The Castle Peak Power Company (CAPCO) has initiated a
project for emission control at the Castle Peak Power Station “B” units (CPPSB)
(“Project”), in response to the Hong Kong SAR Government (HKSARG)’s stated
intent to reduce emissions in Hong Kong.
An Environmental Impact Assessment (EIA) Study Brief was issued for the
Project by the Environmental Protection Department (EPD) in October 2005 (EIA
Study Brief No. ESB-134/2005). In
compliance with one of the Study Brief requirements, a land contamination
assessment will be carried out for the Project Areas (“the site”).
To accommodate the new development, extensive
demolition works are required to relocate a number of existing facilities,
including:
·
CPB Fuel
Oil Day Tank (FODT, hereafter referred to as the aboveground fuel oil day tank)
and associated pipe works connecting with fuel oil pump house (FOPH) and oil
interceptor;
·
Dangerous
Goods (DG) stores; and
·
Intermediate
Pressure Reduction Station (IPRS), LPG compound and CO2 storage
tanks.
The preliminary Project Areas are shown in Figure
1.1a.
Environmental Resources Management (ERM) was
commissioned by CAPCO to conduct a land contamination assessment of the site,
in accordance with the Study Brief requirements.
Site inspection including the
sampling and analysis will be conducted to identify potential sources of
contamination from historical and current operations in this area.
This report describes the Contamination Assessment
Plan (CAP) for the land contamination assessment.
The purpose of the CAP is to provide information,
guidance and instruction for characterising land contamination at the proposed
Project Areas. This CAP documents
procedures for identifying land contamination, carrying out the site
investigation and evaluating the results to identify the nature and extent of
contamination at the site. The
specific tasks of the CAP include:
·
Review
of the history of the Project Areas in relation to possible land contamination;
·
Identification
of potential contamination and associated impacts, risks or hazards; and
·
Preparation
of a plan for the actual contamination assessment, which includes a proposal on
soil and, where appropriate, groundwater sampling and analysis, for agreement
with the EPD prior to its implementation.
The findings of the site investigation will be
evaluated and reported in the Contamination Assessment Report (CAR). If the findings confirm that the site is
contaminated, a Remediation Action Plan (RAP) will be prepared and submitted to
EPD for approval.
1.3
Environmental Legislation and Non-statutory
Guidelines
The assessment of land contamination sources and the
potential impacts will be carried out in accordance with the guidelines set out
in the Environmental Protection Department’s (EPD) Practice Note for Professional Person (ProPECC) PN3/94 - Contaminated
Land Assessment and Remediation; and EPD’s Guidance Notes for Investigation and Remediation of Contaminated Sites
of Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshop (Guidance
Notes) and other relevant guidance notes.
Under the Technical
Memorandum on Environmental Impact Assessment Process (EIAO-TM), Annex 19 Guidelines
for Assessment of Other Impacts, consideration should be given during
development and redevelopment projects to a number of potentially contaminating
historical land uses, which have the potential to cause, or have caused, land
contamination. This includes
developing a CAP for the investigation where such land uses are identified,
preparation of CAR after the investigation has been completed, and if
contamination is confirmed, a RAP.
2.1
Site Appraisal and Review of Historical Site
Investigation Data
ERM conducted a walkthrough of
the proposed Project Areas on 16 November 2005 and identified the areas of
potential sources of contamination as follows.
Potential sources of contamination within the Project
Areas:
·
An
aboveground fuel oil day tank, aboveground steel structures of 4,680 tonnes
capacity underlain and surrounded with a concrete bund. Visual inspection of the concrete bund
area showed no evidence of oil leakage or spillage.
·
Dangerous
goods (DG) storage, two one-storey concrete buildings located on concrete paved
ground. Visual inspection of the
concrete floor around the DG stores showed no evidence of oil leakage or
spillage.
·
Intermediate
pressure reduction station (IPRS), LPG compound and CO2 storage
tanks.
Locations of these facilities are presented in Figure
1.1a.
The aboveground
fuel oil day tank (FODT) was surrounded with reinforced-concrete slabs with
bund walls. The bund walls were
designed to provide containment volumes of not less than the maximum operating
capacity of the oil tank and the containment was fitted with drain channels
connecting to a sump pit, where the oil/oily drainage will be further diverted
via a pipeline to a nearby oil interceptor. Visual inspection of the tank and
containment area identified no apparent evidence of oil staining.
According to information provided by CAPCO, oil leakage at
one of the pipelines connecting the FOPH and the FODT inside the pipeline
trench was reported on 29 July 2004 and the oil spill was cleaned up and
written report submitted to Marine Department on 10 August 2004.
2.2
Potential Soil and Groundwater Contamination
Based on the review of site
information and the walkthrough, the potential sources of soil and groundwater
contamination include
the oil and chemical storage
and handling and oil transmission facilities, are described in Section 2.1. The facilities in the Project Areas may
be considered to be potential sources of land contamination due to the
following reasons:
·
Leakage
and/or spillage from the oil tank to the underlying soil and groundwater;
·
Leakage
and/or spillage of chemicals during handling in the DG stores.
The likely contaminants associated with the fuel
storage and transfer facilities include total petroleum hydrocarbons (TPH),
benzene, toluene, ethylbenzene, xylene (BTEX) and polycyclic aromatic
hydrocarbons (PAHs). The likely
contaminants associated with the chemicals (DG stores) storage include total
petroleum hydrocarbons (TPH), volatile organic compounds (VOCs, including
benzene, toluene, ethylbenzene, xylene, BTEX) and semivolatile organic
compounds (SVOCs, including polycyclic aromatic hydrocarbons, PAHs).
The soil and groundwater sampling plan presented in
the following Sections aims to determine the presence and/or extent of soil and
groundwater contamination in the proposed Project Areas.
3.1.1
Sampling Location and Sampling Depths
The sampling locations and depths are recommended
based on the findings of the site appraisal and have made reference to the
guidelines presented in the Guidance
Notes.
The proposed site investigation programme is
described below and is summarised in Table 3.1a.
·
Conduct
a utility scanning and excavation of inspection pits to 1.2m below ground level
(m bgl) to ensure no interference with underground utilities;
·
Eight
(8) boreholes (DH1 to DH8) shall be drilled to 2 m below the groundwater level,
these include:
-
Four
(4) boreholes (DH 4 to DH 7) located within the northern coal storage yard to
the south of the fuel oil day tank, DG stores, FOPH, APS/ADCR building and
IPRS;
-
One
borehole (1) (DH 3) located north of the fuel oil day tank;
-
One
(1) borehole (DH 8) located at the IPRS; and
-
Two
(2) boreholes (DH 1 and DH 2) located within the proposed gypsum dewatering and
storage facilities area in the western coal storage yard.
·
Four
(4) trial pits (TP1 to TP4) located within the northern coal storage yard area
for surface soil sampling;
·
Sampling
of soil for on-site visual investigation and screening using photo-ionisation
detector (PID) from sub-surface (around 0.5 m) and every 1.0 m until the end of
drilling;
·
Three
soil samples shall be collected from each borehole to ascertain the vertical
distribution of any detected contamination ([1]).
It is proposed that samples be taken from the unsaturated zone to below
the groundwater level (eg at between 0.5m to 1m bgl, at soil and groundwater
interface, at 1m below groundwater level) or where there is visual evidence of
contamination;
·
One
soil sample shall be collected from each trial pit to provide additional
information on the surface soil condition;
·
All
eight boreholes will be converted into eight (8) temporary groundwater
monitoring wells to facilitate groundwater sampling ([2]);
·
One
(1) groundwater (GW) sample shall be collected from each monitoring well; and
·
Free-floating
products in groundwater, if observed, will also be collected for laboratory
analysis.
Figure
3.1a shows the proposed
soil and groundwater sampling locations.
With respect to the nature of the substances stored
and used at the fuel oil day tank (medium fuel oil), diesel storage and filling
station (diesel oil), vehicle maintenance workshop (lubricant oils and
solvent), dangerous goods store, where paints and solvents are stored, it is
proposed that the soil and groundwater samples collected will be analysed for
TPH (total petroleum hydrocarbons), benzene, toluene, ethylbenzene, xylene
(BTEX), polycyclic aromatic hydrocarbons (PAHs) volatile organic compounds
(VOCs), and semivolatile organic compounds (SVOCs).
Summary
of analytical parameters are presented in Table 3.1a.
TCLP tests and analysis of leachate for
metal concentrations (as per Landfill Disposal Criteria for
Contaminated Soil listed in the EPD’s Guidance Notes for Investigation
and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards,
Car Repair/Dismantling Workshops) for the material’s suitability for
landfill disposal will be conducted for the samples confirmed to be contaminated.
Table 3.1a Proposed
Site Investigation Programme
|
Location |
Rationale |
Depth |
Temporary Monitoring Well |
# Soil |
# Groundwater Samples |
Analytical Parameters |
|
Borehole/Monitoring Well/Trial Pits |
|
|
|
|
|
|
|
DH1 |
Located
in the northern part of the proposed long-term gypsum storage area |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
BTEX and PAHs Groundwater: TPH,
BTEX and PAHs |
|
DH2 |
Located
in the southern part of the proposed long-term gypsum storage area |
2
m below groundwater level |
1 |
3 |
1 |
|
|
DH3 |
Located
up-gradient from the fuel oil day tank and up-gradient from all proposed
project areas |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) Groundwater: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) |
|
DH4 |
Located
within the north coal storage yard and also down-gradient from the fuel oil
day tank |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
BTEX and PAHs Groundwater: TPH,
BTEX and PAHs |
|
TP4 |
Located
within the north coal storage yard and also down-gradient from the day tank |
Up
to 1.2 m below ground level |
- |
1 |
- |
|
|
DH6 |
Located
within the north coal storage yard |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
BTEX and PAHs Groundwater: TPH,
BTEX and PAHs |
|
DH7 |
Located
within the north coal storage yard |
2
m below groundwater level |
1 |
3 |
1 |
|
|
TP2 |
Located within the north coal storage yard |
Up to 1.2 m below ground level |
- |
1 |
- |
|
|
DH5 |
Located
within the north coal storage yard and down gradient from the DG Stores |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) Groundwater: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) |
|
TP3 |
Located
within the north coal storage yard and down gradient from the DG Stores |
Up
to 1.2 m below ground level |
- |
1 |
- |
|
|
DH8 |
Located
within the current Intermediate Pressure Reduction
Station to be demolished |
2
m below groundwater level |
1 |
3 |
1 |
Soil: TPH,
BTEX and PAHs Groundwater: TPH,
BTEX and PAHs |
|
TP1 |
Located
within the north coal storage yard and down gradient from the current
Intermediate Pressure Reduction Station |
Up
to 1.2 m below ground level |
- |
1 |
- |
|
|
(To be selected on site) |
|
|
1 Duplicate Soil Sample per 20 Soil Samples |
1 Duplicate Groundwater Sample |
As per samples |
|
|
Trip Blank |
|
|
|
Estimated 5 delivery trips (water samples) |
Soil: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) Groundwater: TPH,
VOCs (including BTEX) and SVOCs (including PAHs) |
|
|
Equipment Rinsate |
|
|
|
Estimated 3 (with 3 rigs on-site) (water samples) |
||
|
|
|
|
Total |
30 |
17 |
|
A utility scan will be conducted prior to the commencement
of any excavation/drilling. At each
of the sampling locations, a trial pit will be excavated to 1.2 m bgl. Trial pits will be dug manually using
hand tools and necessary concrete breaking hand operated mechanical tools to
ensure no interference with underground utilities. Sampling below trial pit levels, will be
conducted using drilling rig.
Drilling rigs, drilling equipment that do not come in contact with
samples and hand breakers will be steam cleaned prior to mobilisation to the
site. Prior to sampling, all
sampling equipment and well materials will be steam cleaned, scrubbed with a
non-phosphate soap solution, washed with tap water and rinsed with distilled
water. This procedure will be repeated
after use at each sampling location to avoid potential cross contamination, and
between samples to ensure that any contamination from the surface of the site
does not affect deeper substrata or the groundwater.
In addition to taking samples for analysis, the
strata log will be recorded. This includes
recording the general structure of the ground and the depth and thickness of
each band of material. The depths
at which samples are taken will be recorded with a description of each sample
such as grain size, colour, and wetness.
Extreme care will be exercised when toxic gases or hazardous materials
are suspected. Photographs will be
taken during the site investigation and for each sample.
3.3.1
Sample Collection
The soil or groundwater sampling will be undertaken following
appropriate protocols so as to minimise the potential for cross-contamination
between sampling locations and depths.
The soil sampling methodologies are based on methods developed by US
Environmental Protection Agency (US EPA), as outlined below.
Decontamination Procedures
Sampling equipment used during the course of the site
investigation programme will be decontaminated using the following procedures:
·
Manual
washing and scrubbing with non-phosphate detergent;
·
Tap
water and distilled water rinse; and
·
Air
drying.
Where available, a steam cleaner or pressure washer
will be used.
During the sampling and decontamination activities,
disposable latex gloves will be worn to prevent transfer of contaminants from
other sources. Any disposable
equipment such as latex gloves will be disposed of as general waste after each
use. Provisions will be made to
containerise any decontamination fluids, although the volume of fluids to be
produced is expected to be low.
Soil Sample Collection
Soil samples will be taken by ERM staff and placed
into appropriate clean glass bottles or sampling containers (provided by the
laboratory) immediately after collection.
Before sampling commences, the laboratory will be consulted on the
particular sample size and preservation procedures that are necessary for each
chemical analyses. The sample
containers will be laboratory cleaned, made of glass or other suitable
materials with aluminium or teflon-lined lids, so that the container surface
will not react with the sample or adsorb contaminants. The containers will be labelled with the
sampling location codes and the depths at which the samples are taken. They will then be transferred to an
icebox or cooler container. Samples
will be kept between 0 to 4°C but not frozen.
Groundwater, if encountered, will be sampled from the
monitoring wells using disposable Teflon bailers.
Sampling Management
Samples will be dispatched to the analytical
laboratory for analysis as soon as practicable following sampling. All samples will be handled under chain
of custody protocols and relinquished to the laboratory representative at the
site or at a location specified by the laboratory.
The parameters as described in Section 3.2 will be analysed using the methods stated in Table 3.4a.
Table 3.4a Analytical
Methods for Contaminants in Soil and Groundwater Samples
|
Contaminant |
Analytical
Methods |
|
TPH |
·
|
|
VOCs (incl. BTEX)/SVOCs (incl. PAHs) |
·
US EPA Method
8260/8270 |
|
TCLP |
·
EPA
SW-846 (Method 1311) |
3.5
Quality Control and Quality Assurance (QC/QA)
Samples collected should be representative of field
conditions. At each sampling
location, soil (and groundwater, if encountered) samples will be collected using
pre-cleaned sampling equipment. All
sample containers will be provided by the contracted laboratory who guarantees
their sterilisation and preservative contents.
Appropriate QC/QA samples will also be collected
during the field investigation, including:
·
Equipment
(rinsate) blanks (one per machine) for the full suite of target parameters, in
order to assess the adequacy of the decontamination procedures;
·
Trip
blanks (one per cooler/shipment) for the full suit of target parameters in
order to assess the potential contamination of the sample handling and
transportation processes; and
·
Groundwater
and soil duplicates (one duplicate sample per 20 samples) for the full suite of
analyses to assess the precision of the procedures.
Precision will be calculated as the relative percent
difference (RPD) between the original sample and the blind duplicate. For water and soil, the acceptance
criteria for precision are 20% RPD and 30% RPD, respectively. Accuracy will be assessed by analysis of
blank samples to ensure that no bias is present in the analytical data.
Analysis of samples will be carried out by an
appropriate, HOKLAS-certified (or other equivalent scheme approved by the EPD)
analytical laboratory. The
laboratory should maintain high standards of analytical and technical services
for the detection of trace organic contaminants. All analysis will be conducted according
to standard procedures set by the US EPA, along with internal QC/QA procedures.
A health and safety risk assessment and health and
safety management plan shall be developed for the site investigation works in
accordance with CLP Power HK Ltd (CLP) and ERM’s internal requirements. All personnel will attend safety
training provided by CLP prior to commencing the works at the site.
It is anticipated that site investigation and
laboratory analysis will be completed within three to four weeks from the date
of approval of the CAP. The CAR will
be submitted to the EPD for approval after the completion of the laboratory
analysis.
The overall assessment will comprise the following
activities:
·
Required
revision and endorsement of the CAP by EPD;
·
Mobilisation
of the subcontractor and contracting analytical laboratory;
·
Field
sampling programme;
·
Analytical
programme/laboratory turnaround (normal turnaround time is expected two weeks);
·
Assessment
and reporting of results in a CAR, including, if required, development of a
remedial action plan (RAP). The CAR
will include all laboratory testing results of chemical analyses; and
·
In
the event that landfill disposal is proposed for contaminated soil materials,
prior agreement will need to be reached with the EPD and the application
accompanied by the RAP and the TCLP test results.
No demolition works involving excavation will be
conducted at the project area before the assessment and the necessary
remediation works have been established.
A CAR will be prepared after obtaining analytical
results from the laboratory. The
report will present the findings of the CAP and site investigation assessment
(including the methodology used during the soil and groundwater sampling and
details of field observations such as visual observations made during the
investigation).
There are no legislative standards requiring clean up
of soil and groundwater contamination in
CAPCO notes that Dutch “B” values are currently being
adopted as the cleanup targets for most of the land decontamination cases in
The CAR will be prepared and submitted to the EPD.
If necessary, a RAP will be prepared in consultation
with the EPD, with the objective of mitigating the site to an agreed upon
condition. Any proposed mitigation
recommendations will be considered under several factors including nature of
the contamination, degree of the contamination, the potential receiver, time
allocation, treatment cost and availability of local expertise for undertaking
the treatment in accordance with the ProPECC PN3/94 and other relevant
guidance notes. The RAP will also
outline requirements for construction workers to follow to limit potential
future exposures.
The results of the sampling programme, the report,
and the objectives of the RAP will be submitted to EPD. It should be noted that no estimate of
the time frame for any mitigation is presented at this time.
([1]) In accordance with the ProPECC PN 3/94 and the Guidance Notes.