10
Water
Quality Impact Assessment
This chapter presents the
assessment of potential water quality impacts, which may arise during the
construction and operation of the stabling sidings at Hung Hom Freight Yard. The Project also covers the modification of Hung
Hom (HUH) and construction of Kai Tak (KAT) and Diamond Hill (DIH) stations
designed based on the HHS option. Construction runoff, sewage from site
workforce and drainage diversion are potential sources of water quality impact
during the construction phase. Operational water quality impact includes track
run-off and seepage from tunnel section.
Mitigation measures have
been proposed to alleviate the potential water quality impact. Adverse residual
impacts during the construction and operational phases are not anticipated.
The relevant legislation
and associated guidance applicable to the present study for the assessment of
water quality impacts include:
·
Water Pollution
Control Ordinance (WPCO) CAP 358, Water Quality Objectives (WQOs) for the and
Victoria Harbour Water Control Zone (VHWCZ);
·
Technical
Memorandum for Effluents Discharged into Drainage and Sewerage Systems Inland
and Coastal Waters (TM on Effluent Standards under WPCO), Effluents discharge
limits for the Victoria Harbour Water Control Zone;
·
Environmental
Impact Assessment Ordinance (EIAO) (Cap. 499), Technical Memorandum on
Environmental Impact Assessment Process (TM-EIAO);
·
ProPECC PN 5/93
“Drainage Plan subject to Comment by the Environmental Protection Department”;
·
ProPECC PN 1/94
“Construction Site Drainage”; and
·
“Recommended Pollution Control Clauses for
Construction Contracts (RPCC)” issued by EPD.
10.3.1 Marine Water Quality Monitoring Stations Near to
Project Site
The representative marine water quality monitoring stations in the
vicinity of the Project site are VM2, VM4, VM5 and VM6 at the
Table 10.1: Marine Water Quality of
|
Parameter |
WQO |
Monitoring Station |
|||
|
|
|||||
|
VM2 |
VM4 |
VM5 |
VM6 |
||
|
Temperature (°C) |
Change due to waste discharge not to exceed
2°C |
23.8 (18.7 –
28.5) |
23.8 (18.6 –
28.6) |
24 (18.7 –
28.6) |
24 (18.7 –
28.6) |
|
Salinity (ppt) |
Change due to waste discharge not exceed 10%
of natural ambient level |
31.7 (22.5 –
33.5) |
31.8 (24.9 –
33.6) |
31.2 (21.4 –
33.4) |
31.4 (23.6 –
33.3) |
|
Dissolved Oxygen (mg/L) |
Depth average: ³ 4 mg/L
for 90% of samples |
5.6 (4.1 –
7.0) |
5.3 (4.1 –
6.7) |
5.2 (4.5 –
6.8) |
5.1 (4.5 –
6.3) |
|
Dissolved Oxygen, Bottom (mg/L) |
Bottom: ³ 2 mg/L
for 90% of samples |
5.5 (4.2 –
7.0) |
5.1 (2.6 –
6.8) |
5.2 (4.4 –
6.8) |
5.0 (3.4 –
6.6) |
|
SS (mg/L) |
Waste discharge not to raise the natural
ambient level by 30% nor cause the accumulation of suspended solids which may
adversely affect aquatic communities |
5.2 (2.7 –
8.3) |
5.8 (3.5 –
7.5) |
5.7 (3.3 –
9.1) |
6 (3.2 –
10.7) |
|
BOD5 (mg/L) |
N/A |
0.7 (<0.1
– 1.2) |
0.7 (0.2 –
1.2) |
0.8 (0.3 –
1.5) |
0.8 (0.1 –
1.7) |
|
NH3-N (mg/L) |
N/A |
0.08 (0.041
– 0.200) |
0.1 (0.049
– 0.203) |
0.12 (0.062
– 0.203) |
0.14 (0.069
– 0.227) |
|
Unionised Ammonia (mg/L) |
Annual mean not to exceed 0.021 mg/L |
0.003 (0.002
– 0.006) |
0.004 (0.001
– 0.007) |
0.005 (0.002
– 0.011) |
0.005 (0.001
– 0.009) |
|
TIN (mg/L) |
Annual mean depth-averaged TIN not to exceed
0.4 mg/L |
0.21 (0.07 –
0.60) |
0.24 (0.08 –
0.57) |
0.29 (0.12 –
0.63) |
0.32 (0.15 –
0.6) |
|
ChlorophyII-a (µg/L) |
N/A |
3.1 (0.7 –
9.1) |
3.3 (0.7 –
8.3) |
3.9 (0.7 –
10.1) |
3.7 (0.8 –
11.4) |
|
E. coli (cfu 100mL) |
N/A |
710 (100
–9400) |
2000 (510 – 8700) |
3900 (160 –
19000) |
2500 (200 – 11000) |
Notes:
[1] Data presented
are depth averaged, except as specified.
[2] Data
presented are annual arithmetic mean except for E. coli, which are
geometric mean values
[3] Data
enclosed in brackets indicate the ranges
[4] Bolded cells
indicate non-compliance with the WQOs for a parameter
10.3.2
River Water Quality Monitoring Stations Near
to Project Site
The representative river water quality monitoring stations in the
vicinity of the Project site are KN1, KN2, KN3, KN4, KN5 and KN7 at Kai Tak
Nullah (see Figure 10.2 for their locations). Water quality parameters
monitored at these stations are given in EPD’s River Water Quality Report 2009[10-2],
and the major parameters are summarized in Table 10.2 below.
Table 10.2: River Water Quality
of Kai Tak Nullah in Year 2009
|
Parameter |
WQO |
Kai Tak Nullah |
|||||
|
Monitoring Station |
|||||||
|
KN1 |
KN2 |
KN3 |
KN4 |
KN5 |
KN7 |
||
|
Dissolved Oxygen (mg/L) |
³
4 mg/L |
6.6 (5.1 –
7.5) |
7.0 (6.3 –
7.7) |
7.2 (7.1 –
8) |
7.9 (6.8 –
8.5) |
7.9 (7.1 –
8.7) |
7.4 (7.0 –
8.4) |
|
pH |
Not to
exceed the range of 6.0-9.0 units |
7.1 (6.9 –
7.6) |
7.3 (7.0 –
7.6) |
7.3 (7.1 –
7.7) |
7.3 (7.0 –
7.6) |
7.3 (6.9 –
7.5) |
7.2 (6.9 –
7.4) |
|
SS (mg/L) |
Annual
median not to exceed 25 mg/L |
4 (3 – 32) |
8 (3 –
24) |
6 (4 –
19) |
11 (3 –
38) |
5 (3 –
12) |
5 (2 –
11) |
|
BOD5 (mg/L) |
≤ 5 mg/L |
4
(<1 – 6) |
3 (2 –
6) |
4 (2 –
8) |
6 (2 –
31) |
3 (1 –
8) |
3 (1 –
10) |
|
COD (mg/L) |
≤ 30
mg/L |
26 (18
– 40) |
28 (23
– 34) |
29 (23
– 39) |
32 (19
– 50) |
27 (19 – 34) |
31 (19 – 33) |
|
E. coli (cfu / 100mL) |
≤ 1000 cfu/100mL, geometric
mean of the most recent 5 consecutive samples taken at intervals of between 7
and 21 days |
85000 (8000 –
880000) |
35000 (6000 –
120000) |
56000 (11000
– 240000) |
87000 (7800 –
1300000) |
21000 (8500 –
52000) |
23000 (8000 –
40000) |
|
NH4-N (mg/L) |
N/A |
0.74 (0.33 –
2.80) |
0.49 (0.1 –
1.6) |
0.48 (0.13 –
1.5) |
0.57 (0.09 –
2.20) |
0.27 (0.08 –
1.70) |
0.26 (0.08 –
1.5) |
Notes:
[1] Data presented are annual
median except for E. coli, which are annual geometric mean values.
[2] Data enclosed in
brackets indicate the ranges
Kai Tak Nullah’s catchment includes some of the
most densely populated areas of
Within the study area of the Project, there is only one water receiving
body in the vicinity of the construction of DIH. The upper end of Kai Tak
Nullah at former
There is no marine biological sensitive receiver such as fish culture
zone, shellfish culture zone, marine park/reserve and commercial fishing ground
in the vicinity of SCL (HHS).
In addition, no marine works will be required for the Project.
The representative Water Sensitive Receiver
(WSR) in the vicinity of the Project site is summarized in Table 10.3 below and shown in Figure 10.3.
Table 10.3: Water sensitive receivers
|
WSR No. |
WSRs Description |
Works Area |
|
WSR 1 |
Kai Tak Nullah |
Construction of DIH |
Since there is no planned/existing activity that may affect the water quality
at WSR1 (Kai Tak Nullah) and the nearby nullah sections, the water quality at
the closest monitoring station, i.e. Station KN7 (see Table
10.2) which was graded
““Excellent” of Water Quality Index (WQI) in 2009, could be adopted as the
baseline water quality.
The site will be maintained by good site practices and there will be no
direct discharge of wastewater into
10.5.1 Pollution Sources from Construction Activities
Potential water pollution sources during construction phase will include
sources mainly from land-based activities as follows:
·
Construction
runoff;
·
Runoff from
tunnelling activities and underground works (mainly at DIH);
·
Sewage effluent
due to workforce on site;
·
Drainage diversion
near HUH and DIH;
·
Groundwater
seepage; and
·
Accidental
Spillage.
10.5.1.1
Construction
Runoff
Construction site runoff comprises:
·
Runoff and erosion
from site surfaces, drainage channels, earth working areas and stockpiles;
·
Wash water from
dust suppression sprays and wheel washing facilities; and
·
Fuel, oil,
solvents and lubricants from maintenance of construction machinery and
equipment.
Construction runoff may cause physical, biological and chemical effects.
The physical effects include potential blockage of drainage channels and
increase of Suspended Solid (SS) levels in VHWCZ.
Local flooding may also occur in heavy rainfall situations. The chemical
and biological effects caused by the construction runoff are highly dependent
upon its chemical and nutrient content.
Runoff containing significant amounts of concrete and cement-derived
material may cause primary chemical effects such as increasing turbidity and
discoloration, elevation in pH, and accretion of solids. A number of secondary
effects may also result in toxic effects to water biota due to elevated pH
values, and reduced decay rates of faecal micro-organisms and photosynthetic
rate due to the decreased light penetration.
10.5.1.2
Tunnelling
Activities and Underground Works
During construction works and rainfall, surface runoff and groundwater
seepage pumped out would have high SS content. The situation would be worse
during wet seasons.
Surface runoff may also be contaminated by bentonite and grouting
chemicals that would be required for the construction of bored tunnel (for
tunnel boring and ground treatment) at DIH and diaphragm walls for
cut-&-cover at DIH and tunnel section at KAT. In addition, wastewater from
construction works will also contain a high concentration of SS.
10.5.1.3
Sewage Effluent
Sewage effluents will arise from the sanitary facilities used by the
construction workforce. The characteristics of sewage would include high levels
of BOD5, Ammonia and E. coli counts.
Sewage from chemical
toilets will also be generated. The sludge needs to be properly managed to
minimize odour and potential health risks to the workforce by attracting pests
and other disease vectors.
The number of construction
workers to be employed on site is not available at this stage, but is
anticipated to be over 450 staff in
the peak period. As the workers will be scattered within the construction site,
the most effective solution will be to provide adequate number of portable
toilets within the site to ensure that sewage from site staff is properly
collected. Depending on site conditions, land availability and site activities,
the locations and number of portable toilets will be determined in the
Environmental Management Plan (EMP) to be submitted by the Contractor. No
adverse water quality impact is envisaged provided that maintenance by licensed
contractors is conducted regularly.
10.5.1.4
Drainage Diversion
Drainage diversion will be undertaken near HUH and DIH. A Drainage
Impact Assessment will be prepared and submitted by the Project Proponent
separately. The assessment will identify the diversion or upgrading of the
existing drainage infrastructure. The potential water quality impact associated
with the drainage diversion or upgrading will be from the run-off and erosion
from site surfaces and earth working areas. Small amount of wastewater may be
released during the disconnection of various drainage systems.
10.5.1.5
Groundwater
Seepage
The construction of DIH and KAT, as well as the refuge sidings at KAT
will be constructed by a combination of open-cut and cut-&-cover method.
Construction methodology using diaphragm wall (D-wall) techniques can minimise
the intrusion of groundwater during excavation. It involves excavation of a
narrow trench that is kept full of slurry, which exerts hydraulic pressure
against the trench walls and acts as a shoring to prevent collapse. Slurry
trench excavations can be performed in all types of soil, even below the ground
water table.
The construction usually begins with the excavation of discontinuous
primary panels of typically up to 6m long and down to the rockhead. In order to provide an effective cut-off to
ground water flow, the walls will need to be toe grouted. Once the excavation
of a panel is completed, a steel reinforcement cage will be placed in the
centre of the panel. Concrete is then poured in one continuous operation. Once
the primary panels are set, secondary panels will be constructed between the
primary panels and the process then repeats to create a continuous wall. It
should be noted that this slurry trench method will reduce the gap between the
panels to the practicable minimum. After this, soil excavation will be
commenced. The intrusion of groundwater through D-wall panels during soil
excavation is therefore considered insignificant.
10.5.1.6
Groundwater from
Contaminated Area
As the Study Area of this Project overlaps
with part of the assessment area under the EIA study for the SCL (MKK-HUH) and
SCL (TAW-HUH), relevant documents from these 2 EIA studies have been reviewed.
According to the approved CARs of SCL (MKK-HUH) and SCL (TAW-HUH), site
investigation (SI) works were carried out from March 2008 to December 2010 and
February 2009 to August 2009 respectively. A total of 14 groundwater samples
had been tested and it is confirmed that no contaminated site was identified
within the Study Area of this Project according to the SI results. Groundwater
quality is therefore not anticipated to be affected by the discharge/ recharge
of groundwater generated from the Project.
10.5.1.7
Accidental
Spillage
There will be no direct discharge of wastewater into the
10.6.1 Pollution Sources & Prediction of Impacts
Potential sources of water quality impact during the operational phase
are summarised below:
·
Track runoff from
train stabling sidings under the podium and tunnel (covered section);
·
Track runoff from
fan area to the north of stabling sidings and launching/ retrieval tracks to
the south of stabling sidings (open track section);
·
Station runoff;
and
·
Sewage from
station and train stabling sidings operation.
10.6.1.1
Track Runoff from
Train Stabling Sidings and Tunnel (Covered Section)
Track runoff from the train stabling sidings under the podium structure
and tunnel (covered section) is expected to contain limited amounts of oil and
grease. Since all tracks are contained in concrete tunnel box, there will be no
rainwater runoff. The tunnel wall will be equipped with water-tight liner and
design for no seepage. The amount of groundwater seepage into the tunnel will
be insignificant. Where oils and lubricating fluids could be spilled and light
maintenance activities such as track washing would be conducted occasionally,
runoff should be diverted to silt traps and oil/ grease interceptors before
discharge to the public foul system. No
adverse water quality impact is anticipated.
10.6.1.2
Track Runoff from
Fan Area and Launching/ Retrieval Tracks (Open Track Section)
Track runoff from the fan area and launching/ retrieval tracks is
expected to contain limited amounts of oil and grease. Where oils and lubricating
fluids could be spilled and track washing would be conducted occasionally,
runoff should be diverted to silt traps and oil/ grease interceptors before
discharge to the existing public storm water drain system. No adverse water
quality impact is anticipated.
10.6.1.3
Station Runoff
Rainwater runoff from the station structure and associated facilities at
HUH would not be contaminated and hence has no adverse water quality impact.
10.6.1.4 Sewage
from Station
A separate consultant will be appointed by the Project Proponent to
conduct the detailed design of sewer for HUH, KAT and DIH. A Sewerage Impact
Assessment will be conducted and submitted to the relevant government
departments for approval separately. The typical Average Dry Weather Flow
(ADWF) for a train station (without top-side properties) would be about 0.8l/s,
which would be equivalent to about 55m3/day, assuming 19 hours of
operation. It is therefore anticipated
that the ADWF for each station would be of similar order and probably in the
order of 50-100m3 /day. Given the small quantity of the ADWF for
each station, the capacity of the existing foul sewer is adequate for the
proposed sewage discharge. Hence, no
water quality impact is anticipated.
10.6.1.5
Sewage from Train
Stabling Sidings Operation
Sewage effluents generated by the on-site work force will be discharged
to the public foul system and potential water quality impact is therefore not
anticipated.
Only inspection and some minor maintenancewould be conducted in the
siding area. These routine operational
activities of the train stabling sidings may release oil and grease residues.
These oily and greasy residues can be dripped, washed or spilled onto the ground
surface within a working area. In areas where runoff could be contaminated by
oil and grease from those minor maintenance activities, oil interceptors are
recommended for separating oil from water prior to discharge. As the sewage
will be treated as necessary to satisfy the discharge standards in the TM on
Effluent Standards under WPCO, no adverse water quality impacts would be
expected.
In accordance with the Practice Note for Professional Persons on
Construction Site Drainage, Environmental Protection Department, 1994 (ProPECC
PN 1/94), construction phase mitigation measures shall include the following:
10.7.1.1 Construction
Runoff and Site Drainage
·
At the start of
site establishment, perimeter cut-off drains to direct off-site water around
the site should be constructed with internal drainage works and erosion and
sedimentation control facilities implemented.
Channels (both temporary and permanent drainage pipes and culverts),
earth bunds or sand bag barriers should be provided on site to direct
stormwater, e.g. Kai Tak Nullah (WSR 1), to silt removal facilities. The design of the temporary on-site drainage
system will be undertaken by the contractor prior to the commencement of
construction.
·
The dikes or
embankments for flood protection should be implemented around the boundaries of
earthwork areas. Temporary ditches should be provided to facilitate the runoff
discharge into an appropriate watercourse, through a site/sediment trap. The
sediment/silt traps should be incorporated in the permanent drainage channels
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, which states that the
retention time for silt/sand traps should be 5 minutes under maximum flow
conditions. Sizes may vary depending
upon the flow rate, but for a flow rate of 0.1 m3/s a sedimentation
basin of 30m3 would be required and for a flow rate of 0.5 m3/s
the basin would be 150 m3.
The detailed design of the sand/silt traps shall be undertaken by the Contractor
prior to the commencement of construction.
·
All exposed earth
areas should be completed and vegetated as soon as possible after earthworks
have been completed, or alternatively, within 14 days of the cessation of
earthworks where practicable. Exposed slope surfaces should be covered by
tarpaulin or other means.
·
All drainage
facilities and erosion and sediment control structures should be regularly
inspected and maintained to ensure proper and efficient operation at all times
and particularly following rainstorms.
Deposited silt and grit should be removed regularly and disposed of by
spreading evenly over stable, vegetated areas.
·
Measures should be
taken to minimise the ingress of site drainage into excavations. If the excavation of trenches in wet periods
is necessary, they should be dug and backfilled in short sections wherever
practicable. Water pumped out from
trenches or foundation excavations should be discharged into storm drains via
silt removal facilities.
·
Open stockpiles of
construction materials (for example, aggregates, sand and fill material) of
more than 50m3 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.
·
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.
·
Precautions be
taken at any time of year when rainstorms are likely, actions to be taken when
a rainstorm is imminent or forecasted, 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, especially for areas
located near steep slopes.
·
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 sited wheel
washing facilities should be provided at every construction site exit where
practicable. 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.
·
Oil interceptors
should be provided in the drainage system downstream of any oil/fuel pollution
sources. The oil interceptors should be emptied and cleaned regularly to
prevent the release of oil and grease into the storm water drainage system
after accidental spillage. A bypass should be provided for the oil interceptors
to prevent flushing during heavy rain.
·
Construction solid
waste, debris and rubbish on site should be collected, handled and disposed of
properly to avoid water quality impacts.
Requirements for solid waste management are detailed in Section 11 of this EIA Report.
·
All fuel tanks and
storage areas should be provided with locks and sited 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 water sensitive receivers nearby.
·
By adopting the
above mitigation measures with Best Management Practices (BMPs) it is
anticipated that the impacts of construction site runoff from the construction
site will be reduced to an acceptable level before discharges.
·
All the earth
works involving should be conducted sequentially to limit the amount of
construction runoff generated from exposed areas during the wet season (April
to September) as far as practicable.
·
In general, no
direct wastewater discharge should be allowed to Kai Tak Nallah, unless a
discharge license has been obtained in accordance with the requirements of the
WPCO.
10.7.1.2 Tunnelling
Works and Underground Works
·
Cut-&-cover/ open
cut tunnelling work should be conducted sequentially to limit the amount of
construction runoff generated from exposed areas during the wet season (April
to September) as far as practicable.
·
Uncontaminated
discharge should pass through sedimentation tanks prior to off-site discharge.
·
The wastewater
with a high concentration of SS should be treated (e.g. by sedimentation tanks
with sufficient retention time) before discharge. Oil interceptors would also
be required to remove the oil, lubricants and grease from the wastewater.
·
Direct discharge
of the bentonite slurry (as a result of D-wall and bored tunnelling
construction) is not allowed. It should be reconditioned and reused wherever
practicable. Temporary storage locations
(typically a properly closed warehouse) should be provided on site for any
unused bentonite that needs to be transported away after all the related
construction activities are completed. The requirements in ProPECC PN 1/94
should be adhered to in the handling and disposal of bentonite slurries.
10.7.1.3
Sewage Effluent
Adequate numbers of
portable toilets should be provided for handling the construction
sewage generated by the workforce. The
portable toilets should be maintained in a reasonable state, which will not
deter the workers from utilizing these portable toilets. Overnight sewerage should be collected by
licensed collectors regularly.
10.7.1.4
Groundwater Seepage
As some proposed works areas at Hung Hom are near
10.7.1.5
Groundwater from
Contaminated Area
Groundwater quality is not anticipated to be affected by the discharge/
recharge of groundwater generated from the Project since no contaminated site
was identified. Thus, mitigation measures are not required, provided that the
groundwater would be discharged in accordance with the requirements of the
TM-Water.
10.7.1.6
Accidental Spillage
In order to prevent accidental spillage of chemicals, proper storage and
handling facilities should be provided. All the tanks, containers, storage area
should be bunded and the locations should be locked as far as possible from the
sensitive watercourse and stormwater drains. The Contractor should register as
a chemical waste producer if chemical wastes would be generated. Storage of
chemical waste arising from the construction activities should be stored with
suitable labels and warnings. Disposal of chemical wastes should be conducted
in compliance with the requirements as stated in the Waste disposal (Chemical
Waste) (General) Regulation.
Mitigation measures are only required to mitigate runoff from train
stabling sidings during the operational phase. The following mitigation
measures during operational phase are recommended:
·
Track runoff from
train stabling sidings (covered section) and tunnel should pass through
oil/grit interceptors/chambers to remove oil, grease and sediment before being
pumped to the public foul drainage system;
·
Track runoff from
the fan area and launching/ retrieval tracks (open track section)should pass
through oil/grit interceptors/chambers to remove oil, grease and sediment
before being pumped to the public storm water drain system;
·
The silt traps and
oil interceptors should be cleaned and maintained regularly; and
·
Oily contents of
the oil interceptors should be transferred to an appropriate disposal facility,
or to be collected for reuse, if possible.
Information on
concurrent projects is presented in Section
1. As discussed in Section 10.5,
there would be no direct discharge of wastewater and it is considered that
quantitative prediction in cumulative impact is not applicable. As all the Project
works would be land-based and provided that proper mitigation measures will be
implemented by these concurrent projects, the water quality impact generated
from these projects would be localized and no adverse cumulative water quality
impacts would be expected.
Adverse residual impacts during the construction and operational phases
are not anticipated provided that the above mitigation measures are
implemented.
Potential water pollution
sources have been identified as construction runoff, sewage from site
workforce, groundwater seepage and accidential spillage. Mitigation measures
including covering excavated materials and providing sedimentation tanks
on-site etc are recommended to mitigate any adverse water quality impacts.
The operational water
quality impact for track run-off and tunnel seepage will have no adverse water
quality impact provided that mitigation measures are incorporated in the
design.
All proposed mitigation measures
are defined in the Environmental Mitigation Implementation Schedule.
[10-1] EPD (2009) Marine Water Quality Report
2009
[10-1] EPD (2009) River Water Quality Report
2009