Table 6.4 EPD River Water Quality
Monitoring Data in 2012
|
Parameter |
Tin Sum Nullah |
River
WQO |
|
TR20B |
||
|
Dissolved Oxygen (mg/L) |
8.2 (7.8 – 9.6) |
No
less than 4 mg/L |
|
pH |
7.9 (7.7 – 8.4) |
6.5
– 8.5 |
|
Suspended Solids (mg/L) |
<1 (<1 – 6) |
Not
to cause more than 20 mg/L change |
|
5-day Biochemical Oxygen
Demand (mg/L) |
<1 (<1 – <1) |
Not
to cause more than 5 mg/L change |
|
Chemical Oxygen Demand
(mg/L) |
4 (<2 – 5) |
Not
to cause more than 30 mg/L change |
|
Oil & grease (mg/L) |
<0.5 (<0.5 – 0.5) |
Not
available |
|
Faecal coliforms (cfu/100mL) |
1 (<1 – <1) |
Not
available |
|
E.coli (cfu/100mL) |
1 (<1 – <1) |
1000 counts per 100ml |
|
Ammonia-nitrogen (mg/L) |
0.02 (<0.01 – 0.28) |
0.5
mg/L at any time |
|
Nitrate-nitrogen (mg/L) |
1.80 (0.67 – 2.50) |
Not
available |
|
Total Kjeldahl Nitrogen (mg/L) |
0.13 (0.05 – 0.51) |
Not
available |
|
Ortho-phosphate (mg/L) |
0.01 (<0.01 – 0.02) |
Not
available |
|
Total Phosphorus (mg/L) |
<0.02 (<0.02 – 0.03) |
Not
available |
|
Total Sulphide (mg/L) |
<0.02 (<0.02 – <0.02) |
Not
available |
|
Aluminium (µg/L) |
90 (<50 – 470) |
Not
available |
|
Cadmium (µg/L) |
<0.1 (<0.1 – 0.1) |
Not
available |
|
Chromium (µg/L) |
<1 (<1 – 1) |
Not
available |
|
Copper
(µg/L) |
2 (<1 – 8) |
Not
available |
|
Lead
(µg/L) |
<1 (<1 – 2) |
Not
available |
|
Zinc (µg/L) |
20 (<10 – 40) |
Not
available |
Notes:
1.
Data source: 2012 River Water Quality in Hong
Kong
2.
Except as specified, data presented are
depth-averaged values calculated by taking the means of three depths: surface,
mid-depth, bottom.
3.
Data presented are annual arithmetic means of
depth-averaged results except for E.coli
and faecal coliforms that are annual geometric means.
4.
Data in brackets indicate the ranges.
6.3.4
Full compliance with the river WQOs were
achieved at the monitoring station (TR20B) in Tin Sum Nullah for pH, suspended
solids (SS), dissolved oxygen (DO), COD and BOD5. The water quality
of this minor stream was reported to be excellent.
Water Sensitive Receivers
6.3.5
In order to evaluate potential water quality
impacts arising from the Project, water sensitive receivers (WSR) within 500 m
of the Project site boundary are considered. Two natural streams / nullah flow
along the Project site boundary. One is located to the northwest of the Project
boundary and the other one named Tin Sum Nullah is located along the southeast
of the Project boundary. The ecological value of these two watercourses is
generally low with low species diversity (refer to Section 8). No ecologically
important species susceptible to water pollution were recorded. However, any
pollutants generated by the Project activities could be discharged into these inland
water courses if uncontrolled, and hence may affect aquatic communities.
Locations of these WSRs are shown in Figure 6.1.
6.4
Assessment Methodologies
6.4.1
According to the EIA Study Brief, the
assessment area for water quality impact assessment will cover all areas within
a distance of 500 m from the boundary of the Project site. The water sensitive
receivers which may be affected by the Project have been identified. Potential
sources of water quality impact that may arise during the construction and
operational activities were described. Possible mitigation measures were also
identified to reduce adverse impacts on water quality.
6.5
Identification of Environmental Impacts
Construction
Phase
6.5.1
The proposed construction works for
reprovisioning of Sha Tin WTW would include demolition of the existing
facilities of the South Works and common facilities for both the North and the
South Works in phases as below; reprovisioning of the South Works; and construction of
new common facilities for both the North and the South Works. Details of the
construction works are described in Section 2. The construction sequence of the major
facilities is:
·
Construction
of retaining wall and new access road;
·
Construction
of new chemical house;
·
Demolition
of existing South Works;
·
Construction
of washwater equalization facilities;
·
Demolition
of existing chemical house (named as Water Treatment Works Logistics Centre);
·
Demolition
of existing washwater recovery tanks;
·
Construction
of Administration Building cum Mainland East Laboratory with visitor
facilities;
·
Construction
of the South Works (except Stage 2 filters);
·
Demolition
of existing administration building;
·
Construction
of Stage 2 filters; and
·
Paving
of access road.
6.5.2
No marine work including dredging would be
required for this Project. No construction activities would be conducted within
the natural streams / nullah within and adjacent to the Project Site. Also,
there would be no canteen or kitchen in the construction site. Potential
sources of water quality impact associated with the land-based construction of
the Project include:
·
General construction activities;
·
Construction site runoff;
·
Accidental spillage; and
·
Sewage effluent from construction workforce.
General Construction Activities
6.5.3
The land-based construction works could have
the potential to cause water pollution.
Various types of construction activities may generate wastewater. These include general cleaning and polishing,
wheel washing, and dust suppression.
These types of wastewater would contain high concentrations of suspended
solids (SS). There is no public sewer available for wastewater discharge
on-site. If uncontrolled, these effluents could lead to deterioration in water
quality.
Construction Site Runoff and Drainage
6.5.4
Construction site run-off would cause
potential water quality impacts.
Potential pollution sources of site run-off may include:
·
Runoff and erosion from exposed soil
surfaces, earth working areas and stockpiles;
·
Release of any bentonite slurries, concrete
washings and other grouting materials with construction run-off, storm water or
ground water dewatering process;
·
Wash water from dust suppression sprays and
wheel washing facilities; and
·
Fuel, oil and lubricants from maintenance of
construction vehicles and equipment.
6.5.5
During rainstorms, site run-off would wash
away the soil particles on unpaved lands and areas with the topsoil
exposed. The run-off is generally
characterized by high concentrations of SS.
Release of uncontrolled site run-off would increase the SS levels and
turbidity in the nearby water environment.
Site run-off may also wash away contaminated soil particles and
therefore cause water pollution.
6.5.6
Wind blown dust would be generated from
exposed soil surfaces in the works areas.
It is possible that wind blown dust would fall directly onto the nearby
water bodies when a strong wind occurs.
Dispersion of dust within the works areas may increase the SS levels in
surface run-off causing a potential impact to the nearby sensitive receivers.
Accidental Spillage
6.5.7
A large variety of chemicals may be used
during construction activities. These
chemicals may include petroleum products, surplus adhesives, spent lubrication
oil, grease and mineral oil, spent acid and alkaline solutions/solvent and
other chemicals. Accidental spillage of
chemicals in the works areas may contaminate the surface soils. The contaminated soil particles may be washed
away by construction site run-off or stormwater drainage which in turn causes
water pollution.
Sewage Effluent from Construction Workforce
6.5.8
During the construction of the Project, the
workforce on site will contribute to the local population of the area, although
the number of workers will vary over the construction period. Potential impacts
may arise from wastewater generated from sanitary facilities and waste disposal
areas.
6.5.9
Deep excavation would be required for
construction of water tanks and the associated facilities. Since potentially
contaminated areas at the Project site were identified in the Contamination
Assessment Plan (CAP), any groundwater pumping out or from dewatering process
during excavation works could be potentially contaminated. Discharge / recharge of potentially
contaminated groundwater generated may affect the surface / groundwater
quality, if uncontrolled.
Operational
Phase
6.5.10
The Sha Tin WTW is to treat raw water mainly imported
from Dongjiang and to provide water supply to territory. The treated water
would comply with the latest standards as specified by WSD. The existing treated water quality standards
as specified by WSD, the authority in
Hong Kong, is based on the World Health Organization (WHO)’s Guidelines for
Drinking-water Quality 2008, supplemented by an additional 10 parameters not
included in the Guidelines. Upon decommissioning for the South Works, it would
then move to the construction phase. Similarly upon completion of the
construction, it would move to the operation phase. No water quality
impact would be expected from switching the existing facilities to the upgraded
facilities. Potential sources of water quality impacts on the nearby water
courses due to the Sha Tin WTW operation would be:
·
Washwater effluent; and
·
Overflow from Treatment Works Components.
Washwater Effluent
6.5.11
During operational phase of the Project, cleansing
of the treatment works components such as filter beds would be required. Washwater
may contain various chemicals, such as polymer, ammonium sulphate, sodium
phosphate, and chlorine, and any impurities removed by the filters. Direct
discharge of such washwater could deteriorate water quality in the receiving
water bodies, if uncontrolled.
Overflow from Treatment Works Components
6.5.12
Possible failure of treatment works
components or interruption of the electrical power supply could cause Sha Tin
WTW operational failures, which could result in an overflow of water. If uncontrolled,
overflow of water would be discharged to the surrounding area and adjacent
water courses.
6.6
Cumulative Impacts from Concurrent Project
6.6.1
The construction works for Shatin to Central
Link – Tai Wai to Hung Hom Section would be conducted concurrently with this
Project. The construction for the railway alignment near the Sha Tin WTW will
be land-based only. Provided that all mitigation measures as recommended in the
EIA Report will be implemented properly, the potential water quality impact
from the Project is expected to be localized and therefore no cumulative water
quality impacts would be expected.
6.7
Prediction and Evaluation of Environmental Impacts
Construction
Phase
General Construction Activities
6.7.1
Land-based construction activities would
generate wastewater and cause water pollution. Their impacts are likely to be
minimal, provided that good construction practices and proper site management
would be observed. Effluent discharge from temporary site facilities should be
controlled to prevent direct discharge to the neighbouring water environment.
It is anticipated that water quality impacts caused by general construction
activities would be insignificant with adequate implementation of recommended
mitigation measures (as given in Section
6.8).
Construction Site Run-off and Drainage
6.7.2
Construction site run-off and drainage may
cause local water quality impacts.
Increase in SS arising from the construction site could block the
drainage channels and may result in local flooding when heavy rainfall
occurs. As a good site practice,
mitigation measures should be implemented to control construction site runoff
and drainage from the works areas, and to prevent runoff and drainage water
with high levels of SS from entering the nearby water bodies. With the implementation of appropriate
measures to control run-off and drainage from the construction site,
disturbance of water bodies would be avoided and deterioration in water quality
would be minimal. Unacceptable impacts on the water quality are not expected,
provided that the recommended measures described in Section 6.8 are properly implemented.
Accidental Spillage
6.7.3
The use of engine oil and lubricants, and
their storage as waste materials has the potential to create impacts on the
water quality if spillage occurs and enters adjacent water environment. Waste oil may infiltrate into the surface
soil layer, or run-off into nearby water environment, increasing hydrocarbon
levels. The potential impacts could
however be mitigated by practical mitigation measures and good site practices
(as given in Section 6.8).
Sewage Effluent from Construction Workforce
6.7.4
Domestic sewage would be generated from the
workforce during the construction phase. Provided that sewage is not discharged
directly into stormwater drains or natural streams / nullah adjacent to the
construction site and this temporary sewage will be properly treated by interim
sewage treatment facilities, such as portable chemical toilets which are
properly maintained with the employment of licensed collectors for the
collection and disposal on a regular basis, it is unlikely that sewage
generated from the site would have a significant water quality impact. Mitigation measures and good site practices
given in Section 6.8 should be
implemented.
Groundwater
6.7.5
Deep excavation would be required for
construction of water tanks and the associated facilities. Since potentially
contaminated areas at the Project site were identified in the CAP, any groundwater
pumping out or from dewatering process during excavation works could be
potentially contaminated. Prior to the
excavation works, the baseline groundwater quality in these potentially
contaminated areas should be reviewed with reference to the relevant site
investigation data and any additional groundwater quality measurement
results. The review results should be
submitted to EPD for examination. If the results indicate contamination for the
groundwater to be generated from the excavation works, this contaminated
groundwater would either be properly treated or properly recharged into the
ground in compliance with the requirements of the TM-DSS. No direct discharge of contaminated
groundwater would be allowed. Provided that all the mitigation measures and
monitoring requirements as recommended in Sections
6.8 and 6.10 are followed properly, no adverse water quality impact would
be envisaged.
Operational
Phase
Washwater Effluent
6.7.6
During operational phase, cleansing of the
treatment works components would be required. The washwater would firstly be
captured by the washwater
equalization tanks, the washwater would then be treated using dissolved air
flotation (DAF) clarification at the DAF clarifiers or other high rate
sedimentation process and finally flow to the Inlet Works to be blended with
raw water. The treatment of sludge generated from the DAF clarification or
other high rate sedimentation process is detailed in the waste management
section. A flow chart for the
treatment of spent washwater is given below in Plate 1. No washwater would be discharged off-site and thus no
adverse impacts upon the nearby watercourses arising from the washwater effluent
would be anticipated.
Plate 1 Flow Chart for Spent
Washwater
Overflow from Treatment Works Components
6.7.7 Overflow
of raw water and process water may occur in the event of equipment failure or
interruption of the electrical power supply. Potential overflow would come from
raw water (which comes from local reservoir and Guangdong) and well process /
treated water (which contains low level of chemicals that used to removed
pollutants and enhance the drinking water quality). The discharge of overflow
in case of equipment failure or power failure is not expected to result in
significant impact on water quality of receiving waters. Provision of standby
units and dual power supply could minimise occurrence of overflow. Discharge of
overflow into the surrounding area and nearby water courses would be avoided
and hence no adverse water quality impact would be anticipated.
6.8
Mitigation of Adverse Environmental Impacts
Construction
Phase
Construction Site Run-off and General Construction
Activities
6.8.1
The site practices outlined in ProPECC PN
1/94 “Construction Site Drainage” should be followed to minimise surface
run-off and the chance of erosion.
Effluent discharged from the construction site should comply with the
standards stipulated in the TM-DSS. The following measures are recommended to
protect water quality and sensitive uses of the inland and coastal waters, and
when properly implemented should be sufficient to adequately control site
discharges so as to avoid water quality impacts:
6.8.2
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.
6.8.3
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 to prevent local
flooding. 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. Minimum distances of 100 m should be maintained between the
discharge points of construction site run-off and the existing saltwater
intakes. While the locations of the discharge points of construction site
run-off have not been confirmed at the current stage, the discharge points are
confirmed to be located within the construction site boundary. The nearest
seawater intake from the construction site within the same watershed would be
the Sha Tin WSD flushing water intakes, which is located at Sha Tin Hoi (5 km
away). It is anticipated that the minimum separation between the discharge
points of construction site effluent and the existing seawater intakes would be
satisfied.
6.8.4
Construction works should be programmed to
minimize soil excavation works in rainy seasons (April to September) as far as
practicable. If excavation in soil
cannot 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 run-off 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.
6.8.5
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.
6.8.6
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.
6.8.7
Open stockpiles of construction materials
(e.g. aggregates, sand and fill material) on sites should be covered with
tarpaulin or similar fabric during rainstorms.
6.8.8
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.
6.8.9
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.
Wheel
Washing Water
6.8.10
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.
Wastewater
from Building Construction
6.8.11
Before commencing any demolition works, all
drainage connections should be sealed to prevent building debris, soil, sand
etc. from entering drains.
6.8.12
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 tankered off site for disposal 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
6.8.13
Acidic wastewater generated from acid
cleaning, etching, pickling and similar activities should be neutralized to
within the pH range of 6 to 10. The neutralized wastewater should be tankered
off site for disposal into foul sewers or treated to a standard acceptable to
storm drains and the receiving waters.
Effluent
Discharge
6.8.14
There is a need to apply to EPD for a
discharge licence for discharge of effluent from the construction site under
the WPCO. The discharge quality must meet the requirements specified in the discharge
licence. All the run-off and wastewater generated from the works areas should
be treated so that it satisfies all the standards listed in the TM-DSS. Minimum
distances of 100 m should be maintained between the discharge points of
construction site effluent and the existing seawater intakes. The nearest
seawater intake from the construction site within the same watershed would be
the WSD flushing water intakes, which is located at Sha Tin Hoi (5 km away). It
is anticipated that the minimum separation between the discharge points of
construction site effluent and the existing seawater intakes would be
satisfied. The beneficial uses of the treated effluent for other on-site
activities such as dust suppression, wheel washing and general cleaning etc., can
minimise water consumption and reduce the effluent discharge volume. 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 relevant WPCO licence which is under the ambit of
regional office of EPD.
Accidental Spillage
6.8.15
Contractor must register as a chemical waste
producer if chemical wastes would be produced from the construction activities.
The Waste Disposal Ordinance (Cap 354) and its subsidiary regulations in
particular the Waste Disposal (Chemical Waste) (General) Regulation should be
observed and complied with for control of chemical wastes.
6.8.16
Any service shop and maintenance facilities
should be located on hard standings within a bunded area, and sumps and oil
interceptors should be provided. Maintenance of vehicles and equipment
involving activities with potential for leakage and spillage should only be
undertaken within the areas appropriately equipped to control these discharges.
6.8.17
Disposal of chemical wastes should be carried
out in complian ce with the Waste Disposal Ordinance. The
Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes
published under the Waste Disposal Ordinance details the requirements to deal
with chemical wastes. General requirements are given as follows:
·
Suitable containers should be used to hold
the chemical wastes to avoid leakage or spillage during storage, handling and
transport.
·
Chemical waste containers should be suitably
labelled, to notify and warn the personnel who are handling the wastes, to
avoid accidents.
·
Storage area should be selected at a safe
location on site and adequate space should be allocated to the storage area.
Sewage Effluent from Construction Workforce
6.8.18
The construction workforce on site will
generate sewage. It is recommended that
all the sewage generated from the workforce should be properly treated by
interim treatment facilities, such as chemical toilets which are properly
maintained with the employment of licensed collectors for the collection and
disposal on a regular basis. Interim treatment facilities should be
properly maintained to avoid adverse impact upon the nearby water environment.
6.8.19
Notices should be posted at conspicuous
locations to remind the workers not to discharge any sewage or wastewater into
the surrounding environment. Regular
environmental audit of the construction site will provide an effective control
of any malpractices and can encourage continual improvement of environmental
performance on site. It is anticipated
that sewage generation during the construction phase of the project would not
cause water pollution problem after undertaking all required measures.
Construction Works in Close Proximity of Inland
Water
6.8.20
Construction works would be carried out in
close proximity of inland water courses along Project site. To minimize the
potential water quality impacts from the construction works near any water
courses, the practices outlined in ETWB TC (Works) No. 5/2005 “Protection of Natural
Streams/rivers from Adverse Impacts arising from Construction Works” should be
adopted where applicable. Relevant mitigation measures are listed
below:
·
Temporary storage of materials (e.g.
equipment, filling materials, chemicals and fuel) and temporary stockpile of
construction materials should be located well away from any water courses
during carrying out of the construction works.
·
Stockpiling of construction materials and
dusty materials should be covered and located away from any water courses.
·
Shoring should be properly erected as
appropriate to prevent soil/ mud from slipping into the watercourses. Stockpiles should be properly covered.
·
Construction debris and spoil should be
covered up and/or disposed of as soon as possible to avoid being washed into
the nearby water receivers.
·
Construction activities, which generate large
amount of wastewater, should be carried out in a distance away from the
waterfront, where practicable.
·
Hoarding should be erected along the site
boundary to protect the nearby watercourses.
Groundwater
6.8.21
No direct discharge of groundwater from
contaminated areas should be adopted.
Prior to any excavation works within the potentially contaminated areas,
the baseline groundwater quality should be reviewed based on the relevant site
investigation data and groundwater quality measurements with reference to
Guidance Note for Contaminated Land Assessment and Remediation and the review
results should be submitted to EPD for examination. If the review results
indicate contamination for the groundwater to be generated from the excavation
works, this contaminated groundwater should either be properly treated or
properly recharged into the ground in compliance with the requirements of the
TM-DSS. If wastewater treatment is to
be deployed for treating the contaminated groundwater, the wastewater treatment
unit shall deploy suitable treatment processes (e.g. oil interceptor /
activated carbon) to reduce the pollution level to an acceptable standard and
remove any prohibited substances to an undetectable range. All treated effluent
from the wastewater treatment plant shall meet the requirements as stated in
TM-DSS and should be tankered away for proper disposal.
6.8.22
If deployment of wastewater treatment is not
feasible for handling the contaminated groundwater, groundwater recharging
wells should be installed as appropriate for recharging the contaminated
groundwater back into the ground. The recharging wells should be selected at
places where the groundwater quality would not be affected by the recharge
operation as indicated in Section 2.3 of the TM-DSS. The baseline groundwater quality
should be determined prior to the selection of the recharge wells, and a
working plan should be submitted to EPD for agreement. Pollution levels of groundwater to be
recharged shall not be higher than pollutant levels of ambient groundwater at
the recharge well. Groundwater monitoring wells should be installed near the
recharge points to monitor the effectiveness of the recharge wells and to
ensure that no likelihood of increase of groundwater level and transfer of
pollutants beyond the site boundary. Prior to recharge, free products should be
removed as necessary by installing the petrol interceptor. The Contractor should apply for a discharge
licence under the WPCO through the Regional Office of EPD for groundwater
recharge operation or discharge of treated groundwater.
Operation
Phase
Emergency Overflow
6.8.23
Standby treatment facilities, such as
parallel trains in flash mixing basins, backwash pumps and pumps in the
inter-stage booster pumping station, would be provided to prevent the
occurrence of overflow as a result of equipment failure or maintenance.
6.8.24
Dual power supply should be provided. Dual
power supply could be in the format of ring main, or an automatic-operated
emergency generator with sufficient capacity to cope with the demand loading of
the essential plant equipment. Inlet valve feeding raw water would be closed
manually within 30 minutes by the operator-in-charge in case of equipment or
power failure.
Summary
of Mitigation Measures
6.8.25
The recommended mitigation measures are
summarized as below:
Construction Phase
·
The site practices outlined in ProPECC PN
1/94 “Construction Site Drainage” should be followed to minimise surface
run-off and the chance of erosion.
Effluent discharged from the construction site should comply with the
standards stipulated in the TM-DSS.
·
The Waste Disposal Ordinance (Cap 354) and
its subsidiary regulations in particular the Waste Disposal (Chemical Waste)
(General) Regulation should be observed and complied with for control of
chemical wastes.
·
All the sewage generated from the workforce
should be properly treated by interim treatment facilities, such as chemical
toilets.
·
The practices outlined in ETWB TC (Works) No.
5/2005 “Protection of Natural Streams/rivers from Adverse Impacts arising from
Construction Works” should be adopted where applicable, to minimize the
potential water quality impacts from the construction works near any water
courses,
·
Contaminated groundwater, if any, should
either be properly treated or properly recharged into the ground in compliance
with the requirements of the TM-DSS.
Operation Phase
·
Standby treatment facilities and dual power
supply should be provided to prevent the occurrence of overflow.
·
Inlet valve feeding raw water would be closed
manually within 30 minutes by the operator-in-charge in case of equipment or
power failure.
6.9
Evaluation of Residual Environmental Impacts
6.9.1
With the full implementation of the
recommended mitigation measures for the construction and operation phases of
the proposed Project, no adverse impact on water quality is anticipated.
6.10
EM&A Requirements
Construction Phase
6.10.1
Minimisation of water quality deterioration
from land-based construction activities could be achieved through implementing
adequate mitigation measures. To ensure
no adverse water quality impact to the nearby water courses due to the
discharge of surface runoff and drainage from the works areas, water quality
monitoring of the two water courses along the Project boundary is recommended
during site clearance and foundation works. Details of the recommended water quality
monitoring requirements are provided in the stand-alone EM&A Manual for the
Project. It is also recommended that regular site inspections should be undertaken
to inspect the construction activities and works areas in order to ensure the
recommended mitigation measures are properly implemented.
Operational
Phase