TABLE OF CONTENTS

Page

6 Land Contamination. 6-1

6.1 Introduction. 6-1

6.2 Environmental Legislation, Standards and Criteria. 6-1

6.3 Assessment Methodology. 6-1

6.4 Description of the Project Area. 6-1

6.5 Identification of Potential Land Contamination Concern. 6-1

6.6 Prediction and Evaluation of Environmental Impacts. 6-1

6.7 Mitigation of Adverse Environmental Impacts. 6-1

6.8 Evaluation of Residual Impacts. 6-1

6.9 Conclusion. 6-1

LIST OF TABLES

Table 6.1 Summary of Hotspots within STSTW.. 6-6

LIST OF FIGURES

60334056/EIA/6.01 Project Location and Works Area

60334056/EIA/6.02 General Site Layout of Existing STSTW, Existing Vehicle Detention Centre and Its Surrounding Areas and Niu Po Shan North

60334056/EIA/6.03 General Site Layout of Existing STSTW and Proposed Sampling Locations

60334056/EIA/6.04 General Site Layout of Existing Vehicle Detention Centre and Proposed Sampling Locations

LIST OF APPENDICES

Appendix 6.01 Contamination Assessment Plan (CAP)

6 Land Contamination

6.1 Introduction

6.1.1.1 This section presents the potential implications of land contamination associated with the Project. The detailed CAP is given in Appendix 6.01.

6.2 Environmental Legislation, Standards and Criteria

6.2.1.1 The relevant environmental legislation guidelines and standards on land contamination aspect include the following:

¡P Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM)

¡P Guidance Note for Contaminated Land Assessment and Remediation (Guidance Note)

The Guidance Note sets out the requirements for proper assessment and management of potentially contaminated sites such as oil installations (e.g. oil depots, petrol filling stations), gas works, power plants, shipyards / boatyards, chemical manufacturing / processing plants, steel mills / metal workshops, car repairing / dismantling workshops and scrap yards. In addition, this Guidance Note provides guidelines on how site assessments should be conducted and analysed and suggests practical remedial measures that can be adopted for the clean-up of contaminated sites.

¡P Practice Guide for Investigation and Remediation of Contaminated Land (Practice Guide)

This guide outlines typical investigation methods and remediation strategies for the range of potential contaminants typically encountered in Hong Kong.

¡P Guidance Manual for Use of Risk-based Remediation Goals for Contaminated Land Management (Guidance Manual)

The Guidance Manual introduces the risk based approach in land contamination assessment and present instructions for comparison of soil and groundwater data to the Risk-Based Remediation Goals (RBRGs) for 54 chemicals of concern commonly found in Hong Kong. The RBRGs were derived to suit Hong Kong conditions by following the international practice of adopting a risk-based methodology for contaminated land assessment and remediation and were designed to protect the health of people who could potentially be exposed to land impacted by chemicals under four broad post restoration land use categories. The RBRGs also serve as the remediation targets if remediation is necessary.

6.3 Assessment Methodology

6.3.1.1 Land contamination assessment was carried out according to the abovementioned EIAO-TM, Guidance Note, Practice Guide and Guidance Manual.

6.3.1.2 A site appraisal, including site walkover and desktop review, was conducted to identify the potentially contaminating land uses that may pose adverse impact to the Project. Site walkover was conducted within the Project Area to review the general site conditions and to identify any source of land contamination (or ¡¥hotspots¡¦). For the desktop review, the following information was reviewed:

¡P Relevant ground investigation reports from CEDD civil engineering library;

¡P Hong Kong Geological Survey Map (Series HGM20) ¡V Sheet No. 7 (1:20,000);

¡P Aerial photographs and topographic maps;

¡P Records (if any) on dangerous goods, chemical wastes, chemical spillage/leakage and fire incidents from the identified potentially contaminated sites from EPD or Fire Services Department (FSD); and

¡P AECOM, Final Report under Agreement No. CE 43/2011 (DS) ¡§Relocation of Sha Tin Sewage Treatment Works to Caverns ¡V Feasibility Study, May 2014.

6.3.1.3 Based on the site appraisal, sampling locations and depths for soil and groundwater at potentially contaminated sites have been proposed. A CAP, detailed findings of the site appraisal and the proposed site investigation (SI) works, were submitted to EPD for agreement and enclosed in Appendix 6.01.

6.3.1.4 As reported in the CAP, all the identified potentially contaminated land uses were in operation, the SI works and the subsequent assessment are therefore proposed to be carried out after decommissioning but before the re-development of the concerned sites. For these concerned sites, review of the initial contamination, possible remediation methods, potential insurmountable impacts, SI requirements as well as the tentative timeframe for subsequent submissions were presented in the CAP.

6.4 Description of the Project Area

6.4.1.1 The Project Area is illustrated in Figure No. 60334056/EIA/6.01. For the purpose of the assessment, the Project is divided into the following 3 areas:

(i) Existing STSTW

The area included the existing STSTW but excluded WSD Salt Water Pumping Station to the north of STSTW which is not part of the Project Area (refer to Figure No. 60334056/EIA/6.02).

(ii) Part of Existing Vehicle Detention Centre (VDC) and its surrounding areas

The area comprises part of existing VDC (i.e. the temporary works area on Area 73) and its surrounding areas (refer to as ¡¥Area A¡¦). The areas are shown in Figure No. 60334056/EIA/6.02. Surrounding areas of VDC mainly include a small section of A Kung Kok Street near the entrance of THEES portal, vacant area adjacent to VDC, landscape area south of VDC (between Ma On Shan Road and A Kung Kok Road), and cycling tracks and footpaths northeast of VDC.

(iii) Nui Po Shan North

The area mainly covered the northern portion of existing Nui Po Shan, bounded to the north by Mui Tsz Lam Road and northwest by A Kung Kok Street, including the proposed A Kung Kok Shan Road surface magazine site (refer to Figure No. 60334056/EIA/6.02).

6.5 Identification of Potential Land Contamination Concern

6.5.1.1 Site appraisal was carried out in the period from November 2014 to March 2015 with site walkovers conducted in November 2014 and January / July / November 2015. Findings of the site appraisal were detailed in the CAP enclosed in Appendix 6.01 and summarised below:

6.5.2 Existing STSTW

6.5.2.1 The existing STSTW is on reclaimed land and the reclamation works in the area was first noted in 1974 and completed around 1981. STSTW Stage 1 construction was noted between 1979 and 1982 while Stages II and III extension were completed in 2004. No major construction was noted after 2009 when the UV disinfection chamber was completed. Based on the site observations and confirmation from the review of aerial photographs, a large portion of the site was covered by vegetation with less than half of the area occupied by facilities and buildings.

6.5.2.2 A number of hotspots, including, for example, workshop, transformers, generators, diesel tanks and chemical / chemical waste storage area, were identified during the site walkover and were shown in Table 6.1 and Figure No. 60334056/EIA/6.03. There could be land contamination impacts if the underlying soil / groundwater were contaminated during the handling and storage of hazardous substances within the hotspots. SI works are therefore recommended within the existing STSTW. Based on the site appraisal, the chemicals / chemical wastes stored on-site and of concern included diesel fuel, lubricating oil, transformer oil, mineral oil and organic solvent. The Chemicals of Concern (COCs) include metals, Volatile Organic Compounds (VOCs), Semi-Volatile Organic Compounds (SVOCs), Petroleum Carbon Ranges (PCRs) and Polychlorinated Biphenyls (PCBs).

6.5.3 Existing Vehicle Detention Centre (VDC) and its Surrounding Areas

6.5.3.1 The area is on reclaimed land. Reclamation of the VDC and Area A was completed in 1985. The area of existing VDC became vacant until structures, likely for nearby construction works, were noted from 1989 to 1993. The whole area of the VDC was vacant again after 1993 and then became a car park in 1995 until 2004 when the footprint of the VDC was noted. No significant change in land uses were observed since then.

6.5.3.2 For Area A, the landscape area was observed after reclamation in 1985 and was observed covered with vegetation in 2009. Cycling tracks and footpaths at northeast of VDC, and vacant area north of Ma On Shan Road were observed in the remaining area of Area A were observed in the 1990s. No significant change in land uses were observed since then.

6.5.3.3 Based on the site appraisal, the existing VDC was operated by the Customs and Excise Department (C&ED). Main activities carried out at the site were storage of detained vehicles and seized goods. Based on the site visit, the detained vehicles are in good condition and the seized goods are only empty containers. The area is only used for storage and neither vehicle nor equipment repairing activities was conducted. Apart from the pest control used on-site, no chemicals were observed stored or handled on site. The area was concrete paved and no apparent stains were observed during the site walkover.

6.5.3.4 According to C&ED, one lot of spent vehicle batteries was temporarily stored on site in 2012 and was later collected from VDC by EPD¡¦s licensed chemical waste collector. Based on the site walkover, the storage area was paved with additional layer of concrete above the concrete paved ground, with no stain and stressed vegetation observed. No past records of battery leakage were reported within the VDC.

6.5.3.5 Based on the site condition and nature of VDC, widespread contamination is not envisaged across the site. The potential land contamination concerns are likely restricted to the temporary storage area for the spent batteries and storage area for seized goods, both located within the Project boundary. Locations of the potential hotspots are shown in Figure No. 60334056/EIA/6.04.

6.5.3.6 Apart from the above, no apparent or historical evidence of contamination within the remaining area of VDC and its surrounding areas were identified. Land contamination impacts are therefore not anticipated within these areas.

6.5.4 Nui Po Shan North

6.5.4.1 Based on the site appraisal, most of Nui Po Shan North was undeveloped. There were only 3 areas that had been developed for use as (i) works area by the contractor along Mui Tsz Lam Road, (ii) effluent inlet point for the THEES (THEES Portal) and (iii) the Evangelical Lutheran Church of Hong Kong (David Camp). The three areas are shown in Figure No. 60334056/EIA/6.02.

6.5.4.2 From the aerial photographs, the contractor¡¦s works area and the THEES Portal were noted in 1994 and 1993 respectively and there were no significant changes observed since then. Based on the site walkover, the contractor¡¦s works area was used as site offices, car parking area and storage of construction materials. The THEES Portal was used to serve as the inlet point to convey the treated effluent to Victoria Harbour. Both areas were paved with intact concrete with absence of stains on ground. No chemicals / chemical wastes were reported or observed stored on-site. Land contamination impacts are therefore not anticipated within the 2 areas.

6.5.4.3 The David Camp was not accessible at the time of the site walkover. However, according to Leisure and Cultural Services Department (LCSD)¡¦s website, David Camp is a holiday camp site operated by Evangelical Lutheran Church of Hong Kong. The site is likely to be used for non-contaminating activities such as recreation activities, classrooms, place of worship and accommodations. Land contamination impacts are therefore not anticipated within the area.

Table 6.1 Summary of Hotspots within STSTW

Location (Site Area)	Concerned Area (approx. area)	Summary of Site Appraisal	Necessity and Rationale for Intrusive Site Investigation (SI)	Proposed Borehole ID*
Existing STSTW (280,000m^2) (Inspection Date: 7 Nov 2014 & 28 Jan 2015)	Chemical Wastes Store (26 m^2)	- Empty chemical containers are stored on shelf in the Chemical Waste Store. The floor of the store is concrete paved and were observed in good condition without stain. - Chemicals observed included spent sulfuric acid, nitric acid and alkali.	1 sampling location proposed. COCs includes metals, VOCs, SVOCs and PCRs.	ENV-BH01
	Dangerous Goods (DG) Store (28m^2)	- No report of spillage or leakage of dangerous goods was reported from FSD records - The floor of the DG Store is concrete paved and was observed in good condition. - The DG containers are observed to be in good condition. - Chemicals stored include paints and thinner.	1 sampling location proposed. COCs includes metals, VOCs, SVOCs and PCRs.	ENV-BH02
	Chemical Waste Area (42 m^2)	- The Chemical Waste Area has a metal roof and the floor of the area is concrete paved with bunding. The concrete pavement and bunding are in good condition. - Empty lubrication oil, grease container, bleach drum and waste battery are temporary stored in this area until collection by registered chemical waste collector.	1 sampling location proposed. COCs includes metals, VOCs, SVOCs and PCRs.	ENV-BH03
	Scrap Iron Storage Area (21m^2)	- Metal scraps such as machine parts are temporary stored in this area till collection by contractor. The area is paved with intact concrete.	1 sampling location proposed. COCs includes metals, VOCs, SVOCs and PCRs.	ENV-BH04
	Chemical Waste Collecting Tank(34 m^2)	- The chemical waste collecting tank is placed on top of a concrete paved area with concrete bunding to prevent spilling and leakage. - Chemical containers and oil drums would be emptied to this collecting tank before placing them in the chemical waste store and chemical waste area.	1 sampling location proposed. COCs includes metals, VOCs, SVOCs and PCR.	ENV-BH05
	Mechanic Workshop (1090 m^2)	- The workshop is concrete paved with no oil stain observed. Repair and maintenance of valve bodies, spindles pumps and other light machine take place in the workshop. - Typical maintenance may include greasing and lubrication involving lubrication oil.	6 sampling locations proposed according to the area. COCs includes metals, VOCs, SVOCs and PCRs.	ENV-BH06 ENV-BH07 ENV-BH08 ENV-BH09 ENV-BH10 ENV-BH11
	Administration and Laboratory Buildings, CLP Transformer No. 1, Transformer No. 19 and No. 20	- The area housed offices and laboratory. The laboratory is located on the first floor of the Laboratory Building. - The ground floor of the Laboratory Building is used only as an exhibition centre and general storeroom (e.g. brand new plastic tubes and wooden sticks). No chemicals were found. - There are a total of 3 transformers (labelled as ¡¥CLP Transformer No. 1¡¦ and ¡¥Transformer No. 19¡¦ and ¡¥No. 20¡¦) in the area. - CLP Transformer No. 1 is operated by CLP and located within the substation. Ground are concrete paved and without stains. - Transformer No. 19 and No. 20 are housed within the transformer rooms. The transformer rooms are elevated on an approximately 0.5m concrete platform.	No land contamination was found within the ground floor of the Administration and Laboratory Buildings. Intrusive SI was considered not necessary. 3 sampling location is proposed for the transformer CLP No. 1, No.19 and No. 20 COCs includes metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH12 ENV-BH12A ENV-BH12B
	Chemical Store (166 m^2)	- The Chemical Store is fully enclosed and the floor of the store is concrete paved. No sign of spillage or stain was observed. - Mainly lubrication oil was stored in the area.	3 sampling locations proposed based on the area. COCs include metals, VOCs, SVOCs and PCRs	ENV-BH13 ENV-BH14 ENV-BH15
	Fuel Oil Tanks	- There are two 1000 L above-ground diesel storage tanks to fuel the nearby generators. - The 2 storage tanks are placed on concrete paved ground with bunding. The paved ground and bunding are observed to be in good condition. - A diesel filling point was also observed near the diesel storage tank.	3 sampling locations are proposed (2 at each storage tank and 1 at the diesel filling point). COCs include metals, VOCs, SVOCs and PCRs.	ENV-BH16 ENV-BH17 ENV-BH18
	Power House + Transformer No. 21 and No. 22 (2470 m^2)	- The Power House consisted of a (i) generator room, (ii) control room / office and (iii) air blower rooms. - The generator room (approximately 1,525 m^2) housed 6 generators. Lubrication oil bottles and oil drums are observed at the temporary chemical waste collecting point (approx. 6m^2), at the southern corner of the generator room. The room is tiled and paved with concrete. No stains were observed. - The air blower rooms (approximately 675 m^2) housed 5 air blowers and are located at the northern portion of the building. The room is paved with intact concrete with no stains observed. - Two transformers (labelled as ¡¥Transformer No. 21¡¦ and ¡¥22¡¦) were located at the western side of the Power House.	14 sampling locations proposed (6 for generator room, 5 for the air blower room, 2 for each of the transformers and 1 for the chemical waste collecting point). COCs include metals, VOCs, SVOCs, PCRs and PCBs (for transformer only).	ENV-BH19 ENV-BH20 ENV-BH21 ENV-BH22 ENV-BH23 ENV-BH24 ENV-BH25 ENV-BH26 ENV-BH27 ENV-BH28 ENV-BH29 ENV-BH30 ENV-BH31 ENV-BH32
	Transformer No. 11 to No. 18	- There are 8 transformers (labelled as Transformer No. 11 to 18) near the Power House for the operation of the Power House and Boiler House. - All 8 transformers are housed within the transformer rooms. The transformer rooms are elevated on an approximately 1.0m concrete platform. No stains were observed on the floor.	8 sampling locations proposed for each of the transformer. COCs include metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH-T1 ENV-BH-T2 ENV-BH-T3 ENV-BH-T4 ENV-BH-T5 ENV-BH-T6 ENV-BH-T7 ENV-BH-T8
	Sludge Thickening House (890m^2) + Transformer No. 5, No. 6 and Transformer A.	- 6 set of consolidated sludge pumps were situated in the basement of the building. - The building is fully concrete paved (included the basement), pipe lines, centrifuge feed tanks, thickened sludge receiving tanks and cold water receiving tanks were observed on the ground floor. - There are 3 transformers (labelled as Transformer No. 5, No. 6 and A) near the Sludge Thickening House. The transformers are on an elevated concrete platform of approximately 1.0m thick. No stains were observed on the floor.	9 sampling locations (6 for the consolidated sludge pumps in the basement and 3 for each of the transformers). COCs include metals, VOCs, SVOCs, PCRs and PCBs (for transformers only).	ENV-BH33 ENV-BH33A ENV-BH34 ENV-BH34A ENV-BH35 ENV-BH35A ENV-BH36 ENV-BH36A ENV-BH36B
	Air Blower House (1307 m^2) + Transformer No. 1 to No. 4	- The Air Blower House consisted of air blower room to the east and switch / transformer room to the west. - The air blower room (approximately 504 m2) housed 6 air blowers. Diesel and lubrication oil were used for their operation. - Temporary oil drums storage were observed to the north of the air blower room. The room is paved with concrete and no stains were observed. - The switch room is located to the north of the switch / transformer room whereas the transformer room is located to the south. There are 4 transformers (labelled as Transformer No. 1 to No. 4). The room is paved with concrete and no stains were observed.	11 sampling locations proposed (6 for air blower room, 4 for each of the transformers and 1 for the temporary oil drums storage). COCs include metals, VOCs, SVOCs, PCRs and PCBs (for transformers only).	ENV-BH37 ENV-BH38 ENV-BH39 ENV-BH40 ENV-BH40A ENV-BH41 ENV-BH41A ENV-BH42 ENV-BH42A ENV-BH43 ENV-BH43A
	Switchgear House (288 m^2) + Transformer No. 7 to 10 + CLP Transformer No. 2	- Reported by the site supervisor, the switchgear house were rarely been used. - Control panels were placed at the southeastern half of the building whereas 4 transformers (labelled as Transformer No. 7 to 10) were housed at the northwestern portion of the building. - The transformer rooms were concrete paved and no stains were observed on the floor. - There is a CLP Substation (labelled as ¡¥CLP Transformer No. 2¡¦) near the Switchgear House. The substation was locked at the time of site inspection and access were not available.	5 sampling locations proposed for Transformer No. 7 to No. 10 and CLP Transformer No. 2. COCs include metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH44 ENV-BH45 ENV-BH46 ENV-BH47 ENV-BH48
	Effluent Pumping Station (619 m^2) + Transformer No. 25 and No. 26	- Four effluent pumps are situated in the station with size approximately 100m^2 (Water pump) - Site supervisor reported turbines that required use of lubricant is on the first floor and, the part based on ground floor is only use as a pipe for water transfer - There are 2 transformers (labelled as Transformer No. 25 to No. 26) near the Effluent Pumping Station. The transformers are on an elevated concrete platform of approximately 0.5m thick. No stains were observed on the floor.	No land contamination was found within the Effluent Pumping Station. 2 sampling locations proposed for Transformer No. 25 and No. 26. COCs include metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH49 ENV-BH50
	Water Reclamation House (312 m^2) + Transformer No. 23 and No. 24	- Major part of the building is used as information centre for visitor. - The remaining portions are used for water reclamation (e.g. ultrafiltration and reverse osmosis system). - There are 2 transformers (labelled as Transformer No. 23 and 24) for the Water Reclamation House. The transformers are on an elevated concrete platform of approximately 0.5m thick. No stains were observed on the floor.	No land contamination was found within the Water Reclamation House. 2 sampling locations proposed for Transformer No. 23 and No. 24. COCs include metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH51 ENV-BH52
	General Area of STSTW (280,000m^2)	-	31 sampling locations, based on 100m sampling grid size, were proposed for STSTW in general. COCs include metals, VOCs, SVOCs and PCRs.	ENV-G1 to ENV-G31
Part of Existing VDC within the Project boundary (approx.36,000m^2) (Inspection Date: 14 Nov 2014 & 30 Nov 2015)	Temporary Storage Area of Spent Batteries (100 m^2)	- The whole area was paved with additional layer of concrete above the concrete ground - No stain and stressed vegetation were observed and no past records of leakage of battery solution.	3 sampling location proposed for the temporary storage area of spent batteries. COCs include metals.	ENV-BH53 ENV-BH54 ENV-BH55
	Storage area of seized goods (100 m^2)	- Only empty containers were stored in the area. - The whole area was concrete paved. - No stain and stressed vegetation were observed and no past records of leakage of chemicals.	3 sampling locations proposed for the storage areas of seized goods. COCs include metals, VOCs, SVOCs, PCRs and PCBs.	ENV-BH56 ENV-BH57 ENV-BH58

6.6 Prediction and Evaluation of Environmental Impacts

6.6.1.1 The STSTW had been operated for over 30 years treating municipal sewage. Preliminary SI works conducted under the Feasibility Study and presented in the CAP did not indicate any contamination exceeding the relevant RBRGs. Together with the fact that a large portion of the STSTW was only vegetation or access roads, extensive contamination is not expected within the site.

6.6.1.2 To determine the extent and nature of any contamination within the STSTW, a total of 71 sampling locations were proposed for the identified hotspots with another 31 sampling locations proposed in the general area of STSTW. As discussed above, the chemicals / chemical wastes stored on-site and of concern included diesel fuel, lubricating oil, transformer oil, mineral oil and organic solvent. The COCs proposed for laboratory analysis included metals, VOCs, SVOCs, PCRs and PCBs. The sampling locations with corresponding hotspots are presented in Table 6.1 and shown in Figure No. 60334056/EIA/6.03. Detail of the sampling of testing requirements are presented in the CAP.

6.6.1.3 For VDC, the potential land contamination concerns are likely restricted to the temporary storage area for the spent batteries and storage area for seized goods, both within the Project boundary. Given the size of the storage areas are small (approximately 100m² for each area) and there were no past records and apparent chemical leakage, extensive contamination within the part of existing VDC within the Project boundary are therefore not expected. The COCs are metals (for the spent batteries storage area) and metals, VOCs, SVOCs, PCRs and PCBs (for the seized goods storage area). The sampling locations with corresponding hotspots are presented in Table 6.1 and shown in Figure No. 60334056/EIA/6.04. Details of the sampling and testing requirements are presented in the CAP.

6.6.1.4 As the existing STSTW and VDC will continue to operate until decommissioning in 2027 and 2017 respectively, the change in operation which lead to any new or relocation of contamination hotspots or occurrence of spillage or accident is not foreseeable, therefore the proposed SI works and any necessary remediation are recommended to be carried out after decommissioning of existing STSTW and part of the existing VDC within the Project boundary but prior to the re-development. Further works, including the submission of supplementary CAP, Contamination Assessment Report (CAR) / Remediation Action Plan (RAP) and Remediation Report (RR), in accordance to EPD¡¦s Guidance Manual, Guidance Note and Practice Guide recommended and discussed in Section 6.7.

6.6.1.5 For the remaining project area, no land contaminating activities associated with current or historical land uses were identified. Land contamination impacts are therefore not anticipated within these areas.

6.6.1.6 Having said that, as David Camp is inaccessible at the time of reporting, further site walkover is recommended to be conducted within the site when access to the camp site is available in order to confirm the presence of any land contamination.

6.6.1.7 In addition to the above and as mentioned in Section 6.4, a surface magazine site at A Kung Kok Shan Road is proposed to be constructed and decommissioned within the Nui Po Shan North during the construction phase of the Project. As it is uncertain at this stage in time whether there would be any land contamination within the site, further site walkover is recommended to be conducted within the surface magazine site before the decommissioning of the site to identify any potential land contamination.

6.6.1.8 Details of the further works for the David Camp and the proposed surface magazine site are also discussed in Section 6.7.

6.6.2 Future Land Uses

6.6.2.1 Land contamination assessment on the potentially contaminated sites would need to be evaluated against the RBRGs and if there were presence of non-aqueous phase liquid (NAPL), soil saturation (Csat) / solubility limits, as stipulated in Table 2.1 and Table 2.2 of the Guidance Manual.

6.6.2.2 The RBRGs were developed based on a risk assessment approach to suit the local environmental conditions and community needs in Hong Kong. Decisions on contaminated soil and groundwater remediation are based on the nature and extent of the potential risks that are posed to human receptors as a result of exposure to chemicals in the soil and/or groundwater. RBRGs were developed for four different land use scenarios as below reflecting the typical physical settings in Hong Kong under which people could be exposed to contaminated soil and groundwater:

¡P Urban residential

¡P Rural residential

¡P Industrial

¡P Public parks

6.6.2.3 For the existing STSTW, the preliminary idea at present is that the site would be used for housing development or other beneficial uses to improve the community and environment. Community facilities and recreation areas such as waterfront promenade would also be considered. The Urban Residential Land Use Scenario (i.e. the more stringent of Urban Residential / Public Parks) is recommended as the land contamination assessment criteria for this type of land uses. However, in case where the re-development include more sensitive land uses (e.g. village-type houses, low-rise residential blocks surrounded by open space and schools), the Rural Residential Land Use Scenario will be appropriate for the assessment. For the existing VDC, as the future land uses had not been determined at this stage in time, the most stringent set of RBRGs is recommended as the land contamination assessment criteria. Referring to Section 6.7 below, a review of the validity of this CAP will be carried out prior to the site investigation works at existing STSTW and part of existing VDC within the Project boundary. A review of the appropriate Land Use Scenario for the land contamination assessment is also recommended to be conducted at the time.

6.6.3 Possible Remediation Measures

6.6.3.1 The actual remediation methods could only be determined after completion of the SI works and EPD¡¦s agreement on the CAR and RAP at the later stage of the Project. The latter will provide details of the remedial actions for the identified contaminated soil and groundwater.

6.6.3.2 Nevertheless, based on the site appraisal, hotspots were identified within the existing STSTW and part of existing VDC within the Project boundary. The potential COCs include metals, VOCs, SVOCs, PCRs and PCBs. For contaminated soil, there are a number of technologies commercially available to tackle the identified COCs. Technologies that are commonly used in Hong Kong are biopiling and cement solidification/stabilization. These ex-situ methods were proven to be effective in treating the target COCs and the treated soil could then be reused on site (e.g. backfilling materials). Given the size of the existing STSTW (approximately 28 ha), there would be sufficient space available to handle and treat the contaminated soil and the two methods are considered to be appropriate for the Project.

6.6.3.3 For groundwater, remediation is not commonly required as contaminants in groundwater seldom exceed the land contamination criteria (i.e. RBRGs) and NAPL do not often present in groundwater. Contaminants in groundwater are often below the respective RBRGs as the potential risks that are posed to human receptors as a result of exposure to chemicals in groundwater is relatively low. This may be due to the fact that according to the EPD¡¦s Guidance Manual, groundwater in Hong Kong were not for drinking purposes and the exposure pathway of contaminants in groundwater to human receptors would be associated with inhalation of volatiles rather than direct exposure. Having said that, there are examples of remediation techniques as shown in EPD¡¦s Practice Guide (e.g. air sparging, recovery trenches / wells, in-ground containment/capping and permeable reactive barriers) that could be applied to this Project if contaminated groundwater were indeed identified.

6.7 Mitigation of Adverse Environmental Impacts

6.7.1 Recommended Further Works

6.7.1.1 As the existing STSTW and VDC will continue to operate until decommissioning in 2027 and 2017 respectively, further assessment and, if required, remediation are recommended to be carried out after decommissioning of existing STSTW and part of the existing VDC within the Project boundary but prior to the re-development. In addition, as the David Camp is inaccessible and the proposed A Kung Kok Shan Road magazine site is yet to be constructed, further site walkover is recommended within the sites when access to the camp site is available and before the decommissioning of the surface magazine site. The further site walkover, assessment and remediation should follow EPD¡¦s Guidance Manual, Guidance Note and Practice Guide and should include the following:

¡P Prior to the commencement of the SI works, review the CAP to confirm whether the proposed SI works (e.g. sampling locations, testing parameters etc.) are still valid and to confirm the appropriate RBRGs land use scenario for the development;

¡P Submit supplementary CAP(s), presenting the findings of the above review for EPD endorsement. If land contamination issues were identified within David Camp and the proposed A Kung Kok Shan Road magazine site in the further site walkover, findings of the site walkover and the proposal for SI works should also be presented in the supplementary CAP(s);

¡P Carry out SI works according to the supplementary CAP endorsed by EPD;

¡P Submit CAR(s), detailing findings of the SI works and nature/extent of any soil/groundwater contamination, and, if contaminated identified, RAP(s) discussing the appropriate remedial methods and mitigation measures, for the identified contamination, for EPD agreement; and

¡P Carry out soil/groundwater remediation works according to EPD agreed RAP and submit RR(s) afterwards for EPD agreement. The remediation works and agreement of RR should be completed prior to re-development.

6.7.2 Mitigation Measures for Remediation Works

6.7.2.1 Mitigation measures for the remediation works would depend on the nature / extent of contamination and the method of treatment. The mitigation measures will be recommended in the RAP and would typically include the following:

¡P Excavation profiles must be properly designed and executed with attention to the relevant requirements for environment, health and safety;

¡P Excavation shall be carried out during dry season as far as possible to minimise contaminated runoff from contaminated soils;

¡P Supply of suitable clean backfill material (or treated soil) after excavation;

¡P Stockpiling site(s) shall be lined with impermeable sheeting and bunded. Stockpiles shall be fully covered by impermeable sheeting to reduce dust emission. If this is not practicable due to frequent usage, regular watering shall be applied. However, watering shall be avoided on stockpiles of contaminated soil to minimise contaminated runoff.

¡P Vehicles containing any excavated materials shall be suitably covered to limit potential dust emissions or contaminated wastewater run-off, and truck bodies and tailgates shall be sealed to prevent any discharge during transport or during wet conditions;

¡P Speed control for the trucks carrying contaminated materials shall be enforced;

¡P Vehicle wheel and body washing facilities at the site¡¦s exist points shall be established and used; and

¡P Pollution control measures for air emissions (e.g. from biopile blower and handling of cement), noise emissions (e.g. from blower or earthmoving equipment), and water discharges (e.g. runoff control from treatment facility) shall be implemented and complied with relevant regulations and guidelines.

6.8 Evaluation of Residual Impacts

6.8.1.1 Further land contamination assessment and, if required, remediation works for the Project Area would need to follow EPD¡¦s Guidance Manual, Guidance Note and Practice Guide and any soil/groundwater contamination would be identified and properly treated prior to the re-development. Land contamination impacts are therefore considered surmountable to future occupants if the recommended actions as outlined in Section 6.7 were followed and contaminated soil and groundwater (if any) were properly treated using appropriate remediation methods and according to EPD¡¦s approved RAP.

6.9 Conclusion

6.9.1.1 Site appraisal was carried out in the period from November 2014 to March 2015 with site walkovers conducted in November 2014 and January / July / November 2015. Based on the site appraisal, the existing STSTW and part of existing VDC (i.e. the temporary works area on Area 73) within the Project boundary are considered to be areas with land contamination concerns.

6.9.1.2 A sampling and testing programme, targeting the existing STSTW and part of existing VDC within the Project boundary had been proposed and documented in the CAP. Based on the latest programme, the existing STSTW and VDC will continue to operate until decommissioning in 2027 and 2017 respectively. Since the site will continue to operate for quite some time, the proposed SI works and any necessary remediation action are recommended to be carried out after decommissioning of existing STSTW and part of existing VDC within the Project boundary but prior to the re-development.

6.9.1.3 In addition, as the David Camp is inaccessible and the proposed A Kung Kok Shan Road surface magazine site is yet to be constructed, further site walkover is also recommended within the sites when access to the camp site is available and before the decommissioning of the surface magazine site to confirm the presence of any land contamination. If land contamination were presence, detailed land contamination assessment and remediation would be required prior to re-development.

6.9.1.4 The further site walkover, assessment and remediation (if any), including the submission of Supplementary CAP(s), CAR(s)/RAP(s) and RR(s) would need to follow EPD¡¦s Guidance Manual, Guidance Note and Practice Guide and according to Section 6.7 of this report.

6.9.1.5 With the implementation of the further site walkover, land contamination assessment and, if required, remediation works for the Project Site, any soil/groundwater contamination would be identified and properly treated prior to the re-development. Land contamination impacts are therefore considered surmountable to future occupants.

<End of Section 6>