5
water quality Impact
5.1.1.1
This section presents an assessment of the
potential water quality impacts associated with the construction and operation
of the Project. Mitigation measures have
been proposed if considered necessary to minimize the identified water quality
impacts.
5.2
Environmental Legislation, Standards and Guidelines
5.2.1
Environmental Impact Assessment Ordinance (EIAO)
5.2.1.1
Technical Memorandum on Environmental Impact
Assessment Process (EIAO-TM) was issued by EPD under Section 16 of the EIAO. The EIAO-TM specifies assessment methodologies
and criteria that are to be followed in an EIA Study. Sections relevant to water quality impact
assessment comprise:
·
Annex 6 - Criteria for
Evaluating Water Pollution; and
·
Annex 14 - Guidelines for
Assessment of Water Pollution.
5.2.2
Water Quality Objectives
5.2.2.1
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 (WQOs) are
stipulated for different water regimes (marine waters, inland waters, bathing
beaches subzones, secondary contact recreation subzones and fish culture
subzones) in each WCZ based on their beneficial uses. The Project site is located within the Western Buffer and Victoria
Harbour (Phase One) WCZs and the WQOs for the Western Buffer and Victoria
Harbour (Phase One) WCZs are listed in Table 5.1
and Table 5.2
respectively.
Table 5.1 Summary of Water Quality
Objectives for Western Buffer WCZ
|
Parameters
|
Criteria
|
Subzone
|
|
Aesthetic appearance
|
There should be no
objectionable odours or discolouration of the water.
|
Whole
Zone
|
|
|
Tarry residues,
floating wood, articles made of glass, plastic, rubber or of any other
substances should be absent.
|
|
|
|
Mineral oil should not
be visible on the surface. Surfactants should not give rise to a lasting
foam.
|
|
|
|
There should be no
recognisable sewage-derived debris.
|
|
|
|
Floating, submerged and
semi-submerged objects of a size likely to interfere with the free movement
of vessels, or cause damage to vessels, should be absent.
|
|
|
|
The water should not
contain substances which settle to form objectionable deposits.
|
|
|
Bacteria
|
The level of Escherichia
coli
should not exceed 610 per 100 mL, calculated as the geometric mean of all
samples collected in one calendar year.
|
Secondary
Contact Recreation Subzones and Fish Culture Subzones
|
|
|
The level of Escherichia
coli
should not exceed 180 per 100 mL, calculated as the geometric mean of all
samples collected from March to October inclusive in 1 calendar year. Samples
should be taken at least 3 times in 1 calendar month at intervals of between
3 and 14 days.
|
Recreation
Subzones
|
|
|
The level of Escherichia
coli
should be less than 1 per 100 mL, calculated as the geometric mean of the
most recent 5 consecutive samples taken at intervals of between 7 and 21
days.
|
Water
Gathering Ground Subzones
|
|
|
The level of Escherichia
coli
should not exceed 1000 per 100 mL, calculated as the geometric mean of the
most recent 5 consecutive samples taken at intervals of between 7 and 21
days.
|
Other
inland waters
|
|
Dissolved Oxygen (DO) within 2 m of the seabed
|
The level of dissolved
oxygen should not be less than 2 mg/L for 90% of the sampling occasions
during the whole year.
|
Marine
waters, including Fish Culture Subzones
|
|
Dissolved Oxygen (DO)
|
The level of dissolved
oxygen should not be less than 4 mg/L for 90% of the sampling occasions
during the whole year, calculated as water column average.
|
Marine
waters excepting Fish Culture Subzones
|
|
|
The level of dissolved
oxygen should not be less than 5 mg/L for 90% of the sampling occasions
during the year, calculated as water column average.
|
Fish
Culture Subzones
|
|
|
The level of dissolved
oxygen should not be less than 4 mg/L.
|
Water
Gathering Ground Subzones and other inland waters
|
|
Colour
|
Human
activity should not cause the colour of water to exceed 30 Hazen units.
|
Water Gathering Ground Subzones
|
|
|
Human activity should
not cause the colour of water to exceed 50 Hazen units.
|
Other
inland waters
|
|
pH
|
The pH of the water
should be in the range of 6.5-8.5, human activity should not cause the
natural pH range to be extended by more than 0.2 unit.
|
Marine
waters
|
|
|
The pH of the water
should be in the range of 6.5-8.5.
|
Water
Gathering Ground Subzones
|
|
|
The pH of the water
should be in the range of 6.0-9.0.
|
Other
inland waters
|
|
Temperature
|
Waste discharges shall
not cause the natural daily temperature range to change by more than 2 ℃.
|
Whole
Zone
|
|
Salinity
|
Waste discharges shall
not cause the natural ambient salinity level to change by more than 10%.
|
Whole
Zone
|
|
Suspended Solids (SS)
|
Human activity shall
neither cause the natural ambient SS level to be raised by more than 30% nor
give rise to accumulation of SS which may adversely affect aquatic
communities.
|
Marine
waters
|
|
|
Human activity shall
not cause the annual median of SS to exceed 20 mg/L.
|
Water
Gathering Ground Subzones
|
|
|
Human activity should
not cause the annual median of suspended solids to exceed 25 mg/L.
|
Other
inland waters
|
|
Un-ionized ammonia (UIA)
|
The un-ionized
ammoniacal nitrogen level should not be more than 0.021 mg/L, calculated as
the annual average (arithmetic mean).
|
Whole
Zone
|
|
Nutrients
|
(a) Nutrients shall not be
present in quantities sufficient to cause excessive or nuisance growth of
algae or other aquatic plants.
|
Marine
waters
|
|
|
(b) Without limiting the generality
of objective (a) above, the level of inorganic nitrogen should not exceed 0.4
mg/L, expressed as annual water column average.
|
Marine
waters
|
|
5-Day Biochemical Oxygen Demand (BOD5)
|
Waste discharges shall
not cause the 5-day biochemical oxygen demand to exceed 3 mg/L.
|
Water
Gathering Ground Subzones
|
|
|
Waste discharges shall
not cause the 5-day biochemical oxygen demand to exceed 5 mg/L.
|
Other
inland waters
|
|
Chemical Oxygen Demand (COD)
|
Waste discharges shall
not cause the chemical oxygen demand to exceed 15 mg/L.
|
Water
Gathering Ground Subzones
|
|
|
Waste discharges shall
not cause the chemical oxygen demand to exceed 30 mg/L.
|
Other
inland waters
|
|
Toxins
|
Waste discharges shall
not cause the toxins in water to attain such levels as to produce significant
toxic, carcinogenic, mutagenic or teratogenic
effects in humans, fish or any other aquatic organisms, with due regard to
biologically cumulative effects in food chains and to toxicant interactions
with each other.
|
Whole
Zone
|
|
|
Waste discharges shall
not cause a risk to any beneficial uses of the aquatic environment.
|
Whole
Zone
|
|
Turbidity
|
Waste discharges shall
not reduce light transmission substantially from the normal level.
|
Bathing
Beach Subzones
|
Note:
(1)
The table is
referenced to the Statement of Water Quality Objectives (Western Buffer Water
Control Zone).
Table 5.2 Summary of Water Quality
Objectives for Victoria Harbour (Phase One) WCZ
|
Parameters
|
Criteria
|
Subzone
|
|
Aesthetic appearance
|
There should be no
objectionable odours or discolouration of the water.
|
Whole
Zone
|
|
|
Tarry residues,
floating wood, articles made of glass, plastic, rubber or of any other
substances should be absent.
|
|
|
|
Mineral oil should not
be visible on the surface. Surfactants should not give rise to a lasting
foam.
|
|
|
|
There should be no
recognisable sewage-derived debris.
|
|
|
|
Floating, submerged and
semi-submerged objects of a size likely to interfere with the free movement
of vessels, or cause damage to vessels, should be absent.
|
|
|
|
The water should not
contain substances which settle to form objectionable deposits.
|
|
|
Bacteria
|
The level of Escherichia
coli
should not exceed 1000 per 100 mL, calculated as the geometric mean of the
most recent 5 consecutive samples taken at intervals of between 7 and 21
days.
|
Inland
waters
|
|
Colour
|
Human activity should
not cause the colour of water to exceed 50 Hazen units.
|
Inland
waters
|
|
Dissolved Oxygen (DO) within 2 m of the seabed
|
The level of dissolved
oxygen should not be less than 2 mg/L for 90% of the sampling occasions
during the whole year.
|
Marine
waters
|
|
Dissolved Oxygen (DO)
|
The level of dissolved
oxygen should not be less than 4 mg/L for 90% of the sampling occasions
during the year, calculated as the annual water column average
|
Marine
waters
|
|
|
The level of dissolved
oxygen should not be less than 4 mg/L.
|
Inland
waters
|
|
pH
|
The pH of the water
should be in the range of 6.5-8.5, human activity should not cause the
natural pH range to be extended by more than 0.2 unit.
|
Marine
waters
|
|
|
Human activity should
not cause the pH of the water to exceed the range of 6.0‒9.0 units.
|
Inland
waters
|
|
Temperature
|
Waste discharges shall
not cause the natural daily temperature range to change by more than 2 ℃.
|
Whole
Zone
|
|
Salinity
|
Waste discharges shall
not cause the salinity level to change by more than 10%.
|
Whole
Zone
|
|
Suspended Solids (SS)
|
Human activity shall
neither cause the natural ambient SS level to be raised by more than 30% nor
give rise to accumulation of SS which may adversely affect aquatic
communities.
|
Marine
waters
|
|
|
Human activity shall
not cause the annual median of SS to exceed 25 mg/L.
|
Inland
waters
|
|
Un-ionized ammonia (UIA)
|
The un-ionized
ammoniacal nitrogen level should not be more than 0.021 mg/L, calculated as
the annual average (arithmetic mean).
|
Whole
Zone
|
|
Nutrients
|
(a) Nutrients shall not be present
in quantities sufficient to cause excessive or nuisance growth of algae or
other aquatic plants.
|
Marine
waters
|
|
|
(b) Without limiting the
generality of objective (a) above, the level of inorganic nitrogen should not
exceed 0.4 mg/L, expressed as annual water column average.
|
Marine
waters
|
|
5-Day Biochemical Oxygen Demand (BOD5)
|
The 5-day biochemical
oxygen demand should not exceed 5 mg/L.
|
Inland
waters
|
|
Chemical Oxygen Demand (COD)
|
The chemical oxygen
demand should not exceed 30 mg/L
|
Inland
waters
|
|
Toxins
|
Waste discharges shall
not cause the toxins in water to attain such levels as to produce significant
toxic, carcinogenic, mutagenic or teratogenic
effects in humans, fish or any other aquatic organisms, with due regard to
biologically cumulative effects in food chains and to toxicant interactions
with each other.
|
Whole
Zone
|
|
|
Waste discharges shall
not cause a risk to any beneficial uses of the aquatic environment.
|
Whole
Zone
|
Notes:
(1)
The table is
referenced to the Statement of Water Quality Objectives (Victoria Harbour
(Phase One) Water Control Zone).
5.2.3
Technical Memorandum on Standards for Effluents
Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters
5.2.3.1
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), issued
under Section 21 of the WPCO, gives guidance on 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 effluent. Any effluent discharges from the proposed
construction and operational activities must comply with the standards for
effluent discharged into the foul sewers, inland waters and coastal waters of
the Western Buffer and Victoria Harbour (Phase One)
WCZs provided in the TM-DSS.
5.2.4
Practice Notes
5.2.4.1
The Professional Persons Environmental
Consultative Committee Practice Note on "Construction Site Drainage"
(ProPECC PN 1/94) provides good practice guidelines
for dealing with 10 types of discharge from construction sites. These include
surface run-off, groundwater, boring and drilling water, wastewater from
concrete batching and precast concrete casting, wheel washing 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.
5.2.4.2
The ProPECC PN 5/93
"Drainage Plans subject to Comments by Environmental Protection
Department" provides guidelines and practices for handling, treatment and disposal of various effluent discharges to
stormwater drains and foul sewers. The design of site drainage and disposal of
various site effluents generated within the new development area should follow
the relevant guidelines and practices as given in the ProPECC
PN 5/93.
5.2.5
Technical Circular
5.2.5.1
Environment, Transport and Works Bureau
Technical Circular (Works) (ETWB TC(W)) No. 5/2005 provides an administrative
framework to better protect all natural streams/rivers from the impacts of
construction works. The procedures
promulgated under this Circular aim to clarify and strengthen existing measures
for protection of natural streams/rivers from government projects and private
developments. The guidelines and precautionary mitigation measures given in the
ETWB TC(W) No. 5/2005 should be followed as far as possible to protect the
inland watercourses at or near the Project area during the construction phase.
5.2.6.1
Besides the WQOs set under the WPCO, WSD has
specified a set of criteria for water quality at flushing water intakes as
shown in Table 5.3.
Table 5.3 WSD’s Water Quality Criteria
for Flushing Water at Sea Water Intakes(1)
|
Parameter (in mg L-1 unless
otherwise stated)
|
Target
Limit
|
|
Colour (HU)
|
< 20
|
|
Turbidity (NTU)
|
< 10
|
|
Threshold Odour Number (odour unit)
|
< 100
|
|
Ammonia Nitrogen (NH3-N)
|
< 1
|
|
Suspended Solids (SS)
|
< 10
|
|
Dissolved Oxygen (DO)
|
> 2
|
|
5-day Biochemical Oxygen Demand (BOD5)
|
< 10
|
|
Synthetic Detergents
|
< 5
|
|
E. coli
(no. per 100 mL)
|
< 20,000
|
5.3.1
Study Area
5.3.1.1
The Study Area for this water quality impact
assessment includes areas within 500 metres from the
boundary of the Project and it falls within both the Western Buffer and
Victoria Harbour (Phase One) WCZs as designated under
the WPCO (Cap. 358).
5.3.2
Marine Water
5.3.2.1
The baseline water quality of the Study Area have been established with reference to routine water
quality monitoring data collected by EPD. The EPD’s marine water quality
monitoring stations WM4 in the Western Buffer WCZ, and VM12, VM14 and VT8 in
the Victoria Harbour (Phase One) WCZ are the closest
marine water quality monitoring stations to the Project site. Marine water quality monitoring data
collected by EPD in 2021 for WM4 as well as VM12, VM14 and VT8 are
summarized in Table 5.4 and Table 5.5 respectively. Locations
of these monitoring stations are illustrated in Figure 5.1. Descriptions of the
baseline water quality conditions provided in the subsequent sections are based
on the EPD’s report “Marine Water Quality in Hong Kong in 2021.
5.3.2.2
The Victoria Harbour
WCZ achieved an overall WQO compliance rate of 100% in 2021. The E. coli
level in the eastern side of Victoria Harbour has
decreased markedly since the implementation of HATS Stage 1 in 2001. The annual
Cross Harbour Swim, suspended since 1979 because of
poor water quality, was resumed on the eastern side of the harbour
in 2011 after implementation of the HATS ADF. With full commissioning of the
HATS Stage 2A, the E. coli level of the central harbour
area has been further reduced. Since 2017, the race route of the event has
returned to the traditional route in the central harbour
area.
5.3.2.3
The Western Buffer WCZ fully achieved the WQOs
in 2021. Since the commissioning of the HATS ADF in 2010, the E. coli
level in the WCZ decreased. Similar to other WCZs in the central waters, significant
improvement of water quality in terms of E. coli and PO4-P
has been observed.
Table 5.4 Summary of Marine Water
Quality Monitoring Data Collected by EPD in 2021 for WM4
|
Parameters
|
Tsing Yi (West)
|
WQO for Western Buffer WCZ (Marine Waters)
|
|
WM4
|
|
Temperature (°C)
|
24.4
(19.8 - 28.4)
|
Not more than 2℃ change in daily temperature range
|
|
Salinity
|
31.5
(29.1 - 33.5)
|
Not to cause more
than 10% change
|
|
Dissolved Oxygen
(mg/L)
|
Depth Average
|
4.6
(3.6 - 5.6)
|
Marine waters
except Fish Culture Subzone: Not less than 4 mg/L for 90% of the sampling
occasions during the whole year
Fish Culture
Subzone: Not less than 5 mg/L for 90% of the sampling occasions during the
whole year
|
|
|
Bottom
|
4.2
(2.4 - 6.0)
|
Marine waters
including Fish Culture Subzones: Not less than 2 mg/L for 90% of the sampling
occasions during the whole year
|
|
Dissolved Oxygen
(% Saturation)
|
Depth Average
|
65
(52 - 81)
|
Not available
|
|
|
Bottom
|
60
(35 - 84)
|
Not available
|
|
pH
|
7.5
(7.2 - 7.9)
|
Marine waters:
6.5 - 8.5 (±0.2 from natural range)
|
|
Secchi Disc Depth
(m)
|
2.5
(1.6 - 4.4)
|
Not available
|
|
Turbidity
(NTU)
|
6.5
(3.7 - 11.3)
|
Bathing Beach
Subzones: Not reduce light transmission substantially from the normal level
|
|
Suspended Solids (SS)
(mg/L)
|
6.5
(1.9 - 11.4)
|
Not more than 30%
increase in natural ambient level
|
|
5-day Biochemical
Oxygen Demand (BOD5) (mg/L)
|
0.8
(0.3 - 1.5)
|
Not available
|
|
Ammonia Nitrogen (NH3-N)
(mg/L)
|
0.122
(0.056 - 0.210)
|
Not available
|
|
Unionised Ammonia
(mg/L)
|
0.002
(<0.001 - 0.007)
|
Not more than
annual average of 0.021mg/L
|
|
Nitrite Nitrogen
(NO2-N)
(mg/L)
|
0.043
(0.006 - 0.084)
|
Not available
|
|
Nitrate Nitrogen
(NO3-N)
(mg/L)
|
0.177
(0.073 - 0.393)
|
Not available
|
|
Total Inorganic
Nitrogen (TIN) (mg/L)
|
0.34
(0.23 - 0.53)
|
Not more than annual water column average of 0.4 mg/L
|
|
Total Kjeldahl Nitrogen (TKN) (mg/L)
|
0.60
(0.34 - 0.89)
|
Not available
|
|
Total Nitrogen (TN)
(mg/L)
|
0.75
(0.46 - 1.16)
|
Not available
|
|
Orthophosphate
Phosphorus (PO4-P) (mg/L)
|
0.016
(0.003 - 0.027)
|
Not available
|
|
Total Phosphorus (TP)
(mg/L)
|
0.09
(0.05 - 0.14)
|
Not available
|
|
Silica (as SiO2)
(mg/L)
|
1.05
(0.40 - 2.13)
|
Not available
|
|
Chlorophyll-a
(μg/L)
|
3.9
(0.8 - 13.3)
|
Not available
|
|
E. coli
(count/100mL)
|
230
(16 - 7800)
|
Secondary Contact Recreation Subzones and Fish Culture Subzone:
Not exceed 610 per 100mL as annual geometric mean
Recreation
Subzones: Not exceed 180 per 100mL, calculated as the geometric mean of all
samples collected from March to October inclusive in 1 calendar year
|
|
Faecal Coliforms
(count/100mL)
|
450
(31 - 17000)
|
Not available
|
Notes:
1.
Data
source: EPD Marine Water Quality in Hong Kong in 2021
2.
Except
as specified, data presented are depth-averaged values calculated by taking the
means of three depths: surface, mid-depth and 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.
5.
During
the periods of the special work arrangement under the COVID-19 pandemic in
2021, marine water quality monitoring frequency was adjusted and sampling at
representative monitoring stations were maintained.
Table 5.5 Summary of Marine Water
Quality Monitoring Data Collected by EPD in 2021 for VM12, VM14 and VT8
|
Parameters
|
Rambler Channel
|
Rambler Channel Typhoon Shelter
|
WQO for Victoria Harbour (Phase One) WCZ
(Marine Waters)
|
|
VM12
|
VM14
|
VT8
|
|
Temperature (°C)
|
24.8
(20.0 - 28.3)
|
24.5
(18.2 - 28.9)
|
25.9
(22.3 - 28.1)
|
Not more than 2℃ change in daily temperature range
|
|
Salinity
|
31.4
(28.8 - 33.4)
|
30.2
(25.2 - 33.3)
|
30.4
(28.0 - 33.0)
|
Not to cause more
than 10% change
|
|
Dissolved Oxygen
(mg/L)
|
Depth Average
|
4.7
(4.0 - 5.7)
|
4.9
(4.1 - 5.6)
|
4.6
(4.0 - 5.5)
|
Not less than 4
mg/L for 90% of the sampling occasions during the whole year
|
|
|
Bottom
|
4.5
(3.2 - 7.0)
|
4.8
(3.9 - 5.9)
|
3.8
(3.2 - 4.6)
|
Not less than 2
mg/L for 90% of the sampling occasions during the whole year
|
|
Dissolved Oxygen
(% Saturation)
|
Depth Average
|
67
(59 - 82)
|
70
(58 - 79)
|
67
(60 - 79)
|
Not available
|
|
|
Bottom
|
64
(48 - 92)
|
69
(56 - 76)
|
55
(48 - 66)
|
Not available
|
|
pH
|
7.5
(7.2 - 7.9)
|
7.6
(7.4 - 7.9)
|
7.5
(7.3 - 7.8)
|
pH falls within
6.5 - 8.5 (±0.2 from natural range)
|
|
Secchi Disc Depth
(m)
|
2.1
(1.8 - 2.8)
|
2.2
(1.7 - 3.0)
|
1.7
(1.5 - 1.9)
|
Not available
|
|
Turbidity
(NTU)
|
7.6
(4.2 - 16.5)
|
5.4
(2.8 - 10.0)
|
7.3
(4.2 - 9.7)
|
Not available
|
|
Suspended Solids (SS)
(mg/L)
|
6.3
(0.9 - 15.0)
|
6.1
(2.9 - 13.6)
|
4.9
(2.9 - 9.6)
|
Not more than 30%
increase
|
|
5-day Biochemical
Oxygen Demand (BOD5) (mg/L)
|
0.7
(0.2 - 1.5)
|
0.9
(<0.1 - 2.6)
|
0.5
(0.4 - 0.7)
|
Not available
|
|
Ammonia Nitrogen (NH3-N)
(mg/L)
|
0.170
(0.059 - 0.243)
|
0.126
(0.041 - 0.223)
|
0.170
(0.091 - 0.315)
|
Not available
|
|
Unionised Ammonia
(mg/L)
|
0.003
(<0.001 - 0.005)
|
0.002
(<0.001 - 0.004)
|
0.004
(<0.001 - 0.012)
|
Not more than
annual average of 0.021mg/L
|
|
Nitrite Nitrogen
(NO2-N)
(mg/L)
|
0.047
(0.006 - 0.127)
|
0.044
(0.007 - 0.084)
|
0.034
(0.005 - 0.049)
|
Not available
|
|
Nitrate Nitrogen
(NO3-N)
(mg/L)
|
0.180
(0.066 - 0.477)
|
0.212
(0.068 - 0.467)
|
0.216
(0.068 - 0.345)
|
Not available
|
|
Total Inorganic
Nitrogen (TIN) (mg/L)
|
0.40
(0.27 - 0.67)
|
0.38
(0.21 - 0.65)
|
0.42
(0.24 - 0.66)
|
Not more than annual water column average of 0.4 mg/L
|
|
Total Kjeldahl Nitrogen (TKN) (mg/L)
|
0.74
(0.36 - 1.12)
|
0.59
(0.40 - 0.76)
|
0.80
(0.69 - 0.92)
|
Not available
|
|
Total Nitrogen (TN)
(mg/L)
|
0.88
(0.54 - 1.23)
|
0.75
(0.52 - 0.96)
|
0.91
(0.76 - 1.05)
|
Not available
|
|
Orthophosphate
Phosphorus (PO4-P) (mg/L)
|
0.021
(0.013 - 0.030)
|
0.016
(0.004 - 0.027)
|
0.018
(0.010 - 0.030)
|
Not available
|
|
Total Phosphorus (TP)
(mg/L)
|
0.08
(0.04 - 0.15)
|
0.07
(0.04 - 0.08)
|
0.07
(0.04 - 0.09)
|
Not available
|
|
Silica (as SiO2)
(mg/L)
|
1.10
(0.45 - 2.17)
|
1.28
(0.22 - 2.80)
|
1.15
(0.72 - 1.70)
|
Not available
|
|
Chlorophyll-a
(μg/L)
|
2.7
(0.8 - 8.0)
|
7.8
(0.4 - 29.7)
|
2.5
(0.9 - 7.7)
|
Not available
|
|
E. coli
(count/100mL)
|
690
(100 - 6600)
|
200
(18 - 580)
|
510
(60 - 1300)
|
Not available
|
|
Faecal Coliforms
(count/100mL)
|
1500
(210 - 17000)
|
530
(52 - 2300)
|
1400
(130 - 3800)
|
Not available
|
Notes:
1.
Data
source: EPD Marine Water Quality in Hong Kong in 2021.
2.
Except
as specified, data presented are depth-averaged values calculated by taking the
means of three depths: surface, mid-depth and 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.
5.
During
the periods of the special work arrangement under the COVID-19 pandemic in
2021, marine water quality monitoring frequency was adjusted and sampling at
representative monitoring stations were maintained.
5.4.1.1
Water sensitive receivers (WSRs) within 500m
from the Project site boundary are identified with reference to Annex 14 of the
EIAO-TM.
5.4.1.2
Key marine WSRs within the 500m assessment area are
identified and their indicative locations are shown in Figure 5.1. These WSRs are listed in
Table 5.6
Table 5.6 List of Marine WSRs
|
ID
|
Description
|
Distance
from Project Site
|
|
WSD1
|
Flushing
Water Intake for Water Supplies Department Tsuen Wan Salt
Water Pumping Station
|
48m
|
|
C1
|
A Cooling
Water Intake in Tsuen Wan near to the ferry pier
|
139m
|
|
T1
|
Rambler
Channel Typhoon Shelter
|
24m
|
5.4.1.3
Key inland WSRs within the 500m assessment area are
also identified in Table 5.7
and their indicative locations are shown in Figure
5.1. These WSRs include:
Table 5.7 List of Inland WSRs
|
ID
|
Location
|
Description
|
Approx.
distance from Project Site
|
|
W1
|
East of Tsuen Tsing Interchange
|
Concrete channel near the East of Tsuen Tsing Interchange
|
Partially
lies within the Project site boundary
|
|
W2
|
Kwai Chung Park
|
Concrete channel across
the Kwai Chung Park and outside of Kwai Chung Park, sloping downward
|
Partially
lies within the Project site boundary
|
|
W3
|
Southwest of Tsuen Tsing Interchange
|
Concrete channel along Tsing Tsuen Road
|
0m
|
|
W4
|
West of Tsuen Tsing Interchange
|
Concrete channel near
the west of Tsuen Tsing Interchange
|
Partially
lies within the Project site boundary
|
|
W5
|
Wing Kei Road Trucks Car Park
|
Concrete channel surrounding
Wing Kei Road Trucks Car Park
|
16m
|
|
W6
|
Tsuen Wan Government Primary School,
Belvedere Garden
|
Concrete channel
along Tsuen Wan Government Primary School and Belvedere Garden
|
150m
|
|
W7
|
Belvedere Garden
|
Downhill
natural watercourse passing box culvert near Tuen
Mun Road then connect to modified watercourse close to Belvedere Garden
|
449m
|
|
W8
|
Pun Shan Tsuen
|
Concrete channel -
Tai Lam Chung Catchwater
|
406m
|
|
W9
|
Pun Shan Tsuen
|
Natural
watercourses from Shek Lung Kung towards Wang Fat Ching She
|
196m
|
|
W10
|
Pun Shan Tsuen
|
Natural
watercourse from Shek Lung Kung towards Belvedere Garden Phase 1
|
165m
|
|
W11
|
Chai Wan Kok
|
Semi-natural
watercourses near Chai Wan Kok, sloping downward to Sheeny Terrace
|
316m
|
|
WGG1
|
Water Gathering Ground near Pun Shan Tsuen
|
Water
Gathering Ground of Western Buffer WCZ
|
404m
|
5.4.1.4
The water gathering ground WGG1 is located at
404m away from the Project boundary, and also it is
located at a higher elevation than the Project works. Thus, the water source of the existing water
gathering ground is not expected to be affected during both construction and
operational phases of the Project. Some
watercourses including W2 (within Project site), W6 (150m), W7 (449m), W8 (406m),
W9 (196m), W10 (165m) and W11 (316m) are located at a higher elevation than the proposed
Project. They are expected not to be affected during both construction and
operational phases of the Project.
5.4.1.5
It should be noted that this Project would not
involve any alternation of the above identified watercourses, or any
construction works at/within the above identified watercourses.
5.5.1
Construction Impacts
5.5.1.1
The Project includes solely aboveground
development. General construction works (including
piling activities) for the Project would be land-based only. The potential
sources of water quality impact associated with the land-based works would
include:
·
Wastewater from general construction activities;
·
Construction site run-off;
·
Construction works in close proximity of inland watercourses;
·
Sewage effluent from construction workforce; and
·
Accidental spillage of chemicals.
Operation Impacts
5.5.1.2
Potential water quality impacts associated with
the operation phase would include:
·
Non-point source surface run-off from new impervious
areas.
5.6.1.1
The assessment area includes all areas within
500m from the Project Boundary. The WSRs that may be affected during the
construction and operation phases of the Project have been identified. Potential sources of water quality impact
that may arise during the construction and operation stages of the Project are
identified, including point discharges and non-point sources to surface water
runoff, sewage from workforce and polluted discharge generated from the
Project. All the identified sources of
potential water quality impact have been evaluated and their impact
significance determined. The mitigation measures
to reduce any identified adverse impacts on water quality to acceptable levels
for both construction and operation phases are determined.
5.7.1
Construction Phase
Wastewater from General Construction
Activities
5.7.1.1
Various types of construction activities may
generate wastewater. These include
general cleaning and polishing, wheel washing, dust suppression and utility
installation. These types of wastewater would contain high concentrations of SS. Various construction works may also generate
debris and rubbish such as packaging, construction materials and refuse. Uncontrolled discharge of site effluents,
rubbish and refuse generated from the construction works could lead to water
quality deterioration. It is expected
that if the good site practice suggested in Section 5.8.2 are followed as far as practicable, the potential
water quality impacts associated with construction activities would be minimal.
Construction Site Run-off
5.7.1.2
Potential pollution sources of site run-off may
include:
·
Run-off and erosion of exposed bare soil and
earth, drainage channels, earth working areas (including land-based piling
activities) and stockpiles;
·
Release
of any bentonite slurries, concrete washings and other grouting materials with
construction runoff or storm water;
·
Wash water from dust suppression sprays and
wheel washing facilities; and
·
Fuel, oil and
lubricants from maintenance of construction vehicles and equipment.
5.7.1.3
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 concentration 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.
5.7.1.4
Wind blown dust would
be generated from exposed soil surfaces in 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.
5.7.1.5
It is important that proper site practice and
good site management be followed to prevent run-off with high level of SS from
entering the surrounding waters. Best
Management Practices (BMPs) in controlling construction site discharges are
recommended for this Project. With the
implementation of BMPs 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. Suggested
measures to control construction site run-off and drainage are described in Section 5.8.2.
Construction Works in Close Proximity of
Inland Watercourses
5.7.1.6
Construction activities in close
proximity of inland watercourses may pollute the inland water bodies due
to potential release of construction wastes as well as construction wastewater and the
site runoff which are generally characterised
by high concentration of SS and elevated pH. Adoption of good housekeeping and mitigation
measures would reduce the generation of construction wastes and potential water
pollution. The implementation of
measures to control run-off and drainage water will be important for the
construction works adjacent to the inland watercourse in
order to prevent run-off and drainage water with high levels of SS from
entering the water environment. With the
implementation of BMPs and provision of mitigation measures as specified in ProPECC PN 1/94 "Construction Site Drainage"
and ETWB TC (Works) No. 5/2005 "Protection of natural streams / rivers
from adverse impacts arising from construction works" as detailed in Section
5.8.2, it is anticipated that water quality impacts would be minimal.
Sewage Effluent from Construction Workforce
5.7.1.7
During the construction of the Project, the
workforce on site will generate sewage effluent, which is characterized by high
levels of BOD, ammonia and E. coli counts. According to Section 5.6.10 of the
Construction Industry Council (CIC)'s publication "Reference Materials on
Construction Site Welfare, Health and Safety Measures", the number of
toilet facilities should be provided at a ratio of not less than one for every
25 workers. Potential water quality
impacts upon the local drainage and fresh water system
may arise from these sewage effluents, if uncontrolled.
5.7.1.8
Temporary sewage generation can be adequately handled
by temporary sanitary facilities, such as portable chemical toilets. The number of the chemical toilets required
for the construction sites should be subject to the detailed design, the
capacity of the chemical toilets, and contractor's site practices. A licensed contractor should be employed to
provide appropriate and adequate portable toilets and be responsible for
appropriate disposal and maintenance.
5.7.1.9
Provided that sewage is not discharged directly
into storm drains or inland waters adjacent to the construction site, temporary
sanitary facilities are used and properly maintained, and mitigation measures
as recommended in Section 5.8.2 are adopted as far as practicable, it is
unlikely that sewage generated from the site would have a significant water
quality impact.
Accidental Spillage of Chemicals
5.7.1.10
The use of engine oil and lubricants and their
storage as waste materials have the potential to create impacts on the water
quality if spillage occurs. Waste oil
may infiltrate into the surface soil layer, or runoff into adjacent
waterbodies, increasing hydrocarbon levels.
Groundwater pollution may also be arisen from the improper use and
storage of chemical and petroleum products within the site area where
groundwater infiltrates into the area.
Infiltration of groundwater may occur at areas where there are faults
and/or fissures in the rock mass. The
potential impacts could however be mitigated by practical mitigation measures
and good site practices as described in Section 5.8.2.
5.7.2
Operation Phase
Non-point source surface run-off from new impervious
areas
5.7.2.1
Surface runoff to be generated from the Project
is known as non-point source pollution.
The new paved road/bridge will increase the quantity of surface
runoff. The presence of oil, grease and
grit on their surfaces could be washed into the nearby drainage system or even
into the watercourses during rainfall event.
5.7.2.2
The Project is expected to have an additional
2.39 ha paved area when in operation and the surface runoff collected from the
newly paved areas from proposed locations for widening of Tsuen Wan Road and
new slip roads would be conveyed to the existing public drainage system. According to the DSD “Stormwater Drainage
Manual (5th edition)”, annual rainfall in Hong Kong is around 2,400mm. The EPD study namely "Update on
Cumulative Water Quality and Hydrological Effect of Coastal Developments and
Upgrading of Assessment Tool (Update Study)” suggested that only rainfall
events of sufficient intensity and volume would give rise to runoff and that
runoff percentage is about 44% and 82% for dry and wet season,
respectively. Therefore, only 1,512mm of
2,400mm annual rainfall would be considered as effective rainfall that would
generate runoff (i.e. 1,512mm=2,400mm×(82%+44%)/2). With consideration of the new paved area and
a runoff coefficient of 0.9 for paved surface, the overall daily runoff
generated from the Project was estimated to be about 89.1 m3/day (i.e.1512/1000/365*23900*0.9).
5.7.2.3
To minimise the impact
from road runoff, all the road works planned under the Project should be
designed with adequate drainage system and appropriate oil interceptors, as
required. It is anticipated that with
proper implementation of best management practices as recommended in Section
5.8.3,
no adverse water quality impact from non-point source surface run-off is
expected.
5.8.2.1
Measures as listed below are recommended to mitigate
the potential water quality impacts from the land-based construction works.
General Construction Activities and
Construction Site Run-off
5.8.2.2
Control of potential pollution of nearby water
bodies during the construction phase of the Project should be achieved by
measures to:
·
prevent or minimise the
likelihood of pollutants (generated from construction activities) being in
contact with rainfall or run-off; and
·
abate pollutants in the
stormwater surface run-off prior to the discharge of surface run-off to the
nearby water bodies.
5.8.2.3
These principle
objectives should be achieved by implementation of the Best Management
Practices (BMPs) of mitigation measures in controlling water pollution. The guidelines for handling and disposal of
construction site discharges as detailed in the ProPECC
PN 1/94 "Construction Site Drainage" should be followed, where
applicable. All effluent discharged from
the construction site should comply with the standards stipulated in the TM-DSS. Minimum distances of 100m should be maintained
between the discharge points of construction site effluent and the existing
seawater intakes, and no effluent shall be discharged into the typhoon
shelter. The following measures
are recommended to protect water quality 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.
Construction Runoff
5.8.2.4
Surface runoff 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 during construction works to
properly direct stormwater to such silt removal facilities. Perimeter channels should be provided on site
boundaries where necessary to intercept storm runoff 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.
5.8.2.5
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.
5.8.2.6
Construction works should be programmed to
minimize soil excavation works in rainy seasons (April to September). If soil excavation 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
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.
5.8.2.7
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.
5.8.2.8
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.
5.8.2.9
Open stockpiles of construction materials (e.g. aggregates, sand and fill material) on sites 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.
5.8.2.10
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 runoff from getting into foul
sewers. Discharge of surface runoff into
foul sewers must always be prevented in order not to unduly overload the foul
sewerage system.
5.8.2.11
If bentonite slurries are required for any
construction works, they should be reconditioned and reused wherever
practicable to minimise the disposal volume of used
bentonite slurries. Temporary enclosed
storage locations should be provided on-site for any unused bentonite that
needs to be transported away after the related construction activities are
completed. Requirements as stipulated in
ProPECC Note PN 1/94 should be closely followed when
handling and disposing bentonite slurries.
Boring and Drilling Water
Wheel Washing Water
5.8.2.13
All vehicles and plants should be cleaned before
they leave a construction site to minimise the
deposition of earth, mud and debris on roads. A wheel washing bay should be provided at
every site exit if practicable and washwater 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 backfill to
reduce vehicle tracking of soil and to prevent site run-off from entering
public road drains.
Rubbish and Litter
5.8.2.14
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.
Effluent Discharge
5.8.2.15
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 runoff and wastewater generated from
the works areas should be treated so that it satisfies all the standards listed
in the TM-DSS. 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.
Construction Works in Close Proximity of
Inland Water
5.8.2.16
The practices outlined in ETWB TC (Works) No. 5/2005
Protection of natural streams / rivers from adverse impacts arising from
construction works should also be adopted where applicable to minimise the water quality impacts on any natural streams
or surface water systems. Relevant
mitigation measures from the ETWB TC (Works) No. 5/2005 are listed below:
·
Construction works close to the inland waters
should be carried out in the dry season as far as practicable where the flow in
the surface channel or stream is low.
·
The use of less or smaller construction plants
may be specified in areas close to the watercourses to reduce the disturbance
to the surface water.
·
Temporary storage of materials (e.g. equipment, chemicals and fuel) and temporary stockpile
of construction materials should be located well away from any water courses
when carrying out of the construction works.
·
Stockpiling of construction materials and dusty
materials should be covered and located away from any water courses.
·
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.
·
Proper shoring may need to be erected in order to prevent soil or mud from slipping into the
watercourses.
Sewage Effluent from Construction Workforce
5.8.2.17
The construction workforce on site will generate
sewage. Sufficient chemical toilets should
be provided in the works area, with a licensed waste collector employed to
clean the chemical toilets on a regular basis.
5.8.2.18
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.
Accidental Spillage of Chemicals
5.8.2.19
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.
5.8.2.20
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 leakage and
spillage should only be undertaken within the areas appropriately equipped to
control these discharges.
5.8.2.21
Disposal of chemical wastes should be carried
out in compliance 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.
Non-point source surface run-off from new
impervious areas
5.8.3.1
The ProPECC PN 5/93 “Drainage
Plans subject to Comments by Environmental Protection Department” provides
guidelines and practices for handling, treatment and
disposal of various effluent discharges to stormwater drains and foul
sewers. The design of site drainage
should follow the relevant guidelines and practices as given in the ProPECC PN 5/93. Best
Management Practices (BMPs) for storm water discharge are recommended to reduce
the stormwater pollution arising from the Project.
Design Measures
5.8.3.2
Exposed surface shall be avoided within the
proposed development to minimise soil erosion. Development site shall be either hard paved or
covered by landscaping area where appropriate to reduce soil erosion.
5.8.3.3
The existing watercourses adjacent to the
Project site will be retained to maintain the original flow path. The drainage system will be designed to avoid
flooding based on the 1 in 50 year return period in
accordance with “Stormwater Drainage Manual (5th Edition)”
published by DSD.
Devices / Facilities to Control Pollution
5.8.3.4
Screening facilities such as standard gully
grating and trash grille, with spacing which is capable of screening off large
substances such as fallen leaves and rubbish should be provided at the inlet of
drainage system.
5.8.3.5
Road gullies with standard design and silt traps
and oil interceptors should be incorporated during the detailed design to
remove particles present in storm water runoff.
Administrative Measures
5.8.3.6
Good management measures such as regular
cleaning and sweeping of road surface / open areas is suggested. The road surface / open area cleaning should
also be carried out prior to occurrence of rainstorm.
5.8.3.7
Manholes, as well as storm water gullies,
ditches provided among the development areas should be regularly inspected and
cleaned (e.g. monthly). Additional inspection and
cleansing should be carried out before forecast heavy
rainfall.
5.9.1.1
According to Section 2.8, concurrent
projects in the vicinity of the Project site are identified and relevant
cumulative impact assessment for construction phase and operation phase of the
Project in conjunction with these concurrent projects is summarized below.
Construction Phase
5.9.1.2
The Proposed Columbarium Building at Site No.10
Tsing Tsuen Road would be constructed concurrently with the Project. Based on the project design, sources of water
quality impacts include general construction activities, construction runoff
and sewage from construction workforce. With
proper mitigation measures put in place, no adverse water quality impacts are expected.
5.9.1.3
The Tai Chung Road Interchange is anticipated to
commence construction in 2028 for completion in 2030. The potential water
quality impacts from this land-based construction would include wastewater from
general construction activities, construction runoff, accidental spillage of
chemical and sewage from construction workforce. With proper mitigation
measures put in place, no adverse water quality impacts are expected.
5.9.1.4
As no adverse water quality impact is expected
from the Project and the above concurrent projects during the construction
phase, no adverse cumulative water quality impact is therefore anticipated
during the construction phase.
Operation Phase
5.9.1.5
Flyover from Kwai Tsing Interchange Upramp to Kwai Chung Road (Register No.: AEIAR-190/2015)
would operate concurrently with the Project. According to its EIA report
(AEIAR-190/2015), the potential sources of water quality impact during the
operation phase were identified to be stormwater runoff. With adoption of best
Management Practices (BMPs) and other measures suggested in ProPECC
PN 5/93 “Drainage Plans subject to Comments by Environmental Protection
Department”, adverse water quality impact is not anticipated.
5.9.1.6
Improvement Works at Tsuen Tsing Interchange (IWTTI)
is a modification to the Completion of Texaco Road / Tsuen Wan Bypass
Interchange and Improvements to Texaco Road Phase II (TDD Contract No.:
TW74/90), which was completed in 1995. For the operation of IWTTI, major source
of water quality impact is expected to be surface runoff. No unacceptable water quality impact is
expected if the proper mitigation measures are implemented.
5.9.1.7
Tai Chung Road Interchange would concurrently
operate with the Project. The potential water quality impact from the Tai Chung
Road Interchange is expected to be surface runoff. No unacceptable water
quality impact is expected if the proper mitigation measures are implemented.
5.9.1.8
As neither the Project nor the concurrent
projects were anticipated to generate significant water quality impact during
operation phase, adverse cumulative impact is hence not anticipated.
5.10.1.1
With proper implementation of mitigation
measures, no residual water quality impact is expected during construction and
operation phases.
5.11.1.1
No adverse water quality impacts would be
expected from the road works if the recommended mitigation measures are
implemented properly. No water quality
monitoring is therefore considered necessary.
Nonetheless, regular site inspection during the construction phase is
proposed to inspect the construction activities and works area to ensure the
recommended mitigation measures are properly implemented.
5.12
Conclusion
5.12.1
Construction Phase
5.12.1.1
The key potential sources of water quality
impacts during construction phase include the wastewater from general
construction activities, construction site run-off, construction works in close proximity of inland watercourses, accidental spillage
of chemicals and sewage effluent from construction workforce. The potential water quality impacts could be
mitigated and controlled by implementing the recommended mitigation measures. Regular site inspections should be undertaken
routinely to inspect the construction activities and works area to ensure the
recommended mitigation measures are proper implemented.
5.12.2
Operation Phase
5.12.2.1
The key potential sources of water quality
impacts during operation phase would be related to non-point source stormwater
runoff from the new paved areas.
Provided that the recommended mitigation measures for the drainage
system are properly implemented, the associated water quality impacts are
expected to be minimal and acceptable.