5 WATER QUALITY
5.1 Introduction
5.2 Water
Sensitive Receivers
5.3 Environmental
Legislation, Policies, Plans, Standards and Criteria
5.4 Description
of the Environment
5.5 Identification
of Environmental Impact
5.6 Assessment
Methodology
5.7 Prediction
and Evaluation of Environmental Impacts
5.8 Mitigation
of Adverse Environmental Impacts
5.9 Evaluation
of Residual Impacts
5.10 Environmental
Monitoring and Audit
5.11 Conclusion
5.1.1
This section presents the
assessment results of the potential water quality impact associated with the
construction and operation of the proposed Road P2 and other roads which are classified
as primary/district distributor roads (DP2). Mitigation measures are also recommended
to minimise potential adverse impacts and to ensure the acceptability of any
residual impact (that is, after mitigation).
5.2.1
Water sensitive receivers
(WSRs) that would potentially affected by the construction and operation of the
Project include several seawater intakes identified at or near the Project site
along the existing waterfront of Wan Chai. These seawater intakes supply
cooling water to the air conditioning systems of various commercial buildings
in the Wan Chai area including:
·
Hong Kong Convention and Exhibition Centre (HKCEC) Phase 1
·
Shui
On Centre
·
Telecom
House
·
Government
Buildings (Wan Chai Tower/Revenue Tower/Immigration Tower)
·
China Resources
Building
·
Hong Kong Exhibition Centre
·
Great
Eagle Centre
·
Sun Hung
Kai Centre.
5.2.2
Cooling water intake for Sun
Hung Kai Centre will be reprovisioned to the new waterfront of Wan Chai during
operational phase. The rest of the above listed cooling water intakes will be
reprovisioned to the intake chambers to the north of HKCEC Extension.
5.2.3
An existing WSD flushing water
intake is also located within the proposed reclamation limit at Wan Chai which
will be uprated and reprovisioned to Wan
Shing Street during operational phase.
5.2.4
Figure 5.2 shows the locations of the existing and reprovisioned seawater
intakes at or near the Project site.
5.3
Environmental Legislation, Policies, Plans,
Standards and Criteria
5.3.1
The criteria for evaluating
water quality impacts in this EIA Study include:
Environmental Impact Assessment Ordinance (EIAO)
5.3.2
The Technical Memorandum on
Environmental Impact Assessment Process (Environmental Impact Assessment
Ordinance) (EIAO-TM) was issued by EPD under Section 16 of the EIAO. It specifies the assessment method and
criteria that were followed in this Study.
Reference sections in the EIAO-TM provide the details of assessment
criteria and guidelines that are relevant to the water quality assessment,
including:
·
Annex 6 – Criteria for Evaluating Water Pollution
·
Annex 14 – Guidelines for Assessment of Water
Pollution.
Water Quality Objectives
5.3.3
The Water Pollution Control
Ordinance (WPCO) provides the major statutory framework for the protection and
control of water quality in Hong Kong. According to the Ordinance and its
subsidiary legislation, Hong Kong waters are
divided into ten Water Control Zones (WCZs). Corresponding statements of Water
Quality Objectives (WQO) are stipulated for different water regimes (marine
waters, inland waters, bathing beaches subzones, secondary contact recreation
subzones and fish culture subzones) in the WCZ based on their beneficial
uses. The proposed Project is
located within Victoria
Harbour (Phase Three) WCZ
and the corresponding WQO are listed in Table 5.1.
Table 5.1 Summary
of Water Quality Objectives for Victoria
Harbour WCZ
|
Parameters
|
Objectives
|
Sub-Zone
|
|
Offensive odour, tints
|
Not to be present
|
Whole zone
|
|
Visible foam, oil scum,
litter
|
Not to be present
|
Whole zone
|
|
Dissolved oxygen (DO) within
2 m of the seabed
|
Not less than 2.0 mg/l for
90% of samples
|
Marine waters
|
|
Depth-averaged DO
|
Not less than 4.0 mg/l for
90% of samples
|
Marine waters
|
|
pH
|
To be in the range of 6.5
- 8.5, change due to human activity not to exceed 0.2
|
Marine waters
|
|
Salinity
|
Change due to human
activity not to exceed 10% of ambient
|
Whole zone
|
|
Temperature
|
Change due to human
activity not to exceed 2 oC
|
Whole zone
|
|
Suspended solids (SS)
|
Not to raise the ambient level
by 30% caused by human activity
|
Marine waters
|
|
Unionised ammonia (UIA)
|
Annual mean not to exceed
0.021 mg/l as unionised form
|
Whole zone
|
|
Nutrients
|
Shall not cause excessive
algal growth
|
Marine waters
|
|
Total inorganic nitrogen
(TIN)
|
Annual mean depth-averaged
inorganic nitrogen not to exceed 0.4 mg/l
|
Marine waters
|
|
Toxic substances
|
Should not attain such
levels as to produce significant toxic, carcinogenic, mutagenic or
teratogenic effects in humans, fish or any other aquatic organisms.
|
Whole zone
|
|
Human activity should not
cause a risk to any beneficial use of the aquatic environment.
|
Whole zone
|
Source: Statement
of Water Quality Objectives (Victoria
Harbour (Phases One, Two
and Three) Water Control Zone).
Water Supplies Department (WSD) Water Quality
Criteria
5.3.4
Besides the WQO set under the
WPCO, the WSD has specified a set of objectives for water quality at flushing
water intakes. The list is shown in
Table 5.2. The target limit for suspended solids
(SS) at these intakes is 10 mg/l or less.
Table 5.2 WSD’s
Water Quality Criteria for Flushing Water at Sea Water Intakes
|
Parameter (in
mg/l unless otherwise stated)
|
Target Limit
|
|
Colour (HU)
|
< 20
|
|
Turbidity (NTU)
|
< 10
|
|
Threshold Odour
Number (odour unit)
|
< 100
|
|
Ammoniacal
Nitrogen
|
< 1
|
|
Suspended
Solids
|
< 10
|
|
Dissolved
Oxygen
|
> 2
|
|
Biochemical
Oxygen Demand
|
< 10
|
|
Synthetic
Detergents
|
< 5
|
|
E. coli (no. per 100
mL)
|
< 20,000
|
Cooling Water Intake Standards
5.3.5
Based on a questionnaire survey
conducted under the approved Comprehensive Feasibility Study for Wan Chai
Development Phase II (WDIICFS) EIA (),
no information on the SS limit is available for all the identified cooling
water intakes. These findings have been confirmed by a telephone survey
conducted under the recent approved EIA for the Hong Kong Convention and
Exhibition Centre (HKCEC) Atrium Link Extension (ALE). The locations of the cooling water
intakes are shown in Figure 5.2. The SS criterion for
cooling water intakes is different from that for the WSD’s intakes as their
beneficial uses are different (the former is used for cooling water system and
the latter for flushing purpose).
Technical Memorandum
5.3.6
Discharges of effluents are
subject to control under the WPCO. The Technical Memorandum on Standards for
Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal
Waters (TM-DSS) gives guidance on the permissible effluent discharges based on
the type of receiving waters (foul sewers, storm water drains, inland and
coastal waters). The limits control
the physical, chemical and microbial quality of effluents. Any sewage from the
proposed construction and operation activities must comply with the standards
for effluents discharged into the foul sewers, inshore waters or marine waters
of Victoria Harbour WCZ, as given in the TM-DSS.
Practice Note
5.3.7
A Practice Note for
Professional Persons (ProPECC) was issued by the EPD to provide guidelines for
handling and disposal of construction site discharges. The ProPECC PN 1/94 “Construction Site
Drainage” provides good practice guidelines for dealing with ten types of
discharge from a construction site.
These include surface runoff, groundwater, boring and drilling water,
bentonite slurry, water for testing and sterilisation of water retaining
structures and water pipes, wastewater from building constructions, acid
cleaning, etching and pickling wastewater, and wastewater from site facilities. Practices given in the ProPECC PN 1/94
should be followed as far as possible during construction to minimise the water
quality impact due to construction site drainage.
Marine Water Quality in Victoria Harbour
5.4.1
The marine water quality
monitoring data routinely collected by EPD in Victoria Harbour
were used to establish the baseline condition. A summary of water quality data
for selected EPD monitoring stations extracted from the EPD’s publication “20
years of Marine Water Quality Monitoring in Hong Kong”
(which is the latest version available at the time of preparing this report) is
presented in Table 5.3. The
monitoring stations in Victoria
Harbour central (VM4, VM5
and VM6) are considered
to be representative of the water quality in the marine waters of the
assessment area.
Locations of the monitoring stations are shown in Figure 5.1.
5.4.2
In the past, wastewater from
both sides of the Victoria Harbour was discharged into it after just simple
screening, leading to marine water low in DO and high in organic nutrients and
sewage bacteria. Commissioning
of HATS Stage 1 in
late 2001 has brought large and sustained improvements to the water quality of
the eastern and central Victoria
Harbour. However,
improvements are less noticeable in the western harbour area which was still
subject to the sewage discharges from local PTW (Central, Wan Chai West and Wan
Chai East). As the HATS Stage 1 was commissioned in late 2001, the data for
2005 as shown in Table 5.3 represent
the situation after the commissioning of HATS Stage 1.
5.4.3
In 2005, the moderate improvements in the
mid harbour area since HATS Stage 1 was commissioned were generally
sustained. Full
compliance with the WQO (for DO, TIN and UIA) was achieved in 2005 in the central
Victoria Harbour WCZ.
Table 5.3 Summary
Statistics of 2005 Marine Water Quality in Victoria Harbour
|
Parameter
|
Victoria Harbour Central
|
WPCO WQO (in marine waters)
|
|
VM4
|
VM5
|
VM6
|
|
Temperature (oC)
|
22.9
(15.8-27.8)
|
23
(15.9-27.9)
|
23
(15.9-27.8)
|
Not more than 2 oC in daily temperature range
|
|
Salinity
|
31.8(28.9-33.2)
|
31.4
(27.3-32.9)
|
31.3
(26.8-32.8)
|
Not to cause
more than 10% change
|
|
Dissolved Oxygen
(DO) (% Saturation)
|
Depth average
|
75
(63-88)
|
76
(68-99)
|
77
(68-96)
|
Not available
|
|
Bottom
|
74
(51-88)
|
74
(46-99)
|
73
(45-94)
|
Not available
|
|
Dissolved Oxygen
(DO)
(mg/l)
|
Depth average
|
5.4
(4.4-6.6)
|
5.5
(4.7-6.6)
|
5.5
(4.8-6.5)
|
Not less than 4 mg/l for 90% of
the samples
|
|
Bottom
|
5.3
(3.6-6.5)
|
5.3
(3.3-6.6)
|
5.3
(3.2-6.5)
|
Not less than 2 mg/l for 90% of
the samples
|
|
pH
|
8
(7.7-8.3)
|
8
(7.6-8.3)
|
8
(7.6-8.2)
|
6.5 - 8.5 (± 0.2
from natural range)
|
|
Secchi disc Depth (m)
|
2.1
(1.5-3.2)
|
2.1
(1.3-3.1)
|
2.1
(1.2-3.3)
|
Not available
|
|
Turbidity (NTU)
|
9.6
(4.5-15.3)
|
9.8
(4.9-14.5)
|
9.8
(5.0-14.8)
|
Not available
|
|
Suspended Solids (SS) (mg/l)
|
3.6
(1.3-9.8)
|
3.4
(1.7-5.3)
|
3.7
(1.3-8.2)
|
Not more than 30% increase
|
|
5-day Biochemical Oxygen Demand (BOD5) (mg/l)
|
0.9
(0.5-1.1)
|
1.1
(0.6-1.4)
|
0.9
(0.4-1.4)
|
Not available
|
|
Nitrite Nitrogen (NO2-N) (mg/l)
|
0.03
(0.01-0.05)
|
0.03
(0.01-0.05)
|
0.03
(0.01-0.05)
|
Not available
|
|
Nitrate Nitrogen (NO3-N) (mg/l)
|
0.13
(0.05-0.24)
|
0.15
(0.05-0.31)
|
0.16
(0.06-0.34)
|
Not available
|
|
Ammonia Nitrogen (NH3-N) (mg/l)
|
0.15
(0.06-0.27)
|
0.19
(0.06-0.29)
|
0.19
(0.07-0.26)
|
Not available
|
|
Unionised Ammonia (UIA) (mg/l)
|
0.006
(0.003-0.015)
|
0.007
(0.005-0.015)
|
0.008
(0.004-0.014)
|
Not more than 0.021 mg/l for annual mean
|
|
Total Inorganic Nitrogen (TIN) (mg/l)
|
0.31
(0.12-0.54)
|
0.37
(0.12-0.64)
|
0.38
(0.14-0.65)
|
Not more than 0.4 mg/l for annual mean
|
|
Total Nitrogen (TN) (mg/l)
|
0.47
(0.26-0.69)
|
0.55
(0.28-0.77)
|
0.55
(0.29-0.79)
|
Not available
|
|
Orthophosphate Phosphorus (PO4) (mg/l)
|
0.03
(0.01-0.04)
|
0.04
(0.01-0.05)
|
0.03
(0.01-0.05)
|
Not available
|
|
Total Phosphorus (TP) (mg/l)
|
0.05
(0.03-0.06)
|
0.05
(0.03-0.07)
|
0.05
(0.03-0.07)
|
Not available
|
|
Chlorophyll-a
(µg/L)
|
2.4
(0.9-7.2)
|
2.8
(0.8-9.1)
|
2.6
(0.8-9.0)
|
Not available
|
|
E coli
(cfu/100 ml)
|
2400
(310-11000)
|
7700
(2500-23000)
|
5700
(1200-33000)
|
Not available
|
|
Faecal Coliforms
(cfu/100 ml)
|
5200
(770-33000)
|
17000
(6800-40000)
|
12000
(2300-89000)
|
Not available
|
Notes: 1. Except as specified, data presented are depth-averaged
values calculated by taking the means of three depths: Surface, mid-depth,
bottom.
2. Data
presented are annual arithmetic means of depth-averaged results except for E. coli and faecal coliforms that are
annual geometric means.
3. Data in
brackets indicate the ranges.
5.5
Identification of Environmental Impact
Operational
Phase
5.5.1
Potential water quality impact
would be associated with surface road runoff which may be contaminated by oils
leaked from passing vehicles. It is
considered that impacts upon water quality will be minimal provided that the
road works are designed with adequate drainage systems and appropriate oil
interceptors, as required.
Construction Phase
5.5.2
Potential sources of water quality
impacts arising from the construction phase will be similar to those of general
land-based construction activities.
Stormwater Discharges
5.5.3
Stormwater and drainage discharges
from the construction sites may contain considerable loads of SS and
contaminants during construction activities. Potential water quality impact includes
run-off and erosion of exposed bare soil and earth, drainage channels, earth
working area and stockpiles. Minimum distances of 100 m shall be maintained
between the existing or planned stormwater discharges and the existing or
planned WSD flushing water intakes during construction and operation phases.
5.5.4
Local and coastal water pollution
impact may be substantial if the construction site run-off is allowed to
discharge into the storm drains or natural drainage without mitigation.
Construction Runoff and
Drainage
5.5.5
Surface runoff generated from the
construction site may contain increased loads of SS and contaminants. Potential pollution sources of site
run-off may come from:
·
contaminated ground water from any dewatering
activities as a result of excavation
·
release of any bentonite slurries 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
·
fuel, oil and lubricants from maintenance of
construction vehicles and equipment.
General Construction Activities
5.5.6
The general construction works that
will be undertaken for the roads will be primarily land-based and may have the
potential to cause water pollution.
These could result from the accumulation of solid waste such as
packaging and construction materials, and liquid waste such as sewage effluent
from the construction work force, discharge of bilge water and spillage of oil,
diesel or solvents by vessels and vehicles involved with the construction. If uncontrolled, any of these could lead
to deterioration in water quality.
Increased nutrient levels result from contaminated discharges and sewage
effluent could also lead to a number of secondary water quality impacts
including decreases in DO concentrations and localised increase in NH3-N
concentrations which could stimulate algal growth and reduction in oxygen
levels.
5.5.7
Sewage will arise from sanitary
facilities provided for the on-site construction work force. It is characterised by high level of
BOD, NH3-N and E.coli counts. For
some of the works areas, there will be no public sewers available for domestic
sewage discharge on-site.
5.6.1
The assessment of the
potential impact of land-based construction activities on water quality has been undertaken in a
qualitative manner. Proposed construction activities were reviewed to assess the land-based water quality impact upon
the nearby water bodies. Practical
water pollution control measures / mitigation proposals (Section 5.8) have been
subsequently recommended to prevent local flooding and to ensure that effluent
discharged from the construction site will comply with the WPCO criteria.
Operational Phase
5.7.1
Potential water quality impact
would be associated with surface road runoff which may be contaminated by oils
leaked from passing vehicles. It is
considered that impacts upon water quality will be minimal provided that the
road works are designed with adequate drainage systems and appropriate oil
interceptors, as required.
Construction Phase
General Construction
Activities
5.7.2
The effects on water quality
from general construction activities are likely to be minimal, provided that
site drainage is well maintained and good construction practices are observed
to ensure that litter, fuels, and solvents are managed, stored and handled
properly.
5.7.3
Based on the Sewerage Manual,
Part I, 1995 of the Drainage Services Department (DSD), the global unit flow
factors for employed population of 0.06 m3 per worker per day
and commercial activities in year 2016 of 0.29 m3 per worker per day
have been used to estimate the sewage generation from the construction
site. The total sewage production
rate is estimated at 0.35 m3 per worker per day. Therefore, with 50 construction workers
working simultaneously at the construction site, a total of about 17.5 m3
of sewage will be generated per day.
The sewage should not be allowed to discharge directly into the surrounding
water body without treatment.
Chemical toilets and subsequently on-site sewer should be deployed at
the construction site to collect and handle sewage from workers (see Section
5.8 for recommended mitigation measures).
Construction Runoff and Drainage
5.7.1
Construction run-off and
drainage may cause physical, chemical and biological effects. The physical effects could arise from
any increase in SS from the construction site that could cause blockage of
drainage channels and associated local flooding when heavy rainfall occurs, as
well as local impact on water quality.
High SS concentrations in marine water could lead to associated
reduction in DO levels.
5.7.2
It is important that proper
site practice and good site management be strictly followed to prevent run-off
water and drainage water with high level of SS from entering the surrounding
waters. With the implementation of
appropriate measures to control run-off and drainage from the construction
site, it is considered that disturbance of water bodies will be localised and
deterioration in water quality will be minimal. Thus, unacceptable impacts on the water
quality are not expected provided that the recommended measures described in
Section 5.8 are properly implemented.
Operational Phase
5.8.1
For the operation of road
works, a surface water drainage system would be provided to collect road
runoff. It is recommended that the
road drainage should be provided with adequately designed silt trap and oil interceptors,
as necessary. The design of the operational stage mitigation measures for the
road works shall take into account the guidelines published in ProPECC PN 5/93
“Drainage Plans subject to Comment by the EPD”.
Construction
Phase
5.8.2
It is important that
appropriate measures are implemented to control runoff and drainage and prevent
high loading of SS from entering the marine environment. Proper site management is essential to
minimise surface water runoff, soil erosion and sewage effluents.
5.8.3
Any practical options for the
diversion and re-alignment of drainage should comply with both engineering and
environmental requirements in order to ensure adequate hydraulic capacity of
all drains.
5.8.4
Construction site runoff and
drainage should be prevented or minimised in accordance with the guidelines
stipulated in the EPD's Practice Note for Professional Persons, Construction
Site Drainage (ProPECC PN 1/94).
Good housekeeping and stormwater best management practices, as detailed
in below, should be implemented to ensure that all construction runoff complies
with WPCO standards and that no unacceptable impact on the WSRs arises due to
construction of the road works. All
discharges from the construction site should be controlled to comply with the
standards for effluents discharged into Victoria Harbour WCZ under the TM-DSS.
Construction Runoff
5.8.5
Exposed soil areas should be
minimised to reduce the potential for increased siltation, contamination of
runoff, and erosion. Construction runoff
related impacts associated with the above ground construction activities can be
readily controlled through the use of appropriate mitigation measures which
include:
·
use of sediment traps
·
adequate maintenance of drainage systems to prevent
flooding and overflow.
5.8.6
Construction site should be
provided with adequately designed perimeter channel and pre-treatment
facilities and proper maintenance.
The boundaries of critical areas of earthworks should be marked and
surrounded by dykes or embankments for flood protection. Temporary ditches should be provided to
facilitate runoff discharge into the appropriate watercourses, via a silt
retention pond. Permanent drainage
channels should incorporate sediment basins or traps and baffles to enhance
deposition rates. The design of
efficient silt removal facilities should be based on the guidelines in Appendix
A1 of ProPECC PN 1/94.
5.8.7
Ideally, construction works
should be programmed to minimise surface excavation works during the rainy
season (April to September). All
exposed earth areas should be completed as soon as possible after earthworks
have been completed, or alternatively, within 14 days of the cessation of
earthworks where practicable. If
excavation of soil cannot be avoided during the rainy season, or at any time of
year when rainstorms are likely, exposed slope surfaces should be covered by
tarpaulin or other means.
5.8.8
Sediment tanks of sufficient
capacity, constructed from pre-formed individual cells of approximately 6 to 8 m3 capacity, are recommended as a
general mitigation measure which can be used for settling surface runoff prior
to disposal. The system capacity is
flexible and able to handle multiple inputs from a variety of sources and
particularly suited to applications where the influent is pumped.
5.8.9
Open stockpiles of construction
materials (for examples, aggregates, sand and fill material) of more than 50 m3 should be covered with
tarpaulin or similar fabric during rainstorms. Measures should be taken to prevent the
washing away of construction materials, soil, silt or debris into any drainage
system.
5.8.10 Manholes (including newly constructed ones) should always be
adequately covered and temporarily sealed so as to prevent silt, construction
materials or debris being washed into the drainage system and storm runoff
being directed into foul sewers.
5.8.11 Precautions to be taken at any time of year when rainstorms are
likely, actions to be taken when a rainstorm is imminent or forecast, and
actions to be taken during or after rainstorms are summarised in Appendix A2 of
ProPECC PN 1/94. Particular
attention should be paid to the control of silty surface runoff during storm
events.
5.8.12 Oil interceptors should be provided in the drainage system and
regularly cleaned to prevent the release of oils and grease into the storm
water drainage system after accidental spillages. The interceptor should have a bypass to
prevent flushing during periods of heavy rain.
5.8.13 All vehicles and plant should be cleaned before leaving a
construction site to ensure no earth, mud, debris and the like is deposited by
them on roads. An adequately
designed and located wheel washing bay should be provided at every site exit,
and wash-water should have sand and silt settled out and removed at least on a
weekly basis to ensure the continued efficiency of the process. The section of access road leading to,
and exiting from, the wheel-wash bay to the public road should be paved with
sufficient backfall toward the wheel-wash bay to prevent vehicle tracking of
soil and silty water to public roads and drains.
Drainage
5.8.14 It is recommended that on-site drainage system should be installed
prior to the commencement of other construction activities. Sediment traps should be installed in
order to minimise the sediment loading of the effluent prior to discharge into
foul sewers. There shall be no
direct discharge of effluent from the site into the sea.
5.8.15 All temporary and permanent drainage pipes and culverts provided to
facilitate runoff discharge should be adequately designed for the controlled
release of storm flows. All
sediment control measures should be regularly inspected and maintained to
ensure proper and efficient operation at all times and particularly following
rain storms. The temporarily
diverted drainage should be reinstated to its original condition when the
construction work has finished or the temporary diversion is no longer
required.
5.8.16 All fuel tanks and storage areas should be provided with locks and
be located on sealed areas, within bunds of a capacity equal to 110% of the
storage capacity of the largest tank, to prevent spilled fuel oils from
reaching the coastal waters of Victoria Harbour WCZ.
Sewage Effluent
5.8.17 Construction work force sewage discharges on site are expected to be
connected to the existing trunk sewer or sewage treatment facilities. The construction sewage may need to be
handled by portable chemical toilets prior to the commission of the on-site
sewer system. Appropriate numbers
of portable toilets shall be provided by a licensed contractor to serve the
large number of construction workers over the construction site. The Contractor shall also be responsible
for waste disposal and maintenance practices.
Stormwater Discharges
5.8.18 Minimum distances of 100 m shall be maintained between the existing
or planned stormwater discharges and the existing or planned WSD flushing water
intakes.
Debris and Litter
5.8.19 In order to maintain water quality in acceptable conditions with
regard to aesthetic quality, contractors shall be required, under conditions of
contract, to ensure that site management is optimised and that disposal of any
solid materials, litter or wastes to marine waters does not occur.
Construction
Phase
5.9.1
General construction activities
associated with the construction of road works could lead to site runoff
containing elevated concentrations of SS and associated contaminants that may
enter into the marine water.
However, it is anticipated that the above water quality impacts will
generally be temporary and localised during construction. Therefore, no unacceptable residual
water quality impacts are anticipated during the construction of the proposed
infrastructure, provided all of the recommended mitigation measures are
implemented and all construction site / works area discharges comply with the
TM-DSS standards.
Operational Phase
5.9.2
Adverse water quality impacts
associated with the operation of the road works are not expected. Thus, there would be no unacceptable
residual impact associated with the operation of the Project.
Construction Phase
5.10.1
The potential water quality impacts
arising from the proposed land-based construction works for the road works have
been assessed. It is predicted that
there will not be any insurmountable adverse impacts on marine water
quality. With the implementation of
the recommended mitigation measures, it is anticipated that the identified
water quality impacts would be kept to within acceptable levels. Monitoring of marine water quality
during the construction phase is therefore not considered necessary for this
site.
5.10.2
Regular site
audit shall be carried out during construction stage to ensure that no adverse
impact on the marine waters and seawater intakes in the vicinity; and to
scrutinize timely implementation of the recommended mitigating measures.
Operational
Phase
5.10.3 No unacceptable water quality
impacts would be expected from the Project. No monitoring programme specific for
operational water quality would be required.
Construction
Phase
5.11.1 Water quality impacts from land-based construction are associated
with the surface runoff, effluent discharge from the site, and sewage from
on-site construction workers.
Impacts can be controlled to comply with the WPCO standards by
implementing the recommended mitigation measures. No unacceptable residual impacts on
water quality are anticipated.
Operational Phase
5.11.2 Potential water quality impact would be associated with surface road
runoff which may be contaminated by oils leaked from passing vehicles. It is considered that impacts upon water
quality will be minimal provided that the road works are designed with adequate
drainage systems and appropriate oil interceptors, as required.