·
Annex 6 - Criteria for Evaluating Water Pollution and Annex 14 -
Guidelines for Assessment of Water Pollution of the “Technical Memorandum on Environmental
Impact Assessment Process” (EIAO -TM);
·
ETWB Technical Circular (Works) No. 5/2005 Protection of Natural
Streams/Rivers from Adverse Impacts Arising from Construction Works;
·
Hong Kong Planning Standards and Guidelines (HKPSG);
·
Technical Memorandum on Standards for Effluents Discharged into Drainage
and Sewerage Systems, Inland and Coastal Waters (TM-DSS);
·
Water Pollution Control Ordinance (WPCO) (Cap.358);
·
Practice Note for Professional Persons on Construction Site Drainage (ProPECC PN 1/94); and
·
Practice Note for Professional Persons on Drainage Plans (ProPECC PN5/93)
Table 5.1 Summary of Water Quality Objectives for Deep Bay WCZ
|
Criteria |
Subzone |
|
|
Aesthetic appearance |
(a) Waste discharges shall cause no objectionable odours or discolouration of the
water |
Whole Zone |
|
(b) Tarry residues, floating wood, articles made
of glass, plastic, rubber or of any other substances should be absent. |
Whole Zone |
|
|
(c) Mineral oil should not be visible on the
surface. Surfactants should not give rise to a lasting foam. |
Whole Zone |
|
|
(d) There should be no recognizable sewage-derived
debris. |
Whole Zone |
|
|
(e) Floating, submerged and semi-submerged objects
of a size likely to interfere with the free movement of vessels, or cause
damage to vessels, should be absent. |
Whole Zone |
|
|
(f) Waste
discharges shall not cause the water to contain substances which settle to
form objectionable deposits. |
Whole Zone |
|
|
Bacteria |
(a) The level of Escherichia coli should not exceed
610 per 100 mL, calculated as the geometric mean of all samples collected in
one calendar year. |
Secondary Contact Recreation Subzone and
Mariculture Subzone (L.N. 455 of 1991)
|
|
(b) The level of Escherichia coli should be zero
per 100 ml, calculated as the running median of the most recent 5 consecutive
samples taken at intervals of between 7 and 21 days. (E.R. 6 of 2019) |
Yuen Long & Kam Tin (Upper) Subzone, Beas
Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground
Subzones |
|
|
(c) The level of Escherichia coli should not
exceed 1000 per 100 ml, calculated as the running median of the most recent 5
consecutive samples taken at intervals of between 7 and 21 days. (E.R. 6 of
2019) |
Yuen Long & Kam Tin (Lower) Subzone and other
inland waters |
|
|
(d) The level of Escherichia coli should not
exceed 180 per 100 mL, calculated as the geometric mean of all samples
collected from March to October inclusive in one calendar year. Samples
should be taken at least 3 times in a calendar month at intervals of between
3 and 14 days. |
Yung Long Bathing Beach Subzone (L.N. 455 of
1991) |
|
|
Colour |
(a) Waste discharges shall not cause the colour of water to exceed 30 Hazen units. |
Yuen Long & Kam Tin (Upper) Subzone, Beas
Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground
Subzones |
|
(b) Waste discharges shall not cause the colour of water to exceed 50 Hazen units. |
Yuen Long & Kam Tin (Lower) Subzone and other
inland waters |
|
|
Dissolved oxygen (DO) |
(a) Waste discharges shall not cause the level of
dissolved oxygen to fall below 4 milligrams per litre
for 90% of the sampling occasions during the year; values should be taken at 1
metre below surface. |
Inner Marine Subzone excepting Mariculture
Subzone |
|
(b) Waste discharges shall not cause the level of
dissolved oxygen to fall below 4 milligrams per litre
for 90% of the sampling occasions during the year; values should be calculated
as water column average (arithmetic mean of at least 2 measurements at 1 metre below surface and 1 metre
above seabed). In addition, the concentration of dissolved oxygen should not
be less than 2 milligrams per litre within 2 metres of the seabed for 90% of the sampling occasions
during the year. |
Outer Marine Subzone excepting Mariculture
Subzone |
|
|
(c) The dissolved oxygen level should not be less
than 5 milligrams per litre for 90% of the sampling
occasions during the year; values should be taken at 1 metre
below surface. |
Mariculture Subzone |
|
|
(d) Waste discharges shall not cause the level of
dissolved oxygen to be less than 4 milligrams per litre. |
Yuen Long & Kam Tin (Upper and Lower)
Subzones, Beas Subzone, Indus Subzone, Ganges Subzone, Water Gathering Ground
Subzones and other inland waters of the Zone |
|
|
pH |
(a) The pH of the water should be within the range
of 6.5-8.5 units. In addition, waste discharges shall not cause the natural
pH range to be extended by more than 0.2 units. |
Marine waters excepting Yung Long Bathing Beach
Subzone |
|
(b) Waste discharges shall not cause the pH of the
water to exceed the range of 6.5-8.5 units.
|
Yuen Long & Kam Tin (Upper and Lower)
Subzones, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering
Ground Subzones |
|
|
(c) The pH of the water should be within the range
of 6.0- 9.0 units. |
Other inland waters |
|
|
(d) The pH of the water should be within the range
of 6.0- 9.0 units for 95% of samples. In addition, waste discharges shall not
cause the natural pH range to be extended by more than 0.5 units. |
Yung Long Bathing Beach Subzone |
|
|
Temperature
|
Waste discharges shall not cause the natural
daily |
Whole Zone |
|
Salinity |
Waste discharges shall not cause the natural
ambient |
Whole Zone |
|
Suspended solids (SS) |
(a) Waste discharges shall neither cause the
natural ambient level to be raised by 30% nor give rise to accumulation of
suspended solids which may adversely affect aquatic communities. |
Marine waters
|
|
(b) Waste discharges shall not cause the annual
median of suspended solids to exceed 20 milligrams per litre. |
Yuen Long & Kam Tin (Upper and Lower)
Subzones, Beas Subzone, Ganges Subzone, Indus Subzone, Water Gathering Ground
Subzones and other inland waters |
|
|
Ammonia |
The un-ionised
ammoniacal nitrogen level should not be more than 0.021 milligram per litre, calculated as the annual average (arithmetic
mean). |
Whole Zone |
|
Nutrients |
(a) Nutrients shall not be present in quantities
sufficient to |
Inner and Outer Marine Subzones |
|
(b) Without limiting the generality of objective
(a) above, the level of inorganic nitrogen should not exceed 0.7 milligram
per litre, expressed as annual mean. |
Inner Marine Subzone |
|
|
(c) Without limiting the generality of objective
(a) above, the level of inorganic nitrogen should not exceed 0.5 milligram
per litre, expressed as annual water column average
(arithmetic mean of at least 2 measurements at 1 metre
below surface and 1 metre above seabed). |
Outer Marine Subzones |
|
|
5-day biochemical oxygen demand (BOD) |
(a) Waste discharges shall not cause the 5-day
biochemical oxygen demand to exceed 3 milligrams per litre. |
Yuen Long & Kam Tin (Upper) Subzone, Beas
Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground
Subzones |
|
(b) Waste discharges shall not cause the 5-day
biochemical oxygen demand to exceed 5 milligrams per litre. |
Yuen Long & Kam Tin (Lower) Subzone and other
inland waters |
|
|
Chemical oxygen demand (COD) |
(a) Waste discharges shall not cause the chemical
oxygen demand to exceed 15 milligrams per litre. |
Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges
Subzone and Water Gathering Ground Subzones
|
|
(b) Waste discharges shall not cause the chemical
oxygen demand to exceed 30 milligrams per litre. |
Yuen Long & Kam Tin (Lower) Subzone and other
inland waters |
|
|
Toxins |
(a) Waste discharges shall not cause the toxins in
water to attain such levels as to produce significant toxic carcinogenic, mutagenic or teratogenic effects in humans, fish or any
other aquatic organisms, with due regard to biologically cumulative effects
in food chains and to toxicant interactions with each other. |
Whole Zone |
|
(b) Waste discharges shall not cause a risk to any
beneficial uses of the aquatic environment.
|
Whole Zone |
|
|
Phenol |
Phenols shall not be present in such quantities as
to produce a specific odour, or in concentration
greater than 0.05 milligrams per litre as C6H5OH. |
Yung Long Bathing Beach Subzone |
|
Waste discharges shall
not reduce light transmission |
Yung Long Bathing Beach
Subzone |
Table 5.2
Summary of Water Quality Objectives for North Western
WCZ
|
Parameters |
Criteria |
Subzone |
|
|||
|
Aesthetic appearance |
(a) Waste discharges shall cause no objectionable odours
or discolouration of the water |
Whole Zone |
|
|||
|
(b) Tarry residues, floating wood, articles made of glass, plastic,
rubber or of any other substances should be absent. |
Whole Zone |
|
||||
|
(c) Mineral oil should not be visible on the surface. Surfactants
should not give rise to a lasting foam.
|
Whole Zone |
|
||||
|
(d) There should be no recognisable
sewage-derived debris. |
Whole Zone |
|
||||
|
(e) Floating, submerged and semi-submerged objects of a size likely to
interfere with the free movement of vessels, or cause damage to vessels,
should be absent. |
Whole Zone |
|
||||
|
(f) Waste discharges shall not cause the water to contain substances
which settle to form objectionable deposits.
|
Whole Zone |
|
||||
|
Colour |
(a) Waste discharges shall not cause the colour
of water to exceed 30 Hazen units. |
Tuen Mun (A) and Tuen Mun
(B) Subzones and Water Gathering Ground Subzones |
|
|||
|
(b) Waste discharges shall not cause the colour
of water to exceed 50 Hazen units. |
Tuen Mun (C) Subzone and other
inland waters |
|
||||
|
Bacteria |
(a) The level of Escherichia coli should not exceed 610 per 100 mL,
calculated as the geometric mean of all samples collected in one calendar
year. |
Secondary Contact
Recreation Subzones |
|
|||
|
(b) The level of Escherichia coli should be less than 1 per 100 ml, calculated
as the running median of the most recent 5 consecutive samples taken at
intervals of between 7 and 21 days. |
Tuen Mun (A) and Tuen Mun (B) Subzones and Water
Gathering Ground Subzones |
|
||||
|
(c) The level of Escherichia coli should not exceed 1000 per 100 ml,
calculated as the running median of the most recent 5 consecutive samples
taken at intervals of between 7 and 21 days.
|
Tuen Mun (C) Subzone
and other inland waters |
|
||||
|
(d) The level of Escherichia coli should not exceed 180 per 100 mL,
calculated as the geometric mean of all samples collected from March to
October inclusive in one calendar year. Samples should be taken at least 3
times in a calendar month at intervals of between 3 and 14 days. |
Bathing Beach Subzones |
|
||||
|
Dissolved oxygen (DO) |
(a) Waste discharges
shall not cause the level of dissolved oxygen to fall below 4 mg per litre for 90% of the sampling occasions during the whole
year; values should be calculated as water column average (arithmetic mean of
at least 3 measurements at 1m below surface, mid-depth and 1m above seabed).
In addition, the concentration of dissolved oxygen should not be less than
2mg per litre within 2m of the seabed for 90% of
the sampling occasions during the whole year.
|
Marine Waters |
|
|||
|
(b) Waste discharges
shall not cause the level of dissolved oxygen to be less than 4 mg per litre. |
Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones, Water Gathering
Ground Subzones and other inland waters |
|
||||
|
Temperature
|
Waste discharges shall not cause the natural daily temperature range to
change by more than 2.0 degrees Celsius.
|
Whole Zone |
|
|||
|
Salinity |
Waste discharges shall not cause the natural ambient salinity level to
change by more than 10%. |
Whole Zone |
|
|||
|
pH |
(a) The pH of the water should be within the range of 6.5-8.5 units. In
addition, waste discharges shall not cause the natural pH range to be
extended by more than 0.2 units. |
Marine waters
excepting Bathing Beach Subzones |
|
|||
|
(b) Waste discharges shall not cause the pH of the water to exceed the
range of 6.5-8.5 units. |
Tuen Mun (A), Tuen Mun (B) and
Tuen Mun (C) Subzones and
Water Gathering Ground Subzones |
|
||||
|
(c) The pH of the water should be within the range of 6.0- 9.0
units. |
Other inland
waters |
|
||||
|
(d) The pH of the water should be within the range of 6.0- 9.0 units for
95% of samples collected during the whole year. In addition, waste discharges
shall not cause the natural pH range to be extended by more than 0.5
units. |
Bathing Beach
Subzone |
|
||||
|
Suspended solids (SS) |
(a) Waste discharges shall neither cause the natural ambient level to
be raised by 30% nor give rise to accumulation of suspended solids which may
adversely affect aquatic communities. |
Marine waters |
|
|||
|
(b) Waste discharges shall not cause the annual median of suspended
solids to exceed 20 mg per litre. |
Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water
Gathering Ground Subzones |
|
||||
|
(c) Waste discharges shall not
cause the annual median of suspended solids to exceed 25 mg per litre. |
Other Inland waters |
|
||||
|
Ammonia |
The un-ionised ammoniacal nitrogen level
should not be more than 0.021 milligram per litre,
calculated as the annual average (arithmetic mean). |
Whole Zone |
|
|||
|
Nutrients |
(a) Nutrients shall not be present in quantities sufficient to |
Marine waters |
|
|||
|
(b) Without limiting the generality of objective (a) above, the level
of inorganic nitrogen should not exceed 0.3 mg per litre,
expressed as annual water column average (arithmetic mean of at least 3
measurements at 1 m below surface, mid-depth and 1 m
above seabed). |
Castle Peak Bay Subzone |
|
||||
|
(c) Without limiting the generality of objective (a) above, the level
of inorganic nitrogen should not exceed 0.5 mg per litre,
expressed as annual water column average (arithmetic mean of at least 3
measurements at 1m below surface, mid-depth and 1m above seabed). |
Marine waters excepting Castle Peak Bay Subzone |
|
||||
|
5-day biochemical oxygen demand (BOD) |
(a) Waste discharges shall not cause the 5-day biochemical oxygen
demand to exceed 3 mg per litre. |
Tuen Mun (A), Tuen
Mun (B) and Tuen Mun (C) subzones and Water Gathering Ground Subzones
|
|
|||
|
(b) Waste discharges shall not cause the 5-day biochemical oxygen
demand to exceed 5 mg per litre. |
Other inland waters |
|
||||
|
Chemical oxygen demand (COD) |
(a) Waste discharges shall not cause the chemical oxygen demand to
exceed 15 mg per litre. |
Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) subzones and Water Gathering Ground Subzones |
|
|||
|
(b) Waste discharges shall not cause the chemical oxygen demand to
exceed 30 mg per litre. |
Other Inland waters |
|
||||
|
Toxins |
(a) Waste discharges shall not cause the toxins in water to attain such
levels as to produce significant toxic, carcinogenic, mutagenic
or teratogenic effects in humans, fish or any other aquatic organisms, with
due regard to biologically cumulative effects in food chains and to toxicant
interactions with each other. |
Whole Zone |
|
|||
|
(b) Waste discharges shall not cause a risk to any beneficial uses of
the aquatic environment. |
Whole Zone |
|
||||
|
Phenol |
Phenols shall not be present in such quantities as to produce a
specific odour, or in concentration greater than
0.05 mg per litre as C6H5OH. |
Bathing Beach
Subzone |
|
|||
|
Turbidity |
Waste discharges shall not reduce light transmission substantially from
the normal level. |
Bathing Beach
Subzone |
|||
Besides
setting the WQOs, the WPCO controls effluent discharging into the WCZs through
a licensing system. Guidance on the permissible effluent discharges based on
the type of receiving waters (foul sewers, stormwater drains, inland and
coastal waters) is provided in the WPCO-TM. The limits given in the WPCO-TM
cover the physical, chemical and microbial quality of
effluents. Any effluent discharge during the construction and operation stages
should comply with the relevant standards as stipulated in the WPCO-TM.
The
HKPSG, Chapter 9 – Environment, provides additional guidelines against water
pollution for sensitive uses such as aquacultural and fisheries zones, bathing
waters and other contact recreational facilities.
Practice
Note for Professional Persons on Construction Site Drainage (ProPECC PN 1/94) provides practice
guidelines for dealing with various types of discharge from a construction
site. Practices outlined in ProPECC PN 1/94 should be
followed as far as possible during construction to minimise the water quality
impact due to construction site drainage.
Practice
Note for Professional Persons on Drainage Plans (ProPECC PN5/93) provides practice
guidelines 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 PN5/93.
The
ETWB TC(W) No. 5/2005 on Protection of Natural Streams / Rivers from Adverse
Impacts Arising from Construction Works issued by the Development Bureau
provides an administrative framework to better protect all natural
streams/rivers from the impacts of construction works. The procedures
promulgated under this Technical 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 would be followed as far as
possible to protect the inland watercourses at or near the Project area during
the construction phase.
Table 5.3 Summary of water quality
statistics for the Deep Bay WCZ in 2022
|
Parameter |
Inner Deep Bay |
Outer Deep Bay |
|||
|
DM1 |
DM2 |
DM3 |
DM4 |
DM5 |
|
|
Temperature (°C) |
24.8 (17.9 - 32.4) |
25.0 (18.0 - 32.1) |
24.9 (18.9 - 31.0) |
25.0 (18.5 - 30.6) |
24.5 (18.4 - 29.9) |
|
Salinity |
14.9 (0.5 - 23.3) |
17.0 (0.4 - 25.8) |
21.6 (5.4 - 29.1) |
23.2 (8.0 - 31.2) |
25.2 (9.0 - 32.7) |
|
Dissolved Oxygen (mg/L) |
6.5 (4.9 - 9.2) |
6.0 (4.9 - 7.8) |
6.0 (4.8 - 6.9) |
5.9 (4.7 - 7.0) |
5.8 (5.0 - 6.7) |
|
Bottom |
N/A N/A |
N/A N/A |
N/A N/A |
5.7 |
5.8 |
|
(4.1 - 7.4) |
(4.7 - 7.2) |
||||
|
Dissolved Oxygen (%
Saturation) |
85 |
80 |
82 |
80 |
80 |
|
(63 - 123) |
(66 - 111) |
(71 - 94) |
(67 - 94) |
(71 - 90) |
|
|
Bottom |
N/A |
N/A |
N/A |
79 |
80 |
|
N/A |
N/A |
N/A |
(57 - 99) |
(67 - 92) |
|
|
pH |
7.4 |
7.4 |
7.5 |
7.5 |
7.6 |
|
(7.0 - 8.5) |
(6.9 - 8.3) |
(7.1 - 7.9) |
(7.1 - 7.9) |
(7.1 - 8.0) |
|
|
Secchi Disc Depth (m) |
1.1 |
1.2 |
1.5 |
1.9 |
1.9 |
|
(0.9 - 1.6) |
(0.9 - 1.5) |
(1.2 - 2.2) |
(1.2 - 2.9) |
(1.7 - 2.7) |
|
|
Turbidity (NTU) |
85.9 |
90.0 |
46.0 |
32.3 |
23.4 |
|
(9.9 - 288.0) |
(9.4 - 384.0) |
(1.8 - 264.0) |
(5.4 - 144.0) |
(4.0 - 78.1) |
|
|
Suspended Solids (mg/L) |
27.6 |
26.2 |
9.3 |
7.4 |
5.2 |
|
(7.0 - 58.0) |
(4.7 - 65.0) |
(2.6 - 22.0) |
(3.2 - 14.0) |
(3.3 - 9.7) |
|
|
5-day Biochemical Oxygen
Demand (mg/L) |
1.8 |
1.5 |
0.8 |
0.7 |
0.9 |
|
(<0.1 - 6.0) |
(0.4 - 3.2) |
(0.2 - 3.5) |
(<0.1 - 3.3) |
(0.1 - 2.9) |
|
|
Ammonia Nitrogen (mg/L) |
0.538 |
0.379 |
0.182 |
0.127 |
0.098 |
|
(0.088 - 1.200) |
(0.050 - 1.400) |
(0.024 - 0.420) |
(0.038 - 0.200) |
(0.009 - 0.190) |
|
|
Unionised Ammonia (mg/L) |
0.008 |
0.007 |
0.003 |
0.002 |
0.002 |
|
(0.002 - 0.024) |
(<0.001 - 0.043) |
(<0.001 - 0.011) |
(<0.001 - 0.007) |
(<0.001 - 0.006) |
|
|
Nitrite Nitrogen (mg/L) |
0.161 |
0.119 |
0.066 |
0.061 |
0.057 |
|
(0.094 - 0.420) |
(0.067 - 0.200) |
(0.025 - 0.130) |
(0.033 - 0.130) |
(0.020 - 0.137) |
|
|
Nitrate Nitrogen (mg/L) |
1.200 |
1.120 |
0.700 |
0.630 |
0.558 |
|
(0.840 - 1.800) |
(0.510 - 2.300) |
(0.280 - 1.200) |
(0.300 - 1.200) |
(0.140 - 1.270) |
|
|
Parameter |
Inner Deep Bay |
Outer Deep Bay |
|||
|
DM1 |
DM2 |
DM3 |
DM4 |
DM5 |
|
|
Total Inorganic Nitrogen
(mg/L) |
1.90 |
1.61 |
0.95 |
0.82 |
0.71 |
|
(1.13 - 2.61) |
(0.70 - 2.89) |
(0.41 - 1.49) |
(0.43 - 1.43) |
(0.28 - 1.41) |
|
|
Total Kjeldahl Nitrogen (mg/L) |
0.93 |
0.73 |
0.40 |
0.35 |
0.31 |
|
(0.46 - 2.10) |
(0.37 - 2.10) |
(0.19 - 0.82) |
(0.18 - 0.64) |
(0.12 - 0.88) |
|
|
Total Nitrogen (mg/L) |
2.29 |
1.96 |
1.16 |
1.04 |
0.93 |
|
(1.40 - 3.37) |
(0.95 - 3.59) |
(0.51 - 1.85) |
(0.56 - 1.61) |
(0.44 - 1.56) |
|
|
Orthophosphate
Phosphorus (mg/L) |
0.120 |
0.100 |
0.059 |
0.029 |
0.016 |
|
(0.018 - 0.180) |
(0.014 - 0.130) |
(<0.002 - 0.160) |
(<0.002 - 0.073) |
(<0.002 - 0.038) |
|
|
Total Phosphorus (mg/L) |
0.26 |
0.22 |
0.12 |
0.09 |
0.06 |
|
(0.16 - 0.41) |
(0.13 - 0.35) |
(0.05 - 0.21) |
(0.04 - 0.13) |
(0.03 - 0.10) |
|
|
Silica (as SiO_{2} ) (mg/L) |
5.74 |
5.17 |
3.74 |
3.57 |
3.00 |
|
(1.70 - 8.90) |
(0.96 - 11.00) |
(1.30 - 7.40) |
(0.99 - 7.50) |
(0.86 - 8.10) |
|
|
Chlorophyll-a (µg/L) |
8.8 |
8.9 |
3.0 |
1.9 |
2.0 |
|
(2.1 - 45.0) |
(2.1 - 33.0) |
(0.8 - 7.5) |
(0.5 - 5.2) |
(0.5 - 5.9) |
|
|
E.coli(count/100mL) |
500 |
170 |
32 |
17 |
20 |
|
(31 - 4900) |
(3 - 10000) |
(<1 - 430) |
(<1 - 250) |
(2 - 940) |
|
|
Faecal Coliforms (count/100mL) |
1200 |
430 |
53 |
35 |
43 |
|
(88 - 24000) |
(9 - 18000) |
(<1 - 900) |
(1 - 760) |
(2 - 1900) |
|
Note: 1. Unless otherwise specified, data
presented are depth-averaged (A) values calculated by taking the means of three
depths: Surface(S), Mid-depth(M), Bottom(B).
2. Data presented are annual arithmetic means
of the depth-averaged results except for E.coli and
faecal coliforms which are annual geometric means.
3. Data in brackets indicate the ranges.
4. N/A (Not Applicable) indicates the measurement was not made due to shallow
water.
5. During the periods of the special work arrangement under the COVID-19
pandemic in 2022, marine water quality monitoring frequency was adjusted and
sampling at representative monitoring stations were maintained. Full scale monitoring was conducted in the
periods of February to December 2022.
Table
5.4 Summary of water quality statistics for the North Western
WCZ in 2022
|
Parameter |
Lantau Island (North) |
Pearl Island |
Pillar Point |
Urmston Road |
Chek Lap Kok (North) |
Chek Lap Kok (West) |
|
NM1 |
NM2 |
NM3 |
NM5 |
NM6 |
NM8 |
|
|
Temperature (°C) |
23.9 |
24.5 |
24.4 |
24.5 |
24.5 |
24.4 |
|
(16.0 - 29.0) |
(16.0 - 29.1) |
(18.2 - 29.2) |
(15.9 - 29.4) |
(15.3 - 29.3) |
(15.3 - 29.1) |
|
|
Salinity |
30.0 |
28.0 |
28.1 |
27.3 |
25.7 |
27.5 |
|
(22.8 - 33.5) |
(15.4 - 33.4) |
(17.3 - 33.4) |
(19.7 - 33.1) |
(10.8 - 33.2) |
(13.2 - 33.9) |
|
|
Dissolved Oxygen (mg/L) |
5.3 |
5.6 |
5.6 |
5.5 |
5.7 |
5.8 |
|
(4.0 - 6.8) |
(4.3 - 6.7) |
(4.2 - 6.9) |
(4.1 - 6.8) |
(4.2 - 7.3) |
(4.6 - 7.1) |
|
|
Bottom |
5.1 |
5.3 |
5.3 |
5.2 |
5.7 |
5.7 |
|
(3.0 - 7.1) |
(3.9 - 7.0) |
(3.6 - 7.0) |
(3.5 - 7.0) |
(4.1 - 7.5) |
(3.0 - 7.4) |
|
|
Dissolved Oxygen (%
Saturation) |
74 |
78 |
77 |
77 |
79 |
80 |
|
(58 - 89) |
(63 - 95) |
(61 - 89) |
(56 - 86) |
(61 - 88) |
(62 - 91) |
|
|
Bottom |
72 |
75 |
75 |
73 |
79 |
80 |
|
(43 - 88) |
(55 - 92) |
(53 - 89) |
(51 - 87) |
(58 - 90) |
(43 - 91) |
|
|
pH |
7.6 |
7.6 |
7.6 |
7.6 |
7.5 |
7.6 |
|
(7.2 - 8.0) |
(7.1 - 8.1) |
(7.2 - 8.0) |
(7.1 - 8.0) |
(7.1 - 8.0) |
(7.2 - 8.0) |
|
|
Secchi Disc Depth (m) |
2.4 |
2.2 |
1.9 |
1.9 |
1.9 |
1.6 |
|
(1.9 - 3.6) |
(1.7 - 3.1) |
(1.1 - 2.6) |
(1.2 - 2.7) |
(1.2 - 2.7) |
(0.9 - 2.2) |
|
|
Turbidity (NTU) |
18.6 |
17.7 |
28.7 |
32.8 |
28.9 |
43.6 |
|
(4.1 - 83.8) |
(4.4 - 50.7) |
(4.4 - 139.0) |
(4.1 - 120.0) |
(4.1 - 105.0) |
(4.3 - 206.0) |
|
|
Suspended Solids (mg/L) |
6.0 |
5.4 |
7.0 |
10.4 |
7.7 |
11.4 |
|
(1.8 - 11.3) |
(2.1 - 7.8) |
(2.1 - 11.8) |
(2.6 - 30.0) |
(2.0 - 16.7) |
(3.5 - 25.0) |
|
|
5-day Biochemical Oxygen
Demand (mg/L) |
0.4 |
0.4 |
0.5 |
0.5 |
0.4 |
0.4 |
|
(<0.1 - 0.9) |
(<0.1 - 1.0) |
(<0.1 - 0.9) |
(<0.1 - 0.9) |
(<0.1 - 1.0) |
(<0.1 - 0.9) |
|
|
Ammonia Nitrogen (mg/L) |
0.106 |
0.094 |
0.104 |
0.094 |
0.078 |
0.047 |
|
(0.018 - 0.193) |
(0.033 - 0.170) |
(0.029 - 0.167) |
(0.034- 0.177) |
(0.020 - 0.157) |
(0.012 - 0.099) |
|
|
Unionised Ammonia (mg/L) |
0.002 |
0.002 |
0.002 |
0.002 |
0.001 |
0.001 |
|
(<0.001-0.004) |
(<0.001- 0.004) |
(<0.001-0.007) |
(<0.001-0.005) |
(<0.001-0.005) |
(<0.001-0.005) |
|
|
Nitrite Nitrogen (mg/L) |
0.037 |
0.047 |
0.055 |
0.057 |
0.059 |
0.043 |
|
(0.007 - 0.091) |
(0.006 - 0.107) |
(0.008 - 0.117) |
(0.011 - 0.120) |
(0.015 - 0.127) |
(0.006 - 0.079) |
|
|
Nitrate Nitrogen (mg/L) |
0.236 |
0.327 |
0.360 |
0.356 |
0.421 |
0.332 |
|
(0.057 - 0.740) |
(0.059 - 1.070) |
(0.069 - 1.200) |
(0.066 - 0.917) |
(0.109 - 1.270) |
(0.046 - 1.230) |
|
Parameter |
Lantau Island (North) |
Pearl Island |
Pillar Point |
Urmston Road |
Chek Lap Kok (North) |
Chek Lap Kok (West) |
|
NM1 |
NM2 |
NM3 |
NM5 |
NM6 |
NM8 |
|
|
Total Inorganic Nitrogen
(mg/L) |
0.38 |
0.47 |
0.52 |
0.51 |
0.56 |
0.42 |
|
(0.15 - 0.83) |
(0.18 - 1.17) |
(0.20 - 1.30) |
(0.20 - 1.02) |
(0.23 - 1.36) |
(0.10 - 1.32) |
|
|
Total Kjeldahl Nitrogen (mg/L) |
0.40 |
0.40 |
0.31 |
0.39 |
0.34 |
0.34 |
|
(0.10 - 1.20) |
(0.11 - 1.27) |
(0.13 - 0.79) |
(0.13 - 1.15) |
(0.13 - 0.89) |
(0.09 - 1.00) |
|
|
Total Nitrogen (mg/L) |
0.67 |
0.78 |
0.73 |
0.81 |
0.82 |
0.72 |
|
(0.26 - 1.29) |
(0.31 - 1.35) |
(0.37 - 1.40) |
(0.42 - 1.23) |
(0.47 - 1.51) |
(0.38 - 1.42) |
|
|
Orthophosphate
Phosphorus (mg/L) |
0.014 |
0.013 |
0.013 |
0.016 |
0.012 |
0.008 |
|
(0.005 - 0.031) |
(<0.002 - 0.033) |
(<0.002 - 0.032) |
(0.005 - 0.038) |
(<0.002 - 0.032) |
(<0.002 - 0.019) |
|
|
Total Phosphorus (mg/L) |
0.06 |
0.06 |
0.06 |
0.06 |
0.06 |
0.06 |
|
(0.03 - 0.10) |
(0.03 - 0.09) |
(0.03 - 0.13) |
(0.04 - 0.10) |
(0.03 - 0.08) |
(0.02 - 0.10) |
|
|
Silica (as SiO_{2} ) (mg/L) |
1.58 |
2.13 |
2.27 |
2.24 |
2.61 |
2.20 |
|
(0.28 - 4.40) |
(0.54 - 6.57) |
(0.66 - 7.60) |
(0.72 - 5.47) |
(0.78 - 8.03) |
(0.60 - 7.43) |
|
|
Chlorophyll-a (µg/L) |
1.4 |
1.7 |
1.4 |
1.4 |
1.6 |
2.3 |
|
(0.3 - 4.0) |
(0.4 - 5.5) |
(0.5 - 3.6) |
(0.5 - 3.4) |
(0.4 - 5.3) |
(0.9 - 9.7) |
|
|
E.coli(count/100mL) |
640 |
83 |
42 |
41 |
16 |
4 |
|
(29 - 4700) |
(4 - 720) |
(5 - 370) |
(4 - 770) |
(3 - 390) |
(1 - 250) |
|
|
Faecal Coliforms
(count/100mL) |
1300 |
170 |
96 |
89 |
40 |
8 |
|
(46 - 11000) |
(12 - 1500) |
(18 - 1700) |
(8 - 1400) |
(3 - 1100) |
(1 - 940) |
Note: 1. Unless otherwise specified, data
presented are depth-averaged (A) values calculated by taking the means of three
depths: Surface(S), Mid-depth(M), Bottom(B).
2. Data presented are annual arithmetic means
of the depth-averaged results except for E.coli and
faecal coliforms which are annual geometric means.
3. Data in brackets indicate the ranges.
4. During the periods of the special work arrangement under the COVID-19
pandemic in 2022, marine water quality monitoring frequency was adjusted and
sampling at representative monitoring stations were maintained.
Table 5.5 Summary of Water quality monitoring data for Tin Shui
Wai Nullah in 2022
|
Parameter |
Unit |
TSR 1 |
TSR 2 |
|
Dissolved Oxygen |
mg/L |
7.2 |
9.0 |
|
pH |
/ |
7.7 |
8.2 |
|
Suspended Solids |
mg/L |
8.2 |
4.2 |
|
5-Day Biochemical
Oxygen Demand |
mg/L |
3.6 |
1.6 |
|
Chemical Oxygen
Demand |
Mg/L |
14 |
7 |
|
Oil & Grease |
Mg/L |
<0.5 |
<0.5 |
|
E.coli |
Counts/100mL |
27 000 |
26 000 |
|
Faecal Coliforms |
Counts/100mL |
98 000 |
50 000 |
|
Ammonia-Nitrogen |
mg/L |
1.400 |
0.640 |
|
Nitrate-Nitrogen |
mg/L |
0.750 |
0.710 |
|
Total Kjeldahl Nitrogen |
Mg/L |
2.00 |
4.00 |
|
Orthophosphate
Phosphorus |
Mg/L |
0.120 |
0.014 |
|
Total Phosphorus |
Mg/L |
0.19 |
0.07 |
|
Sulphide |
Mg/L |
<0.02 |
<0.02 |
|
Aluminium |
µg/L |
60 |
51 |
|
Cadmium |
µg/L |
<0.1 |
<0.1 |
|
Chromium |
µg/L |
<1 |
<1 |
|
Copper |
µg/L |
2 |
<1 |
|
Lead |
µg/L |
<1 |
<1 |
|
Zinc |
µg/L |
<10 |
<10 |
|
Flow |
m3/s |
NM |
0.105 |
Notes: [1] Data presented are in annual
medians of monthly samples; except those for fecal
coliforms and E.coli which are in annual geometric
means.
[2] Figures in brackets are annual ranges.
[3] NM indicates no measurement taken.
[4] Values at or below laboratory reporting
limits are presented as laboratory reporting limits (see Appendix B).
[5] Equal values for annual medians (or
geometric means) and ranges indicate that all data are the same as or below
laboratory reporting limits.
Table 5.6 WSRs identified within 500m from the
project site
|
WSR(s) |
Description |
Type |
|
WSR1 |
Yuen Long Freshwater Service
Reservoir |
Reservoir |
|
WSR2 |
Hung Shui Hang Stream |
Watercourse |
|
WSR3 |
Tan Kwai Tsuen Stream |
Watercourse |
|
WSR4 |
Tan Kwai Tsuen
Saltwater Service Reservoir |
Reservoir |
|
WSR5 |
Tan Kwai Tsuen South
Freshwater Service Reservoir |
Reservoir |
|
WSR6 |
Tan Kwai Tsuen North
Freshwater Service Reservoir |
Reservoir |
|
WSR7 |
Within woodland
adjacent to Tan Kwai Tsuen Fresh Water Service Reservoir |
Abandoned Fish Pond |
|
WSR8 |
Near Sha Tseng Tsuen |
Abandoned Fish Pond |
|
WSR9 |
Near Sha Tseng Tsuen |
Abandoned Fish Pond |
|
WSR10 |
Near Sha Tseng Tsuen |
Abandoned Fish Pond |
|
WSR11 |
Near Sha Tseng Tsuen |
Abandoned Fish Pond |
|
WSR12 |
Near Sha Tseng Tsuen |
Abandoned Fish Pond |
|
WSR13 |
Tributary of Shan Pui
River (Yuen Long Creek) |
Watercourse |
|
WSR14 |
Near Fui Sha Wai |
Abandoned Fish Ponds |
|
WSR15 |
Tributary of Tin Shui
Wai Nullah |
Watercourse |
|
WSR16 |
Near Fui Sha Wai |
Inactive Fish Pond |
|
WSR17 |
Near Fui Sha Wai |
Abandoned Fish Ponds |
|
WSR18 |
Tributary
of Tuen Mun River Channel |
Watercourse |
·
Construction site runoff;
o
Run-off and
erosion of exposed bare soil and earth, drainage channels, earth working areas
and stockpiles;
o
Wash water
from dust suppression sprays and wheel washing facilities; and
o
Fuel, oil and lubricants from maintenance of construction vehicles
and equipment.
·
Construction Works in Close Proximity to Inland
Water
o Construction activities in close vicinity to the
inland water courses may impact water quality due to the potential release of
construction wastewater. Construction wastewater are generally characterized by high SS
concentration and elevated pH. The implementation of adequate construction
site drainage and Best Management Practices as described Section 5.8 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”, it is anticipated that water quality impacts would be
minimal.
·
Accidental spillage;
o The use of chemicals such as engine oil and lubricants,
and their storage as waste materials has the potential to impact water quality
if spillage occurs and enters adjacent water environment. Waste oil may infiltrate into the surface
soil layer, or runoff into the nearby water environment, increasing hydrocarbon
levels. Groundwater pollution may also arise from the improper use and storage
of chemicals and petroleum products within the site area where groundwater
infiltrates into the area. Infiltration
of groundwater may occur at area 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.
·
Sewage effluent
from the construction workforce.
o During the construction of the Project, the
workforce on site will generate sewage effluent, which is characterized by high
levels of BOD, ammonia and E.coli counts. Based on the DSD Sewerage Manual, the sewage
production rate for construction workers is estimated at 0.35m3 per
worker per day. Potential water quality impacts upon the local drainage and
freshwater system may arise from these sewage effluents, if uncontrolled
·
Standard screening designs such
as gully grating should be provided to stop large objects from entering;
·
Exposed surface shall be
avoided to minimize soil erosion.
Cumulative Impact with
Concurrent Projects
Table 5.7 Potential Concurrent Projects
|
No |
Potential Concurrent
Projects |
Tentative construction
time |
|
1 |
Environmentally Friendly Transport Services
in Hung Shui Kiu / Ha Tsuen New Development Area
and Adjacent Areas |
Phase 1: Year 2027 – 2030/31 Phase 2: Year 2032 – 2036 Phase 3: Year 2034 – 2038 |
|
2 |
Route 11 (Section between Yuen Long and
Lantau) |
No later than Year 2033 |
|
3 |
Site Formation and Infrastructure Works for
Public Housing Developments at Long Bin, Yuen Long |
Year 2020 - 2026 |
|
4 |
Site Formation and Infrastructure Works for
Public Housing Development near Tan Kwai Tsuen, Yuen Long |
Year 2022 - 2027 |
|
5 |
Yuen Long South Development |
2022 – 2038 |
|
6 |
Hung Shui Kiu / Ha
Tsuen New Development Area |
2020 – 2038 |
|
7 |
Potential Sites in Yuen Long Areas 13 &
14 for Housing Development |
Year 2025 - 2032 |
· The use of less or smaller construction plants may be specified in areas close to the water courses to reduce the disturbance to the surface water.
· Temporary storage of materials (e.g. equipment, chemicals and fuel) and temporary stockpile of construction materials should be located well away from any water courses when carrying out of the construction works.
· Stockpiling of construction materials and dusty materials should be covered and located away from any water courses.
· Construction debris and spoil should be covered up and / or disposed of as soon as possible to avoid being washed into the nearby water receivers.
· Proper shoring may need to be erected in order to prevent soil or mud from slipping into the watercourses.