Table of contents

 

9        Waste Management implications & Land contamination.. 9-1

9.1         Introduction. 9-1

9.2         Relevant Legislations, Standards & Guidelines. 9-1

9.3         Assessment Methodology. 9-5

9.4         Estimation of Construction Waste Generation and Evaluation of Impact (Land-based Works) 9-5

9.5         Estimation of Construction Waste Generation and Evaluation of Impact (Marine-based Works) 9-9

9.6         Land Contamination. 9-10

9.7         Estimation of Operational Phase Waste Generation and Evaluation of Impact 9-12

9.8         Mitigation Measures. 9-13

9.9         Residual Impact 9-16

9.10       Environmental Monitoring and Audit 9-16

9.11       Conclusion. 9-17

 

 

 

9               WASTE MANAGEMENT IMPLICATIONS & LAND CONTAMINATION

9.1              Introduction

9.1.1        This Chapter identifies the types of wastes that are likely to be generated during the construction and operation of the Project, and evaluates the potential environmental impacts that may result from these wastes. 

9.2              Relevant Legislations, Standards & Guidelines

9.2.1        Reference has been made to the following Ordinances and Regulations which are relevant to waste management and disposal:

·           The Waste Disposal Ordinance (Cap. 354) and subsidiary legislation such as the Waste Disposal (Chemical Waste) (General) Regulation and Waste Disposal (Charges for Disposal of Construction Waste) Regulation that set out requirements for the storage, handling and transportation of all types of wastes.

·           Environmental Impact Assessment Ordinance (Cap. 499), Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), Annexes 7 and 15;

·           Public Health and Municipal Services Ordinance (Cap. 132) – Public Cleansing and Prevention of Nuisance Regulation – control of disposal of general refuse;

·           Land (Miscellaneous Provisions) Ordinance (Cap. 28); and

·           Dumping at Sea Ordinance (Cap. 466).

9.2.2        Other relevant documents and guidelines are applicable to waste management and disposal in Hong Kong include:

·           Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes (1992);

·           Development Bureau Technical Circular (Works) (TC(W)) No. 6/2010, Trip Ticket System for Disposal of Construction & Demolition Materials;

·           Development Bureau TC(W) No. 8/2010 Enhanced Specification for Site Cleanliness and Tidiness;

·           ETWB TC(W) No. 34/2002, Management of Dredged / Excavated Sediment;

·           ETWB TC(W) Nos. 22/2003 and 22/2003A, Additional Measures to Improve Site Cleanliness and Control Mosquito Breeding on Construction Sites;

·           ETWB TC(W) No. 19/2005, Environmental Management on Construction Sites;

·           Project Administration Handbook for Civil Engineering Works, 2014 Edition Section 4.1.3, Management of Construction and Demolition Material Including Rock;

·           Works Bureau TC No. 2/93, Public Dumps;

·           Works Bureau TC No. 2/93B, Public Filling Facilities; and

·           Works Bureau TC Nos. 25/99, 25/99A and 25/99C, Incorporation of Information on Construction and Demolition Material Management in Public Works Sub-committee Papers.

9.2.3        Legislations and guidelines related to land contamination are given below:

·           Environmental Impact Assessment Ordinance (Cap. 499), Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), Annex 19;

·           Waste Disposal (Chemical Waste) (General) Regulation (Cap 354C)

·           Dangerous Goods Ordinance (Cap 295)

·           Practice Guide for Investigation and Remediation of Contaminated Land;

·           Guidance Note for Contaminated Land Assessment and Remediation; and

·           Guidance Manual for Use of Risk-Based Remediation Goals (RBRGs) for Contaminated Land Management.

Waste Management

9.2.4        The Waste Disposal Ordinance (WDO) prohibits unauthorised disposal of wastes.  Construction waste is defined as any substance, matter or thing that is generated from construction work and abandoned, whether or not it has been processed or stockpiled before being abandoned, but does not include any sludge, screenings or matter removed in or generated from any desludging, desilting or dredging works.  Under the WDO, wastes can be disposed of only at designated waste disposal facilities.

9.2.5        Under the WDO, the Chemical Waste (General) Regulation 1992 provides regulations for chemical waste control, and administers the possession, storage, collection, transport and disposal of chemical waste.  EPD has also issued a guideline document, the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes (1992), which details how the contractor should comply with the regulations on chemical waste.

9.2.6        Public Cleansing and Prevention of Nuisance Regulation provides control on illegal tipping of wastes on unauthorised (unlicensed) sites. 

9.2.7        The Land (Miscellaneous Provisions) Ordinance provides control on dumping of public fill.  The inert portion of construction waste (also called public fill) may be taken to public fill reception facilities which are operated by the Civil Engineering and Development Department (CEDD).  The Land (Miscellaneous Provisions) Ordinance requires that dumping licences be obtained by individuals or companies who deliver public fill to public filling areas.  The CEDD issues the licences under delegated powers from the Director of Lands.

9.2.8        Under the licence conditions, public fill reception facilities will only accept inert earth, soil, sand, rock, boulder, rubble, brick, tile, concrete, asphalt, masonry or used bentonite.  In addition, in accordance with Development Bureau Technical Circular (Works) (TC(W)) No. 6/2010, the Public Fill Committee will advise on the acceptance criteria (e.g. no mixing of construction waste, nominal size of the materials less than 250mm, etc.) for disposal of construction and demolition (C&D) materials at public fill facilities.

Construction and Demolition (C&D) Material

9.2.9        The current policy related to the disposal of C&D materials is documented in the Works Branch TC No. 2/93, ‘Public Dumps’. C&D materials that are wholly inert, namely public fill, should not be disposed of to landfill, but should be taken to public filling areas for reuse. 

9.2.10    Under the Waste Disposal (Charges for Disposal of Construction Waste) Regulation, enacted in January 2006, construction waste delivered to a landfill for disposal must not contain more than 50% by weight of inert material.  Construction waste delivered to a sorting facility for disposal must contain more than 50% by weight of inert material, and construction waste delivered to a public fill reception facility for disposal must consist entirely of inert materials.

9.2.11    The ETWB TC(W) No. 19/2005 “Environmental Management on Construction Sites” includes procedures on waste management requiring contractors to reduce the C&D materials to be disposed of during the course of construction. The Project Administration Handbook for Civil Engineering Works, 2014 Edition Section 4.1.3, “Management of Construction and Demolition Material Including Rock” to enhance the management of C&D materials, and to minimize its generation at source, submission of C&D Materials Management Plan (C&DMMP) is not required for less than 50,000 m3 C&D materials from Designated Projects and less than 300,000 m3 from non-Designated Projects.  Under ETWB TC(W) No. 19/2005, the contractor is required to prepare and implement an Environmental Management Plan (EMP) and the Waste Management Plan becomes part of the EMP.

Chemical Waste

9.2.12    Under the Waste Disposal (Chemical Waste) (General) Regulations, all producers of chemical waste must register with EPD and treat their wastes, either utilising on-site plant licensed by EPD, or arranging for a licensed collector to transport the wastes to a licensed facility.  The regulation also prescribes the storage facilities to be provided on site, including labelling and warning signs, and requires the preparation of written procedures and training to deal with emergencies such as spillages, leakages or accidents arising from the storage of chemical waste.

Marine Sediment

9.2.13    ETWB TC(W) No. 34/2002 Management of Dredged / Excavated Sediment stipulates that marine sediment shall be disposed of at designated dumping ground in accordance to its contamination level. The contamination level of the sediment is classified into three categories (Cat. L, M, H) based on the Chemical Exceedance Levels (CEL) shown in Table 9-1, which determines the disposal method.

Table 9-1:      Sediment Quality Criteria for the Classification of Sediment

Contaminants

Lower Chemical Exceedance Level (LCEL)

Upper Chemical Exceedance Level (UCEL)

Metals (mg/kg dry weight)

Cadmium (Cd)

1.5

4

Chromium (Cr)

80

160

Copper (Cu)

65

110

Mercury (Hg)

0.5

1

Nickel (Ni)*

40

40

Lead (Pb)

75

110

·    Silver (Ag)

1

2

·    Zinc (Zn)

200

270

Metalloid (mg/kg dry weight)

Arsenic

12

42

Organic-PAHs (µg/kg dry weight)

·    Low Molecular Weight PAHs

550

3160

·    High Molecular Weight PAHs

1700

9600

Organic-non-PAHs (µg/kg dry weight)

Total PCBs

23

180

Organometallics (µg-TBT L-1 in interstitial water)

Tributyltin*

0.15

0.15

* The contaminant level is considered to have exceeded the UCEL if it is greater than the value shown.

Category L:

Sediment with all contaminant levels not exceeding the LCEL. The material must be dredged, transported and disposed of in a manner which minimizes the loss of contaminants either into solution or by resuspension.

Category M:

Sediment with any one or more contaminant levels exceeding the LCEL and none exceeding the UCEL.  The material must be dredged and transported with care, and must be effectively isolated from the environment upon final disposal unless appropriate biological tests demonstrate that the material will not adversely affect the marine environment.

Category H:

Sediment with any one or more contaminant levels exceeding the UCEL.  The material must be dredged and transported with great care, and must be effectively isolated from the environment upon final disposal.

9.3              Assessment Methodology

9.3.1         The assessment of potential waste management implications includes the following tasks:

·           Estimation of the types and quantities of waste arising;

·           Evaluation of potential impacts from the handling, collection, transportation and disposal of waste; and

·           Proposal of mitigation measures for the waste management.

9.3.2         In order to identify and evaluate the potential contamination impacts associated with the Project, a desktop study has been conducted to review the current and historical land uses. Site inspections have been carried out to identify any contamination hotspots and the site condition of the industrial operations, if any.

9.3.3         The assessment area covers the work boundary for the proposed sewage treatment plant and proposed pipe alignment.

9.3.4         In addition, the following sources of information have been collected and reviewed:

·           Aerial photographs from Lands Department;

·           Available ground investigation reports

9.4              Estimation of Construction Waste Generation and Evaluation of Impact (Land-based Works)

9.4.1        The top priority is to minimize any waste production. The amount of construction waste has been minimized by designing the sewerage works with minimum land requirement and adopting suitable construction method. As mentioned in Chapter 2 – Project Descriptions, trenchless method will be adopted where pipes have to be laid deep underground. This method involves excavation between two open ends without uncovering the ground above. Trenchless method are capable to reduce the amount of excavated materials when compared with open-cut methods.

9.4.2        The actual amount of construction waste depends upon the practice of the Contractor. The preliminary estimation is shown below.

9.4.3        Referring to the detailed construction method in Chapter 2 – Project Descriptions, major construction waste will be:

·           Construction and demolition materials

·           Chemical waste

·           Bentonite slurry

·           General refuse from workforce

Construction and Demolition Materials (C&D Materials)

9.4.4        C&D materials can be divided into two categories:

                             i.          Inert C&D materials (or public fill), e.g. soil, rock, concrete etc., which could be reused on-site as filling materials or off-site as public fill at public fill reception facilities, and

                           ii.          Non-inert C&D materials (or C&D waste), e.g. timber, paper etc., which should be reused or recycled as far as possible; landfill disposal should be considered as the last resort.

9.4.5        On average, the expected daily production of inert C&D materials (or public fill) is 5.21m3. During construction phase, 7,506m3 waste would be generated, which will comprise the following:

·           Soil and plant materials generated from slope cutting;

·           Soil and rocks from drilling for submarine outfall;

·           Broken concrete from excavation work for pipe laying;

·           Soil from excavation work for pipe laying; and

·           Unused building materials, e.g. cement, concrete.

9.4.6        Rock excavation at sewage treatment plant (STP) and HDD works at rocky shore will generate 4,344m3 of low quality rock, at a rate of 11.9m3 per day.

9.4.7        Approximately 2,430m3 of rocks, broken concrete and soil can be reused for backfilling of excavated trenches after pipe laying. Unused building materials can be used in other construction sites.

9.4.8        Non-inert C&D materials (or C&D waste) from land-based works will be as follows:

·           Plant materials;

·           Metal and timber formwork;

·           Bamboo scaffolding; and

·           Material packaging, e.g. plastic, paper wraps.

9.4.9        A designated area shall be identified during the construction stage for onsite sorting of C&D materials as far as possible. Sorted inert materials shall be sent to a public fill reception facility for beneficial reuse, and the closest public fill reception facility is located at Tseung Kwan O Area 137 Fill Bank. DSD shall enquire with the Public Fill Committee on the availability of public fill reception facility and acceptability of the inert material.

9.4.10    Metal, paper and plastic should be recycled or reused as far as possible. Timber and dismantled bamboo scaffolding should be reused in other projects if the quality remains satisfactory. Non-inert C&D materials (or C&D waste) which are not recyclable or reusable should be disposed of at landfill, and the closest one is South East New Territories Landfill. DSD shall enquire with the Environmental Protection Department on the availability of landfill and acceptability of the waste.

9.4.11    No barging point or conveyor system for waste removal will be adopted.

Chemical Waste

9.4.12    Chemical waste that may arise during the construction of the Po Toi O Sewage Treatment Works (PTOSTW) includes:

·           Paint, solvents and detergents in fabricating the STP;

·           Cleansing fluid, lubricating oil, scrap batteries and fuel in maintaining and powering machinery; and

·           Empty containers of the above substances.

9.4.13    The amount of chemical waste generated will vary between Contractors based on the number of plant equipment to be employed and the maintenance frequency. However, it is expected to be limited (about 1m3 for the whole Project) due to small project scale.

9.4.14    Improper handling of the chemical waste may pose health impact on workers (e.g. accidental ingestion), fire hazard and contamination of soil and water. The Contractor shall register with EPD as a chemical waste producer. All chemical waste shall be delivered to Chemical Waste Treatment Centre in Tsing Yi by licensed collectors for treatment and disposal in strict compliance with the Waste Disposal (Chemical Waste) (General) Regulations.

Bentonite Slurry

9.4.15    Bentonite will be used as drilling liquid during horizontal directional drilling for the proposed submarine outfall. Cutting comprising broken rock and marine sediment will be mixed with bentonite and drawn out of the drilled tunnel. After extraction from bentonite, broken rock will be disposed of as public fill while marine sediment will be removed for marine disposal. Reconditioned bentonite free from cutting will be reused for drilling.

9.4.16    The contractor may consider not to reuse the spent bentonite for whatever reasons. The quantity of bentonite to be disposed of will depend on contractor’s practice. The estimated quantity is 5m3 after completion of the drilling works. The bentonite shall be dewatered before disposal at public fill. Alternative disposal methods are recommended under ProPECC PN 1/94 Construction Site Drainage. Bentonite shall be dumped at marine spoil ground after obtaining a marine dumping license from EPD. For disposal at public drainage system, the bentonite shall be treated up to effluent standards for sewers, storm drains or the receiving waters as set out in the WPCO Technical Memorandum.

General Refuse

9.4.17    General refuse refers to the waste generated by workers during daily operation, e.g. food waste and packaging, metal cans, plastic bottles and office waste. The estimated daily generation is about 0.34m3 and the total quantity for this Project is about 460m3.

9.4.18    Even though the quantity is small, sufficient rubbish bins or collection area should be provided to maintain the hygiene and tidiness of the works site. Otherwise the waste may be blown away by wind or washed into nearby watercourses or sea. In addition to causing pollution problem, this may clog drainage system, resulting in flooding under heavy rain. Littering with rubbish around is also unsightly and may attract pest and bring odour nuisance. Recycle bins should also be provided to encourage recycling for paper, metal and plastic. As the South East New Territories Landfill no longer receive waste other than construction waste, the collected waste shall be removed to Island East Transfer Station at regular interval for final disposal to West New Territories Landfill.

Other Wastes (Human Waste)

9.4.19    Workers can use the public toilet in the middle of Po Toi O Village. Otherwise, chemical toilets should be provided if necessary, which should be maintained regularly by registered waste collectors.

9.4.20    With implementation of mitigation measures in Section 9.8, waste management impact due to handling, collection, transportation and disposal of C&D materials, chemical waste and general refuse is expected to be acceptable.

Table 9-2:       Summary of Land-based Waste

Type of Waste

Quantity
(approx. m3)

Handling and

Disposal Options

Potential Route

Reuse

On-site

Dispose

Off-site

Total

1.   C&D Materials (Total)

2430

5412

7842

A portion of inert C&D materials (or public fill) will be reused on-site for backfilling.

Inert C&D materials (or public fill) which cannot be reused on-site will be disposed to Tseung Kwan O Area 137 Fill Bank.

Po Toi O Chuen Road à Clearwater Bay Road à Wan Po Road à Tseung Kwan O Area 137 Fill Bank

(About 1-2 truck trips/day)

·  Inert C&D Materials

(excavated soil)

1840

1032

2872

·  Inert C&D Materials

(low quality rock)

300

4044

4344

·  Inert C&D Materials
 (broken concrete pavement)

290

0

290

·  Non-inert C&D Materials
(excluding marine sediment)

0

336

336

To be disposed of at landfill (the closest landfill is South East New Territories Landfill (SENT))

Po Toi O Chuen Road à Clearwater Bay Road à Wan Po Road à SENT

(About 1 truck trip/day)

2.   Chemical Waste

0

1

1

To be disposed to Chemical Waste Treatment Centre (CWTC)

Po Toi O Chuen Road à Clearwater Bay Road à Lung Cheung Road à Ching Cheung Road à Tsing Kwai Highway à Tsing Yi Road à CWTC

(Dispose when required)

3.   General Refuse

0

460

460

To be sent to Island East Transfer Station (IETS) for compaction, containerization and dispose at West New Territories Landfill.

Po Toi O Chuen Road à Clearwater Bay Road à Tsueng Kwan O Road à Eastern Harbour Crossing à Island Eastern Corridor à IETS

(About 1 truck trip/day)

9.5              Estimation of Construction Waste Generation and Evaluation of Impact (Marine-based Works)

9.5.1         Dredging will be involved in diffuser installation at the mouth of Po Toi O bay.  According to EPD Marine Water Quality Report 2013, the sediment quality of the station PS6 in Outer Port Shelter (see Figure 9-1) is within Lower Chemical Exceedance Level (LCWL) as shown in Table 9-3 below.

Table 9-3:       Sediment Quality at Station PS6

Contaminants

PS6

Lower Chemical
Exceedance Level (LCEL)

Metals (mg/kg in dry weight)

Cd

<0.1

1.5

Cr

24

80

Cu

11

65

Pb

30

40

Hg

<0.05

0.5

Ni

18

40

Ag

<0.2

1

Zn

64

200

Metalloid (mg/kg in dry weight)

As

5.9

12

Organic-non-PAHs (µg /kg in dry weight)

PCBs

18

23

Organic-PAHs (µg /kg in dry weight)

Low Molecular Weight PAHs

98

550

High Molecular Weight PAHs

32

1700

9.5.2         As part of site investigation conducted in 2015, sediment samples were collected at the proposed diffuser location and its vicinity (SD1 and SD2) as shown in Figure 9-2. Sediment was collected by vibrocoring down to the proposed dredging depth (4m). Samples were collected at 4 depths (i.e. 0 – 0.9m, 0.9 – 1.9m, 1.9 – 2.9m and 3.0 – 3.9m below seabed) at each station. Chemical testing revealed that all samples belonged to Category L according to ETWB TC(W) No. 34/2002 Management of Dredged/Excavated Sediment.

9.5.3         For fulfilment of Section 3(i) of the Study Brief, Sediment Sampling and Testing Plan (SSTP) has been submitted to EPD for agreement prior to commencement of the tests for this EIA Study. This plan details the ranges of parameters to be analysed; the number, type and methods of sampling; sample preservation; chemical and biological laboratory test methods to be used.

9.5.4         The SSTP was approved by EPD on 4 January 2016 and sediment sampling was conducted on 19 February 2016. Since the expected contamination level of the sediment from the Project is low, sampling was proposed within a 200m ´ 200m grid for Tier II analysis. As the dredging work is highly localized within 50m ´ 10m cofferdam, one sediment sampling station (SD3) was set near the proposed diffuser location as shown in Figure 9-2. Surface sediment was collected by grab sampling and then sent to a HOKLAS laboratory for testing. The sediment sample was also confirmed to be of Category L. Category L materials being dredged, transported and disposed must be handled carefully to minimize the loss of contaminants either into solution or by resuspension.

9.5.5         The results are summarized in Table 9-4 and detailed in Appendix 9.1.

Table 9-4:    Summary of Sediment Sampling and Testing Results

Station

Location

Easting

Northing

Depth

Classification

SD1

Location of proposed diffuser

848645

815745

4m

Cat L

SD2

20m south of the proposed diffuser

848640

815721

4m

Cat L

SD3

Within proposed cofferdam enclosed area

848645

815779

Surface

Cat L

9.5.6         Since SSTP and Sediment Quality Report (SQR) are only serve the purpose of fulfilling the EIA Study for this Project under the EIAO, TM and Study Brief, separate submissions (e.g. SSTP/SQR) to EPD's Territorial Control Office (TCO) will be required when applying for the dumping permit under Dumping at Sea Ordinance (DASO). The rationale for sediment removal/disposal will also need to be submitted to the Marine Fill Committee (MFC) of Civil Engineering and Development Department (CEDD) for agreement in accordance with ETWB TC(W) No. 34/2002 Management of Dredged/Excavated Sediment.

9.5.7         About 500m2 of marine sediment will be dredged, of which 5m2 will be occupied by the diffuser (see Figure 9-2 for dredging boundary). In total, 1,200m3 of dredged marine sediment will be generated. As the quantity of Category L sediment is far below 50,000m3, the open sea disposal site shall be assigned by MFC/CEDD after application of dumping permit under DASO. A maximum of four barge trips per day for sediment disposal is anticipated.

9.6              Land Contamination

Historic Land Uses

9.6.1         Historical aerial photographs covering Po Toi O area were reviewed to evaluate any land use changes associated with potential contamination implication within the proposed work boundary demarcated in Figure 1-1. The oldest aerial photo available dated back to 1945. Changes of land use observed are shown in the following table:

Table 9-5:      Historical Change in Po Toi O and its vicinity

Year

Observation

1945

Very few houses in Po Toi O;

Agriculture lands were found at where the golf course and Fairway Vista are currently located;

Few boats parking in Po Toi O Bay; &

A pier has been established on/before 1945

1963

The pier was expanded; &

Gradually increased in the number of houses in Po Toi O

1973

Fish rafts were erected, more settlement

1979

Site clearance for the construction of Tai Au Mun Road, Po Toi O Chuen Road and Clearwater Bay Country Club; &

Gradual increase in the number of houses in Po Toi O, and the number of fish rafts in Po Toi O Bay

1982

Cut-slope formed at the proposed STP location;

Construction of footpath above the cut slope; &

Concreting of open space outside Tin Hau Temple

1986

Well-developed village in Po Toi O and Tai Wong Kung; &

Obvious increase in the number of fish rafts in Po Toi O Bay

1987

Site clearance for the construction of Fairway Vista and its access road

1996

Site clearance for the construction of Seacrest Villas

2000

Construction of a second pier at Po Toi O

2014

No noticeable change in Po Toi O since 2000.

9.6.2         Based on the aerial photos, Po Toi O was historically used for residential (village), agriculture, boat shelter, fish farming, religious and golfing uses. No boat factory, repairing workshop or other industrial activity that may cause land contamination was identified. Representative photos are provided in Appendix 9.2. No activity that has risk of land contamination was observed.

Existing Land Use

9.6.3         Site inspection was carried out on 20 February 2014 to identify any contamination hotspots within the proposed work boundary. The current land use is for residential (village), fish farming, religious, golfing, dining, tourism and boating uses (inspection photos of current land use are presented in Appendix 9.3). According to AFCD, there is also leisure fishing business on fish rafts. No boat factory, repairing workshop or other industrial activity was observed or reported.

9.6.4         No land contamination report was found in the Po Toi O area. Enquiry has been sought from Environmental Protection Department (EPD) on any historic record on chemical waste producers and spillage/leakage incidences in Po Toi O, and from Fire Services Department (FSD) on dangerous goods licence and spillage/leakage of dangerous of goods. Both departments confirmed neither records were found (letter attached in Appendix 9.4).

9.6.5         As there is no record of industrial land use or leakage of chemical in Po Toi O, land contamination within the proposed work boundary is highly unlikely.

9.7              Estimation of Operational Phase Waste Generation and Evaluation of Impact

Sludge

9.7.1        During the operational phase, sludge with low dry solid content will be produced after the sewage treatment. The normal practice is to dewater the sludge to a dry solid content of 20~30% for disposal at landfills. However, as the estimated daily production of the sludge is 5.3m3, it was considered not cost-effective to expand the footprint of the proposed sewage treatment plant to accommodate a sludge dewatering facility. It is proposed that the sludge with about 7% dry solid content will be removed to a nearby STP for dewatering every 2 days by a sludge tanker. The receptor STP will be identified before operation of the PTO STP.

9.7.2        The new Sludge Treatment Facility in Tuen Mun is in operation and should be able to receive the dewatered sludge by the time the STP runs in 2020. Therefore, no significant impact is expected due to operation of the STP.

9.7.3        Sludge tankers will be used to transport the sludge for treatment. The tanker will park inside the STP building and sludge will be pumped by coupling. The odourous gas will be confined within the STP which will be kept under negative pressure. The gas will be drawn to a deodouring system for treatment before release into the atmosphere. As the transfer process will be carried out in enclosed environment and in low frequency, no odour or traffic impact is expected on the surrounding sensitive receivers during handling of the sludge.

Solid Waste

9.7.4        Screening will be carried out at the sewage inlet to remove large solid matters such as faeces, paper, sand or even plastic bags. The debris produced from the screening process will be removed regularly to maintain the efficiency of the screen and the solid matters will be disposed of at landfill inside sealed containers to contain odour. The production rate is expected to be 0.25m3 per day.

9.7.5        In addition to solid waste from sewage treatment, small amount of general refuse will also be generated from staff, and this shall be dumped at the relocated FEHD refuse collection point or disposed of at landfill together with the debris.

Chemical Waste

9.7.1.      Regular chemical cleaning of the MBR membranes will be required to prevent membrane fouling and to maintain the membrane performance. MBR would be periodically cleaned every 3~6 months. The tanks will be disinfected by sodium hypocholorite. Sodium hypochlorite and/or oxalic acid would be adopted for the removal of organic and inorganic deposits. The cleaning process will take place in-situ on the permeate side without removal of membrane. The deposits will dissolve in the sewage and be treated by the MBR system. The unused chemical will follow the sewage flow in the MBR system, neutralized by hydrogen chloride and eventually be discharged with treated effluent at the diffuser. As the used chemicals will be treated and amount should be small when compared with the quantity of effluent, the water quality impact due to MBR cleaning will not be significant.

9.7.2.      Used filters in the deodourizing unit will be replaced and disposed of as solid waste at landfill. The frequency of removal will be decided in the detailed design stage.

9.7.3.      Emergency generator will be brought to the STP in case of power failure. Diesel will be used as power fuel and the used oil drum will become chemical waste. As dual-feed power from power company will be provided, it is anticipated that only under very rare occasion will both primary and secondary power be failed such that emergency generator will be activated. The quantity of diesel required will be dependent on the time of restoration of the plant and therefore cannot be quantified. However, given the highly infrequent occurrence of the emergency situation, the quantity of used oil drums should be insignificant.

9.7.4.      All chemical waste shall be properly stored, labelled and removed by licensed waste collectors as per Waste Disposal (Chemical Waste) (General) Regulation.

9.8              Mitigation Measures

9.8.1         Careful planning before construction work and close monitoring will be crucial to prevent performing unnecessary works, resulting in extra waste.

Construction Phase

9.8.2         Handling, storage, collection and disposal of waste shall be proposed in accordance with Waste Disposal Ordinance. Good site practices shall be implemented to minimize undesirable nuisance:

C&D Materials

·           The Contractor shall identify suitable location for temporary stockpiling (tentatively within construction site). The stockpile should be covered by tarpaulin or other water-resistant fabric. This can prevent the waste from being blown away by wind or washed into watercourses/sea/drainage system under heavy rain.

·           Waste sorting area should be provided as far as possible to separate out reusable, recyclable wastes and/or public fill. Dumping at landfill should be considered as last resort.

·           Sorted waste should be stored separately at designated locations.

·           Cover waste materials with tarpaulin or in enclosure during transportation

·           As Po Toi O has little flat and vacant land for stockpiling the waste onsite for disposal offsite, the contractor should identify and agree with local residents on commencement of the works for a proper storage/sorting site.

·           Dump trucks should be near fully loaded with excavated materials before departure from the construction site. Frequent movement of traffic is a source of annoyance and increases the chance of accidental leakage.

·           However, the trucks should not be overloaded and the cover should be closed to enclose the excavated materials during movement.

·           Careful planning and estimation should be made to avoid over-ordering and therefore wastage of construction materials.

·           Adopt durable materials for formworks and scaffolding (e.g. steel) for future reuse.

·           Odour-emitting waste should be stored in tight containers.

·           Reduce water content in wet spoil generated from piling work by mixing with dry materials. Only dispose treated spoil with less than 25% dry density to Public Fill Reception Facilities.

Chemical Waste

·           Chemical waste should be stored at designated chemical waste storage area with bunds on impermeable ground. Roof and locks should be provided if stored outdoor. Alternatively, cabinet or cupboard with spill trays can be used if the quantity of waste is small.

·           Chemical waste should be labelled clearly in accordance with Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes to alert workers on hazard during handling and storing:

o   Store chemical waste with suitable containers. Seal and maintain the container to avoid leakage or spillage during storage, handling and transport

o   Label chemical waste containers in both English and Chinese with instructions in accordance to Schedule 2 of the Waste Disposal (Chemical Waste) (General) Regulation

o   The container capacity should be smaller than 450 litres unless agreed by the EPD        

·           Compatible containers should be used for storing specific chemical waste to prevent leakage/spillage (e.g. resistant to corrosive chemicals). Checking of the integrity of the containers before and during use is required.

·           The Contractor should be registered as a Chemical Waste Producer with EPD and engage licensed chemical waste collectors for disposal under the Waste Disposal (Chemical Waste)(General) Regulation.

·           Comply with the requirements of the chemical storage area:

o   Store only chemical waste and label clearly the chemical characters of the waste

o   Have at least 3 sides enclosed and protected from rainfall with cover

o   Provide sufficient ventilation

o   Have impermeable floor and has bunds to contain 110% of the capacity of the largest container or 20% of the total volume of the stored waste in the area, whichever is larger

o   Adequately spaced incompatible materials

·           Transfer used lubricants, waste oils and other chemicals to oil recycling companies, if possible, and empty oil drums for reuse or refill. No direct or indirect discharge is permitted

·           Hire licensed chemical waste disposal contractors for waste collection and removal. Dispose chemical waste at the approved CWTC at Tsing Yi or other licensed facility

General Refuse

·           Sufficient rubbish bins should be provided at regular interval for collection of general refuse.

·           Recycle bins should be provided to encourage recycling of paper, plastic and metal cans.

·           Collected waste should be removed from the construction site by registered collectors regularly.

Good Site Practices

·           Prepare and implement a site specific Waste Management Plan (WMP) as part of Environmental Management Plan (EMP) in accordance with ETWB TC(W) No. 19/2005. Detail waste management method in the form of avoidance, reuse, recovery, recycling, storage, collection, treatment and disposal according to the recommendations on the EIA and EM&A Manual. It should be approved by the engineer’s representative and regularly reviewed.

·           Apply for relevant waste disposal permits in accordance with the Waste Disposal Ordinance (Cap. 354), Waste Disposal (Charges for Disposal of Construction Waste) Regulation (Cap. 345) and the Land (Miscellaneous Provisions) Ordinance (Cap. 28), Dumping at Sea Ordinance (Cap. 466).

·           A trip ticket system should be implemented to monitor the flow of waste from the construction site to public fill reception facilities/landfill/chemical waste treatment facilities/recycler.

·           Works schedule will be well planned to minimize the excavation work area in any time.

·           Should chemical toilet be provided, the sewage shall be regularly cleaned by registered contractor.

·           Provide training to workers on site cleanliness, waste management (waste reduction, reuse and recycle) and chemical handling procedures

·           Maintain drainage systems, sumps and oil interceptors

·           Provide sufficient waste collection points and regular waste removal

·           Minimize wastage through careful planning and avoiding over-purchase of construction materials

·           Store waste materials properly as follows:

o   Avoid contamination by proper handling and storing waste

o   Prevent erosion by covering waste or applying water spray

o   Maintain and clean storage area regularly

o   Sort and stockpile different materials at designated location to enhance reuse

·           Hire licensed waste disposal contractors for waste collection and removal. Dispose waste at licensed waste disposal facilities

·           Provide wheel washing at construction site exit to clean the vehicle body and wheel

·           Organize training and reminders to site staff on waste minimization through avoidance and reduction, reusing and recycling

Bentonite

·           Used bentonite shall be reconditioned onsite and reused as far as practical to minimize wastage. If this is deemed not viable, the used bentonite shall be delivered offsite for reconditioning.

Marine Sediment

·           Since only Category L sediment (i.e. uncontaminated sediment) was identified, dredged marine sediment will be transported by a barge to dispose of at designated marine dumping ground by open sea dumping according to ETWB TCW No. 34/2002 Management of Dredged/Excavated Sediment.

Operational Phase

9.8.3         Sludge will be delivered by sealed sludge tanker for treatment at Sludge Treatment Facilities.

9.8.4         Debris from screening process and general refuse should be stored within the STP in sealed container and be disposed of at landfill regularly.

9.8.5         Worn filters and MBR membrane shall be stored and labelled as in construction phase. Chemical waste shall be treated at chemical treatment facility by licensed contractor.

9.9              Residual Impact

9.9.1         With proper implementation of the mitigation measures, no residual impact is anticipated for waste generated from construction works and operation of PTOSTW.

9.10          Environmental Monitoring and Audit

9.10.1     The Contractor should prepare a Waste Management Plan in accordance with ETWB TC(W) No. 19/2005 Waste Management on Construction Site, which details the expected amount of different types of wastes generated in the coming month and year and updates at regular intervals. The actual waste usage should be recorded monthly. Waste handling, storage and removal methods should also be proposed in the WMP and be reviewed the effectiveness at regular intervals. Training should be provided to all staff to ensure that they are aware of the practice, in particular in chemical waste handling (e.g. understanding of hazard labels and emergency procedures).

9.10.2     Regular site inspection shall be carried out during construction phase to check whether the proposed mitigation measures have been properly implemented and to evaluate the effectiveness.

9.10.3     No EM&A is proposed for Operational Phase.

9.11          Conclusion

9.11.1     During construction phase, major C&D materials will be composed of rock and soil from slope cutting for STP construction. Other waste includes chemical waste from maintenance of plant equipment, used bentonite from drilling works, marine sediment from dredging works and general refuse from workforce.

9.11.2     Sediment Sampling and Testing Plan (SSTP) has been submitted to EPD as required under the Study Brief. Sedimentary Quality Tests of sediment at and near the dredging point showed that the materials were classified as Category L. According to ETWB TC(W) No. 34/2002 Management of Dredged/Excavated Sediment, Category L materials shall be disposed at open sea disposal site assigned by the Marine Fill Committee (MFC).

9.11.3     Since SSTP and SQR are only serve the purpose of fulfilling the EIA Study for this Project under the EIAO, TM and Study Brief, separate submissions (e.g. SSTP/SQR) to EPD's TCO will be required when applying for the dumping permit under DASO.  The rationale for sediment removal/disposal will also need to be submitted to the Marine Fill Committee (MFC) for agreement in accordance with ETWB TC(W) No. 34/2002 Management of Dredged/Excavated Sediment.

9.11.4     Operation of sewage treatment plant will generate sludge, debris from screening, worn filter in deodouring unit and general refuse from staff.

9.11.5     The waste shall be handled and disposed of properly to prevent causing damage to the environment, e.g. water pollution, odour nuisance and hygiene issue. With implementation of the recommended measures and site practices, impact due to waste management is expected to be acceptable.

9.11.6     Based on historical aerial photos, land use history, site inspection and information from EPD and FSD, it is concluded that land contamination within the proposed work boundary is highly unlikely.