Section 5_ Land Contamination

5 Land contamination

Introduction

5.1 Contaminated land refers to the land which has been polluted by hazardous substances as a result of industrial operations carried out on the site over a number of years. These contaminants if present, may pose hazardous risks or cause adverse effects to the land users and the nearby environment. The implications of land contamination associated with the Phased Reprovisioning of Cape Collinson Crematorium (hereinafter known as “Project”) and its works area (hereinafter called “Study Area”) have been assessed in accordance with the EIA Study Brief (No. ESB-177/2008) in this Section.

Environmental Legislation, Policies, Plans Standards and Criteria

5.2 ”Guidance Note for Contaminated Land Assessment and Remediation” (Guidance Note 1) and “Guidance Notes for Investigation and Remediation of Contaminated Sites of: Petrol Filling Stations, Boatyards, and Car Repair / Dismantling Workshops” (Guidance Note 2) issued by the Environmental Protection Department (EPD) provide guidance on land contamination assessment.

5.3 Further consideration of contamination issues is provided in Section 3 (Potential Contaminated Land Issues) of Annex 19 “Guidelines for Assessment of Impact on Sites of Cultural Heritage and Other Impacts” of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM).

Risk-based Remediation Goals (RBRGs)

5.4 The Guidance Note 2 refers the Risk-based Remediation Goals (RBRGs) as the criteria for land contamination assessment. The “Guidance Manual for Use of Risk–Based Remediation Goals for Contaminated Land Management” (Guidance Manual) which promulgated by EPD on 15 August 2007, presents guidance for interpretating soil and groundwater data in respect to the RBRGs levels developed for post-restoration land use scenarios.

5.5 The Guidance Manual has referred four different post-restoration land use scenarios, 1) Urban residential, 2) Rural residential, 3) Industrial and 4) Public parks. In accordance with the Guidance Manual Section 3, post-restoration land uses for public utilities shall refer to the RGRBs Industrial land use. Receptors for this land use are those at sites where part of the operation is carried out directly on land and the workers are more likely to be exposed to soil.

Assessment Methodology

5.6 In accordance with the above guidance notes, desktop study of historical and current land uses and site appraisal have been conducted to identify any potential land contamination hotspots in the Study Area. According to the findings of site appraisal, a Contamination Assessment Plan (CAP) (Appendix 5.1) was prepared and endorsed by EPD on 2 April 2008. A site investigation was carried out subsequently in accordance with the approved CAP. The results, findings and recommended remedial works were presented in the Contamination Assessment Report & Remediation Action Plan (CAR & RAP) as attached in Appendix 5.2 which has been submitted to EPD for approval on 23 April 2008.

5.7 Possible sources of contamination in the new crematorium and precautionary measures for prevention of future land contamination due to the new operation will also be identified under this Chapter.

Description of the Environment

5.8 The Study Area is located at Cape Collinson Road, Eastern District near Buddhist Cemetery, with site area of about 2000m². The Existing Crematorium consists of four service halls for carrying out ceremonies, two cremation rooms consisting of twelve cremators and several offices.

5.9 The Existing Crematorium is bounded to west and south by six columbarium blocks and Hong Kong Electric substation. Cemeteries and Fung Wah Estate are at the east and north of the Existing Crematorium respectively.

Site Geology and Hydrogeology

5.10 According to the Hong Kong Geological Survey Map (Series: HGM20) – Sheet No. 11 (1:20,000 scale) on the solid and superficial geology of the Study Area, the Study Area is mainly underlain by Shing Mun Formation, undivided sedimentary and volcanic rock consisting of tuffite of Upper Jurassic Period of Mesozoic Era.

5.11 A review of previous ground investigation (GI) reports undertaken at or in vicinity of the Study Area was conducted at the Civil Engineering and Development Department’s (CEDD) Geotechnical Information Library to obtain information about the geological and hydrogeological conditions of the Study Area. Details of the reviewed GI reports are listed below:

· Agreement No. CE 9/95 Feature No. 11SE-D/F19 Chai Wan Ground Investigation Factual Fieldwork Report by Bachy Soletanche Group in 1995. (CEDD’s Geotechnical Information Unit Report No. 21583)

· Slope No. 11SE-D/R2 Regional Council Crematorium, Tai Tam Road, H.K. Ground Investigation Factual Fieldwork Report by Bachy Soletanche Group in 1999. (CEDD’s Geotechnical Information Unit Report No. 30513)

· Agreement No. CE 10/2004 (GE) 10-Year Extended LPM Project, Phase 5, Package D – Hong Kong Island Landslip Preventive Works on Government Slopes and Related Studies – Investigation, Design and Construction Feature No. 11SE-D/C71 Location: Cape Collinson Crematorium Final Factual Fieldwork Report by Fugro Geotechnical Services Ltd. in 2006. (CEDD’s Geotechnical Information Unit Report No. 42859)

5.12 With reference to the above GI reports, the area close to the Study Area is generally covered by a layer of fill materials/colluvium (~0.5m to 1.5m in thickness) composed of sandy SILT and clayey sandy SILT with occasional fine to medium gravel. It is then followed by a layer (~1.15m to 10.1m in thickness) of saprolitic soil (in the majority of fine ash vitric TUFF and sandy SILT) before reaching the lower variable decomposed rock (rock of grade IV with thickness of ~0.4m to 6m). In terms of the likelihood of migration of contaminants, fill materials (i.e. top soil layer) generally have higher permeability and therefore, ability of potential contaminant migration through this horizon is higher than downward migration.

5.13 According to the general topography of the Study Area and groundwater levels recorded in some of the reviewed GI reports, elevation of the groundwater level varies from +153mPD to +110mPD from hillside south to hillside north of the Existing Crematorium. The general groundwater pattern likely flows from south to north, i.e. from Tai Tam Road towards Fung Wah Estate.

Site History

5.14 A review of historical aerial photographs (as shown in Table 5.1) available in the Survey and Mapping Office of Lands Department was undertaken. The aim of this review is to identify the landuses associated with potential contamination implication within or near the Study Area.

Table 5.1 Reviewed Historical Aerial Photographs

Year	Height (Ft.)	Photograph Reference No.
1945	20000	4062
1949	8600	6063
1961	30000	120
1963	2700	6979
1967	6250	5631
1972	13000	2289
1974	12500	9697
1976	4000	12673
1978	4000	23782
1980	4000	29864
1982	4000	40872
1984	4000	53720
1986	4000	A06043
1987	4000	A10339
1989	4000	A17812
1992	4000	A32626
1994	4000	CN6926
1996	4000	CN14150
1998	4000	CN21101
2000	4000	CN28278
2002	3500	CW39611
2004	4000	CW55553
2006	4000	CW72455
2007	3000	CW77143

5.15 As concluded from the review of aerial photographs, the location of the Existing Crematorium was an open area until 1962 and residential houses were found in the location of current Fung Wah Estate. Six columbarium blocks were built successively from 1970s to 1990s. Tai Tam Gap Correctional Institution at the southeast of the Existing Crematorium was also built in 1972. Residential houses were demolished and Fung Wah Estate was built in 1980s. No major land uses changes of the Study Area and surrounding areas were observed since then.

Identification of Sensitive Receivers

5.16 Construction workers and crematorium staffs are the most likely group to be exposed to any potential contaminated material during the construction and operation phases respectively. During the construction phase, workers may be exposed to potential contaminated soil when carrying out excavation and preparation of foundation works. Depending on the nature of the contaminants, hazard during subsurface services may be of concern. The principal exposure routes for workers include:

· Direct ingestion of contaminated soils through eating or drinking/smoking on site; and

· Dermal contact with contaminated soils.

5.17 Given that the contaminated soil would have been remediated in the construction phase, it will unlikely present a residual hazard to the crematorium staffs during their routine operation & maintenance works.

Identification of Environmental Impacts

5.18 There were four service halls for carrying out ceremonies, two cremation rooms with twelve cremators and a number of smaller structures such as offices. The New Cape Collinson Garden of Remembrance opened in December 2007, was situated at the west of the Existing Crematorium.

5.19 A capacity of 15,000L underground storage tank (UST), located at the south of the Existing Crematorium, has been used for diesel storage. The diesel fuel stored in the UST was pumped via the underground pipeline to the aboveground storage tank (AST) which situated at ground floor of the Existing Crematorium serving the cremators thereby by gravity. The exact alignment of the underground pipeline was concealed and could not be visually identified or from the available as-built plans during preparation of the CAP. A utilities plan of the Study Area was later retrieved from the Electrical and Mechanical Services Department (EMSD) after the submission of CAP. According to the site interview with the site person in charge (PIC) from EMSD, no reportable events of leakage concerning the fuel tanks and pipeline were noted.

5.20 Twelve cremators were located in two cremation rooms at the ground floor of the Existing Crematorium. Floors of both cremation rooms were covered by intact ceramic tiles while the cremators were set up on concrete foundation. Diesel fuel was fed to the cremators from the AST via vertical pipelines that ran outside along the wall. The oil pipes ended behind the cremators where their connections were clad in metal plates. Given the limited space and burn hazard from the operating cremator for close inspection, it was unable to access to the pipe joint or coupling where their conditions or any signs of leakage were uncertain. The site PIC from Electrical & Mechanical Services Department (EMSD) expressed that small-scale leakage of fuel from the pipes possibly happened occasionally inside the cremation room. There was no storage of chemicals or dangerous goods were observed and as told by the manager of the Crematorium during site inspection.

5.21 Six chimneys connected to the twelve cremators were located at the top roof of the Existing Crematorium. Some areas around the Existing Crematorium were landscaped with trees and shrubs while other areas were paved with intact concrete. No stain or odour were observed during site inspection. The structural layout is shown in Figure 5.1.

5.22 Site investigations were conducted at the locations near underground storage tank system and around chimneys to evaluate any impact to environment. A contamination assessment report & remediation action plans (CAR & RAP) have been prepared as attached in Appendix 5.2 to discuss the site investigation findings including the fieldworks and laboratory analytical results and recommend appropriate remediation plans for the identified contaminated areas.

5.23 The site investigation (SI) works were carried out from 15 March to 20 March 2008. Four boreholes and five soil surface sampling locations were proposed at the hotspots within the Study Area in accordance with the approved CAP. The locations of the sampling points are shown in Figure 5.2. Results summary of laboratory testing are summarized in Table 5.2. Results exceeded to the relevant RBRGs are highlighted in bold font.

Table 5.2 Laboratory Results Summary

Criteria

VOCs mg/kg

TPH, mg/kg

Heavy Metal, mg/kg

Dioxin, ng/kg

Benzene

Toluene

Ethylbenzene

Xylenes (Total)

C6-C8

C9-C16

C17-C35

Antimony

Arsenic

Barium

Cadmium

Chromium III

Chromium VI

Cobalt

Copper

Lead

Manganese

Mercury

Molybdenum

Nickel

Tin

Zinc

Dioxins (I-TEQ)

Industrial

9.21

10000

8240

1230

10000

261

196

10000

653

10000

1960

10000

2290

10000

38.4

3260

10000

5000

Soil Saturation Limit (Csat)

336

235

138

150

1000

3000

5000

Location

Depth (m)

Sampling Date

From

0.10

14/03/2008

<0.50

6.1

0.10

6.6

<1.0

1.7

9.2

170

<0.05

2.3

3.6

8.32

0.50

14/03/2008

<0.50

2.0

<0.10

1.8

<1.0

2.9

2.4

830

<0.05

<1.0

1.0

3.5

3.92

0.10

14/03/2008

<0.50

4.7

<0.10

6.4

<1.0

1.0

5.8

140

<0.05

2.4

2.7

8.2

2.24

0.10

14/03/2008

<0.50

4.1

<0.10

1.7

<1.0

6.2

1.9

150

520

<0.05

1.2

<1.0

1.3

2.71

0.10

18/03/2008

<0.50

3.2

<0.10

2.5

<1.0

1.7

5.4

210

<0.05

1.5

1.6

3.0

8.58

BH-1

0.50

17/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-1

1.50

1.95

17/03/2008

<0.20

<0.60

<5.0

<200

<500

180000

BH-1

5.50

5.95

17/03/2008

<0.20

<0.60

<5.0

<200

<500

260

BH-2

0.50

17/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-2

2.00

2.45

18/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-2

5.80

6.25

18/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-3

0.50

15/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-3

1.50

2.00

15/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-3

5.50

6.00

15/03/2008

<0.20

<0.60

<5.0

<200

<500

BH-4

0.50

17/03/2008

<0.20

<0.60

<5.0

<200

<500

NA: denotes not applicable

5.24 For the fuel tank system, ten soil samples were collected from four boreholes for laboratory analysis. Among these samples analyzed, only one soil sample from BH-1 at 1.5m to 1.95m bcl having lead content of 180,000 mg/kg exceeds the relevant RBRG (2,290mg/kg). No detectable VOCs or TPHs was reported for all soil samples.

5.25 In accordance with the CAP, one trial pit (TP-1) was proposed underneath the pipeline of the underground fuel tank system. According to the drawing provided by EMSD (presented in the CAR), the existing pipeline is running parallel to the drive at the southwest side of the Study Area, which was possessed by Civil Engineering and Development Department (CEDD) for 10-Year Extended Landslip Preventive Measures (LPM) Project, Phase 5, Package D – Landslip Preventive Works or Slopes in Hong Kong Island project at the time of conducting SI. Access to the proposed trial pit location for sampling could not be obtained during SI. Replies from CEDD and ArchSD are presented in the CAR.

5.26 Hard strata were encountered from 0.6m - 6.25m bcl at BH4. It is believed that contaminants were not likely migrating downwards through the hard strata, therefore only one disturbed soil sample was collected at 0.5m bcl. All soil sampling works were supervised by a qualified land contamination specialist.

5.27 For the surface soil samples, ten soil samples were collected at 0.1m and 0.5m respectively at the five designated surface soil sampling locations (S1-S5) by hand tools. All samples were delivered to the analytical laboratory and should the results of 0.1m soil samples exceed the relevant criteria, analysis for the 0.5m soil samples shall be carried out. According to the laboratory analysis results, no 0.1m samples were found exceeding to the relevant RBRGs in either heavy metals or dioxins. Therefore, no 0.5m soil samples were analyzed.

5.28 No groundwater was encountered for all the sampling location during the course of SI. No groundwater sample was collected for laboratory analysis.

5.29 Since the cremators are still in operation and the proposed trial pit location (TP-1) is possessed by CEDD, it is not possible to carry out site investigation inside the cremation rooms and at TP-1 at this stage. Further site inspection of TP-1 and two cremation rooms will be carried out after decommissioning and prior to the demolition of the existing crematorium. A supplementary CAP will be prepared for EPD endorsement to present detailed sampling and testing plan for two cremation rooms. Further SI of TP-1 will be conducted in accordance with the approved CAP. Findings of site investigation and appropriate remediation methods will be presented in supplementary CAR and RAP for EPD endorsement prior to the commencement of any earthworks. The extent of contamination, if any, should be estimated based on the depth where contaminants found, the hydrogeological condition and the contaminants levels. The actual extent will be determined by confirmatory sampling and testing.

Prediction and Evaluation of Environmental Impacts

Construction Phase

Phase 1 - Construction of New Crematorium

5.30 No surface soil sample has found exceeded the relevant RBRGs Industrial levels for the heavy metals or dioxins. Therefore, no potential environmental impacts due to aerial deposition of contaminants are anticipated during the construction phase.

Phase 2 - Demolition of the Existing Crematorium and Construction of New Crematorium

5.31 Based on the analytical results of soil presented above, soil sample at location BH-1 at the depth of 1.5m to 1.95m bcl has exceeded the relevant RBRG for lead.

5.32 Defining the extent of localised contaminated soils with the consideration of no-contamination results of the adjacent boreholes, a 5m x 5m square encompassing the sampling location BH1 will be adopted.

5.33 The proposed vertical extent of excavation is 0.5m above and below the sampling depth with heavy metals exceeding the relevant RBRG. Figure 5.3 present the estimated contamination extent.

5.34 Based on the above approach, the vertical excavation depth was estimated to be 1.0m -2.45m bcl while the horizontal excavation extent was estimated to be 25m². The overall estimated soil quantity was 37m³. The estimated quality of contaminated soil at the Study Area is summarized in Table 5.3.

Table 5.3 Estimated Quantity of Contaminated Soil

Area

Contaminant

Estimated Contamination Extent

Vertical m bcl

Horizontal (m²)

Quantity of contaminated soil (m³)

BH1

Lead

1.5 - 1.95m bcl

(1.0 -2.45m bcl)

Operation Phase

5.35 Since Towngas will be used as burning fuel instead of diesel, there will be no underground storage tank in the Study Area in the future, therefore, possible leakage or spillage from the underground fuel tank is eliminated.

5.36 The new cremators are designed to be capable of meeting the newly revised requirements described in “A Guidance Note on the Best Practicable Means for Incinerators (Crematoria)” BPM12/2(06), the quantities of metals and dioxins emission will be limited. As no exceedance in dioxin or heavy metals for surface deposition has been found in this Study, and quantities of heavy metals and dioxin emission will be limited with the future cremator design, surface soil contaminated with heavy metal or dioxin by surface deposition is therefore not anticipated.

Mitigation of Adverse Environmental impacts

Construction Phase

5.37 The mitigation measures for the soil contamination are detailed in the CAR/RAP. Soil remediation options applicable to the subject sites were addressed based on the following criteria:

l Technical and cost effectiveness

l Technology development status

l Commercial availability

l Experience

l Expertise requirement

5.38 The applicability/ environmental benefits and limitations/ environmental dis-benefits of the above remediation techniques for lead (heavy metal) contamination soil are detailed in Table 5.4.

Table 5.4 Potential Soil Remediation Technologies

Remediation Measures	Descriptions	Applicability	Limitations
Cement Solidification/ Stabilization	Ex situ immobilization technique treats contaminated soil by mixing soil with binding agents, e.g. cement so that the contaminants become physically bound within stable mass.	l Applicable to clean-up inorganic contaminants, including heavy metals. l Solidification/stabilization has been used on certain contaminated sites in Hong Kong and demonstrated as a successful treatment method for inorganic contaminated soil, e.g. decontamination works at Cheoy Lee Shipyard at Penny’s Bay, reclamation works at North Tsing Yi Shipyard site and few isolated sites identified in the Deep Bay Link project.	l The effectiveness reduces with the presence of organic contaminants (N.B. No organic contaminants were found in the heavy metal contaminated soil in this Study). l Large boulders may hinder the mixing process. Soil sorting is necessary before the treatment taken place. l The process may result in volume increase. l Pilot test is required to set the appropriate ratio of cement to soil for complete immobilization.
Electronkinetic Separation	In situ remediation uses electrochemical and electrokinetic processes to desorb and remove metals and polar organics from soil. Low intensity direct current is applied to the soil to mobilize the charged species.	l Applicable to treat low permeability soil contaminated with heavy metals.	l The effectiveness depends on moisture content of soil. It decreases with moisture content less than 10%. l Require further treatment to remove the desorbed contaminants and thus increase the cost of remediation. l Presence of anomalies such as large gravels and insulating material in soil can induce variability of electrical conductivity in soil. This may reduce the effectiveness.
Excavation and Landfill Disposal	Ex-situ method whereby contaminants are removed by excavation of the contaminated soil and direct disposal to landfill	l Most simple and quickest way to dispose of small volume of contaminated soil l Contamination is removed definitely l Higher certainty of success l Wide experience in Hong Kong Applicable to all waste or mixture that meet land disposal restriction treatment standards. Common practice for shallow, highly-contaminated soils.	l Pre-treatment may be required for contaminated soil to meet landfill disposal criteria l Landfill space limited and valuable. l Indirect costs to the landfill management on monitoring and maintenance. l Potential long-term liabilities to landfill l Need large volume of clean backfill materials No access to the working site until completion of backfilling Least desirable management option.

Remediation Methods for Soil Contaminated with Metals

5.39 Among the remediation methods listed in Table 5.4, soil washing is considered not applicable as extra treatment steps may be required to address hazardous levels of washing solvent remaining in the treated residuals which may increase the cost of remediation. While the electrokinetics method suitable for low permeability soil, the contaminated soil at the Study Area belonged to the high permeable fill type materials, making such method not suitable. In addition, the lack of experience in Hong Kong for electrokinetics remediation methods may also pose difficulties in the remediation process.

5.40 For the solidification / stabilization, the solid monolithic block adopted in this solidification / stabilization technique is extremely resistant to the leaching of inorganic contaminants. Additives can be added to assist in chemically binding the contaminants in a matrix that typically shows unconfined compressive strengths similar to a soil-cement mix. In addition, solidification / stabilization has been used on certain contaminated sites in Hong Kong and as a successful treatment method for inorganic contaminated soil, e.g. decontamination works at the Cheoy Lee Shipyard at Penny’s Bay, reclamation works at North Tsing Yi Shipyard site and few isolated sites identified in the Deep Bay Link project. Based on the above discussion, solidification / stabilization technique is considered as the most practical and cost-effective method to treat the metals contaminated soil on site.

Outline Procedures and Operation of Remediation

Excavation of Contaminated Soil

5.41 The excavation plans for the identified contaminated areas at the Study Area are shown in Figure 5.3. Factors such as excavation areas and depths, engineering properties and stability of the soils shall be considered for safe working conditions. The excavations will be designed in accordance with the geotechnical properties of the soils and appropriate safety factors as determined by the Engineer. All excavated areas will be set out by an appropriate qualified and licensed land surveyor based upon the excavation plans shown in Figure 5.3.

5.42 The excavation sequence would be as follows:

l Excavate the contaminated soil and properly packed until no contaminants are found (confirmed by field and laboratory tests);

l Transport the excavated soil by roll-off trucks for on-site treatment;

l Finally, backfill the excavation with clean soils.

Closure Assessment

5.43 Confirmatory soil sampling for closure assessment should be carried out to confirm the clean-up of the contaminated soil. In general, at least one sample from the base of the excavation pit and four samples from the sidewall should be collected for confirmatory testing. Figure 5.4 presents the proposed confirmatory sampling locations.

5.44 If the analytical results of the confirmatory samples are below the relevant RBRGs lead content, removal of contaminated soil shall be considered complete. If the analytical results exceed the relevant level, excavation shall be extended further (with 0.5m increment in vertical direction and 1.0m in horizontal direction). Further sampling and confirmatory test will be undertaken. The process of excavation, sampling and confirmatory test will continue until all contaminated soils are removed.

Cement Solidification / Stabilisation (CS/S)

5.45 The amount of heavy metal contaminated soil proposed for CS/S treatment in this Study is ~37m³. A treatment area should be confined for carrying out the CS/S mixing and temporary soil stockpile. Prior to solidification, lead contaminated soil should be screened to segregate soil from debris, rock fragment, and other materials and to break soil clumps into sizes to allow effective mixing with solidifying agents.

5.46 During the CS/S process, cement, water and/or other additive(s) should be added to the contaminated soils to form a solid matrix. After setting, the samples of the blocks should be collected for testing to confirm if contaminated materials meet the i) Toxicity Characteristics Leaching Procedure (TCLP) and ii) unconfined compressive strength (UCS) tests i.e. achievement of the stabilization targets.

Toxicity Characteristics Leaching Procedure Test

5.47 TCLP tests should be conducted in accordance with USEPA Method 1311 and USEPA Method 6020 for the concerned metals in this Study. The TCLP test of the CS/S treated soil should comply with the “Universal Treatment Standards” (UTS), as shown in Table 5.5, before using the soil on-site.

Table 5.5 Universal Treatment Standards (UTS) for the Concerned Heavy Metals

Parameters	Universal Treatment Standard
Lead	0.75 mg/L as TCLP

Unconfined compressive strength (UCS)

5.48 The treated material should be allowed to set to achieve the unconfined compressive strength (UCS) of not less than 1 MPa with reference to the USEPA guidelines (1986) – handbook for Stabilisation/Solidification of Hazardous Wastes, EPA/540/2-86-00. The test procedure of UCS test shall be based on BS 1377.

Possible Remediation Methods for Contaminated Soil underneath Pipeline and at Cremation Rooms

5.49 As identified above, the major contamination source due to the pipeline and operation of cremation rooms is likely the leakage of fuel petroleum. Organic contaminants such as TPH and SVOCs are likely found exceeding the relevant RBRGs. If contaminated soil is found underneath the pipeline and at cremation rooms from the further SI, depending on the contamination extent, possible remediation methods for organic contaminants could be excavation and biopiling as well as in-situ soil venting. If the volume of contaminated is found to be small and the aforesaid remediation methods is infeasible and impracticable, excavation and landfill disposal could be considered as last resort. Closure assessment in accordance with paragraphs 5.43 to 5.44 will be carried out in order to confirm the clean-up of contaminated soil. The remediation method should be determined in the supplementary RAP according to the laboratory results and estimated quantity of contaminated soil.

Underground Storage Tank Removal

5.50 During removal of the underground storage tank, appropriate precautions should be taken to avoid contamination. All fuel tank and associated pipelines should be emptied prior to any demolition work being undertaken. Any remaining sludge or sediment in the tanks or pipelines should be removed and disposed of as chemical waste in accordance with the appropriate regulation for disposal of such material. After removal of the underground storage tank, confirmatory soil sample(s) underneath the tank should be collected and tested for TPH, VOCs and Pb using the same approach as mentioned in Sections 5.43 and 5.44 above to ensure that no contamination due to fuel leakage.

Operation Phase

5.51 Provided that all contaminated soils identified are treated before construction of the new crematorium, land contamination impacts due to future operation of new crematorium are not anticipated. Therefore, mitigation measures are considered not necessary in operation phase.

Evaluation of Residual Impacts

5.52 The proposed remediation methods will completely remove contaminants from the Study Area through excavation followed by immobilizing the contaminants by cement solidification/ stabilization and backfilled on site subsequently. After completion of soil remediation, residual impact in respect of land contamination on the future users should not be expected.

5.53 Although potential contamination from pipeline is uncertain, large scale land contamination due to leakage or spillage from the pipeline is not anticipated. Therefore, potential land contamination arising from the pipeline will be localized and in a manageable scale.

5.54 As abovementioned, since possible leakage or spillage of diesel may occur at the Cremation Rooms 1 and 2, further site investigation will be carried out for hydrocarbon related contaminants.

5.55 If in any case that soil is found contaminated with hydrocarbon related product at Cremation Rooms 1 and 2, on-site soil treatment using bioremediation method would possibly be one of the soil remediation option. With implementation of proper remedial actions prior to the commencement of any earthworks, residual land contamination impacts are not anticipated.

Recommended Health and Safety Measures and Environmental Mitigation Measures

5.56 Mitigation measures have been recommended in the RAP for handling of the contaminated materials during the course of site remediation in order to minimise (1) the potentially adverse effects on the health and safety of construction workers and (2) the environmental impacts arising from the handling of contaminated materials.

5.57 The following basic health and safety measures should be implemented as far as possible:

l Set up a list of safety measures for site workers;

l Provide written information and training on safety for site workers;

l Keep a log-book and plan showing the contaminated zones and clean zones;

l Maintain a hygienic working environment;

l Avoid dust generation;

l Provide face and respiratory protection gear to site workers;

l Provide personal protective clothing (e.g. chemical resistant jackboot, liquid tight gloves) to site workers; and

l Provide first aid training and materials to site workers.

5.58 The Contractor for the excavation works shall take note of the following points for excavation:

l Excavation profiles must be properly designed and executed;

l In case the soil to be excavated is situated beneath the groundwater table, it may be necessary to lower the groundwater table by installing well points or similar means. The discharge of groundwater, if any, should follow the requirements under the Water Pollution Control Ordinance (WPCO);

l Excavation zone should be fenced off;

l Quantities of soil to be excavated must be estimated;

l It may be necessary to split quantities of soil according to soil type, degree and nature of contamination;

l Temporary storage of soil at intermediate depot or on-site may be required. The storage site should include protection facilities for leaching into the ground e.g. a liner may be required;

l Supply of suitable clean backfill material is needed after excavation;

l Care must be taken of existing buildings and utilities; and

l Precautions must be taken to control of ground settlement.

5.59 Key potential environmental impacts induced by CS/S processes include:

l Odour, run-off and dust emission from CS/S plant;

l Noise generated from CS/S process.

5.60 The following mitigation measures are recommended to be implemented during CS/S processes.

Air Quality Impact

l The loading, unloading, handling, transfer or storage of cement should be carried out in an enclosed system.

l The loading, unloading, handling, transfer or storage of other materials which may generate airborne dust emissions such as untreated soil and oversize materials sorted out from the screening plant and stabilized soil stockpiled in the designated handling area, should be carried out in such a manner to prevent or minimise dust emissions. These materials should be adequately wetted prior to and during the loading, unloading and handling operations.

l All practicable measures should be taken to prevent or minimize the dust emission caused by vehicle movement.

Noise Impact

l The mixing area should be sited as far as practicable to nearby noise sensitive receivers.

l Simultaneous operation of mixing plants and other equipment should be avoided.

l Mixing process and other associated material handling activities should be properly scheduled to minimise potential cumulative noise impact on nearby noise sensitive receivers.

l Construction Noise Permit should be applied for the operation of powered mechanical equipment, if any, during restricted hours.

Water Quality Impact

l Stockpile of untreated soil should be covered as far as practicable to prevent the contaminated material from leaching out. The leachate should be discharged following the requirements of Water Pollution Control Ordinance.

Waste

l The oversize materials such as rocks and boulders should be screened out, cleaned the soil attached and used as filling material within the site. Contaminated materials (soil or rock fragments) of size smaller than 5 cm should be collected and transferred to the mixing area for decontamination treatment.

l Stabilized soils should be broken into suitable size for backfilling or reuse on site.

l A high standard of housekeeping should be maintained within the mixing area.

l There should be clear and separated areas for stockpiling of untreated and treated materials.

Conclusion

5.61 Site investigation was undertaken for the fuel tank system and aerial deposition from stack emission for land contamination assessment. The result indicated that one soil sample (BH1, 1.5 – 1.95m bcl) was found exceeding to the relevant RBRG for lead. The amount of contaminated soil required remediation is estimated to be around ~37m³.

5.62 Cement solidification/stabilization (CS/S) treatment is proposed for the remediation of ~37m³ soils contaminated with heavy metals in this Study. The treated soils have to meet both the universal treatment standards in the TCLP test and the unconfined compressive strength (UCS) test of not less than 1 MPa before backfilling on site.

5.63 Further site investigation in areas that are currently in use and cannot be accessed is required. These areas include the trial pit for soil sampling underneath the pipeline, Cremation Room 1 and Room 2. It is recommended that further site investigation will be undertaken after decommissioning and prior to the demolition of the existing crematorium.

5.64 A supplementary CAP will be prepared for EPD endorsement to present detailed sampling and testing plan for Cremation Rooms 1 and 2. For site investigation at pipeline, potential contaminants have been identified in the approved CAP and SI shall be conducted in accordance with the approved CAP.

5.65 Findings of further site investigation will be presented in supplementary CAR and supplementary RAP will be prepared, if required, for EPD endorsement prior to the commencement of any earthworks.

5.66 Referring to the site inspection presented in CAP, there is no record of large-scale leakage or spillage at the Study Area. In case of any contamination found related with hydrocarbon product during further site investigation, on-site soil treatment using bio-remediation method could be one of the remedial option.

5.67 As Towngas will be used as burning fuel instead of diesel in the new crematorium, possible leakage or spillage from the underground storage tank and the pipeline system is eliminated. With the new design of cremators which is capable of meeting the newly revised requirements described in “A Guidance Note on the Best Practicable Means for Incinerators (Crematoria)” BPM12/2(06), it is anticipated that aerial deposition would not give rise to significant land contamination.