HKOLNG EIA_07

Table 7.1 Summary of Water Quality Objectives for Southern WCZ, Second Southern Supplementary WCZ, North Western WCZ, North Western Supplementary WCZ, Deep Bay WCZ and Western Buffer WCZ

	Water Quality Objective	Southern WCZ	Second Southern Supplementary WCZ	North Western WCZ	North Western Supplementary WCZ	Deep Bay WCZ	Western Buffer WCZ
A	AESTHETIC APPEARANCE
a)	Waste discharges shall cause no objectionable odours or discolouration of the water.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone
b)	Tarry residues, floating wood, articles made of glass, plastic, rubber or of any other substances should be absent.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone
c)	Mineral oil should not be visible on the surface. Surfactants should not give rise to lasting foam.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone
d)	There should be no recognisable sewage-derived debris.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	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	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone
f)	Waste discharges shall not cause the water to contain substances which settle to form objectionable deposits.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone
B	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 & Fish Culture Zones	Secondary Contact Recreation Subzones	Secondary Contact Recreation Subzone	Secondary Contact Recreation Subzone	Secondary Contact Recreation Subzone and Mariculture Subzone (L.N. 455 of 1991)	Secondary Contact Recreation Subzones and Fish Culture Subzones
b)	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 (L.N. 453 of 1991)	Not applicable	Bathing Beach Subzones	Not applicable	Yung Long Bathing Beach Subzone (L.N. 455 of 1991)	Recreation Subzones
c)	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.	Not applicable	Not applicable	Tuen Mun (A) and Tuen Mun (B) Subzones and Water Gathering Ground Subzones	Not applicable	Not applicable	Water Gathering Ground Subzones
d)	The level of Escherichia coli should not exceed 1000 per 100 mL, calculated as the geometric mean of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days.	Not applicable	Not applicable	Tuen Mun (C) Subzone and other inland waters	Not applicable	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Other inland waters
e)	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.	Not applicable	Not applicable	Not applicable	Not applicable	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Not applicable
C	COLOR
a)	Waste discharges shall not cause the colour of water to exceed 30 Hazen units.	Not applicable	Not applicable	Tuen Mun (A) and Tuen Mun (B) Subzones and Water Gathering Ground Subzones	Not applicable	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Water Gathering Ground Subzones
b)	Waste discharges shall not cause the colour of water to exceed 50 Hazen units	Not applicable	Not applicable	Tuen Mun (C) Subzone and other inland waters	Not applicable	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Other inland waters
D	DISSOLVED OXYGEN
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 calculated as the water column average (arithmetic mean of at least 3 measurements at 1 metre below surface, mid-depth, 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.	Marine waters excepting Fish Culture Subzones	Whole zone	Marine waters	Whole zone	Outer Marine Subzone excepting Mariculture Subzone	Marine waters excepting Fish Culture Subzones
b)	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 calculated as water column average (arithmetic mean of at least 3 measurements at 1 metre below surface, mid-depth 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.	Fish Culture Subzones	Not applicable	Not applicable	Not applicable	Not applicable	Fish Culture Subzones
c)	Waste discharges shall not cause the level of dissolved oxygen to be less than 4 milligrams per litre.	Inland waters of the Zone	Not applicable	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones, Water Gathering Ground Subzones and other inland waters	Not applicable	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges Subzone, Water Gathering Ground Subzones and other inland waters	Water Gathering Ground Subzones and other inland waters
d)	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.	Not applicable	Not applicable	Not applicable	Not applicable	Inner Marine Subzone excepting Mari culture Subzone	Not applicable
e)	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.	Not applicable	Not applicable	Not applicable	Not applicable	Mariculture Subzone	Not applicable
E	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; Mui Wo (A), Mui Wo (B), Miu Wo (C), Mui Wo (E) and Mui Wo (F) Subzones.	Not applicable	Marine waters excepting Bathing Beach Subzones	Not applicable	Marine waters excepting Yung Long Bathing Beach Subzone	Not applicable
b)	The pH of the water should be within the range of 6.5-8.5 units. In addition, human activity should not cause the natural pH range to be extended by more than 0.2 unit.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Marine waters
c)	Waste discharges should not cause the natural pH range of the water to be extended by more than 0.2 unit. In addition, the pH of the water should be in the range of 6.5-8.5 units.	Not applicable	Whole zone	Not applicable	Whole zone	Not applicable	Not applicable
d)	The pH of the water should be within the range of 6.0-9.0 units.	Mui Wo (D) Sub-zone and other inland waters.	Not applicable	Other inland waters	Not applicable	Other inland waters	Not applicable
e)	Human activity should not cause the pH of the water to exceed the range of 6.0-9.0 units.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Other inland waters
f)	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.	Bathing Beach Subzones	Not applicable	Bathing Beach Subzones	Not applicable	Yung Long Bathing Beach Subzone	Not applicable
g)	Waste discharges shall not cause the pH of the water to exceed the range of 6.5-8.5 units.	Not applicable	Not applicable	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Not applicable	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Not applicable
h)	Human activity should not cause the pH of the water to exceed the range of 6.5-8.5 units.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Water Gathering Ground Subzones
F	TEMPERATURE
a)	Waste discharges shall not cause the natural daily temperature range to change by more than 2.0 degrees Celsius.	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Not applicable
b)	Human activity should not cause the natural daily temperature range to change by more than 2.0ºC.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Whole zone
G	SALINITY
a)	Change due to waste discharge not to exceed 10% of natural ambient level	Whole zone	Whole zone	Whole zone	Whole zone	Whole zone	Not applicable
b)	Human activity should not cause the natural ambient salinity level to change by more than 10%.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Whole zone
H	SUSPENDED SOLIDS
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	Whole zone	Marine waters	Whole zone	Marine waters	Not applicable
b)	Human activity should neither cause the natural ambient level to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Marine waters
c)	Waste discharges shall not cause the annual median of suspended solids to exceed 20 milligrams per litre.	Mui Wo (A), Mui Wo (B), Mui Wo (C), Mui Wo (E) and Mui Wo (F) Subzones.	Not applicable	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Not applicable	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Ganges Subzone, Indus Subzone, Water Gathering Ground Subzones and other inland waters	Not applicable
d)	Human activity should not cause the annual median of suspended solids to exceed 20 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Water Gathering Ground Subzones
e)	Waste discharges shall not cause the annual median of suspended solids to exceed 25 milligrams per litre.	Mui Wo (D) Sub-zone and other inland waters.	Not applicable	Other inland waters	Not applicable	Not applicable	Not applicable
f)	Human activity should not cause the annual median of suspended solids to exceed 25 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Other inland waters
I	AMMONIA
a)	The ammonia nitrogen level should not be more than 0.021 milligram per litre, calculated as the annual average (arithmetic mean), as unionised form.	Whole zone	Whole zone	Not applicable	Not applicable	Not applicable	Not applicable
b)	The un-ionized ammoniacal nitrogen level should not be more than 0.021 mg per litre, calculated as the annual average (arithmetic mean).	Not applicable	Not applicable	Whole zone	Whole zone	Whole zone	Whole zone
J	NUTRIENTS
a)	Nutrients shall not be present in quantities sufficient to cause excessive or nuisance growth of algae or other aquatic plants.	Marine waters	Whole zone	Marine waters	Whole zone	Inner and Outer Marine Subzones	Marine waters
b)	Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.1 milligram per litre, expressed as annual water column average (arithmetic mean of at least 3 measurements at 1 metre below surface, mid-depth and 1 metre above seabed).	Marine waters	Whole zone	Not applicable	Not applicable	Not applicable	Not applicable
c)	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).	Not applicable	Not applicable	Castle Peak Bay Subzone	Not applicable	Not applicable	Not applicable
d)	Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.4 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).	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Marine waters
e)	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 1 m below surface, mid-depth and 1 m above seabed).	Not applicable	Not applicable	Marine waters excepting Castle Peak Bay Subzone	Whole zone	Outer Marine Subzone	Not applicable
f)	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.	Not applicable	Not applicable	Not applicable	Not applicable	Inner Marine Subzone	Not applicable
K	5-DAY BIOCHEMICAL OXYGEN DEMAND
a)	Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 3 milligrams per litre.	Not applicable	Not applicable	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Not applicable	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Not applicable
b)	The 5-day biochemical oxygen demand should not exceed 3 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Water Gathering Ground Subzones
c)	Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 5 milligrams per litre.	Inland waters of the zone	Not applicable	Other inland waters	Not applicable	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Not applicable
d)	The 5-day biochemical oxygen demand should not exceed 5 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Other inland waters
L	CHEMICAL OXYGEN DEMAND
a)	Waste discharges shall not cause the chemical oxygen demand to exceed 15 milligrams per litre.	Not applicable	Not applicable	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Not applicable	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Not applicable
b)	The chemical oxygen demand should not exceed 15 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Water Gathering Ground Subzones
c)	Waste discharges shall not cause the chemical oxygen demand to exceed 30 milligrams per litre.	Inland waters	Not applicable	Other inland waters	Not applicable	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Not applicable
d)	The chemical oxygen demand should not exceed 30 mg per litre.	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Other inland waters
M	DANGEROUS SUBSTANCES / TOXIC SUBSTANCES / TOXINS
a)	Waste discharges shall not cause the concentrations of dangerous substances in marine waters to attain such levels as to produce significant toxic 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	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable
b)	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.	Not applicable	Whole zone	Not applicable	Whole zone	Not applicable	Whole zone
c)	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.	Not applicable	Not applicable	Whole zone	Not applicable	Whole zone	Not applicable
d)	Waste discharges of dangerous substances shall not put a risk to any beneficial uses of the aquatic environment.	Whole zone	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable
e)	Human activity should not cause a risk to any beneficial use of the aquatic environment.	Not applicable	Whole zone	Not applicable	Whole zone	Not applicable	Whole zone
f)	Waste discharges shall not cause a risk to any beneficial use of the aquatic environment.	Not applicable	Not applicable	Whole zone	Not applicable	Whole zone	Not applicable
N	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.	Not applicable	Not applicable	Bathing Beach Subzones	Not applicable	Yung Long Bathing Beach Subzone	Not applicable
O	TURBIDITY
	Waste discharges shall not reduce light transmission substantially from the normal level.	Not applicable	Not applicable	Bathing Beach Subzones	Not applicable	Yung Long Bathing Beach Subzone	Bathing Beach Subzones

Sources:

(1) CAP358I Southern Water Control Zone Statement of Water Quality Objectives. Available at: https://www.elegislation.gov.hk/hk/cap358I!en.assist.pdf

(2) CAP358BA Statement of Water Quality Objectives (Second Southern Supplementary Water Control Zone) https://www.elegislation.gov.hk/hk/cap358BA!en.assist.pdf

(3) CAP358X Statement of Water Quality Objectives (North Western Water Control Zone) https://www.elegislation.gov.hk/hk/cap358X!en.assist.pdf

(4) CAP358AZ Statement of Water Quality Objectives (North Western Supplementary Water Control Zone) https://www.elegislation.gov.hk/hk/cap358AZ!en.assist.pdf

(5) CAP358R Statement of Water Quality Objectives (Deep Bay Water Control Zone) https://www.elegislation.gov.hk/hk/cap358R!en.assist.pdf

(6) CAP358AD Statement of Water Quality Objectives (Western Buffer Water Control Zone) https://www.elegislation.gov.hk/hk/cap358AD!en.assist.pdf

Table 7.2 Summary of EPD Routine Water Quality Monitoring Data from Selected Stations of the Deep Bay WCZ, North Western WCZ and Western Buffer WCZ (1986 – 2016)

Parameter	DM3	DM4	DM5	NM3	NM5	NM6	NM8	WM1
Temperature (°C)	24.1	23.9	23.8	23.4	23.5	23.7	23.7	22.8
	(11.0-32.0)	(11.1-32.7)	(12.2-30.6)	(12.3-29.6)	(12.2-29.7)	(12.1-30.3)	(14.8-30.6)	(14.7-29.3)
Salinity (psu)	21.4	23.1	25.8	28.7	27.4	26.2	27.9	32.0
	(0.8-32.1)	(3.2-34.1)	(7.6-34.2)	(16.0-33.9)	(15.7-33.7)	(9.1-33.9)	(7.4-33.7)	(26.0-34.4)
Dissolved Oxygen	6.3	6.2	6.1	6.0	6.0	6.5	6.6	6.1
(mg L^-1)	(2.4-16.1)	(3.1-11.2)	(3.2-11.4)	(3.2-14.6)	(2.9-14.6)	(3.1-11.8)	(3.3-11.6)	(2.7-9.7)
Dissolved Oxygen	6.9	6.1	5.9	5.7	5.6	6.3	6.3	5.8
(mg L^-1) - Bottom	(2.4-16.1)	(2.4-11.1)	(2.6-11.0)	(2.2-15.6)	(2.1-15.6)	(2.4-13.4)	(0.8-11.7)	(1.6-9.8)
Suspended Solids (mg L^-1)	17.4	13.5	11.0	9.7	11.9	10.7	13.0	5.5
	(2.5-120.0)	(1.0-88.5)	(1.3-99.7)	(1.7-90.3)	(1.8-86.9)	(1.9-89.3)	(1.9-59.3)	(0.8-22.6)
5-day Biochemical	1.4	0.9	0.9	0.8	0.8	0.9	0.8	0.7
Oxygen Demand (mg L^-1)	(0.2-12.0)	(0.2-3.9)	(0.1-6.4)	(0.1-2.8)	(0.1-3.0)	(0.1-6.1)	(0.1-4.6)	(0.1-2.9)
Unionised Ammonia	0.018	0.009	0.006	0.004	0.005	0.004	0.003	0.003
(mg L^-1)	(0.001-0.553)	(0.001-0.068)	(0.001-0.045)	(0.001-0.018)	(0.001-0.019)	(0.001-0.022)	(0.001-0.019)	(0.001-0.020)
Total Inorganic Nitrogen	1.43	0.98	0.75	0.46	0.60	0.59	0.44	0.18
(mg L^-1)	(0.01-6.33)	(0.10-2.85)	(0.10-2.16)	(0.03-1.48)	(0.05-1.94)	(0.02-2.03)	(0.01-2.09)	(0.03-0.50)
Orthophosphate	0.121	0.056	0.036	0.026	0.030	0.024	0.016	0.017
Phosphorus (mg L^-1)	(0.003-0.901)	(0.003-0.190)	(0.004-0.092)	(0.002-0.056)	(0.004-0.065)	(0.002-0.063)	(0.004-0.048)	(0.004-0.079)
Total Phosphorus (mg L^-1)	0.19	0.10	0.07	0.06	0.07	0.06	0.04	0.05
	(0.05-1.50)	(0.03-1.12)	(0.03-0.42)	(0.02-0.31)	(0.02-0.33)	(0.02-0.33)	(0.02-0.13)	(0.02-0.38)
Chlorophyll-a (g L^-1)	6.2	3.3	2.6	2.8	2.8	4.1	4.4	2.6
	(0.3-180.0)	(0.3-43.0)	(0.2-42.0)	(0.3-25.0)	(0.2-25.0)	(0.3-48.0)	(0.4-44.3)	(0.2-25.3)
Escherichia coli	64	137	325	384	618	31	5	137
(cfu/100ml)	(1-19000)	(1-5190)	(2-17000)	(8-85333)	(7-11385)	(1-2287)	(1-1235)	(1-4767)

Notes:

1. Data presented are depth-averaged values calculated by taking the means of three depths, i.e. surface (S), mid-depth (M) and bottom (B), except as specified.

2. Data presented are annual arithmetic means except for E. coli, which are geometric means.

3. Shaded cells indicate non-compliance with the WQOs.

Table 7.3 Summary of EPD Routine Water Quality Monitoring Data from Selected Stations of the Southern WCZ (1986 – 2016)

Parameter	SM3	SM4	SM5	SM6	SM7	SM12	SM13	SM17	SM18	SM20
Temperature (°C)	22.9	23.2	23.5	23.2	23.4	23.6	23.6	23.3	23.1	23.6
	(14.2-28.9)	(14.3-28.8)	(14.2-29.6)	(14.0-29.4)	(14.2-29.8)	(13.7-29.4)	(13.8-29.7)	(14.1-29.9)	(14.0-29.1)	(14.0-29.8)
Salinity (psu)	32.2	31.6	31.2	31.4	30.7	30.5	30.5	31.4	31.9	30.6
	(28.2-34.5)	(24.2-34.4)	(18.8-34.3)	(22.9-34.3)	(20.0-34.4)	(14.9-34.3)	(13.9-34.4)	(23.5-34.4)	(24.9-34.3)	(15.3-34.2)
Dissolved Oxygen	6.2	6.3	6.8	6.6	6.5	7.0	7.0	6.7	6.5	6.5
(mg L-1) - Depth Average	(3.2-11.0)	(3.1-11.3)	(4.2-11.7)	(3.5-10.4)	(3.4-10.9)	(3.4-11.2)	(3.6-11.1)	(3.5-10.2)	(3.5-12.7)	(2.1-9.5)
Dissolved Oxygen	5.9	6.1	6.3	6.0	6.2	6.7	6.7	6.2	5.9	6.3
(mg L-1) - Bottom	(1.3-13.4)	(1.5-10.4)	(2.0-10.4)	(0.3-9.6)	(2.2-11.1)	(2.4-11.4)	(1.7-11.6)	(1.1-10.4)	(0.4-16.3)	(1.9-9.7)
Suspended Solids	4.9	4.0	5.6	5.3	6.5	8.5	7.3	6.1	4.9	10.4
(mg L-1)	(0.5-30.0)	(0.7-26.5)	(0.8-21.3)	(0.8-30.7)	(0.9-45.3)	(0.6-40.8)	(0.8-35.0)	(0.9-52.5)	(0.5-23.4)	(1.0-106.0)
5-day Biochemical	0.7	0.8	0.9	0.9	1.0	1.1	1.0	0.7	0.7	0.8
Oxygen Demand (mg L-1)	(0.2-3.7)	(0.1-3.5)	(0.1-3.5)	(0.1-3.7)	(0.1-4.5)	(0.1-3.5)	(0.1-3.4)	(0.1-3.0)	(0.1-3.5)	(0.1-4.5)
Unionised Ammonia	0.002	0.003	0.002	0.003	0.004	0.003	0.003	0.002	0.002	0.002
(mg L-1)	(0.001-0.032)	(0.001-0.017)	(0.001-0.018)	(0.001-0.025)	(0.001-0.016)	(0.001-0.028)	(0.001-0.021)	(0.001-0.011)	(0.001-0.014)	(0.001-0.011)
Total Inorganic Nitrogen	0.15	0.18	0.16	0.17	0.25	0.23	0.21	0.16	0.13	0.23
(mg L-1)	(0.01-0.52)	(0.02-1.04)	(0.02-0.95)	(0.01-0.87)	(0.01-1.17)	(0.02-1.31)	(0.02-1.33)	(0.01-0.65)	(0.01-0.65)	(0.02-1.25)
Orthophosphate	0.014	0.015	0.013	0.013	0.018	0.016	0.014	0.012	0.012	0.011
Phosphorus (mg L-1)	(0.003-0.039)	(0.002-0.053)	(0.003-0.102)	(0.002-0.047)	(0.002-0.040)	(0.002-0.046)	(0.002-0.041)	(0.002-0.051)	(0.002-0.034)	(0.003-0.040)
Total Phosphorus	0.04	0.04	0.04	0.04	0.046	0.046	0.045	0.043	0.041	0.036
(mg L-1)	(0.02-0.23)	(0.02-0.23)	(0.02-0.23)	(0.02-0.23)	(0.02-0.25)	(0.02-0.48)	(0.02-0.83)	(0.02-0.72)	(0.02-0.25)	(0.02-0.15)
Chlorophyll-a (µg L-1)	2.6	3.6	4.2	4.0	5.1	5.9	5.0	3.3	2.9	3.9
	(0.3-13.5)	(0.3-26.0)	(0.3-32.0)	(0.3-28.3)	(0.3-29.7)	(0.3-46.0)	(0.2-37.0)	(0.2-21.7)	(0.3-17.0)	(0.4-21.7)
Escherichia coli	37	21	2	3	14	30	5	2	2	2
(cfu/100ml)	(1-1957)	(1-6067)	(1-790)	(1-267)	(1-2887)	(1-33354)	(1-980)	(1-122)	(1-280)	(1-142)

Notes:

1. Data presented are depth-averaged values calculated by taking the means of three depths, i.e. surface (S), mid-depth (M) and bottom (B), except as specified.

2. Data presented are annual arithmetic means except for E. coli, which are geometric means.

3. Shaded cells indicate non-compliance with the WQOs.

Parameter	ST1	WT1	WT3
Temperature (°C)	24.2	23.3	23.3
	(16.9-29.7)	(15.3-28.5)	(15.2-28.6)
Salinity (psu)	29.8	30.9	30.9
	(21.8-33.2)	(25.2-33.5)	(26.7-33.4)
Dissolved Oxygen (mg L^-1)	6.8	6.1	6.0
- Depth Average	(4.9-11.8)	(3.7-9.3)	(4.1-9.2)
Dissolved Oxygen (mg L^-1)	6.7	6.2	5.9
- Bottom	(4.2-10.7)	(3.4-9.0)	(3.7-9.0)
Suspended Solids (mg L^-1)	6.4	4.6	4.4
	(1.1-23.0)	(1.0-20.7)	(1.4-21.3)
5-day Biochemical Oxygen Demand	1.1	0.8	0.9
(mg L^-1)	(0.3-2.3)	(0.2-2.0)	(0.3-2.3)
Unionised Ammonia (mg L^-1)	0.003	0.003	0.003
	(0.001-0.009)	(0.001-0.009)	(0.001-0.009)
Total Inorganic Nitrogen (mg L^-1)	0.29	0.24	0.25
	(0.11-0.63)	(0.06-0.69)	(0.08-0.58)
Orthophosphate Phosphorus	0.014	0.013	0.014
(mg L^-1)	(0.002-0.030)	(0.002-0.029)	(0.003-0.031)
Total Phosphorus (mg L^-1)	0.04	0.04	0.04
	(0.02-0.10)	(0.02-0.15)	(0.02-0.10)
Chlorophyll-a (g L^-1)	7.8	3.4	3.6
	(0.7-26.0)	(0.5-16.9)	(0.4-17.3)
Escherichia coli (cfu/100ml)	74	325	1,054
	(6-299)	(8-1,490)	(61-8,423)

Parameter	ADV-21 Guideline	DS3	DS4	NS4	NS6	SS3	SS4	SS6	WS2
Arsenic (mg kg^-1)	12	42	13.6	13.6	12.3	12.4	7.4	8.8	6.3	9.1
			(3.9-20.0)	(6.6-26.0)	(3.7-26.0)	(6.1-24.0)	(3.0-14.0)	(3.8-16.0)	(1.7-12.0)	(1.4-17.0)
Cadmium (mg kg^-1)	1.5	4	0.4	0.3	0.3	0.3	0.3	0.4	0.2	0.3
			(0.1-11.0)	(0.1-13.0)	(0.1-8.9)	(0.1-13.0)	(0.0-6.8)	(0.0-9.1)	(0.0-5.9)	(0.0-9.2)
Chromium (mg kg^-1)	80	160	39	33	31	31	31	37	23	37
			(17-53)	(14-54)	(9-68)	(15-61)	(17-62)	(25-54)	(10-48)	(23-59)
Copper (mg kg^-1)	65	110	46	29	28	21	26	38	13	38
			(11-230)	(6-65)	(5-67)	(7-84)	(1-290)	(18-76)	(4-31)	(17-140)
Lead (mg kg^-1)	75	110	50	41	41	34	38	45	27	40
			(24-79)	(18-93)	(29-82)	(16-55)	(20-190)	(25-73)	(16-55)	(22-54)
Mercury (mg kg^-1)	0.5	1	0.12	0.08	0.10	0.07	0.12	0.15	0.06	0.14
			(0.03-0.36)	(0.03-0.29)	(0.03-0.35)	(0.03-0.22)	(0.04-0.79)	(0.05-0.69)	(0.02-0.18)	(0.03-0.57)
Nickel (mg kg^-1)	40	40	25	20	18	19	21	22	15	23
			(10-37)	(7-32)	(7-40)	(8-32)	(9-35)	(11-32)	(5-29)	(13-31)
Silver (mg kg^-1)	1	2	0.4	0.2	0.2	0.2	0.2	0.3	0.2	0.4
			(0.0-1.0)	(0.0-1.0)	(0.0-0.5)	(0.0-0.5)	(0.0-0.5)	(0.0-1.0)	(0.0-0.5)	(0.0-3.0)
Zinc (mg kg^-1)	200	270	127	101	98	83	95	109	64	106
			(49-230)	(36-180)	(57-180)	(32-130)	(41-680)	(75-140)	(29-120)	(66-170)
Total Polychlorinated Biphenyls	23	180	14	15	14	14	14	15	14	15
(PCBs) (μg kg^-1)			(3-18)	(3-19)	(3-18)	(3-18)	(3-25)	(3-23)	(3-18)	(3-24)
Low Molecular Weight	550	3,160	111	113	114	109	109	110	100	114
Polycyclic Aromatic Hydrocarbons (PAHs) (μg kg-1)			(10-191)	(10-215)	(10-244)	(10-185)	(10-185)	(10-275)	(10-185)	(10-207)
High Molecular Weight	1,700	9,600	108	81	91	46	101	133	42	126
Polycyclic Aromatic Hydrocarbons (PAHs) (μg kg-1)			(22-277)	(10-381)	(11-229)	(11-163)	(22-415)	(37-301)	(12-116)	(22-1094)
Chemical Oxygen	--	--	14,394	13,656	13,255	12,696	15,342	14,502	9,279	13,792
Demand (mg kg^-1)			(7,700-32,000)	(7,400-21,000)	(5,600-19,000)	(7,400-20,000)	(9,400-28,000)	(9,600-25,000)	(4,300-18,000)	(3,900-21,000)
Total Kjeldahl Nitrogen	--	--	423	334	341	307	414	423	332	477
(mg kg^-1)			(150-2,300)	(100-1,300)	(23-810)	(74-860)	(220-960)	(92-710)	(100-780)	(260-1,800)

Table 7.7a Water Quality Sensitive Receivers in the Vicinity of the Project

Description	Location	Model Output Location	Geodesic Distance / Approximate Shortest Distance by Sea (km)
Description	Location	Model Output Location	from the Proposed Subsea Pipeline		from the Proposed LNG Terminal
Fisheries Sensitive Receivers
Spawning/ Nursery Grounds	Fisheries Spawning Ground in North Lantau	Numerous ⁽¹⁾; MPA-5, AR1, CR3	0.3 / 0.3		>10 / >10
	Fisheries Spawning/Nursery Grounds in South Lantau	Numerous; MPC-5-6, MPD-8-9, CR4, CR5, NB9-10, B8-9, MPE	0.05-0.2 / 0.05-0.2		0.2 / 0.2
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	AR1	1.0 / 1.0		>10 / >10
Fish Culture Zone	Cheung Sha Wan FCZ	FCZ1	7.0 / 7.8		9.9 / 9.9
	Lo Tik Wan FCZ	FCZ2	3.6 / 7.1		>10 / >10
	Sok Kwu Wan FCZ	FCZ3	4.0 / 9.0		>10 / >10
Oyster Production Area	Sheung Pak Nai	O1	3.6 / 3.6		>10 / >10
Marine Ecological Sensitive Receivers
Seagrass Beds	Ha Pak Nai	H1	2.2 / 2.2		>10 / >10
	Tung Chung Bay	C8	6.7 / 6.9		>10 / >10
Marine Park (MP)	Sha Chau and Lung Kwu Chau MP	MPA-5	1.0 / 1.0		>10 / >10
	Proposed AAHK 3RS MP	MPB	0.7 / 0.7		>10 / >10
	Proposed Southwest Lantau MP	MPC-7-8	0.7 / 0.7		9.4 / 9.8
	Proposed South Lantau MP	MPD-8-9	1.7 / 1.7		2.1 / 2.1
	Potential South Lamma MP	MPE	1.7 / 1.7		>10 / >10
Intertidal Mudflats / Mangroves / Horseshoe Crab Nursery Grounds	Sheung Pak Nai	H9	5.1 / 5.3		>10 / >10
	Ha Pak Nai	H1	2.2 / 2.2		>10 / >10
	Ngau Hom Shek	H8	6.6 / 6.9		>10 / >10
	Lung Kwu Sheung Tan	NB1	1.7 / 1.7		>10 / >10
	Tung Chung Bay	C8	6.7 / 6.9		>10 / >10
	Sha Lo Wan	H2	3.5 / 3.5		>10 / >10
	Sham Wat Wan	H6	3.4 / 4.5		>10 / >10
	Tai O	H3	1.4 / 1.4		>10 / >10
	Yi O	H4	1.2 / 1.2		>10 / >10
	Fan Lau Tung Wan	MPC-5, NB4	2.6 / 2.6		7.4 / 7.4
	Tong Fuk Miu Wan / Shui Hau	H5	5.2 / 5.2		6.7 / 6.7
	Pui O	B4	6.9 / 6.9		9.2 / 9.2
	Shek Kwu Chau North	H7	2.9 / 3.0		5.4 / 5.5
Corals	Artificial Seawall at BPPS	CR1, CR2	0.1 / 0.1		>10 / >10
	Pak Chau	CR3	0.3 / 0.3		>10 / >10
	Shek Kwu Chau	CR4	1.6 / 1.6		4.3 / 4.3
	Siu A Chau	CR5	4.3 / 4.3		5.5 / 5.8
	Tai A Chau	CR6	1.1 / 1.1		5.7 / 5.7
	Cheung Chau	CR7-8	4.1 / 5.0		8.9 / 11.2
	Hei Ling Chau	CR9-10	6.6 / 6.6		>10 / >10
	Sunshine Island	CR11	7.0 / 7.0		>10 / >10
	Shek Kok Tsui	CR12	2.7 / 2.7		>10 / >10
	Pak Kok	CR13	3.6 / 4.1		>10 / >10
	Sha Wan	CR14	6.6 / 6.9		>10 / >10
	Ap Lei Chau	CR15	5.3 / 7.4		>10 / >10
	Wong Chuk Kok	CR16-17	5.9 / 9.3		>10 / >10
	Sham Wan	CR18	4.7 / 4.7		>10 / >10
	Luk Chau	CR19	3.8 / 7.0		>10 / >10
	Hung Shing Yeh	CR20	1.6 / 1.9		>10 / >10
	Ha Mei Wan	CR21	1.6 / 1.6		>10 / >10
	Chi Ma Wan Peninsula	CR22	7.0 / 7.8		9.9 / 9.9
Water Quality Sensitive Receivers
Gazetted Beaches	Tong Fuk	B1	6.8 / 6.8		8.5 / 8.5
	Upper Cheung Sha Beach	B2	6.7 / 6.7		8.6 / 8.6
	Lower Cheung Sha Beach	B3	6.5 / 6.5		8.6 / 8.6
	Pui O Beach	B4	6.9 / 6.9		9.2 / 9.2
	Cheung Chau Tung Wan Beach	B5	4.1 / 5.0		8.9 / 11.2
	Kwun Yam Wan Beach	B6	3.7 / 3.7		9.0 / 10.7
	Hung Shing Yeh Beach	B8	1.8 / 1.8		>10 / >10
	Lo So Shing Beach	B9	2.1 / 2.1		>10 / >10
Non-gazetted Beaches	Lung Kwu Sheung Tan	NB1	1.7 / 1.7		>10 / >10
	Lung Kwu Tan	NB12	3.5 / 3.5		>10 / >10
	Hau Hok Wan	NB2	5.1 / 5.4		>10 / >10
	Fan Lau Sai Wan	NB3	1.8 / 1.8		>10 / >10
	Fan Lau Tung Wan	NB4	1.9 / 2.1		>10 / >10
	Siu A Chau Wan	NB5	3.9 / 4.1		5.9 / 6.1
	Yi Long Wan	NB6	4.4 / 4.4		6.9 / 7.1
	Tai Long Wan	NB7	4.9 / 4.9		7.5 / 7.6
	Tai Kwai Wan	NB8	4.8 / 5.2		9.2 / 9.2
	Po Yue Wan	NB9	2.9 / 2.9		7.2 / 7.2
	Shek Pai Wan	NB10	4.0 / 9.1		>10 / >10
	Mo Tat Wan	NB11	4.3 / 9.5		>10 / >10
Seawater Intakes	Sludge Treatment Facilities	C1	1.6 / 1.6		>10 / >10
	Black Point Power Station	C2	1.1 / 1.1		>10 / >10
	Castle Peak Power Station	C3	4.4 / 4.4		>10 / >10
	Shiu Wing Steel Mill	C4	5.3 / 5.3		>10 / >10
	Tuen Mun Area 38	C5	6.0 / 6.1		>10 / >10
	Airport	C6-9	5.5 / 5.6		>10 / >10
	Pumping Station at Tai Kwai Wan	NB8	4.8 / 5.2		9.2 / 9.2
	Sha Wan Drive	C10	6.5 / 6.5	>10 / >10
	Queen Mary Hospital	C14	6.5 / 6.5	>10 / >10
	Cyberport	C15	5.7 / 7.2	>10 / >10
	Wah Fu Estate	C11	5.3 / 6.4	>10 / >10
	Ap Lei Chau	C12	5.8 / 8.2	>10 / >10
	Lamma Power Station	C13	0.5 / 0.5	>10 / >10

Note: (1) “Numerous” generally describe WSRs as a large area. Model observation points listed are selected locations which are representative and close to the project affected area.

(2) Location of Secondary Contact Recreation Subzone and potential water sports activities are generally also covered by other WSRs in close proximity, such as gazetted and non-gazetted beaches, marine ecological sensitive receivers, etc. Therefore, additional stand-alone WSRs for Secondary Contact Recreation Subzone and potential water sports activities are not included.

Table 7.7b Additional Observation Points for Water Quality Modelling

Description	Location	Model Output Location	Geodesic Distance / Approximate Shortest Distance by Sea (km)
Description	Location	Model Output Location	from the Proposed Subsea Pipeline	from the Proposed LNG Terminal
Observation Points (for reference)
Boundary of Existing/Proposed Marine Parks	Sha Chau and Lung Kwu Chau MP	MPA-1-4	0.1 / 0.1	>10 / >10
	Proposed Southwest Lantau MP	MPC-1-6	0.1 / 0.1	9.4 / 9.8
	Proposed South Lantau MP	MPD-1-7	0.05-0.2 / 0.05-0.2	0.2 / 0.2

Parameter	Criterion
Colour (HU)	< 20
Turbidity (NTU)	< 10
Threshold Odour No.	< 100
Ammoniacal Nitrogen (mg L^-1)	< 1
Suspended Solids (mg L^-1)	< 10
Dissolved Oxygen (mg L^-1)	> 2
5-day Biochemical Oxygen Demand (mg L^-1)	< 10
Synthetic Detergents (mg L^-1)	< 5
E. coli (cfu/100mL)	< 20,000

Table 7.9 Allowable Increase in SS (mg L^-1) Levels for Water Quality Sensitive Receivers and Observation Points

Sensitive Receivers	Name	Model Output Location	EPD Station	Relevant Depth	Dry Season		Wet Season
					Ambient Level ^(a)	WQO Allowable Change	Ambient Level ^(a)	WQO Allowable Change
Fisheries Sensitive Receivers
Spawning/Nursery Grounds	Fisheries Spawning Ground in North Lantau	MPA-5	NM5	Depth-averaged	21.9	6.6	20.0	6.0
Spawning/Nursery Grounds		AR1	NM6	Depth-averaged	26.0	7.8	14.3	4.3
		CR3	NM5	Depth-averaged	21.9	6.6	20.0	6.0
	Fisheries Spawning/Nursery Grounds in South Lantau	MPC-8	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPD-8	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPD-9	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		CR4	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		CR5	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		NB9	SM12	Depth-averaged	18.9	5.7	13.6	4.1
		NB10	SM3	Depth-averaged	10.3	3.1	7.7	2.3
		B8	SM5	Depth-averaged	13.1	3.9	9.9	3.0
		B9	SM5	Depth-averaged	13.1	3.9	9.9	3.0
		MPE	SM5	Depth-averaged	13.1	3.9	9.9	3.0
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	AR1	NM6	Bottom	32.7	9.8	23.0	6.9
Fish Culture Zone	Cheung Sha Wan FCZ	FCZ1	SM12	Depth-averaged	18.9	31.1 ^(b)	13.6	36.4 ^(b)
	Lo Tik Wan FCZ	FCZ2	SM3	Depth-averaged	10.3	39.7 ^(b)	7.7	42.3 ^(b)
	Sok Kwu Wan FCZ	FCZ3	SM4	Depth-averaged	7.0	43.0 ^(b)	6.8	43.2 ^(b)
Oyster Production Area	Sheung Pak Nai	O1	DM4	Depth-averaged	28.2	8.5	23.5	7.1
Ecological Sensitive Receivers
Seagrass Beds	Ha Pak Nai	H1	DM4	Bottom	35.3	10.6	29.3	8.8
	Tung Chung Bay	C8	NM8	Bottom	38.4	11.5	39.5	11.9
Marine Park (MP)	Sha Chau and Lung Kwu Chau MP	MPA-5	NM5	Depth-averaged	21.9	6.6	20.0	6.0
	Proposed AAHK 3RS MP	MPB	NM8	Depth-averaged	28.3	8.5	21.0	6.3
	Proposed Southwest Lantau MP	MPC-7	NM8	Depth-averaged	28.3	8.5	21.0	6.3
	Proposed Southwest Lantau MP	MPC-8	SM20	Depth-averaged	20.1	6.0	21.1	6.3
	Proposed South Lantau MP	MPD-8	SM20	Depth-averaged	20.1	6.0	21.1	6.3
	Proposed South Lantau MP	MPD-9	SM17	Depth-averaged	13.0	3.9	10.3	3.1
	Potential South Lamma MP	MPE	SM5	Depth-averaged	13.1	3.9	9.9	3.0
Intertidal Mudflats / Mangroves / Horseshoe Crab Nursery Grounds ^(c)	Sheung Pak Nai	H9	DM4	Depth-averaged	28.1	-	23.5	-
	Ha Pak Nai	H1	DM4	Depth-averaged	28.1	-	23.5	-
	Ngau Hom Shek	H8	DM3	Depth-averaged	28.1	-	27.2	-
	Lung Kwu Sheung Tan	NB1	NM5	Depth-averaged	21.9	-	20.0	-
	Tung Chung Bay	C8	NM8	Depth-averaged	28.3	-	21.0	-
	Sha Lo Wan	H2	NM8	Depth-averaged	28.3	-	21.0	-
	Sham Wat Wan	H6	NM8	Depth-averaged	28.3	-	21.0	-
	Tai O	H3	NM8	Depth-averaged	28.3	-	21.0	-
	Yi O	H4	NM8	Depth-averaged	28.3	-	21.0	-
	Fan Lau Tung Wan	MPC-5	SM20	Depth-averaged	20.2	-	21.1	-
		NB4	SM20	Depth-averaged	20.2	-	21.1	-
	Tong Fuk Miu Wan / Shui Hau	H5	SM13	Depth-averaged	15.8	-	12.3	-
	Pui O	B4	SM13	Depth-averaged	15.8	-	12.3	-
	Shek Kwu Chau North	H7	SM13	Depth-averaged	15.8	-	12.3	-
Corals	Artificial Seawall at BPPS	CR1	DM5	Bottom	38.8	11.6	24.0	7.2
		CR2	DM5	Bottom	38.8	11.6	24.0	7.2
	Pak Chau	CR3	NM5	Bottom	34.7	10.4	40.2	12.1
	Shek Kwu Chau	CR4	SM17	Bottom	18.0	5.4	16.0	4.8
	Siu A Chau	CR5	SM20	Bottom	24.0	7.2	35.4	10.6
	Tai A Chau	CR6	SM20	Bottom	24.0	7.2	35.4	10.6
	Cheung Chau	CR7	SM7	Bottom	13.0	3.9	18.5	5.6
		CR8	SM7	Bottom	13.0	3.9	18.5	5.6
	Hei Ling Chau	CR9	SM7	Bottom	13.0	3.9	18.5	5.6
		CR10	SM7	Bottom	13.0	3.9	18.5	5.6
	Sunshine Island	CR11	SM7	Bottom	13.0	3.9	18.5	5.6
	Shek Kok Tsui	CR12	SM7	Bottom	13.0	3.9	18.5	5.6
	Pak Kok	CR13	WM1	Bottom	16.0	4.8	16.0	4.8
	Sha Wan	CR14	WM1	Bottom	16.0	4.8	16.0	4.8
	Ap Lei Chau	CR15	SM3	Bottom	14.8	4.4	12.5	3.8
	Wong Chuk Kok	CR16	SM3	Bottom	14.8	4.4	12.5	3.8
		CR17	SM3	Bottom	14.8	4.4	12.5	3.8
	Sham Wan	CR18	SM18	Bottom	16.0	4.8	13.0	3.9
	Luk Chau	CR19	SM3	Bottom	14.8	4.4	12.5	3.8
	Hung Shing Yeh	CR20	SM5	Bottom	16.0	4.8	14.0	4.2
	Ha Mei Wan	CR21	SM5	Bottom	16.0	4.8	14.0	4.2
	Chi Ma Wan Peninsula	CR22	SM12	Bottom	21.8	6.5	18.0	5.4
Water Quality Sensitive Receivers
Gazetted Beaches	Tong Fuk	B1	SM13	Depth-averaged	16.1	4.8	12.3	3.7
	Upper Cheung Sha Beach	B2	SM13	Depth-averaged	16.1	4.8	12.3	3.7
	Lower Cheung Sha Beach	B3	SM13	Depth-averaged	16.1	4.8	12.3	3.7
	Pui O Beach	B4	SM13	Depth-averaged	16.1	4.8	12.3	3.7
	Cheung Chau Tung Wan Beach	B5	SM7	Depth-averaged	11.6	3.5	12.0	3.6
	Kwun Yam Wan Beach	B6	SM7	Depth-averaged	11.6	3.5	12.0	3.6
	Hung Shing Yeh Beach	B8	SM5	Depth-averaged	13.1	3.9	9.9	3.0
	Lo So Shing Beach	B9	SM5	Depth-averaged	13.1	3.9	9.9	3.0
Non-gazetted Beaches	Lung Kwu Sheung Tan	NB1	NM5	Depth-averaged	21.9	6.6	20.0	6.0
	Lung Kwu Tan	NB12	NM5	Depth-averaged	21.9	6.6	20.0	6.0
	Hau Hok Wan	NB2	NM8	Depth-averaged	28.3	8.5	21.0	6.3
	Fan Lau Sai Wan	NB3	SM20	Depth-averaged	20.1	6.0	21.1	6.3
	Fan Lau Tung Wan	NB4	SM20	Depth-averaged	20.1	6.0	21.1	6.3
	Siu A Chau Wan	NB5	SM20	Depth-averaged	20.1	6.0	21.1	6.3
	Yi Long Wan	NB6	SM12	Depth-averaged	18.9	5.7	13.6	4.1
	Tai Long Wan	NB7	SM12	Depth-averaged	18.9	5.7	13.6	4.1
	Tai Kwai Wan	NB8	SM12	Depth-averaged	18.9	5.7	13.6	4.1
	Po Yue Wan	NB9	SM12	Depth-averaged	18.9	5.7	13.6	4.1
	Shek Pai Wan	NB10	SM3	Depth-averaged	10.3	3.1	7.7	2.3
	Mo Tat Wan	NB11	SM4	Depth-averaged	7.0	2.1	6.8	2.0
Seawater Intakes ^(d)	Sludge Treatment Facilities	C1 ^(b)	DM5	Bottom	35.3	94.7	29.3	100.7
	Black Point Power Station	C2 ^(b)	DM5	Bottom	35.3	728.7	29.3	734.7
	Castle Peak Power Station	C3 ^(b)	NM5	Bottom	34.7	729.3	40.2	723.8
	Shiu Wing Steel Mill	C4	NM5	Bottom	34.7	10.4	40.2	12.1
	Tuen Mun Area 38	C5	NM3	Bottom	26.2	7.9	27.0	8.1
	Airport	C6	NM6	Bottom	32.7	9.8	23.0	6.9
		C7	NM6	Bottom	32.7	9.8	23.0	6.9
		C8	NM8	Bottom	38.4	11.5	39.5	11.9
		C9	NM8	Bottom	38.4	11.5	39.5	11.9
	Tai Kwai Wan	NB8 ^(d)	SM12	Bottom	21.8	6.5	18.0	5.4
	Sha Wan Drive	C10	WM1	Bottom	16.0	4.8	16.0	4.8
	Queen Mary Hospital	C14	WM1	Bottom	16.0	4.8	16.0	4.8
	Cyber Port	C15	WM1	Bottom	16.0	4.8	16.0	4.8
	Wah Fu Estate	C11	WM1	Bottom	16.0	4.8	16.0	4.8
	Ap Lei Chau	C12 ^(d)	SM3	Bottom	14.8	4.4	12.5	3.8
	Lamma Power Station	C13 ^(b)	SM5	Bottom	16.0	84.0	14.0	86.0
Observation Points (for reference)
Boundary of Existing & Proposed Marine Parks		MPA-1	NM5	Depth-averaged	21.9	6.6	20.0	6.0
		MPA-2	NM5	Depth-averaged	21.9	6.6	20.0	6.0
		MPA-3	NM6	Depth-averaged	26.0	7.8	14.3	4.3
		MPA-4	NM6	Depth-averaged	26.0	7.8	14.3	4.3
		MPC-1	NM8	Depth-averaged	28.3	8.5	21.0	6.3
		MPC-2	NM8	Depth-averaged	28.3	8.5	21.0	6.3
		MPC-3	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPC-4	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPC-5	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPC-6	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPD-1	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPD-2	SM20	Depth-averaged	20.1	6.0	21.1	6.3
		MPD-3	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		MPD-4	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		MPD-5	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		MPD-6	SM17	Depth-averaged	13.0	3.9	10.3	3.1
		MPD-7	SM17	Depth-averaged	13.0	3.9	10.3	3.1

Notes:

a. Ambient level is calculated as 90^th percentile of the EPD routine monitoring data (1986-2016) at respective EPD station close to the WSRs;

b. This table is applicable for those sensitive receivers which were assessed against the WQO. There are other assessment criteria of certain type of WSRs. The allowable elevation for Fish Culture Zones is 50 mg L^-1 minus ambient level. The allowable SS level for intakes at the BPPS, CPPS and LPS are 764, 764 and 100 mg L^-1. The allowable SS level for intake at the Sludge Treatment Facilities is 130 mg L^-1 based on the information provided by the operator of the facilities in November 2017.

c. For intertidal mudflat, mangrove and horseshoe crab WSRs, organisms living in these habitats are generally adapted to muddy or sandy substrate and used to turbid water. No SS criterion is recommended for these WSRs;

d. WSD stipulates a specific requirement for the seawater intake, the SS level being maintained below 10 mg L^-1. This is not applicable to both NB8 and C12 where baseline SS level exceeds 10 mg L^-1. WQO criteria of elevation not exceeding 30% of the ambient level would be adopted.

Table 7.10 Allowable DO Depletion (mg L^-1) for Water Quality Sensitive Receivers and Observation Points

Sensitive Receivers	Name	Model Output Location	EPD Station	Relevant Depth	Annual
					Ambient Level ^(a)	WQO Allowable Change
Fisheries Sensitive Receivers
Spawning/Nursery Grounds	Fisheries Spawning Ground in North Lantau	MPA-5	NM5	Depth-averaged	4.2	0.2
Spawning/Nursery Grounds		AR1	NM6	Depth-averaged	4.9	0.9
		CR3	NM5	Depth-averaged	4.2	0.2
	Fisheries Spawning/Nursery Grounds in South Lantau	MPC-8	SM20	Depth-averaged	4.8	0.8
		MPD-8	SM20	Depth-averaged	4.8	0.8
		MPD-9	SM17	Depth-averaged	5.1	1.1
		CR4	SM17	Depth-averaged	5.1	1.1
		CR5	SM20	Depth-averaged	4.8	0.8
		NB9	SM12	Depth-averaged	5.5	1.5
		NB10	SM3	Depth-averaged	4.5	0.5
		B8	SM5	Depth-averaged	5.4	1.4
		B9	SM5	Depth-averaged	5.4	1.4
		MPE	SM5	Depth-averaged	5.4	1.4
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	AR1	NM6	Bottom	4.6	2.6
Fish Culture Zone	Cheung Sha Wan FCZ	FCZ1	SM12	Depth-averaged	5.5	0.5
	Lo Tik Wan FCZ	FCZ2	SM3	Depth-averaged	4.5	0.0
	Sok Kwu Wan FCZ	FCZ3	SM4	Depth-averaged	5.0	0.0
Oyster Production Area	Sheung Pak Nai	O1	DM4	Depth-averaged	4.8	0.0
Ecological Sensitive Receivers
Seagrass Beds	Ha Pak Nai	H1	DM4	Bottom	4.6	2.6
	Tung Chung Bay	C8	NM8	Bottom	4.1	2.1
Marine Park (MP)	Sha Chau and Lung Kwu Chau MP	MPA-5	NM5	Depth-averaged	4.2	0.2
	Proposed AAHK 3RS MP	MPB	NM8	Depth-averaged	4.8	0.8
	Proposed Southwest Lantau MP	MPC-7	NM8	Depth-averaged	4.8	0.8
	Proposed Southwest Lantau MP	MPC-8	SM20	Depth-averaged	4.8	0.8
	Proposed South Lantau MP	MPD-8	SM20	Depth-averaged	4.8	0.8
	Proposed South Lantau MP	MPD-9	SM17	Depth-averaged	5.1	1.1
	Potential South Lamma MP	MPE	SM5	Depth-averaged	5.4	1.4
Intertidal Mudflats / Mangroves / Horseshoe Crab Nursery Grounds	Sheung Pak Nai	H9	DM4	Depth-averaged	4.8	0.8
	Ha Pak Nai	H1	DM4	Depth-averaged	4.8	0.8
	Ngau Hom Shek	H8	DM3	Depth-averaged	4.5	0.5
	Lung Kwu Sheung Tan	NB1	NM5	Depth-averaged	4.2	0.2
	Tung Chung Bay	C8	NM8	Depth-averaged	4.8	0.8
	Sha Lo Wan	H2	NM8	Depth-averaged	4.8	0.8
	Sham Wat Wan	H6	NM8	Depth-averaged	4.8	0.8
	Tai O	H3	NM8	Depth-averaged	4.8	0.8
	Yi O	H4	NM8	Depth-averaged	4.8	0.8
	Fan Lau Tung Wan	MPC-5	SM20	Depth-averaged	4.8	0.8
		NB4	SM20	Depth-averaged	4.8	0.8
	Tong Fuk Miu Wan / Shui Hau	H5	SM13	Depth-averaged	5.6	1.6
	Pui O	B4	SM13	Depth-averaged	5.6	1.6
	Shek Kwu Chau North	H7	SM13	Depth-averaged	5.6	1.6
Corals	Artificial Seawall at BPPS	CR1	DM5	Bottom	4.1	2.1
		CR2	DM5	Bottom	4.1	2.1
	Pak Chau	CR3	NM5	Bottom	3.1	1.1
	Shek Kwu Chau	CR4	SM17	Bottom	3.8	1.8
	Siu A Chau	CR5	SM20	Bottom	3.9	1.9
	Tai A Chau	CR6	SM20	Bottom	3.9	1.9
	Cheung Chau	CR7	SM7	Bottom	4.4	2.4
		CR8	SM7	Bottom	4.4	2.4
	Hei Ling Chau	CR9	SM7	Bottom	4.4	2.4
		CR10	SM7	Bottom	4.4	2.4
	Sunshine Island	CR11	SM7	Bottom	4.4	2.4
	Shek Kok Tsui	CR12	SM7	Bottom	4.4	2.4
	Pak Kok	CR13	WM1	Bottom	3.2	1.2
	Sha Wan	CR14	WM1	Bottom	3.2	1.2
	Ap Lei Chau	CR15	SM3	Bottom	3.3	1.3
	Wong Chuk Kok	CR16	SM3	Bottom	3.3	1.3
		CR17	SM3	Bottom	3.3	1.3
	Sham Wan	CR18	SM18	Bottom	3.1	1.1
	Luk Chau	CR19	SM3	Bottom	3.3	1.3
	Hung Shing Yeh	CR20	SM5	Bottom	4.5	2.5
	Ha Mei Wan	CR21	SM5	Bottom	4.5	2.5
	Chi Ma Wan Peninsula	CR22	SM12	Bottom	5.3	3.3
Water Quality Sensitive Receivers
Gazetted Beaches	Tong Fuk	B1	SM13	Depth-averaged	5.6	1.6
	Upper Cheung Sha Beach	B2	SM13	Depth-averaged	5.6	1.6
	Lower Cheung Sha Beach	B3	SM13	Depth-averaged	5.6	1.6
	Pui O Beach	B4	SM13	Depth-averaged	5.6	1.6
	Cheung Chau Tung Wan Beach	B5	SM7	Depth-averaged	5.1	1.1
	Kwun Yam Wan Beach	B6	SM7	Depth-averaged	5.1	1.1
	Hung Shing Yeh Beach	B8	SM5	Depth-averaged	5.4	1.4
	Lo So Shing Beach	B9	SM5	Depth-averaged	5.4	1.4
Non-gazetted Beaches	Lung Kwu Sheung Tan	NB1	NM5	Depth-averaged	4.2	0.2
	Lung Kwu Tan	NB12	NM5	Depth-averaged	4.2	0.2
	Hau Hok Wan	NB2	NM8	Depth-averaged	4.8	0.8
	Fan Lau Sai Wan	NB3	SM20	Depth-averaged	4.8	0.8
	Fan Lau Tung Wan	NB4	SM20	Depth-averaged	4.8	0.8
	Siu A Chau Wan	NB5	SM20	Depth-averaged	4.8	0.8
	Yi Long Wan	NB6	SM12	Depth-averaged	5.5	1.5
	Tai Long Wan	NB7	SM12	Depth-averaged	5.5	1.5
	Tai Kwai Wan	NB8	SM12	Depth-averaged	5.5	1.5
	Po Yue Wan	NB9	SM12	Depth-averaged	5.5	1.5
	Shek Pai Wan	NB10	SM3	Depth-averaged	4.5	0.5
	Mo Tat Wan	NB11	SM4	Depth-averaged	5.0	1.0
Seawater Intakes ^(b)	Tai Kwai Wan	NB8	SM12	Bottom	5.3	3.3
	Ap Lei Chau	C12	SM3	Bottom	3.3	1.3
Observation Points (for reference)
Boundary of Existing & Proposed Marine Parks		MPA-1	NM5	Depth-averaged	4.2	0.2
		MPA-2	NM5	Depth-averaged	4.2	0.2
		MPA-3	NM6	Depth-averaged	4.9	0.9
		MPA-4	NM6	Depth-averaged	4.9	0.9
		MPC-1	NM8	Depth-averaged	4.8	0.8
		MPC-2	NM8	Depth-averaged	4.8	0.8
		MPC-3	SM20	Depth-averaged	4.8	0.8
		MPC-4	SM20	Depth-averaged	4.8	0.8
		MPC-5	SM20	Depth-averaged	4.8	0.8
		MPC-6	SM20	Depth-averaged	4.8	0.8
		MPD-1	SM20	Depth-averaged	4.8	0.8
		MPD-2	SM20	Depth-averaged	4.8	0.8
		MPD-3	SM17	Depth-averaged	5.1	1.1
		MPD-4	SM17	Depth-averaged	5.1	1.1
		MPD-5	SM17	Depth-averaged	5.1	1.1
		MPD-6	SM17	Depth-averaged	5.1	1.1
		MPD-7	SM17	Depth-averaged	5.1	1.1

Notes:

a. Ambient level is calculated as 10th percentile of the EPD routine monitoring data (1986-2016) at respective EPD station close to the WSRs.

b. There is a specific requirement for WSD seawater intakes and the DO should be maintained at above 2 mg L^-1. Allowable DO depletion is calculated as 10^th percentile of the ambient DO level minus 2 mg L^-1. There is no applicable standard for other seawater intakes, thus those intakes are not included.

7.4.5 Sediment Deposition

Impacts to artificial reefs as well as coral colonies have been assessed with regard to sediment deposition. The assessment criterion of 200 g m^-2 day^-1, which represents an indicative level above which sustained deposition could harm sediment sensitive hermatypic corals, has been used in approved EIA Reports ([5]) ([6])and has been adopted here.

7.4.6 Nutrients

Elevation in the levels of nutrients as a result of the Project’s construction activities, if any, will be compared against the respective WQO (Table 7.1 refers).

7.4.7 Dissolved Metals and Organic Contaminants

There are no existing regulatory standards or guidelines for dissolved metals and organic contaminants in the marine waters of Hong Kong. It is thus proposed to make reference to relevant international standards and this approach has been adopted in previous approved EIAs, i.e., EIA for Decommissioning of Cheoy Lee Shipyard at Penny’s Bay ([7]), EIA for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit ([8]), EIA for Wanchai Development Phase II ([9]), EIA for Liquefied Natural Gas (LNG) Receiving Terminal and Associated Facilities ([10]),EIA for Hong Kong Offshore Wind Farm in Southeastern Waters ([11]), Additional Gas-fired Generation Units Project ([12]). Table 7.11 shows the assessment criteria for dissolved metals and organic contaminants for this Study.

Table 7.11 Summary of Assessment Criteria for Dissolved Metals and Organic Contaminants

Parameter	Unit	Assessment Criteria for this Study
Metals
Cadmium (Cd)	mg L^-1	2.5 ^{(a) (b)}
Chromium (Cr)	mg L^-1	15 ^{(a) (b)}
Copper (Cu)	mg L^-1	5 ^{(a) (b)}
Nickel (Ni)	mg L^-1	30 ^{(a) (b)}
Lead (Pb)	mg L^-1	25 ^{(a) (b)}
Zinc (Zn)	mg L^-1	40 ^{(a) (c)}
Mercury (Hg)	mg L^-1	0.3 ^{(a) (b)}
Arsenic (As)	mg L^-1	25 ^{(a) (b)}
Silver (Ag)	mg L^-1	1.9 ^(e)
PAHs
Total PAHs	mg L^-1	3.0 ^(d)
PCBs
Total PCBs	mg L^-1	0.03 ^(e)
Organotins
Tributyltin (TBT)	mg L^-1	0.1 ^(f)(maximum concentration)

Notes:

(a) UK Environment Agency, Environmental Quality Standards (EQS) for List 1 & 2 dangerous substances, EC Dangerous Substances Directive (76/464/EEC)
(https://www.gov.uk/government/publications/list-of-chemicals-for-water-framework-directive-assessments/environmental-quality-standards-directive-eqsd-list-for-wfd-assessments).

(b) Annual average dissolved concentration (ie usually involving filtration a 0.45-um membrane filter before analysis).

(d) Australian and New Zealand Environment and Conservation Council (ANZECC), Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000) – Trigger values for protection of 90% of species.
(http://www.agriculture.gov.au/SiteCollectionDocuments/water/nwqms-guidelines-4-vol2.pdf).

(e) U.S. Environmental Protection Agency, National Recommended Water Quality Criteria, 2009. (http://www.epa.gov/waterscience/criteria/wqctable). The Criteria Maximum Concentration (CMC) is an estimate of the highest concentration of a material in surface water (ie saltwater) to which an aquatic community can be exposed briefly without resulting in an unacceptable effect. CMC is used as the criterion of the respective compounds in this study.

(f) Salazar MH, Salazar SM (1996) Mussels as Bioindicators: Effects of TBT on Survival, Bioaccumulation, and Growth under Natural Conditions. In Organotin, edited by M.A. Champ and P.F. Seligman. Chapman & Hall, London.

There are no existing regulatory standards or guidelines for total PCBs, total PAHs and TBT in water and hence reference has been made to the USEPA water quality criteria, Australian water quality guidelines, and international literature, respectively. The assessment criteria for total PCBs, total PAHs and TBT are 0.03 μg L^-1, 3.0 μg L^-1, and 0.1 μg L^-1 respectively.

7.4.8 Total Residual Chlorine

Electrochlorination of seawater would be conducted to control biofouling of the open rack vaporizer of the FSRU Vessel. The stream of cooled water discharge would carry low level of residual chlorine of less than or equal to 0.5 mg L^-1 and be discharged into marine waters. Previous studies ([13])([14]) indicated adverse impacts on marine organisms may arise for total residual chlorine (TRC) at or above 0.02 mg L^-1. This criterion was adopted in approved EIAs of Kai Tak Development (AEIAR-130/2009), Desalination Plant in Tseung Kwan O (AEIAR-192/2015) and Additional Gas-fired Generation Units Project (AEIAR-197/2016), and was adopted as assessment criterion in this EIA.

Seawater intakes, gazetted and non-gazetted beaches are not considered sensitive to TRC. No assessment criterion is proposed for these WSRs.

7.5 Assessment Methodology

7.5.1 General Methodology

The methodology employed to assess potential water quality impacts associated with the construction and operation of the Project is presented in the Water Quality Modelling Method Statement (Annex 7B) and has been based on the information presented in the Project Description (Section 3). Full details of the scenarios examined in the modelling works are provided in Annex 7B. Verification of hydrodynamic model has been provided under Appendix B of Annex 7B and model spin up check for construction phase sediment plume modelling has been provided under Appendix C of Annex 7B. The WSRs assessed are presented in Figure 7.2.

7.5.2 Uncertainties in Assessment Methodology

Uncertainties in the assessment of the impacts from marine construction activities have been considered when drawing conclusions from the assessment. In carrying out the assessment, the worst case assumptions have been made in order to provide a conservative assessment of environmental impacts. These assumptions are considered in detail in Annex 7B and are not further discussed here.

Uncertainties in operation phase discharge modelling have been identified in Annex 7B. To ensure robustness of modelling assessment, conservative assumptions have been made to address the uncertainties from future operation. These assumptions include:

· Temperature and level of TRC of effluent from the Project were assumed to be released at their maximum level (temperature differential of -7°C and TRC concentration of 0.5 mg L^-1); and

· Model spin up was conducted for multiple tidal spring-neap cycles to ensure sufficient background build-up of cooled discharge and TRC, if any, could be captured in the modelling;

· Location of sediment source for maintenance dredging was selected at representative location to reflect the worst case scenario.

7.6 Potential Sources of Impact

Potential sources of impacts to water quality arising from the Project may occur during both the construction and operation phases. Each is discussed in turn below.

7.6.1 Construction Phase

As discussed in Section 3, marine construction works would be required for the construction of the proposed Jetty by piling as well as the construction of subsea gas pipelines from the Jetty to the BPPS and the LPS by dredging and jetting. Potential sources of water quality impact from the land-based and marine-based construction works include:

· Changes in water quality, including suspended sediment dispersion, sediment deposition, DO depletion, and elevated concentrations of nutrients, heavy metals and organic contaminants, due to marine dredging and jetting at the Jetty and subsea pipeline routes. Other marine construction activities detailed in Section 3 would not involve significant sediment disturbance;

· Vessel discharges, including sewage effluent from construction workforce;

· Runoff from land-based work sites at the GRS at the BPPS, the GRS at the LPS, and Jetty topside construction; and

· Hydrotesting for subsea pipeline pre-commissioning activities.

7.6.2 Operation Phase

Since the proposed LNG Terminal consists of a piled deck Jetty and an FSRU Vessel which is essentially a ship, its presence would not result in notable change in the seabed level therefore notable change in flow regime would not be expected.

The potential impacts to water quality arising from the operation of the Project have been identified as follows:

· Change in seawater temperature and increase in TRC level due to the discharge of cooled water from the FSRU Vessel;

· Change in water quality due to the discharge of concentrated seawater and treated effluent from the FSRU Vessel;

· Change in water quality due to the discharge of other effluents from the FSRU Vessel and LNGC, including ballast water;

· Potential risk of accidental spills and leaks due to the operation of the LNG Terminal; and

· Potential water quality impact from maintenance dredging at the LNG Terminal.

7.7 Impact Assessment – Construction Phase

7.7.1 Changes in Water Quality due to Marine Construction Activities

Suspended Solids (SS) Dispersion and Sedimentation

Sediment plume modelling study has been conducted to assess the potential SS impact from marine dredging and jetting works of the Project. A total of nine representative scenarios for sediment plume modelling has been conducted, they include:

· C01A - Pipeline trench formation using grab dredgers and Jetty construction (Figure 3.1a of Annex 7B);

· C01B - Pipeline trench formation using grab dredgers and Trailing Suction Hopper Dredger (TSHD) from BPPS Pipeline KP12.1 to 21.3 (Figure 3.1b of Annex 7B);

· C01C - Pipeline trench formation using grab dredgers and TSHD from BPPS Pipeline KP41.1 to 42.9 (Figure 3.1c of Annex 7B);

· C02 - Pipeline trench formation using jetting machine from BPPS Pipeline KP44.9 to 42.9 (Figure 3.1d of Annex 7B);

· C03 - Pipeline trench formation using jetting machine from BPPS Pipeline KP41.1 to 37.5 (Figure 3.1e of Annex 7B);

· C04 - Pipeline trench formation using jetting machine from BPPS Pipeline KP31.5 to 21.3 (Figure 3.1f of Annex 7B);

· C05 - Pipeline trench formation using jetting machine from BPPS Pipeline KP15.6 to 0.1 (Figure 3.1g of Annex 7B);

· C06 - Pipeline trench formation using jetting machine from LPS Pipeline KP17.4 to 0.1 (Figure 3.1h of Annex 7B);

· C07 – Pipeline trench formation using jetting machine from BPPS Pipeline KP36.0 to 31.5 (Figure 3.1i of Annex 7B).

Details on the number of concurrent plants, type of plants used, working rate, number of working hours per day as well as other concurrent projects have been discussed in Annex 7B and is not further discussed in this Section. The modelling predictions for these scenarios are provided below.

Dredging Scenario C01A

In this scenario, a total of seven closed grab dredgers were assumed to work concurrently at various sections of the BPPS Pipeline and LPS Pipeline. The assumed locations and working rates of the modelled sediment sources are shown in Figure 3.1a of Annex 7B. All work plants were assumed to be working continuously for 24 hours throughout the simulation. Multiple closed grab dredgers on the same section of pipeline were assumed to be working concurrently.

Predicted maximum SS elevation from the dredging works and other concurrent projects is provided in Table 7C.1 of Annex 7C. Contour plots showing the maximum SS elevation throughout the simulation are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for all the WSRs in both seasons, except for the coral colonies CR1 where the predicted maximum sedimentation flux exceeded the assessment criterion of 200 g m^-2 day^-1, up to 295.4 g m^-2 day^-1 and 260.9 g m^-2 day^-1 in dry and wet seasons respectively. Mitigation measure in terms of silt curtain surrounding grab dredgers at all sediment sources at BPPS shore approach and the nearby WSRs (CR1 and CR2([15])) is recommended to reduce potential impacts to these isolated corals.

Observation point MPD-5 also indicated SS elevation at the southeast corner of the proposed South Lantau Marine Park (SLMP), with maximum SS elevation predicted to be 3.7 mg L^-1 in wet seasons. However, the elevation was predicted to be limited to localized area given that other locations within the marine park (MPD-1, MPD-2, MPD-3, MPD-4, MPD-6, MPD-7, MPD-8 and MPD-9) did not show particularly high SS elevations in both seasons. Given that the other locations of SLMP are not affected, it can be deduced that the marine ecological sensitive receivers at the proposed Marine Park would not be adversely affected by the localised elevations predicted at the corner of this marine park. Nevertheless, as standard good practice for dredging operation, silt curtain will be implemented for 03_G and will also for other grab dredging sections ([16]). Furthermore, mitigation measure by adopting two layers of silt curtain with combined silt removal efficiency of 80% reduction surrounding the coral locations (CR1 and CR2) is recommended to reduce potential impacts to these WSRs. Such level of silt removal efficiency was adopted in the approved EIAs of AEIAR-106/2007 Liquefied Natural Gas (LNG) Receiving Terminal and Associated Facilities (80% silt removal), AEIAR-146/2009 Tuen Mun - Chek Lap Kok Link (87% silt removal) and AEIAR-145/2009 Hong Kong - Zhuhai - Macao Bridge Hong Kong Boundary Crossing Facilities (87% silt removal), and confirmed in a recent silt curtain efficiency test conducted under EP-489/2014 Expansion of Hong Kong International Airport into a Three-Runway System (which involves ground treatment, land formation and jetting of submarine cable, etc.).

According to the Contaminated Spoil Management Study ([17]), the implementation of silt curtain around the closed grab dredgers will reduce the dispersion of SS by a factor of 4 (equivalent to 75% reduction). This SS reduction factor has been adopted in a number of past studies involving release of marine sediment, including the approved EIA of Additional Gas-fired Generation Units at the BPPS, EIA of SCL Hung Hom to Admiralty Section, IWMF EIA, WDII & CWB EIA, CT Dredging EIA as well as the Western Coast Road EIA study.

The predicted maximum SS elevations and sedimentation flux with mitigation are provided Table 7C.10 of Annex 7C. The predicted maximum sedimentation flux at CR1 and maximum SS elevation at MPD-5 would be below the proposed assessment criterion in both seasons. It is therefore concluded that, with the implementation of mitigation measures, no unacceptable SS impact from the dredging operation would be expected.

Dredging Scenario C01B

Alternative trenching method for the BPPS Pipeline section along Urmston Road and southwest Lantau has been considered to allow flexibility for marine works at these two busy shipping channels. The use of TSHD dredging at these two sections has been considered and modelled under Scenario C01B (TSHD dredging at southwest Lantau) and C01C (TSHD dredging at Urmston Road).

In this scenario, a total of four closed grab dredgers were assumed to work concurrently at various sections of the BPPS Pipeline and LPS Pipeline. In addition, dredging works from BPPS Pipeline KP21.3 to 15.6 was assumed to be conducted concurrently with one TSHD. The assumed locations and working rates of the modelled sediment sources are shown in Figure 3.1b of Annex 7B. All work plants were assumed to be working continuously for 24 hours throughout the simulation.

The SS elevation predictions from this scenario are similar to those of Scenario C01A, because most of the sediment released was contributed to by the same sediment sources representing the closed grab dredgers. Small changes in maximum SS elevation (when compared with Scenario C01A) near the Urmston Road (due to the removal of nearby sediment source) and southwest Lantau pipeline section (due to the change in nearby sediment source) were predicted, and the predicted levels were low and complied with the corresponding WQO criteria in both seasons.

Modelling results for CR1 and MPD-5 are similar under Scenario C01A and Scenario C01B due to grab dredging operation nearby. The same mitigation measures as Scenario C01A are recommended to reduce the potential impact from the grab dredging operation under this scenario. No mitigation measure is considered necessary for TSHD dredging. The predicted maximum SS elevations with mitigation are provided Table 7C.11 of Annex 7C. The predicted maximum sedimentation flux at CR1 and maximum SS elevation at MPD-5 would be below the proposed assessment criterion in both seasons. It is therefore concluded that, with the implementation of mitigation measures, no unacceptable SS impact from the dredging operation would be expected.

Dredging Scenario C01C

In this scenario, a total of four closed grab dredgers were assumed to work concurrently at various sections of the BPPS Pipeline and LPS Pipeline. In addition, dredging works from BPPS Pipeline KP42.9 to 41.1 was assumed to be conducted concurrently with one TSHD. This scenario is complementary to Scenario C01B and assessed the TSHD dredging at the Urmston Road pipeline section. The assumed locations and working rates of the modelled sediment sources are shown in Figure 3.1c of Annex 7B. All work plants were assumed to be working continuously for 24 hours throughout the simulation.

The SS elevation predictions from this scenario are similar to those of Scenario C01A. Small changes in maximum SS elevation (when compared with Scenario C01A) near the Urmston Road (due to the change in nearby sediment source) and southwest Lantau pipeline sections (due to removal of nearby sediment source) were predicted, and the predicted levels were low and complied with the corresponding WQO criteria in both seasons.

Modeling results at CR1 and MPD-5 are also similar under Scenarios C01A, C01B and C01C. The same mitigation measures as Scenario C01A are recommended to reduce the potential impact from the grab dredging operation under this scenario. No mitigation measure is considered necessary for TSHD dredging. The predicted maximum SS elevations with the mitigation are provided Table 7C.12 of Annex 7C. The predicted maximum sedimentation flux at CR1 and maximum SS elevation at MPD-5 would be below the proposed assessment criterion in both seasons. It is therefore concluded that, with the implementation of mitigation measures, no unacceptable SS impact from the dredging operation would be expected.

Based on the prediction of Scenarios C01A, C01B and C01C, the proposed pipeline installation by dredging using either closed grab dredgers or TSHD would not result in unacceptable SS elevation or sedimentation flux at all WSRs identified with the implementation of the proposed mitigation measures.

Jetting Scenario C02

In this scenario, one jetting machine was assumed to be working from BPPS Pipeline KP44.9 to 42.9 with working rate at 1,000 m day^-1 continuously for 24 hours throughout the simulation.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.4 of Annex 7C. Contour plots showing the maximum SS elevation throughout the simulation are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for the majority of the WSRs in both seasons. However, given the close proximity between this pipeline section and some identified WSRs, high SS elevation at the seagrass bed H1 (in dry season only), coral colonies CR1 and CR2 (both in dry and wet seasons) would exceed the corresponding WQO criterion. High sedimentation flux was also predicted at CR1 and CR2. It should be noted that the pipeline jetting operation is considered as a moving source, and so SS elevation would be transient and short-term with the predicted percentage time for exceedance of about 0.4% at H1 and up to about 3.5% at CR1 and 3.9% at CR2.

Mitigation measure in terms of two layers of silt curtain with combined silt removal efficiency of 80% reduction surrounding the coral locations (CR1 and CR2) is recommended to reduce potential impacts to these WSRs. In addition, silt curtain surrounding the jetting machine would be implemented to control the sediment loss from the jetting operation. The use of silt curtain to control sediment dispersion from jetting operation has been adopted for other cable / pipeline laying projects ([18])([19])([20])([21])([22]) and silt removal efficiency of such silt curtain would be about 85% ([23]). Therefore, the same silt removal efficiency has been adopted for the mitigated scenarios.

Under the mitigated scenario, predicted maximum SS elevation at H1, as well as both SS elevation and sedimentation flux at CR1 and CR2 would be reduced significantly (Table 7C.13 of Annex 7C). Maximum SS elevation at H1, as well as both maximum SS elevation and sedimentation flux at CR1 and CR2 is predicted to be below the corresponding WQO criteria for SS in both seasons. With the implementation of the proposed mitigation measures, no unacceptable SS impact on H1, CR1 and CR2 would be expected.

Jetting Scenario C03

In this scenario, one jetting machine was assumed to be working from BPPS Pipeline KP41.1 to 37.5, with working rate at 1,000 m day^-1 continuously for 24 hours throughout the simulation.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.5 of Annex 7C. Contour plots showing the maximum SS elevation throughout the simulation are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for most WSRs in both seasons. Elevation of SS was predicted at the Sha Chau and Lung Kwu Chau Marine Park (MPA-5) and its northwest corner (MPA-2). However, the elevation was predicted to be limited to a localized area given that other locations within the marine park (MPA-1, MPA-3 and MPA-4) did not show particularly high SS elevations in both seasons. To minimize the predicted elevation of SS at the Sha Chau and Lung Kwu Chau Marine Park, implementation of silt curtain around the jetting machine is recommended. Furthermore, adoption of two layers of silt curtain with combined silt removal efficiency of 80% reduction is also recommended in the vicinity of the marine park boundary near the jetting machine to further reduce the water quality impact.

With the implementation of the proposed mitigation measures, predicted maximum SS elevation at both the observation point (MPA-2) and WSR (MPA-5) of the Sha Chau and Lung Kwu Chau Marine Park would be below the corresponding WQO criteria for SS in both seasons (Table 7C.14 of Annex 7C). Therefore, no unacceptable SS impact on MPA-2 and MPA-5 would be expected.

Jetting Scenario C04

In this scenario, one jetting machine was assumed to be working from BPPS Pipeline KP31.5 to 21.3 with working rate at 1,500 m day^-1 continuously for 24 hours throughout the simulation.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.6 of Annex 7C. Contour plots showing the maximum SS elevation throughout the simulation are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for the majority of the WSRs in both seasons. Given that this section of the pipeline is located along the boundary of the Proposed AAHK 3RS Marine Park, modelling results indicated maximum SS elevation of up to 6.7 mg L^-1 was predicted in the wet season at MPB representing this WSR. The SS elevation was predicted to be transient (for about 0.1% of time). In addition, high sedimentation flux is also predicted at the coral colonies CR3 at Pak Chau as well as artificial reef at Sha Chau and Lung Kwu Chau AR1. The maximum sedimentation flux at AR1 is predicted at to be up to 503.2 and 452.1 g m^-2 day^-1 respectively in dry and wet seasons.

The Sha Chau and Lung Kwu Chau Marine Park (SCLKCMP) is located at the north end of the pipeline section. The modelling results indicated maximum SS elevation of up to 85.6 mg L^-1 in wet season at observation point MPA-3; and at AR1 with up to 12.9 mg L^-1 and 13.8 mg L^-1 in dry and wet season respectively. The SS elevation was limited to localized areas given that other locations within this marine park (MPA-1, MPA-2, MPA-4 and MPA-5) did not show high SS elevations. To minimize the predicted elevation of SS at the Sha Chau and Lung Kwu Chau Marine Park, implementation of silt curtain around the jetting machine is recommended to further reduce potential impacts to this marine park.

Mitigation measure in terms of working rate reduction of jetting machine from 1,500 m day^-1 to 720 m day^-1 from BPPS Pipeline KP31.5 to 26.2 is recommended. In the mitigated scenario, maximum SS elevation at MPA-3, AR1, CR3 and MPB, and sedimentation flux at AR1 and CR3, would comply with the corresponding criteria (Table 7C.15 of Annex 7C). It is therefore concluded no unacceptable SS impact would be expected for the pipeline jetting from BPPS Pipeline KP31.5 to 21.3 with the proposed mitigation measures.

Jetting Scenario C05

In this scenario, one jetting machine was assumed to be working from BPPS Pipeline KP15.6 to KP0.1, with working rate at 1,000 m day^-1 continuously for 24 hours throughout the simulation.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.7 of Annex 7C. Contour plots showing the maximum SS elevation throughout the modelled period are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for the majority of the WSRs in both seasons. However, this section of pipeline is in the vicinity of the southern boundary of the proposed Southwest Lantau Marine Park (SWLMP) and close to the southern boundary of the proposed South Lantau Marine Park (SLMP). High SS elevation and sedimentation flux are predicted in wet season at coral colonies CR6 on the south coast of South Soko within the SLMP, with maximum SS elevation of 12.2 mg L^-1 (with about 0.2% of time exceedance) and sedimentation flux of 500.4 g m^-2 day^-1 in the wet season.

Observation points along the southern boundary of the SLMP (MPD-2, MPD-3, MPD-4, MPD-5) were predicted to have high SS elevation ranging from 9.1 – 65.9 mg L^-1 in dry season to 13.1 – 70.0 mg L^-1 in wet season.

The modelling results also indicated maximum SS elevation up to 9.6 mg L^-1 and 20.2 m L^-1 in dry and wet seasons respectively at observation point MPC-3; up to 8.2 mg L^-1 in wet season at MPC-4 and up to 6.7 mg L^-1 in wet season at MPC-5 of SWLMP. However, the SS elevation was limited to localized area given that other locations within the SWLMP (MPC-1, MPC-2, MPC-7 and MPC-8) did not show particularly high SS elevations.

Mitigation measure in terms of silt curtain with silt removal efficiency of 85% surrounding jetting machine, as well as additional two layers of silt curtains with combined silt removal efficiency of 80% along the southern boundary of the South Lantau Marine Park (KP0.1-8.9), are recommended. With the implementation of mitigation measures, maximum SS elevations at the WSRs (MPD-9 and CR6) and observation points (MPC-3, MPC-4, MPC-5, MPD-2, MPD-3, MPD-4 and MPD-5) are predicted to be below the corresponding criteria in both seasons (Table 7C.16 of Annex 7C). Since there is no exceedance of WQO SS criteria predicted at the WSRs of the marine parks, coral location or other WSRs, it is concluded that no unacceptable water quality impact would be expected with the implementation of proposed mitigation measures.

Jetting Scenario C06

In this scenario, one jetting machine was assumed to be working from LPS Pipeline KP17.4 to 0.1. The jetting machine was assumed to be with working rate at 1,000 m day^-1 continuously for 24 hours from LPS Pipeline KP17.4 to 14.5, at 7,000 m day^-1 continuously for 24 hours from LPS Pipeline KP14.5 to 5.0, and at 720 m day^-1 continuously for 24 hours from LPS Pipeline KP5.0 to 0.1.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.8 of Annex 7C. Contour plots showing the maximum SS elevation throughout the modelled period are also provided in Annex 7C. Most of the section of pipeline is located in open waters and is relatively far away from the WSRs identified. From KP5.0 to 0.1, however, predicted maximum SS elevation at the WSR of the South Lantau Marine Park (MPD-9) was up to 5.1 mg L^-1 in dry season as well as at the eastern boundary of the SLMP up to 15.4 mg L^-1 at observation MPD-5 and 14.7 mg L^-1 at MPD-6. The SS plume was predicted to also encroach into the marine park and results in SS elevation at MPD-9 up to 5.1 mg L^-1 in dry season.

Mitigation measure in terms of silt curtain with silt removal efficiency of 85% surrounding jetting machine, as well as additional two layers of silt curtain with combined silt removal efficiency of 80% in the vicinity of the eastern boundary of the South Lantau Marine Park near the jetting machine (KP0.1-5.0), are recommended. With the implementation of mitigation measures, maximum SS elevations at the WSRs (MPD-9) and observation points (MPD-5 and MPD-6) are predicted to be below the corresponding criteria in both seasons (Table 7C.17 of Annex 7C). Since there is no exceedance of WQO SS criteria predicted at the WSRs of the marine parks, coral location or other WSRs, it is concluded that no unacceptable water quality impact would be expected with the implementation of proposed mitigation measures.

Jetting Scenario C07

In this scenario, one jetting machine was assumed to be working from BPPS Pipeline KP36.0 to 31.5. The jetting machine was assumed to be with working rate at 720 m day^-1 continuously for 24 hours throughout the simulation period.

Predicted maximum SS elevation from the jetting works and other concurrent projects is provided in Table 7C.9 of Annex 7C. Contour plots showing the maximum SS elevation throughout the modelled period are also provided in Annex 7C. Compliance with the corresponding assessment criteria for SS elevation and sedimentation flux is predicted for the majority of the WSRs in both seasons. However, elevation of SS level was predicted at the WSRs of Sha Chau and Lung Kwu Chau Marine Park as well as the observation point. High SS elevation at WSR AR1 and observation point MPA-3 was predicted (up to 8.7 mg L^-1 in dry season for AR1 with 0.1% of time exceedance; up to 47.6 mgL^-1 in dry season and 13.5 mg L^-1 in wet season for MPA-3 with ~0.5% of time exceedance). Sedimentation flux of up to 351.7 g m^-2 day^-1 was also predicted at AR1 in the dry season. Maximum SS elevation at CR3 was predicted to be up to 42.8 mg L^-1 and 91.9 mg L^-1 in dry season and wet seasons respectively and maximum sedimentation flux up to 1465.6 g m^-2 day^-1 and 2939.2 g m^-2 day^-1 in dry and wet seasons respectively.

Mitigation measure in terms of silt curtain with silt removal efficiency of 85% surrounding jetting machine, as well as additional two layers of silt curtain with combined silt removal efficiency of 80% along the western boundary of the SCLKCMP (KP31.5-36.0), are recommended. With the implementation of mitigation measures, maximum SS elevations and sedimentation flux at the WSRs (AR1 and CR3) and maximum SS elevation at observation point (MPA-3) are predicted to be below the corresponding criteria in both seasons (Table 7C.18 of Annex 7C). Since there is no exceedance of WQO SS criteria predicted at the WSRs of the marine park, coral location or other WSRs, it is concluded that no unacceptable water quality impact would be expected with the implementation of proposed mitigation measures.

Other Marine Construction Works

There are some other marine works to be carried out under this Project which have not been included specifically in the modelling scenarios assessed above. They are considered to result in minimum disturbance to the seabed and their impact can be evaluated under relevant marine dredging/jetting scenarios which have been quantitatively assessed. These marine works are summarized below in Table 7.12 below.

Table 7.12 Summary of Other Marine Works

Marine Works	Modelling Scenario Covered
De-burial and re-burial of about 100m of existing pipeline end section east of LPS Pipeline KP17.4	The relevant work area for the use of mass flow excavator would be in the immediate vicinity of jetting source 02_J_A under Scenario C06. Since the sediment loss from mass flow excavator is expected to be below that of sediment loss 02_J_A and the de-burial and re-burial will not be conducted at the same time as the jetting at 02_J_A, the worst case water quality impact from the use of mass flow excavator is considered covered under construction scenario C06. For the same reason, the subsequent re-burial of pipeline after tie-in by jetting is considered covered given the forward speed for that section does not exceed the forward speed by 02_J_A (i.e. 1,000 m day^-1).
Cofferdam construction and removal at Pipeline landfalls of the BPPS and the LPS (if needed *)	Past approved EIAs generally consider the potential disturbance to water quality by these marine construction activities negligible and quantitative assessment was not required. Quantitative assessment for such activity was conducted recently in the approved EIA of Expansion of Sha Tau Kok Sewage Treatment Works (AEIAR-207/2017), which estimated the potential sediment loss to the water column during the retrieval of sheetpiles after the completion of works behind cofferdam. Based on the approved EIA, the estimated sediment loss to the water column from the sheetpile retrieval activity would be very low. Given that dredging at both pipeline shore approaches at BPPS and LPS have been modelled (as sediment sources 01_G and 13_G under Scenarios C01A, C01B and C01C), the potential worst case impact on water quality would be assessed covering the proposed pipeline landfall construction works as well.
Placement of Rock Armour along the Pipeline Section	Rock would be placed above the pipelines for protection for all section of pipelines. It should be noted that the placement of rock armour will be controlled to ensure the rock is placed at the right location for appropriate level of protection. Therefore, the level of disturbance to seabed from the placement works would be limited. Furthermore, rock armour contains negligible amount of fine contents and is not expected to result in notable change in water quality which exceeds the level predicted for pipeline trenching works. Given water quality modelling assessment was conducted covering the trenching works for the entire pipelines and the rock armour placement works for each section would only be conducted after the completion of dredging / jetting works for that specific section, it is concluded that the potential change in water quality due to rock armour placement has been covered.

* In the event that the pre-installed pipeline cannot be used for the LPS tie-in, an alternative landfall point will be used

As assessed above in Section 7.7.1, elevation of SS at WSRs near the pipeline alignment is predicted under unmitigated scenarios, particularly for jetting scenarios next to the existing and proposed marine parks. Jetting works undertaken next to the marine park boundary is predicted to result in elevated level of SS for a short period of time, and would return to lower level as the jetting machine moves away from the marine parks. In general, potential water quality impact only occurs for a limited period of time, as shown in the high percentage time compliance of the SS criteria in Annex 7C. The same applies to other WSRs in the vicinity, such as identified coral locations. Mitigation measures including implementation of silt curtain at sediment sources (grab dredgers and jetting machine), reduction of working rates as well as silt curtain at WSRs are recommended to reduce the potential SS impact in the receiving waters and nearby WSRs. Full compliance in terms of SS elevation and sedimentation flux at all WSRs is predicted under the mitigated scenarios. No unacceptable water quality impact on the nearby WSRs identified, including but not limited to the existing, planned or potential Marine Parks, corals, secondary contact recreation subzones, potential water sports activities, beaches, marine mammal habitat, horseshoe crab breeding ground, amphioxus, green turtle and seawater intake points, etc., is expected for all modelled scenarios as well as the minor marine construction works.

Excavated sediment from dredging operations would be transported and disposed at appropriate sediment disposal facilities. Appropriate measures, as stated in Section 7.9.1, would be implemented to control any potential water quality impact associated with the transportation and disposal of excavated sediment. Further considerations on the disposal of sediment are detailed in Annex 7B. It should be highlighted that both the Open Sea Disposal Area at South Cheung Chau as well as the Contaminated Mud Marine Disposal Facility at Airport East / East Sha Chau Area has been taken into account in the modelling exercise as concurrent project for this Study. The potential water quality impact from the disposal of excavated sediment from this Project has been taken into account in the water quality modelling assessment and no unacceptable impacts on water quality is expected.

The use of silt curtain has been recommended in the pipeline construction scenarios to reduce sediment dispersion from grab dredging and jetting, as well as to protect nearby WSRs from sediment plume. In general, silt curtain would be mounted on floats with weights attached at the bottom rim to ensure sufficient coverage of the water column and the silt curtain would be effective in reducing water quality impacts close to the seabed. The vertical depth and other settings of the silt curtain would be appropriately adjusted onsite to accommodate for water depth and other local conditions to avoid disturbing the seabed. For the cage type silt curtain enclosing the jetting machine, the contractor will deploy the cage type silt curtain with care to avoid any dragging of the silt curtain on the seabed. Deployment of the silt curtain will be checked regularly to reduce secondary impact on water quality. Given that the forward speed for jetting machine and the associated silt curtain enclosing it is generally low near sensitive areas such as marine park (720 m day^-1 for 24 hrs is equivalent to 30 m hr^-1 or 0.5 m min^-1), disturbance to seabed, if any, would be very limited. As such, no unacceptable secondary water quality impact associated with the deployment of silt curtain under this Project would be anticipated. Construction phase water quality monitoring, which is detailed in the EM&A Manual, would be conducted to ensure no unacceptable water quality impact at nearby WSRs from the construction works under this Project.

Dissolved Oxygen (DO) Depletion

The degree of DO depletion exerted by a sediment plume is a function of the sediment oxygen demand of the sediment, its concentration in the water column and the rate of oxygen replenishment. The impact of the sediment oxygen demand on DO concentrations has been calculated based on the following equation:

DO (mg O₂ L^-1) = DO (g O₂/m³) = SS (g DW/m³) × fraction of organic matter in sediment (g C/g DW) × 2.67 (g O₂/gC)

The assumption behind this equation is that all the released organic matter is eventually re-mineralized within the water column. This leads to an estimated depletion with respect to the background DO concentrations. This DO depletion depends on the quality of the released sediments, i.e. on the percentage of organic matter in the sediment. The fraction of organic matter in sediment (Chemical oxygen demand in Table 7.5) was taken as 15,342 mg kg^-1 with reference to EPD Marine Monitoring data shown in Table 7.5 as a representative value for sediments within the Study Area. Maximum SS elevation predicted among the marine construction scenarios (mitigated if applicable) at each WSRs was adopted for the estimation. The predicted maximum DO depletion are provided in Annex 7D.

Among all WSRs, maximum DO depletion of 0.2 mg L^-1 are predicted among all construction scenarios, which are quite low and no exceedances are predicted. In view of the above, unacceptable depletion of DO from the marine construction works is not expected.

Release of Sediment-bounded Contaminants

As discussed in Section 7.3.6, results of elutriate tests from past EIA studies as well as under this Study indicate the tendency for release of sediment-bounded pollutants, including metals, metalloids and organic contaminants is low. Some past elutriate test results ([24]) for Silver and total PAHs exceeded the proposed assessment criteria; however, other elutriate test results ([25]) ([26]) as well as the elutriate test conducted under this Study all showed that contaminant levels would be below the proposed assessment criteria. Further analysis is therefore not required for these two parameters.

For other elutriate test results from past EIAs, exceedance with the proposed assessment criteria was observed for Arsenic and Mercury (refer to Annex 8A for testing results). For Arsenic, the maximum concentration recorded was about 2 times of the corresponding assessment criteria. For Mercury, the maximum concentration recorded was only about 3 times of the corresponding assessment criteria.

Results of elutriate test conducted under this Study is provided in Annex 7A. These results were taken into account in the tracer dispersion modelling for determining the potential release of contaminants during dredging/jetting works under this Project. The modelling approach and the results are described in Annex 7E.

Based on the modelling results and predictions, no unacceptable elevation of any sediment-bounded contaminants is expected at the representative WSRs in both dry and wet seasons.

Release of Sediment-bounded Nutrients

As shown in Annex 7A, elevated concentration of total nitrogen (TN) and ammonia nitrogen (NH₃-N) was generally observed in elutriate results when compared with the seawater blanks. A comparison of TN and NH₃-N levels for various pipeline sections is provided in Table 7.13.

Table 7.13 Comparison of Total Nitrogen and Ammonia Nitrogen Levels in Elutriate and Seawater Blank for Various Pipeline Sections

		Pipeline Sections
		Urmston Road	West of Sha Chau & Lung Kwu Chau Marine Park	Southwest of Lantau	Soko Island	LPS Pipeline
Sampling Stations (Blank Stations)		B-GB01 to B-GB03 (B-GB02)	B-GB04 to B-GB08, B-EL01 to B-EL05 (B-EL02)	B-GB09 to B-GB18 (B-GB12)	B-EL06 to B-EL11 (B-EL08)	L-EL01 to L-EL14 (L-EL09)
Maximum TN (mg L^-1)	Elutriate ⁽¹⁾	2.48	2.43	4.27	1.87	1.43
	Blank ⁽²⁾	1.74	1.81	1.10	0.70	0.58
	Elevation	0.74	0.62	3.17	1.17	0.85
	Mass released per unit Sediment Loss (mg kg^-1)	4.23	3.54	18.11 ⁽⁵⁾	6.69	4.86
Maximum NH₃-N (mg L^-1)	Elutriate ⁽³⁾	0.37	0.56	2.31	0.54	0.58
	Blank ⁽⁴⁾	0.13	0.09	0.08	0.09	0.06
	Elevation	0.24	0.47	2.23	0.45	0.52
	Mass released per unit Sediment Loss (mg kg^-1)	1.37	2.69	12.74 ⁽⁵⁾	2.57	2.97

Note:

(1) Sum of Total Kjeldahl Nitrogen, Nitrate-N and Nitrite-N. If Nitrite-N <0.05 mg/L, TN is calculated assuming Nitrite-N as 0.05 mg/L for conservative assessment.

(2) Sum of Total Kjeldahl Nitrogen, Nitrate-N and Nitrite-N. If Nitrite-N <0.05 mg/L, TN is calculated assuming Nitrite-N as 0 mg/L for conservative assessment.

(3) Sum of Ammonia Nitrogen, Nitrate-N and Nitrite-N. If Nitrite-N <0.05 mg/L, TN is calculated assuming Nitrite-N as 0.05 mg/L for conservative assessment.

(4) Sum of Ammonia Nitrogen, Nitrate-N and Nitrite-N. If Nitrite-N <0.05 mg/L, TN is calculated assuming Nitrite-N as 0 mg/L for conservative assessment.

(5) The highest mass released per unit sediment loss of TN and NH₃-N are shown in bold.

Tracer dispersion modelling is conducted to predict the elevation of nutrients at the WSRs based on the results of sediment elutriate test conducted under this Study. The modelling approach and the results are described in Annex 7E.

As presented in Annex 7E, given there would only be small/negligible contribution in the elevation of TIN and UIA due to marine dredging/jetting works to the criteria and ambient level, no unacceptable water quality impact on the WSRs would be expected.

7.7.2 Marine Vessel Discharges

Construction vessels have the potential for the following liquid discharges:

· Uncontaminated deck drainage;

· Potentially contaminated drainage from machinery spaces; and

· Sewage/grey water.

Deck drainage is likely to be uncontaminated and is not likely to impact water quality. Other sources of possible impacts to water quality may arise from discharges of hydrocarbons (oil and grease) from machinery space drainage and biochemical oxygen demand (BOD) and microbiological constituents associated with sewage/grey water. These waste streams are all readily amenable to control as part of appropriate practice on vessels. Possible impacts associated with construction vessel discharges are therefore considered to be negligible.

No solid wastes will be permitted to be disposed of overboard by vessels during construction works, thus impacts from such sources would be minimal.

7.7.3 Subsea Pipeline Hydrotesting

Hydrotesting would be required to check the integrity of the subsea pipelines([27]). An assessment of the impacts from pipeline hydrotest discharges is undertaken. At the time of preparing this EIA, information provided by CLP and HKE suggested that that seawater added with a ‘cocktail’ compound (acting as an oxygen scavenger, bactericide and corrosion inhibitor all-in-one; such as WFT9371 from Weatherford, or equivalent, subject to final engineering design), would be used for hydrotesting. This compound is known to be of very low toxicity, and a discharge concentration of ≤ 10 mg L^-1 is expected which is significantly below the No Observable Effect Concentration (NOEC) of 500 mg L^-1 (material safety data sheet provided in Annex 7J). Therefore, toxicity-related water quality impact would not be expected from the discharge of hydrotest water.

The compound also contains up to 30% of sodium metabisulphite (Na₂S₂O₅), which has the potential to consume dissolved oxygen in the marine waters when discharged. The complete oxidation of sodium metabisulphite is illustrated in the chemical equation below:

Na₂S₂O_5
(aq) + O_{2 (aq)} + H₂O_(l) à 2NaHSO₄ _(aq)

Each molecule of sodium metabisulphite (molecular mass = 190.107 g mol^-1) reacts with one molecule of oxygen (molecular mass = 31.999 g mol^-1). The potential maximum depletion of dissolved oxygen from 10 mg L^-1 compound discharge would be calculated below:

The maximum DO depletion from the discharge of the compound at less than 10 mg L^-1 would, therefore, be about 0.505 mg L^-1, which is below the allowed DO depletion (2.1 and 0.9 mg L^-1 respectively in dry and wet seasons) at the nearest EPD marine water quality monitoring station SM17. Full compliance with the DO WQO would be expected at the point of discharge at the Jetty. Results of near field dispersion modelling (detailed under Annex 7F) indicated that further dispersion and dilution (reaerate not taken into account) would reduce the concentration of the chemical to one-ninth of discharge concentration before reaching the nearest WSR (proposed South Lantau Marine Park) thus potential impact on the nearest WSR would be negligible. Potential impacts to WSRs further afield would be even lower. No unacceptable water quality impact from the discharge of hydrotest water is thus expected.

7.7.4 Runoff from Land-based Work Sites

Minor land-based construction works would be required at the pipeline landing locations at the BPPS and the LPS, including minor trenching and gas pipeline installation works. Small-scale piping and equipment installation works would also be required for the GRS at the BPPS, GRS at the LPS and Jetty topside. Discharges and runoff from the sites during these construction and installation activities may contain suspended solids which could be a source of water pollution. Considering the small scale and extent of such activities and with proper implementation of the mitigation measures (Section 7.9.1), it is anticipated that no adverse water quality impacts would arise from the land-based works.

All land-based construction works would be conducted in either the BPPS or the LPS, where there is no water courses, natural streams, ponds and wetlands. Therefore there would not be any alternation of water courses, natural streams, ponds, wetlands, change of catchment types or areas, erosion or sedimentation due to the Project.

7.7.5 Sewage Discharges

Sewage will arise from the construction workforce and site office’s sanitary facilities. It is estimated that the average number of workers working onsite is about 200-300. Based on the general effluent generation rate (150L per worker per day ([28]), approximately 30,000 - 45,000L of effluent will be generated at the site during the construction phase. To accommodate the increase in sewage effluent from construction workforce, suitable sanitary facilities such as chemical toilets would be provided onsite. These chemical toilets would be regularly maintained and cleaned by licensed contractor to avoid any environmental nuisance. No onsite discharge from these chemical toilets would be allowed. Therefore, no unacceptable water quality impacts to sensitive receivers are anticipated.

7.8 Impact Assessment – Operation Phase

7.8.1 Discharge of Cooled Seawater with TRC from the FSRU Vessel

Seawater will be used in the LNG regasification process at the FSRU Vessel to ‘heat up’ the LNG and consequently seawater cooler than ambient will be discharged from the FSRU Vessel to the marine environment. Based on the latest design information, cooled water generated from the regasification process is expected to be at a maximum 9°C below the water temperature at the intake. The design maximum flow rate for cooled water discharge would be 20,000 m³ hr^-1.

The change in seawater temperature due to cooled water discharge has been modelled using CORMIX (for nearfield dispersion) and Delft3D FLOW module (for far field dispersion). The predicted vertical profile of the cooled water plume from CORMIX (detailed in Annex 7F) has been adopted into the far field hydrodynamic model in Delft3D FLOW to simulate the representative conditions for the dry and wet seasons.

The predicted change in seawater temperature at the nearest observation point (proposed South Lantau Marine Park; MPD-5 which represents its southeast corner about 200m away from the discharge outfall at the FSRU Vessel) and WSR (MPD-9 which represents the centre of the proposed South Lantau Marine Park) in the dry and wet seasons are presented in Table 7.14. Contour plots of typical plume of cooled water flowing towards MPD-5 in flood tide (worst tidal condition) are provided in Annex 7G. The predicted changes in temperature at the nearest observation point and WSR are expected to be significantly below the WQO criteria of ± 2°C. No unacceptable change in water temperature at the nearest WSR is expected. Potential impacts to the identified WSRs further away would be even lower.

Table 7.14 Predicted Temperature at the Nearest Observation Point and WSR for Proposed South Lantau Marine Park (MPD-5 and MPD-9) with and without Cooled Water Discharge from the FSRU Vessel

Note: values represent seawater temperature at the same water depth as the discharge outfall, i.e. about 9-10 m below water surface. The change in depth-averaged water temperature (representing the entire water column) would be even lower.

Other than the potential decrease in water temperature from the discharge of cooled water, modelling simulation has also been conducted to predict the impact from the discharge of total residual chlorine (TRC) from the electrochlorination process of the regasification system. Electrochlorination would be conducted to introduce chlorine in the open rack vaporizers to control biofouling, and the maximum TRC level would be 0.5 mg L^-1 in the discharge effluent. The predicted levels of TRC at the nearest observation point MPD-5 are presented in Table 7.15. Contour plots showing the average and maximum TRC levels are provided in Annex 7G. The predicted levels of TRC at MPD-5 are quite low and are all well below the corresponding assessment criteria of 0.02 mg L^-1. No unacceptable impact from the discharge of TRC is expected.

Table 7.15 Predicted TRC at the Nearest Observation Point and WSR for Proposed South Lantau Marine Park (MPD-5 and MPD-9) associated with Cooled Water Discharge from the FSRU Vessel

TRC (mg L^-1)	Dry Season	Wet Season
Assessment Criteria	0.02	0.02
MPD-5
Average	0.00014	0.00010
Maximum	0.00057	0.00046
MPD-9
Average	<0.00001	<0.00001
Maximum	0.00003	0.00006

7.8.2 Discharge of Concentrated Seawater and Treated Effluent from the FSRU Vessel

A freshwater generator will be provided on board the FSRU Vessel to provide potable water for staff onsite. The seawater intake rate and freshwater production rate are about 3,360 m³ day^-1 and 60 m³ day^-1 respectively, i.e. concentrated seawater would be discharged at about 3,300 m³ day^-1. The freshwater generator would employ vacuum distillation for freshwater production and no chemical additive is expected to be used for its normal operation.

Salinity elevation estimated based on mass balance method ([29]) indicates salinity elevation would be less than 2% at discharge, which is below the corresponding WQO criteria of 10%, therefore no unacceptable change in salinity due to freshwater generation is expected. Low level of waste heat from the vacuum distillation process would be discharged into the sea through the concentrated seawater. However, given there is a much higher cooled water discharge from the regasification unit ([30]), the thermal impact from the concentrated seawater is expected to be eliminated soon after discharge. No unacceptable water quality impact would be expected from the discharge of concentrated seawater from the freshwater generator.

Based on the latest design information, sewage generated by staff onsite would be collected for onsite treatment by a sewage treatment unit at the FSRU Vessel. It is expected there will be about 48 staff working and staying at the jetty. Typical sewage loading under such conditions ([31]) is 0.3 m³ day^-1 per person and the corresponding design treatment capacity for sewage treatment unit is 14.4m³ day^-1. The quality of treated sewage effluent from the onsite sewage treatment unit is expected to comply with the corresponding WPCO discharge standards for effluents discharged into the marine waters of Southern WCZ subject to the conditions of the relevant licence. Near field dispersion modelling has been conducted to assess the impacts from the discharge of treated sewage effluent based on the said volume and standards. Results of the near field dispersion modelling are detailed in Annex 7F.

Results indicate the impacts of the discharge of treated effluent are negligible and would comply with the corresponding assessment criteria at the nearest WSR (and others that are further away). No unacceptable water quality impact from the discharge of treated sewage effluent is therefore expected.

7.8.3 Other Effluent Discharges from the FSRU Vessel and LNGC

For first arrival of the FSRU Vessel at the LNG Terminal, it will be loaded with LNG cargo and hence without ballast water, thus no ballast water will be discharged from the FSRU Vessel into Hong Kong waters. The FSRU Vessel would be moored at the Jetty during normal operation and ballast water would be taken in and out according to operating conditions of FSRU Vessel. Considering this operational condition, no unacceptable water quality impact from the intake and subsequent discharge of ballast water from the FSRU Vessel would be expected.

No discharge of ballast water from LNGCs into Hong Kong waters is also expected since LNGCs would arrive at the LNG Terminal with LNG cargo and thus without ballast water. During the LNG Unloading and Loading operations, ballast water will be taken on-board the LNGCs from the surrounding sea and pumped into its double hull ballast tanks to compensate for the LNG cargo unloading process. Considering this operational condition, no unacceptable water quality impact would be expected.

Minor wastewater discharges including seawater/rain deck drains ([32]), engine cooling water, other waste waters such as wastewater / chemical waste/bilge water generated from the LNG Terminal operation will be stored in storage tank(s) on board and discharged into a barge for handling ashore by licensed contractor(s). Measures would be put in place to ensure the management and control of day-to-day activities at the LNG Terminal that involve the use of potentially contaminating materials, such as fuel and lube oils. For example, it is expected that containment bunds and appropriate drainage system would be provided where necessary (e.g. where lube oil or other chemicals would be used or stored) to collect seawater/rain deck drains. These measures are presented and discussed in Section 7.9. The measures will ensure that surrounding marine waters are not affected by contaminants in run-off from the site. Consequently no unacceptable impact to water quality is expected.

7.8.4 Accidental Spill Events

There are a number of substances involved in the Project operation which carry risk of spillage. These include LNG, chemicals / dangerous goods as well as fuel of LNGC.

LNG handled in the FSRU Vessel and LNGC vaporizes at ambient temperature ([33]). In case of any spillage, the spilled LNG would quickly vaporized and would not leave any significant trace of the spill. In view of the above, no unacceptable water quality impact associated with any LNG spillage from the operation of the LNG Terminal would be expected.

There will be limited amount of chemicals stored in the FSRU and LNGC for the maintenance of the facilities (such as lube oil) as well as for operation of equipment on board. These chemicals will only be stored in bunded areas to contain any potential spillage. Appropriate clean up kits should be provided onsite to facilitate any required clean up action in case of any spillage onboard. Electrochlorination will be adopted and no storage of chlorine will be required. In view of the limited amount of chemical storage onboard, the above preventive measures are considered sufficient to control any potential spillage of chemicals onboard. No unacceptable water quality impact from spillage of storage chemicals would be expected.

Though extremely unlikely, the major spillage event during Project operation would be the spillage of LNGC fuel in case of vessel collision. It should be highlighted that LNGCs are large and (relatively) slow-moving vessels which is unlikely to be omitted by other marine vessels (which results in a collision). Furthermore, modern LNGCs are equipped with special design to prevent the fuel from leaking into the sea. Fuel for propulsion and ship services is carried in storage tanks installed inside double hulls, which further protect against collision. Some modern LNGCs even use LNG as fuel, which essentially eliminate any potential risk of LNGC fuel spillage and the associated water quality impact.

It is considered that a spillage of LNGC fuel is highly unlikely given the above. However, the EIA Study Brief requires that a potential scenario to be examined. A hypothetic worst-case scenario for LNGC fuel spillage was modelled and assessed below to provide indication on how such a spill would disperse to advise the arrangement for spill containment and clean-up effort.

Temperature (°C)	Dry Season			Wet Season
Temperature (°C)	Baseline	Project	Change	Baseline	Project	Change
WQO Criteria	-	-	>±2	-	-	>±2
MPD-5
Minimum	19.02	18.92	-0.10	21.88	21.68	-0.20
Average	19.29	19.27	-0.02	22.42	22.37	-0.07
MPD-9
Minimum	19.07	19.07	<-0.01	21.84	21.84	<-0.01
Average	19.38	19.38	<-0.01	22.57	22.57	<-0.01

In the model, it is assumed the event leading to a spillage occurred when a LNGC approaches to the Jetty from the south and 60% of the maximum tank contents of LNGC of tank capacity (up to 6,700m³) were spilled. The event leading to the spillage was assumed to occur in spring tide to capture the potential maximum distance travelled by the oil patches within the several initial hours of the spill. This is to allow the worst-case assessment in terms of spill containment and clean-up effort. Modelling of spillage at high and low water was conducted separately to assess the maximum range oil patches can reach in a full ebb (for spill during high water) and flood (for spill during low water) tide. Detailed considerations and assumptions for the spill modelling were provided in Annex 7B.

Results of the modelling prediction are detailed in Annex 7I. In dry season, the modelling results indicate oil patches released would move west or southwest, pass through the south of Soko Island in 4 to 8 hours. Oil patches would then move southwest further and exit the southwest marine boundary of Hong Kong in 8 to 12 hours. In wet season, the movement pattern of oil patches is less consistent. Spillage which occurs within 5 hours after high water would likely result in oil patches moving southeast and exiting the southern boundary of HKSAR waters in about two hours. For spillage that occurs in the rest of the period, oil patches would likely stay within the marine boundary of HKSAR for longer period of time and may reach coastline of Soko Island, Shek Kwu Chau, South Lantau, Cheung Chau, Hei Ling Chau, South of Lamma. A summary of the shortest time required for oil patches to reach these shorelines are summarized below in Table 7.16.

Table 7.16 Predicted Shortest Travel Time of Oil Patches to Reach Nearby Shorelines

Shorelines	*Minimum Hour Traveled*
Soko Island	4
Shek Kwu Chau	8
South Lantau	8
Cheung Chau	12
Hei Ling Chau	16
Lamma Island	36

With regards to the location of the proposed South Lantau Marine Park (SLMP), as shown in Annex 7I, oil patches could reach the proposed SLMP within the first two hours after the spill. Based on the results of the modelling, it is recommended in both seasons contingency actions for containing the oil patches should be implemented immediately to ensure oil patches would not spread into the nearby SLMP or impact any nearby shoreline.

7.8.5 Maintenance Dredging at the LNG Terminal

Maintenance dredging using one grab dredger may be required at the LNG Terminal once every about five years (subject to site condition) to maintain sufficient clearance for safe navigation of the LNGCs. For the purpose of this assessment, water quality modelling has been conducted to evaluate the potential elevation of SS at the nearby WSR. Since the dredging works would be remote from most WSRs, an assessment of the predicted maximum SS elevation at the nearest observation point of the proposed South Lantau Marine Park MPD-5 was made. Also, the only major marine works identified nearby is the open sea disposal at South Cheung Chau Disposal Site and the sediment loss from this project has been taken into account in the sediment plume modelling exercise. Maintenance dredging was assumed to be conducted using one grab dredger working at a rate of 5,500 m³ day^-1 (24 hours each day) with the use of a single layer of silt curtain with silt removal efficiency of 75% reduction.

A summary of predicted maximum SS elevation at MPD-5 is provided in Table 7.17. Contour plots showing the maximum and average instantaneous SS elevation throughout the modelled spring-neap cycle in dry and wet seasons are provided in Annex 7H. The predicted maximum SS elevation at MPD-5 would be below the corresponding WQO criteria in both seasons. Elevation of SS at other WSRs further away would be much lower.

No unacceptable water quality impact from maintenance dredging would be expected.

Table 7.17 Predicted Maximum Elevation in Suspended Solid at the Nearest Observation Point of Proposed South Lantau Marine Park MPD-5 from Operation Phase Maintenance Dredging near the LNG Terminal

Sensitive Receivers	Model Output Location	SS Elevation (mg L^-1)
		Dry Season		Wet Season
		Allowable Increase	Max. Increase	Allowable Increase	Max. Increase
Marine Park (Depth-averaged)
Proposed South Lantau Marine Park	MPD-5	3.8	1.1	3.1	0.6

7.9 Mitigation Measures

7.9.1 Construction Phase

Marine Construction Works

To minimise potential water quality impacts from elevated SS due to the proposed dredging and jetting works, the following mitigation measures are recommended (Figure 7.6):

Table 7.18 Summary of Mitigation Measures for Pipeline Construction Works

Work Location	Plants Involved	Allowed Maximum Work Rate	Silt Curtain at Plants	Silt Curtain at WSRs
LPS Pipeline
Pipeline shore approach at LPS (KP17.4-18.2)	1 Grab Dredger	1,600 m³ day^-1 for 24 hours each day	Yes	Not required
West Lamma Channel (KP14.5-17.4)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Not required
South of Shek Kwu Chau to West Lamma Channel (KP5.0 - 14.5)	1 Jetting Machine	7,000 m day^-1 for 24 hours each day	Yes	Not required
Double Berth Jetty to South of Shek Kwu Chau (KP0.1 - 5.0)	1 Jetting Machine	720 m day^-1 for 24 hours each day	Yes	Two layers at Eastern Boundary of the Proposed South Lantau MP (KP0.1-5.0)
Pipeline Riser Sections at Double Berth Jetty
Pipeline Riser (KP0.0 – 0.1 for both pipelines)	1 Grab Dredger	8,000 m³ day^-1 for 24 hours each day	Yes	Not required
BPPS Pipeline
Jetty Approach (KP0.1 – 5.0)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Two layers at Southern Boundary of the Proposed South Lantau MP (KP0.1-8.9)
South of Soko Islands (KP5.0 – 8.9)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes
Southwest of Soko Islands (KP8.9 - 12.1)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Not required
Adamasta Channel (KP12.1 - 15.6)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Not required
Southwest Lantau (KP15.6 - 21.3)	2 Grab Dredgers	Total 16,000 m³day^-1 for 24 hours each day 8,000 m³ day^-1 for each plant	Yes	Not required
Southwest Lantau (KP15.6 - 21.3)	1 TSHD (Alternative)	57,600 m³ day^-1 for 24 hours each day	Not required	Not required
West of Tai O to West of HKIA (KP21.3 – 31.5)	1 Jetting Machine	1,500 m day^-1 for 24 hours each day from KP KP26.2 to 21.3 720 m day^-1 for 24 hours each day from KP31.5 to 26.2	Yes	Not required
Sha Chau to Lung Kwu Chau (KP31.5 – 36.0)	1 Jetting Machine	720 m day^-1 for 24 hours each day	Yes	Two layers at Western Boundary of the Sha Chau and Lung Kwu Chau MP (KP31.5-36.0)
Sha Chau to Lung Kwu Chau (KP36.0 - 37.5)	1 Grab Dredger	8,000 m³ day^-1 for 24 hours each day	Yes	Not required
Lung Kwu Chau to Urmston Anchorage (37.5 - 41.1)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Two layers at NW corner of Sha Chau and Lung Kwu Chau MP (KP37.5-41.1)
Urmston Road (KP41.1 – 42.9)	1 Grab Dredger	8,000 m³ day^-1 for 24 hours each day	Yes	Not required
Urmston Road (KP41.1 – 42.9)	1 TSHD(Alternative)	64,800 m³ day^-1 for 24 hours each day	Not required	Not required *
West of BPPS (KP42.9 - 44.9)	1 Jetting Machine	1,000 m day^-1 for 24 hours each day	Yes	Two layers at CR1, CR2
Pipeline shore approach at BPPS (KP44.9 - 45.0)	1 Grab Dredger	1,500 m³ day^-1 for 24 hours each day	Yes	Two layers at CR1, CR2

* As shown in Annex 7C, the predicted sediment plume from grab dredging/ TSHD at this section would not reach CR1 and CR2 at the BPPS seawall, therefore additional silt curtain at CR1 and CR2 is not required.

In addition, the following have been taken into account when considering the mitigation measures:

· Grab dredging can be conducted concurrently with one TSHD.

· One jetting machine can be working on each pipeline.

· Cofferdam construction and removal at pipeline landfalls of the BPPS and the LPS (if needed) should not be conducted concurrently with the nearby pipeline dredging sections (BPPS Pipeline KP44.9 - 45.0 and LPS Pipeline KP17.4 - 18.2). Silt curtain surrounding the works areas for cofferdam construction and removal at pipeline landfalls of the BPPS and the LPS should also be implemented.

Silt curtains shall be formed from tough, abrasion resistant, permeable membranes, suitable for the purpose, supported on floating booms in such a way as to ensure that the sediment plume shall be restricted to within the limit of the works area. The silt curtain shall be formed and installed in such a way that tidal rise and fall are accommodated, with the silt curtains always extending from the surface to the bottom of the water column and held with anchor blocks. Schematic diagrams on silt curtain deployment are provided in Figures 7.4 and 7.5. The contractor shall regularly inspect the silt curtains and check that they are moored and marked to avoid danger to marine traffic. Regular inspection on the integrity of the silt curtain should be carried out by the contractor and any damage to the silt curtain shall be repaired by the contractor promptly. Relevant marine works shall only be undertaken when the repair is fixed to the satisfaction of the engineer.

Furthermore, the following standard measures and good site practices are recommended to be implemented to avoid/minimise the potential impacts from marine construction:

· All vessels should be well maintained and inspected before use to limit any potential discharges to the marine environment;

· All vessels must have a clean ballast system;

· No overflow is permitted from the trailing suction hopper dredger and the Lean Mixture Overboard (LMOB) system will only be in operation at the beginning and end of the dredging cycle when the drag head is being lowered and raised;

· Dredged marine mud will be disposed of in a gazetted marine disposal area in accordance with the Dumping at Sea Ordinance (DASO) permit conditions;

· Disposal vessels will be fitted with tight bottom seals in order to prevent leakage of material during transport;

· Barges will be filled to a level, which ensures that material does not spill over during transport to the disposal site and that adequate freeboard is maintained to ensure that the decks are not washed by wave action;

· After dredging, any excess materials will be cleaned from decks and exposed fittings before the vessel is moved from the dredging area;

· When the dredged material has been unloaded at the disposal areas, any material that has accumulated on the deck or other exposed parts of the vessel will be removed and placed in the hold or a hopper. Under no circumstances will decks be washed clean in a way that permits material to be released overboard. Dredgers will maintain adequate clearance between vessels and the seabed at all states of the tide and reduce operations speed to ensure that excessive turbidity is not generated by turbulence from vessel movement or propeller wash; and

· Marine works shall not cause foam, oil, grease, litter or other objectionable matter to be present in the water within and adjacent to the works site. Wastewater from potentially contaminated area on working vessels should be minimized and collected. These kinds of wastewater should be brought back to port and discharged at appropriate collection and treatment system; and

· No solid waste is allowed to be disposed overboard.

Land-based Construction Works

As the works are next to the shoreline, infiltration of seawater during excavation is anticipated. Appropriate infiltration control, such as cofferdam wall, is recommended to be adopted to limit groundwater inflow to the excavation works areas. Groundwater pumped out from excavation area should be discharged into the storm system via silt removal facilities.

Standard site practices outlined in ProPECC PN 1/94 “Construction Site Drainage” will be followed as far as practicable in order to reduce surface runoff, minimise erosion, and also to retain and reduce any SS prior to discharge. These practices include the following:

· Silt removal facilities such as silt traps or sedimentation facilities will be provided to remove silt particles from runoff to meet the requirements of the TM standard under the WPCO. The design of silt removal facilities will be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and sediment control structures will be inspected on a regular basis and maintained to confirm proper and efficient operation at all times and particularly during rainstorms. Deposited silt and grit will be removed regularly.

· Earthworks to form the final surfaces will be followed up with surface protection and drainage works to prevent erosion caused by rainstorms.

· Appropriate surface drainage will be designed and provided where necessary.

· The precautions to be taken at any time of year when rainstorms are likely together with the actions to be taken when a rainstorm is imminent or forecasted and actions to be taken during or after rainstorms are summarised in Appendix A2 of ProPECC PN 1/94.

· Oil interceptors will be provided in the drainage system where necessary and regularly emptied to prevent the release of oil and grease into the storm water drainage system after accidental spillages.

· Temporary and permanent drainage pipes and culverts provided to facilitate runoff discharge, if any, will be adequately designed for the controlled release of storm flows.

· The temporary diverted drainage, if any, will be reinstated to the original condition when the construction work has finished or when the temporary diversion is no longer required.

· Appropriate numbers of chemical toilets shall be provided by a licensed contractor to serve the construction workers over the construction sites to prevent direct disposal of sewage into the water environment. No onsite discharge from these chemical toilets would be allowed.

Discharge of Hydrotest Water

Given that no unacceptable water quality impact would be expected due to the use of the proposed chemical for hydrotesting of pipelines, therefore no mitigation measures would be required.

A detailed hydrotesting procedure will be developed during the implementation stage of the Project that will detail how the process will be carried out, how it will be carefully controlled and monitored, and how the discharge of hydrotesting water will be managed.

7.9.2 Operation Phase

Modelling assessment for operation phase cooled water and TRC discharge indicated that no unacceptable water quality impact would be expected from the operation of the proposed LNG Terminal. Also, no unacceptable impact would be expected from the discharge of concentrated seawater as well as treated sewage effluent from the Project in view of the low salinity elevation and low discharge rate. No mitigation measures would be required.

For maintenance dredging at the LNG Terminal, mitigation measures in form of controlled dredging rate (maximum of 5,500 m³ day^-1) as well as silt curtain should be implemented for the control of sediment dispersion and the protection of the nearby WSRs. Applicable control measures related to construction phase marine works as stated in Section 7.9.1 would also be implemented.

The additional risk associated with accidental fuel spill from the operation of the LNG Terminal is expected to be minimal. Design features such as shutdown valves and leak detectors are also included to avoid and minimise potential fuel leak. A project-specific contingency plan will be prepared including protocols for avoidance, containment, remediation and reporting accidental spill event. No additional water quality mitigation measure is required.

7.10 Residual Impact

7.10.1 Construction Phase

With the implementation of proposed mitigation measures, it is predicted that the maximum SS elevation and sedimentation, as well as DO levels at all WSRs would be in compliance with the corresponding WQO criteria. No exceedance of WQO criterion is also expected from the discharge of hydrotest water. Therefore, no unacceptable residual water quality impact due to release of SS from marine construction works is expected.

Potential water quality impacts from land-based construction activities are expected to be controlled with the implementation of proposed mitigation measures. No unacceptable water quality impact from land-based construction works is expected.

7.10.2 Operation Phase

No unacceptable residual water quality impact would expected from the operation of the proposed LNG Terminal including the discharge of cooled seawater, concentrated seawater and treated effluent from sewage treatment plant.

No unacceptable residual water quality impact would also expected during maintenance dredging at the jetty with the implementation of mitigation measures including controlled work rate and silt curtain around grab dredger.

The additional risk associated with accidental spill from the operation of the LNG Terminal is expected to be minimal. With the implementation of appropriate design features as well as the adoption of contingency plan, no unacceptable water quality impact would be expected.

7.11 Cumulative Impact

Cumulative impact from projects in the vicinity has been considered. Detailed considerations are provided under Section 5 of Annex 7B. The following concurrent projects are selected and summarized below which have been taken into account in the modelling assessment with updated information that are not presented in Annex 7B.

7.11.1 Engineering Feasibility Study for Industrial Estate at Tuen Mun Area 38 (Register No. ESB-277/2014)

Letter was issued to the corresponding project proponent (the Hong Kong Science and Technology Parks Corporation) to confirm the need of construction of marine sewage outfall (as stated in the Project Profile), the construction period and other details. The project proponent replied there is no further update in design and project programme available. Thus assessment would be done based solely on information provided by the submitted Project Profile. Since there is no direct discharge of (treated or untreated) sewage into marine water under this Project, the only potential cumulative impact from the proposed development of the industrial estate at Tuen Mun Area 38 would be the water quality impact from the potential marine construction of subsea sewage outfall. Given that there is no detail for marine construction nor plan showing the layout of potential outfall extend, the potential marine construction from this project would not be taken into account in the construction phase water quality modelling exercise. In view of its notable physical separation from the pipeline alignment under this Project, significant cumulative impact would not be expected.

7.11.2 Expansion of Hong Kong International Airport into a Three-Runway System (Register No.: AEIAR- 185/2014)

To account for the potential change in flow regime due to the presence of reclamation for 3RS-HKIA, the reclamation has been taken into account in both construction phase and operation phase modelling exercise under this Study. Furthermore, ground treatment by deep cement mixing (DCM) as well as sand filling by TSHD has been taken into account in the construction phase sediment plume modelling assessment.

7.11.3 Potential Reclamation Site at Lung Kwu Tan

Based on the recent communication with CEDD, the reclamation at Lung Kwu Chau would be commenced in 2023 the earliest, and could be subjected to changes. Since the marine construction under this Project is expected to be conducted in 2019, there will not be temporal overlapping for the construction of this Project and the Lung Kwu Tan Reclamation. Therefore, the potential cumulative impact from the construction of the reclamation at Lung Kwu Tan would not be taken into account for construction. On the other hand, the potential change in flow regime has been taken into account in the operation phase modelling assessment in view of the long term operation of the proposed Offshore LNG terminal.

7.11.4 Integrated Waste Management Facilities (IWMF) at Shek Kwu Chau (Registration No. AEIAR-163/2012)

Based on latest available information, the marine works for this project, which primarily involves the formation of about 15.9ha of reclamation adjacent to Shek Kwu Chau (about 1.5km away from the LPS Pipeline and over 4km from the LNG Terminal) by non-dredged methods, is anticipated to commence in 2018 for completion in around 2022. According to the approved EIA and the subsequent application for variation of EP conditions, the marine filling works for reclamation (which is the major water quality concern under this Project) would only be conducted behind completed seawall with a 50m opening enclosed by a double layer of silt curtains. Water quality assessment in the approved EIA and for the subsequent application for variation of EP conditions indicated the potential SS elevation would be very localized and comply with the corresponding water quality criterion at the nearest WSRs identified under the EIA study. The potential water quality impact from small scale dredging and ground treatment works required under the project are also expected to be localized and would comply with the corresponding water quality criteria according to the approved EIA and the subsequent application for variation of EP conditions. In view of the above, no unacceptable cumulative water quality impact from the marine construction for reclamation under this Project would be expected. On the other hand, the potential change in flow regime due to the reclamation has been taken into account in the operation phase modelling assessment in view of the long term operation of the proposed Offshore LNG terminal.

Submarine cable laying works associated with the project currently do not have a confirmed programme. According to the approved EIA, the disturbed sediment from the laying of submarine cable would be settled within 80m from the cable alignment. As shown in Annex 7C, the predicted sediment plume for marine works under mitigated scenarios will not reach Shek Kwu Chau. This means there will not be significant cumulative impact on water quality from the submarine cable laying works for IWMF which would be conducted to the north of Shek Kwu Chau.

7.11.5 Tung Chung New Town Extension (Registration No. AEIAR-196/2016)

The Tung Chung East Reclamation has been taken into account in both the construction phase and operation phase modelling of this Study.

7.11.6 New Contaminated Mud Marine Disposal Facility at Airport East / East Sha Chau Area (AEIAR-089/2005)

Based on the updated information provided by Civil Engineering and Development Department (CEDD), the forecast sediment disposal in 2019 would be 0.47Mm³, which translates to about 2 barge loads per day for a typical 650m³ barge. It is noted that the active contaminated mud pits is currently CMP V_d at present and would be followed by CMP V_b and then CMP V_c after exhaustion. Among these three pits, CMP V_b is the closest to the BPPS pipeline alignment, and the corresponding sediment source is chosen at CMP V_b in the sediment plume dispersion model, with sediment loss calculated based on the 2019 forecast of 0.47Mm³ delivered by two barges daily.

7.11.7 Improvement Dredging for Lamma Power Station Navigation Channel (AEIAR-212/2017)

Based on the information provided by the HKE, concurrent dredging at Zone 2 of the dredging area under AEIAR-212/2017 would not be conducted concurrently with the marine works for LPS. The next worst case scenario of navigation dredging using grab dredger at Zone 1 has been taken into account in the construction phase sediment plume modelling exercise under this Project according to the available information provided in the approved EIA of AEIAR-212/2017. This project has not been taken into account in the sediment plume modelling exercise for the operation phase sediment plume modelling exercise in view of the large physical separation.

7.11.8 Open Sea Disposal Area for Uncontaminated Sediment at South Cheung Chau

Based on the updated information provided by CEDD, the forecast sediment disposal in 2019 would be 3.10Mm³, which translates to about 13 barge loads per day for a typical 650m³ barge. It is noted that there is no particular pit or hotspot for active disposal. For conservative assessment, it is assumed the 13 barge loads would be distributed to the northern half of the open sea disposal area so the distance to the nearby WSRs is shorter (thus more conservative results).

7.12 Environmental Monitoring and Audit

7.12.1 Construction Phase

Marine water quality monitoring at selected WSRs is recommended for marine dredging and jetting works for the pipeline construction. Regular site audits would also be conducted throughout the marine-based construction under this Project. The specific monitoring requirements are detailed in the standalone Environmental Monitoring and Audit (EM&A) Manual.

7.12.2 Operation Phase

Marine water quality monitoring at selected nearby WSRs is recommended for first year of operation of the LNG Terminal. Details are provided in the standalone EM&A Manual.

During maintenance dredging at the LNG Terminal, water quality monitoring at selected nearby WSRs would be required. The specific monitoring requirements are detailed in the EM&A Manual.

7.13 Conclusion

7.13.1 Construction Phase

Computational modelling has been conducted to predict various potential water quality impacts from the proposed marine dredging and jetting operations under this Project, including SS elevation, sedimentation, DO depletion, release of nutrient, heavy metal and trace organic contaminants. Full compliance is predicted at all identified WSRs for all parameters in both seasons with the implementation of proposed mitigation measures. To ensure environmental compliance, marine water monitoring for the marine construction works is recommended.

Other potential water quality impacts from other marine and land-based construction works were also addressed. Appropriate preventive and mitigation measures are recommended to minimise the potential water quality impact from these works. Environmental monitoring and audit is recommended to ensure the proper implementation of these measures.

7.13.2 Operation Phase

The potential change in water quality due to various discharges at the LNG Terminal, including cooled seawater and TRC from regasification unit, concentrated seawater from freshwater generator and treated sewage effluent from sewage treatment plant, have been assessed. No unacceptable water quality impact has been predicted from these discharges. Potential water quality impact from the operation phase maintenance dredging is also assessed by computational model and no unacceptable water quality impact has been predicted.

Furthermore, computational simulation has been conducted to predict the movement and extent of oil patches by assuming a hypothetic worst-case of an oil spill event from LNGC as required in the EIA Study Brief to devise the arrangement for spill containment and clean-up effort.

([1]) Sediment quality data for SS7 is available since 1998.

([2]) ERM – Hong Kong, Ltd (2002) EIA for the Proposed Submarine Gas Pipeline from Cheng Tou Jiao Liquefied Natural Gas Receiving Terminal, Shenzhen to Tai Po Gas Production Plank, Hong Kong. Final EIA Report. For the Hong Kong and China Gas Co., Ltd.

([3]) Maunsell (2001) EIA for Tai Po Sewage Treatment Works - Stage V. Final EIA Report. For Drainage Services Department, Hong Kong SAR Government.

([4]) ERM - Hong Kong, Ltd (2007) Liquefied Natural Gas (LNG) Receiving Terminal and Associated Facilities. For CAPCO. Final EIA Report. December 2006

([5]) ERM – Hong Kong, Ltd (2000) EIA for Construction of an International Theme Park in Penny's Bay of North Lantau together with its Essential Associated Infrastructures - Environmental Impact Assessment. Final EIA Report. For Civil Engineering Department, Hong Kong SAR Government.

([6]) ERM - Hong Kong, Ltd (2006) Liquefied Natural Gas (LNG) Receiving Terminal and Associated Facilities. For CAPCO. Final EIA Report. December 2006.

([7]) Maunsell (2002). EIA for Decommissioning of Cheoy Lee Shipyard at Penny's Bay. For Civil Engineering Department, Hong Kong SAR Government.

([8]) ERM – Hong Kong (1997). EIA for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit. For Civil Engineering Department, Hong Kong SAR Government.

([9]) Maunsell (2001). EIA for Wanchai Development Phase II - Comprehensive Feasibility Study. For Territory Development Department, Hong Kong SAR Government.

([11]) BMT Asia Pacific Ltd (2009). EIA for Hong Kong Offshore Wind Farm in Southeastern Waters. For HK Offshore Wind Limited

([12]) ERM - Hong Kong, Ltd. (2019). EIA for Additional Gas-fired Generation Units Project. For Castle Peak Power Company Limited.

([13]) Langford, T. E. (1983). Electricity Generation and the Ecology of Natural Waters.

([14]) Tender Ref. WP 98-567 Provision of Service for Ecotoxicity Testing of Marine Antifoulant – Chlorine in Hong Kong Final Report January 2000. Submitted to Environmental Protection Department by the Centre for Coastal Pollution and Conservation, City University of Hong Kong.

([15]) No exceedance of SS and sedimentation criteria is predicted at CR2. As a precautionary measure, silt curtain surrounding CR2 is recommended to reduce the relatively high sedimentation flux

([16]) While silt curtains at 01_G, 05_G, 06_G, 09_G and 11_G are not necessary to achieve compliance to the SS criteria for WQO, the effect of silt curtains is taken into account in the predicted SS elevation for the mitigated scenarios.

([17]) Mott MacDonald (1991). Contaminated Spoil Management Study, Final Report, Volume 1, for EPD, October 1991.

([18]) Approved Direct-to-Permit application for Pacific Light Cable Network (PLCN)–Deep Water Bay (DIR-254/2017).

([19]) Approved Direct-to-Permit application for Asia-Africa-Europe-1 (AAE-1) Cable System (DIR-244/2016).

([20]) Approved Direct-to-Permit application for Asia Pacific Gateway (APG) - Tseung Kwan O (DIR-233/2013).

([21]) Approved EIA Report for the Black Point Gas Supply Project (AEIAR-150/2010).

([22]) Approved EIA of The Proposed Submarine Gas Pipelines from Cheng Tou Jiao Liquefied Natural Gas Receiving Terminal, Shenzhen to Tai Po Gas Production Plant, Hong Kong (AEIAR-071/2003).

([23]) Approved Direct-to-Permit application for Asia-Africa-Europe-1 (AAE-1) Cable System (DIR-244/2016).

([24]) Approved EIA Report for the Black Point Gas Supply Project (AEIAR-150/2010).

([25]) Approved EIA Report for the HKLNG Terminal and (AEIAR - 106/2007).

([26]) Approved EIA Report for the Additional Gas-fired Generation Units Project (AEIAR-197/2016).

([27]) Integrity check would also be required for the FSRU Vessel. Such integrity test would be conducted outside of Hong Kong and so no water quality impact to Hong Kong waters would be expected.

([28]) Based on Table 2 of the Drainage Services Department's Sewerage Manual. The same per head sewage discharge rate was adopted in the approved EIA of Black Point Gas Supply Project (AEIAR-150/2010) and Additional Gas-fired Generation Units Project (AEIAR-197/2016) and is considered appropriate.

([29]) Based on mass balance, salinity change = 3,360 m³ day^-1 ÷ (3,360 m³ day^-1 - 60 m³ day^-1) – 100% = 1.818%

([30]) The discharge of concentrated seawater has not been taken into account in the cooled water discharge modelling to assess the worst case scenario in terms of maximum temperature decrease due to cooled water discharge.

([31]) Based on preliminary estimation from the WorleyParsons Design Guide for this Project. Such loading level is comparable to typical domestic flow levels stipulated in Table T1 of Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning (Version 1.0).

([32]) Detailed design of the FSRU vessel is not currently available. It is expected containment bunds and appropriate drainage system would be provided where necessary (e.g. where lube oil or other chemicals would be used or stored) to collect seawater/rain deck drains.

([33]) Boiling point of the main component in LNG, methane, is at −161.6°C at 1 atmospheric pressure.

Parameter	ADV-21 Guideline		SS7
	LCEL	UCEL
Arsenic (mg kg^-1)	12	42	7.9
			(4.4-11.0)
Cadmium (mg kg^-1)	1.5	4	0.1
			(<0.1-0.3)
Chromium (mg kg^-1)	80	160	50
			(14-73)
Copper (mg kg^-1)	65	110	111
			(30-250)
Lead (mg kg^-1)	75	110	61
			(27-230)
Mercury (mg kg^-1)	0.5	1	0.22
			(0.05-0.60)
Nickel (mg kg^-1)	40	40	19
			(6-24)
Silver (mg kg^-1)	1	2	0.3
			(<0.2-1.0)
Zinc (mg kg^-1)	200	270	157
			(59-400)
Total Polychlorinated	23	180	18
Biphenyls (PCBs) (µg kg^-1)			(18-22)
Low Molecular Weight Polycyclic	550	3,160	122
Aromatic Hydrocarbons (PAHs) (μg kg^-1)			(90-246)
High Molecular Weight Polycyclic	1,700	9,600	312
Aromatic Hydrocarbons (PAHs) (μg kg^-1)			(62-1,400)
Chemical Oxygen Demand (mg kg^-1)	--	--	18,000
			(10,000-28,000)
Total Kjeldahl Nitrogen	--	--	450
(mg kg^-1)			(180 - 680)

7.2.1 Water Pollution Control Ordinance (WPCO)

7.2.2 Technical Memorandum for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-ICW)

7.2.3 Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM)

7.2.4 Practice Note for Professional Persons, Construction Site Drainage

7.3.1 Study Area

7.3.2 Marine Water Quality

7.3.3 Water Quality in Typhoon Shelters

7.3.5 Sediment Quality in Typhoon Shelters

7.3.6 Sediment Elutriate Quality

7.3.7 Water Quality Sensitive Receivers

7.4.1 Suspended Solids

7.4.2 Water Temperature

7.4.3 Salinity

7.4.4 Dissolved Oxygen

7.4.5 Sediment Deposition

7.4.6 Nutrients

7.4.7 Dissolved Metals and Organic Contaminants

7.4.8 Total Residual Chlorine

7.5.1 General Methodology

7.5.2 Uncertainties in Assessment Methodology

7.6.1 Construction Phase

7.6.2 Operation Phase

7.7.1 Changes in Water Quality due to Marine Construction Activities

Suspended Solids (SS) Dispersion and Sedimentation

Dredging Scenario C01A

Dredging Scenario C01B

Dredging Scenario C01C

Jetting Scenario C02

Jetting Scenario C03

Jetting Scenario C04

Jetting Scenario C05

Jetting Scenario C06

Jetting Scenario C07

Other Marine Construction Works

Dissolved Oxygen (DO) Depletion

Release of Sediment-bounded Contaminants

Release of Sediment-bounded Nutrients

7.7.2 Marine Vessel Discharges

7.7.3 Subsea Pipeline Hydrotesting

7.7.4 Runoff from Land-based Work Sites

7.7.5 Sewage Discharges

7.8.2 Discharge of Concentrated Seawater and Treated Effluent from the FSRU Vessel

7.8.4 Accidental Spill Events

7.8.5 Maintenance Dredging at the LNG Terminal

Marine Construction Works

Land-based Construction Works

Discharge of Hydrotest Water

7.9.2 Operation Phase

7.10.1 Construction Phase

7.10.2 Operation Phase

7.11.1 Engineering Feasibility Study for Industrial Estate at Tuen Mun Area 38 (Register No. ESB-277/2014)

7.11.2 Expansion of Hong Kong International Airport into a Three-Runway System (Register No.: AEIAR- 185/2014)

7.11.3 Potential Reclamation Site at Lung Kwu Tan

7.11.4 Integrated Waste Management Facilities (IWMF) at Shek Kwu Chau (Registration No. AEIAR-163/2012)

7.11.8 Open Sea Disposal Area for Uncontaminated Sediment at South Cheung Chau

7.12.1 Construction Phase

7.12.2 Operation Phase

7.13.1 Construction Phase

7.13.2 Operation Phase