7.1
The
water quality impact assessment indicated that no adverse water quality impact
would be expected from the proposed construction and demolition activities,
with implementation of recommended mitigation measures as described in Section
8 of the EIA Report. During operational phase, as “dry” process
will be adopted for the Air Pollution Control equipment in the new crematorium,
no effluent will be discharge and hence no adverse impact will be generated on
water quality.
7.2
Regular
site inspection shall be undertaken to inspect the construction activities and
works area in order to ensure that the mitigation measures are properly
implemented. Monitoring of the construction site effluent shall be carried out
in accordance with the WPCO license which is under the ambit of regional office
of EPD. Marine water quality monitoring is not necessary since no off-site
water quality impact is expected.
Site Inspections
7.3
Site
inspections shall be carried out by the ET and shall be based on the
recommended mitigation measures for water pollution control. In the event that
the recommended mitigation measures are not fully or properly implemented,
deficiency shall be recorded and reported to the site management. Suitable actions are to be carried out to:
·
Record the problems and investigate the
causes;
·
Issue action notes to the Contractor who is
responsible for the works;
·
Implement remedial and corrective actions
immediately;
·
Re-inspect the site conditions upon
completion of the remedial and corrective actions; and
·
Record the event and discuss with the
Contractor for preventive actions.
Compliance Audits
7.4
Compliance
audits are to be undertaken to ensure that a valid discharge license has been
issued by EPD prior to the discharge of effluent from the Project site. If
monitoring of the treated effluent quality from the Works Areas is required
during the construction phase of the Project, the monitoring should be carried
out in accordance with the WPCO license which is under the ambit of regional
office (RO) of EPD. The audit results reflect whether the effluent quality is
in compliance with the discharge license requirements. In case of
non-compliance, suitable actions by the relevant parties should be undertaken
to:
·
Notify the site management on the
non-compliance;
·
Identify the sources of pollution;
·
Check the implementation status of the
recommended mitigation measures;
·
Investigate the operating conditions of the
on-site treatment systems;
·
Implement corrective and remedial actions
to improve the effluent quality;
·
Increase monitoring frequency until the
effluent quality is in compliance with the discharge licence requirements; and
·
Record the non-compliance and propose
preventive measures.
7.5
Mitigation
measures for water quality control have been recommended in the EIA Report and
summarized below. The implementation
schedule of the recommended water quality mitigation measures is presented in Appendix
A.
Demolition and Construction Works
7.6
The
Contractor shall responsible for the implementation of the site practices as outlined
in the ProPECC PN1/94 to minimise surface runoff and the chance of erosion.
These practices include the following items:
Surface Run-off
7.7
Surface
run-off from construction sites should be discharged into storm drains via
adequately designed sand/silt removal facilities such as sand traps, silt traps
and sedimentation basins. Channels or
earth bunds or sand bag barriers should be provided on site to properly direct
stormwater to such silt removal facilities.
Perimeter channels at site boundaries should be provided where necessary
to intercept storm run-off from outside the site so that it will not wash
across the site. Catchpits and perimeter
channels should be constructed in advance of site formation works and
earthworks.
7.8
Silt
removal facilities, channels and manholes should be maintained and the
deposited silt and grit should be removed regularly, at the onset of and after
each rainstorm. Any practical options
for the diversion and re-alignment of drainage should comply with both
engineering and environmental requirements in order to provide adequate
hydraulic capacity of all drains.
7.9
Construction
works should be programmed to minimize soil excavation works in rainy seasons
(April to September). If excavation in
soil could not be avoided in these months or at any time of year when
rainstorms are likely, for the purpose of preventing soil erosion, temporary
exposed slope surfaces should be covered e.g. by tarpaulin, and temporary
access roads should be protected by crushed stone or gravel, as excavation
proceeds. Intercepting channels should
be provided (e.g. along the crest / edge of excavation) to prevent storm runoff
from washing across exposed soil surfaces.
Arrangements should always be in place in such a way that adequate
surface protection measures can be safely carried out well before the arrival
of a rainstorm.
7.10
Earthworks
final surfaces should be well compacted and the subsequent permanent work or
surface protection should be carried out immediately after the final surfaces
are formed to prevent erosion caused by rainstorms. Appropriate drainage like intercepting
channels should be provided where necessary.
7.11
Measures
should be taken to minimize the ingress of rainwater into trenches. If
excavation of trenches in wet seasons is necessary, they should be dug and
backfilled in short sections. Rainwater
pumped out from trenches or foundation excavations should be discharged into
storm drains via silt removal facilities.
7.12
Open
stockpiles of construction materials (e.g. aggregates, sand and fill material)
on sites should be covered with tarpaulin or similar fabric during
rainstorms.
7.13
Manholes
(including newly constructed ones) should always be adequately covered and
temporarily sealed so as to prevent silt, construction materials or debris from
getting into the drainage system, and to prevent storm run-off from getting
into foul sewers. Discharge of surface
run-off into foul sewers must always be prevented in order not to unduly
overload the foul sewerage system.
Groundwater
7.14
Groundwater
pumped out of wells, etc. for the lowering of ground water level in basement or
foundation construction should be discharged into storm drains after the
removal of silt in silt removal facilities.
Boring and Drilling
Water
7.15
Water
used in ground boring and drilling for site investigation or rock / soil
anchoring should as far as practicable be recirculated after
sedimentation. When there is a need for
final disposal, the wastewater should be discharged into storm drains via silt
removal facilities.
Wastewater from
Concrete Batching and Precast Concrete Casting
7.16
Wastewater
generated from the washing down of mixing trucks and drum mixers and similar
equipment should whenever practicable be used for other site activities. The discharge of wastewater should be kept to
a minimum and should be treated to meet the appropriate standard as specified
in the Technical Memorandum on Standards for Effluents Discharged into Drainage
and Sewerage Systems, Inland and Coastal Waters (TM-DSS) before discharging.
7.17
To
prevent pollution from wastewater overflow, the pump sump of any wastewater
system should be provided with an on-line standby pump of adequate capacity and
with automatic alternating devices.
7.18
Under
normal circumstances, surplus wastewater may be discharged into foul sewers
after treatment in silt removal and pH adjustment facilities (to within the pH
range of 6 to 10). Disposal of
wastewater into storm drains will require more elaborate treatment.
Wheel Washing Water
7.19
All
vehicles and plant should be cleaned before they leave a construction site to
minimize the deposition of earth, mud, debris on roads. A wheel washing bay should be provided at
every site exit if practicable and wash-water should have sand and silt settled
out or removed before discharging into storm drains. The section of construction road between the
wheel washing bay and the public road should be paved with backfall to reduce
vehicle tracking of soil and to prevent site run-off from entering public road
drains.
Bentonite Slurries
7.20
Bentonite
slurries used in construction works should be reconditioned and used again
wherever practicable. If the disposal of
a certain residual quantity cannot be avoided, the used slurry may be disposed
of at the marine spoil grounds subject to obtaining a marine dumping licence
from EPD on a case-by-case basis.
7.21
If
the used bentonite slurry is intended to be disposed of through the public drainage
system, it should be treated to the respective effluent standards applicable to
foul sewer, storm drains or the receiving waters as set out in the TM-DSS.
Water for Testing
& Sterilization of Water Retaining Structures and Water Pipes
7.22
Water
used in water testing to check leakage of structures and pipes should be used
for other purposes as far as practicable. Surplus unpolluted water could be
discharged into storm drains.
7.23
Sterilization
is commonly accomplished by chlorination.
Specific advice from EPD should be sought during the design stage of the
works with regard to the disposal of the sterilizing water. The sterilizing water should be used again
wherever practicable.
Wastewater from
Building Construction
7.24
Before
commencing any demolition works, all sewer and drainage connections should be
sealed to prevent building debris, soil, sand etc. from entering public
sewers/drains.
7.25
Wastewater
generated from building construction activities including concreting,
plastering, internal decoration, cleaning of works and similar activities
should not be discharged into the stormwater drainage system. If the wastewater is to be discharged into
foul sewers, it should undergo the removal of settleable solids in a silt removal
facility, and pH adjustment as necessary.
Acid Cleaning,
Etching and Pickling Wastewater
7.26
Acidic
wastewater generated from acid cleaning, etching, pickling and similar
activities should be neutralized to within the pH range of 6 to 10 before
discharging into foul sewers. If there
is no public foul sewer in the vicinity, the neutralized wastewater should be
tinkered off site for disposal into foul sewers or treated to a standard
acceptable to storm drains and the receiving waters.
Wastewater from
Site Facilities
7.27
Wastewater
collected from canteen kitchens, including that from basins, sinks and floor
drains, should be discharged into foul sewer via grease traps capable of
providing at least 20 minutes retention during peak flow.
7.28
Drainage
serving an open oil filling point should be connected to storm drains via a
petrol interceptors with peak storm bypass.
7.29
Vehicle
and plant servicing areas, vehicle wash bays and lubrication bays should as far
as possible be located within roofed areas.
The drainage in these covered areas should be connected to foul sewers
via a petrol interceptor. Waste oil
should be collected and stored for recycling or disposal in accordance with the
Waste Disposal Ordinance.
Effluent Discharge
7.30
There
is a need to apply to EPD for a discharge licence under the WPCO for discharging
effluent from the construction site. The discharge quality is required to meet
the requirements specified in the discharge licence. All the runoff, wastewater
or extracted groundwater generated from the works areas should be treated as
necessary so that it satisfies all the standards listed in the TM-DSS. It is anticipated that the wastewater
generated from the works areas would be of small quantity. Monitoring of the
construction site effluent quality should be carried out in accordance with the
WPCO license which is under the ambit of regional office (RO) of EPD.
Sewage from Workforce
7.31
Temporary
sanitary facilities, such as portable chemical toilets, should be employed
on-site where necessary to handle sewage from the workforce. A licensed contractor
would be responsible for appropriate disposal of waste matter and maintenance
of these facilities.
Accumulation of Solid Waste and Accidental
Spillage
7.32
Good
site practices should be adopted to remove rubbish and litter from construction
sites so as to prevent the rubbish and litter from spreading from the site
area. It is recommended to clean the
construction sites on a regular basis. Stockpiles of cement and other
construction materials should be kept covered when not being used.
7.33
Oils
and fuels should only be used and stored in designated areas which have
pollution prevention facilities. To
prevent spillage of fuels and solvents to the nearby watercourse, all fuel
tanks and storage areas should be provided with locks and be sited on sealed areas,
within bunds of a capacity equal to 110% of the storage capacity of the largest
tank. The bund should be drained of
rainwater after a rain event. Oil leakage or spillage should be contained and
cleaned up immediately.
Operation Phase
7.34
The
Project would not cause any adverse water quality impact during operation
phase. For handling and disposal of other operation
stage effluent (such as for the storm drainage), the practices outlined in
ProPECC PN 5/93 should be adopted where applicable. No other mitigation measure is required.