6.1
Potentially
contaminated areas have been
identified at the existing Hong
Kong School of Motoring (HKSM) and
City Bus Depot (CBD). As recommended in the EIA report, site investigation
shall be carried out to
determine the presence and extent of contamination before the construction
works take place at the concerned areas. The contamination assessment shall be
carried out in accordance with EPD’s 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”.
6.2
The
contaminated sites shall be remediated before commencement of any construction
work at the concerned sites which may disturb the ground. The duration of
remediation shall be taken into account by the Project Proponent or the
Contractor as part of the construction programme. In all cases, contaminated
soil remediation, treatment or disposal must be managed in an environmentally
sound manner, including compliance with all relevant legislation and Government
requirements.
6.3
For CBD site, the SI has been
undertaken from 31 March to 3 April 2006. The results indicated that heavy metals and Total Petroleum Hydrocarbon (TPH) exceedances were found in 7
sampling locations.
6.4
A
Remediation Action Plan (RAP) has been prepared which essentially recommends
removal of the underground tanks and any local soil contamination around them
as well as replacing the removed material with clean in-fill. Considering the estimated contaminated soil volume is ~150m3, such soil is recommended to be excavated and
disposed of at EPD’s designated landfill site.
6.5
For
the soil with elevated level of heavy metals, Toxicity Characteristic Leaching
Procedure (TCLP) test will be conducted as a further study in order to
determine the leachability (hence the toxic risk) of the soil at the CBD Site.
For a conservative approach, the clean-up strategy (i.e. cement
solidification/stabilisation treatment) has been proposed for the soil
contaminated with arsenic/tin in the RAP.
6.6 For HKSM site, the Contamination Assessment Plan (CAP) which proposed 10 sampling locations for site investigation (SI) has been prepared under this EIA for an illustrative purpose. The party responsible for the SI at the HKSM site in the future would need to separately submit a CAP and Contamination Assessment Report (CAR) (and Remediation Action Plan (RAP), if necessary) to EPD for their approval.
6.7
The CAR should be
prepared to document the findings of the site investigation for the HKSM Site.
Interpretation of laboratory testing results in accordance with the ProPECC Note No. 3/94 and comparison of
the findings with relevant standards, such as the ‘Dutch B’ levels in the Dutch
guidelines or other international practices as appropriate shall be also
included in the CAR.
6.8
If
land contamination is confirmed, a RAP should be prepared and drawn
up to formulate necessary remedial measures. The subsequent CAR and RAP should
be endorsed by EPD before implementation of any remediation works. Any necessary
actions to be carried out at these sites would be the responsibility of the
current site user or responsible parties.
6.9
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.
6.10
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.
Mitigation Measures during Construction Stage
6.11
It is expected that
any identified contaminated land would be remediated to the acceptable
standards prior to site clearance/excavation works. Therefore, no significant
impact in relation to land contamination would be expected. However, as a precaution, mitigation measures are recommended to
minimise the potentially adverse effects on the health and safety of
construction workers and the impacts arising from the disposal of potentially
contaminated materials. These measures include, but are not limited to, the following:
l
Construction
workers’ potential contact with contaminated materials should be minimised by
using bulk earth-moving excavator equipment;
l
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;
l
Stockpiling
of contaminated excavated materials on site should be avoided as far as
possible;
l
The
use of contaminated soil for landscaping should be prohibited unless there is
proper treatment of soil;
l
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;
l
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;
l
Speed
control for the trucks carrying contaminated materials should be enforced;
l
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;
l
Records
of the quantities of wastes generated and disposed of should be maintained; and
l 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.
Mitigation Measures for Remediation Process
6.12
The
following mitigation measures are proposed for biopiling and cement
solidification/stabilisation 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
l
Biopile
should be covered by tarpaulin or low permeable sheet to avoid dust emission;
l
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;
l
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
l
Silencers
should be installed at biopile blower to minimise noise impact;
l
Quiet plant shall be used for biopile treatment
such as generator, blower, etc.
Water Quality Impact
l
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;
l
Mixing
of contaminated soils and cement/water/other additive(s) should be undertaken
at a solidification plant to minimise the potential for leaching;
l
Run-off
from the solidification/stabilisation area should be prevented by constructing
a concrete bund along the perimeter;
Waste
l
The
loading, unloading, handling, transfer and storage of cement should be carried
out in an enclosed system;
l
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.
l
Mixing
process and other associated material handling activities should be properly
scheduled to minimise potential noise impact.
Visual
Impact
l
Temporary hoarding should be provided around the
treatment area in order to minimize the visual impact.
6.13
The
implementation for the recommended land contamination mitigation measures is
presented in Appendix B.