7.1
The potential environmental issues associated with land
contamination have been reviewed and are presented in this section. The implications of land contamination for
the proposed land uses at the study area, including Hong Kong
School of Motoring (HKSM), Citybus Depot (CBD) and the existing
Environmental Legislation, Policies, Plans, Standards and
Criteria
7.2
The Practice Note for Professional Persons ProPECC PN3/94 “Contaminated
Land Assessment and Remediation” and “Guidance Notes for Investigation
and Remediation of Contaminated Sites of: Petrol Filling Stations, Boatyards,
and Car Repair / Dismantling Workshops”
issued by the Environmental Protection Department (EPD) provide guidance on
land contamination assessment. The Guidance Notes make reference to
criteria developed in the
7.3
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).
7.4
The methodology adopted in this assessment is in accordance
with EPD’s Practice Note ProPECC PN3/94 “Contaminated
Land Assessment and Remediation” and “Guidance Notes for Investigation
and Remediation of Contamination Sites of: Petrol Filling Stations, Boatyards,
and Car Repair / Dismantling Workshops”.
7.5
Site appraisal was carried out by
reviewing the historical aerial photographs, site inspection, consultation with
relevant Government departments and interview with the existing land
users. All collected information and
inspection findings were analysed thoroughly to evaluate the potential impact
of land contamination associated with the historical/current operations.
Description of the Environment
Baseline Condition
7.6
The current
Site History and Geology
7.7
The site history of the subject sites was
obtained by
reviewing relevant historical aerial photographs. Table 7.1 is a summary of the aerial
photographs reviewed:
Table 7.1 Aerial
Photographs Reviewed
|
Year |
Ref. no |
Height (ft) |
Land use |
|
|
HKSM site |
CBD site |
|||
|
1963 |
6732 |
<4000 |
Farmland |
Farmland |
|
1967 |
5362 |
<4000 |
Farmland |
Farmland |
|
1972 |
1868 |
<4000 |
Farmland |
Farmland |
|
1976 |
12803 |
<4000 |
Open
space |
Open
space |
|
1977 |
20553 |
<4000 |
Car
park |
Open
space |
|
1979 |
26779 |
<4000 |
Car
park |
Open
space |
|
1980 |
29919 |
<4000 |
Car
park |
Open
space |
|
1982 |
45437 |
<4000 |
Car
park |
Open
space |
|
1983 |
47746 |
<4000 |
Car
park |
Open
space |
|
1985 |
A03869 |
<4000 |
HKSM |
Open
space |
|
1987 |
A10402 |
<4000 |
HKSM |
Car
park |
|
1989 |
A17731 |
<4000 |
HKSM |
Car
park |
|
1991 |
A28121 |
<4000 |
HKSM |
Car
park |
|
1996 |
CN15482 |
<4000 |
HKSM |
CBD |
|
1999 |
CN22933 |
<4000 |
HKSM |
CBD |
7.8
The review of available historical aerial photographs
indicated that the HKSM was under construction in 1983 and
in full-scale operation since 1985. The site was undeveloped land before and
used for car parking from 1977 to 1983. Both of the uses identified before 1983
would not cause any contamination concern.
No change of land use is identified at the site after operation of the
HKSM.
7.9
For the CBD Site, the historical aerial photographs
review indicated that the CBD was in place in 1996. The land was
vacant before 1987 and used as a car park from 1987 to 1991. Both of which
would not give rise to land contamination concern. Further information obtained from the site
personnel that the CBD was used as vehicle washing and
refuelling leased by Citybus Limited from the Ocean Park Corporation (OPC)
since 1993. No record of industrial land usage is
identified for the CBD site prior to 1993 nor is there any change of site
activities since the depot operation was commissioned.
7.10
For the existing
7.11
The
Review of Environmental Information from the Government
7.12
Specific information, that is, historical records of
chemical spillage and any violations of environmental regulations, have been
requested from the Fire Services Department (FSD) and the Regional Office
(South) of Environmental Protection Department (EPD).
7.13
There is no record of spillage/ leakage of dangerous goods
stored within the concerned areas.
Both the HKSM and CBD have been registered for Dangerous Goods (DG)
storage and the details are presented in Table
7.2:
Table 7.2 Records
of Current and Past Registration of Storage of Dangerous Goods
|
Name of Licensee |
Date of Issue |
Dangerous Goods Storage Details |
|
Motoring Ltd. |
|
An approved underground tank with capacity
of 18,200 litres for storage of petrol |
|
Citybus Ltd. |
|
Two approved underground tanks
with each capacity of 45,460 litres for storage of diesel |
7.14
The HKSM has been registered as a chemical
waste producer since November 1993. The volume of spent engine oil produced is
about 1,600 to 1,800 litres per year.
There is no record of chemical spillage happened in the past within the
HKSM site.
Identification of Potential Environmental Impacts
7.15
A number of site visits were
conducted from January 2005 to February 2006 to the HKSM, CBD and the existing
The
7.16
A site inspection to the HKSM was conducted in January
Table 7.3 Potential
Contaminative Areas/Activities in the
|
Area/Activity |
Site Descriptions |
Potential Contaminants |
|
Petrol filling station with
underground fuel storage tank |
Unleaded
petrol which is stored in an underground fuel tank is used by the private
vehicles of the motoring school. Two
fuel dispensers were noted and no apparent stain was observed on the paved
ground. |
Petroleum
product |
|
Fuel
interceptors |
Five interceptors are located adjacent to the
underground fuel storage tanks. All
possible spillage during vehicle refuelling is collected through a series of
channels into the fuel interceptor. |
Petroleum
product |
|
Vehicle maintenance workshop |
The
workshop is for maintenance of the private vehicles of the motoring school.
The ground was paved with concrete but the vehicle repairing area was found
with apparent oil stain. |
Paint, chlorinated solvent,
lubricating oil, hydraulic oil |
|
Chemical waste storage
area |
Drums
of oils including hydraulic oil and engine oil were stored at the chemical
waste storage area located at the south east corner of the site. The drums
were placed without drip trays and apparent stains were observed in the drum
storage area. |
Chlorinated solvent,
petroleum product, lubricating oil, hydraulic oil |
Citybus Depot
7.17
A site inspection was conducted at the bus depot on
Table 7.4 Potential
Contaminative Areas/Activities in the Citybus Depot
|
Area/Activity |
Site Descriptions |
Potential Contaminants |
|
Bus
refuelling area with underground fuel storage tanks |
Diesel fuel which is stored in the underground fuel tanks (2 tanks with each capacity of 45,460 litres) is used by the vehicles
of City bus. Five fuel
dispensers were noted and no apparent stain was observed on the concrete paved ground. |
Petroleum product |
|
Diesel
fuel interceptors |
Three interceptors are located adjacent to the
underground fuel storage tanks. All
possible spillage during bus refuelling is collected through a series of
channels into the fuel interceptor. |
Petroleum
product |
|
Vehicle
washing facility |
Mild cleaning solvent is used for vehicle
washing. The water used is collected by the drainage channels around the car
washing facilities and recycled by using the built-in recycling unit. |
Petroleum
product washed out from buses |
Existing
7.18
A site walk-through to the existing
Table 7.5 Potential
Contaminative Areas/Activities in the Existing
|
Area/Activity |
Location |
Site Descriptions |
Sign of Potential Contamination |
|
Lowland |
|||
|
3.3kv
transformer room |
Near
the tennis court |
No apparent stain, no spillage record and no crack observed on the concrete paved ground. The room was tidy and maintained with good housekeeping. |
Nil |
|
DG
storage |
Near
the Country Club |
No apparent stain, no spillage record and no crack observed on the concrete paved ground. The storage was tidy and maintained with
good housekeeping. |
Nil |
|
Plant
rooms (Compressor,
pump, chiller etc.) |
The
dolphin university |
No apparent stain, no spillage record and no crack observed on the concrete paved ground. All rooms were tidy and maintained with
good housekeeping. |
Nil |
|
Headland |
|||
|
Plant
rooms (Compressor,
pump, chiller etc.) |
The
shark aquarium |
No apparent stain, no spillage record and no crack observed on the concrete paved ground. All rooms were tidy and maintained with
good housekeeping. |
Nil |
|
E&M
workshop and chemical storage |
The
dragon |
Small area
(about The workshop
and chemical storage area were tidy and maintained with good housekeeping. |
Minor
spillage indicated by sign of few drips
of lubricant on the concrete slab. |
|
Liquid Propane Gas (LPG) storage area |
Headland
workshop area (in the middle between atoll reef and eagle) |
No apparent stain, no spillage record and no crack observed on the concrete paved ground. All areas were tidy and maintained with
good housekeeping. |
Nil |
|
E&M
workshop |
Nil |
||
|
Chemical
storage |
Nil |
||
|
Plant
room and backup generator |
The
ocean theatre |
The
generator is used for backup service only.
No
apparent stain, no spillage record and no crack observed on the concrete paved ground. The room was tidy and maintained with good
housekeeping. |
Nil |
|
Plant
room (Compressor,
pump etc.) |
The |
The
room was tidy without apparent stain observed and maintained with good
housekeeping. |
Nil |
|
Plant
room (Generator) |
At the
pacific pier |
The room
was tidy without apparent stain observed and maintained with good house
keeping. |
Nil |
Identification of Sensitive Receivers
7.19
Construction workers are the most likely group to be exposed
to any potential contaminated material during the construction stage. Workers may be exposed during excavation and
preparation of foundation works.
Depending on the nature of the contaminants, hazard during preparation
of foundations and 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.
7.20
According to the development
layout plan, part of the existing HKSM site would become the new Ocean Park
Entrance and the existing CBD would become part of the access road and the
public transport drop-off (refer to Figure
7.6).
Visitors to, and staff of,
7.21
Contaminated groundwater would be regarded as a potential
source of water pollution as a result of percolation and infiltration if the
soil contamination was severe.
Contamination
Assessment Plan
7.22
The site area of the HKSM is approximately
7.23
The majority of sampling
locations (i.e. 6 drill holes) are proposed around the hotspots near the underground fuel storage
tanks, underground fuel interceptors, vehicle maintenance area and chemical
waste storage area to investigate any contamination due to fuel seepage or
localised chemical spillage. Additional SI locations (i.e. 4 drill holes) are
proposed at the open ground and the site boundary to assess any migration of
contaminants from the hotspot areas.
7.24
The HKSM site is located on
Government land under the tenancy agreement (No. SHX-13). It is expected (Scenario A) that this site
will be cleaned up by HKSM before handing over to
7.25
As required by the EIA Study
Brief, a Contamination
Assessment Plan (CAP) has been prepared as given in Appendix
7.26
HKSM’s consent for the
preparation of this CAP has not been obtained.
In this sense, the attached CAP (Appendix
Citybus Depot
Contamination
Assessment Plan
7.27
The entire bus depot site is
approximately
7.28
As required by the EIA Study
Brief, a
Contamination Assessment Plan (CAP) has been prepared as given in Appendix 7.1b taking account of all available information. Citybus’s consent for the
preparation and inclusion of the CAP in this EIA Report has been obtained.
7.29
The CBD site falls into the
areas owned by
7.30
The CAP provides detailed information of the proposed
sampling locations as well as a sampling and testing schedule. With reference to the Guidance Notes for
Investigation and Remediation of Contamination Sites of: Petrol Filling
Stations, Boatyards, and Car Repair / Dismantling Workshops
(GN), 10
sampling points are proposed for the contamination investigation at the CBD.
Locations of the proposed SI locations are shown in Figure 7.4.
7.31
Most of the sampling locations
(i.e. 9 drill holes) are proposed near the potential contaminative uses,
including bus refuelling area, underground fuel storage tanks and underground fuel
interceptors. One additional drill hole is proposed near the bus washing
facility.
Site
Investigation
7.32
Envex (HK) Limited (hereafter
called ‘Envex’) has been appointed by Citybus Limited as their Consultant to
conduct the SI in accordance with the CAP (Appendix
7.1b) at the CBD site. The SI has been conducted from
7.33
The sampling strategy used during the SI followed the
principles of the Environmental Protection Department’s “Guidance Notes for Investigation and Remediation of Contaminated Sites
of: Petrol Filling Stations, Boatyards, Car Repair / Dismantling Workshops”, and
also the principles of the Practice Note PN3/94 “Contaminated land Assessment and Remediation”. Soil samples
were obtained using the ‘Trial Pit’ and ‘Bore-Hole’ method and were collected from each of the 10 sampling locations. Three (3) samples were taken vertically from
various depths in accordance with the CAP.
A total of 30 samples were analysed for a range of heavy metals, BTEX
and total petroleum hydrocarbons (TPH) by an approved laboratory.
Result
Analysis and Interpretation
7.34
In order to determine whether or not the ground was
contaminated, the results of the soil analysis were compared with the soil criteria used in The Netherlands for
contaminated land assessments, namely the “Dutch List” of guideline values (in
mg/kg) of A, B and C where the A value is essentially regarded as unpolluted, B regarded as potential pollution,
requiring further investigation or remediation and C regarded as ‘presence of
pollution and necessity for remediation’.
7.35
In
general, elevated concentrations of TPH and heavy metals were noted in the soil
samples. BTEX analysis results did not exceed the “A” values for any of the
soil sampling locations.
7.36
Groundwater was not encountered during the soil
sampling exercise. Migration of contaminants due to hydraulic movement is not
expected.
Heavy Metal
7.37
The results of the soil analysis showed that concentration
of arsenic and tin exceeded the relevant Dutch B values. Except these two metals at those specified locations, the
concentration of the other heavy metals in the soil samples are all acceptably
low. The
exceedance of heavy metals in the soil samples are summarized in Table
Table
|
Borehole |
Sampling Depth (m below ground) |
Parameter |
Dutch “B” Level (mg/kg) |
Concentration (mg/kg) |
|
BH-5 |
4.20 to
4.62 |
Arsenic |
30 |
50 |
|
BH-1 |
4 to
4.45 |
Arsenic |
30 |
34* |
|
BH-3 |
4 to
4.45 |
Arsenic |
30 |
43 |
|
BH-4 |
4 to
4.45 |
Arsenic |
30 |
51 |
|
BH-9 |
4 to
4.45 |
Arsenic |
30 |
86 |
|
BH-9 |
5 to |
Tin |
50 |
63 |
7.38
The presence of arsenic and tin in
the soil samples at elevated levels is probably not due to past site activities
(as open
ground, a car park and most recently as a bus refuelling and washing facility). The
heavy metal distribution is also unlikely caused by surface spillage. Such
discrete soil samples with elevated concentration of
heavy metals are very much localised and are likely due to the naturally occurring minerals in the fill materials.
7.39
According to the development
layout plan, the existing CBD would become part of the access road and the
public transport drop-off (refer to Figure
7.6). The excavation depth for construction
works would be down to a maximum depth of 3m below ground. As such, the
presence of the layer with elevated level of arsenic/tin (~4m below ground)
would be untouched during the construction stage.
7.40
A further study,
Toxicity Characteristic Leaching Procedure (TCLP) testing,
should be conducted in order to determine the
leachability (hence the toxic risk) of the soil with elevated
level of metals at the CBD site. The TCLP test is an international recognized
method for evaluation of heavy metal pollution in soils. This test can give
additional information of the mobility of the heavy metals and hence the
likelihood of metals to be leached out from the soil particles.
7.41
For a conservative approach, clean-up strategy is proposed
for the soil contaminated with heavy metals. It is recommended that the soil materials from the borehole
locations should be removed for a radius of
7.42
The materials above
Table 7.6b Estimated Volume
of Heavy Metals Contaminated Soil for CS/S Treatment
|
Contaminants |
Borehole |
Estimated Horizontal Extent (m) |
Estimated Vertical Extent (m below existing
ground level) |
Estimated
Contaminated Soil Volume (m3) |
||
|
Arsenic |
BH-3 |
|
3.5 to 4.5 |
29 |
||
|
|
BH-4 |
|
3.5 to 4.5 |
29 |
||
|
|
BH-5 |
|
3.5 to 4.5 |
29 |
||
|
Arsenic and Tin |
BH-9 |
|
3.5 to 6.0 |
57 |
||
|
|
|
|
|
|
Total: |
~150 |
TPH
7.43
Elevated TPH
concentrations above the B value of 1,000mg/kg were found at two discrete soil samples
(at separate 2 sampling locations) in the immediate vicinity of the underground
refuelling tanks. Such contamination is
suspected to have been caused by minor fuel spillage from the underground tanks
possibly during installation stage. Soil
remediation at these locations is recommended.
7.44
It is anticipated
that initial excavation for the purpose of extracting the fuel tanks will need
to be at least
7.45
There are two options
recommended for remediation for this quantity of TPH contaminated soil,
including i) biopiling and ii) excavation and disposal.
7.46
Biopiling makes use
of biological processes to turn contaminants into harmless products, ultimately
to carbon dioxide, water and simple inorganic compounds. Biopiling process had
been adopted in previous land contamination projects such as Decommissioning of
Cheoy Lee Shipyards with soil treatment capacity over
7.47
Excavation and
disposal is to remove contaminated soil from the site permanently. This method is relatively quick and ensures
definite removal of contamination, as well as elimination of secondary impact
associated with on-site remediation.
However, the disposal of excavated soils will consume valuable landfill
space if the volume is large.
7.48
Other soil
remediation measures are not further considered because of critical
disadvantages such as long-term liability and no demonstrated local experience
etc.
7.49
The estimated TPH
contaminated soil volume for remediation from CBD site is approximately
7.50
The HKSM site has
different programme for SI and the nature of contamination is not known without
the support of SI results. Biopile co-treatment of the organic contaminated
soils from both CBD and HKSM sites will necessitate storage of contaminated
soil on site. This will lead to environmental risk (e.g. fugitive emission and
leachate) resulting from the extended period required for the stockpiling of
the CBD soil. As such, the option for co-treatment of the contaminated soil
from both sites is considered not practical at this stage.
7.51
A Remedial Action Plan for CBD site has been prepared as given in Appendix 7.3. The portion
under the short term tenancy (No. SHX 844) has also been covered in the CAP.
Site appraisal revealed that no potential contaminative activities have been
carried out at such area. With reference
to the CAR, no exceedance was found at the nearest borehole (i.e. #10) and no
groundwater was encountered throughout the site during the SI. Migration of contaminant through groundwater
movement to that portion of land is not anticipated. Remediation work is thus considered not necessary.
Existing
7.52
All concerned workshops, transformer
rooms, plant rooms, chemical DG storage areas were inspected and most of the
concerned areas were tidy and maintained with good housekeeping. No apparent
stain or ground decolourisation were found at the time of site inspection
except the workshop area adjacent to ‘the Dragon’ within the Park.
7.53
For the E&M workshop and
chemical storage area located near ‘the Dragon’, these areas in general are
kept in good condition by day-to-day housekeeping and only a very small area
was observed with oil stain during the inspection. As revealed by the site
personnel, the workshop only has small- scale maintenance works which involve
limited use of chemicals, lubricants, solvents or paints. No spillage/accident
was recorded. Based on the nature of workshop without heavy machinery works and
the good housekeeping in the chemical storage area/workshop, significant land
contamination in these areas are not suspected. As such, no SI would be
proposed within the existing
Prediction and Evaluation of Environmental Impacts
7.54
Based on the findings of site inspection, potential areas
with land contamination concern have been identified in the HKSM
site. As the HKSM site is still in operation, the land
is currently not available for carrying out the SI to ascertain the extent of
contamination at this EIA stage.
7.55
The implications of potential land contamination for future
development at the HKSM site include:
·
Health and safety concern for workers during site clearance/
construction activities, resulting from potential exposure to hazardous or
flammable materials in soil; and
·
Disposal of potentially contaminated spoil arising from site
clearance or construction works.
7.56
Since the existing land-uses identified are not major
contaminative industry, area-wide contamination causing insurmountable impacts
to the environment is considered very unlikely.
Given that there was never any chemical/ fuel spillage ever recorded
and the site observations also showed without apparent sign of contamination at
this site, it is suspected that only localised contamination caused by small-scale
leakage/spillage might be encountered. The overall land contamination impact
would not be significant and only proper handling of contaminated materials is
required if contamination is identified.
7.57
As noted earlier, HKSM has not given its consent to the
Consultant either to prepare or submit the CAP on their behalf (Appendix
Citybus Depot
Site
7.58
Elevated levels of heavy metals
were found very localised in the fill materials and that level of materials
would be kept untouched during the construction stage, significant impact to
the construction workers would not be expected.
7.59
A further study i.e. TCLP test
will be conducted to assess the leachability of the heavy metals from soil at
the CBD site. For a conservative approach, remediation action i.e. cement solidification/stabilisation
work is proposed for the soil with elevated heavy metal levels. An estimate of
7.60
For the estimated ~150 m3 of TPH contaminated
soil, it is proposed to be
excavated and disposed of at EPD’s designated landfill site. Mitigation measures are proposed to minimise
environmental impacts during soil excavation and transportation, as given in
Section 7.76. Therefore, environmental impact related to contaminated land is
considered insignificant.
Preliminary Programmes for Site
Investigation and Remediation (Alternative Scenarios for HKSM site)
7.61
With Scenario A (which is the expected scenario),
the additional land to be incorporated within OPC’s extended Site is expected
to be handed over in a clean condition. The existing users (i.e.
HKSM) would
fulfil their responsibilities for the SI (described in the CAP) and any
required remediation works within their Site. For Scenario A, no further action from OPC is
required and OPC would subsequently grant access to its
contractors to the Site to begin work.
7.62
An alternative scenario, namely Scenario B,
has been
considered as the “fall-back” option. It would only arise in the event that the
existing user or responsible parties do not hand over the Site
in a clean condition. Under this Scenario, the whole
HKSM site will initially be fenced off and the suspected contaminated area will
be fully demarcated and isolated. The purpose of fencing the site is to restrict access
to ensure there would be no risk to the general public. In order to safeguard the health of both
visitors to
7.63
Following this, OPC undertakes to
carry out, to the extent outstanding, the site investigation (refer to Appendix
7.64
Once the SI results are
available, the potential contaminated area could be identified and the
fenced-off area could be adjusted to isolate only the area of contamination. OPC would ensure that no
work would be undertaken within the fenced off area. OPC
would modify the design of the new entry plaza and access road so as to
accommodate this fenced off area in its layout and to limit access to, as well as
circulation around it.
7.65
Consideration of the extent of any SI works to be undertaken
by OPC to cater for Scenario B would take account of the outcome of any SI and/
or works undertaken by others.
7.66
OPC has reviewed the construction and implementation
programme for the redevelopment and has confirmed that its programme would
accommodate delayed handover to its contractors and that it would proceed with
works in other areas even if portions of the HKSM Site were not available when
expected.
Programme for Site
Investigation
7.67
Given that only limited areas
have been identified as potential contamination area at HKSM site, about 4
weeks time would be required for the SI works including site preparation,
drilling, sampling and testing. Further
4 weeks time is required for reporting (CAR and RAP) and solving comments from
relevant authorities for EPD’s endorsement.
Programme for Remediation
7.68
The major contamination concern at the HKSM Site is the
potential fuel leakage from the underground storage tanks. However, taking into account the known
operation history and relevant tank records without prior release, no bulk fuel
leakage from the underground tanks is anticipated.
7.69
Some recent completed EIA projects with petroleum
contamination by oil tanks have also been referenced to in order to provide
information for possible contamination extent and planning of contamination
material handling and remediation, such as:
l
EIA
Report (EIA-098/2004) for
l
EIA
Report (EIA-119/2005) for Lamma Power Station Units L4 & L5 Flue Gas
Desulphurization Plant Retrofit Project:
l
EIA
Report (EIA-092/2003) Reprovisioning of Diamond Hill Crematorium: The
facility had fuel tanks, DG store and electric sub-station. The SI results
showed no TPH contamination was found around the fuel tank area and only minor
metal contaminated soil of less than
7.70
Based on consultant experience gained from the past projects
involving leaks from underground storage tanks, the contamination would
normally be found at the “smeared” zone (i.e.
Table 7.7 Estimated Volume of Contaminated Soil at Identified
Hotspots in HKSM
|
Site |
Hotspot |
Estimated Horizontal Extent of Contamination (m2) |
Estimated Vertical Extent of Contamination (m) |
Estimate Volume of Contaminated Soil (m3) * |
|
HKSM |
1 underground fuel storage tank |
10 x 10 |
3 |
300 |
|
Chemical waste storage area and vehicle maintenance workshop |
20 x 5 |
1 |
100 |
|
|
Total Estimated Volume of
Contaminated Soil |
400 |
|||
Note: * The actual extent and quantity of contaminated soil
at the site should be subject to SI results.
7.71
The possible
scenarios with proposed remediation methods and duration are summarized in Table 7.8.
In view of the nature of business of HKSM with potential contaminants including
petroleum hydrocarbons and heavy metals, biopiling and/or cement
solidification/stabilisation are proposed for remediation in the unlikely event
of significant contamination found. These two remediation methods have been
proved to successfully treat the soil contaminated by petroleum hydrocarbons or
heavy metals, such as in the decontamination projects of Cheoy Lee Shipyard,
North Tsing Yi Shipyard and the former
Table 7.8 Possible Remediation Options and
Preliminary Remediation Programme For HKSM Site
|
Scenario |
Possible Quantity of Contaminated Soil (1) |
Possible Remediation Options (2) |
Preliminary Remediation Programme |
|
Scenario 1 |
No contaminated soil |
Nil |
Nil |
|
Scenario 2 |
Small volume of contaminated soil |
Landfill disposal |
3 to 5 months (3) |
|
Scenario 3 |
Large volume of contaminated soil which requires for the set-up of
on-site/off-site treatment plant |
Option 1 – On-site treatment by biopiling and/or cement
solidification/stabilisation |
12 to 18 months |
|
Option 2 – Off-site treatment by biopiling and/or cement
solidification/stabilisation |
12 to 18 months |
Notes:
(1) Small volume of contaminated soil is
expected to be a few hundreds cubic meters while the large volume of
contaminated soil is likely more than a thousand cubic meters.
(2) A complete comparison of the pros and cons of all possible
remediation options (plus recommendation) to be provided in the future RAP
submission so as to justify the proposed remediation options and determine the
best feasible option for contaminated soil treatment.
(3) Application of
landfill disposal to Facilities Management Group of EPD is normally required 3
months before disposal. Such application would be made as soon as possible if
excavation and landfill disposal is confirmed for soil remediation.
7.72
Either on-site or off-site
treatment would be considered depending on the site and time availability. The
contaminated soil should be treated by biopile (if TPH exceedance found in the
SI) and/or CS/S (if heavy metals exceedance found in the SI). On-site possible
areas for remediation could be in Tai Shue Wan or the
open space
7.73
Transportation of the
contaminated soil from the HKSM Site to both treatment sites would be by road.
The approximate distances would be of
7.74
The difference
between Tai Shue Wan and the open space near the rest garden are described in Table 7.9 below:
Table 7.9 Comparison between Tai Shue Wan and Open Space near the
|
Location |
Tai Shue Wan |
|
|
Area to be occupied for biopile treatment |
|
|
|
Maximum height of biopile |
|
|
|
Sensitive Receivers |
The existing facilities will be demolished. The space can be used as biopile
treatment. The closest receivers will
be about |
The rest garden is identified as an ASR, which is |
|
Environmental concerns |
Air, Noise, Water, Waste and
Visual |
Air, Noise, Water, Waste and
Visual |
|
Engineering concerns |
Ground level (1% fall shall be provided for the proposed platform, the
area shall also be paved with concrete) Power supply (at least 100kW for the biopile equipment and lighting) Water supply Erect hoarding (with minimal |
Ground level (1% fall shall be provided for the proposed platform, the
area shall also be paved with concrete) Power supply (at least 100kW for the biopile equipment and lighting) Water supply Erect hoarding (with minimal Access road (at least |
Remediation of Contaminated Soil
7.75
The likely amount of contaminated soil, under the reasonably
worst-case scenario, estimated from the best available information and relying
on professional judgment gained from projects having similar type/ likelihood
of contamination is expected to be less than
Mitigation Measures for Land Contamination
7.76
Mitigation measures are proposed for handling of the
contaminated materials in order to minimise (1) the potentially adverse effects
on the health and safety of construction workers and (2) the impacts arising
from the disposal of potentially contaminated materials. These measures for
contaminated material excavation and transportation include:
·
Construction workers’ potential contact with contaminated
materials should be minimised by using bulk earth-moving excavator equipment;
·
Exposure to any contaminated materials should be minimised
by wearing appropriate clothing and personal protective equipment such as
gloves and masks (when interacting directly with suspected contaminated
material), providing adequate hygiene and washing facilities and preventing
smoking and eating during such activities;
·
Stockpiling of contaminated excavated materials on site
should be avoided as far as possible;
·
The use of contaminated soil for landscaping should be
prohibited unless there is proper treatment of soil;
·
Vehicles containing any excavated materials should be
suitably covered to limit potential dust emissions or contaminated wastewater
run-off, and truck bodies and tailgates should be sealed to prevent any
discharge during transport or during wet conditions;
·
Only licensed waste haulers should be used to collect and
transport any contaminated material to an appropriate treatment/disposal site
and procedures should be developed to ensure that illegal disposal of waste
does not occur;
·
Speed control for the trucks carrying contaminated materials
should be enforced;
·
The necessary waste disposal permits should be obtained, as
required, from the appropriate authorities, in accordance with the Waste
Disposal Ordinance (Cap 354), Waste Disposal (Chemical Waste) (General)
Regulation (Cap 35), as required;
·
Records of the quantities of wastes generated and disposed
of should be maintained; and
·
In accordance with good construction practice, silt traps
should be used to reduce the impact to drainage caused by suspended solids
arising from disturbed ground, or any construction materials such as cement and
gravel. Wastewater, surface runoff or extracted groundwater should be disposed of in accordance with the WPCO.
7.77
Key potential
environmental impacts induced by biopiling and CS/S processes include:
·
Odour, run-off and dust emission from biopile and cement solidification/stabilisation
plant;
·
Noise generated from biopile blower and cement solidification/stabilisation process; and
·
Volatile organic
carbons (VOCs) and benzene from biopile emission exhaust.
7.78
The following mitigation measures are proposed for biopiling
and CS/S processes (applicable to both Tai Shue Wan and the open
space near the rest garden) which are the possible remediation actions in
the unlikely event of significant contamination found.
Air
Quality Impact
·
Biopile should be covered by tarpaulin or low permeable
sheet to avoid dust emission;
·
Vented air from biopile should be
connected to blower and carbon adsorption system for treatment before release
to the atmosphere. Exhaust air from the blower and carbon adsorption system
should be monitored regularly;
·
The materials which may generate airborne dust emissions
e.g. untreated contaminated soil should
be adequately wetted prior to and during the loading, unloading and handling
operations;
Noise
Impact
·
Silencers should be installed at biopile blower to minimise
noise impact;
·
Quiet plant shall be used for
biopile treatment such as generator, blower, etc.
Water
Quality Impact
·
Impermeable liners should be placed at the bottom of biopile
and leachate collection sump should be constructed along the perimeter of
biopile to minimise contaminated run-off.
The leachate should be recycled back to the biopile or trucked away to
Chemical Wastes Treatment Centre for disposal;
·
Mixing of contaminated soils and cement/water/other
additive(s) should be undertaken at a solidification plant to minimise the
potential for leaching;
·
Run-off from the solidification/stabilisation area should be
prevented by constructing a concrete bund along the perimeter;
Waste
·
The loading, unloading, handling, transfer and storage of
cement should be carried out in an enclosed system;
·
The contaminated soils should be transported by roll-off
trucks (containerisation). This provides
the most effective way to control the handling of contaminated soil and
minimise the chance of spillage/ leakage during transportation.
·
Mixing process and other associated material handling
activities should be properly scheduled to minimise potential noise impact.
Visual
Impact
·
Temporary hoarding should be
provided around the treatment area in order to minimize the visual impact.
7.79
With implementation of the above proposed mitigation
measures, no adverse environmental impacts would be expected for biopiling and
CS/S process.
7.80
The proposed remediation methods would completely remove
contaminants from the site through excavation followed by disposal, degradation
of the contaminants to non-toxic substances by biopiling or immobilizing the
contaminants by cement solidification/ stabilisation. After completion of soil
remediation, residual impact in respect of land contamination on the future
users should not be expected.
Environmental Monitoring and Audit Requirements
7.81
Details of the environmental monitoring
and audit requirements are provided in Chapter 13 of
this EIA and a stand-alone EM&A Manual.
7.82
An investigation of the historical/current land uses,
including a desk-top review and site inspection, at the Hong Kong School of
Motoring (HKSM), Citybus Depot (CBD) and existing
7.83
The concern of contamination at the HKSM and CBD arises from
the presence of vehicle refuelling/ washing area, vehicle maintenance workshop
and chemical waste storage area. For the
existing
7.84
Two Contamination Assessment Plans (CAP) which detail the
sampling locations and testing schedules of the site investigation (SI) have
been prepared. A total of 20 sampling locations are proposed for the HKSM and
CBD, with 10 sampling points at each site. Citybus Limited has given its consent
to Ocean Park Corporation (OPC) to submit the CAP on their behalf. The CAP
prepared for HKSM under this EIA is for illustrative purpose only. The party
responsible for land contamination SI at the HKSM site in the future would need
to separately submit a CAP for Environmental Protection Department (EPD)’s
approval.
7.85
For CBD site, the SI was conducted from 31 March to 3 April
2006. The results as presented in the CAR indicated that the concentration of
most of the heavy metals in the soil samples are acceptably low except arsenic
and tin at five specified locations. Considering that the elevated levels of
heavy metals are found very localised in the fill materials, the source is
probably not due to the past site activities/surface spillage and the level of
materials would be kept untouched during the construction stage, direct impact
to the construction workers would not be anticipated.
7.86
A further study, Toxicity Characteristic Leaching Procedure
(TCLP) testing, will be conducted in order to determine the leachability (hence
the toxic risk) of the soil with elevated level of metals at the CBD site. For
a conservative approach, clean-up strategy is proposed for the soil
contaminated with heavy metals with details in the Remediation Action Plan
(RAP).
7.87
The soil with elevated level of arsenic/tin (~150 m3)
is proposed to be excavated, treated on site using cement solidification/
stabilisation (CS/S) and backfilled to original position. The mixing procedure
would be carried out within a skip or equivalent. Assuming a production rate of
7.88
Elevated total petroleum hydrocarbon (TPH) concentrations
above the B value of 1,000mg/kg were found in two sampling locations in the
immediate vicinity of the underground refuelling tanks. Soil remediation at
these locations is recommended with details in the RAP. The excavation of BH-2
is proposed to be down to 8m below grade.
The excavation of BH-6 and the remaining area around the tank is
proposed to be down to 6m below grade which equates to maximum soil volume of
about
7.89
For HKSM Site, in view of the current site condition
observed from site inspection, information obtained from Fire Services
Department (FSD)/Environmental Protection Department (EPD) without bulk
spillage/ leakage and nature of business without heavy contaminative activities
involved, only small-scale contamination caused by localised leakage/ spillage
is likely to be encountered. Insurmountable impacts on the surrounding
environment in respect of land contamination would therefore not be
anticipated.
7.90
Based on professional judgement and experience gained from
other similar projects involving leaks from underground storage tanks, the
contamination would normally be found at the “smeared” zone (i.e.
7.91
The SI for HKSM should be conducted as soon as possible
after the site operation ceases. A CAR should be prepared to document the
findings of the SI and identify any need for remediation. If land contamination
is confirmed, a RAP should be drawn up to formulate necessary remedial
measures. The subsequent CAR and RAP should be endorsed by EPD prior to
implementation of any remedial works.
7.92
Different remediation options and associated treatment
programme have been proposed based on the estimated quantity of contaminated
soil and nature of possible contaminants. Both Tai Shue Wan and the open space
near the existing Nam Long Shan rest garden are considered technically feasible
for the proposed remediation works. The CS/S works for heavy metal contaminated
soil is proposed to be carried out in the HKSM site if the soil volume is
small. The biopile and/or CS/S treated soil will be re-used on site.
Appropriate mitigation measures have been recommended to minimise environmental
impacts during soil excavation, transportation and remediation. No adverse
residual impact in respect of land contamination is anticipated if necessary
remediation works are carried out in respect of any identified contaminated
land.
7.93
In the event that the current users or responsible parties
of the HKSM Site do not fulfil its obligations to undertake a CAP, CAR or RAP
or the necessary remediation to the satisfaction EPD, and the site handed-over
to OPC is not totally cleaned (for technical or other reasons), then the whole
HKSM site will initially be fenced off and the suspected contaminated area will
be fully demarcated and isolated. The purpose of fencing the site is to
restrict access to ensure there would be no risk to the general public. Following this, OPC undertakes to carry out,
to the extent outstanding, the site investigation. Such an undertaking does not
relieve the existing users of their obligations to clean the site, nor does it
in any way restrict OPC’s rights to recover the costs of carrying out the SI
works from the responsible parties.
7.94
Once the SI results are available, the potential
contaminated area could be identified and the fenced-off area could be adjusted
to isolate only the area of contamination. OPC would ensure that no work would
be undertaken within the fenced off area. OPC would modify the design of the
new entry plaza and access road so as to accommodate this fenced off area in
its layout and to limit access to, as well as circulation around it.
7.95
OPC has confirmed that the space and time requirements for
contamination investigation and/or treatment of contaminated soil can be
accommodated in the overall design and redevelopment programme for
[1] F.M. von Fahnestock, G.B.
Wickramanayake, R.J. Kratzke and W.R. Major (1998) Biopile Design, Operation, and Maintenance Handbook for Treating
Hydrocarbon-Contaminated Soils, published by Battelle Press.