1.1
Background to the Study
The
Castle Peak Power Company (CAPCO) has initiated a project for emission control
at the Castle Peak Power Station ?units (CPB) (roject?, in response to
the Hong Kong SAR Government (HKSARG) 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 (he 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.
Environmental
Resources Management (ERM) was commissioned by CAPCO to conduct a land
contamination assessment of the site, in accordance with the Study Brief
requirements. A Contamination
Assessment Plan (CAP) was prepared, submitted to and was approved by the EPD
and forms a basis of this assessment.
The
preliminary Project Areas are shown in Figure
1.1a
of the approved CAP.
Site
inspection including soil and groundwater sampling and analysis was conducted
to identify potential sources of contamination from historical and on-going
operations in this area, in accordance with the CAP.
A
Contamination Assessment Report (CAR) summarising the results of the
investigation works and recommending further investigation was prepared (Annex
E1).
1.2
Objectives of the Action Plan
This
Remediation Action Plan (RAP) presents the results obtained during the
contamination investigation at the Project Areas and proposes remediation
actions. The objective of the plan is to reduce
the opportunity for exposure to contaminants during the construction of the Project.
1.3
Scope of the Remediation
The
scope of the remediation will include:
·
Sampling
and testing and, where applicable, treatment and handling/management of the
excavated contaminated soils; and
·
Preparation
of a decontamination verification report upon completion of the demolition,
construction and any necessary decontamination works.
1.4
Structure of the RAP
The
remainder of this document is structured as follows:
Section 2 summarises the site
investigation results; and
Section 3 presents contamination
remediation action plan for the Project Areas.
The
document is accompanied by the CAR in Annex E1.
This
Section
presents the summary of the results of the site investigation works. The full details of the methodology used
for the soil and groundwater sampling works, details of field observations such
as visual observations made during the investigation programme and the
analytical results from soil and groundwater analyses are provided in the CAR, Annex E1.
2.1
Site Investigation Programme
The
Site Investigation (SI) was conducted as described in the CAR and consisted of
drilling of eight boreholes (DH1 to DH8) and four trial pits (TP1 to TP4), the
installation groundwater sampling wells where groundwater was encountered (ie
DH1 to DH8), soil and groundwater sampling, laboratory sample analysis and a
field QA/QC programme. The
locations of the boreholes and trial pits are presented in Figure
3.1a
of the approved CAP.
The
SI programme was designed and carried out in accordance with the EPD Practice Notes for Professional Persons: Contaminated Land Assessment and Remediation ProPECC PN 3/94 and
the Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Stations, Boatyards, and Car Repair/Dismantling Workshops, 1999.
2.1.1
Field Observations
The
underground soil profiles observed during the exploration were recorded using
boring logs (see Annex
E1b
of the CAR).
No obvious sign of hydrocarbon staining,
discoloration or odour was observed in any underlying soil samples and/or groundwater.
No free oil product was observed on
the groundwater surface.
A
soil sample taken from TP3 at a depth 0.9 m below ground level (m bgl), had a reported
total TPH concentration of 1,858 mg/kg ([1]). . This
level exceeds the Dutch ?level for mineral oil (1,000 mg/kg). The concentration was below the Dutch ?
value for mineral oil of 5,000 mg/kg. No soil sample was collected at a deeper level
at the adjacent borehole location (DH5) as the underlying geology comprised of
boulders and fractured granite rock from 0.5 meter below ground level (m bgl)
to the end of drilling at 6.8 m bgl. TPH was not detected in any other soil samples
collected from the Project Areas.
No
target volatile organic compounds (VOCs) including Benzene, Toluene, Ethyl Benzene
and Xylene (BTEX) and semi-volatile organic compounds (SVOCs) were detected at
concentrations exceeding the laboratory reporting limits.
2.1.3
Groundwater
The
static groundwater levels were between 2.4 to 5.5 m bgl (or 1.23 and 2.7 mPD). Based on the groundwater water levels
measured and the local surface hydrology, the shallow groundwater in the Site
area is anticipated to flow in a generally southern or south-westerly direction
and may be influenced by tidal motion in the nearby coastal area.
Light
diesel, heavy diesel and/or heavy oil were detected in groundwater samples
collected from the Site. The sum of
light diesel, heavy diesel and heavy oil concentrations in the groundwater
samples from DH1 to DH7 ranged from 812 (g/L to 3,120 (g/L and exceeded the
Dutch ?value of 600 (g/L for mineral oil. The sum of the light diesel, heavy diesel
and heavy oil fractions in the groundwater sample collected from DH8 was 204
(g/L which is marginally above the ?value (ie 200 (g/L) for mineral oil.
No
free-floating oil product was observed on the groundwater surface.
VOCs and other SVOCs were not detected
in the groundwater samples except di-n-butyl phthalate and bis (2-ethylhexyl) phthalate.
Di-n-butyl
phthalate were detected at concentrations ranging from 31 to 459 (g/L in the groundwater
samples from all groundwater wells whereas bis (2-ethylhexyl) phthalate were detected
at concentrations ranging from 21 to 34 32 (g/L
in the groundwater samples from DH3 and DH5 ([2]).
The phthalates in groundwater
however does not represent a risk for this specific Site as there is no
abstraction of groundwater for any use and there is no exposure to groundwater
under normal circumstances.
2.2
Assessment of
Land Contamination Extent
TPH
in Soil at
TP3
The
concentration of TPH [light diesel (C10-C14), heavy diesel (C15-C28) and heavy oil
(C29-C36)] in soil at TP3 at 0.9 m bgl exceeded the Dutch ?value but was below
the Dutch ?value. As no TPH was
detected in soil at the other sampling locations, the TPH detected
contamination was considered to be localised. As an
extremely worst-case approach, it is The estimated
that amount
of potentially contaminated soil within the Project boundary is 50
m3 of soil
to be excavated near TP3 may be contaminated by TPH.
TPH,
Di-n-butyl
Phthalate
and
Bis
(2-ethylhexyl) Phthalate
in Groundwater
TPH
(light diesel, heavy diesel and heavy oil) contamination at above Dutch ?and
?levels has been reported in all the groundwater samples (DH1 to DH8). The TPH concentrations detected in the
samples from wells DH1 and DH2 were primarily attributable to the light diesel
and heavy diesel fractions. TPH concentrations
at DH3 to DH8 were primarily attributable to the heavy diesel and heavy oil
fractions. Phthalates were found in
the groundwater samples from all groundwater wells (DH1 to DH8) but this does not
represent a risk since groundwater is not abstracted for any use at this Site
and there is no exposure to groundwater under normal circumstances.
The
FODT was located above the ground, has been provided with secondary containment
systems and no oil spills and leakages have been reported or observed during the
site investigation works in this area. An oil pipe leakage near the fuel oil pump
house was reported to the Marine Department and the EPD in July 2004.
The
potential transport mechanism for the TPH, di-n-butyl phthalate and bis
(2-ethylhexyl) phthalate contamination in the groundwater at CPB is the flow of
shallow groundwater, which was measured at about 1.23 to 2.7 mPD. The groundwater flow within CPB is likely
to be influenced by tidal movements as the site is located on a reclaimed area approximately
100 to 400 m from the waterfront.
As
CPB is paved, and groundwater is not used for either domestic or industrial purposes
at CPB and in the adjacent areas, the potential exposure to TPH in groundwater
could only take place during the demolition and construction stages of the
Project. The potential exposure
pathways include dermal contact and accidental ingestion.
With
the implementation of appropriate environmental, health and safety control measures
(as described in Section
3),
no potential adverse impacts are anticipated during the demolition and
construction activities.
2.3
Evaluation of Construction Methods for FGD Plant
2.3.1
Tanks and Oil/Water Separator Sump Demolition
To
accommodate the installation/construction of the proposed Selective Catalytic Reduction
(SCR) and Limestone Flue Gas Desulphurisation (LS-FGD) equipment, demolition works
are required to relocate a number of existing facilities, as described in Section 1.1.
In
addition gypsum storage facilities are proposed to be constructed within the western
coal storage yard.
The demolition
works will take about eight months and are currently scheduled to commence in
early 2007. Excavations for the construction
of foundations are anticipated to commence in around third or fourth quarters
of 2007.
The FODT and the oil separator serving it will be
washed/decontaminated prior to demolition. This will also enable the materials to be
disposed as non-contaminated construction and demolition wastes.
A
total of about 835 tonnes of scrap steel will be produced from the demolition of
the fuel oil day tank, LPG and CO2
tanks, pumps and the associated fixtures/ appendages such as pipeline, spiral stair
and catwalk attached to the tanks. The
steel sheets of the facilities will be cut into small panels for easy
transportation. All the scrap steel
will be transported off-site by barges or lorries for recycling.
A total of
1,830 m3 of
uncontaminated reinforced concrete (after applying a bulking factor of 1.4)
will be generated from the demolition of the fuel oil day tank retaining walls,
DG stores, LPG switch room and vaporiser, LPG tank foundation and pipe
trenches. The concrete is not
contaminated and will be separated from other waste to avoid contamination. The concrete (C&D materials) will be
reused on-site for the subsequent construction within the northern and western
coal yard areas or sent to public filling facilities /other reclamation sites
for reuse.
2.3.2
Excavated Materials
Non-Contaminated
Excavated Materials
Excavation
works would be required for the construction of the piles and shallow
foundations to support the new facilities. A total of about 30,000m3
(after applying a bulking factor of 1.2) of excavated materials (assumed to be mainly
soft materials) will be generated from the demolition of the existing
facilities and excavation for the construction of the foundations for new
facilities.
After
excavating the in-ground foundations and concrete structures, the area will be backfilled
with the excavated uncontaminated soil and imported fill materials to the
existing grade. In addition, excavated
soil will be reused as far as practicable in the Project Area located within
the existing north coal yard which will need to be raised from the existing +5
to +6 mPD to approximately +7 mPD.
Potentially
Contaminated Excavated Materials
Excavation
works will be required at the TP3 area for the construction of the foundations of
an FGD absorber. An estimated total
of 50 m3
of potentially contaminated soil (after applying a bulking factor of 1.2) will
be excavated and treated before reuse within the Project or disposal.
The
excavated potentially contaminated soil will be managed in accordance with the
EPD ProPECC PN 3/94 and Guidance
Notes
for
Investigation and Remediation
of
Contaminated Sites of Petrol filling
Stations,
Boatyards,
and Car/Repair/Dismantling Workshops.
The proposed strategy for the excavation,
testing, remediation and disposal is presented in the following Section
3.
Following
the completion of the land contamination site investigation at the Project
area, the following remediation programmes are proposed.
3.1
Soil Excavation and Confirmation/Verification Sampling
The
only soil contamination identified during the SI programme described in Section 2.1 is
the TPH contamination observed in soil samples at TP3. According to the arrangements in the current
construction plan discussed in Section 2.3.2,
only minor excavation works for the construction of the foundations of the FGD facilities
are expected to be required. Moreover, the existing ground level at
the TP3 location as well as its neighbourhood area will have to be raised by
backfilling with filling materials (excavated or imported) for the installation
of the emissions control facilities.
For
the remediation of petroleum hydrocarbon contaminated soil to be excavated at
TP3, the following steps are proposed:
·
Excavation
of 50 m3
soil around TP3 for
construction of bored piles and pile caps.
·
Temporary
stockpiling of the excavated materials from TP3.
·
The
temporary stockpile will be contained in a container covered by HDPE sheet on top.
·
Conducting
verification sampling for TPH contamination in the soil around the excavated
parcel. The soil samples will be
obtained at each boundary of the excavation parcel at 0.5m, 1m and 1.5 m bgl.
·
Bioremediation
by applying nutrient to the soil will be employed for the on-site treatment of contaminated
soils at a
location within the Project boundary.
Suitable kinds of nutrient will be added
to the soil and the soil will be turned regularly to ensure sufficient air goes
into the soil to undergo biodegradation.
·
Where
the treated soil showed TPH concentrations below the Dutch ?value, the
treatment is considered completed and the soil can be used as fill materials
on-site or disposed of as
fill materials at the public fill bank.
·
If
disposal to the public fill bank is required, vehicles containing any excavated
materials will be suitably covered to limit potential dust emissions or wastewater
run-off, and truck bodies and tailgates will be sealed to minimise the risk of
a discharge during transportation or during wet conditions.
·
Records
of the quantities of soil generated for off-site disposal will be maintained.
·
A
decontamination verification report will be prepared upon the completion of the
decontamination works.
Groundwater
was found to be contaminated in the groundwater samples collected from all
wells with the total TPH at concentrations ranged from 204 to 3,120 (g/L. Di-n-butyl phthalate were detected at concentrations
ranging from 31 to 459 (g/L in the groundwater samples from all groundwater
wells whereas bis (2-ethylhexyl) phthalate were detected at concentrations ranging
from 21 to 34 32 (g/L
in the groundwater samples from DH3 and DH5. There is no abstraction of groundwater at
this Site for any use.
As
such, it is proposed that the following control measures are implemented during
the demolition and excavation to minimise potential environmental impacts from
the groundwater contamination. The following
steps are proposed:
·
Cleaning
of the FODT and the oil separator serving it prior to demolition. Oily water and sludge collected from the cleaning
should be treated at the on-site wastewater treatment facility. Oily water and sludge collected from the cleaning
should be collected and disposed of as
chemical waste at Government chemical waste treatment facility.
·
Only
licensed waste contractors shall be used to collect and transport any chemical
waste. The necessary waste disposal
permits will be obtained, as required, from the appropriate authorities, in
accordance with the Waste
Disposal
Ordinance
(Cap
354) and
Waste
Disposal
(Chemical Waste) (General) Regulation (Cap 354C),
as required.
As
groundwater is not used for either domestic or industrial purposes at the site
or in the adjacent areas, remediation of groundwater is not considered to be necessary
for the Project to proceed. If
groundwater is encountered during the construction of foundations, the
groundwater abstracted or collected will be recharged back to the site.
3.3
Health and Safety Control Measures
The
remediation work will involve soil excavation, soil stockpiling and soil sampling.
To minimise the contacts of the
workers with the contaminated materials and to ensure a safe work environment
during the remediation works, the following control measures are proposed:
·
Prior
to commencing any remediation works, a health and safety risk assessment should
be performed for the remediation works to identify potential work related hazards
and prepare appropriate control measures.
·
Appropriate
Personal Protective Equipment (PPE) such as safety hat, chemical protective gloves,
masks (for both dust and vapour), eye goggles, protective clothing and
protective footwear should be provided to staff who would be involved in the
contaminated area (TP3) remediation works. No works should be allowed without the
suitable PPE.
·
The
workers should inspect and check their PPE before, during and after use. In cases where any of the PPE is
impaired, the workers should stop work immediately and inform their supervisor.
The workers should not be allowed
to re-start their work until the impaired PPE is replaced.
·
The
workers should always maintain basic hygiene standard (eg hand wash before
leaving the contaminated work area). The workers should also be responsible
for cleaning and storing their own PPE in a secure place before leaving the
site.
·
Eating,
drinking and smoking should be strictly prohibited within the contaminated area.
·
The
designated site management representatives must be informed if any workers feel
uncomfortable physically or mentally during the remediation works. All workers should leave the work areas and
the works should be temporarily suspended until the reason for the uncomfortable
feeling has been identified.
·
The
works should be stopped or discontinued when Typhoon Signal No. 3 or Rainstorm
Warnings are hoisted. All stockpile
materials (if any) should be covered immediately by tarpaulin or other similar protective
and waterproof materials.
·
Bulk
earth-moving excavator equipment should be used to minimise construction workers?
potential contact with contaminated materials.
Contents
1 Introduction 1
1.1 Background to
the Study 1
1.2 Objectives of
the Action Plan 1
1.3 Scope of the
Remediation 2
1.4 Structure of
the RAP 2
2 Contamination
Assessment background Information 3
2.1 Site Investigation
Programme 3
2.2 Assessment of
Land Contamination Extent 4
2.3 Evaluation of
Construction Methods for FGD Plant 5
3 Remediation Actions 7
3.1 Soil Excavation
and Confirmation/Verification Sampling 7
3.2 Groundwater Handling 8
3.3 Health and Safety
Control Measures 89
Annex E1 Contamination Assessment Report