6                    LAND CONTAMINATION ASSESSMENT

 

6.1              Introduction

 

6.1.1          Based on the tentative Project programme, the Existing Crematorium will be decommissioned and demolished within the period of October 2006 to November 2007.  Since the Existing Crematorium is a registered pathological incinerator, its decommissioning is classified as a Designated Project under EIAO Schedule 2 Part II (Item 3)

 

6.1.2          Scott Wilson Limited was commissioned by the HKPC as a sub-consultant to carry out an assessment of land contamination at the site of the Diamond Hill Crematorium. 

 

6.1.3          The Contaminated Land Assessment has been carried out in accordance with the guidance given in the following documents:

 

·             Annex 19 of the Environmental Impact Assessment Ordinance – Technical Memorandum

 

·             Practical Note for Professional Persons (ProPECC) Note PN 3/94, “Contaminated Land Assessment and Remediation

 

·             Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards and Car Repair/Dismantling Workshops”, Environmental Protection Department, EPD/TR1/99.

 

6.1.4          A Contamination Assessment Plan (CAP) has been prepared and endorsed by EPD.  This report is included as Appendix C1.  The objectives of the CAP are to:

 

·             Determine the previous landuses of the site

 

·             Outline the current environmental setting of the site, in terms of surrounding landuses, geology and hydrogeology

 

·             Describe the processes carried out at the site

 

·             Identify potential sources of ground contamination

 

·             Outline potential contaminant sources, receptors, and the potential pathways between sources and receptors

 

·             Determine a suitable site investigation strategy to identify, quantify and delineate areas of ground contamination

 

6.1.5          Site investigation works were carried out in March 2003, and the results are documented in the Contamination Assessment Report (CAR) and Remediation Action Plan (RAP) as attached in Appendix C2.  The objectives of the CAR and RAP are to:

 

·             Present the findings of the site investigation

·             Assess the concentrations of contaminants found against relevant criteria

·             Determine the requirement for any remedial works

·             Specify the extent and nature of remedial works

 

6.1.6          Summaries of findings in CAP, CAR and RAP are given below.

 

 

6.2              Geology, Hydrogeology and Hydrology

 

6.2.1          The geology of this part of Kowloon comprises Quaternary colluvial (debris flow) deposits of the Fanling Formation, overlying granite bedrock of the Kowloon Granite Formation.

 

6.2.2          Ground conditions of the project site were found to consist of sandy fill material with rock fragments, to depths of up to 2m below ground level, overlying completely decomposed medium grained granite or colluvium.

 

6.2.3          A watercourse is present immediately to the east of the site, which consists of a natural rocky channel.  Immediately to the south of the site, this watercourse passes into an underground drainage channel, prior to ultimately discharging into Victoria Harbour.  However, during site investigation, no groundwater was encountered.

 

6.3              Current Landuses

 

6.3.1          The site is currently used as a crematorium, and consists of a central building for carrying out services and cremationsand a number of smaller structures such as stores and a CLP secondary substation.  The grounds of the site are landscaped with many trees and shrubs.

 

6.4              Surrounding Landuses

 

6.4.1          The site is bounded to the north and east by cemeteries and grave sites, with Hammer Hill Road also lying to the east of the site.  There are a number of buildings to the west, which include a columbarium for cremated remains and a CLP secondary substation.  Above ground high-voltage electricity cables are situated to the north of the site.  Po Kong Village Road runs along the southwestern edge of the site.  Tate’s Cairn Tunnel passes beneath the area, to the north and west of the site boundary.

 

6.5              Previous Landuses

 

6.5.1          Historical landuses have been determined by examination of historical aerial photographs and site plans and by interviews with current employees.

 

6.5.2          A total of six historical aerial photographs have been reviewed, as listed below:

 

·             81A/177, April 1949;

·             1935 Y72, 1972;

·             14304, June 1976;

·             A18296, September 1989;

·             A35622, July 1993;

·             CN23166, June 1999.

 

6.5.3          The earliest aerial photo indicates that the site was, at this time, predominantly grassed, boulder-strewn hillside.  A number of tracks crossed the site, and the photograph suggests that graves were present to the west and north.

 

6.5.4          By the time of the 1972 photo, the area of graves had spread southwards, over part of the current crematorium site.  The area to the southwest of the site (outside the current site boundary) appears to have been used as a car dismantling and repair facility.  There were a number of buildings in the southeastern corner of the site, comprising the previous Diamond Hill Crematorium and the associated staff accommodation.  The 1976 photo shows the vehicles to the southwest had been removed, and construction work appeared to be underway.  There is an area in the southwest of the current site which consisted of irregular-shaped plots of land, and may represent a squatter area or small agricultural plots.

 

 

6.5.5          Construction of the current crematorium took place between the photos of 1976 and 1989 were taken.  Many of the grave plots shown in earlier photos were covered by the new crematorium development, and the structures in the southeastern corner of the site were also removed.  The basic layout of the crematorium in the 1989 photo was the same as at present.  A large new building is also shown to the northwest of the site.  The layout of the area does not appear to have altered significantly between the 1989 photo and the most recent photo of 1999.

 

6.5.6          A number of drawings have been provided by Arch SD, dating from the construction of the present crematorium in 1977/78.  These drawings indicate the locations of the previous crematorium, the underground fuel storage tank, and the dangerous goods store.  The drawings indicate that considerable earthworks and disturbance of the natural topography should have occurred during these construction works.

 

6.6              Site Walkover Survey

 

6.6.1          A site inspection was carried out on 21st November 2002.  The locations of the dangerous goods store, underground fuel tank and CLP secondary substation were confirmed, although access to the interior of these buildings was not available.  No visible evidence of contamination was noted during this site visit.  A further site visit was undertaken on 11th December 2002, when access to all areas (excluding the CLP secondary substation) was possible. Site operatives were present during the site visits and provided verbal information on current and previous site practices.  This information has been taken account of in determining the likely sources of contamination.

 

6.7              Contaminant Sources

 

6.7.1          On the basis of a review of historical information and current practices, and following the site inspection, the principal potential sources of contamination at the site were identified.  These are associated with the site’s current and former use as a crematorium.  Other land uses within and beyond the site boundary are considered unlikely to give rise to significant contamination within the site.  The locations of potential contaminant sources are shown in Figure 6.1.

 

6.7.2          Facilities or activities which may result in contamination, and the contaminants which may be present, are listed below.

 

Fuel Storage Tank

Potential Contaminants:  

Total Petroleum hydrocarbons (diesel range) (TPH);

Polyaromatic hydrocarbons (PAH).

The fuel tank has been used for storage of diesel rather than petrol, so lighter range petroleum fractions (e.g. BTEX) are not likely to be present.  An underground fuel pipe is believed to lead from the main buried tank to a small tank inside the main building, in the roof space.  The exact alignment of this pipe could not be precisely determined either from the available plans or from the site visit.

       

Dangerous Goods Store

Potential Contaminants:  

Total Petroleum hydrocarbons (diesel range);

Polyaromatic hydrocarbons.

The interior of the Dangerous Goods Store was inspected during the site visit.  The Store has a concrete floor, which appears largely free from staining or cracking.  The contents of the store were found to be mainly non-hazardous items, although a small number of sealed plastic containers thought to contain oil were noted.  There was no visual or olfactory evidence of any contamination within the Store or the immediate vicinity.

 

Electricity Sub-station (on site)

Potential Contaminants:  

Polychlorinated biphenyls (PCBs)

Total Petroleum hydrocarbons

It is not possible to ascertain with certainty whether PCB-containing transformer oils have been used in this CLP secondary substation.  In the absence of further information, it has been assumed that PCBs are potential contaminants in this area.  Sampling beneath the sub-station is not possible whilst the sub-station is still in use, as this would lead to unacceptable safety risks.  Sampling and analysis will be carried out following decommissioning of the sub-station.

 

Areas impacted by aerial deposition from stack emissions

Potential Contaminants:  

Polyaromatic hydrocarbons;

Dioxins;

Metals (“Dutch List”: Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Ba, Hg, Pb)

It is considered unlikely that stack emissions would give rise to significantly elevated concentrations of soil contaminants under normal conditions.  However, the possibility cannot be discounted and hence sampling and analysis was carried out. Aerial deposition of contaminants arising from stack emissions would be greatest in the downwind direction from the stack.  The prevailing wind direction is from east to west, meaning that aerial emissions from the stack would be predominantly carried to the west.  Sampling effort was therefore concentrated to the west of the stack, although confirmatory sampling was also carried out to the north, south and east of the stack.

 

Cremators

Potential Contaminants:  

Polyaromatic hydrocarbons;

Dioxins;

Metals (“Dutch List”: Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Ba, Hg, Pb)

The cremators are situated within the building and above a concrete floor slab.  Since the potential contaminants are predominantly in the solid phase (e.g. particulate matter) it is considered very unlikely that they could migrate through the slab into the underlying soil and sampling and analysis beneath the slab was therefore not considered necessary.  Particulate contamination may however be present within the cremators and flues.

 

Former Crematorium

Potential Contaminants:  

Total Petroleum hydrocarbons;

Polyaromatic hydrocarbons;

Dioxins;

Metals (“Dutch List”: Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Ba, Hg, Pb)

No information is available on the layout or operation of the former crematorium.  The site has undergone considerable disturbance due to site formation for the current facility.  It is not therefore possible to identify specific features of the former crematorium where sampling and analysis is required.  The former crematorium lies at depth within part of the Project site that will undergo minimal disturbance as part of the construction works, and therefore sampling was not considered necessary. 

 

6.8              Site Investigations

 

6.8.1          Exploratory holes were sited to investigate the potential sources of contamination identified above.

 

6.8.2          Intrusive investigations were not carried out beneath the floor slab of the Existing Crematorium building, since it was considered that there is a negligible likelihood that any particulate contamination within the crematorium building could have migrated through the concrete floor slab into the underlying soil.

 

6.8.3          The locations of exploratory holes are shown in Figure 6.2.  The sampling depths and analytical requirements are shown in Table 6.1 below.

 

Table 6.1   Exploratory Holes

 

Location

Exploratory Hole (depth)

Sampling Depths (mbgl)

Analytical Requirements

Fuel storage tank

DH1 (7m)

DH2 (7m)

TP1 (3m) (1)

4.5m; 5.5m; 7m

4.5m; 5.5m; 7m

0.5m; 1.5m; 3m

TPH

PAH

Dangerous Goods store

TP2 (3m)

0.5m; 1.5m; 3m

TPH

PAH

West of stack

S1 (0.1m)

S2 (0.1m)

S3 (0.1m)

0.1m

0.1m

0.1m

 

Metals

PAH

Dioxins

North of stack

S4 (0.1m)

0.1m

South of stack

S5 (0.1m)

0.1m

East of stack

S6 (0.1m)

0.1m

Note: (1) Trial pit TP1 was terminated at 0.9m due to the presence of large boulders preventing further excavation.  Samples were taken from 0.5m and 0.9m depth below ground level.  No evidence of fuel pipelines or fuel contamination was noted in this area.  It is therefore considered that the samples taken from this trial pit are adequate to determine whether contamination is present in this area.

 

6.8.4          Due to operation constraints as described in Section 7.5, the CAP recommended additional site investigations in areas of the site that are currently in use and cannot be readily accessed.  These investigations will be carried out once the existing facility has been decommissioned.  The additional site investigations are required in the vicinity of the existing CLP secondary substation during Phase I of the construction and demolition works, and around the cremators and flues inside the crematorium building during Phase II of the construction and demolition works.  Once access to these areas is available, a sampling and analysis plan will be prepared for approval by EPD, additional investigations will take place, and the need for remedial works will be determined.  Any remedial works required will be in addition to those described in this current report.

 

6.8.5          The Existing Crematorium will continue operation until 2006, and there is the possibility that further contamination could occur between the time of the current investigations (2003) and 2006, particularly as a result of continuing aerial deposition.  It is therefore proposed that, once the Existing Crematorium has ceased operating during Phase II, confirmatory surface samples will be taken from the samples points S1 to S6 at a depth of 0.1m, and these samples will be analysed for the same suite of determinands (i.e. dioxins, metals and PAH) in order to confirm that no further contamination has occurred.  The Remediation Action Plan will be revised on the basis of these results.

 

6.8.6          The underground fuel storage tank and associated pipework will be removed as part of the site formation works.  The base of the excavations will be inspected during and after tank removal by a suitably experienced environmental specialist in order to determine whether there is any visual or olfactory evidence of fuel contamination.  If such contamination is suspected, then confirmatory soil sampling will be carried out, and the samples analysed for TPH.

 

6.9              Assessment Results

 

6.9.1          Total petroleum hydrocarbons, polyaromatic hydrocarbons, metals and dioxins in the soil samples tested fell within the relevant assessment criteria except the following samples:

 

·              S3: lead (180 mg/kg); tin (190 mg/kg)

·              S5: tin (160 mg/kg)

 

6.9.2          Details of the assessment criteria and results are documented in Appendix C2 and summarised in Table 6.2.

 

Table 6.2   Summary of Soil Testing Results

 

Parameter

Units

Assessment Criteria

Range

Dioxin

ng/g, TEQ

1

0.00378 - 0.00894

Silver

mg/kg

NA

<1

Arsenic

mg/kg

30

1.4 - 5.9

Barium

mg/kg

400

5.7 - 50

Beryllium

mg/kg

NA

<1

Cadmium

mg/kg

5

<0.05 - 0.09

Cobalt

mg/kg

50

0.8 - 3

Chromium

mg/kg

250

0.5 - 11

Copper

mg/kg

100

0.5 - 29

Mercury

mg/kg

2

<0.05 - 0.5

Molybdenum

mg/kg

40

<1 - 3

Nickel

mg/kg

100

0.8 - 5

Lead

mg/kg

150

14 - 180

Antimony

mg/kg

NA

<1

Selenium

mg/kg

NA

<1 - 4

Tin

mg/kg

50

<1 - 190

Thallium

mg/kg

NA

<1

Vanadium

mg/kg

NA

1 - 15

Zinc

mg/kg

500

15 - 77

C6-C9 TPH

mg/kg

1000

<2

C10-C28 TPH

mg/kg

1000

<25

C28-C36 TPH

mg/kg

1000

<25

Total PAH

mg/kg

20

<DL - 0.3042

 

6.9.3          Toxicity Characteristic Leaching Procedure (TCLP) tests were carried out on samples S3 and S5, to determine the solubility and mobility of lead and tin in these samples and hence determine the suitability for landfill disposal.  The TCLP test results are shown in Table 6.3.

 

Table 6.3   Results of TCLP Tests for Parameters Exceeding Assessment Criteria

 

 

Lead (ppm)

Tin (ppm)

Landfill Disposal Criteria

50

250

S3

0.03

0.015

S5

<0.01

<0.01

 

6.10          Proposed Remediation Action Plan

 

6.10.1      TCLP testing has been undertaken, and the concentrations of lead and tin in the TCLP tests were several orders of magnitude lower than the Landfill Disposal Criteria.  Hence pre-treatment of the soil prior to landfill disposal is not deemed necessary.

 

6.10.2      The remedial works will consist of removing soil from an area of 5m radius around the sampling locations S3 and S5, to a depth of 0.5m.  The removed soil will then be disposed of at landfill.  Following excavation, confirmatory testing will be undertaken to confirm that all contaminated soil has been removed, and a Remediation Report will be submitted to EPD, detailing the remedial work undertaken.

 

6.10.3      The estimated volume of soil that needs removal is small (less than 100m3), and therefore it is considered that landfill disposal is the most appropriate remedial measure.

 

6.10.4      Summary of the remediation works is shown in the flowchart in Figure 6.3.  Details of the remediation plan (RAP) are provided in Appendix C2.  This includes measures to prevent any adverse water quality impacts during remediation by minimising the possibility of contaminated run-off being generated.

 

6.10.5      During removal of the underground fuel storage tank, appropriate precautions should be taken to avoid contamination.  All fuel tanks and associated pipework should be emptied prior to any demolition work being undertaken.  Any remaining sludge or sediment in the tanks or pipework should be removed and disposed of as chemical waste in accordance with the appropriate regulations for disposal of such material.

 

6.10.6      Should contamination be encountered beneath the fuel tank or the CLP sub-station, further remedial work will be required.  Such potential contamination would consist of either TPH (in the case of the fuel tank) or PCBs (in the case of the CLP secondary substation).

 

6.10.7      Although there is no evidence to date of contamination associated with the fuel tank, and the drillholes around the fuel tank do not indicate contamination, there is the possibility that the material directly underlying the fuel tank may be contaminated with petroleum hydrocarbons.  A realistic worst case estimate is that the volume of contaminated material would be no more than 100m3 (i.e. approximately 7m x 5m x 3m depth).  For this volume of material, treatment by bioremediation is likely to be uneconomic, and the recommended remedial strategy would be landfill disposal.  The actual remedial strategy to be adopted is subject to the findings of the supplementary investigations.

 

6.10.8      The likelihood of significant widespread PCB contamination beneath the CLP secondary substation is considered to be low, due to the low mobility of PCBs in the environment and the low likelihood of a spillage occurring.  As a realistic worst-case estimate, it could be assumed that less than 25m3 (i.e. 5m x 5m x 1m depth) of material could be contaminated, and may require stabilisation with cement prior to disposal to landfill. The actual remedial strategy to be adopted is subject to the findings of the supplementary investigations.

 

6.11          Potential for Future Land Contamination

 

6.11.1      The proposed development is a replacement for the Existing Crematorium.  There is the potential for the development to give rise to land contamination in the future, if appropriate environmental standards are not followed.

 

6.11.2      The most potentially significant future sources of contamination are:

 

·             Spills or leakage of fuel stored for the cremators; and

 

·             Aerial deposition of metals and dioxins.

 

6.11.3      Provided the New Crematorium complies with the prescribed air emissions limits, it is considered very unlikely that aerial deposition would give rise to significant land contamination, due to the very small quantities of metals and dioxins that would be emitted.

 

6.11.4      The fuel storage facilities to be provided in the New Crematorium should be constructed, maintained and inspected in accordance with the provisions of the Dangerous Goods (General) Regulations (Cap. 295B) and the guidelines presented in “Guidance for the Design, Construction, Modification and Maintenance of Petrol Filling Stations” (Institute of Petroleum, 1999), and with the necessary approvals from the Fire Services Department.  To mitigate the environmental impacts from operational land contamination, the following mitigation measures shall be implemented for installation and operation of any underground fuel tanks:

 

·         The underground fuel tank(s) shall be of a specified durability and placed within a concrete pit to avoid direct contact of the tank surface with soil.

·         The concrete pit shall be accessible to allow tank integrity test to be carried out on an annual basis, or when deemed necessary by an independent qualified surveyor or structural engineer. Any potential problems such as potential cracking shall be rectified as far as practicable.

·         Diesel fuel pipelines shall preferably be installed above ground. If underground piping is unavoidable, concrete lined trenches shall be constructed to contain the pipelines. The distance between the cremators and the underground tanks shall be minimized as appropriate to avoid the need for long pipelines.

·         Proper installation and use of meters (e.g. at the two ends of any pipeline) would allow any unexpected pressure drop or difference and signs of leakage be detected from routine inspection or during diesel fuel pumping. Any identified leakage shall be reported to the plant manager in-charge.

·         Any spillage of fuel shall be removed immediately by portable pump when the quantity is large or by absorbing materials when the quantity is low or with similar effective tools as appropriate. Used absorbing material shall be properly stored and disposed of as chemical waste.

·         The underground tanks refueling (from tank trucks) shall only be undertaken by authorized staff of the fuel company using the company's standard procedures to avoid spillage of diesel fuel.

 

6.11.5      Provided the above measures are implemented properly, the likelihood of uncontrolled leakage of fuel giving rise to land contamination is low.  If in the future such facilities are decommissioned, contamination testing will be required in order to identify and delineate any contamination that may have occurred.  No additional land contamination impacts are envisaged during the transitional stage of the project.