. There was no sign of the plaque in the vicinity of the grave (Drawing No. 24315/13/606).

· Grave 14 is a Qing Dynasty grave set into a steep hillside on a purposefully terraced platform. The grave consists of a concrete enclosure with a pale grey brick wall structure into which the plaque has been set. The plaque is bordered by a plain moulded concrete frame with traces of red colour (Drawing No. 24315/13/606)

· Grave 15 is a Qing dynasty grave, set on a terrace similar to that of grave 14. The grave consists of a concrete enclosure and platform with a brick wall structure (pale red bricks) with plaque set into it (framed with plain concrete). (Drawing No. 24315/13/606).

· Grave 17: Grave marked on 1:1000 scale map but no evidence remaining on site (Drawing No. 24315/13/606).

· Grave 18: Grave marked on 1:1000 scale map but no evidence remaining on site (Drawing No. 24315/13/606).

· Grave 22: Grave marked on 1:1000 scale map but no evidence remaining on site (Drawing No. 24315/13/606).

· Grave 23: Grave marked on 1:1000 scale map but no evidence remaining on site (Drawing No. 24315/13/606).

· Grave 24: Grave marked on 1:1000 scale map but no evidence remaining on site (Drawing No. 24315/13/606).

· Grave 25 is a Qing Dynasty grave, set on a large terrace with stone lined retaining wall. The grave consists of a concrete enclosure with grey stone plaque set in it. Much of the side sections of the grave had lost their outer covering and consisted of shaped earth and uncut stones (Drawing No. 24315/13/606).

· Grave 26 is a Qing Dynasty grave, set on a gently sloping section of the hillside and does not have a terrace associated with it. The grave consists of a plain concrete enclosure and back wall with reddish orange stone plaque set into it (Drawing No. 24315/13/606).

· Grave 27 is a Qing Dynasty grave set near the edge of the hillslope. The grave consists of some of the concrete enclosure, there was no plaque associated with the grave (Drawing No. 24315/13/606).

· Grave 29: Abandoned gravesite. Only remaining evidence consists of a small pile of stones (Drawing No. 24315/13/606).

· Grave 30: Abandoned gravesite. Only remaining evidence consists of a small pile of stones (Drawing No. 24315/13/606).

Cultural Landscape Features (Boulder Paths)

A boulder path was identified in the 2001 HKIA survey. The condition of the path has not changed since that time. The boulder path, referred to as (BP1) in this report was identified near the northeast boundary of the Finalised Layout Plan. The location is shown in Drawing No. 24315/13/606 and the recording form is shown in Appendix 9.3. The southern section of the path is located at the edge of the Ngong Tong Section of the study area and runs northwards, leading eventually to the valley floor near the former Tong To Shan Tsuen. The path consists of a surface of uncut boulders and cobbles. The path has washed away in sections and some parts are not stone lined. It runs in a generally north-south direction. No other cultural landscape features were identified in this section of the study area.

9.5.3.2 Tong To Shan (North of Shek Tsai Ha Road: east section)

Historical Buildings

No historical buildings were identified in the field survey.

Graves

One intact historical grave was identified in the Tong To Shan. The two graves sites that were identified during the desk-based study G1 was found to have been abandoned with some pieces of the broken concrete enclosure visible. The location of G16 was marked on 1:1000 scale map but no evidence of it was remained on site. A third grave G28 (not identified in the desk-based study) was identified by the grave survey team, it is located in between two large sets of terraced slopes on the hillside overlooking Tong To Shan. A terrace for the grave had been constructed and the burial chamber was cut directly into the hillside at the back of the terrace. The grave is dated to the Late Qing Dynasty. Drawing No. 24315/13/606 shows the locations of Graves 1, 16 and 28.

Cultural Landscape Features (Boulder Paths)

The maps from the HKIA study were consulted, but it was not possible to find all of the mapped paths on site. In light of this situation, all accessible parts of the study area were again walked on a field scan. As part of this field scan, two boulder paths were identified (Drawing No. 24315/13/606). The first path (BP2) was identified in two sections. The southern section is approximately 20 metres in length and runs in a north easterly direction. It has been truncated at its southern end and ends abruptly at an artificial hill slope (cut during the installation of a drainage channel). At the northern end of this section, the path continues on as a dirt surface with a few isolated boulders that may be natural, for approximately 30m (across a flat area between two hilltops). At this point a clearly boulder lined surface is again visible. The path now leads from the flat area down the hillside containing the recorded terraces associated with Tong To Shan. It eventually meets up with another boulder path (BP3). After this junction, BP2 carries on in a north-easterly direction for approximately 10 metres, at this point it crosses a water course (near T7, described below) where a bridge has been constructed out of boulders and cobbles. After this, the path continues on in a north-north easterly direction.

BP3 can be followed for approximately 30m after the junction of itself and BP2. It runs in a generally east/west direction although it veers north/south just before the junction with BP2. The boulder lined surface disappears near the detectable end of the path. This section of the path is located on a steep hillside and there was evidence of water erosion in the form of gullies and many fallen trees. Because of these obstructions, it was impossible to tell if the path continued onwards. It should also be noted that there are also many small earth-lined paths connecting the terraces and running alongside them.

Boulder Terrace (Slope protection walls)

A series of boulder terraces were identified in the vicinity of boulder paths BP2 and BP3 (T1, T2, T3, T4, T5, T6, T7, T8 and T9). The locations of the terraces can be seen on Drawing No. 24315/13/606.

i) T1 consists of a terrace (approximately 5m in width and 20m in length) artificially cut into the hillside with an L-shaped unmortared stone retaining wall, constructed of cobbles and small boulders. The stone wall is generally intact in the vicinity of BP2, however, many sections of the wall have fallen away along the 20m length of the wall. There are evidence of some cut hill slopes around the terrace, but they are very rough and showed no evidence of stone lining.

ii) T2 is located near the highest point of boulder path 2. It consists of sections of a low, uncut and unmortared cobbled wall (c. 0.3m in height) running along the side of the boulder path and on cut sections of hillside perpendicular to the path. The stone lining could be seen to be partially washed away in some sections (with loose stones lying on the ground below the wall) and completely washed away in others with only the cut hillside remaining.

iii) T3 is a very low unmortared stone terrace constructed of unmodified cobbles. It runs perpendicular to BP2 and actually crosses it. It is visible to either side of the path, running for a few metres on either side, before it disappears. This area appears to have suffered from repeated water erosion and it was impossible to tell the original extent of the terrace due to washing away of the hill slope.

iv) T4 consists of another L-shaped terrace on the opposite side of BP2 than T1. This terrace, however, also has low (c. 0.5m high) walls in some sections. The terraces and walls consist of uncut and unmortared cobbles. There is also a ditch lying directly to the side of the boulder path. The ditch is also stone lined and it may have been constructed as a water control device. The boulder path near this feature is currently situated on a pedestal of soil, again showing a history of severe water erosion.

v) T5 is a series of uncut stone terraces, again unmortared, running down the hillslope to the valley floor. The uppermost section of this feature is situated at the junction of BP2 and BP3. Again small sections of the terrace edges have low uncut and unmortared walls. The stone lining is for the most part intact near BP2, however, further away from the path, whilst the hill slope shows clear signs of having been intentionally cut for terracing, it is not stone lined. A surface scan of the terraces did not show evidence of stones that had been washed away and it is possible that the walls were never stone lined.

vi) T6 is another series of terraces running northwards towards the valley floor from BP2, to the northeast of the junction with BP3. These terraces are similar in nature to those of T5. The terraces in this section consisted for the most part of small flat areas with high terrace walls cut into the hillsides.

vii) T7 is the largest of the recorded features. The main section runs parallel to a stream course and consists of an approximately 2 to 3m high terrace wall. It is possible that it represents the lowest section of terraces associated with T4, although due to water erosion and vegetation it was not possible to discern the exact relationship.

viii) T8 and T9 are located in a small valley to the west of the terraces described above. T8 consists of a set of six terraces leading from the lower part of the hillside down to the valley floor. The slopes show clear signs of having been artificially cut and retaining walls of uncut stone had been constructed on some of them. As well, a stone lined ditch, probably associated with water management ran along the south eastern side of the terraces. T9 is a set of three large terraces set further up the hillside from T8. The area between T8 and T9 appears to be natural terrain, though there was evidence of quite substantial water erosion in the area and any modifications to the landscape may have been washed away. The terrace walls of T9 were very high, i.e. over 2 meters. Again there were paths running along side the terraces and associated stone constructed features that were again probably associated with water management.

9.5.3.3 Shek Tsai Ha (South of Shek Tsai Ha Road: western section)

Historical Buildings

No historical buildings were identified in the field survey.

Graves

Three grave sites, G19, G20 and G21, were located during the desk-based study of this section of the study area. During the field survey, two sites were located and there was no evidence found of the third. G19 is a Qing dynasty grave. It consists of a concrete enclosure with the burial removed. The front of the grave had been destroyed during the removal process. The urn has been placed to the side of the grave and the plaque set on top of it. G20 was located in the same area as G19. A cut in the hillside was the only visible evidence of the original gravesite. Upon investigation a plaque was discovered approximately 2 metres away, propped up against the hillside and held up by some loose stones and bricks. Grave 21 was marked on 1:1000 scale map but there was no evidence remaining on site. Locations are shown in Drawing No. 24315/13/606.

Cultural Landscape Features

No cultural landscape features were identified in this section of the study area.

9.5.3.4 Wo Keng Shan (South of Shek Tsai Ha Road: eastern section)

Historical Buildings

No historical buildings were identified in the field survey.

Graves

Two grave sites were identified in this section, both lying in the 50m buffer area to the southwest of the NLES. Grave 30 was marked on 1:1000 scale map but there was no evidence remaining on site. Grave 31 consisted of a concrete enclosure with some traces of decoration visible. Locations of the Graves are shown in Drawing No. 24315/13/606.

Cultural Landscape Features

No cultural landscape features were identified in this section of the study area.

9.6 Identification and Evaluation of Impacts

No historical buildings or structures were identified in the CHIA study area during the field survey. The identified features consisted of graves and cultural landscape features, the impacts are presented in the following sub-sections.

9.6.1 Ngong Tong (North and West of Shek Tsai Ha Road: western and central section)

Graves

All graves located in the Ngong Tong section of the study area will be directly impacted by the Project. Impacts will occur as part of site formation during the construction phase and will result in the destruction of the graves.

Cultural Landscape Features

The southernmost section of boulder path (BP1) is located just within or at the edge of the landfill extension boundary and may be directly impacted by the Project. Impacts will occur as part of site formation during the construction phase and will result in the destruction of any sections of the path that fall within the landfill extension boundary.

9.6.2 Tong To Shan (North of Shek Tsai Ha Road: east section)

Graves

No intact graves are located within the Project area. Grave (G28) is located approximately 40m from the boundary of the landfill extension area and will not be impacted by the Project.

Cultural Landscape Features

A small section of BP2 is located in the extension boundary area and will be directly impacted by the Project. Impacts will occur as part of site formation during the construction phase and will result in the destruction of any sections of the path that fall within the landfill extension area.

The remainder of BP2 is located outside of the extension area and will not be impacted by the Project.

The boulder terrace features are all located outside of the extension area at the following distances:

· T1: approx. 40m

· T2: approx. 20m

· T3: approx. 50m

· T4: approx. 60m

· T5: approx. 70m

· T6: approx. 85m

· T7: approx. 80m

· T8: approx. 60m

· T9: approx. 40m

The terrace features will not be impacted by the Project.

9.6.3 Shek Tsai Ha (South of Shek Tsai Ha Road: western section)

Graves

Two gravesites were located in this section of the study area and will be directly impacted by the Project. Impacts will occur as part of site formation during the construction phase and will result in the destruction of the graves.

9.6.4 Wo Keng Shan (South of Shek Tsai Ha Road: eastern section)

Graves

Grave 31 is located at a distance of approximately 20 metres from the nearest works area and will not be impacted by the construction or operation of the landfill extension.

9.7 Mitigation Recommendations

As mentioned above the impacts arising from this Project will result in the destruction of any resources located within the extension boundary. The mitigation recommendation for all of the impacted resources is preservation by detailed record. The full methodology for the recording and preparation of the archives for both the cultural landscape features (boulder paths and boulder terraces) and the graves can be found in Appendix 9.4. It should be noted that sites of abandoned graves would require no mitigation measures. It should also be noted that the study area for the Project was extremely overgrown with dense ground covering vegetation and that the potential for the presence of more historical graves in the study area exists. As a result of this situation it is recommended as mitigation that during the construction phase, if during the course of works a grave is found that the AMO is contacted immediately and that works stop in the immediate vicinity of the grave until it can be inspected by AMO staff.

The identified resources that will require mitigation are listed by section below:

9.7.1 Ngong Tong (North and West of Shek Tsai Ha Road: western and central section)

Cultural Landscape Features

The mitigation proposal for cultural landscape in Ngong Tong is summarised in Table 9.3.

Table 9.3: Mitigation recommendations for cultural landscape features in the Ngong Tong section of the study area

Resource

Impact Assessment

Mitigation Recommendation

Boulder Path (BP1)

Any sections of the boulder path that fall within the boundary extension for the finalised layout plan will be directly impacted by the Project.

The southern section of the path must be surveyed and mapped in order to determine if any sections of the path fall within the Project boundary.

If any sections are found to be within the Project boundary then preservation by record must be undertaken and fulfill the requirements as stated in Appendix 9.4.

Graves

The mitigation proposal for graves in Ngong Tong section is summarised in Table 9.4.

Table 9.4: Mitigation recommendations for graves in the Ngong Tong section of the study area

Resource	Impact	Mitigation
G2, G4, G5, G6, G7, G8, G14, G15, G25, G26 and G27.	All graves will be directly impacted by the Project.	Preservation by record must be undertaken for all graves and fulfill the requirements as stated in Appendix 9.4.

9.7.2 Tong To Shan (North of Shek Tsai Ha Road: east section)

Cultural Landscape Features

The mitigation proposal for Tong To Shan is summarised in Table 9.5.

Table 9.5: Mitigation recommendations for cultural landscape features in the Tong To Shan section of the study area

Resource	Impact	Mitigation
Boulder Path (BP2)	The section of the boulder path that falls within the Project boundary will be directly impacted by the Project.	Preservation by record must be undertaken for the section of the path that will be directly impacted by the Project and it must fulfill the requirements as stated in Appendix 9.4

Graves

No intact graves will be impacted by the Project; no mitigation is required.

9.7.3 Shek Tsai Ha (South of Shek Tsai Ha Road: western section)

Cultural Landscape Features

No cultural landscape features were identified in this section of the study area and no mitigation is required.

Graves

The mitigation proposal for Shek Tsai Ha Section is summarised in Table 9.6.

Table 9.6: Mitigation recommendations for graves in the Shek Tsai Ha section of the study area

Resource	Impact	Mitigation
G19	Both graves will be directly impacted by the Project.	Urn is present but the structure has been severely damaged; no mitigation will be required.
G20	Both graves will be directly impacted by the Project.	Only remaining structural feature of the grave is the plaque. No mitigation is required.

9.7.4 Wo Keng Shan (South of Shek Tsai Ha Road: eastern section)

Cultural Landscape Features and Graves

No resources recorded in this section of the study area will require mitigation.

9.8 Conclusions

9.8.1 Archaeology

As a result of the findings of the desk-based study and the preliminary site investigation, the Ngong Tong, Shek Tsai Ha and Wo Keng Shan sections of the study area were deemed to have extremely low archaeological potential and would require no mitigation measures. Further testing of the Tong To Shan section was recommended to determine if any sub-surface deposits were associated with the cultural landscape features identified there. The result of the archaeological investigation was that no archaeological material or cultural layers were identified. Thus, no further mitigation measures in the form of archaeological excavation are recommended.

The construction activities associated with the site formation for the NENT Landfill Extension will not impact on any areas containing archaeological potential. Archaeological resources identified as part of the Tong To Shan Archaeological Site in previous investigations are located outside of the extension boundary and will not be impacted by the construction works.

9.8.2 Built Heritage

A number of resources will be directly impacted by the Project; these consist of 13 graves (G2, G4, G5, G6, G7, G8, G14, G15, G25, G26, G27, G28 and G31) and 2 sections of boulder paths (BP1 & BP2). The section of boulder path (BP1) will have to be further surveyed to determine its exact relationship to the extension area and hence the nature of any impacts.

The impacts on the Cultural Landscape Features associated with the Tong To Shan Archaeological Site will be minimal as the agricultural terraces and associated features, including the main sections of the boulder paths are all beyond the extension boundary.

Mitigation in the form of detailed preservation by record for all of the resources will be required prior to the commencement of the construction phase. The survey of boulder path and the submission to AMO will be specified in the NENT Landfill Extension Contract. It is the responsibility of the DBO Contractor to ensure that the recording will be carried out by a qualified professional and that a report will be submitted to and approved by AMO prior to the commencement of any excavation works.

With the implementation of mitigation measures, there will be no impacts to cultural heritage resources during construction, operation, restoration and aftercare stages of the NENT Landfill Extension.

9.9 References

Fyfe J. A. et al (2000) The Quaternary Geology of Hong Kong, Hong Kong Geological Survey, Geotechnical Engineering Office, CED, The Government of the Hong Kong SAR.

Hong Kong Institute of Archaeology (2002) The 2001 Archaeological Survey & Assessment for the Proposed NENT Landfill Extension (Final report).

Hong Kong Geological Survey (1991) Sheung Shui; Sheet 3; Solid and Superficial Geology

Series HGM20, Scale 1 : 20 000. Hong Kong Government.

Aerial Photograph Library (GEO) (1999) A49224 (Ta Kwu Ling)

(1999) CN23769 (Ta Kwu Ling)

(2004) CW57996 (Ta Kwu Ling)

10 Ecological Impact

10.1 Introduction

This chapter presents the Ecological Impact Assessment on any direct and indirect potential ecological impacts arising from the construction, operation, restoration and aftercare of the Project. Potential losses, damages, and impacts to flora, fauna and natural habitats, including the aquatic fauna in Lin Ma Hang stream have been mitigated by means of protection, maintenance and rehabilitation of the natural environment. The potential ecological impact on the identified species and habitats was assessed to be minimal and acceptable with the implementation of mitigation measures such as woodland plantation and transplantation of species of conservation value.

The ecological impact assessment has been conducted in accordance with the requirements of Annexes 8 and 16 of the TM-EIAO and the EIA Study Brief for the Project.

10.2 Relevant Legislation and Guidelines

The HKSAR ordinances and regulations relevant to ecological assessment of this Project include the following:

· Forests and Countryside Ordinance (Cap. 96) and its subsidiary legislation, the Forestry Regulations;

· Town Planning Ordinance (Cap. 131);

· Wild Animals Protection Ordinance (Cap. 170);

· Country Parks Ordinance (Cap. 208) and its subsidiary legislation; and

· Environmental Impact Assessment Ordinance ("the EIAO", Cap. 499) and the associated TM (TM-EIAO).

Ecological assessment will also make reference to the following guidelines and standards as well as international conventions:

· Hong Kong Planning Standards and Guidelines (HKPSG) Chapter 10, "Conservation";

· Ecological Baseline Survey For Ecological Assessment (EIAO Guidance Note No. 7/2002);

· PELB Technical Circular 1/97 / Works Branch Technical Circular 4/97, "Guidelines for Implementing the Policy on Off-site Ecological Mitigation Measures";

· Relevant wildlife protection laws in PRC;

· Convention on Wetlands of International Importance Especially as Waterfowl Habitat (the "Ramsar Convention"), which requires parties to conserve and make wise use of wetland areas, particularly those supporting waterfowl populations;

· United Nations Convention on Biological Diversity, which requires parties to regulate or manage biological resources important for the conservation of biological diversity, to promote the protection of ecosystems, natural habitats and the maintenance of viable populations of species in natural surroundings;

· International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species;

10.3 Field Survey Scope and Methodology

The study area for terrestrial ecological assessment covers all areas within 500 metres of the site boundary of the land based works areas (Project Area), or the area likely to be impacted by the Project. Based on the results of literature review, most of the previous studies covered areas beyond the 500m boundary for the current study, or have been focused on the existing landfill area. Locations of sites and species of conservation importance previously recorded are also outside the current study area. In order to fill this data gap, the field surveys have been focused on the study area (i.e. the Project Area and the area within the 500m of the site boundary (500m-Area)).

The EIA study brief required ecological field surveys of at least 6 months covering wet season to be carried out. An eight-month ecological field survey (covering dry and wet season) was undertaken from March to October 2005 to record ecological data within the study area and establish the ecological profile, for incorporation into the EIA. The ecological survey was completed in October 2005. The flora, fauna and other components of the ecological habitats within the assessment area were examined. In addition to daytime surveys, night time surveys were conducted to record nocturnal fauna including birds, herpetofauna and mammals. Known areas of conservation importance (Lin Ma Hang Stream, Lin Ma Hang Lead Mine SSSI) lie mostly outside the 500m boundary and were covered mainly by literature review, and supplemented by verification surveys. Data analyses and discussions described habitats and species found in the study area, highlighting those that are rare, of conservation importance, or protected by law. Sampling locations of fauna group were included in Drawing No. 24315/13/701. Species groups surveyed and the survey methods are described below.

Habitat and Vegetation

Habitats were mapped (as shown in Drawing No. 24315/13/702) based on the latest government aerial photos and field ground truthing. Representative areas of each habitat type were surveyed on foot. Plant species of each habitat type encountered and their relative abundance, with special attention to rare or protected species, were recorded. Colour photographs of all habitats encountered on site and of ecological features of special importance were provided in Drawing No. 24315/13/703. Habitat maps of the study area were produced at the required scale using GIS software.

Avifauna

The birds of selected habitats within the study area were mainly surveyed using the transect count method. Birds within 20 m from the centreline of sampling transects were identified and counted. For birds in habitats occurring as small patches (e.g., woodland, plantation) the point count method was used. Ten minutes were spent counting birds seen or heard within 30 m from the centre of each sampling point. Since some bird species are nocturnal, e.g., owls, nightjars, night surveys were carried out. Bird species encountered outside sampling transects and points but within the study area were also recorded to produce a complete species list. Signs of breeding were recorded. Relative abundance and species richness of birds were computed.

Herpetofauna

Herpetofauna in the study area were surveyed qualitatively. Both daytime and night time surveys were carried out for herpetofauna. Potential microhabitats of herpetofauna, e.g., litters, rotten logs, were searched. All reptiles and amphibians sighted were recorded. Amphibians were identified by their calls during night surveys.

Non-Volant Mammals

Mammals in both the study area were surveyed qualitatively. All sightings, tracks, and signs (e.g., scats, footprints, quills) of mammals were recorded, and identified to species as far as possible. Both daytime and night time surveys were carried out.

Bats

Within the study area, bats were surveyed by observations of roosting, flying, or foraging at six point-count stations set at representative habitats (woodlands and riparian zone) during dusk. Abundance data were recorded using two methods. First, bat vocalizations (bat calls) were recorded as files on computer disks using an AnaBat® II Bat Detector (a “detector”) linked to an AnaBat zero crossings analysis interface module (ZCAIM) equipped with a compact flash card for data storage. Field data were downloaded from the flash card to a computer for analyses in the office. Second, bats were manually counted whenever the detector indicated bats within its range of sensitivity. The manual counts enable more accurate counting in situations where multiple bats were detected by the detector but the recorded sequence file could not distinguish between them. Species were identified visually. Abundance was indexed as the adjusted number of bat calls or sightings during a 7-minute sampling period at each of 6 sampling points. Adjustments consisted of reconciling the computer record with the manual record, to account for data files that represent more than one bat or multiple calls that represent only one bat. All computer data analyses were carried out using Statistix 7.0® software.

Dragonflies and Butterflies

Dragonflies and butterflies within the study area were surveyed using the transect count or point count method. Dragonflies and butterflies within 10 m from the centreline of sampling transects were identified and counted. When point count method was used, five minutes were spent counting dragonflies and butterflies within 15 m from the centre of each sampling point. Dragonflies and butterflies outside the transects and counting points but within the study area were also recorded in order to produce a complete species list.

Aquatic fauna

Aquatic fauna in channels and stream courses within the study area (e.g. upper tributaries of Lin Ma Hang Stream and Ping Yuen River) were studied. Lin Ma Hang Stream located outside the 500 m boundary area was also visited to verify the information reported in the literature. Sampling methods (including direct observation, focused searching, hand netting) were selected according to the site conditions. Boulders in the stream were overturned to locate aquatic animals beneath if necessary. All encountered organisms were identified to the lowest possible taxon and recorded. Abundance and species richness of aquatic fauna were provided.

10.4 Key Ecological Issues

Key ecological issues identified during the course of the EIA study include the following.

· Ecologically sensitive areas (Drawing No. 24315/13/701):

o Lin Ma Hang Stream and its catchment;

o Lin Ma Hang Lead Mines Site of Special Scientific Interest (SSSI);

o Wo Keng Shan fung shui wood;

o Robin’s Nest Countryside.

· Habitats of conservation interests:

o woodlands

o natural stream courses and rivers (e.g. Lin Ma Hang Stream)

· Wildlife groups of conservation interests:

o vertebrates (e.g. avifauna, mammals including bats, fish, herpetofauna)

o macroinvertebrates (e.g. butterflies, odonates, crustaceans)

Also, during the public communication meetings some of the Green Groups expressed the importance to preserve the existing trail from Wo Keng Shan Road (near Miu Keng) to Robin’s Nest. As explained during these meetings, the proposed landfill extension will not encroach upon this existing trail, nor the main portion of Robin’s Nest countryside.

10.5 Results of Literature Review

In accordance with the Study Brief, the ecological baseline shall include the following:

· review and incorporate the findings of relevant studies

· carry out necessary field surveys, the duration of which shall be at least 6 months (covering wet season), and investigation to verify the information collected, fill the information gaps identified and fulfil the objectives of the EIA study

· establish an ecological profile of the study area based on data of relevant previous studies/surveys and results of additional ecological field surveys, and describe the characteristics of each habitat found

The relevant studies include but are not limited to those listed in Section 3.4.8.4 of the EIA Study Brief. These are:

· The on-going EIA study of the Drainage Improvement in Northern New Territories – Package C

· Conservation Recommendations for Fish Communities of Lowland Streams in Hong Kong prepared by Dr. Chan Pui Lok, Bosco and Prof. David Dudgeon.

· Sustainability and biodiversity: the impact, alternative design and prospects of restoration of channelized lowland streams in Hong Kong. (Chan Pui Lok Bosco 2001. Ph. D. Thesis).

· Sustainable Development for the 21st Century (SUSDEV)

· Annual Summary Reports of Terrestrial Monitoring for NENT Landfill Site

· The Pilot Biodiversity Study of the eastern Frontier Closed Area and North East New Territories, Hong Kong, June-December 2003 conducted by Kadoorie Farm and Botanic Garden (KFBG) (2004).

· Final Strategic Environmental Assessment Report on Extension of Existing Landfills and Identification of Potential New Waste Disposal Sites

· Register of Sites of Special Scientific Interest (SSSIs). Loose-leaf document maintained by Planning Department, Hong Kong.

· The Terrestrial Biodiversity Survey conducted by HKU

· Annual report and other publications of The Hong Kong Bird Watching Society

· Memoirs of Hong Kong Natural History Society

· Porcupine! – Newsletter of Department of Ecology & Biodiversity of University of Hong Kong

· Hong Kong Biodiversity - Newsletter of the Department of Agriculture, Fisheries and Conservation

Despite the distance of Lin Ma Hang stream from the study area (mostly beyond the 500m-Area), the study brief requires the potential impacts to the stream and its catchment to be assessed. Lin Ma Hang Stream is a typical lowland freshwater stream and has a rich collection of primary freshwater fish including five rare and uncommon species (Final Strategic Environmental Assessment Report on Extension of Existing Landfills). 15 species of freshwater fish were recorded during a study covering 43 lowland streams in Hong Kong (Chan 2001). The University of Hong Kong has submitted a proposal to the Government in 1999 recommending the designation of Lin Ma Hang stream as an SSSI.

The EIA study brief for the Project highlighted the on-going EIA Study of the Drainage Improvement in Northern New Territories – Package C, which was conducted in 2003-4 and included a 12-month ecology survey. The brief requires incorporation of these survey results into the baseline for the present EIA study.

Kadoorie Farm and Botanic Garden (2004) conducted a biodiversity study on Ling Ma Hang Stream in 2003. During the study, 16 freshwater fish were recorded in the stream, including 2 extremely rare ones (Appendix 10.1). The high species diversity and the healthy and intact fish community confirmed the importance of this stream, and KFBG urged designation of this stream as an SSSI (ibid.).

Lin Ma Hang Lead Mines SSSI supports nine bat species (Appendix 10.2) (Shek and Chan 2004) and is one of the most important bat colonies in Hong Kong. The roosting population is 1146 and 898 bats in summer and winter respectively (Shek and Chan 2005). Greater Bent-winged Bat is the most numerous species (81.7% of total bats in summer, 73.3% in winter). All recorded bat species prey on insects that are caught on the wing or are gleaned from vegetation, soil or water. This SSSI is located almost 1 km from the proposed Landfill Extension site. It is unlikely that this SSSI and the nearby riparian foraging areas for the bats would be directly affected by the Project. However, indirect impacts to the bat colonies will be assessed in detail in this study and will include construction noise and potential loss of foraging habitat.

Lin Ma Hang area is well known for its botanical interest. Seven plant species of conservation interest have been recorded at Lin Ma Hang (KFBG 2004, Xing et al. 2000). The important wooded ravines and Fung Shui Wood identified so far are located outside the proposed boundary of the Landfill Extension and even beyond the 500 m boundary for the Project. Four rare and one very rare plant species were also recorded in Robin’s Nest by the Biodiversity Survey (HKU 2002), but these plants were located at least 2 km away from the proposed landfill extension site. Therefore they are unlikely to be adversely impacted.

Terrestrial fauna in Lin Ma Hang were surveyed between October 2003 and September 2004 during the EIA study of Drainage Improvement in Northern New Territories – Package C. Uncommon/rare fauna species that would utilise stream and wetland habitats included two species of dragonfly (Club-tailed Cruiser Macromia urania and Blue Sprite Pseudagrion microcephalum) and four species of butterfly (Glassy Bluebottle Graphium cloanthus, Small Grass Yellow Eurema brigitta, Centaur Oak Blue Arhopala pseudocentaurus and Bush Hopper Ampittia dioscorides) (ibid.).

Some bird species were reported in Robin’s Nest by members of The Hong Kong Bird Watching Society between 1996 and 2000. These included Peregrine Falcon Falco peregrinus, Collared Scops Owl Otus bakkamoena, Oriental Scops Owl O. sunia and Savanna Nightjar Caprimulgus affinis (Carey et al. 1998, 1999, Turnbull et al. 2004). Oriental Scops Owl is a scarce migrant in Hong Kong (Carey et al. 2001) and is found in areas with scattered trees (Viney et al. 2005). Peregrine Falcon is a rare resident, and occurs in a wide range of habitats. Collared Scops Owl is common and widespread in Hong Kong, and mainly occurs in wooded habitats. Savanna Nightjar is an uncommon resident, and is mainly found in hillsides with low vegetation (Carey et al. 2001).

The environmental impact assessment and monitoring for the existing landfill described the habitats in the area. Habitats surrounding the existing landfill, other than plantation, are mainly grassland and shrubland. Hillfire disturbance was quite frequent at the site. Species commonly recorded included Dicranopteris pedata, Arundinella setosa, Ischaemum spp., Cymbopogon spp., and Panicum sp. Woody species included Baeckea frutescens, Rhodomyrtus tomentosa, Pinus spp., Liquidambar formosana, and the planted Acacia mangium and Acacia confusa, Lophostemon confertus and Casuarina equisetifolia (ibid.). Protected species recorded/observed included orchid species such as Habenaria linguella (FELT 1999) and Arundina chinensis (Cheung, per comm.). The annual monitoring results showed that the vegetation varied seasonally was of good condition and vegetation cover was high, although some next to the landfill operation site was covered by dust. One exception was Pinus massoniana, which was either killed by nematode infection or hillfires. It was concluded that the landfill operation did not cause any adverse impacts on natural establishment of vegetation.

10.6 Results of Field Surveys

10.6.1 Habitat and vegetation

Major habitats recorded within the study area include natural woodland, plantation, grassland with low shrub, stream, abandoned agricultural fields, and urbanised/disturbed (Drawing No. 24315/13/702 & 703, Table 10.1).

Table 10.1: Habitats recorded within the study area

Habitat	Area (ha)
Natural Woodland	74.18
Plantation Woodland	7.86
Grassland with Low Shrub	155.25
Abandoned Agriculture	12.99
Urbanised/Disturbed	49.84
Stream	2900 m (stream channels inside Project Area) 314 m (channels inside 500m-Area) 250 m (Ping Yuen River inside 500m- Area) 1343 m (Lin Ma Hang Stream inside 500m- Area) 3180 m (Lin Ma Hang Stream outside study area)

In total, 203 plant species were recorded (Appendix 10.3). Seven plant species including 2 trees, 2 shrub, 2 orchid and 1 fern species of conservation interest were recorded within the study area. They were Aquilaria sinensis, Endospermum chinense, Rhododendron simsii, Pavetta hongkongensis, Cibotium barometz, Arundina graminifolia and Spathoglottis pubescens.

The tree survey recorded 29 tree species, mostly native. A total of 2,178 trees with diameter at breath height (DBH)>95mm were recorded, 825 of which within the Project area, and 85% of which had a DBH equals to 0.3m or below and the remaining 327 nos. (15%) had a DBH in the range of 0.4m to 0.8m inclusive. The majority of the trees surveyed are young at age and small at size. Trees were mainly recorded in the secondary woodland at northern fringe and a ravine at the centre of the proposed landfill extension.

Natural Woodland

Natural Secondary Woodland was mainly located on the hillside of Lin Ma Hang catchment outside the Project area and along major ravines within the Project area. Woodland at Tong To Shan was more mature with a canopy of 12-15m, while woodland within the rest of study area including those within the proposed landfill extension area (Project Area) was relatively younger with a canopy of 5-8m. It was dominated by native pioneer tree species including Schima superba, Machilus chekiangensis, Schefflera heptaphylla, Cratoxylum cochinchinensis, Aporosa dioica, Itea chinensis, and Castanopsis fissa. The understory was fairly dense and was composed of a variety of tree, shrub, fern and herb species including Litsea rotundifolia, Psychotria rubra, Cibotium barometz, and Christella parasitica.

A total of 117 plant species were recorded in woodland habitat, including two tree species and two shrub species and one fern species of conservation concern. One mature tree of Endospermum chinense was recorded in a ravine. It is a tree of restricted distribution in Hong Kong. It is not protected locally or regionally. One mature tree and three seedlings of Aquilaria sinensis were seen. It is listed on CITES Appendix II and scheduled under the Protection of Endangered Species of Animals and Plant Ordinance (Cap. 586). It is protected as Category II nationally protected species in China and is listed as vulnerable in the China Plant Red Data Book and IUCN Red List, but it is quite common in Hong Kong. Two individuals of Rhododendron simsii were recorded in the ravines. This is a native shrub commonly found in Hong Kong. The whole genus Rhododendron is protected under Forestry Regulations. An individual of Pavetta hongkongensis was recorded at Tong To Shan. It is protected under Forestry Regulations but is quite common in Hong Kong. All of these species except Pavetta hongkongensis were located within the Project Area. Cibotium barometz is a fern as listed on CITES Appendix II and scheduled under the Protection of Endangered Species of Animals and Plant Ordinance (Cap. 586). A few individuals were observed outside the Project Area, and it is commonly recorded in forest and shrubland in Hong Kong.

A fung shui wood was recorded at Wo Keng Shan at the southwest fringe of the study area. It was dominated by Cinnamomum camphora, which apparently were planted due to their uniform size and spacing. Other trees recorded include Dimocarpus longan, Ficus microcarpa, and Macaranga tanarius. The plant diversity was low; a total of 15 species was recorded and little understorey was developed.

Plantation Woodland

Plantation was mainly recorded on the engineering slope along the existing access road inside the landfill and the stockpile area. It was young, about 20 years old, with an 8-12m canopy dominated by exotic species including Acacia confusa, Acacia auriculiformis, Acacia mangium, Eucalyptus robusta, Casuarina equisetifolia, Lophostemon conferta and Leucaena leucocephala. The understorey was mostly grassy occasionally with native shrubs and trees including Neyraudia reynaudiana, Bidens pilosa, Celtis tetrandra subsp. sinensis, Macaranga tanarius, and Breynia fruticosa. The plant diversity was low - a total of 43 species with no plant species of conservation concern was recorded in this habitat.

Grassland with Low Shrub

Grassland with low shrub, probably maintained by hillfires from scattered grave sites, occupied about half of the study area dominating the natural hillside and hydroseeded slope. Major species recorded included Dicranopteris pedata, Neyraudia reynaudiana, Rhodomyrtus tomentosa, Baeckea frutescens, and Rhus chinensis.

A total of 114 plant species was recorded within the grassland with low shrub habitat, including 2 orchid species of conservation concern. About 10 individuals of Arundina graminifolia were found on the engineered slope along the access road to the stockpile area, while about 50 individuals of Spathoglottis pubescens were located along the access road to Robin’s Nest. While all orchids are protected under the Forestry Regulations, both orchids recorded during the present survey are very common in Hong Kong.

Abandoned Agricultural Field

Abandoned agricultural field was recorded at Wo Keng Shan and Lin Ma Hang on the southwest and northeast fringe of the study area. It was mainly composed of weedy and grassy species including Neyraudia reynaudiana, Panicum maximum and Wedelia trilobata. A total of 16 species was recorded. No plant species of conservation concern was found.

Urbanised/Disturbed

The existing landfill site, including the entrance, access road, landfill area, and stockpile area constituted this habitat. Most of the surface was concrete or void of vegetation. This area has little ecological value.

Streams/Channels

There were channels within the Project Area. The channels included man-made concrete drains and semi-natural channels which were remnants of previous stream courses disturbed during the construction of the existing landfill. Concrete drains were constructed along the boundary of the stockpile area of the existing landfill site. The drains on both sides of the stockpiles then joined a remnant stream course. The remnant stream course ran along the access road and changed into concrete channel near the boundary of the Project Area. The concrete channel went through a small portion of the study area and finally joined the existing stream courses (Ping Yuen River, see below).

Besides the length of concrete channel originating in the landfill site, there were two major streams within the study area, i.e. Ping Yuen River southwest of the Project Area and Lin Ma Hang northeast of the Project Area. But both streams were completely outside the Project Area.

Ping Yuen River originated on the northwest slope of Wo Keng Shan (to the south of the landfill), and then ran westward, through Ta Kwu Ling area, and finally joined Shenzhen River at HKSAR border near Lo Shue Ling.

Lin Ma Hang originated from several tributaries on the northwest slope of Robin’s Nest (Hung Fa Leng). Only one of the Lin Ma Hang tributaries (the most southward) fell within the study area boundary. These tributaries all flowed in a northwest direction and joined near Lin Ma Hang Village. The stream finally joined Shenzhen River to the north of the village.

10.6.2 Avifauna

Project Area

A total of 16 species was recorded within the Project area during quantitative surveys. The recorded bird community is typical of disturbed areas (e.g., White Wagtail Motacilla alba) (Appendix 10.4). Collared Scops Owl Otus lempiji was recorded during night surveys. Species richness was low in all habitats within the Project area (Table 10.2). Apart from woodland, bird abundance was low in all habitats. Bird density in woodland was considered medium to high. Apart from an abandoned nest (probably nest of Spotted Dove Streptopelia chinensis) in the plantation in the stockpile, there was no sign of breeding within the Project area.

Table 10.2: Bird community of habitats within Project area

Habitat	Urbanised/disturbed	Grassland with low shrub	Plantation	Woodland
Bird density (birds ha^-1)	4.8	1.8	9.8	27.3
Species richness	5	4	5	5

Grassland with low shrub is the major habitat within the Project area. This type of habitat generally supports low abundance and species richness of birds (Thrower 1984, Dudgeon and Corlett 1994, 2004, Kwok and Dahmer 2002). This may be related to the low food abundance, low concealment and simple habitat complexity (Dudgeon and Corlett 1994).

Woodland and plantation mainly exist as small patches or narrow strips within the Project area. Only the woodland on the southeast corner of the Project area is connected to continuous woodland. The bird species in woodland and plantation within the Project area are those favour open areas, and are basically similar to those in the surrounding grassland with low shrub. No woodland dependent bird species was recorded in woodlands within the Project area. Plantations within the Project area consist mainly of exotic species, which do not bear fruits and have sparse canopies. Hence these plantations are not important foraging and breeding habitats of birds. These plantations are considered of low ecological importance as feeding and nesting habitats for birds.

Bird species of conservation concern within the Project area included Collared Scops Owl and Greater Coucal Centropus sinensis. Both are Class 2 Protected Animal of PRC and Collared Scops Owl is listed in Appendix 2 of CITES (Zheng and Wang 1998). Collared Scops Owl and Greater Coucal are common and widespread in Hong Kong (Carey et al. 2001). Collared Scops Owl was recorded in roadside plantation near the entry of the NENT Landfill. This species can be found in wooded areas, including plantations and feed mainly on insects and small mammals (e.g., mice, shrews), and is recorded from widespread areas (ibid.). Greater Coucal was recorded in grassland in Ngong Tong. This species can be found in many types of habitats. Greater Coucal has also been observed foraging in refuse (ibid.).

500m-Area

In total, 44 bird species were recorded in the 500m-Area, and were mainly common and widespread in Hong Kong (Appendix 10.5). Significant observations were the recording of woodland dependent species (Emerald Dove Chalcophaps indica, Grey-chinned Minivet Pericrocotus solaris and Chestnut Bulbul Hemixos castanonotus) in woodland on south of Tong To Shan Tsuen. These species are mainly found in large old woodlands in Hong Kong (Carey et al. 2001).

Bird species of conservation concern within the 500m-Area included Black Kite Milvus lineatus, Emerald Dove, Greater Coucal and Collared Scops Owl. Black Kite and Collared Scops Owl are Class 2 Protected Animal of PRC and listed in Appendix 2 of CITES (Zheng and Wang 1998). Greater Coucal is Class 2 Protected Animal of PRC. Black Kite and Greater Coucal are common and widespread in Hong Kong, and can be found in many types of habitats (Carey et al. 2001). Emerald Dove is rare in Hong Kong, and mainly found in well-wooded area (ibid.). Collared Scops Owl can be found in many types of wooded areas, including plantations (ibid.).

Black Kites were recorded at the existing landfill. Emerald Dove was observed in woodland south of Tong To Shan Tsuen. Collared Scops Owl was recorded in roadside plantation near the entry of the NENT Landfill. Greater Coucals were found in abandoned agriculture in Lin Ma Hang and Wo Keng Shan.

10.6.3 Herpetofauna

Project Area

Only one species of amphibian was recorded within the Project area. This was the Brown Tree Frog Polypedates megacephalus. Both eggs and adults were recorded. This species is common in Hong Kong (Chan et al. 2005).

Three species of reptiles were recorded within the Project area. These were the Changeable Lizard Calotes versicolor, Long-tailed Skink Mabuya longicaudata and Taiwan Kukri Snake Oligodon formosanus. Changeable Lizard and Long-tailed Skink are common and widespread in Hong Kong (Karsen et al. 1986). Taiwan Kukri Snake is not common but widespread in Hong Kong. This species inhabits a wide range of habitats, including dry and wet ones (ibid.). These include grassland, shrubland, woodland and wet cultivation. Taiwan Kukri Snake was found in plantation near the stockpile.

500m-Area

Five species of amphibian were recorded within the 500m-Area. These were Asian Common Toad Bufo melanostictus, Brown Tree Frog, Gunther’s Frog Rana guentheri, Paddy Frog Fejervarya limnocharis and Chinese Bullfrog Hoplobatrachus chinensis. All are common in Hong Kong (Chan et al. 2005).

Chinese Bullfrog is of conservation concern. This species is a Class 2 Protected Animal of PRC (Zhao 1998). Chinese Bullfrog was recorded in Lin Ma Hang Stream.

Four species of reptile were recorded within the 500m-Area. These were Red-eared Slider Trachemys scripta, Changeable Lizard, Chinese Skink Eumeces chinensis and Long-tailed Skink. All are common in Hong Kong. Red-eared Slider is an exotic species (Karsen et al. 1986).

10.6.4 Non-Volant Mammals

Project Area

A probable den of Wild Boar Sus scrofa was recorded in area immediate outside the existing landfill. Wild Boar is recorded in grassy-shrubland and forest in widespread localities in Hong Kong. This was the only sign of non-volant mammal in the Project area.

500m-Area

No other non-volant mammals were recorded within the 500m-Area.

10.6.5 Bats

Project Area

Three species, namely, Japanese Pipistrelle Pipistrellus abramus, Himalayan Roundleaf Bat Hipposideros armiger, and Leschenault’s Rousette Rousettus leschenaultii were recorded in the Project area. Japanese Pipistrelle was the most numerous species. All are widespread and common in Hong Kong (Shek and Chan 2005, 2006) and common in Mainland China (Zhang 1997). Total numbers of calls-sightings were similar in March and October 2005 (Table 10.3). In both months the total was approximately one fourth of the August total of 144. This probably reflects the seasonal differences in nocturnal insect activity, which causes seasonal changes in bat activity. In colder months bat numbers are typically lower than in the warmer months.

Table 10.3 : Bat calls and sightings recorded by species at NENT Landfill in 2005

Date	Site No.	Start Time	End Time	No.	Pipabr	Hiparm	Roules
19-Mar-05	6	1855	1902	0
	1	1912	1919	5	5
	2	1923	1930	7	7
	3	1935	1942	9	9
	4	1945	1952	8	6	2
	5	2000	2007	11	10	1
Survey totals				40	37	3	0
24-Aug-05	6	1830	1837	0
	1	1845	1852	1		1
	2	1855	1902	55	35		20
	3	1907	1914	21	21
	4	1915	1922	28	27		1
	5	1926	1933	39	33	4	2
Survey totals				144	116	5	23
12-Oct-05	6	1840	1847	2	2
	1	1853	1900	2	2
	2	1904	1911	5	5
	3	1913	1920	23	14	9
	4	1924	1931	3	3
	5	1933	1940	1	1
Survey totals				36	27	9	0

* Pipabr = Japanese Pipistrelle Pipistrellus abramus: Hiparm = Himalayan Roundleaf Bat Hipposideros armiger; and Roules = Leschenault’s Rousette Rousettus leschenaultii

In two of the three survey periods, sampling Station 3 had the greatest number of bats. Station 3 is a valley location with a perennial stream (the remnant stream course within the Project Area) to the west and a wooded hillside to the east. This site has produced the only records of insectivorous bats, which were abundant in August, but not so in March or October.

Japanese Pipistrelle and Himalayan Roundleaf Bat are insectivorous, while Leschenault’s Rousette is frugivorous. Most of the Hong Kong bats use mines and water tunnels as roost sites, as natural roosts such as inland cave or mature forests are lacking (Ades 1994). Water tunnel, mine or big tree is absent within the proposed extension site. Therefore, bats are thought to forage on the proposed extension site but roost elsewhere, probably in nearby woodlands or in the abandoned lead mine at Lin Ma Hang.

Foraging habitats preferred by bats in Hong Kong included 1) riparian vegetation on stream bank and open water bodies (reservoirs, fishponds); 2) woodland edge (boundary with grassland shrub and abandoned agricultural lands); and 3) agricultural lands (Ades and Reels 1998).

The major vegetation cover within the Project area is grassland with low shrub, which probably supports low insect abundance. Water in the remnant stream course near Station 3 is contaminated and may not provide suitable habitat for nocturnal flying insects, mainly mosquito, which in turn are food base of insectivorous bats. The interface of grassland with low shrub and natural woodland along the ridge of Wong Mau Hang Shan may provide foraging habitat to bats. Bats can fly more easily above the open space above short vegetation cover and prey on insects flying out from woodlands. The woodland on the east slope of Wong Mau Hang Shan will not be affected by the Project.

Kendrick (1998) stated that insect abundance in agricultural lands is higher than in adjacent woodland or shrubland habitats. The abandoned agricultural lands in Wo Keng Shan, Ping Yeung and Lin Ma Hang are therefore considered important foraging habitats of insectivorous bats.

Outside the Study Area

A visit to Lin Ma Hang Lead Mine SSSI was made in September 2005. Bat species including Horseshoe Bats Rhinolophus spp. were observed inside the cave. The SSSI is still actively used as bat roosts during the survey.

10.6.6 Dragonflies and Butterflies

Project Area

There was no record of dragonfly in grassland, plantation and woodland. Twelve Wandering Gliders Pantala flavescens were recorded in urbanised/disturbed areas in the stockpile. In total, 11 species of dragonfly were recorded in streams/nullahs in the Project area (Appendix 10.6). All recorded species are common and widespread in Hong Kong (Wilson 2004). Abundance and species richness of dragonfly were low in the Project area, as most aquatic habitats are channelised and with simple habitat structure. These aquatic habitats were also contaminated/silted to certain degree, and their value as dragonfly habitat is low.

A total of 24 species of butterfly were recorded in the Project area (Appendix 10.7). Most recorded species are common and widespread in Hong Kong (Yiu 2004). Species richness of butterfly was low in all surveyed habitats within the Project area (Table 10.4). Abundance was low in urbanised/disturbed and grassland with low shrub and medium in plantation and woodland.

The butterfly species of conservation concern was Yellow Coster Acraea issoria. This species is very rare in Hong Kong (Yiu 2004). Yellow Coster was recorded at grassland at the Project area near Shek Tsai Ha. This species is only recorded in a few localities in Hong Kong, and is usually found in areas with their larval foodplant Boehmeria nivea and Hairy Gonostegia Gonostegia hirta (Bascombe et al. 1999). The larval foodplant of Yellow Coster were not found within the Project area. The habitat of Yellow Coster is dry abandoned agricultural land, which is not found within the Project area.

Table 10.4 : Butterfly community of habitats within Project area

Habitat

Urbanised/

disturbed

Grassland with low shrub

Plantation

Woodland

Butterfly density

(butterflies ha^-1)

6.5

17.1

Species richness

500m-Area

A total of 22 species of dragonfly was recorded in the 500m-Area (Appendix 10.8). All recorded species are common and widespread in Hong Kong (Wilson 2004).

A total of 32 species of butterfly was recorded in the 500m-Area (Appendix 10.9). Most recorded species are common and widespread in Hong Kong (Yiu 2004). Three uncommon species were recorded at the woodlands near Tong To Shan Tsuen. These were Bush Hopper Ampittia dioscorides, Banded Awl Hasora chromus and Chestnut Bob Iambrix salsala. All were recorded at abandoned cultivated lands in Lin Ma Hang.

10.6.7 Aquatic fauna

Project Area

While the concrete drains in the stockpile area were not suitable for the establishment of aquatic fauna due to the transient flows, the water in the semi-natural stream remnant was of deep brown colour, possibly due to the geological nature of the nearby soil. No aquatic fauna was recorded in these watercourses (concrete drains and stream remnant) and they had little ecological value.

On the cut slopes along the access road connecting the stockpile area, there were some rocky ditches on the slopes intercepted by concrete channels. Atyid shrimp Caridina cantonensis and Freshwater crab Somanniathelphusa zanklon were found in these ditches.

All the three species of freshwater crabs found in Hong Kong are endemic. Somanniathelphusa zanklon is typical of lowland habitats (Dudgeon and Corlett 1994). They forage in rice fields, irrigation ditches, flooded furrows and slow-flowing stream and rivers. The crabs prey on a wide range of food including freshwater snails (ibid.). They are considered of global concern by some local ecologists (Fellowes et al. 2001).

The first two pereiopods (walking legs) of atyid shrimp are chelate and are characterized by well-developed tufts of setae for the collection of food. In Hong Kong four species of this genus have been reported, namely, Caridina cantonensis, C. apodosis, Caridina trifasciata and C. serrata (Yam 2003). They are detritivores feeding mainly on leaf litter from riparian vegetation. Members of this genus are usually found in mountain streams with clean water. Among the four species, Caridina cantonensis is the most common and widespread in Hong Kong.

No fish fauna was recorded in the concrete drains, stream remnant nor the rocky ditches within the Project area during the field survey.

500m-Area

A length of concrete channel went through the site office area of the landfill within the study area. This channel drained the drains and stream remnant within the Project area and connected to Ping Yuen River.

During the April, the section of Ping Yuen River within the study area has running water but low flow with little aquatic fauna recorded. Four species of freshwater snails were found in Ping Yuen River and the adjacent agricultural lands, i.e. Sinotaia quadrata, Melanoides tuberculata, Radix plicatulus and Apple Snail Pomacea lineate (Table 10.5). They are not considered of conservation importance, while Apple Snail is an agricultural pest. Sinotaia quadrata and Melanoides tuberculata are native prosobranch freshwater snails, while Radix plicatulus is a pulmonate snail. Apple Snail originates from South America. It was first introduced into China as a pond culture species, but has become naturalised. In Hong Kong, there is no rearing of this snail and they are not taken as food. Pomacea lineata are considered an agricultural pest known to damage vegetables. None of these snails is of special conservation concern.

Greater flow volume was found in Ping Yuen River during the July survey. Three species of common exotic fish species, i.e. Mosquito Fish, Guppy and Swordtail were found. Freshwater crab Somanniathelphusa zanklon and Atyid shrimp Caridina cantonensis were also recorded. Somanniathelphusa zanklon, as mentioned above, is considered of global concern by some local ecologists (Fellowes et al. 2001).

Upstream reaches of the Lin Ma Hang Stream (including the most southward tributary which fall within the study area boundary) did not have surface flow during the March survey.

Though there was more surface flow in the Ling Ma Hang village during May 2005, the majority of the upstream reaches of the Lin Ma Hang Stream was still dry or had only very limited surface flow. No aquatic fauna was recorded in this tributary.

Table 10.5: Aquatic fauna species of Ping Yuen River

No.	Scientific Name	Common Name	Rarity*
Fish	Gambusia affinis affinis	Mosquito Fish	Common
	Poecilia reticulata	Guppy	Common
	Xiphophorus hellerii	Swordtail	Common
Snail	Sinotaia quadrata,	Snail
	Melanoides tuberculata,	Snail
	Radix sp.	Snail
	Pomacea lineate.	Apple Snail
Crustacea	Somanniathelphusa zanklon	Freshwater crab
Crustacea	Caridina cantonensis	Atyid shrimp

Outside the Study Area

The majority of Lin Ma Hang Stream was outside the study area boundary. Its tributaries joined in the lowland area near the Lin Ma Hang Village.

Lin Ma Hang Stream was studied previously in a biodiversity study by the Kadoorie Farm and Botanic Garden in 2003. During the study, 16 freshwater fish were recorded in the stream, including 2 extremely rare species Mastacemblus armatus and Rasbora steineri (Appendix 10.1). The high species diversity and the healthy and intact fish community confirmed the importance of this stream, and KFBG urged designation of this stream as an SSSI (KFGB 2004).

No field survey in Lin Ma Hang Stream was conducted for the EIA study on the Drainage Improvement in Northern New Territories – Package C

During the field survey conducted for this EIA study, 15 species of freshwater fishes were recorded in the lowland sections of the Ling Ma Hang Stream (Table 10.6). Among them, Mud Carp Cirrhinus molitorella, Common Carp Cyprinus carpio, Guppy Poecilia reticulata, and Tilapia Oreochromis mossambicus were not recorded in the previous surveys conducted by KFBG (2004). Both Mud Carp and Common Carp typically occur in large numbers in reservoirs and fishponds, but are not common in streams. Guppy and Tilapia are originally exotic species but now widespread and breed in local water bodies. The previously recorded rare fish Chinese Rasbora Rasbora steineri was also found during the survey.

Freshwater crab Cryptopotamon anacoluthon and Atyid shrimp Caridina cantonensis were also recorded in the lowland section of Ling Ma Hang Stream. Among the three freshwater crabs in Hong Kong, Cryptopotamon anacoluthon is most common, and usually more abundant than the other two species. Although relatively common and widespread in Hong Kong, Cryptopotamon anacoluthon is considered of potential global concern by some local ecologists (Fellowes et al. 2001).

Table 10.6 : Freshwater fish species of Lin Ma Hang Stream

No.	Scientific Name	Common Name	Rarity*
Fish
1	Anguilla japonica	Japanese Eel	Uncommon
2	Carassius auratus	Goldfish	Not common
3	Cirrhinus molitorella	Mud Carp	Not common
4	Cyprinus carpio	Common Carp	Not common
5	Gambusia affinis affinis	Mosquito Fish	Common
6	Hemiculter leucisculus	Wild Carp	Uncommon
7	Misgurnus anguillicaudatus	Oriental Weatherfish	Common
8	Nicholscypris normalis		Common
9	Parazacco spilurus	Predaceous Chub	Common
10	Poecilia reticulata	Guppy	Common
11	Pterocryptis cochinchinensis	Vietnam Catfish	Common
12	Rasbora steineri	Chinese Rasbora	Rare
13	Rhinogobius duospilus		Common
14	Schistura fasciolata	Striped Loach	Common
15	Oreochromis mossambicus	Tilapia	Common
Crustacea
16	Cryptopotamon anacoluthon	Freshwater crab
17	Caridina cantonensis	Atyid shrimp

* Follow AFCD 2004.

10.7 Evaluation of Habitats and Species

The ecological importance of the habitats within the study area was evaluated in accordance with the criteria stipulated in Annex 8 of EIAO TM.

Table 10.7: Evaluation of natural woodland habitat within the study area

Criterion	Description
Naturalness	Natural habitat
Size	74.18 ha
Diversity	Moderate plant diversity. Low fauna diversity.
Rarity	Endospermum chinense (locally restricted), Rhododendron simsii and Pavetta hongkongensis (locally protected but common), Aquilaria sinensis (protected locally and in China but common in Hong Kong), Cibotrium barometz (protected locally and in China but very common in Hong Kong). No rare terrestrial fauna recorded.
Re-creatability	Difficult to recreate and takes time to mature
Fragmentation	Continuous patch in Lin Ma Hang and scattered along ravines on other hillslopes
Ecological linkage	Linked to Lin Ma Hang Stream
Potential value	High with protection
Nursery/breeding ground	No significant record, but can provide breeding habitats for birds, reptiles and butterflies
Age	More mature at Tong To Shan and Wo Keng Shan, relative younger within the Project Area and elsewhere
Abundance/richness of wildlife	Medium to high bird abundance, low butterfly abundance
Overall ecological value	Moderate to high

Table 10.8: Evaluation of plantation woodland habitat within the study area

Criterion	Description
Naturalness	Man made (planted) with some natural colonisation
Size	7.86 ha
Diversity	Low fauna diversity
Rarity	No rare species recorded
Re-creatability	Easy to recreate
Fragmentation	Formed thin belts on engineering slopes
Ecological linkage	Not functionally linked to habitats of conservation importance
Potential value	Moderate with active management including thinning and interplant with native species
Nursery/breeding ground	No significant record. Value as breeding habitat for terrestrial fauna is low due to sparse canopy and made up of exotic tree species.
Age	Young, probably about 20 years.
Abundance/richness of wildlife	Low avifauna abundance, medium butterfly abundance
Overall ecological value	Low

Table 10.9: Evaluation of grassland with low shrub habitat within the study area

Criterion	Description
Naturalness	Natural but frequently disturbed by fire
Size	155.25 ha
Diversity	Low fauna diversity
Rarity	Two protected but common orchids (Spathoglottis pubescens and Arundina graminifolia) A very rare butterfly Yellow Coster
Re-creatability	Maintained by hillfire
Fragmentation	Continuous stands on hillsides
Ecological linkage	Not functionally linked to habitats of conservation importance
Potential value	Low due to presence of grave sites
Nursery/breeding ground	No significant record. Value as breeding habitat for terrestrial fauna is low due to high level of disturbance and low vegetation cover
Age	N/A
Abundance/richness of wildlife	Low fauna abundance
Overall ecological value	Low

Table 10.10: Evaluation of stream/channel habitat within and outside the study area

Criterion	Description
	Within the Project area	Within the study area		Outside the study area
Naturalness	Channels inside landfill were man-made or semi-natural but disturbed.	Include both artificial (the concrete channel near the landfill site office) and natural (Ping Yuen River and the most southward tributary of Lin Ma Hang Stream) watercourses.		Lower reach of stream near Shenzhen River was highly modified, upper reach was fairly natural.
Size	2,900 m (stream remnant and channels inside existing landfill)	314 m (Concrete channel) 250 m (Ping Yuen River) 1343 m (Lin Ma Hang Stream tributary)		3180 m (Lin Ma Hang Stream outside study area)
Diversity	Low within the Project area and the study area.	Moderate within the study area		High (15 spp. of freshwater fish, and two spp. of crustaceans) in Lin Ma Hang Stream which is outside the study area boundary.
Rarity	The habitat type is not rare in Hong Kong. No rare aquatic fauna was recorded.			One rare fish was found.
Re-creatability	Re-creatable			Not re-creatable
Fragmentation	N/A
Ecological linkage	No fauna was found in the semi-natural stream remnant during the field surveys. Only hydrologically connected to Ping Yuen River, but no special ecological linkage was identified.		The concrete channel hydrologically connects the Ping Yuen River with the stream remnant and channels inside existing landfill. The upstream part of Lin Ma Hang joins the downstream part outside the study area and ecologically connected (maintaining a complete stream profile from upstream to downstream).	Received water flow from the upstream section within the study area. With riparian habitats in the vicinity.
Potential value	Low for the channels within the Project area		Low for the stream courses within the study area. .	Moderate for Lin Ma Hang Stream
Nursery/breeding ground	No nursery/breeding ground of special value was identified, but streams/channels can provide breeding habitats for dragonflies and amphibians.
Age	N/A
Abundance/richness of wildlife	Low within the Project area.		Moderate in the study area.	High in Lin Ma Hang Stream outside the study area
Overall ecological value	Low within the Project area.		Moderate in the study area.	High in Lin Ma Hang Stream.

Table 10.11: Evaluation of abandoned agricultural fields habitat within the study area

Table 10.12: Evaluation of urbanised/disturbed habitat within the study area

Criterion	Description
Naturalness	Man made habitat
Size	49.84 ha
Diversity	Low fauna diversity
Rarity	No rare terrestrial fauna recorded
Re-creatability	Easy to recreate
Fragmentation	None
Ecological linkage	Not functionally linked to habitats of conservation importance
Potential value	Low
Nursery/breeding ground	No significant record. Value as breeding habitat for terrestrial fauna is low due to high level of disturbance and low vegetation cover
Age	N/A
Abundance/richness of wildlife	Low fauna abundance
Overall ecological value	Low

In accordance with Table 3, Annex 8 of the EIAO-TM, the ecological value of species was assessed in terms of protection status (e.g. fauna protected under WAPO (except birds), and flora and fauna protected under regional/global legislations/conventions), species distribution (e.g. endemic), and rarity (e.g. rare or restricted). The list and evaluation of the flora and faunal species of conservation concern recorded within the study area, according to the TM-EIAO, are given in Tables 10.13 and 10.14.

Table 10.13: Evaluation of floral species of conservation importance within the study area

Common name	Scientific name	Locations	Protection status	Distribution	Rarity
Incense Tree	Aquilaria sinensis	In woodland within the Project area	Protected under Protection of Endangered Species of Animals and Plant Ordinance, CITES Appendix II, Category II nationally protected species in China and is listed as vulnerable in the China Plant Red Data Book and by IUCN (2002).	Lowland forests and fung shui woods	Locally common
Endospermum	Endospermum chinense	In woodland within the Project area	Not protected	Lowland forests and fung shui woods	Restricted
Red Azalea	Rhododendron simsii	In woodland fringe within the Project area	Protected under Forestry Regulations	Shrubland and woodland	Very common
Pavetta	Pavetta hongkongensis	In woodland fringe outside the Project area	Protected under Forestry Regulations	fung shui woods and lowland forest	Common
Lamb of Tartary	Cibotium barometz	In woodland outside the Project Area	Protected under Protection of Endangered Species of Animals and Plant Ordinance, also in Appendix II of CITES	Forest and shrubland	Very Common
Bamboo Orchid	Arundina graminifolia	Grassland within the Project area	Protected under Forestry Regulations	grassland and streamsides	Very common
Buttercup Orchid	Spathoglottis pubescens	Grassland outside the Project area	Protected under Forestry Regulations	grassland	Very common

Table 10.14: Evaluation of faunal species of conservation importance within the study area

Common name	Locations	Protection status	Distribution	Rarity
Japanese Pipistrelle Pipistrellus abramus	Urbanised/disturbed within the Project area	Wild Animals Protection Ordinance (Cap 170)	Widely distributed in Hong Kong,	Common in Hong Kong
Himalayan Roundleaf Bat Hipposideros armiger	Existing landfill within the Project area	Wild Animals Protection Ordinance (Cap 170)	Widely distributed in Hong Kong.	Common in Hong Kong
Leschenault’s Rousette Rousettus leschenaultii	Existing landfill within the Project area	Wild Animals Protection Ordinance (Cap 170)	Widely distributed in Hong Kong.	Common in Hong Kong
Black Kite Milvus lineatus	Existing landfill within the study area	Wild Animals Protection Ordinance (Cap 170); Class 2 Protected Animal of PRC; Appendix 2 of CITES	Widely distributed in Hong Kong	Common in Hong Kong
Collared Scops Owl Otus lempiji	Roadside plantations within Project area and near the entry of NENT Landfill	Wild Animals Protection Ordinance (Cap 170); Class 2 Protected Animal of PRC; Appendix 2 of CITES	Widely distributed in Hong Kong	Common in Hong Kong
Emerald Dove Chalcophaps indica	Woodland near Tong To Shan Tsuen within the study area	Wild Animals Protection Ordinance (Cap 170)	Widely distributed in Hong Kong, occurs in well-wooded areas	Rare
Greater Coucal Centropus sinensis	Shrubland in Ngong Tong within the Project area	Wild Animals Protection Ordinance (Cap 170); Class 2 Protected Animal of PRC	Widely distributed in Hong Kong, occurs in many types of habitats	Common
Chinese Bullfrog Hoplobatrachus chinensis	Lowland section of Lin Ma Hang Stream	Class 2 Protected Animal of PRC	Widely distributed in Hong Kong, occurs in lowland wetlands	Common
Yellow Coster Acraea issoria	Grassland at Shek Tsai Ha within the Project area	Not protected	Only found in a few localities in Hong Kong	Very rare
Freshwater crab Somanniathelphusa zanklon	Ditches on slopes inside the Project area and Ping Yuen River	Not protected	Widely distributed in Hong Kong.	Common
Freshwater crab Cryptopotamon anacoluthon*	Lowland section of Lin Ma Hang Stream	Not protected	Widely distributed in Hong Kong.	Common
Chinese Rasbora Rasbora steineri*	Lowland section of Lin Ma Hang Stream	Not protected	North District and Kam Tin	Rare

* Recorded outside the study area.

10.8 Impact Identification and Evaluation

A detailed comparison of the ecological benefits and dis-benefits of all possible extension areas was made in the early stage of this EIA study (e.g. Value Management and the Option Assessment) and the results were summarised in Section 2 of this report, which recommended Option 4 as the preferred extension area to avoid adverse environmental impact to the maximum practicable extent. In particular, consideration was given to avoid or minimize the disturbance to the ecosystems in the adjacent areas including the Lin Ma Hang Stream and Robin’s Nest.

The potential terrestrial and aquatic ecological impacts arising from the construction works of the preferred option, including loss of habitats, removal of vegetation, and disturbance to animals were quantitatively assessed in accordance with Annexes 8 and 16 of the TM-EIAO. Particular attention was paid to the following:

· Habitat loss & removal of vegetation

· Disturbance to wildlife.

· Impacts on aquatic fauna due to changes in water qualities, hydrodynamics properties, sedimentation rates and patterns, and hydrology.

· Impacts to hydrodynamic regime of the Lin Ma Hang Stream and its associated water system in the catchment area and aquatic life during the construction and operation stages;

· Impacts to the aquatic life due to the accidental leakage of leachate and/or other wastewater;

· Impacts to the wildlife due to the accidental leakage of landfill gas;

· Impacts of habitat loss in the Robin’s Nest and wildlife therein due to the Project;

· Impacts to the bats inhabiting in the nearby Lin Ma Hang Lead Mines because of loss of foraging ground due to the Project; and

· Cumulative impacts due to other proposed development projects in the vicinity for example, the proposed drainage improvement work.

10.8.1 During Excavation and Landfill Operation

Recognised Sites of Conservation Importance

Among all the recognised sites of conservation importance within and in the vicinity of the study area, none will be directly impacted. Lin Ma Hang Lead Mines SSSI is located about 1km from the proposed landfill extension and therefore will not be affected by the Project. Lin Ma Hang Stream and its catchment would be completely avoided by Option 4 and therefore would not be affected. There will be no reduction in surface flow or change in ground water level at Ling Ma Hang Stream.

Option 4 would encroach the Robin’s Nest countryside at the eastern corner of the proposed extension, which is also part of the existing landfill. The impact of loss of habitats as a whole, including the Robin’s Nest countryside is assessed below.

Habitats and Vegetation

Option 4 would avoid key area of Tong To Shan Archaeological Site (TTSAS) and therefore avoid encroachment to the Lin Ma Hang natural woodland (and also the Lin Ma Hang Stream catchment).

The direct ecological impact of excavation and landfill operation would be loss of habitats. Option 4 would cause losses of 4.01 ha of native woodland, 47.64 ha of grassland with low shrub, 4.76 ha of plantation, 0.12 ha of abandoned agriculture, 6.89 ha of urbanised/disturbed and 2,530m of stream/channel habitat (including 1820m of concrete channel, 2 ditches of 256m and 84m, and a section of natural stream remanant of 370m).

Most of the habitat losses will occur within the existing NENT Landfill boundary (Table 10.15). Loss or disturbance to these habitats within the existing NENT Landfill boundary (e.g. the native woodland at the eastern end of the proposed extension boundary) had been taken into account during the planning and establishment of the existing NENT Landfill, and mitigation measures proposed for this Project would also cover the loss of habitats within the existing landfill boundary.

Table 10.15: Habitat loss due to Landfill Extension

Habitat type	Total	Within NENT Landfill boundary		Caused by Option 4
	Area (ha)	Area (ha)	Percentage of total loss (%)	Area (ha)	Percentage of total loss (%)
Abandoned Agriculture	0.12	0.01	8.3	0.11	92.7
Grassland with low shrub	47.64	20.95	44.0	26.69	56.0
Natural Woodland	4.01*	2.56	63.8	1.45	36.2
Plantation Woodland	4.76	4.76	100.0	0	0
Urbanised/Disturbed	6.89	6.88	99.9	0.01	0.1
Total	63.42	35.16	-	28.26
Stream/channel** (length)	2,530m	1,735m	68.5	795m	31.5

* Only (4.01 – 2.56») 1.5ha loss of natural woodland. The 2.56 ha within existing landfill boundary will be disturbed by the stockpile activities anyway.

**including 1820m of concrete channel, 2 ditches of 256m and 84m, and a section of natural stream remanant of 370m.

Amongst the 4.01ha of woodland to be encroached, 2.56ha would fall within the existing NENT Landfill Boundary while 1.45ha falling outside the existing NENT Landfill Boundary would be affected due to the NENT Landfill Extension Project.

According to Table 10.7, these woodland patches to be lost are of moderate ecological values. Compared to the woodland at Tong To Shan and Lin Ma Hang catchment, most of the natural woodland to be lost is relatively younger in age but also has moderate plant diversity. It supports four species of flora of conservation importance (including Aquilaria sinensis, Rhododendron simsii, Endospermum chinense, and Arundina graminifolia), 2 bird species (Collared Scops Owl and Greater Coucal) and 3 bat species of conservation interest.

For the 2.56 ha woodland within the existing NENT Landfill, some of them are located at the east near the Stockpile and Borrow Area and will be disturbed during the restoration of the existing landfill. One patch of woodland (1.2 ha) to be lost is located in the centre of the existing landfill and is isolated in nature, while another patch (0.25 ha) is located at the fringe of the existing landfill area. Loss of these woodland patches (4.01 ha) and other habitats would occur in phases due to progressive change in topography of the site during the construction and operation phases of the landfill extension development over 10-12 years and therefore the extent of impacts would be diluted.

Despite the young age, isolated nature and progressive loss of the woodland within the Project area, due to moderate quality of habitat, and irreversible nature, long duration and moderate magnitude of impacts, the overall potential impact due to site formation is considered moderate (Table 10.16). Mitigation measures are required and should include compensatory woodland planting for the natural woodland loss and transplantation of flora of conservation importance.

Landfill gas contains methane and carbon dioxide may have adverse effects on plant growth by suppressing the oxygen level in soil and thus the root establishment. With high quality of composite cap, leachate contamination and landfill gas migration to cover soil is unlikely. Accidental leakage of landfill gas would not affect the vegetation during the excavation and operation phase as the site would be void of vegetation. During the restoration phase the effect of accidental leakage would be temporarily and would not post long term effect on plant growth. Planting of exotic species tolerant to landfill gas during the initial establishment stage and native species more sensitive to landfill gas at the later stage would also alleviate the problem.

Toxic substances in leachate might affect plant growth. Accidental leakage of leachate, if any, would not affect the vegetation during the excavation and operation phase as the site would be void of vegetation. During the restoration phase, in case of accidental leakage the effect would be temporarily and therefore would not cause long term effect on the plants.

Terrestrial Fauna

Habitats would be lost due to the proposed extension include natural woodland, abandoned agriculture, grassland with low shrub, plantation woodland, urbanised/disturbed and stream/channel. Apart from natural woodland, the affected habitats are highly disturbed and of low fauna abundance. Natural woodland will be lost to the proposed landfill extension are of younger age and are either isolated patches or on the edge of a continuous woodland, and are probably inhabited by habitat generalists. Most of these woodlands are located within the existing landfill. The loss of 4.01 natural woodland from the proposed extension would be a small proportion of all natural woodlands within the study area (4.01 ha out of 74.18 ha, i.e. 5.4 %). The nearest natural woodland would be in close proximity (within 1 km) from the lost woodland. Fauna inhabiting these woodlands should easily locate and utilise the remaining woodlands nearby. In addition, the loss of habitat will be progressive in phases over 10-12 years. The impact to terrestrial fauna due to loss of these habitats is anticipated to be minor.

Although some fauna species of conservation concern were recorded within the Project area (see Table 10.14), the affected areas are not optimal habitats of these species. The population of these species that could be supported by the Project area is not likely to be large.

The proposed extension is not going to affect the important habitat of Yellow Coster (dry abandoned agriculture) and Emerald Dove (large old woodland). The impact to these two species will be minimal.

The potential impact to Black Kite is considered minimal as this species forage in disturbed areas, including the existing landfill.

The Project might affect foraging habitats of Collared Scops Owl and Greater Coucal. However, the habitats would be lost from the proposed landfill extension would be mainly disturbed (e.g., urbanised/disturbed, grassland) and are not important habitats for these two species. As areas would be lost do not contain optimal habitats of these species, the number of individuals affected may not be high and alternative habitats are available in nearby area, e.g., Lin Ma Hang, Wo Keng Shan, Robin’s Nest, potential impacts to these two species were ranked as minimal.

The potential impact to bats will be the loss of foraging habitats. The perennial stream will be affected by the proposed landfill extension, and associated woodland habitats would be lost to the landfill extension. Loss of habitats due to site formation, however, would be progressive in phases over 10-12 years. Other optimal bat foraging habitats (e.g., cultivated lands) are available immediately outside the proposed landfill extension, such as the areas along Ping Yuen River and those along Lin Ma Hang Stream. This impact to the bats is considered minor. Compensatory planting would also include tree species with berries and figs to provide food sources for fruit bats.

There will be no direct impact to the Lin Ma Hang Lead Mine SSSI. The impact to bats roosting in this lead mine will mainly be potential loss of foraging habitats, which is anticipated to be minimal. The Project area is more than 1.6 km from the Lin Ma Hang Lead Mine SSSI, and might not be important foraging habitats to the bat roosting in there. Optimal foraging habitats of bats discussed in Section 10.6.5 are present near the Lin Ma Hang Lead Mine SSSI at Lin Ma Hang and San Kwai Tin.

The fauna community utilising the Project area during operating phase will mainly be those typical of disturbed areas, which are of high mobility. It is also anticipated that the fauna abundance will be low due to low vegetation cover, as seen in the existing landfill. The covering seals in operating landfill will slow down the rate of emission of landfill gas in case any accidental leakage happens. In addition, the chance of accumulation of landfill gas in open areas to the level dangerous/lethal to wild animals must be very low. The animals may also leave the site before they are far too weakened. The potential impact to terrestrial fauna due to accidental leakage of landfill gas is anticipated to be minimal.

Aquatic Habitat and Fauna

Direct Loss : The potential impacts to Lin Ma Hang stream and catchment were considered. The Lin Ma Hang upstream headwater is located at least 100m always from the conforming extension boundary. As the development of the northern boundary of the proposed extension is most sensitive to the Tong To Shan Archaeological Site, Option 4 would completely avoid the Lin Ma Hang natural woodland. There would be no physical encroachment and no drainage impacts to Lin Ma Hang Stream or its catchment. Both the surface flow and groundwater flow of Lin Ma Hang Stream would not be impacted.

There would be a loss of 2,530m of stream/channel within the proposed extension (see Table 10.15). Among them, 1,733 would be within the existing NENT Landfill boundary. Loss or disturbance to the habitats within the existing landfill boundary (i.e. the stream remnants, channels and ditches) had been taken into account during the planning and establishment of the existing NENT Landfill, any loss from the existing NENT Landfill Project would not be an additional loss. Furthermore, the stream/channel habitat within the Project area (the boundary of the proposed extension) is of low ecological value (see Table 10.10).

The only aquatic fauna of conservation importance within the Project area is the Freshwater Crab Somanniathelphusa zanklon found in the rocky ditches on the cut slope. This species however is common in Hong Kong and considered typical of lowland habitats (Dudgeon and Corlett 1994). This crab was also found in Ping Yuen River within the study area (the downstream section of the channels in the Project area). The impact on this species from the loss of the channels inside the Project area was therefore considered acceptable, and impacts from habitat loss to the stream ecology would therefore be minimal.

Changes in Water Qualities : During the operation phase of the landfill the tipping face will remain substantially exposed. Due to contact with the waste material, all run-off generated from within it will be collected and treated. Groundwater will be protected by an impermeable barrier fully lined within the landfill. All leachate will be diverted to the leachate treatment plant for treatment within the landfill prior to being conveyed to nearby sewage treatment works. Lin Ma Hang Stream is located in another catchment area separated from the landfill by a ridgeline and thus would not have any potential to be impacted by the runoff (no encroachment to Lin Ma Hang Catchment). Impacts on natural stream habitat due to water quality changes are not anticipated. The rare freshwater fish Rasbora steineri and another freshwater crab Cryptopotamon anacoluthon which recorded in the lowland reach of Lin Ma Hang Stream also would not be impacted by the Project.

Hydrology : The proposed extension boundary is located mostly (over 95%) within the head of the catchment for Ping Yuen River. But currently the majority of surface runoff from this catchment is directed towards engineered surface drainage channels surrounding the proposed extension area and along Wo Keng Shan Road. Compared with other catchments feeding to Ping Yuen River, this affected catchment would be of less importance to the recharging of groundwater table due to its higher proportion of runoff than infiltration caused by the steep hill slopes.

According to the drainage impact assessment, during construction and operation, there would be only slight fluctuation of water level of Ping Yuen River (between 1mm to 9mm) due to change in catchment area and change in extent of impermeable area. The aquatic fauna found in Ping Yuen River was low in both diversity and abundance, and all species are widespread in Hong Kong. Therefore, potential impacts to Ping Yuen River and associated aquatic fauna were considered minor. Mitigation measures are therefore not required.

Furthermore, Lin Ma Hang Stream is located in another catchment area. There would be no change in surface flow at Lin Ma Hang Stream. No impacts on the freshwater crab Cryptopotamon anacoluthon and the rare freshwater fish Rasbora steineri, which were recorded in the lowland reach of Lin Ma Hang Stream, were anticipated. No mitigation is therefore required.

Sedimentation Rates and Patterns : There is no encroachment to Lin Ma Hang Catchment and there is no influence on existing flow or sedimentation rate. As all runoff at the hill slopes within the landfill will be diverged through surface channel. All the run-off will pass through sedimentation process before discharging into the nearby stream courses into Ping Yuen River. No sedimentation impact on the streams will be caused by the landfill.

Accidental Leakage of Leachate and/or Other Wastewater : Leachate is the rain water that passes through the active tipping face of the landfill and picks up dissolved, colloidal, and suspended solids in concentrations that vary widely in different local conditions. It may contain high concentration of ammonia, nitrogen radicals, organic acids, dissolved salts, (sodium in particular), and various heavy metals, e.g. lead, zinc.

All leachate would be collected and conveyed for treatment. The two layers of impermeable barriers (one layer on the bottom of waste filling, while the second layer on the top of the waste filling and beneath the cap soil) could effectively prevent any accidental leakage of leachate in case the collection system failed. There would also be a contingency plan for the accidental leakage of leachate (see below sections). The seepage / leakage of leachate due to damage of liner system has also been addressed in the water quality section (section 5.6.2.2). In practice, an average of 1 defect per ha of liner could be easily achieved by good manufacturing quality and QA/QC programme. The impact on groundwater quality due to seepage / leakage of leachate will be negligible. The leaked leachate reaching the layer will be drained to the leachate treatment works downstream and treated as ordinary leachate before discharge if the corresponding trigger levels have been exceeded. The impact on groundwater quality due to seepage / leakage of leachate is therefore assessed to be unlikely. Therefore, no impact on stream water quality or stream ecology is anticipated.

Potential Collection of Hazardous Waste in the Future (when SENT landfill is closed) : Upon closure of SENT landfill, the proposed NENT Landfill Extension may have to receive hazardous waste including ash from Integrated Waste Management Facility (IWMF) and chemical waste. The collection and disposal of all these chemical waste and hazardous waste are properly controlled and documented. These wastes are in general treated by fixation and tested with chemical leakage test (e.g. TCLP) before disposal to landfill site. A special area/trench is designated for the disposal of such waste. The leachate will be conveyed to leachate treatment plant for pre-treatment before diverting to DSD sewage treatment works for final treatment. Heavy metal or toxic substances will be removed within the landfill leachate treatment plant. All the effluent will comply with the condition of the effluent discharge licence. Similar to SENT landfill, bench-scale test in laboratory and special pilot tests within site should be conducted by the DBO Contractor (during detailed design stage when the nature of IWMF waste is materialised) to test the effectiveness of the leachate/surface water collection system before any full-scale operation. So far, no incident of accidental spillage or other environmental problems were caused by disposal of chemical/hazardous waste at SENT and WENT landfills and other international landfills (such as Japan with the implementation of IWMF). Should the treatment and disposal procedure follow international guidelines and comply with the existing health risk standards for human and environmental safety, no potential impact on ecology is anticipated. No mitigation is therefore required.

Cumulative impacts with other proposed development projects

Drainage improvement works were proposed in the lower reach of Lin Ma Hang Stream under the Drainage Improvement in Northern New Territories – Package C. These works would be conducted in a separate catchment area and thus would not have cumulative impacts with the present project. There is no other major development within the study area. Therefore the NENT Landfill Extension Project would not constitute significant cumulative ecological impacts in the surrounding area.

10.8.2 Upon Landfill Restoration

Terrestrial Habitat and Fauna

Upon completion of operation and during the restoration phase, the landfill site would be restored by planting of woodland, shrubland and grassland species (see Section 10.9 and LVIA chapter). The planting and maintenance would be implemented by the DBO Contractor, who will take care of the site for 30 years after restoration. No adverse ecological impact to the surrounding terrestrial habitats and associated fauna is anticipated.

Aquatic Habitat and Fauna

According to the groundwater impact assessment, upon completion of the landfill works, the site would be capped with a second impermeable barrier for afteruse. Any surface run-off generated over the area would then be collected by the surface drainage channels. Given that it would have had no interaction with the underlying waste material, the surface run-off would be of a high enough quality to be discharged directly into the downstream river systems. New drainage channel will be provided along the site boundary to convey all the surface run-off to Ping Yuen River. There will be no encroachment to Lin Ma Hang catchment and thus there will be no impact on Lin Ma Hang Stream.

According to the Drainage Impact Assessment and Water Quality Assessment, there would be no deep infiltration of groundwater following landfill restoration due to the capping layer provided. Although there will be a subsequent reduction in the recharging of the groundwater levels within the extension area, all precipitation however will be mobilised as either surface run-off or interflow through the topsoil material and supplement the surface water flow for the Ping Yuen Catchment, resulting in an increase of water level by 35mm at Ping Yuen River compared to those in existence prior to the landfill development. The ecological impacts due to changes in surface runoff are anticipated to be minor. No mitigation is required during the restoration phase.

The construction, operation and the restoration phase impacts are summarised in Table 10.16 and 10.17.

Table 10.16 Construction and Operation Phases Impacts

Activity	Source	Receiver	Nature of Impacts						Severity	Mitigation Required
			Habitat quality	Species affected	Size-abundance	Duration	Reversibility	Magnitude
Site formation	Site preparation	Terrestrial habitat and associated flora and fauna	All except woodland habitat are of low ecological importance	Fauna and flora species recorded in the project area, including 4 plant species of conservation interest affected, 2 bird species (Collared Scops Owl and Greater Coucal) and 3 bat species of conservation interest, would be affected	Of the 63.42 ha of the Project area to be affected, 4.01 ha of woodland is of moderate ecological value.	Long term and permanent	Irreversible	Moderate	Moderate	Yes, detailed surveys and transplantation of species of conservation interest (under circumstance technically feasible), compensatory planting
Noise, dust and visual disturbance	Works equipment and human activities	Faunal species on adjacent habitats	Terrestrial habitats affected are of low ecological importance	Disturbance tolerant fauna	Terrestrial habitats affected confined to areas adjacent to work areas.	Temporary	Reversible	Low	Minor	Yes, good site practice
Changes in Water quality	Site runoff and leachate	Aquatic fauna	Low for Ping Yuen River	Common species	N/A	Temporary	Reversible	Low (all runoff and leachate will be transferred offsite for treatment	Minor	Yes, good site practice
Changes in Hydrology	Site runoff	Aquatic fauna	Low (Ping Yuen River)	Common species	N/A	Temporary (flow to be restored at restoration phase)	Reversible	Significant during construction and operation stages	Minor	No

Table 10.17 Restoration phase impacts

Activity	Source	Receiver	Nature of Impacts						Severity	Mitigation Required
			Habitat quality	Species affected	Size-abundance	Duration	Reversibility	Magnitude
Compensatory Planting	Planting activities	New landfill site	Low on finished landfill site	Few/none on new capped surface	Over 30 ha to be replanted	5 years of planting	Irreversible	Moderate	Positive impact	No
Construction of drainage network to redirect surface runoff	Surrounding surface runoff	Ping Yuen River	Low on finished landfill site	Few/none on new capped surface	Increase in water level by 35mm	Permanent	Irreversible	Moderate	Minor	No

10.9 Impact Avoidance and Mitigation Measures

Following EIAO-TM Annex 16 guidelines, mitigation measures are discussed in this section to avoid, minimise and compensate for identified ecological impacts.

10.9.1 Impact Avoidance

As described in Chapter 2, Option 4 has been carefully selected through the option assessment process to avoid / minmise impacts on most sites, habitats and species of conservation importance. Although Option 4 is not ranked the highest ecologically, it has avoided Lin Ma Hang Stream and its catchment completely. Direct and indirect impacts on Lin Ma Hang Stream and its catchment and associated woodland habitats are therefore completely avoided.

10.9.2 Impact Minimisation

Due to the large area required for the Project, loss of important habitats such as woodland is unavoidable. Option 4 has been identified as the preferred design with favourable comparisons on waste management (achieving the target requirement), engineering considerations (no imported fill material required for the site formation works, no drainage impacts on Lin Ma Hang catchment), environmental constraints (no ecological impacts on Lin Ma Hang Stream), and social acceptability (highest landfill areas with gentle slopes/ gradient, comparable unit cost for disposal). In comparing with Option 1 (the conforming option), the northern boundary of Option 4 is set back to minimize the impact to mature woodland at Lin Ma Hang.

Option 4 would cause a loss of 4.01 ha woodland of which 2.56 ha is located at the east of the existing stockpile and borrow area. Other options with less woodland loss by adjusting landfill boundary in the east could only result in a minor reduction in woodland loss but resulting in significant reduction of landfill capacity of 10%. This will definitely affect the waste management needs and also increase the unit disposal cost of 13% and therefore is not preferred. In fact, set back the extension boundary at the east would not help to prevent woodland loss. The existing Stockpile and Borrow Area was allocated to the existing NENT Landfill Contractor in 1994 and this area will be disturbed by the existing NENT Landfill Contractor during the restoration period of the existing landfill.

The remaining 1.45 ha woodland being affected is location in the heart of the landfill extension and is also the valley of the landfill bowl, which is unavoidable in any of the proposed layout options.

Impacts on woodland loss would be mitigated by compensatory planting. Although loss of woodland habitat within the existing landfill boundary should have been addressed by the environmental assessment for the existing landfill, the current EIA would also cover the compensation of habitat loss in this area by anticipating a high ratio of woodland compensatory planting (see below).

The surveys conducted under this EIA identified at least four plant species of conservation interest within the Project area that would have been directly impacted by the proposed landfill extension. The group tree surveys recorded 2 no. of Aquilaria sinensis and 3 no. of Endospermum chinense, while the ecological surveys recorded 2 no. of Rhododendron simsii and about 10 no. of Arundina graminifolia. To minimise the ecological impacts, the affected individuals would be transplanted to suitable nearby habitats prior to the construction phase as far as practicable. A detailed vegetation survey covered the affected habitats would be conducted prior to the commencement of site clearance works by a suitably qualified botanist /ecologist. The aim of the survey is to update, identify and record the location and number, health condition and suitability for transplantation of the affected individuals in order to provide details for the transplantation scheme. The requirements of detailed vegetation survey will be specified in the NENT Landfill Extension Contract.

According to the LVIA, due to the fact that the habitats are located to slopes inaccessible to vehicles and machineries, the majority of them may not be likely to be preserved by transplanting. However, it is recommended to preserve among them, some which are of rare and precious species (e.g. Aquilaria sinensis, Endospermum chinense) by transplanting as far as technically and financially feasible. Feasibility and suitability of transplanting the affected plant species of conservation interest would be carefully studied and suitable receptor sites would be identified by the transplantation scheme. Examples of the potential receptor site for Aquilaria sinensis and Endospermum chinense will be fringe of Ling Ma Hang Woodland immediately to the north of the Project Area, while potential receptor site for Rhododendron simsii and Arundina chinensis will be grassland habitat along the southeast boundary of the Project Area. Proximity of the receptor sites to the Project Area will allow access for transplantation and monitoring while avoiding potential disturbance inside the Project Site due to earthwork.

To ensure good preparation of the transplantation work, the transplantation scheme should be formulated during the detailed design stage for this Project based on the information collected during the detailed vegetation survey. It should include careful selection of receptor sites, detailed transplantation methodology, and should be implemented and supervised by a suitably qualified botanist / horticulturist. A monitoring programme should be set out to monitor the survival and evaluate the successfulness of transplantation.

Good site practices and precautionary measures should be implemented to avoid encroachment onto the nearby natural habitats, minimise disturbance to wildlife, and ensure good water quality. Examples are detailed in various sections of the EIA report and they include:

· Placement of equipment or stockpile in designated works areas and access routes selected on existing disturbed land to minimise disturbance to natural habitats.

· Restriction of construction activities to the work areas that would be clearly demarcated.

· Reinstatement of the work areas immediately after completion of the works.

· Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction programme.

· Machines and plant (such as trucks, cranes) that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum.

· Plant known to emit noise strongly in one direction, where possible, be orientated so that the noise is directed away from nearby NSRs.

· silencers or mufflers on construction equipment should be properly fitted and maintained during the construction works.

· mobile plant should be sited as far away from NSRs as possible and practicable.

· material stockpiles, site office and other structures should be effectively utilised, where practicable, to screen noise from on-site construction activities.

· use of “quiet” plant and working methods.

· construction phase mitigation measures in the Practice Note for Professional Persons on Construction Site Drainage.

· design and set up of the temporary on-site drainage system will be undertaken by the DBO Contractor prior to the commencement of construction.

· design and incorporation of silt/sediment traps in the permanent drainage channels to enhance deposition rates and regular removal of deposited silt and grit.

· minimization of surface excavation works during the rainy seasons (April to September), and in particular, control of silty surface runoff during storm events, especially for areas located near steep slopes.

· regular inspection and maintenance of all drainage facilities and erosion and sediment control structures to ensure proper and efficient operation at all times and particularly following rainstorms.

· provision of oil interceptors in the drainage system downstream of any oil/fuel pollution sources.

10.9.3 Impact Mitigation

Habitat Loss

Most of the landscape and visual mitigation measures proposed during the construction and operation phases are temporary, including screening tree planting and boundary Green Belt planting. All the permanent and effective mitigation measures for habitat loss have to be implemented after capping is completed in the restoration and afteruse phases, i.e. in around 2021. A total of 26.83 ha will be planted for mitigating landscape impact and woodland loss. The proposed woodland planting would form a piece of contiguous woodland of substantial size and will join up with the existing natural woodland in the vicinity (see Drawing No. 24315/14/009). Assuming tree seedlings / whips planting at 1.5m spacing in staggered pattern, about 148,100 nos. of tree seedlings / whips will be planted. Details of the woodland planting are described in Table 8.10 of the LVIA and are summarised as follows.

Although the 4.76 ha of plantation would be lost is of low ecological value and does not require ecological mitigation, the compensation planting which serves as a landscape mitigation measure will cover this loss from a landscape viewpoint. Among the 26.83 ha of compensatory woodland planting, 4.76 ha would be regarded as compensation for the plantation loss in a ratio of 1:1 in terms of area. As the proposed tree list would include many native species especially during the second phase of planting (see Table 8.14), the compensatory woodland planting would be of higher ecological value than the original plantation. There would be ecological enhancement in addition to the 1:1 ratio compensating planting.

The remaining 22.07 ha of woodland planting would compensate for the loss of 4.01 ha of natural woodland, resulting in a 5.5: 1 compensation ratio in terms of area. Most native trees had extremely high mortalities on the local test site in the first few years after the capping of landfill. After several years, the pioneer species provide shelter for the native species and the survival rate and growth of native species will improve. Natural ecological succession also takes place as the pioneer species establishes. Therefore, planting of tree seedlings is preferable to be carried out in two phases. The first phase involves planting of landfill pioneers tree species (including 12 exotic species and 3 native species, see Table 8.14). The second phase, 3 – 5 years after the completion of first phase, involves the planting of seedlings of 26 native tree species of higher ecological values (also see Table 8.14). This high compensation ratio (5.5:1) is justified to partly off-set impacts due to (1) the time-lag between the site clearance (habitat destruction) and compensatory planting (to be commenced tentatively in 2021, about 15 years from now, and takes another 15-20 years to develop) when it becomes old enough to provide habitats to wildlife, and (2) availability (which will be planted at a later phase) and survival (higher mortality in landfill site) of native species to be planted. It is aniticipated that this compensatory planting proposal would fulfil the requirement set out in ETWB TC No. 3/2006 that implementation of compensatory planting should be of a ratio not less than 1:1 in terms of quality and quantity within the site.

In addition to 26.83ha of woodland mix planting, 19 ha of shrubland mix planting and 17.55 ha of grassland will also be compensated, all implemented in phases. Recommended tree and shrub species are detailed in section 8.6.3.1. The future maintenance parties are mentioned in section 8.6.3.2.

To ensure the survival and establishment of the compensatory planting, a 10 year ecological monitoring is proposed, i.e. 2021-2031. Apart from the standard practices and regular maintenance covered by the landscape contract, monitoring of survival, height, and health condition of species planted will be monitored. Detail requirements will be given in the EM&A manual. The requirement of the 10 year ecological monitoring scheme will be specified in the NENT Landfill Extension Contract and will be implemented by the DBO Contractor.

Accidental Leakage of Leachate and Landfill Gas

As mentioned above, leachate collection facilities and the two layers of impermeable barriers would effectively prevent water quality impacts. Monitoring during landfill operation and after use phase would verify the expected conditions. There would also be contingency plans for the accidental leakage of leachate and landfill gas.

The NENT Landfill Extension will be designed as a containment landfill with LFG collection and management systems to eliminate any off-site migration of LFG. The LFG risk assessment in Section 7.4.5 has identified that the overall risk level of LFG hazards to receivers outside the landfill extension site, which include Tong To Shan Tsuen inside Lin Ma Hang stream catchment, is categorised as “Medium” (Category C), and there will be “semi-active” or enhanced passive gas controls and detection system for the receivers. Future landfill liner, leachate collection and treatment system, LFG control devices, landfill cap design will be designed with reference to the specifications of the existing NENT Landfill which is successful in LFG control throughout the years. Furthermore, the design of suitable level of contingency plans for the potential receivers will be incorporated. An Emergency and Contingency Plan will be devised by the DBO Contractor for implementation of appropriate actions in case any LFG migration detected. Such measures include those currently being adopted in the existing NENT Landfill, e.g. installation of double layer liner, LFG extraction/collection/treatment/export systems, gas sensors, increasing monitoring frequency, connecting the affected monitoring point to the Landfill Gas Extraction System, passive venting of landfill gas, active extraction and flaring of landfill gas, and installation of additional barriers to gas movement. etc. The existing NENT Landfill has been incorporated an efficient and effective LFG management system, in which a coordinated approach to LFG monitoring, collection, extraction, flaring and utilization is being implemented to achieve the elimination of the hazards to flora and fauna due to toxicity or asphyxiation effect of LFG presence external to the landfill site. The records of the compliance of LFG monitoring has proven the success of this LFG management system, and the protection of wildlife outside the NENT Landfill extension is thus guaranteed.

The potential impacts from accidental leakage of leachate on Lin Ma Hang Stream and its catchment and associated woodland habitats are avoided through the complete avoidance of Lin Ma Hang catchment by the current landfill extension option (i.e. Option 4, see Chapter 2). Furthermore, a contingency plan on accidental leakage of leachate, which is based upon the current contingency plan of the existing NENT Landfill and modified for the landfill extension, will be adopted to further protect other streams inside the same catchment of the landfill extension such as Ping Yuen River. The future monitoring programme will include surface and groundwater monitoring within and around the site. In the event that the water quality requirements are exceeded, Corrective Action Programmes will be implemented which include surface water/groundwater extraction and treatment prior to discharge, groundwater interception and diversion, installation of additional groundwater well for monitoring and for extraction of contaminated groundwater for treatment, increased frequency of ground-water quality testing, installation of subsurface barriers, changes of working methods, diversion, etc. Contingency plan on accidental leakage of leachate has been detailed in Section 5.8.2.1.

Though the potential risk is extremely low, with the contingency plans for the accidental leakage of leachate and landfill gas in place, the water quality of nearby natural streams (including Lin Ma Hang Stream), associated aquatic life, and other wildlife will be further protected.

10.10 Residual Ecological Impacts

The residual impact to terrestrial fauna from this Project will be the time-lag between the site clearance (habitat destruction) and compensatory plantation becomes old enough to provide habitats to wildlife. The terrestrial fauna recorded within the Project area were habitat generalists and can utilise habitats other woodlands, the residual impact due to a time-lag of 10-12 years will be acceptable.

To further minimise the residual impacts, advance compensatory planting should be considered. While there will be no room for advance planting on site, it is noted that the existing landfill operation will be completed shortly, and the afteruse design is underway. It is therefore recommended that the project proponent would liaise with the contractor of the existing NENT Landfill on the possibility of including some woodland planting in the restoration phase of the existing landfill, for example, advanced planting of 4 ha of woodland to compensate for the loss. The plant mix schedule proposed for the current EIA can also be adopted for the restoration of existing landfill. If implementable, advance compensatory planting can offset the time-lag effect of the NENT Landfill Extension Project. It is anticipated that the proponent can get the agreement in principle with the landfill operator for advance planting during detailed design stage.

With the implementation of the above mitigation measures, the residual impacts are considered minimal and acceptable.

10.11 Ecological Monitoring and Audits

Survival and growth of the compensatory woodland planting will require long term monitoring (at least for two years after the completion of planting programme under the landscape contract and 10 years for ecological monitoring) and should be specified in the planting and maintenance contract and the EM&A manual.

10.12 Conclusion

The NENT Landfill Extension consists of the existing Stockpile and Borrow Area and haul road of NENT Landfill. It covers 0.12 ha of abandoned agriculture land, 47.64 ha of grassland with low shrub, 4.01 ha of natural woodland, 4.76 ha of plantation, 6.89 ha of urbanised/disturbed land, and 2,530m of stream/channel habitats and its associated flora and fauna. In fact, the selected layout (Option 4) is one of the options that enable the NENT Landfill Extension to avoid Lin Ma Hang Stream and its catchment completely. The existing grassland and woodland are largely disturbed by the construction activities in the existing Stockpile and Borrow Area. The overall ecological impacts are ranked as moderate and would be mitigated by transplantation of species of conservation interest, compensatory planting and good site practice.

Potential ecological impacts caused by LFG and leachate are considered as minor. With adoption of the proposed leachate and landfill gas collection facilities and contingency plans, no residual impacts are anticipated.

Upon completion of operation, the landfill site would be restored by planting of woodland, shrubland and grassland species, and the surface flow of Ping Yuen River would be restored. No adverse ecological impact to the surrounding terrestrial and aquatic habitats and their associated flora and fauna is anticipated.

10.13 Reference

Ades, G.W.J. 1994. A Comparative Ecological Study of Insectivorous Bats (Hipposideridae, Vespertilionidae and Rhinolophidae) in Hong Kong, with special reference to Dietary Seasonality. PhD Thesis of University of Hong Kong.

Ades, G.W.J. 1999. The species composition, distribution and population size of Hong Kong bats. Memoirs of Hong Kong Natural History Society 22:183–209.

Ades, G. and Reels, G. 1998. Special feature: focus on farmland – bats. Porcupine! 18: 23-24.

Agriculture, Fisheries and Conservation Department. 2002. Checklist of Hong Kong Plants 2001. Dong Sheng Printing Co., Guangzhou.

Agriculture, Fisheries and Conservation Department. 2004. Field Guide to the Freshwater Fish of Hong Kong.

Bascombe, M.J., Johnston, G. and Bascombe, F.S. 1999. The Butterflies of Hong Kong. Academic Press, London.

Black & Veatch Hong Kong Limited. 2005. Agreement No. CE 6/2002 (DS) Drainage Improvement in Northern New Territories – Package C: Investigation, Design and Construction. Environmental Impact Assessment Draft Report. Drainage Services Department, Hong Kong.

BMT Asia Pacific Limited. 2002. NENT Landfill Site Terrestrial Monitoring. Annual Summary Report for the Year 2001. March 2002.

Carey, G. J., Diskin, D.A., Leader, P.J., Cheung, H.F., Lewthwaite, R. W., Chalmers, M. L. and Kennerley, P. R. 1998. Systematic List. Hong Kong Bird Report 1996: 13–87.

Carey, G. J., Kennerley, P. R., Cheung, H. F., Lewthwaite, R. W. and Chalmers, M. L. 1999. Systematic List. Hong Kong Bird Report 1997: 15–91.

Carey, G. J., Diskin, D.A., Lewthwaite, R. W. and Turnbull, M. 2000. Systematic List. Hong Kong Bird Report 1998: 18–95.

Carey, G.J., Chalmers, M.L., Diskin, D.A., Kennerley, P.R., Leader, P.J., Leven, M.R., Lewthwaite, R. W., Melville, D.S., Turnbull, M. and Young, L. 2001. The Avifauna of Hong Kong. Hong Kong Bird Watching Society, Hong Kong.

Chan, P-l, B. 2001. Sustainability and biodiversity : the impact, alternative design and prospects of restoration of channelized lowland streams in Hong Kong. Ph. D Thesis. Hong Kong : University of Hong Kong, 2001.

Corlett, R. T. 2001. Is Javan Mongoose native and does it matter? Porcupine! 24: 19.

Dudgeon, D. and Corlett, R. 1994. Hills and Streams – An Ecology of Hong Kong. Hong Kong University Press, Hong Kong.

Dudgeon, D. and Corlett, R. 2004. The Ecology and Biodiversity of Hong Kong. Friends of the Country Parks & Joint Publishing, Hong Kong.

ERM Limited. 1995. NENT Landfill: Supplementary Environmental Impact Assessment. Submitted to Far East Landfill Technologies. October 1995.

ERM Limited. 1999. Terrestrial Vegetation Monitoring at NENT Landfill – 1998: Annual Monitoring Report. Submitted to Far East Technologies Ltd. 26 February 1999.

Fellows

Karsen, S.J., Lau, M.W.N. and Bogadek, A. 1998. Hong Kong Amphibians and Reptiles. Urban Council, Hong Kong.

Kendrick, R.C. 1998. Special feature: focus on farmland – insects. Porcupine! 18: 24.

Kwok, H.K. and Dahmer, T.D. 2002. Bird community on hill fire maintained grassland. Memoirs of the Hong Kong Natural History Society 25: 111-116.

Scott Wilson Limited. 2003. Agreement No. CE45/99. Extension of Existing Landfills and Identification of Potential Waste Disposal Sites. Final Strategic Environmental Assessment Report Volume I and II). Submitted to Environmental Protection Department. January 2003.

Shek, C.T. 2004. Bats of Hong Kong: An Introduction of Hong Kong Bats, with an Illustrative Identification Key. Hong Kong Biodiversity 7: 1-9.

Shek, C.T. and Chan, C.S.M. 2005. Roost censuses of cave dwelling bats of Hong Kong. Hong Kong Biodiversity 10: 1-8.

Shek, C.T. and Chan, C.S.M. 2006. Mist net survey of bats with three new bat species recorded for Hong Kong. Hong Kong Biodiversity 11: 1-7.

Siu, G. L-p. 2000. Orchidaceae of Hong Kong. Memoirs of the Hong Kong Natural History Society. 23: 137-148.

Thrower, S.L. 1984. Hong Kong Country Parks. Government Printer, Hong Kong.

Turnbull, M., Carey, G.J., Lewthwaite, R.W., Yu, Y.T., Kilburn, E.M.S. and Leader, P.J. 2004. Systematic List. Hong Kong Bird Report 1999/2000: 29–180.

Viney, C., Phillipps, K. & Lam, C. Y. 2005. Birds of Hong Kong and South China. Government Printer, Hong Kong.

Wilson, K.D.P. 2004. Field Guide to the Dragonflies of Hong Kong. Agriculture, Fisheries and Conservation Department, Hong Kong.

Xing, F.W., Ng, S.C., Chau, L.K.C. 2000. Gymnosperms and angiosperms of Hong Kong. Memoirs of the Hong Kong Natural History Society. 23: 21-136.

Yiu, V. 2004. Field Guide to Butterfly Watching in Hong Kong. Hong Kong Lepidopterist’s Society, Hong Kong.

Zhang Yongzu et al. 1997. Distribution of mammalian species in China. China Forestry Publishing House, Beijing, 280pp.

Zhao, E.M. 1998. China Red Data Book of Endangered Animals: Amphibia & Reptilia. Science Press, Beijing.

Zheng, G.M. and Wang, Q. S. 1998. China Red Data Book of Endangered Animals: Aves. Science Press, Beijing.

11 Summary of Environmental Outcome

11.1 Population and Environmental Sensitive Areas Protected

The entire population of the affected villages in the vicinity of the Project site are effectively protected by the measures proposed by this EIA study.

By adopting a design with no encroachment on the ecologically sensitive areas, the habitats of ecological importance around the site including Lin Ma Hang natural woodland, Lin Ma Hang Stream and its catchment are completely protected.

11.2 Environmental Friendly Design and Benefit

Environmental friendly design and benefit adopted in this EIA study are summarised below:

· The layout of the NENT Landfill Extension was chosen such that the void space of the landfill could be optimised without encroaching on the catchment of Lin Ma Hang

· A bentonite conductivity of 10^-9m/s was proposed for the liner system of the NENT Landfill Extension to protect the qualities of surface water and groundwater around the site.

· A comprehensive leachate collection, monitoring, interception and diversion system will be provided for the Landfill Extension

· A comprehensive surface water management system including erosion control, dry weather flow interceptor, sedimentation tank, etc. will be provided for the Landfill Extension.

· To compensate for the loss of existing trees on the Project site, 26.83 ha (43% of the site) will be planted with woodland mix progressively in phases. There will be about 148,100 trees planted. In addition, 19 ha of shrubland mix planting and 17.55 ha of grassland are proposed.

11.3 Key Environmental Problem Avoided

Potential ecological and water quality impacts on Lin Ma Hang Stream, Lin Ma Hang Lead Mines SSSI and Robin’s Nest have been avoided by adopting a layout with no encroachment on these sensitive areas.

11.4 Environmental Protection Measures and Precautionary Measures

Precautionary measures and good site practices were recommended throughout the impact assessments of air quality, noise, water quality, waste management, landfill gas hazard, landscape and visual, and ecology. These measures were consolidated in an Implementation Schedule which specifies the responsibility, methodology and timing of implementation, such that effective and appropriate implementation of the measures can be assured.

12 Environmental Monitoring and Audit Requirements

12.1 Introduction

This section provides descriptions of the environmental and operational variables and parameters to be monitored, and the purpose for which each should be monitored, e.g. as an indication of general background conditions or as an indicator of unacceptable environmental impact.

In accordance with the requirements as stipulated in Annex 21 of the TM-EIAO, it is considered necessary to conduct the Environmental Monitoring and Audit (EM&A) programme during the construction, operation, restoration and aftercare phases of the Project and to define the relevant scope of EM&A requirements, including:

· Provision of a database against which to determine any short- or long-term environmental impacts of the landfill extension;

· Confirmation of the validity of any assumptions made in the design of landfill extension;

· Provision of an early indication that any of the environmental control measures or other operational practices are failing to achieve the required standards;

· Provision of data to determine the effectiveness of any mitigation or control measures implemented through amendments in procedures during the life of landfill;

· Provision of data to enable an environmental audit of the construction, operation, resotration and aftercare works to be undertaken; and

· Assessment of compliance with the environmental and pollution control and operational requirements.

12.2 Project Organisation

A project organisation consisting of the Independent Consultant (IC), Independent Environmental Checker (IEC), Environmental Team (ET), Project Proponent (EPD) and DBO Contractor should be established to take on the responsibilities for environmental protection for the NENT Landfill Extension Project. The IEC will be appointed by the Project Proponent to conduct independent auditing on the overall EM&A programme including environmental and operation monitoring, implementation of mitigation measures, EM&A submissions, and any other submission required under the Environmental Permit (EP). The organisation, responsibilities of respective parties and lines of communication with respect to environmental protection works are given in the EM&A Manual.

12.3 EM&A Manual and Implementation Schedule

EM&A is an important aspect in the EIA process which specifies the timeframe and responsibilities for the implementation of environmental mitigation measures. The requirements on environmental monitoring (including baseline and impact monitoring) are given in the EM&A Manual.

A project specific EM&A Manual to the NENT Landfill Extension was prepared with reference to the latest design information available and EPD’s generic EM&A Manual. The project specific EM&A Manual highlights the following issues:

· Organisation, hierarchy and responsibilities of the DBO Contractor, Project Proponent, ET, IEC and IC with respect to the EM&A requirements during construction, operation, restoration and aftercare phases of the landfill extension;

· Information on project organisation and programming of construction activities;

· Requirements with respect to the construction schedule and necessary EM&A programme to track the varying environmental impacts;

· Full details of methodologies to be adopted, including all field, laboratory and analytical procedures, and details on quality assurance;

· Procedure for undertaking on-site environmental audits;

· Definition of Action and Limit Levels;

· Establishment of Event and Action Plans;

· Requirements of reviewing pollution sources and working procedures required in the event of non-compliance of environmental criteria and complaints;

· Requirements for reviewing the EIA predictions, implementation of mitigation measures, and effectiveness of environmental protection and pollution control measures adopted; and

· Presentation of requirements for EM&A data and appropriate reporting procedures.

An Environmental Mitigation Implementation Schedule (EMIS) has been prepared and included in the EM&A manual to summarise all the required mitigation measures need to be implemented during the construction, operation, restoration and aftercare phases of the landfill extension. The implementation responsibilities are also identified in the EMIS which is also included in the EM&A Manual for submission to EPD.

The DBO Contractor should review the mitigation measures and EMIS with respect to the design developments and construction methodology. In case the DBO Contractor needs to update the mitigation measures and EMIS, the EM&A Manual should be updated accordingly. The DBO Contractor should seek EPD’s prior approval on these amendments before construction commences.

12.4 EM&A Programme

Detailed requirements of the EM&A programme are described in the EM&A Manual. Measurements and activities are summarised as follows:

· Baseline monitoring on groundwater, surface water, dust, ambient emissions of odour, VOC and ammonia, and ecology (flora and fauna);

· Impact monitoring on leachate, LFG, groundwater, surface water, dust, ambient emissions of odour, VOC and ammonia, meteorological data, volume and density of waste, settlement, waste type, and ecology (flora and fauna);

· Remedial actions in accordance with the Event and Action Plan within the timeframe in cases the specified criteria in the EM&A Manual were exceeded;

· Logging and keeping records of monitoring results; and

· Preparation and submission of Monthly, Quarterly and Annual EM&A Reports.

12.5 Method Statements

The environmental aspects of working methods should be controlled through checking of the DBO Contractor’s method statements which should be submitted and approved by the IEC prior to the works commence. The Project Proponent should specify an arrangement whereby the method statements would be scrutinised and signed off by the IEC before approval.

13 3-Dimensional EIA

In order to facilitate Continuous Public Involvement (CPI), a web-site www.nent-ext.com has been developed for the presentation of 3-D Environmental Impact Assessment Public Engagement Tools which aims to facilitate awareness of the development proposals and promote greater public participation in the decision making process. All the EIA findings and mitigation measures have been presented in the form of 3D EIA animation. The public can make use of the 3D EIA public engagement tools to offer suggestions, innovative solutions, alternative options and mitigation measures. Consensus can be developed through this re-iterative information exchange, engagement and informed dialogue process offered by the tools.

14 Conclusion

This EIA Report has provided an assessment of the potential environmental impacts associated with the construction, operation, restoration and aftercare phases of the Project.

Baseline conditions, sensitive receivers, potential environmental impacts, mitigation measures and EM&A requirements were identified and assessed throughout the course of the EIA study. The recommended mitigation/precautionary measures are summarised in an Implementation Schedule for further enforcement.

14.1 Option Evaluation

Four layout options for the NENT Landfill Extension with different footprints were considered during the option evaluation stage. After detailed evaluation of engineering aspects, environmental issues and community responses, Option 4 for developing the NENT Landfill Extension was adopted.

14.2 Air Quality Impact

The potential air quality impacts during construction, operation, restoration and aftercare phases of the Project have been assessed.

14.2.1 Construction Phase

Construction dust modelling results show that there would be no adverse construction dust impact on the ASRs in the vicinity of the Project site. Good site practices, however, are still recommended throughout the construction period to further eliminate any dust problem. Requirements for regular monitoring of dust concentration are detailed in the EM&A Manual.

14.2.2 Operation Phase

14.2.2.1 Stack Gas Emission

Dispersion modelling results show that gaseous emissions from ammonia stripping plant, LFG power generator and flaring system of the NENT Landfill Extension will have no adverse impact on the ASRs throughout the operational period of the Project. The maximum allowable discharge limits from the above facilities should be specified in contract specifications to control the air emissions. Regular emission monitoring of these facilities is recommended to ensure their proper functioning.

14.2.2.2 Odour

14.2.3 Restoration and Aftercare Phases

The scale of construction activities during the restoration and aftercare phases of the Project would be smaller when compared with its construction phase. Construction dust is therefore not an issue.

The impact of stack gas emissions from treatment facilities will be much reduced during these phases given the gradual reduction in leachate and LFG generation rates over time. The air quality conditions would not be worse than the operation phase and hence no adverse impact is anticipated.

14.3 Noise Impact

The potential noise impacts during construction, operation, restoration and aftercare phases of the Project have been assessed.

14.3.1 Construction and Restoration Phase

Potential construction noise impacts are likely caused by various construction activities on site, such as, site clearance and formation, soil excavation, installation of lining system, construction of leachate treatment facilities, installation of final capping system, etc.

Construction noise assessment concluded that the construction noise levels at the neighbouring NSRs will comply with the relevant noise criteria even without any mitigation measures in place. No adverse construction noise impact is therefore anticipated during the construction and restoration phases.

14.3.2 Operation Phase

Potential noise impact during the operation phase of the Project include road traffic noise along Wo Keng Shan Road, which is the major access to the NENT Landfill Extension site, and on-site noise from leachate treatment facilities (including aeration lagoon and ammonia stripping plant) and daily landfill operations (e.g. vehicular movements, waste filling, waste compacting, etc.)

Assessment results show that the predicted operational noise levels at the NSRs will be within the relevant noise criteria. No adverse noise impact is anticipated during this phase.

14.3.3 Aftercare Phase

No adverse noise impact is anticipated during the aftercare phase given the minimal amount of site activities involved during this period.

14.4 Water Quality

The potential water quality and hydrological impacts during construction, operation, restoration and aftercare phases of the Project have been assessed. No overflow or discharge of raw leachate, treated leachate and contaminated surface runoff from the tipping face to Ping Yuen River and its tributaries will be allowed under any circumstances.

14.4.1 Construction and Restoration Phases

With proper implementation of construction site runoff control measures, adverse water quality impact during construction and restoration phases is not anticipated.

14.4.2 Operation and Aftercare Phases

Under normal installation and operation conditions, the rate of leachate seepage due to manufacturing defects of geomembrane is assessed to be negligible and would have minimal impact on groundwater quality.

In case of accidental leakage of leachate due to rupture or damage of lining and/or leachate collection system, the impact on surface water and groundwater quality will be limited and temporary with the implementation of remedial measures proposed in the contingency plan.

Assessment results show that the groundwater level underneath the site may potentially drop by 1.5m over the operational lifetime of the NENT Landfill Extension. Groundwater levels at Wo Keng Shan and Ping Yuen could fall by 1m and 0.6m respectively, which are considered to be minimal. The groundwater system will be recharged by adjacent catchments and a number of measures to mitigate the potential loss of groundwater yield have been proposed.

The maximum cumulative amount of leachate generated from both the existing and the extension of NENT Landfill was estimated to be 1,500 m³/day under extreme meteorological conditions. Options for catering the surplus amount of leachate, including building new storage lagoons and constructing a new leachate treatment facility, have been considered. It should be noted that under normal meteorological conditions the total leachate generation rate from both landfills will be 1,190m³/day, which is still within the allowable capacity of the discharge license. No adverse impact on DSD’s sewerage network downstream is anticipated.

14.5 Waste Management

The waste management implications during construction, operation, restoration and aftercare phases of the Project have been assessed.

14.5.1 Construction and Operation Phases

During the construction and operation phases of the Project, a variety of waste including excavated construction materials, chemical waste, general refuse and sludge from leachate treatment facilities will be generated. The quality, quantity and timing of waste arising have been assessed. By adopting a construction material balance approach, and with the implementation of proper management practice, no adverse environmental impact arising from waste management is anticipated.

14.5.2 Restoration and Aftercare Phases

During the 30-year restoration and aftercare period, chemical waste, sludge and general refuse will be the major waste sources anticipated. The quantities of waste arising have been estimated. With the proper handling of waste arising, no adverse environmental impact is anticipated.

14.6 Landfill Gas Hazards

The results of this qualitative risk assessment for LFG hazards associated with the construction, operation, restoration and aftercare phases indicate that the overall risks to the receivers within the NENT Landfill Extension site would be categorised as ‘High’ and that to the receivers outside the NENT Landfill Extension site would be ‘Medium’. The sensitive receivers falling within the newly proposed 250 m consultation zone shall be prone to LFG potential risk and appropriate protective and precautionary measures including engineering design and monitoring programme have been proposed to reduce such risk to acceptable levels. With these measures in place, no adverse impact would be anticipated.

14.7 Landscape and Visual Impact

The Project site of the Landfill Extension is mainly made up largely by the SBA and haul roads of the existing NENT Landfill Site. Furthermore, the existing NENT Landfill Site is located immediately adjoining to the northwest of the proposed extension. It is noted the existing landscape resources and characters of the Project site have already been largely deteriorated by the SBA of the existing landfill site.

In terms of residual landscape impact, it is concluded that with implementation of mitigation measures, the proposed development will have slight impact to the upland landscape at the northwest facing slope of Wo Keng Shan (LCA3C) and moderate impact to rural settlement landscape of Tong To Shan Tsuen & Ngong Tong (LCA2A). Furthermore, it is assessed that there will be slight to moderate residual impact to the woodland (LR1) and slight residual impact to shrubland (LR2) and grassland (LR3) within the Project site. The loss of 1.5 ha of existing woodland and 5.8 ha of shrubland will be compensated by 26.83 ha (about 43% of the Project site area) of woodland mix progressively planted in phases with about 148,100 nos. of tree seedlings/ whips. In addition, 19 ha of shrubland mix planting and 17.55 ha of grassland will be created in the restoration phase.

Due to their proximity, the existing landfill site, its SBA and the proposed extension will affect the similar group of visual sensitive receivers. It is noted that the landscape character of the Project site will be similar to that of the existing landfill site and its associated SBA. In terms of residual visual impact, the proposed development will have slight impact to the majority of the identified visual sensitive receivers. Moderate to significant impact is expected to Hikers at the top of Robin’s Nest (VSR 9), whereas moderate impact is expected to visual sensitive receivers at Lin Ma Hang (VSR 2) and to potential future users at the existing NENT Landfill site during its aftercare period. (VSR12).

The proposed landfill extension will be restored and vegetated to match with its surrounding landform and vegetation patterns in the restoration and aftercare phases. In summary, the overall landscape and visual impact of the Project is acceptable with mitigation measures implemented.

14.8 Cultural Heritage Impact

14.8.1 Archaeology

14.8.2 Built Heritage

A number of resources will be directly impacted by the Project; these consist of 13 graves (G2, G4, G5, G6, G7, G8, G14, G15, G25, G26, G27, G29 and G30) and 1 boulder path (BP2). A second boulder path (BP1) will have to be surveyed to determine its exact relationship to the extension area and hence the nature of any impacts. Mitigation in the form of preservation by record for all of the resources will be required. It is the responsibility of the DBO Contractor to ensure that the recording has been carried out by a qualified professional and that a report has been submitted to and approved by AMO prior to the commencement of any excavation works.

14.9 Ecological Impact

14.9.1 Construction and landfill Operation Phase

The construction works of the preferred option would cause a loss of 0.12 ha of abandoned agriculture land, 47.64 ha of grassland with low shrub, 4.01 ha of natural woodland, 4.76 ha of plantation, 6.89 ha of urbanised/disturbed, and 2530 m of stream/channel habitats. In fact, the selected layout enables the NENT Landfill Extension to avoid Lin Ma Hang Stream and its catchment completely. With the implementation of the mitigation measures including compensatory planting, the residual impacts are considered minimal and acceptable.

Potential ecological impacts caused by landfill gas and leachate are ranked as minor. With adoption of the proposed leachate and landfill gas collection facilities and contingency plans, no residual impacts are anticipated.

14.9.2 Restoration Phase

Upon completion of operation, the landfill site would be restored by planting of woodland, shrubland and grassland species, and the surface flow of Ping Yuen River would be restored to comparable level. No adverse ecological impact to the surrounding terrestrial and aquatic habitats and their associated flora and fauna is anticipated.

14.10 Environmental Monitoring and Audit

Details of the EM&A programme and monitoring requirements are described in the EM&A Manual. The following measurements and activities have been included:

· Baseline monitoring on groundwater, surface water, dust, ambient emissions of odour, VOC and ammonia, and ecology (flora and fauna);

· Remedial actions in accordance with the Event and Action Plan within the timeframe in cases the specified criteria in the EM&A Manual are exceeded;

· Logging and keeping records of monitoring results; and

· Preparation and submission of Monthly, Quarterly and Annual EM&A Reports

14.11 3D-EIA Tools

14.12 Overall Conclusion

An EIA Report has been prepared to satisfy the requirements given in the EIA Study Brief No.: ESB-114/2004 and the TM-EIAO. All the latest design information has been incorporated into the EIA process. Aspects that have been considered in this EIA Report include:

· Layout option evaluation

· Description of construction, operation and aftercare activities

· Air Quality Impact

· Noise Impact

· Water Quality Impact

· Waste Management Implications

· Landfill Gas Hazards

· Landscape and Visual Impact

· Impact on Cultural Heritage

· Ecological Impact

· Environmental Monitoring and Audit

· 3D EIA

Overall, the EIA Report has predicted that the Project would be environmentally acceptable with the implementation of the proposed mitigation measures for construction and operation phases. An environmental monitoring and audit programme has been recommended to ensure the effectiveness of recommended mitigation measures.