5.1.1
This section presents an assessment of the potential water quality
impacts associated with the construction and operation of the Project.
Recommendations for mitigation measures have been provided, where necessary, to
minimize the identified water quality impacts to an acceptable level. The
water quality impact assessment was conducted in accordance with the
requirements in Annexes 6 and 14 of the EIAO-TM and the requirements in Section
3.4.6 and Appendix D of the EIA Study Brief (ESB-323/2019).
Environmental Impact
Assessment Ordinance (EIAO)
5.2.1
The 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
·
Annex 14 - Guidelines for Assessment of Water Pollution
Water Quality Objectives
5.2.2
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) and four Supplementary
Water Control Zones. 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. According
to Item 3.4.6.2 of the Study Brief, the assessment areas for this water quality
impact assessment covers the Tolo Harbour and Channel WCZ as well as the
Victoria Harbour (Phase Two) WCZ as designated under the WPCO. The selected
WQOs for the Tolo Harbour and Channel WCZ, Tolo Harbour Supplementary WCZ and
Victoria Harbour (Phase Two) WCZ are listed in Table
5.1 to Table 5.3 respectively.
Table 5.1 Summary
of Key Water Quality Objectives for Tolo Harbour and Channel WCZ
|
Parameters
|
Objectives
|
Subzone
|
|
Offensive odour, tints
|
Not to be present
|
Whole zone
|
|
Visible foam, oil
scum, litter
|
Not to be present
|
Whole zone
|
|
Dissolved Oxygen (DO)
|
Not less than 2 mg/L within two metres of the bottom, or
not less than 4 mg/L in the remainder of the water column
|
Marine waters in
Harbour Subzone
|
|
Not less than 3 mg/L within two metres of the bottom, or
not less than 4 mg/L in the remainder of the water column
|
Marine waters in
Buffer Subzone
|
|
Not less than 4 mg/L at any point in the water column
|
Marine waters in
Channel Subzone
|
|
Not less than 4 mg/L or 40% saturation (at 15℃) at any
time
|
Inland waters
|
|
pH
|
Not to cause the normal pH range to be extended by more
than ±0.5 pH units at any time
|
Marine waters in
Harbour Subzone
|
|
Not to cause the normal pH range to be extended by more
than ±0.3 pH units at any time
|
Marine waters in
Buffer Subzone
|
|
Not to cause the normal pH range to be extended by more
than ±0.1 pH units at any time
|
Marine waters in
Channel Subzone
|
|
Not to exceed the normal pH range of 6.5 - 8.5 at any
time
|
Inland Waters in Shing
Mun (A, B, C, F, G, H) subzones
|
|
Not to exceed the normal pH range of 6.0 - 9.0 at any
time
|
Inland Waters in Shing
Mun (D, E, I) subzones and other watercourses
|
|
Light Penetration
|
Should not reduce light transmission by more than 20% of
the normal level at any location or any time.
|
Marine waters in
Harbour Subzone
|
|
Should not reduce light transmission by more than 15% of
the normal level at any location or any time.
|
Marine waters in
Buffer Subzone
|
|
Should not reduce light transmission by more than 10% of
the normal level at any location or any time.
|
Marine waters in
Channel Subzone
|
|
Salinity
|
Not to cause the normal salinity range to be extended by
more than ±3 parts per thousand at any time
|
Marine waters
|
|
Temperature
|
Not to cause the
natural daily temperature range to be extended by greater than ±1.0 ℃ at any
location or time. The rate of temperature change shall not exceed 0.5 ℃ per hour
at any location, unless due to natural phenomena.
|
Marine
waters
|
|
Not to cause the natural daily temperature range to be
extended by greater than ±2.0 ℃ at any location or time.
|
Inland waters
|
|
Chemical oxygen demand
(COD)
|
Not to exceed 15 mg/L at any time
|
Inland Waters in Shing
Mun (B, F, G) subzones
|
|
Not to exceed 30 mg/L at any time
|
Inland Waters in Shing
Mun (A, C, D, E, H, I) subzones and other watercourses
|
|
5-day Biochemical
Oxygen Demand (BOD5)
|
Not to exceed 3 mg/L at any time
|
Inland Waters in Shing
Mun (B, F, G) subzones
|
|
Not to exceed 5 mg/L at any time
|
Inland Waters in Shing
Mun (A, C, D, E, H, I) subzones and other watercourses
|
|
Suspended Solids (SS)
|
Not to cause the annual median level to exceed 20 mg/L
|
Inland Waters in Shing
Mun (A, B, C, F, G, H) subzones
|
|
Not to cause the annual median level to exceed 25 mg/L
|
Inland Waters in Shing
Mun (D, E, I) subzones and other watercourses
|
|
Colour
|
Human activity should not cause the colour of water to exceed
50 Hazen units.
|
Inland waters in
SM(A), SM(C), SM(D), SM(E), SM(H), SM(I) and other inland watercourses
|
|
Human activity should not cause the colour of water to
exceed 30 Hazen units.
|
Inland waters in
SM(B), SM(F) and SM(G)
|
|
Settleable Material
|
Bottom deposits or submerged objects should not adversely
influence bottom-living communities, alter the basic Harbour geometry or
shipping channels, present any hazard to shipping or diving activities, or
affect any other beneficial use of the waters
|
Marine waters
|
|
Ammonia Nitrogen (NH3-N)
|
Not to exceed 0.5 mg/L at any time
|
Inland waters
|
|
E. coli Bacteria
|
Not to exceed 610 per 100mL, calculated as the geometric
mean of all samples collected in one calendar year
|
Secondary Contact Recreation
Subzone and Fish Culture subzones
|
|
Not to exceed 1,000 per 100mL, calculated as a running
median of the most recent 5 consecutive samples taken at intervals of between
7 and 21 days (or 14 and 42 days)
|
Inland Waters in Shing
Mun (A, C, D, E, H, I) subzones and other watercourses
|
|
Not to exceed 0 per 100mL, calculated as a running median
of the most recent 5 consecutive samples taken at intervals of between 7 and
21 days (or 14 and 42 days)
|
Inland Waters in Shing
Mun (B, F, G) subzones
|
|
Chlorophyll-a
|
Not to cause the level of chlorophyll-a in waters
of the subzone to exceed 20 mg/m3, calculated as a running
arithmetic mean of 5 daily measurements for any single location and depth
|
Marine waters in
Harbour Subzone
|
|
Not to cause the level of chlorophyll-a in waters
of the subzone to exceed 10 mg/m3, calculated as a running
arithmetic mean of 5 daily measurements for any single location and depth
|
Marine waters in
Buffer Subzone
|
|
Not to cause the level of chlorophyll-a in waters
of the subzone to exceed 6 mg/m3, calculated as a running
arithmetic mean of 5 daily measurements for any single location and depth
|
Marine waters in
Channel Subzone
|
|
Toxic Substances
|
Toxic substances in the water should not 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 interactions
of toxic substances with each other
|
Whole zone
|
|
Human activity should not cause a risk to any beneficial
use of the aquatic environment
|
Whole zone
|
Source: Tolo
Harbour and Channel Water Control Zone Statement of Water Quality Objectives.
Note: The WQOs for inland
waters are only reported for Shing Mun River catchment, which is within the
Study Area of this Project. There are 9 subzones of inland waters in Shing Mun
River catchment, namely SM(A) to SM(I) respectively, as delineated under
Schedule 3 of Cap 358F Tolo Harbour and Channel Water Control Statement of
Water Quality Objectives for Watercourses under the WPCO. Please refer to http://www.legislation.gov.hk/blis_pdf.nsf/CurAllEngDoc/D436F5EC4700FCAD482575EE007087E9/$FILE/CAP_358F_e_b5.pdf
for the delineation of Shing Mun River Subzone
Table 5.2 Summary
of Key Water Quality Objectives for Tolo Harbour Supplementary WCZ
|
Parameters
|
Objectives
|
Subzone
|
|
Offensive odour, tints
|
Not to be present
|
Whole zone
|
|
Visible foam, oil
scum, litter
|
Not to be present
|
Whole zone
|
|
E. coli Bacteria
|
Not to exceed 1 per 100mL, calculated as the geometric
mean of the most recent 5 consecutive samples taken at intervals of between 7
and 21 days
|
Whole zone
|
|
Colour
|
Not to exceed 30 Hazen units at any time
|
Whole zone
|
|
Dissolved Oxygen (DO)
|
Not less than 4 mg/L at any time
|
Whole zone
|
|
pH
|
Not to exceed the normal pH range of 6.5 - 8.5 at any
time
|
Whole zone
|
|
Temperature
|
Change due to human activity not to exceed 2℃
|
Whole zone
|
|
Salinity
|
Change due to human activity not to exceed 10% of natural
ambient salinity level.
|
Whole zone
|
|
Suspended Solids (SS)
|
Change due to human activity not to cause the annual
median level to exceed 20 mg/L
|
Whole zone
|
|
Unionized 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
|
|
5-day Biochemical
Oxygen Demand (BOD5)
|
Not to exceed 3 mg/L at any time
|
Whole zone
|
|
Chemical Oxygen Demand
(COD)
|
Not to exceed 15 mg/L at any time
|
Whole zone
|
|
Toxic Substances
|
Toxic substances in the water should not 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 interactions
of toxic substances with each other
|
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
(Tolo Harbour Supplementary Water Control Zone).
Table 5.3 Summary
of Key Water Quality Objectives for Victoria Harbour (Phase Two) WCZ
|
Parameters
|
Objectives
|
Subzone
|
|
Offensive odour, tints
|
Not to be present
|
Whole zone
|
|
Visible foam, oil
scum, litter
|
Not to be present
|
Whole zone
|
|
E. coli Bacteria
|
Not to exceed 1,000 per 100mL, calculated as the
geometric mean of the most recent 5 consecutive samples taken at intervals of
between 7 and 21 days
|
Inland waters
|
|
Colour
|
Not to exceed 50 Hazen units at any time
|
Inland waters
|
|
Dissolved Oxygen (DO)
within 2 m of the seabed
|
Not less than 2 mg/L for 90% of the sampling occasions
during the whole year
|
Marine waters
|
|
Depth-averaged DO
|
Not less than 4 mg/L for 90% of the sampling occasions
during the whole year
|
Marine waters
|
|
Not less than 4 mg/L at any time
|
Inland waters
|
|
pH
|
To 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 units
|
Marine waters
|
|
Not to exceed the normal pH range of 6.0 - 9.0 at any
time
|
Inland waters
|
|
Salinity
|
Change due to human activity not to exceed 10% of ambient
salinity level.
|
Whole zone
|
|
Temperature
|
Change due to human activity not to exceed 2℃
|
Whole zone
|
|
Suspended Solids (SS)
|
Not to raise the ambient level by more than 30% caused by
human activity nor give rise to accumulation of SS which may adversely affect
aquatic communities
|
Marine waters
|
|
Not to cause the annual median level to exceed 25 mg/L
|
Inland waters
|
|
Unionized 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
|
Shall not cause excessive or nuisance growth of algae or
other aquatic plants
|
Marine waters
|
|
Total Inorganic
Nitrogen (TIN)
|
Not to exceed 0.4 mg/L, calculated as annual water column
average
|
Marine waters
|
|
5-day Biochemical
Oxygen Demand (BOD5)
|
Not to exceed 5 mg/L at any time
|
Inland waters
|
|
Chemical Oxygen Demand
(COD)
|
Not to exceed 30 mg/L at any time
|
Inland waters
|
|
Toxic Substances
|
Toxic substances in the water should not 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 interactions
of toxic substances with each other
|
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 (Phase Two) Water Control Zone).
Hong Kong Planning
Standards and Guidelines
5.2.3
The Hong Kong Planning Standards and Guidelines (HKPSG), Chapter 9
(Environment), provides additional guidelines against water pollution for
sensitive uses such as aquaculture and fisheries zones, bathing waters and
other contact recreational waters.
Technical Memorandum on
Effluent Discharge Standard (TM-DSS)
5.2.4
Discharge of effluents is 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 standards control
the physical, chemical and microbial quality of effluents. Any effluent
discharge from the proposed construction and operation activities must comply
with the relevant standards as stipulated in the TM-DSS.
5.2.5
The criteria for discharges to inland waters depend upon the beneficial
uses of the waters. The majority of the inland water bodies potentially
affected by the proposed developments are used for general amenity and
secondary contact recreation, which are classified as Group D inland waters.
The standards for effluents discharged into Group D inland waters are provided
in Table 5.4 below.
Table 5.4 Standards
for effluents discharged into Group D inland waters (All units in mg/L unless
otherwise stated; all figures are upper limits unless otherwise indicated)
|
Flow rate
(m3/day)
|
≦200
|
＞200
and
|
＞400
and
|
＞600
and
|
＞800
and
|
＞1000
and
|
＞1500
and
|
＞2000
and
|
|
Determinand
|
|
≦400
|
≦600
|
≦800
|
≦1000
|
≦1500
|
≦2000
|
≦3000
|
|
pH (pH units)
|
6-10
|
6-10
|
6-10
|
6-10
|
6-10
|
6-10
|
6-10
|
6-10
|
|
Temperature (℃)
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
|
Colour (lovibond
units)(25mm cell length)
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
Suspended solids
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
|
BOD
|
20
|
20
|
20
|
20
|
20
|
20
|
20
|
20
|
|
COD
|
80
|
80
|
80
|
80
|
80
|
80
|
80
|
80
|
|
Oil & Grease
|
10
|
10
|
10
|
10
|
10
|
10
|
10
|
10
|
|
Iron
|
10
|
8
|
7
|
5
|
4
|
2.7
|
2
|
1.3
|
|
Boron
|
5
|
4
|
3.5
|
2.5
|
2
|
1.5
|
1
|
0.7
|
|
Barium
|
5
|
4
|
3.5
|
2.5
|
2
|
1.5
|
1
|
0.7
|
|
Mercury
|
0.1
|
0.05
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Cadmium
|
0.1
|
0.05
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Other toxic metal
individually
|
1
|
1
|
0.8
|
0.8
|
0.5
|
0.5
|
0.2
|
0.2
|
|
Total Toxic metals
|
2
|
2
|
1.6
|
1.6
|
1
|
1
|
0.5
|
0.4
|
|
Cyanide
|
0.4
|
0.4
|
0.3
|
0.3
|
0.2
|
0.1
|
0.1
|
0.05
|
|
Phenols
|
0.4
|
0.3
|
0.2
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
|
Sulphide
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
Sulphate
|
800
|
600
|
600
|
600
|
600
|
400
|
400
|
400
|
|
Chloride
|
1000
|
800
|
800
|
800
|
600
|
600
|
400
|
400
|
|
Fluoride
|
10
|
8
|
8
|
8
|
5
|
5
|
3
|
3
|
|
Total phosphorus
|
10
|
10
|
10
|
8
|
8
|
8
|
5
|
5
|
|
Ammonia nitrogen
|
20
|
20
|
20
|
20
|
20
|
20
|
20
|
10
|
|
Nitrate + nitrite
nitrogen
|
50
|
50
|
50
|
30
|
30
|
30
|
30
|
20
|
|
Surfactants (total)
|
15
|
15
|
15
|
15
|
15
|
15
|
15
|
15
|
|
E. coli
(count/100ml)
|
1000
|
1000
|
1000
|
1000
|
1000
|
1000
|
1000
|
1000
|
Source from Table 6 of TM-DSS, EPD
Professional Persons
Environmental Consultative Committee Practice Notes (ProPECC PNs)
5.2.6
The Environmental Protection Department (EPD) has issued the
Professional Persons Environmental Consultative Committee Practice Note on
Construction Site Drainage (ProPECC PN 1/94) to provide guidelines for handling
and disposal of construction site discharges. Practices outlined in ProPECC PN
1/94 shall be closely followed to control site runoff and wastewater generated
during the construction phase of the proposed Project so as to minimize
potential water quality impacts associated with construction site discharges.
5.2.7
The ProPECC PN 5/93 on Drainage Plans Subject to Comment by the EPD
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.
ETWB Technical Circular
(Works) No. 5/2005 Protection of Natural Streams/Rivers from Adverse Impacts Arising from
Construction Works
5.2.8
ETWB Technical Circular (Works) 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 (Works)
No. 5/2005 should be followed as far as possible to protect the inland
watercourse at or near the Project area during the construction phase.
Guidelines for the
Design of Small Sewage Treatment Plants
5.2.9
The “Guidelines for the Design of Small Sewage Treatment Plants”
have been prepared with a view to providing Authorized Persons and designers
with general advice on the design of small sewage treatment plants (STP). The
guidelines highlight the importance of good plant design, which among other
objectives, should aim to make future operation easy and reliable.
Study Area
5.3.1
According to Section 3.4.6.2 of the Study Brief, the study area for this
water quality impact assessment included areas within 500m from the boundary of
the Project and covered the Tolo Harbour and Channel WCZ and Victoria Harbour
(Phase Two) WCZ as designated under the WPCO.
5.3.2
The baseline conditions of the water bodies in the study area were
established with reference to the routine river and marine water quality
monitoring data collected by EPD, their corresponding monitoring locations are
indicated in 60604728/R42b/Figure 5.1. Descriptions of the baseline
conditions provided in the subsequent sections are extracted from the EPD’s
reports “River Water Quality in Hong Kong in 2020” and “Marine Water
Quality in Hong Kong in 2020”.
Marine Water
Water Quality in
Victoria Harbour
5.3.3
The marine water quality monitoring results at stations in vicinity of
the Project, namely VM4 and VM5 are shown in Table
5.5 below. Full compliances with the WQO was recorded at the two selected
EPD stations for TIN, DO (depth average and bottom) and UIA in 2020.
Table 5.5 Baseline
Water Quality Condition for Victoria Harbour WCZ in 2020
|
Parameters
|
Victoria
Harbour (Central)
|
WPCO
WQO
(in
marine waters)
|
|
VM4
|
VM5
|
|
Temperature
(℃)
|
24.5
(19.6 - 28.9)
|
24.2
(19.0 - 29.0)
|
Change due to waste discharge not to exceed 2℃
|
|
Salinity
|
31.4
(28.7 - 33.1)
|
30.9
(27.4 - 33.1)
|
Change due to waste discharge not to exceed 10% of
natural ambient level
|
|
Dissolved Oxygen (DO)
(mg/L)
|
Depth Average
|
5.7
(4.4
- 6.9)
|
5.6
(4.5
- 6.6)
|
Not less than 4 mg/L for 90% of the samples
|
|
|
Bottom
|
5.6
(4.0
- 6.9)
|
5.4
(3.4
- 6.8)
|
Not less than 2 mg/L for 90% of the samples
|
|
Dissolved Oxygen
(% Saturation)
|
Depth Average
|
81
(64 - 92)
|
79
(65 - 92)
|
Not available
|
|
|
Bottom
|
78
(40 - 96)
|
74
(30 - 95)
|
Not available
|
|
pH
|
7.9
(7.5
- 8.1)
|
7.9
(7.6
- 8.1)
|
6.5 - 8.5 (± 0.2 from natural range)
|
|
Secchi Disc Depth
(m)
|
2.4
(2.0
- 3.1)
|
2.5
(1.8
- 3.0)
|
Not available
|
|
Turbidity
(NTU)
|
3.4
(1.2
- 6.4)
|
3.2
(1.7 - 4.8)
|
Not available
|
|
Suspended Solids (SS)
(mg/L)
|
7.1
(1.6
- 14.3)
|
7.7
(2.2 -
13.9)
|
Not more than 30% increase
|
|
5-day Biochemical Oxygen Demand
(BOD5) (mg/L)
|
0.8
(0.3 - 1.6)
|
0.8
(0.3
- 2.0)
|
Not available
|
|
Ammonia Nitrogen
(mg/L)
|
0.112
(0.033
- 0.207)
|
0.138
(0.050
- 0.203)
|
Not available
|
|
Unionized Ammonia (UIA)
(mg/L)
|
0.004
(<0.001
- 0.007)
|
0.005
(0.001 -
0.009)
|
Not more than 0.021 mg/L for annual mean
|
|
Nitrite Nitrogen
(mg/L)
|
0.028
(0.007
- 0.070)
|
0.027
(0.009
- 0.090)
|
Not available
|
|
Nitrate Nitrogen
(mg/L)
|
0.149
(0.051
- 0.287)
|
0.161
(0.059 -
0.377)
|
Not available
|
|
Total Inorganic Nitrogen (TIN)
(mg/L)
|
0.29
(0.15
- 0.45)
|
0.33
(0.18
- 0.61)
|
Not more than 0.4 mg/L for annual mean
|
|
Total Kjeldahl Nitrogen
(mg/L)
|
0.62
(0.35
- 1.07)
|
0.63
(0.21
- 1.20)
|
Not available
|
|
Total Nitrogen
(mg/L)
|
0.80
(0.55
- 1.19)
|
0.82
(0.49
- 1.34)
|
Not available
|
|
Orthophosphate Phosphorus
(PO4-P) (mg/L)
|
0.019
(0.011 -
0.032)
|
0.018
(0.006 -
0.033)
|
Not available
|
|
Total Phosphorus
(mg/L)
|
0.06
(0.03 -
0.08)
|
0.05
(0.03 -
0.08)
|
Not available
|
|
Silica (as SiO2)
(mg/L)
|
1.01
(0.33 -
1.77)
|
0.99
(0.32 -
2.10)
|
Not available
|
|
Chlorophyll-a
(µg/L)
|
3.1
(0.4 -
12.1)
|
3.0
(0.2 -
15.3)
|
Not available
|
|
E. coli
(cfu/100mL)
|
290
(27 -
1200)
|
490
(79 -
5500)
|
Not available
|
|
Faecal Coliforms
(cfu/100mL)
|
740
(89 -
4100)
|
1200
(190 -
8800)
|
Not available
|
Note: 1. Data
source: EPD Marine Water Quality in Hong Kong in 2020
2. Unless
otherwise specified, data presented are depth-averaged values calculated by
taking the means of three depths: Surface, Mid-depth, Bottom.
3. Data
presented are annual arithmetic means of depth-averaged results except for E.
coli and faecal coliforms that are annual geometric means.
4. Data
in brackets indicate the ranges.
5. cfu – colony forming
unit.
Trend of Water Quality
in Victoria Harbour
5.3.4
The overall WQO compliance rate of Victoria Harbour WCZ in 2020 was 90%.
The WQO compliance rate for DO and UIA in 2020 were both 100%. Under the
influence of regional background level in the Pearl River Estuary as well as
local pollution sources, only 70% of the monitoring stations in the WCZ met the
TIN WQO.
5.3.5
The TIN compliance rate fluctuates year to year under the influence of
regional TIN level in the entire Pearl River Estuary, local urban surface
run-offs and Stonecutters Island Sewage Treatment Works (SCISTW) discharges. The
regional influence was also observed in the monitoring data for North Western,
Southern and Western Buffer WCZs. On the other hand, unionized ammonia
nitrogen, E. coli, PO4-P and BOD5 levels showed
decreasing trends over the past 30 years.
5.3.6
The E. coli level in the eastern side of Victoria Harbour has
markedly decreased since the Harbour Area Treatment Scheme (HATS) Stage 1
commissioned in December 2001. With full commissioning of the HATS Stage 2A in
December 2015, the E. coli level of the central harbour area has been
further reduced.
Water Quality in Tolo
Harbour
5.3.7
The marine water quality monitoring results at station in vicinity of
the Project, namely TM2 is shown in Table 5.6 below. Full compliances
with the WQO was recorded at the selected EPD station TM2 for DO (depth average
and bottom), chlorophyll-a and E. coli in 2020.
Table 5.6 Baseline
Water Quality Condition for Tolo Harbour and Channel WCZ in 2020
|
Parameters
|
Harbour
Subzone
|
WPCO
WQO
(in
marine waters)
|
|
TM2
|
|
Temperature
(℃)
|
26.3
(20.6 - 29.8)
|
Change due to waste
discharge not to exceed ±1℃ and not to exceed 0.5℃ per hour
at any location
|
|
Salinity
|
29.9
(24.8
- 32.8)
|
Change due to waste
discharge not to be greater than ±3ppt at any time
|
|
Dissolved Oxygen (DO)
(mg/L)
|
Depth Average
|
6.1
(5.1
- 7.9)
|
Not less than 4 mg/L
in the water column (except for the bottom water within 2 m from the seabed)
|
|
|
Bottom
|
6.2
(4.5
- 8.3)
|
Not less than 2 mg/L
within 2 m from the seabed
|
|
Dissolved Oxygen
(% Saturation)
|
Depth
Average
|
89
(73
- 112)
|
Not
available
|
|
|
Bottom
|
90
(70
- 120)
|
Not
available
|
|
pH
|
8.0
(7.7 -
8.3)
|
Change due to waste
discharge not to be greater than ±0.5 pH units at any time.
|
|
Secchi Disc Depth
(m)
|
2.4
(1.6 -
3.4)
|
Not available
|
|
Turbidity
(NTU)
|
3.1
(1.5 -
5.5)
|
Not available
|
|
Suspended Solids (SS)
(mg/L)
|
8.1
(1.4 -
17.0)
|
Not available
|
|
5-day Biochemical Oxygen Demand
(BOD5) (mg/L)
|
1.7
(0.8 -
2.6)
|
Not available
|
|
Ammonia Nitrogen
(mg/L)
|
0.045
(0.022 -
0.076)
|
Not available
|
|
Unionized Ammonia (UIA)
(mg/L)
|
0.003
(<0.001
- 0.005)
|
Not available
|
|
Nitrite Nitrogen
(mg/L)
|
0.004
(<0.002
- 0.010)
|
Not available
|
|
Nitrate Nitrogen
(mg/L)
|
0.039
(<0.002
- 0.215)
|
Not available
|
|
Total Inorganic Nitrogen (TIN)
(mg/L)
|
0.09
(0.03 -
0.27)
|
Not available
|
|
Total Kjeldahl Nitrogen
(mg/L)
|
0.50
(0.22 -
0.81)
|
Not available
|
|
Total Nitrogen
(mg/L)
|
0.54
(0.29 -
0.82)
|
Not available
|
|
Orthophosphate Phosphorus
(PO4-P) (mg/L)
|
0.008
(0.002 -
0.026)
|
Not available
|
|
Total Phosphorus
(mg/L)
|
0.04
(<0.02
- 0.06)
|
Not available
|
|
Silica (as SiO2)
(mg/L)
|
1.48
(0.50 -
4.15)
|
Not available
|
|
Chlorophyll-a
(µg/L)
|
5.8
(1.4 -
9.2)
|
Harbour Subzone: Not
to exceed 20 µg/L, calculated as a running arithmetic mean of 5 daily
measurements for any single location and depth.
|
|
E. coli
(cfu/100mL)
|
13
(<1 -
4500)
|
Not to exceed 610
cfu/100mL for geometric mean of all samples collected in one calendar year
|
|
Faecal Coliforms
(cfu/100mL)
|
76
(6 -
32000)
|
Not available
|
Note: 1. Data
source: EPD Marine Water Quality in Hong Kong in 2020
2. Unless
otherwise specified, data presented are depth-averaged values calculated by
taking the means of three depths: Surface, Mid-depth, Bottom.
3. Data
presented are annual arithmetic means of depth-averaged results except for E.
coli and faecal coliforms that are annual geometric means.
4. Data
in brackets indicate the ranges.
5. cfu – colony forming
unit.
Trend of Water Quality
in Tolo Harbour
5.3.8
The monitoring results of key water quality parameters indicate that the
overall WQO compliance rate of the Tolo Harbour and Channel WCZ in 2020 was 93%.
Tolo Harbour consistently complied with the bacteriological WQO for secondary
contact recreational uses applicable to the entire marine waters of the WCZ.
Tolo Channel, however, was subject to a natural hydrological phenomenon of
water column stratification and associated lower bottom DO level due to
restricted water exchange with the open waters.
5.3.9
In the mid-1980s, with the implementation of the Tolo Harbour Action
Plan, which includes the control of livestock waste, the provision and
improvement of sewerage, the export of treated sewage effluent from Sha Tin and
Tai Po Sewage Treatment Works outside Tolo Harbour for discharging into
Victoria Harbour via Kai Tak River, as well as the extension of village
sewerage in the catchment area, there has been a steady improvement in water
quality in Tolo Harbour in the past three decades.
Inland Water
Water Quality in Shing
Mun River and its Tributaries
5.3.10
Section of Shing Mun River, and its tributaries including Kwun Yam Shan
Stream and Tin Sum Nullah are located within the study area, the corresponding
water quality monitoring results at stations, namely TR19I, KY1 (closest to the
Project Site) and TR20B, are shown in Table 5.7 below.
Table 5.7 Baseline
Water Quality Condition for Shing Mun River and its Tributaries in 2020
|
Parameters
|
Shing
Mun
Main
Channel
|
Kwun
Yam Shan Stream
|
Tin
Sum Nullah
|
WPCO
WQO
(in
inland waters)
|
|
TR19I
|
KY1
|
TR20B
|
|
Dissolved Oxygen (DO)
(mg/L)
|
6.7
(4.4 -
8.0)
|
8.1
(7.9 - 9.2)
|
7.9
(7.7 - 8.9)
|
≥ 4 mg/L or 40% saturation (at 15℃)
|
|
pH
|
8.1
(7.6 -
8.9)
|
8.4
(8.2 -
8.8)
|
7.7
(6.8
- 8.9)
|
within 6.0 - 9.0 for TR19I;
within 6.5 - 8.5 for KY1 and TR20B
|
|
Suspended Solids (SS)
(mg/L)
|
3.5
(1.4 -
16.0)
|
5.3
(2.4 -
9.3)
|
0.5
(<0.5
- 1.1)
|
Annual median:
≤ 25 mg/L, for TR19I;
≤ 20 mg/L, for KY1 and TR20B
|
|
5-day Biochemical Oxygen Demand
(BOD5) (mg/L)
|
3.1
(1.7 -
8.5)
|
0.5
(<0.1 -
1.1)
|
<0.1
(<0.1 -
0.4)
|
≤ 5 mg/L, for TR19I and TR20B;
≤ 3 mg/L, for KY1
|
|
Chemical Oxygen Demand (COD)
(mg/L)
|
13
(8 - 24)
|
4
(<2 -
7)
|
5
(<2
- 9)
|
≤ 30 mg/L, for TR19I and TR20B;
≤ 15 mg/L, for KY1
|
|
Oil & Grease
(mg/L)
|
<0.5
(<0.5 -
<0.5)
|
<0.5
(<0.5 -
<0.5)
|
<0.5
(<0.5 -
<0.5)
|
Not available
|
|
E. coli
(cfu/100mL)
|
140
(40 - 630)
|
87
(30 - 330)
|
<1
(<1 - <1)
|
running median of the most recent 5 consecutive samples
taken at intervals of between 7 and 21 days (or 14 and 42 days):
≤ 1,000 cfu/100mL, for TR19I and TR20B;
≤ 0 cfu/100mL, for KY1
|
|
Faecal Coliforms
(cfu/100mL)
|
2,500
(810 –
56,000)
|
800
(160 –
3,800)
|
<1
(<1 - <1)
|
Not available
|
|
Ammonia Nitrogen
(mg/L)
|
0.130
(0.058 -
0.230)
|
0.023
(0.015 -
0.032)
|
0.034
(0.014
- 0.180)
|
≤ 0.5 mg/L
|
|
Nitrate Nitrogen
(mg/L)
|
0.130
(0.014 -
0.510)
|
0.305
(0.140 -
0.650)
|
0.910
(0.470
- 1.800)
|
Not available
|
|
Total Kjeldahl Nitrogen
(mg/L)
|
0.58
(0.22 -
0.92)
|
0.13
(<0.05
- 0.34)
|
0.20
(<0.05
- 0.29)
|
Not available
|
|
Orthophosphate Phosphorus
(PO4-P) (mg/L)
|
0.027
(0.014 -
0.047)
|
0.054
(0.009 -
0.088)
|
0.012
(0.007
- 0.130)
|
Not available
|
|
Total Phosphorus
(mg/L)
|
0.05
(0.04 - 0.40)
|
0.10
(0.08 -
0.13)
|
0.02
(<0.02
- 2.50)
|
Not available
|
|
Sulphide
(mg/L)
|
<0.02
(<0.02
- <0.02)
|
<0.02
(<0.02
- <0.02)
|
<0.02
(<0.02
- <0.02)
|
Not available
|
|
Aluminium (Al)
(µg/L)
|
<50
(<50 -
<50)
|
93
(<50 -
267)
|
64
(<50 - 210)
|
Not available
|
|
Cadmium (Cd)
(µg/L)
|
<0.1
(<0.1 -
<0.1)
|
<0.1
(<0.1 -
<0.1)
|
<0.1
(<0.1 -
0.7)
|
Not available
|
|
Chromium (Cr)
(µg/L)
|
2
(2 - 4)
|
<1
(<1 -
<1)
|
<1
(<1 - <1)
|
Not available
|
|
Copper (Cu)
(µg/L)
|
5
(3 - 6)
|
<1
(<1 -
1)
|
1
(<1 - 3)
|
Not available
|
|
Lead (Pb)
(µg/L)
|
<1
(<1 -
<1)
|
<1
(<1 -
<1)
|
<1
(<1 - <1)
|
Not available
|
|
Zinc (Zn)
(µg/L)
|
<10
(<10 -
16)
|
<10
(<10 -
<10)
|
<10
(<10 -
13)
|
Not available
|
|
Flow
(m3/s)
|
NM
|
0.008
(0.001 -
0.046)
|
0.024
(0.015
- 0.098)
|
Not available
|
Note: 1. Data
source: EPD River Water Quality in Hong Kong in 2020
2. Data
presented are in annual medians of monthly samples; except those for faecal
coliforms and E. coli and which are in annual geometric means.
3. Figures
in brackets are annual ranges.
4. “NM”
indicates no measurement taken.
5. cfu – colony forming
unit
Trend of Water Quality
in Shing Mun River and its Tributaries
5.3.11
Shing Mun River, a major river which has three main tributaries and runs
through the densely populated Sha Tin urban area, showed marked improvement
during the past three decades. The WQO compliance rate of Shing Mun River was 90%
in 2020.
5.3.12
Shing Mun River Main Channel (TR19I) is currently used for secondary
contact recreation activities in Hong Kong, was rated “Excellent” in 2020, while
it was rated “Good” in 2019.
Water Quality in Kai
Tak River
5.3.13
Project Area at the Kowloon side of the Lion Rock Tunnel falls within
the catchment area of Kai Tak River. The water quality monitoring results at
station in vicinity of the Project, namely KN7 is shown in Table
5.8 below. Kai Tak River had a WQO compliance rate of 85% in 2020, four
monitoring stations in Kai Tak River maintained “Good” while two downstream
stations were graded as “Fair” in 2020.
Table 5.8 Baseline
Water Quality Condition for Kai Tak River in 2020
|
Parameters
|
Kai
Tak River
|
WPCO
WQO
(in
inland waters)
|
|
KN7
|
|
Dissolved Oxygen (DO)
(mg/L)
|
7.2
(6.9 -
7.9)
|
≥ 4 mg/L
|
|
pH
|
7.2
(7.1 -
7.6)
|
within 6.0- 9.0
|
|
Suspended Solids (SS)
(mg/L)
|
6.7
(4.1 - 11.0)
|
Annual median ≤ 25 mg/L
|
|
5-day Biochemical Oxygen Demand
(BOD5) (mg/L)
|
9.1
(2.7 -
11.0)
|
≤ 5 mg/L
|
|
Chemical Oxygen Demand (COD)
(mg/L)
|
27
(10 - 32)
|
≤ 30 mg/L
|
|
Oil & Grease
(mg/L)
|
<0.5
(<0.5 -
<0.5)
|
Not available
|
|
E. coli
(cfu/100mL)
|
3 300
(1 100 - 12
000)
|
The geometric mean of the most recent 5 consecutive
samples taken at intervals of between 7 and 21 days:
≤ 1,000 cfu/100mL
|
|
Faecal Coliforms
(cfu/100mL)
|
6 400
(2 400 -
56 000)
|
Not available
|
|
Ammonia Nitrogen
(mg/L)
|
1.400
(0.360 -
3.900)
|
Not available
|
|
Nitrate Nitrogen
(mg/L)
|
3.700
(2.600 -
4.500)
|
Not available
|
|
Total Kjeldahl Nitrogen
(mg/L)
|
4.20
(0.96 -
5.30)
|
Not available
|
|
Orthophosphate Phosphorus
(PO4-P) (mg/L)
|
0.700
(0.490 -
1.300)
|
Not available
|
|
Total Phosphorus
(mg/L)
|
1.30
(0.55 - 1.60)
|
Not available
|
|
Sulphide
(mg/L)
|
<0.02
(<0.02
- <0.02)
|
Not available
|
|
Aluminium (Al)
(µg/L)
|
<50
(<50 -
78)
|
Not available
|
|
Cadmium (Cd)
(µg/L)
|
<0.1
(<0.1 -
<0.1)
|
Not available
|
|
Chromium (Cr)
(µg/L)
|
1
(<1 -
2)
|
Not available
|
|
Copper (Cu)
(µg/L)
|
3
(2 - 4)
|
Not available
|
|
Lead (Pb)
(µg/L)
|
<1
(<1 -
<1)
|
Not available
|
|
Zinc (Zn)
(µg/L)
|
14
(11 - 21)
|
Not available
|
|
Flow
(m3/s)
|
2.760
(1.166 -
4.572)
|
Not available
|
Trend of Water Quality
in Kai Tak River
5.3.14
The water quality of the Kai Tak River improved from mostly “Very Bad”
in 1986 to “Good” and “Fair” in 2020. The E. coli level in rivers in
the Kowloon district has been reduced by over 90% compared with 1999. It was
expected that the water quality of Kai Tak River would further improve, upon
completion of the sewerage repair and upgrading works in the river catchment
area by the DSD and other improvement works in the Kai Tak Development Area by
the CEDD.
5.4.1
According to Item 3.4.6.2 of the Study Brief, the assessment area for
this water quality impact assessment includes areas within 500 metres from the
boundary of the Project and covers the Tolo Harbour and Channel WCZ as well as
the Victoria Harbour (Phase Two) WCZ as designated under the WPCO and the water
sensitive receivers (WSRs) in the vicinity of the Project. WSRs within the study
area were identified with reference to Annex 14 of the EIAO-TM.
5.4.2
Key WSRs within 500m from the boundary of the Project were identified at
Table 5.9 below and their respective locations are illustrated in 60604728/R42b/Figure 5.2.
Table 5.9 Water
Sensitive Receivers
|
ID
|
Location
|
Nature
|
Description
|
|
S1
|
Mau Tsai
Shan
|
Natural
watercourse
|
Moderate flow rate and
comprised of natural sandy and rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S2
|
Sha Tin Tau
New Village
|
Semi-natural
watercourse
|
Natural at the upper
section. Section at Sha Tin Tau New Village has modified concrete bank but
natural rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S3
|
Kak Tin
Village
|
Natural
watercourse
|
Joins with S4 before
discharging to a modified channel. Low to moderate flow and comprised of
natural sandy and rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S4
|
Hung Mui
Kuk Village
|
Natural
watercourse
|
Joins with S3 before
discharging to a modified channel. Low to moderate flow and comprised of
natural sandy and rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S5
|
Hung Mui
Kuk Picnic Site
|
Natural
watercourse
|
Joins two tributaries
to a channelised lower section near Lion Rock Tunnel Road.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S6
|
Lion Rock
towards Tei Lung Hau
|
Natural
watercourse
|
Flow from Lion Rock
and comprised of natural rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S7
|
Beacon
Hill towards Lion Rock Tunnel Shatin Portal
|
Natural
watercourse
|
Moderate flow from
Beacon Hill into a nullah. Comprised of natural sandy and rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S8
|
Beacon
Hill towards Tei Lung Hau
|
Semi-natural
watercourse
|
Middle section at east
of Shatin South Fresh Water Service Reservoir is channelised. Comprised of
natural sandy and rocky substratum.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
S9
|
Beacon
Hill towards Tin Sum Nullah
|
Semi-natural
watercourse
|
Natural at the upper
section. Joins Tin Sum Nullah near Shatin Water Treatment Works. One of the
tributaries of Shing Mun River.
Permanent flow from
south to north, finally discharged to Shing Mun River.
|
|
SW1
|
Within
Lion Rock Country Park
|
Natural
watercourse
|
Natural seasonal
watercourse which joins with S4 at Hung Mui Kuk, predominantly dry, no
evident surface flow was observed during dry and wet seasons.
|
|
SW2
|
Within
Lion Rock Country Park
|
Natural
watercourse
|
Natural seasonal
watercourse, predominantly dry, no evident surface flow was observed during
dry and wet seasons.
|
|
SW3
|
Within
Lion Rock Country Park
|
Natural
watercourse
|
Natural seasonal
watercourse, predominantly dry, no evident surface flow was observed during
dry and wet seasons.
|
|
SW4
|
Within
Lion Rock Country Park
|
Natural
watercourse
|
Natural seasonal
watercourse which joins with WC8 near Lion Rock
Tunnel Road, predominantly dry, no evident surface flow was observed
during dry and wet seasons.
|
|
SW5
|
Watercourse
west of Lion Rock Park
|
Natural
watercourse
|
Natural seasonal
watercourse with flow running from north to south, finally discharged to
Victoria Harbour.
|
|
SW6
|
Watercourse
west of Lion Rock Park
|
Natural
watercourse
|
Natural seasonal
watercourse with flow running from north to south, finally discharged to
Victoria Harbour.
|
|
WC1
|
Catchwater
|
Channelised
watercourse
|
Catchwater which lead
to Kowloon Reservoir.
|
|
WC2
|
Watercourse
southeast of Ha Keng Hau
|
Channelised
watercourse
|
Concrete
step-channel with very limited water flow.
Seasonal flow from
south to north, finally discharged to Shing Mun River.
|
|
WC3
|
Watercourse
south of LRT Toll Plaza
|
Channelised
watercourse
|
Concrete
banks and discharges to an underground culvert. No water flow was observed.
Seasonal flow from
south to north, finally discharged to Shing Mun River.
|
|
WC4
|
Watercourse
west of Lion Rock Park
|
Semi-natural
watercourse
|
Natural at the upper
section. Section near the service reservoir is channelised which discharges to an underground culvert. Received
shallow water occasionally.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC5
|
Watercourse
west of Lion Rock Park
|
Semi-natural
watercourse
|
Natural at the upper
section. Section near the Kowloon Portal is channelised which discharges to an underground culvert. Received
shallow water occasionally.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC6
|
Watercourse
west of Lion Rock Park
|
Channelised
watercourse
|
Concrete
banks and discharges to an underground culvert. Received shallow water
occasionally.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC7
|
Watercourse
west of Lion Rock Park
|
Channelised
watercourse
|
Concrete
banks and discharges to an underground culvert. Received shallow water
occasionally.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC8
|
Within
Lion Rock Country Park
|
Channelised
watercourse
|
Modified watercourse
which joins with SW4 near Lion Rock Tunnel Road, predominantly dry.
|
|
WC9
|
Watercourse
south of Tin Ma Court
|
Channelised
watercourse
|
Concrete
banks with limited water flow.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC10
|
Watercourse
north of Tin Ma Court
|
Channelised
watercourse
|
Concrete
banks with limited water flow.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC11
|
Watercourse
near Sha Tin Tau
|
Channelised
watercourse
|
Concrete
modified watercourse with very limited water flow.
Seasonal flow from
south to north, finally discharged to Shing Mun River.
|
|
WC12
|
Watercourse
near Golden Lion Garden
|
Channelised
watercourse
|
Concrete
modified watercourse with very limited water flow.
Seasonal flow from
south to north, finally discharged to Shing Mun River.
|
|
WC13
|
Watercourse
north of Lion Rock Park
|
Semi-natural
watercourse
|
Natural at the upper
section. Section near the service reservoir is channelised which discharges to an underground culvert. With
limited water flow.
Seasonal flow from
north to south, finally discharged to Kai Tak River.
|
|
WC14
|
Watercourse
west of Lion Rock Park
|
Semi-natural
watercourse
|
Natural at the upper
section. Section near the service reservoir is channelised.
Seasonal flow from
north to south, finally discharged to Victoria Harbour.
|
|
WC15
|
Watercourse
near Jade Garden
|
Channelised
watercourse
|
Concrete
banks with limited water flow.
Seasonal flow from
north to south, finally discharged to Victoria Harbour.
|
|
P1
|
Ponds near
Sha Tin Tau New Village
|
Concrete
ponds
|
Small
inactive ponds near the village housing at Sha Tin Tau New Village.
|
|
P2
|
Ponds near
Sha Tin Tau New Village
|
Concrete
ponds
|
Small
inactive ponds near the village housing at Sha Tin Tau New Village.
|
|
S10
|
Within
Lion Rock Country Park
|
Water
Gathering Ground
|
Rainwater
is collected via catchwaters and is then stored in Kowloon Reservoir.
|
|
S11
|
Beacon
Hill
|
Site of
Special Scientific Interest
|
Designated
as a SSSI because of its rich floral diversity and the rare ferns and unusual
orchids.
|
|
S12
|
Lion Rock Country
Park
|
Country
Park
|
-
|
5.4.3
Tin Sum Nullah (part of S9) is one of the tributaries of Shing Mun
River. The main channel of Shing Mun River is currently used for secondary
contact recreation activities, it runs through the densely populated Shatin
urban areas and drains into Tolo Harbour. There are natural streams (S2 to S9)
running across the Sha Tin Tau New Village and Lion Rock Country Park. A
number of streams (S1 to S9) also runs down from the hills (Kwun Yam Shan, Tei
Lung Hau, Beacon Hill, Lion Rock, Unicorn Ridge and Temple Hill). As shown in 60604728/R42b/Figure 5.2, S7 and S8 are watercourses located
in close proximity to the project site while S2 to S6 are watercourses running
underneath the project site. The small section of S7 near an engineered slope
crest above the Lion Rock Tunnel Shatin portals is located approximately 20 m
from the Project footprint and would not be directly affected by construction
works. Although some of the sections of S3 and S5 are located within works
boundary, there is no construction works to be conducted at/within S3 and S5.
5.4.4
SW1, SW2, SW3 and SW4 are natural seasonal watercourses at Shatin side running
underneath the project site. These seasonal watercourses are predominantly dry
and no evident surface flow was observed during dry and wet seasons. Although
some of the sections of SW1 are located within works boundary, there is no
construction works to be conducted at/within SW1. SW5 and SW6 is a natural
seasonal watercourse at Kowloon side which originate from the hillslope area of
Beacon Hill and finally leading to Victoria Harbour.
5.4.5
WC1, WC2, WC3, WC8, WC11 and WC12 are all channelized watercourses at
Shatin side. WC1 is a concretized rectangular catchwater located within Lion
Rock Country Park in close proximity to the project site which convey
catchwater to the Kowloon Reservoir. WC1 is located at a higher elevation than
the aboveground works. WC2, located southeast of Ha Keng Hau, is a concrete
step-channel with very limited water flow. WC3 is a small concrete nullah
located at south of the Lion Rock Tunnel toll plaza within the project site.
There is no construction works to be conducted at/within WC3. No water flow
was observed at this modified watercourse. A modified watercourse WC8 linked
to SW4 is a dry nullah which located within Lion Rock Country Park. WC11 and
WC12 are channelized watercourses with flow finally leading to Shing Mun River.
5.4.6
WC4 to WC7, WC9, WC10 and WC13 to WC15 are semi-natural and/or
channelized watercourses at Kowloon side. WC4, WC5, WC13 and WC14 are
semi-natural watercourses (upper section is natural and modified to channel
near service reservoir) in close proximity to the project site which discharge
to an underground culvert. WC6 and WC7 are channelized watercourses in close
proximity to the project site with concrete banks and discharge to an underground
culvert. Although some of the sections of WC4 to WC7 are located within works
boundary, there is no construction works to be conducted at/within WC4 to WC7. WC9,
WC10 and WC15 are channelized watercourses near Jade Garden and Tin Ma Court.
These watercourses (WC4 to WC7, WC9 and WC10) only contained limited water
flow.
5.4.7
P1 and P2 are small inactive ponds which located near the village
housing at Sha Tin Tau New Village. P2 is located in close proximity to the
project site.
5.4.8
It should be noted that this Project would not involve any construction
works at/within the above identified watercourses and ponds.
5.4.9
Although tunneling works will be located within the water gathering
grounds (S10), no aboveground structure would be constructed within the area.
The nearest aboveground structure would be located outside the boundary of the
water gathering ground. The water gathering ground is located at a higher
elevation than the aboveground works. That is, waters are running from the
water gathering grounds towards the Project. 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.
5.4.11
S12 is Lion Rock Country Park which designated in 1977, is one of the
earliest country parks of Hong Kong. It covers a wide upland region set
between North Kowloon and Shatin. The park borders on Kam Shan Country Park to
the west by a boundary line on Tai Po Road, and commands a total area of 557
hectares.
5.5.1
The assessment area includes inland waters within 500 metres from the
boundary of the Project and other areas such as stream courses and the
associated water systems in the vicinity that might be impacted by the Project.
The methodology employed to assess potential water quality impacts associated
with the construction and operation of the Project followed the detailed
technical requirements given in Appendix D of the Study Brief. The WSRs that
may be affected by the Project have been identified. Potential sources of
water quality impact that may arise during the construction and operation
stages of the Project were described, 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 will be evaluated and their impact significance determined.
Practical water pollution control measures will be recommended to mitigate
identified water quality impacts.
Construction Phase
5.6.1
The major construction activities include
demolition, site formation, excavation, foundation, superstructure and building
construction, tunnel and roads widening as well as slope and E&M
works. The potential sources of water quality impact associated with the construction
works would include:
·
Wastewater from general construction activities;
·
Construction site run-off;
·
Sewage from construction workforce;
·
Accidental spillage of chemicals;
·
Groundwater infiltration arising from tunnel boring;
·
Water pollution from culvert modification works;
·
Construction works in close proximity of inland watercourses; and
·
Groundwater from contaminated areas and contaminated site runoff
Wastewater from General
Construction Activities
5.6.2
Various types of construction activities may generate wastewater. These
include general cleaning and polishing, wheel washing, dust suppression sprays
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. Adoption of the guidelines
and good site practices for handling and disposal of construction discharges as
part of the construction site management practices would minimize the potential
impacts.
Construction Site
Run-off
5.6.3
Potential pollution sources of site run-off may include:
·
Run-off and erosion of exposed bare soil and earth, drainage
channel, earth working area and stockpiles;
·
Release of any bentonite slurries, concrete washings and other
grouting materials with construction run-off 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.
5.6.4
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 soil particles that were
contaminated by the construction activities and therefore cause water pollution.
5.6.5
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.
5.6.6
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.
Sewage Effluent from
Construction Workforce
5.6.7
During the construction of the Project, the workforce on site will
generate sewage effluents, which are characterized by high level of BOD,
ammonia and E. coli. Based on the DSD Sewerage Manual, the sewage
production rate for construction workers is estimated at 0.35 m3 per
worker per day. For every 100 construction workers working simultaneously at
the construction site, about 35 m3 of sewage would be generated per
day. Potential water quality impacts upon the local drainage and fresh water
system may arise from these sewage effluent, if uncontrolled.
5.6.8
However, this temporary sewage can be adequately handled by temporary sanitary
facilities, such as portable chemical toilets. According to the Reference
Materials on Construction Site Welfare, Health and Safety Measures that issued
by the Construction Industry Council (i.e. Section 5.6.10), the number of
toilet facilities provided on site shall be at a ratio of not less than 1 for
every 25 workers. The number of the chemical toilets required for the
construction sites should be subject to later 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.
5.6.9
Provided that sewage is not discharged directly into stormwater drains
or inland waters adjacent to the construction site, and temporary sanitary
facilities are used and properly maintained, it is unlikely that sewage
generated from the site would have a significant water quality impact.
Accidental Spillage of
Chemicals
5.6.10
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 rise 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.
Groundwater
Infiltration arising from Tunnel Boring
5.6.11
Underground development may result in infiltration of groundwater. The
major concern from underground construction activities would be the increase in
site runoff and the associated potential drawdown of groundwater in any soil
and aquifer layers. Groundwater infiltration would affect the construction
works and infiltrated water would carry away silt and other contaminants from
site into the site drainage. Consideration should be taken at the early design
stage to minimize the infiltration of groundwater. Underground development may
also drawdown groundwater in any soil and aquifer layers if uncontrolled.
Practical groundwater control measures should be followed to minimize the
potential groundwater infiltration.
Water Pollution from
Culvert Modification Works
Construction Works in
Close Proximity to Inland Water
5.6.13
Construction activities in close vicinity to the inland watercourses (S2
to S8, SW1 to SW4, WC1 to WC8, WC14 and P2; ID refer to Table
5.9 and 60604728/R42b/Figure 5.2) may impact water quality due to
the potential release of construction waste and wastewater. Construction waste
and wastewater are generally characterized by high SS concentration and
elevated pH. With the implementation of adequate construction site drainage
and Best Management Practices as described in Section 5.7.1 - 5.7.2 and provision of mitigation measures as
specified in ETWB TC (Works) No. 5/2005 “Protection of natural streams/ rivers
from adverse impacts arising from construction works” as detailed in Section
5.7.26, it is anticipated that water quality impacts would be
minimal.
Groundwater from
Contaminated Areas and Contaminated Site Runoff
5.6.14
It is identified that the tunnel portal areas have potential land
contamination issues. Proper land contamination remediation and mitigation
measures are proposed in Section 7. Any
contaminated material disturbed, or material which comes into contact with the
contaminated material, has the potential to be washed with site runoff into
drainage system. Excavated contaminated materials would be properly stored,
housed and covered to avoid generation of contaminated runoff. Open
stockpiling of contaminated materials will not be allowed. Any contaminated
site runoff will be properly treated and disposed in compliance with the
requirements of the TM-DSS. Mitigation measures for contaminated site runoff
are recommended under Section 5.7.27.
5.6.15
Groundwater pumped out or from dewatering process during excavation
works in the contaminated areas might be potentially contaminated. Any
contaminated groundwater will be either properly treated or properly recharged
into the ground in compliance with the requirements of the TM-DSS. No direct
discharge of contaminated groundwater will be adopted. Mitigation measures and
monitoring requirements for contaminated groundwater discharge/recharge are
recommended under Section 5.7.28 - 5.7.29.
With proper implementation of the recommended mitigation measures, no
unacceptable water quality would be expected from the groundwater generated from
contaminated areas and contaminated site runoff.
Operation Phase
5.6.16
Potential water quality impacts associated with the Project operation
would include:
· Surface run-off from road/bridge/viaduct;
· Sewage effluent from the new administration building
and ventilation buildings;
· Wastewater generated from washing and maintenance operation;
and
· Tunnel run-off and drainage
Surface run-off from
Road/Bridge/Viaduct
5.6.17
Surface runoff to be generated from the Project is known as non-point
source pollution. The paved and developed areas, especially the new
road/bridge/viaduct 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.
5.6.18
The Project was expected to have an additional 4.72ha paved area when in
operation. According to the DSD Stormwater Drainage Manual, annual
rainfall in Hong Kong is about 2400mm. The EPD study, Update on Cumulative
Water Quality and Hydrological Effect of Coastal Developments and upgrading of
Assessment Tool, 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, it was
assumed that only 1512mm (i.e. 2400mm x (82%+44%)/2) of the 2400mm annual
rainfall would be considered as effective rainfall that would generate surface
runoff. With consideration of the 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 176.0 m3/day (i.e.1512/1000/365*47200*0.9).
5.6.19
Surface runoff generated from the paved or developed areas may contain
debris, refuse and dust. Practices that cleaning agents used for road and
building faced washing may also affect the water quality of the nearby
receiving water. Minor non-point source pollution would be expected from the
Project.
5.6.20
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. The design of stormwater drains
shall follow the relevant guidelines and practices as given in the ProPECC PN
5/93 “Drainage Plans subject to Comment by the EPD”.
Sewage effluent from
New Administration Building and Ventilation Buildings
5.6.21
Sewage generated from the new administration building and ventilation
buildings under the operation phase is characterized by high level of BOD,
ammonia and E. coli. It would not cause adverse water quality impacts
if the sewage and wastewater generated from the proposed development would be
properly treated and disposed. The estimation of sewage and other wastewater
generated from operation of the proposed administration building, car parking
area and ventilation buildings is summarized in Table
5.10 below.
Table 5.10 Estimation
of Sewage and Other Wastewater from New Administration Building, Car Parking
Area and Ventilation Buildings
|
Wastewater
Generated from
|
Type
of Wastewater Generated
|
Estimated
Serving Population / Size
|
Estimated
Quantity of Wastewater
|
Proposed
Wastewater Treatment Method
|
|
To On-site Sewage Treatment Plant (STP)
|
|
New
Administration Building
|
Sewage from Toilet
|
150 staff
(Estimated Total No. of Tunnel Operating Staff)
|
150 staff x 0.18 m3/staff/day
(1)
= 27 m3/day
|
On-site STP adjacent to new Administration Building
|
|
|
Effluent from food
preparation and utensils washing
|
6 staff
(Estimated Total No. of Canteen Staff)
|
6 staff x 1.58 m3/
staff/day (2)
= 9.48 m3/day
|
Grease Trap before treated at on-site STP adjacent to new
Administration Building
|
|
Car Parking Area
|
Washing and
maintenance activities of tunnel work vehicles
|
60 nos. of
tunnel works vehicles
|
60 vehicles
x 0.17 m3/vehicle/7
day
= ~1.5 m3/day
(each tunnel work vehicle is to be washed manually using
wet towels once per week)
|
Petrol interceptor following by sedimentation tank before
treated at on-site STP adjacent to new Administration Building
|
|
|
|
Total:
|
~38 m3/day
|
|
|
To Septic Tank and Soakaway System (ST/SA system)
|
|
Ventilation
Building at Shatin Portal
|
Sewage from Toilet
|
Estimated no more than 5 staff
|
5 staff x 0.18 m3/staff/day
(1)
= 0.9 m3/day
|
ST/SA system adjacent to new Ventilation Building
|
|
|
Washing and maintenance
activities of ventilation systems
|
Not
Applicable
|
0.5 m3/day
(general cleansing
using water and vacuuming only)
|
Carbon filter before discharging to ST/SA system
|
|
Ventilation Building
at Kowloon Portal
|
Sewage from Toilet
|
Estimated no more than 5 staff
|
5 staff x 0.18 m3/staff/day
(1)
= 0.9 m3/day
|
ST/SA system adjacent to new Ventilation Building
|
|
|
Washing and
maintenance activities of ventilation systems
|
Not
Applicable
|
0.5 m3/day
(general cleansing
using water and vacuuming only)
|
Carbon filter before discharging to ST/SA system
|
|
|
|
Total:
|
~3 m3/day (~1.5 m3/day from each
new Ventilation Building)
|
Note: 1. Value
refers to the commercial activity Type J3 of Table T-2 of the “Guidelines
for Estimating Sewage Flows for Sewage Infrastructure Planning” issued by
EPD.
2. Value
refers to the commercial activity Type J10 of Table T-2 of the “Guidelines
for Estimating Sewage Flows for Sewage Infrastructure Planning” issued by
EPD.
5.6.22
There is no existing nearby public sewer serving the new administration
building and car parking area while the nearest public sewer connection is
located approximately 300m away from the new administration building and car
parking area. It is also foreseeable that there is difficulty in the
maintenance (i.e., replacement and repair works) of the public sewer connection
to the new administration building and car parking area since portion of the
sewer connection will be running across the trunk road at the toll plaza area.
The on-site sewage treatment plant (STP) instead of public sewer connection for
the new administration building and car parking area is therefore adopted. All
sewage and wastewater generated from the new administration building and car parking
area would be treated by the STP before discharging to the nearby road drainage
system outside Lion Rock Country Park. The on-site sewage treatment facility
will be designed generally with reference to EPD’s “Guidelines for the
Design of Small Sewage Treatment Plant”.
5.6.23
Source of sewage generated from the operation of the new administration
building include tunnel operating staff (i.e. estimated total 150 nos.) and
staff canteen (with about 6 staff). The estimated average dry weather flow
(ADWF) generated from the operation of the new administration building is about
36.5 m3/day (i.e. 150 x 0.18 m3/day/employee for
Commercial type J3 + 6 x 1.58 m3/day/employee for Commercial Type
J10). Both sewage and wastewater from the new administration building and car
parking area will be treated by the on-site STP. As presented
in Table 5.10, the estimated ADWF for
sewage and wastewater to be discharged to the on-site STP is about 38 m3/day
(27 m3/day + 9.48 m3/day + 1.5 m3/day = ~38 m3/day)
and the estimated peak flow for sewage and wastewater to be discharged to the
on-site STP is about 2.64 L/s (with peaking factor of 6 as stated in Section
3.3 of “Guidelines for the Design of Small Sewage Treatment Plant”).
The on-site STP is designed with capacity to handle a peak flow of three times
of ADWF (i.e. 38 m3/day x 3 = 114 m3/day) with provision
of equalization tank to store three times of ADWF for 2 hours (i.e. minimum 9.5
m3) for the surplus flow. The on-site STP in the type of Membrane
Bio-reactor (MBR) with UV disinfection will be adopted and installed within the
footprint area of the administration building. There is a need to apply to EPD
for a discharge licence for effluent discharge from the on-site STP under the
WPCO. The treated effluent of the MBR plant will be discharged to the adjacent
road drainage system outside Lion Rock Country Park and subsequently discharge
to Shing Mun River and shall meet the effluent standards of Group D inland
water as specified in TM-DSS (see Table 5.4).
5.6.24
In addition, an emergency storage tank with 2 hours of ADWF capacity (i.e.
~3.2 m3) will also be provided for temporary storage of sewage and
the stored sewage will be tankered away if the operation of STP is anticipated
could not be resumed before all the temporary storage capacity utilized, to
avoid emergency discharge to drainage system. To further minimize the
potential emergency discharge from the on-site STP, dual or standby power
supply, standby sewage treatment units, flow sensors and alarm systems should
be provided. Level sensors connected with alarm signalizing system will also
be installed, to monitor the storage volume to avoid overflow of untreated wastewater/raw
sewage. A warning signal will be generated automatically to alert the manager
when the flow in the tank reached a pre-set level, allowing sufficient time for
arranging tanker service to tanker away excessive untreated wastewater/raw
sewage. Some spare parts such as electrical and mechanical components of the
proposed STP will also be provided in case of facilities break down /
emergency. Regular test, maintenances and replacement of membranes or
equipment are necessary to maintain a good operation condition. Hence, no adverse water quality impact would therefore be
anticipated.
5.6.25
The wastewater generated from canteen usually contains greasy waste.
Grease trap will be installed for the wastewater generated from the canteen
before being treated at the on-site STP. No adverse water quality would
therefore be anticipated.
5.6.26
There is no existing public sewer serving the new ventilation buildings
at Kowloon and Shatin portals while the nearest public sewer connections are
also some distance away (i.e. >250m for the new ventilation building at
Kowloon portal and >650m for the new ventilation building at Shatin portal).
It is also anticipated that there is difficulty in the maintenance (i.e.,
replacement and repair works) of the public sewer connection/sewer connection
to the new ventilation buildings since portion of the sewer connection will be
running across approaching road at the Shatin portal and trunk road at the Lung
Cheung Road Interchange. Besides, the new ventilation building at Shatin
portal is also approximately 400m away from the proposed STP of which to be
located near the new administration building. Therefore, the septic tank with
soakaway system is adopted for both new ventilation buildings. The use of
septic tank with soakaway system for the new ventilation buildings at both
portals is considered adequate in view of minimal no. of tunnel operation staff
required to be stationed at the new ventilation buildings. The design of
septic tank with soakaway system shall follow the relevant guidelines and
practices as given in the ProPECC PN 5/93 “Drainage Plans subject to Comment
by the EPD”. No adverse water quality impact would therefore be
anticipated.
5.6.27
Regular maintenance shall be provided to all components of the
wastewater treatment system in new administration building and ventilation
buildings, including the on-site STP, septic tank with soakaway system, grease
traps, etc. No adverse water quality impact would therefore be anticipated.
Wastewater generated
from washing and maintenance operation
5.6.28
Wastewater will be generated from washing and maintenance activities of work
vehicles at car parking area as well as the maintenance activities for
ventilation system. Direct discharge of the generated wastewater to the nearby
drainage system and water environment will create potential water quality
impact.
5.6.29
The anticipated quantity of the wastewater from washing and maintenance
activities of ventilation system is 0.5 m3/day as it requires
general cleansing (using water and vacuuming cleaning only). The wastewater
generated from general cleansing of ventilation system is merely with dusts and
undissolved oils. Wastewater discharging during washing and maintenance
activities of ventilation system will be collected, treated with active carbon
filter before discharge to the septic tank.
5.6.30
The anticipated quantity of the wastewater from washing and maintenance
activities of work vehicles at car parking area is estimated about 1.5 m3/day.
Wastewater from washing and maintenance activities of work vehicles usually contains
hydrocarbon pollutants such as petroleum and diesel. All wastewater generated
from washing and maintenance activities of work vehicles at car parking area
should be collected and treated by petrol interceptor following by
sedimentation tank before discharge to the on-site STP. Regular maintenance shall
be provided to all components of the wastewater treatment system, including the
on-site STP, petrol interceptor, sedimentation tank, active carbon filter
system, etc. A Licensed Chemical Contractor should be employed to collect and
dispose of spent lubrication oil generated from vehicle maintenance activities
in compliance with the Waste Disposal Ordinance. No adverse water quality
impact would therefore be anticipated.
Tunnel run-off and
drainage
5.6.31
During rainstorm, rainwater on the open and at-grade section may
generate tunnel run-off. Seepage of groundwater into the tunnel may also
generate tunnel run-off. Such run-off may contain limited amount of SS, oil
and grease. Directly discharge of tunnel run-off may cause adverse water
quality impact on nearby water environment.
5.6.32
The tunnel wall should be equipped with water-tight liner to avoid
groundwater seepage. The amount of groundwater seepage into the tunnel would
be insignificant. Any tunnel run-off could be contaminated with limited amount
of lubricants, SS, iron, oil and grease from passing vehicles. Standard
oil/grit interceptors/chambers should be provided to remove oil, lubricants,
grease, silt and grit from the tunnel run-off before discharging into public
drainage system. No adverse water quality impacts would be expected.
Construction Phase
General Construction
Activities and Construction Site Run-off
5.7.1
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.
5.7.2
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. 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 Site
Run-off
5.7.3
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.
5.7.4
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.
5.7.5
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.
5.7.6
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.
5.7.7
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.
5.7.8
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.
5.7.9
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.
5.7.10
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
5.7.11
Water used in ground boring and drilling for site investigation or rock
/ soil anchoring should as far as practicable be re-circulated after
sedimentation. When there is a need for final disposal, the wastewater should
be discharged into storm drains via silt removal facilities.
Wheel Washing Water
5.7.12
All vehicles and plants should be cleaned before they leave a
construction site to minimise the deposition of earth, mud, debris on roads. A
wheel washing bay should be provided at every site exit of 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 backfall to reduce vehicle
tracking of soil and to prevent site runoff from entering public road drains.
Rubbish and Litter
5.7.13
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
5.7.14
There is a need to apply to EPD for a discharge licence for discharge of
effluent from the construction site under the WPCO. The discharge quality must
meet the requirements specified in the discharge licence. All the 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.
Acid Cleaning, Etching
and Pickling Wastewater
5.7.15
Acidic wastewater generated from acid cleaning, etching, pickling and
similar activities should be neutralised to within the pH range of 6 to 10
before discharging into foul sewers. If there is no public foul sewer in the
vicinity, the neutralized wastewater should be tankered off site for disposal
into foul sewers or treated to a standard acceptable to storm drains and the
receiving waters.
Sewage Effluent from
Construction Workforce
5.7.16
No discharge of sewage to the stormwater drains and inland water will be
allowed. Adequate and sufficient portable chemical toilets should be provided
in the works areas to handle sewage from construction workforce. A licensed
collector should be employed to clean and maintain the chemical toilets on a
regular basis.
5.7.17
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 should be conducted to
provide an effective control of any malpractices and achieve continual
improvement of environmental performance on site.
Accidental Spillage of
Chemicals
5.7.18
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. The Contractor is also recommended to
develop management procedures for chemicals used and prepare an emergency
spillage handling procedure to deal with chemical spillage in case of accident
occurs.
5.7.19
Any service shop and maintenance facilities should be located on hard
standings within a bunded area, and sumps and oil interceptors should be
provided. Maintenance of vehicles and equipment involving activities with
potential for leakage and spillage should only be undertaken within the areas
appropriately equipped to control these discharges.
5.7.20
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.
Groundwater
Infiltration arising from Tunnel Boring
5.7.21
Appropriate measures should be implemented to minimize the groundwater
infiltration during the tunnel construction. The groundwater control
strategies include:
·
Probing Ahead: As normal practice, the Contractor will undertake
rigorous probing of the ground ahead of excavation works to identify zones of
significant water inflow. The probe drilling results will be evaluated to
determine specific grouting requirements in line with the tunnel advance. In
such zones of significant water inflow that could occur as a result of
discrete, permeable features, the intent would be to reduce overall inflow by
means of cut-off grouting executed ahead of the tunnel advance.
·
Pre-grouting: Where water inflow quantities are excessive,
pre-grouting will be required to reduce the water inflow into the tunnel. The
pre-grouting will be achieved via a systematic and carefully specified protocol
of grouting.
·
In principle, the grout pre-treatment would be designed on the
basis of probe hole drilling ahead of the tunnel face.
·
The installation of waterproof lining would also be adopted after
the formation of the tunnels.
5.7.22
In the event of excessive infiltration being observed as a result of the
tunnelling or excavation works even after incorporation of the water control
strategies, post-grouting should be applied as far as practicable as described
below:
·
Post-grouting: Groundwater drawdown will be most likely due to
inflows of water into the tunnel that have not been sufficiently controlled by
the pre-grouting measures. Where this occurs, post grouting will be undertaken
before the lining is casted. Whilst unlikely to be required in significant
measure, such a contingency should be allowed for reduction in permeability of
the tunnel surround (by grouting) to limit inflow to acceptable levels.
5.7.23
The practical groundwater control measures stated above are proven
technologies and have been extensively applied in other past projects. These
measures or other similar methods, as approved by the Engineer to suit the
works condition shall be applied to minimize the groundwater infiltration.
5.7.24
In case seepage of groundwater occurs, groundwater should be pumped out
from works areas and discharged to the drainage system via silt trap.
Groundwater from dewatering process should also be discharged to the storm
system via silt removal facilities.
Culvert Modification
Works
5.7.25
Precaution measures shall be implemented to prevent adverse water
quality impact to the surrounding environment for culvert modification works. Good
site practices are described in ETWB TC (Works) No. 5/2005 “Protection of
natural streams/ rivers from adverse impacts arising from construction works”
and ProPECC PN 1/94 “Construction Site Drainage” should be adopted where
applicable. The following major measures shall be implemented:
·
Cofferdams and impermeable sheet piles should be installed as
appropriate to isolate the water flow from the construction works area.
·
Dewatering of flow diversion shall be conducted prior to the
construction works to prevent water overflow to the surrounding area.
·
Flow diversion should be conducted in dry season as far as
practicable when the water flow is low.
·
Any excavated sediment from the culvert modification works shall
be properly stored at bunded areas away from any watercourse and covered with
tarpaulin before transporting out of the site. Detailed management of excavated
sediment will be discussed in Chapter 6.
Construction Works in
Close Proximity to Inland Water
5.7.26
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 minimize 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:
·
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 watercourses when carrying out of the construction works.
·
Stockpilling of construction materials and dusty materials should
be covered and located away from any watercourses.
·
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.
·
Construction works close to the inland watercourses should be
carried out in dry season as far as practicable where the flow in the surface
channel or stream is low.
Groundwater from
Contaminated Areas and Contaminated Site Runoff
5.7.27
Remediation of contaminated land should be properly conducted following
the recommendations proposed under Section 7.
Any excavated contaminated material and exposed contaminated surface should be
properly housed and covered to avoid generation of contaminated runoff. Open
stockpiling of contaminated materials should not be allowed. Any contaminated
runoff generated under the construction process should be properly collected
and diverted to wastewater treatment facilities (WTF) as necessary. The WTF
shall deploy suitable treatment processes (e.g. oil interceptor/ activated
carbon) to reduce the pollution level to an acceptable standard and remove any
prohibited substances (such as total petroleum hydrocarbon) to an undetectable
range. All treated effluent from the wastewater treatment system shall meet
the requirements as stated in TM-DSS and should be either discharged into the
foul sewers or tankered away for proper disposal.
5.7.28
No direct discharge of groundwater from contaminated areas should be
adopted. Prior to any excavation works within the potentially contaminated
areas, the baseline groundwater quality in these areas should be reviewed based
on the past relevant site investigation data and any additional groundwater
quality measurements to be performed with reference to Guidance Note for
Contaminated Land Assessment and Remediation and the review results should
be submitted to EPD for examination. If the review results indicated that the
groundwater to be generated from the excavation works would be contaminated,
this contaminated groundwater should be either properly treated or properly
recharged into the ground in compliance with the requirements of the TM-DSS. If
wastewater treatment is to be deployed for treating the contaminated
groundwater, the wastewater treatment unit shall deploy suitable treatment
process (e.g. oil interceptor/ activated carbon) to reduce the pollution level
to an acceptable standard and remove any prohibited substances (such as total
petroleum hydrocarbon) to an undetectable range. All treated effluent from the
wastewater treatment plant shall meet the requirements as stated in the TM-DSS
and should be either discharged into the foul sewers or tankered away for
proper disposal.
5.7.29
If deployment of wastewater treatment is not feasible for handling the
contaminated groundwater, groundwater recharging wells should be installed as
appropriate for recharging the contaminated groundwater back into the ground. The
recharging wells should be selected at places where the groundwater quality
will not be affected by the recharge operation as indicated in Section 2.3 of
TM-DSS. The baseline groundwater quality should be determined prior to the
selection of the recharge wells, and submit a working plan to EPD for
agreement. Pollution levels of groundwater to be recharged shall not be higher
than pollutant levels of ambient groundwater at the recharge well. Groundwater
monitoring wells should be installed near the recharge points to monitor the
effectiveness of the recharge wells and to ensure that no likelihood of
increase of groundwater level and transfer of pollutants beyond the site
boundary. Prior to recharge, free products should be removed as necessary by
installing the petrol interceptor. The Contractor should apply for a discharge
licence under the WPCO through the Regional Office of EPD for groundwater
recharge operation or discharge of treated groundwater.
Operation Phase
Surface run-off from
Road/Bridge/Viaduct
5.7.30
Best Management Practices (BMPs) for stormwater discharge are
recommended to reduce stormwater pollution arising from the Project.
Design Measures
5.7.31
Exposed surface shall be avoided within the Project Site to minimise
soil erosion. The Project Site shall be either hard paved or covered by
landscaping area and plantation where appropriate.
5.7.32
The drainage system within the Project Site should be designed to cater
for the runoff from 50 year-return-period rainstorm.
Devices / Facilities to
Control Pollution
5.7.33
Screening facilities such as standard gully grating and trash grille,
with spacing which is capable of screening large substances such as fallen
leaves and rubbish should be provided at the inlet of drainage system.
5.7.34
Road gullies with standard design and silt traps and oil interceptors
should be incorporated during the detailed design to remove particles present
in stormwater runoff.
Administrative Measures
5.7.35
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.
5.7.36
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.
Sewage effluent from
New Administration Building and Ventilation Buildings
5.7.37
All sewage generated from the administration building would be treated by
the on-site STP before discharging to the nearby road drainage system outside
Lion Rock Country Park. The on-site sewage treatment facility will be designed
generally with reference to EPD’s “Guidelines for the Design of Small Sewage
Treatment Plant”. The on-site STP is designed with capacity to handle a
peak flow of three times of ADWF (i.e. 114 m3/day) with provision of
equalization tank to store three times of ADWF for 2 hours (i.e. minimum 9.5 m3)
for the surplus flow. The on-site STP will adopt MBR with UV disinfection
technology and installed within the footprint area of the administration
building. There is a need to apply to EPD for a discharge licence for effluent
discharge from the on-site STP under the WPCO. The treated effluent of the MBR
plant will meet the effluent standards of Group D inland water as specified in TM-DSS
(see Table 5.4).
5.7.38
In addition, an emergency storage tank with 2 hours of ADWF capacity (i.e.
~3.2 m3) will also be provided for temporary storage of sewage and
the stored sewage will be tankered away if the operation of STP is anticipated
could not be resumed before all the temporary storage capacity utilized, to
avoid emergency discharge to drainage system. To further minimize the
potential emergency discharge from the on-site STP, dual or standby power supply,
standby sewage treatment units, flow sensors and alarm systems should be
provided. Level sensors connected with alarm signalizing system will also be
installed, to monitor the storage volume to avoid overflow of untreated wastewater/raw
sewage. A warning signal will be generated automatically to alert the manager
when the flow in the tank reached a pre-set level, allowing sufficient time for
arranging tanker service to tanker away excessive untreated wastewater/raw
sewage. Some spare parts such as electrical and mechanical components of the
proposed STP will also be provided in case of facilities break down /
emergency. Regular test, maintenances and replacement of membranes or
equipment are necessary to maintain a good operation condition.
5.7.39
Wastewater generated from canteen within the new administration building
will be collected and treated by grease trap before being treated at the
on-site STP.
5.7.40
All sewage generated from the new ventilation buildings at Kowloon and
Shatin portals would be treated by a septic tank with soakaway system each in
view of minimal number of tunnel operation staff is required to be stationed at
the new ventilation buildings. The design of septic tank with soakaway system
shall follow the relevant guidelines and practices as given in the ProPECC PN
5/93 “Drainage Plans subject to Comment by the EPD”. Regular
maintenance shall be provided to all components of the wastewater treatment
system, including the on-site STP, septic tank with soakaway system, grease
traps, etc. No direct discharge of sewage effluent into the inland water will
be allowed.
Wastewater generated
from washing and maintenance operation
5.7.41
Wastewater from washing and maintenance activities of ventilation system
will be collected and treated with active carbon filter before discharge to the
septic tank. All wastewater generated from washing and maintenance activities of
work vehicles at car parking area will be collected and treated by petrol
interceptor following by sedimentation tank before discharge to the on-site STP.
Regular maintenance shall be provided to all components of the wastewater
treatment system, including the on-site STP, petrol interceptor, sedimentation
tank, active carbon filter system, etc. A Licensed Chemical Contractor should
be employed to collect and dispose of spent lubrication oil generated from
vehicle maintenance activities in compliance with the Waste Disposal Ordinance.
No direct discharge of these wastewaters into the inland water will be allowed.
Tunnel run-off and
drainage
5.7.42
Mitigation measures are required to mitigate tunnel run-off during the
operation phase as illustrated in follow:
·
Road drainage channels discharge should pass through oil/grit
interceptors/chambers to remove oil, grease and sediment before discharging
into the public storm drainage 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.
5.8.1
According to Section 2, “Relocation
of Diamond Hill Fresh Water and Salt Water Service Reservoirs to Cavern” and “Proposed
Drainage Improvement Works at Chui Tin Street and Chui Tin Street Soccer Pitch”
would be constructed concurrently with the Project and “Revised Trunk Road T4”
and “In-situ Reprovisioning of Sha Tin Water Treatment Works – South Works”
would also be operated in conjunction with the Project.
Construction Phase
5.8.2
The construction phase of “Relocation of Diamond Hill Fresh Water and
Salt Water Service Reservoirs to Cavern” will overlap with that of the Project
during 2025 to 2027. According to the Project Profile, potential water quality
impact may arise due to construction site runoff and drainage from works areas,
wastewater from general construction activities, sewage generated by
construction workforce, accidental spillage of chemicals, construction works in
close proximity of inland watercourses and potential groundwater infiltration.
With proper adoption of mitigation measures and good site practices, potential
water quality impact would be minimized. No unacceptable water quality impact is
expected.
5.8.3
The construction phase of the “Proposed Drainage Improvement Works at
Chui Tin Street and Chui Tin Street Soccer Pitch” will also overlap with the
Project during 2025 to 2031. The drainage improvement works would involve
land-based construction only and the potential water quality impacts would include
construction site runoff and drainage from works areas, wastewater from general
construction activities, sewage generated by construction workforce and
accidental spillage. With proper implementation of good site practices and
mitigation measures such as guidelines as given in ProPECC PN 1/94, potential
water quality impact would be minimized. No unacceptable water quality impact is
expected.
5.8.4
As no significant water quality impact was expected from the Project, “Relocation
of Diamond Hill Fresh Water and Salt Water Service Reservoirs to Cavern” and
the “Proposed Drainage Improvement Works at Chui Tin Street and Chui Tin Street
Soccer Pitch” during construction phase, adverse cumulative water quality
impact is hence not anticipated.
Operation Phase
5.8.5
“In-situ Reprovisioning of Sha Tin Water Treatment Works – South Works”
would operate in concurrent with the Project. According to the approved EIA
report (AEIAR-187/2015), no washwater effluent from cleansing of the treatment
works components would be discharged off-site. Standby treatment facilities
and dual power supply will be provided to minimize the occurrence of overflow.
No adverse water quality impact would be expected.
5.8.6
For the operation of “Revised Trunk Road T4”, major sources of water
quality impacts were expected to be paved area runoff and potential
hydrodynamic and water quality impact on Shing Mun River due to the
installation of permanent structures. Based on the EIA Report for “Revised
Trunk Road T4”, no unacceptable water quality impact is expected if the
recommended mitigation measures are properly implemented.
5.8.7
As neither the Project nor the concurrent projects were anticipated to
generate significant water quality impact during operation phase, adverse
cumulative impacts were hence not anticipated.
5.9.1
With implementation of the recommended mitigation measures for the
construction and operation phases of the Project, no adverse residual impacts
on water quality are anticipated.
5.10.1
With proper implementation of the recommended mitigation measures,
unacceptable water quality impacts at the identified WSRs are not expected. Nevertheless,
a water quality monitoring programme is recommended to ensure compliance with
the assessment criteria.
5.10.2
Detailed approach and methodology of the water quality monitoring
programme are presented in the Environmental Monitoring and Audit Manual
(EM&A Manual) under a separate cover and are briefly described below.
Construction Phase
5.10.3
Baseline monitoring should be undertaken for three times per week for a
period of at least four weeks before commencement of the construction works to
establish baseline water quality conditions of the area. Impact monitoring
should be undertaken for three times per week during the construction period to
obtain water quality data of the area throughout the construction period for
comparison with the baseline water quality data and hence determine any water
quality impacts from the construction activities. Post Project monitoring
should also be undertaken three times per week for four weeks after the
completion of construction works. The interval between 2 sets of monitoring
shall not be less than 36 hours.
5.10.4
The following parameters will be monitored under the water quality
monitoring programme:
·
pH
(in situ measurement);
·
Water
temperature (0C) (in situ measurement);
·
Salinity
(ppt) (in situ measurement);
·
Dissolved
Oxygen (DO) (% saturation and mg L-1) (in situ measurement);
·
Turbidity
(NTU) (in situ measurement); and
·
Suspended
Solids (SS) (mg L-1) (laboratory analysis).
5.10.5
Weekly site inspections and audits will be conducted to ensure that the
recommended mitigation measures are properly implemented during the
construction stage.
Operation Phase
5.10.6
Unacceptable water quality impacts are not expected during the operation
of the Project. Therefore, environmental monitoring and audit for water quality
is not recommended for the operation phase of the Project.