Allied Environmental Consultants Limited (AEC) was commissioned to undertake an Environmental Impact Assessment (EIA) for the decommissioning works of the west portion and southern edge of the Middle Ash Lagoon, Tsang Tsui followed by site formation works and construction of drainage and construction access road works (hereinafter known as the “Project”). The EIA study aims to evaluate the potential environmental impact associated with the provision of buildable land at the west portion and southern edge of the Middle Ash Lagoon, Tsang Tsui for the future development. One of the possible future developments is the provision of Columbarium and Garden of Remembrance by the Food and Environmental Hygiene Department (FEHD).

The Project is a designated project under Item 8 of Part II, Schedule 2 of the Environmental Impact Assessment Ordinance (EIAO), i.e. decommissioning of a waste disposal facility for pulverized fuel ash, furnace bottom ash or gypsum. Hence an Environmental Permit (EP) prior to the decommissioning works is required. The construction of Columbarium and Garden of Remembrance, however, does not fall under a designated project and shall not be detailed in the EIA report.

A Project Profile (PP-460/2012) for the Project was submitted to EPD and an EIA Study Brief (No. ESB-243/2012) under the EIAO was issued by EPD on 30 April 2012. An Environmental Impact Assessment (EIA) study was conducted in accordance with EIA Study Brief (No. ESB-243/2012) to provide information on the nature and extent of environmental impact which will arise from the construction and operation of the Project and related activities taking place concurrently.

This Executive Summary presents the key findings of the Environmental Impact Assessment (EIA) for the Project as required under the EIAO.

Project Description

Project Location and Site History

The Subject Site is located in the western part of the Middle Ash Lagoon in Tsang Tsui, Tuen Mun. The site is being operated by Castle Peak Power Company Limited (CAPCO) for the storage of water and pulverised fuel ash (PFA), a by-product of burnt coal from the adjacent Castle Peak Power Station. The ash lagoons at Tsang Tsui was formed by reclamation in the 1980s and is occupied by CAPCO exclusively. According to the current programme, CAPCO will surrender the middle lagoon to the Government in first quarter of 2015.

The Project consists of the Subject Site with a total area of about 30,000m² (3.0 hectares). It comprise of 2.7ha of dry PFA platform and 0.3ha of low zone along the northern boundary, where generally filled up with water by a man-made water channel. The site faces Castle Peak to the south and is separated from Shen Zhen Bay by a seawall on the north.

With reference to the approved EIA report from EPD for the Development of the Integrated Waste Management Facilities (IWMF) Phase 1 (application no. EIA 201/2011), the area directly to the east of the Subject Site is one of the potential sites for the IWMF Phase 1. The remaining Middle Ash Lagoon area will be taken over by the Environmental Protection Department (EPD) as an extension of WENT Landfill (WLES) (application no. EIA-171/2009). Further to the east in the East Lagoon, a Sludge Treatment Facilities (STF) (application no. EIA-155/2008) development is currently under construction which is scheduled to be completed in 2015.

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Subject Site (Photographed on 2014.04.04)

The potential of environmental impact induced by decommissioning of the ash lagoons at Tsang Tsui had been evaluated in detail by previously approved EIA studies, including Sludge Treatment Facility (EIA-155/2008), West New Territories (WENT) Landfill Extensions (EIA-171/2009), and proposed Integrated Waste Management Facility (EIA-201/2011).

All these approved EIA concluded that the potential adverse environmental impact are of insignificant level to sensitive receivers. Take into consideration the similar activities and sensitive receivers of this project to the aforementioned EIA studies, the potential adverse environmental impact are anticipated to be insignificant level to sensitive receivers.

Background and Need for the Project

Finding a solution to limited land resources has always been in the agenda for Hong Kong. In light of the fact that the Site Area will be surrendered by CAPCO to the government in the first quarter of 2015, it is necessary to utilize this new plot of vacant land to good use.

Before any development planning, decommissioning would be deemed to be required for any future development due to its current use as pulverized fuel ash storage area. The EIA had evaluated the environmental impacts associated with the decommissioning process at the west portion of the Middle Ash Lagoon at Tsang Tsui, Tuen Mun. One of the potential usages of this new plot of vacant land is the development of Columbarium.

Due to its size and separation from domestic developments, the Subject Site is considered a favourable candidate for columbarium facility. As such, the Project aims to provide buildable land for the future government developments, amongst them a Columbarium and Garden of Remembrance through decommissioning of the western part of the Middle Ash Lagoon.

Benefits

The decommissioning works which consists of covering of 1m thick general fill above the final PFA platform at the Subject Site and Construction Access Road Area would provide environmental benefit as it prevents potential PFA exposure to the Public and provide buildable land for future developments on the Subject Site.

Consideration of Alternatives

The aim of the EIA study is to evaluate the environmental impacts related to decommissioning process of west portion of the Middle Ash Lagoon at Tsang Tsui, Tuen Mun and its associated site formation works. A fundamental project alternative is the option to not implement the decommissioning, site formation, drainage and road works, which in environmental terms is referred to be as the “Do-nothing” option. However, the provision of buildable land is essential in order for the government to provide sufficient facilities to the public. As such, the “Do-nothing” option is not preferred.

Project Scope

The decommissioning works in the Project shall mainly involve the following:

• Covering of 1m thick general fill above the final PFA surface with minor levelling works

• Formation of Construction Access Road (North) by filling and levelling followed by layering of a 1m thick general fill above the final PFA surface to proposed levels

• Formation of part of the Construction Access Road (South) by layering of a 1m thick general fill above the final PFA surface to proposed levels, followed by levelling and slope works along the road section approaching to the Site

In addition, associate works in the Project, which will not involve decommissioning, include the following:

• Minor reinstating works on part of the existing access road to form the Construction Access Road (South)

• Construction of retaining structure for slope stabilization along the edge of existing water channel near the north site boundary

• Installation of surface drainage outfall system for discharging the surface water out of the complete buildable land at the north-west corner of the Subject Site

• Installation of site hoarding and temporary surface drainage system

The operational phase of the Project is when the decommissioning works detailed above is completed to provide a flat buildable land for future development by the government.

Construction Programme

The decommissioning works will commence around September 2015. The completion date is tentatively scheduled on March 2016.

Any Related Projects

The Project is located in the ash lagoon areas which are currently occupied by CAPCO for uses relating to the operation of the Castle Peak Power Stations. Various projects have been proposed in the Nim Wan and Tsang Tsui areas, including the STF, WLES, and the IWMF.

Consideration of Alternative Decommissioning Methods

Potential decommissioning methods are identified as (1) in-situ treatment such as hardening with cement; (2) off site treatment or storage; and (3) covering with soil.

In-situ treatment

In-situ treatment, such as hardening with cement could chemically and physically fix the PFA in the cement matrix, leading to the stable ground condition. However, this method is considered not feasible, due to the large quantity (approximate 15,000m³) of cement is required to fix the PFA with the Site.

Off Site Treatment

Taken into account of the relatively stable PFA and its large quantity, disposal of PFA to other storage facilities is not a favourable environmental alternative since it would generate a large amount of PFA as waste. Excavating the PFA to off-site location for recycle and treatment would involve extensive transportation. Moreover, excavation of PFA would pose possible environmental and health hazards to workers due to PFA dust emission during excavation works. In addition, transportation of large amount of PFA for disposal is not a cost-effective option. In addition, there are currently no government-specified location for the disposal of PFA.

Recycle for Concrete Production

Due to the large amount of PFA, exportation of PFA for reproduction of concrete might would require transportation of large quantity of PFA and also a long period of time for consumption. It may cause more environmentally adverse impacts to the public and fail to provide buildable land in the case of the shortage of territory currently.

Covering with Soil

Leaving the PFA in-situ is considered as the most cost and environmental viable option. As such, decommissioning of the Subject Site through covering of 1m thick general fill above the final PFA surface upon minor levelling works is adopted in this Project. Different fill materials such as broken stone, concrete, and other hard inert material, have been considered for filling of PFA areas. However, the import of general fill compared with the aforementioned alternative materials is more cost-effective. Moreover, in the long run, general fill material is easier to manage for any future developments at Subject Site.

Preferred Decommissioning Method

The Project’s adopted decommissioning method of importing 1m thick general fill to cover the PFA surface aims at cost-effectiveness while minimizing impact on the environment. During the Project, mobilisation and preparation/establishment will be carried out by the Contractor. Careful design of the decommissioning works will be adopted to optimize the import of materials. No surplus construction materials/waste is to be delivered to public fill bank.

Slope Stabilization Works

To the existing water channel at the north of the Subject Site, one of the options is to fill up the entire water channel to provide more land for future developments. However, in view that the water channel may provided suitable nesting grounds to Little Grebes as breeding habitat during the wet season, filling up the water channel is deemed to cause the ecological impact. In this connection, the decommissioned area is considered to reduce and the construction sequence is carefully phased in order to reduce the Project’s environmental impact to the Little Grebes.

In the current design, slope stabilization works would be carried out to the edge of the water channel to prevent soil loss of water channel through erosion as well as providing a stable habitat. A surface water drainage system would be constructed to discharge future storm water runoff from the Subject Site and prevent adverse environmental impact to the water channel. Such works would provide long-term environmental benefits as well as minimization of habitat loss

Key Findings of the Environmental Impact Assessment

Air Quality Impact

Potential air quality impact associated with the construction and operational phase of the Project have been assessed in the EIA report. Representative Air Sensitive Receivers (ASRs) within 500m of the Subject Site have been identified.

A total of two representative ASRs were identified for this assessment in accordance with the criteria set out in the EIAO (TM). They include (1) the current WENT Landfill Site office and (2) STF Office located at over 200m from the Subject Site.

Construction Phase

Air quality impacts from the decommissioning and construction works for the Project would mainly be related to construction dust from materials handling, construction access road, filling activities, wind erosion of open sites and stockpiling areas.

Effective dust control following the requirements given in the Air Pollution Control (Construction Dust) Regulation and in accordance with the EM&A programme during construction are recommended. With implementation of control measures the proposed Project would not cause adverse cumulative air quality impact at all air sensitive receivers in the vicinity of the Subject Site.

In view of the large separation distance (more than 200m) of the nearby ASRs from the Project Site, no dust monitoring is considered necessary. Yet, regular site environmental audits during the construction phase of the Project will be conducted to ensure that the recommended dust suppression measures are implemented properly.

Operational Phase

The operational phase of the Project shall be a piece of buildable land available for future developments by the government. Since the operational phase does not involve any equipment operation or human activities, adverse air quality impact is not expected.

Health Impact Assessment

Potential health impact associated with the construction phase of the Project have been assessed in the EIA report.

Construction Phase

A Human Health Risk Assessment has been conducted to identify potential health effects from exposure to chemicals in a contaminated environmental media. Through a systematic screening, 7 Chemicals of Particular Concerns (COPCs) were identified: Arsenic, Cadmium, Lead, Nickel, Chromium (VI), Manganese, and Mercury. Quantitative risk assessment was conducted for these COPCs, and it was determined that the calculated incremental risk levels caused by the decommissioning works would be below risk levels of 1 in 100,000 as suggested by US Environmental Protection Agency (USEPA), thus adverse health effect is unlikely to be anticipated.

Cumulative non-carcinogenic health impact has been assessed and compared with local and overseas guideline levels. As the predicted COPCs concentration are found to be lower than the corresponding guideline levels, it was concluded that the levels of non-carcinogenic chemicals were found to be insignificant when compared to the adopted/derived reference levels.

The health risk arising from radon emission from PFA has been evaluated. Quantitative assessment has been conducted to determine the radon risks of on-site workers. It was found that the workers’ predicted annual effective dose is less than annual limit of 1 mSv for general public as suggested by the International Commission on Radiological Protection (ICRP). The findings also meet the findings from various literature researches, in which the radon health risk for the decommissioning works is of insignificant level.

Noise Impact

Potential noise impacts associated with the construction and operational phase of the Project have been assessed in the EIA report. Noise sensitive receivers were not identified within 300m of the Subject Site. Nearest possible noise sensitive receivers identified include village houses at Lung Kwu Sheung Tan and Ha Pak Nai, located 3km and 2km away from the Subject Site.

Construction Phase

Potential construction noise impacts are likely caused by various construction activities on site, such as, formation of construction access road by excavation, filling and leveling works, installation of temporary surface drainage system, site formation works including leveling of PFA surface and filling of 1m thick general fill.

Assessment results show that the maximum predicted noise level associated with the construction activities on the Subject Site to Noise Sensitive Receivers of Lung Kwu Sheung Tan and Ha Pak Hai would be 49dB(A), which does not exceed the noise criteria as specified in the Technical Memorandum on Environmental Impact Assessment Process.

Good practices stipulated in relevant standards and Technical Memorandum for the control of noise emissions from construction sites are still recommended to further reduce any potential nuisance. Adverse noise impact during the construction phase is not anticipated. In view of the large separation distance of the nearby NSRs from the Project Site, no noise monitoring is considered necessary. Yet, regular site environmental audits during the construction phase of the Project will be constructed to ensure that the recommended noise mitigation measures are implemented properly.

Operational Phase

Water Quality Impact

Potential water quality impacts associated with the construction and operational phase of the Project have been assessed in the EIA report. Representative Water Sensitive Receivers (WSRs) within 500m of the Subject Site have been identified.

Three water sensitive receivers have been identified within 500m from the site boundary of the Project. They include two moderate sized streams (“Stream W1” and “Stream W2”) located at the southern part of ash lagoon and discharged into a tidal channel to the east of the ash lagoon area and Deep Bay.

Construction Phase

Sources of water quality impact throughout the decommissioning and construction phase include (1) drainage and construction site-runoff from construction of retaining structures for slope stabilization and construction of surface drainage outfall, (2) PFA contaminated surface runoff, (3) sewage effluent produced by workforce and (4) wastewater generated from general construction activities.

With proper implementation of construction site mitigation measures and good site practices as followed to ProPECC PN 1/94, such as provision of site runoff collection system and chemical toilets, adverse water quality impacts during construction phase is not anticipated.

A water quality monitoring programme and site environmental inspection will be implemented to ensure the effectiveness of the recommended mitigation measures.

Operational Phase

Waste Management Implications

Potential waste management options associated with the construction and operational phase of the Project have been assessed in the EIA report. Mitigation measures and good site practices were identified and were recommended in the EIA report with reference to the applicable waste legislations and guidelines.

Construction Phase

The types of waste that would be generated during the decommissioning and construction phases of the Project include construction and demolition (C&D) materials from the construction activities, general refuse from the workforce and chemical wastes from the maintenance of construction equipment. The estimated amount of C&D fill material is 30,000m³ for Subject Site and 10,000m³ for Construction Access Road Area.

All PFA excavated during levelling works shall be reused as site formation material within the site boundary. This shall be included in contractual specifications.

Various waste management options were explored to minimize the environmental impact. The hierarchy shall be adopted in the following order:

– Avoidance and reduction;

– Reuse of materials;

– Recovery and recycling; and

– Treatment and disposal

The decommissioning contract has provision for how the wastes are handled, transported and disposed of properly and good site practices and waste reduction measures are implemented accordingly, adverse environmental impact is not expected during the construction phase of the Project.

Operational Phase

Land Contamination Assessment

Potential land contamination impact associated with the construction and operational phase of the Project have been assessed in the EIA report. Land contamination assessment has been conducted based on historical and current land use.

Construction Phase

The Subject Site has been used by CAPCO for the storage of water and PFA since the 1980s. An assessment was conducted with reference to the checklist obtained from Annex C1 of Practice Guide for Investigation and Remediation of Contaminated Land. The results confirmed that no known contaminants or chemicals were found on site aside from PFA. It is concluded that there is no adverse impact from land contamination.

Operational Phase

Landfill Gas Hazard

Potential landfill gas (LFG) hazards during the construction and operational phase of the Project have been identified. The potential impacts of LFG hazards from the proposed WENT Landfill Extension have been assessed based on the Landfill Gas Hazard Assessment (LFGHA) Guidance Note.

Construction Phase

Landfill Gas Hazard Assessment Study was conducted in accordance with the Landfill Gas Hazard Assessment Guidance Note. A source-pathway-target analysis was conducted to assess the risk of landfill gas hazard associated with the Project. According to the classification of risk category, the landfill gas hazard risk for the Project was identified as MEDIUM for both construction workers working outdoors and site office personnel.

Nevertheless, a number of protection measures will be implemented to safeguard the safety of the site workers and all personnel presence of the Subject Site. Precautions should be clearly laid down and rigidly adhered to with respect to:

– Trenching and excavation; and

– Creation of confined spaces at, near to or below ground level.

Moreover, the Contractor will be required to submit their landfill gas monitoring plan and precautionary measures to the Project Team for their approval before the commencement of work.

With the implementation of these projection measures, no adverse impact of landfill gas hazard to this Project is anticipated.

Operational Phase

The operational phase of the Project shall be an idle buildable land to cater any future developments by the government. The operational phase of the Project will be under an open area, thereby adverse environmental impact arising from landfill gas hazard is not expected. In light of the anticipation for the operation of WENT Landfill Extension, any such future developments would render the respective project proponent to have to undertake another set of LFG assessment based on the respective design provisions in order to assess landfill gas hazards.

Ecological Impact

A literature review supplemented by comprehensive ecological survey conducted during April 2012 to September 2012 was undertaken to establish the ecological profile within the Study Area, which is delineate by an area within 500m from the Subject Site.

Ecological resources recorded within the Study Area include woodland, plantation, orchard/village, grassland / shrubland, watercourse, ash lagoon, seawall, urbanized / disturbed areas and coastal waters and its associated flora and fauna species. Woodland, natural section of watercourse, water channel/water-filled portion of the Middle Ash Lagoon, and West Ash Lagoons had low to moderate ecological values, whereas other habitats had low ecological values. In accordance with the survey at 2012, 2013 and 2014, species of conservation concern recorded within the Study Area include three flora and eighteen fauna species (including bats, birds and dragonflies). Breeding of Little Grebe was recorded at both Middle and West Ash Lagoon including the Subject Site.

Ecological impacts of the proposed Project include permanent loss of about 4 hectares of ash platform, urbanized/disturbed habitat and grassland/shrubland. The majority of the associated habitat loss are considered as an artificial habitat with regular disturbance from ash dumping and pumping of water from CLP Plant. On the other hand, installation of drainage pipes would encroach about 0.03 hectare of the man made water channel at the north-west corner of the Subject Site, while construction of retaining structure for slope stabilization along the edge of the existing water channel near the north boundary will lead to an increase of about 0.03 hectare of water channel area. Therefore, there is no net loss of water channel surface.

During the course of the survey, the landscape of the site changed frequently as it was shaped by the continual storage of PFA by CAPCO. On the latest site surveillance, water bodies were found on the northern and eastern edge of the Middle Lagoon. The observed behavior of the little grebe suggests that their breeding ground will be confined to those areas . Given the absence of a large water body in the Subject Site, the impact of the decommissioning work to the breeding of Little Grebe is considered minimal. Nevertheless, mitigation will be in place to protect the remaining water body on site. This entails the incorporation of the following in the site development stage: the construction of an embankment, the erection of 2.4m high fencing and the construction of a landscaped buffer zone adjacent to the site.

The construction of retaining wall for slope stabilization area shall be minimized in scale, whereas construction period will be limited within non-breeding season of Little Grebe. The “non-breeding season of Little Grebe” is assumed to be dry season, which is November to March in following year, in accordance with definition as stated in EIAO Guidance Note.

As the Project would not involve any marine works, no direct marine or intertidal habitat loss from the Project is anticipated.

With the implementation of the mitigation measures to keep the water body intact, the residual impacts are considered minimal and acceptable. The overall impacts to terrestrial and freshwater habitats are ranked as low.

Environmental Monitoring and Audit

Environmental monitoring and audit (EM&A) programme will be implemented during the construction of the Project to ensure the effectiveness of the recommended mitigation measures and compliance with relevant statutory requirements. Details of the EM&A works have been specified in the EM&A Manual. The EM&A Manual contains full details of proposed baseline and compliance monitoring programme, implementation schedule of the environmental protection / mitigation measures, EM&A reporting procedures, and complaint handling procedures.

Overall Conclusion

An EIA report has been prepared to study the decommissioning works of the west portion and southern edge of the Middle Ash Lagoon, Tsang Tsui followed by site formation works and construction of drainage and road works. The EIA report has been prepared to fulfill requirements as specified in the EIA Study Brief (No. ESB-243/2012) and the Technical Memorandum on Environmental Impact Assessment. All the latest design information has been incorporated into the EIA process. Where necessary and practicable, the EIA has specified mitigation and control measures to reduce the environmental impacts to acceptable levels.

The EIA Report has predicted that the Project would be environmentally acceptable and with low residual impacts through the implementation of the proposed mitigation measures. The schedule of implementation of the recommended mitigation measures has been provided in the EIA report. Monitoring requirements have also been specified in a separate EM&A manual to ensure proper implementation of the recommended mitigation measures.