Parameters	Objectives	Sub-Zone
Offensive Odour, Tints	Not to be present	Whole zone
Visible foam, oil scum, litter	Not to be present	Whole zone
E. coli	Not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year.	Secondary Contact Recreation Subzones
E. coli	Not exceed 180 per 100 mL, calculated as the geometric mean of all samples collected from March to October inclusive. Samples should be taken at least 3 times in one calendar month at intervals of between 3 and 14 days.	Bathing Beach Subzones
Depth-averaged DO	Not less than 4 mg L^-1 for 90% of the sampling occasions during the whole year; values should be calculated as the annual water column average (expressed normally as the arithmetic mean of at least 3 measurements at 1m below surface, mid depth and 1m above the seabed. However in water of a depth of 5m of less the mean shall be that of 2 measurements – 1m below surface and 1m above seabed, and in water of less than 3m the 1m below surface sample only shall apply.)	Marine waters
Dissolved Oxygen (DO) within 2 m of the seabed	Not be less than 2 mg L^-1 within 2 m of the seabed for 90% of the sampling occasions during the whole year.	Marine waters
pH	To be in the range of 6.5 - 8.5, change due to human activity not to exceed 0.2	Marine waters excepting Bathing Beach Subzones
pH	To be within the range of 6.0 - 9.0 for 95% of samples collected during the whole year, change due to human activity not to exceed 0.5.	Bathing Beach Subzones
Salinity	Change due to human activity not to exceed 10% of ambient level	Whole zone
Temperature	Not to exceed 2 ^oC change due to human activity.	Whole zone
Suspended Solids (SS)	Not to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Marine waters
Unionised Ammonia (UIA)	Not to exceed 0.021 mg L^-1, calculated as the annual average (arithmetic mean).	Whole zone
Nutrients	Not present in quantities sufficient to cause excessive algal growth	Marine waters
	Annual mean depth-averaged inorganic nitrogen not to exceed 0.3 mg L^-1	Castle Peak Bay Subzone
	Annual mean depth-averaged inorganic nitrogen not to exceed 0.5 mg L^-1	Marine waters excepting Castle Peak Bay Subzone
Toxic substances	Not to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms.	Whole zone
	Not to cause a risk to any beneficial use of the aquatic environment due to human activity.	Whole zone

Source: Statement of Water Quality Objectives (North Western Water Control Zone).

Table 8.2: Water Quality Objectives for North Western Supplementary WCZ

Parameters	Objectives	Sub-Zone
Offensive Odour, Tints	Not to be present	Whole zone
Visible foam, oil scum, litter	Not to be present	Whole zone
E. coli	Not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year.	Secondary Contact Recreation Subzones
Depth-averaged DO	Not less than 4 mg L^-1 for 90% of the sampling occasions during the whole year; values should be calculated as the annual water column average (expressed normally as the arithmetic mean of at least 3 measurements at 1m below surface, mid depth and 1m above the seabed. However in water of a depth of 5m of less the mean shall be that of 2 measurements – 1m below surface and 1m above seabed, and in water of less than 3m the 1m below surface sample only shall apply.)	Whole zone
Dissolved Oxygen (DO) within 2 m of the seabed	Not less than 2 mg L^-1 within 2 m of the seabed for 90% of the sampling occasions during the whole year.	Whole zone
pH	To be in the range of 6.5 - 8.5, change due to human activity not to exceed 0.2	Whole zone
Salinity	Change due to human activity not to exceed 10% of ambient level	Whole zone
Temperature	Not to exceed 2 ^oC change due to human activity.	Whole zone
Suspended Solids (SS)	Not to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Whole zone
Unionised Ammonia (UIA)	Not to exceed 0.021 mg L^-1, calculated as the annual average (arithmetic mean).	Whole zone
Nutrients	Not present in quantities sufficient to cause excessive algal growth	Whole zone
	Annual mean depth-averaged inorganic nitrogen not to exceed 0.5 mg L^-1	Whole zone
Toxic substances	Not to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms.	Whole zone
	Not to cause a risk to any beneficial use of the aquatic environment due to human activity.	Whole zone

Source: Statement of Water Quality Objectives (North Western Supplementary Water Control Zone).

Table 8.3: Water Quality Objectives for Deep Bay WCZ

Parameters	Objectives	Sub-Zone
Offensive Odour, Tints	Not to be present	Whole zone
Visible foam, oil scum, litter	Not to be present	Whole zone
E. coli	Not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year.	Secondary Contact Recreation Subzone and Mariculture Subzone (L.N. 455 of 1991)
	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.	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones
	Not exceed 1000 per 100 ml, calculated as the running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days.	Yuen Long & Kam Tin (Lower) Subzone and other inland waters
	Not exceed 180 per 100 mL, calculated as the geometric mean of all samples collected from March to October inclusive in one calendar year. Samples should be taken at least 3 times in a calendar month at intervals of between 3 and 14 days.	Yung Long Bathing Beach Subzone (L.N. 455 of 1991)
Depth-averaged DO	Not cause the level of dissolved oxygen to fall below 4 mg L^-1 for 90% of the sampling occasions during the year; values should be taken at 1 metre below surface.	Inner Marine Subzone excepting Mariculture Subzone
	Not cause the level of dissolved oxygen to fall below 4 mg L^-1 for 90% of the sampling occasions during the year; values should be calculated as water column average (arithmetic mean of at least 2 measurements at 1 metre below surface and 1 metre above seabed).	Outer Marine Subzone excepting Mariculture Subzone
	Not be less than 5 mg L^-1 for 90% of the sampling occasions during the year; values should be taken at 1 metre below surface.	Mariculture Subzone
	Not cause the level of dissolved oxygen to be less than 4 mg L^-1.	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges Subzone, Water Gathering Ground Subzones and other inland waters of the Zone
Dissolved Oxygen (DO) within 2 m of the seabed	Not be less than 2 mg L^-1 within 2 m of the seabed for 90% of the sampling occasions during the whole year.	Outer Marine Subzone excepting Mariculture Subzone
pH	To be in the range of 6.5 - 8.5, change due to human activity not to exceed 0.2	Marine waters excepting Yung Long Bathing Beach Subzone
	To be in the range of 6.5 - 8.5	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones Other inland waters
	To be in the range of 6.0 – 9.0	Yung Long Bathing Beach Subzone
Salinity	Change due to human activity not to exceed 10% of ambient level	Whole zone
Temperature	Not to exceed 2 ^oC change due to human activity.	Whole zone
Suspended Solids (SS)	Not to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Marine waters
Suspended Solids (SS)	Human activities shall not cause the annual median of suspended solids to exceed 20 mg L^-1.	Yuen Long & Kam Tin (Upper and Lower) Subzones, Beas Subzone, Ganges Subzone, Indus Subzone, Water Gathering Ground Subzones and other inland waters
Unionised Ammonia (UIA)	Not to exceed 0.021 mg L^-1, calculated as the annual average (arithmetic mean).	Whole zone
Nutrients	Not present in quantities sufficient to cause excessive algal growth	Inner and Outer Marine Subzones
	Annual mean depth-averaged inorganic nitrogen not to exceed 0.7 mg L^-1	Inner Marine Subzone
	Level of inorganic nitrogen should not exceed 0.5 mg L^-1, expressed as annual water column average (arithmetic mean of at least 2 measurements at 1 metre below surface and 1 metre above seabed).	Outer Marine Subzone
Toxic substances	Not to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms.	Whole zone
	Not to cause a risk to any beneficial use of the aquatic environment due to human activity.	Whole zone

Source: Statement of Water Quality Objectives (Deep Bay Water Control Zone).

Table 8.4: Water Quality Objectives for Western Buffer WCZ

Parameters	Objectives	Sub-Zone
Offensive Odour, Tints	Not to be present	Whole zone
Visible foam, oil scum, litter	Not to be present	Whole zone
E. coli	Not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year.	Secondary Contact Recreation Subzones and Fish Culture Subzones
	Not exceed 180 per 100 mL, calculated as the geometric mean of all samples collected from March to October inclusive in 1 calendar year. Samples should be taken at least 3 times in 1 calendar month at intervals of between 3 and 14 days.	Recreation Subzones
	Less than 1 per 100 mL, calculated as the geometric mean of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days	Water Gathering Ground Subzones
Depth-averaged DO	Not less than 4 mg L^-1 for 90% of the sampling occasions during the whole year; values should be calculated as the annual water column average (expressed normally as the arithmetic mean of at least 3 measurements at 1m below surface, mid depth and 1m above the seabed. However in water of a depth of 5m of less the mean shall be that of 2 measurements – 1m below surface and 1m above seabed, and in water of less than 3m the 1m below surface sample only shall apply.)	Marine waters except Fish Culture Subzones
Depth-averaged DO	Not less than 5 mg L^-1 for 90% of the sampling occasions during the years; values should be calculated as water column average (arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed).	Fish Culture Subzones
Dissolved Oxygen (DO) within 2 m of the seabed	Not be less than 2 mg L^-1 within 2 m of the seabed for 90% of the sampling occasions during the whole year.	Marine waters
pH	To be in the range of 6.5 - 8.5, change due to human activity not to exceed 0.2	Marine waters
pH	Human activity should not cause the pH of the water to exceed the range of 6.5-8.5 units.	Water Gathering Ground Subzones
Salinity	Change due to human activity not to exceed 10% of ambient level	Whole zone
Temperature	Not to exceed 2 ^oC change due to human activity.	Whole zone
Suspended Solids (SS)	Not to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Marine waters
Unionised Ammonia (UIA)	Not to exceed 0.021 mg L^-1, calculated as the annual average (arithmetic mean).	Whole zone
Nutrients	Not present in quantities sufficient to cause excessive algal growth	Marine waters
	Annual mean depth-averaged inorganic nitrogen not to exceed 0.4 mg L^-1	Marine waters
Toxic substances	Not to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms.	Whole zone
	Not to cause a risk to any beneficial use of the aquatic environment due to human activity.	Whole zone

Source: Statement of Water Quality Objectives (Western Buffer Water Control Zone).

8.2.4 Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS)

8.2.4.1 Under the WPCO, the discharge of effluents are subject to limits set in the Cap. 358AK “Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters” (TM-DSS). The limit levels vary depending on the WCZ, the receiving waters and the rate of effluent flow. Standards for effluent discharged into inshore waters and marine waters of the North Western WCZ are shown in Table 8.5 and Table 8.6.

Table 8.5: Standards for Effluent Discharged into the Inshore Waters of North Western Water Control Zone

Flow rate (m3/day)	≤10	>10 and ≤200	>200 and ≤400	>400 and ≤600	>600 and ≤800	>800 and ≤1000	>1000 and ≤1500	>1500 and ≤2000	>2000 and ≤3000	>3000 and ≤4000	>4000 and ≤5000	>5000 and ≤6000
pH (pH units)	6-9	6-9	6-9	6-9	6-9	6-9	6-9	6-9	6-9	6-9	6-9	6-9
Temperature (°C)	40	40	40	40	40	40	40	40	40	40	40	40
Colour (lovibond units) (25 mm cell length)	1	1	1	1	1	1	1	1	1	1	1	1
Suspended solids	50	30	30	30	30	30	30	30	30	30	30	30
BOD	50	20	20	20	20	20	20	20	20	20	20	20
COD	100	80	80	80	80	80	80	80	80	80	80	80
Oil & Grease	30	20	20	20	20	20	20	20	20	20	20	10
Iron	15	10	10	7	5	4	3	2	1	1	0.8	0.6
Boron	5	4	3	2	2	1.5	1.1	0.8	0.5	0.4	0.3	0.2
Barium	5	4	3	2	2	1.5	1.1	0.8	0.5	0.4	0.3	0.2
Mercury	0.1	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001
Cadmium	0.1	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001
Other toxic metals individually	1	1	0.8	0.7	0.5	0.4	0.3	0.2	0.15	0.1	0.1	0.1
Total toxic metals	2	2	1.6	1.4	1	0.8	0.6	0.4	0.3	0.2	0.1	0.1
Cyanide	0.2	0.1	0.1	0.1	0.1	0.1	0.05	0.05	0.03	0.02	0.02	0.01
Phenols	0.5	0.5	0.5	0.3	0.25	0.2	0.1	0.1	0.1	0.1	0.1	0.1
Sulphide	5	5	5	5	5	5	2.5	2.5	1.5	1	1	0.5
Total residual chlorine	1	1	1	1	1	1	1	1	1	1	1	1
Total nitrogen	100	100	80	80	80	80	50	50	50	50	50	30
Total phosphorus	10	10	8	8	8	8	5	5	5	5	5	5
Surfactants (total)	20	15	15	15	15	15	10	10	10	10	10	10
E. coli (count/100ml)	1000	1000	1000	1000	1000	1000	1000	1000	1000	1000	1000	1000

Note: All units are in mg/L unless otherwise stated. All figures are upper limits unless otherwise indicated.

Table 8.6: Standards for Effluent Discharged into the Marine Waters of North Western Water Control Zone

Flow rate (m3/day)	≤10	>10 and ≤200	>200 and ≤400	>400 and ≤600	>600 and ≤800	>800 and ≤1000	>1000 and ≤1500	>1500 and ≤2000	>2000 and ≤3000	>3000 and ≤4000	>4000 and ≤5000	>5000 and ≤6000
pH (pH units)	6-10	6-10	6-10	6-10	6-10	6-10	6-10	6-10	6-10	6-10	6-10	6-10
Temperature (°C)	45	45	45	45	45	45	45	45	45	45	45	45
Colour (lovibond units) (25 mm cell length)	4	1	1	1	1	1	1	1	1	1	1	1
Suspended solids	500	500	500	300	200	200	100	100	50	50	40	30
BOD	500	500	500	300	200	200	100	100	50	50	40	30
COD	1000	1000	1000	700	500	400	300	200	150	100	80	80
Oil & Grease	50	50	50	30	25	20	20	20	20	20	20	20
Iron	20	15	13	10	7	6	4	3	2	1.5	1.2	1
Boron	6	5	4	3.5	2.5	2	1.5	1	0.7	0.5	0.4	0.3
Barium	6	5	4	3.5	2.5	2	1.5	1	0.7	0.5	0.4	0.3
Mercury	0.1	0.1	0.1	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001
Cadmium	0.1	0.1	0.1	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001	0.001
Other toxic metals individually	2	1.5	1.2	0.8	0.6	0.5	0.32	0.24	0.16	0.12	0.1	0.1
Total toxic metals	4	3	2.4	1.6	1.2	1	0.64	0.48	0.32	0.24	0.2	0.14
Cyanide	1	0.5	0.5	0.5	0.4	0.3	0.2	0.15	0.1	0.08	0.06	0.04
Phenols	0.5	0.5	0.5	0.3	0.25	0.2	0.13	0.1	0.1	0.1	0.1	0.1
Sulphide	5	5	5	5	5	5	2.5	2.5	1.5	1	1	0.5
Total residual chlorine	1	1	1	1	1	1	1	1	1	1	1	1
Total nitrogen	100	100	80	80	80	80	50	50	50	50	50	50
Total phosphorus	10	10	8	8	8	8	5	5	5	5	5	5
Surfactants (total)	30	20	20	20	15	15	15	15	15	15	15	15
E. coli (count/100ml)	4000	4000	4000	4000	4000	4000	4000	4000	4000	4000	4000	4000

Note: All units are in mg/L unless otherwise stated. All figures are upper limits unless otherwise indicated.

8.2.5 Practice Note for Professional Persons on Construction Site Drainage (ProPECC Note PN 1/94)

8.2.5.1 A practice note for professional persons was issued by the EPD to provide guidelines for handling and disposal of construction site discharges. The Practice Note for Professional Persons on Construction Site Drainage (ProPECC Note PN 1/94) provides good practice guidelines for dealing with various types of discharge from a construction site. Practices outlined in ProPECC Note PN 1/94 should be followed as far as possible during construction to minimise the water quality impact due to construction site drainage.

ID	Descriptions
Bathing beaches¹
B1	Butterfly Beach (Gazetted Beach)
B2	Lung Kwu Sheung Tan (Non-gazetted beach)
B3	Gazetted Beaches at Tuen Mun
B4	Anglers’ Beach (Gazetted Beach)
B5	Gazetted Beaches at Ma Wan
B6	Gold Coast Marina / Golden Beach (Gazetted Beach)
B7	Lung Tsai (Non-gazetted beach)
B8	Lung Kwu Tan (Non-gazetted beach)
B9	Gemini Beaches (Gazetted Beach)
B10	Hoi Mei Wan Beach(Gazetted Beach)
B11	Casam Beach and Lido Beach (Gazetted Beach)
B12	Tin Kau Beach (Gazetted Beach)
B13	Approach Beach (Gazetted Beach)
Cooling seawater and WSD flushing water intakes
C1	Black Point Cooling Water Intake
C2	Castle Peak Power Station Cooling Water Intake
C3	WSD Seawater Intake at Tuen Mun
C4	Proposed Ta Pang Po Intake (Pumping Station)
C5²	Future seawater intake for Lantau Logistics Park (LLP)
C6²	Future seawater intake point for Tung Chung East
C7a³	Cooling water intake at Hong Kong International Airport (North)
C7b	Cooling water intake at Hong Kong International Airport (South)
C8	Future Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities (HKBCF) Intake
C9	Future Sludge Treatment Facilities Intake
C10	Proposed Lok On Pai Intake (Pumping Station)
C11	Seawater intake at Tung Chung
C12	WSD Seawater Intake at Ap Lei Chau
C13	Cooling Water Intake at Wah Fu Estate
C14	Queen Mary Hospital Cooling Water Intake
C15	Cooling Water Intake for Shiu Wing Steel Mills
C17⁴	Future Seawater Intake at Hong Kong International Airport (East)
C18²	Future seawater intake point for Sunny Bay Development
C20	WSD Seawater intake at Tsing Yi
Corals
CR2	Artificial Reef at Sha Chau and Lung Kwu Chau Marine Park
CR3	Hard Corals at The Brothers Islands
CR4	Coral Community in Sandy Bay
CR5	Coral Community in Kau Yi Chau
Fisheries and fish culture zones
F1	Ma Wan Fish Culture Zone (FCZ)
F2	Fishing/Spawning Grounds in North Lantau
F3	High Production of Capture Fisheries
Ecologically sensitive areas and areas of conservation importance
E1	Pak Nai SSSI
E2	San Tau Beach SSSI
E3	Potential marine park / marine reserve for Southwest Lantau
E4	Planned marine park at Brothers Islands / Tai Mo To (Dolphin Habitat)
E5	Sha Chau and Lung Kwu Chau Marine Park
E6	Hau Hok Wan (Horseshoe Crab Habitat)
E7	Sha Lo Wan (Horseshoe Crab Habitat)
E8	Sham Wat Wan (Mangrove and Horseshoe Crab Habitat)
E9	Tai O (Mangrove Habitat)
E10	Yi O (Mangrove and Horseshoe Crab Habitat)
E11	Tai Ho Bay, Near Tai Ho Stream SSSI
E12	Sham Shui Kok (Dolphin Habitat)
Typhoon shelters
T1	Tuen Mun Typhoon Shelter
T2	Aberdeen Typhoon Shelter

1. Bathing beaches represent primary contact recreation areas. Water quality at secondary contact recreation areas along the coast of Tuen Mun and Tsuen Wan can be inferred from the observation points located along Urmston Road (e.g. M1, M5, M6, M7 and M8).

2. As no implementation programme is available for the Lantau Logistics Park and Sunny Bay development, C5 and C18 have been adopted for operation phase only. Similarly, the implementation schedule for Tung Chung East (as of September 2013) suggests that the first population intake would not be until 2023/24. As the marine works for the third runway project will be completed by then, C6 is also not considered to be applicable during construction phase.

3. C7a will be relocated due to the land formation activities of the project, consequently, the location adopted in the operation phase ‘without project’ scenario is slightly different from the construction phase scenarios and the operation phase ‘with project’ scenario.

4. As C17 is part of the third runway project, this WSR is only applicable to the operation phase ‘with project’ scenario.

Table 8.8: Observation Points for Water Quality Modelling

ID	Descriptions
Representative Location
M1	Urmston Road (Main Channel)
M2	River Trade Terminal
M3	Airport Channel Western End
Marine Park
M4a, M4b, M4c, M4d, M4e	Four corners and southern boundary mid-point of Sha Chau and Lung Kwu Chau Marine Park
EPD Monitoring Location
M5	Lantau Island (North)
M6	Pearl Island
M7	Pillar Point
M8	Urmston Road
M9	Chep Lap Kok (North)
M10	Chep Lap Kok (West)
M11	Hong Kong Island (West) 1
M12	Hong Kong Island (West) 2
M13	Tsing Yi (South)
M14	Tsing Yi (West)
M15	Inner Deep Bay 1
M16	Inner Deep Bay 2
M17	Inner Deep Bay 3
M18	Outer Deep Bay 1
M19	Outer Deep Bay 2

8.3.3 Baseline Conditions

8.3.3.1 The project is situated in the north western waters of Hong Kong, as such the waters around the project are heavily influenced by the massive freshwater flows from the Pearl River Estuary. As the Pearl River carries heavy suspended sediment and nutrient loads, these parameters are generally higher in the north western waters than in other water bodies in Hong Kong.

8.3.3.2 EPD has conducted regular marine water and sediment quality monitoring since 1986. For assessment of the effects of the project to various WSRs, the latest marine water and sediment quality data collected by EPD at their monitoring stations were summarised to provide an overview of the baseline conditions within the study area.

Summary of Latest Baseline Monitoring Data

8.3.3.3 The North Western WCZ attained an overall WQO compliance rate of 72 % in 2012, which is the same as 2011. All stations in this WCZ fully complied with the unionised ammonia and DO objectives, while all but one station failed to meet the TIN objective. The higher TIN levels may be due to higher background levels from Pearl River discharges, as well as some local discharges and surface runoff. A summary of marine water quality monitoring data routinely collected by EPD from 1986 to 2012 at the monitoring stations within this WCZ is presented in Table 8.9 and a summary of the bottom sediment quality is presented in Table 8.12.

8.3.3.4 The Western Buffer WCZ attained an overall WQO compliance rate of 67 % in 2012 which is lower than the previous year due primarily to a drop in compliance against the TIN objective (only 25 % in 2012). This increase in TIN may be due to the higher background TIN level under the influence of Pearl River discharges, as well as annual fluctuations of surface runoff and discharges from nearby wastewater treatment plants. A summary of marine water quality monitoring data routinely collected by EPD from 1986 to 2012 at the monitoring stations within this WCZ is presented in Table 8.10 and a summary of the bottom sediment quality is presented in Table 8.13.

8.3.3.5 The Deep Bay WCZ attained an overall WQO compliance rate of 53% in 2012 which represents an improvement from previous years due to the decrease in unionised ammonia levels, which enabled a 100% compliance rate for the unionised ammonia objective. However similar to previous years, none of the monitoring stations in this WCZ met the TIN objective in 2012. A summary of marine water quality monitoring data routinely collected by EPD from 1986 to 2012 at the monitoring stations within this WCZ is presented in Table 8.11 and a summary of the bottom sediment quality is presented in Table 8.14.

8.3.3.6 All 41 gazetted beaches in Hong Kong complied with the WQO in 2012. The E. coli count in the Tuen Mun District range from 40 to 62 counts per 100ml in 2012, and received “Fair” annual ranking for all the beaches along the Tuen Mun coast. The E. coli count in the Tsuen Wan District ranged from 24 to 88 counts per 100ml in 2012, and received “Good” or “Fair” annual ranking for all the beaches along the Tsuen Wan area.

8.3.3.7 A summary of marine beach water quality monitoring data routinely collected by EPD at relevant monitoring stations is presented in Table 8.15 and Table 8.16.

Table 8.9: Marine Water Quality in North Western Water Control Zone at Selected Stations in 1986 to 2012

Marine Water Quality Parameters
Monitoring Stations		Temperature (oC)	Salinity (psu)	Dissolved Oxygen (mg/L)	Dissolved Oxygen (%saturation)	pH	Secchi Disc Depth (M)	Turbidity (NTU)	Volatile Suspended Solids (mg/L)	5-day Biochemical Oxygen Demand (mg/L)	Unionised Ammonia (mg/L)	Nitrite Nitrogen (mg/L)	Total Inorganic Nitrogen (mg/L)	Total Kjeldahl Nitrogen (mg/L)	Orthophosphate Phosphorus (mg/L)	Total Phosphorus (mg/L)	Chlorophyll-a (µg/L)	Escherichia coli (cfu/100ml)	Suspended Solids (mg/L)	Ammonia Nitrogen (mg/L)	Nitrate Nitrogen (mg/L)	Total Nitrogen (mg/L)	Silica (mg/L)	Phaeo-pigments (µg/L)	Faecal Coliforms (cfu/100ml)
NM1 (Lantau Island (North))	Min	14.9	8.1	2.0	29	7.3	0.5	0.5	<0.5	<0.1	<0.001	<0.002	0.03	<0.05	<0.002	<0.02	<0.2	<1	0.5	<0.005	0.004	0.21	0.06	<0.5	1
	Max	30.6	34.4	14.2	187	8.9	34.0	137.2	13.0	4.6	0.021	0.370	2.16	4.68	0.098	0.65	54.0	8000	62.0	0.480	1.600	5.50	7.10	38.0	20000
	Avg	23.1	30.0	5.9	81	8.0	2.1	11.2	1.6	0.7	0.004	0.045	0.37	0.34	0.025	0.06	2.5	316	9.3	0.107	0.219	0.60	1.37	1.2	625
NM2 (Pearl Island)	Min	12.4	6.4	2.7	38	7.3	0.4	1.0	<0.5	<0.1	0.001	<0.002	0.05	0.05	<0.002	<0.02	<0.2	1	0.5	<0.005	<0.002	0.22	<0.05	<0.2	1
	Max	30.3	34.0	11.5	156	8.8	4.0	80.0	77.0	4.0	0.022	0.380	2.29	1.40	0.089	0.88	53.0	8100	98.0	0.440	1.700	2.58	8.10	22.0	17000
	Avg	23.5	28.1	6.2	85	8.0	1.7	10.1	1.7	0.8	0.005	0.055	0.46	0.34	0.026	0.06	3.2	293	8.2	0.109	0.291	0.69	1.70	1.3	560
NM3 (Pillar Point)	Min	12.1	7.4	2.2	32	6.3	0.4	1.0	<0.5	<0.1	0.001	<0.002	0.02	<0.05	<0.002	<0.02	<0.2	<1	0.5	<0.005	<0.002	0.09	<0.05	<0.2	<1
	Max	29.9	33.9	17.7	200	8.7	4.0	181.2	37.0	4.0	0.025	0.370	2.10	1.30	0.080	0.39	56.0	180000	120.0	0.546	1.500	2.62	6.90	13.0	320000
	Avg	23.3	29.0	6.0	83	8.0	1.7	11.7	1.8	0.7	0.005	0.055	0.44	0.34	0.026	0.06	2.9	476	10.1	0.111	0.270	0.67	1.58	1.2	910
NM5 (Urmston Road)	Min	12.1	3.8	2.1	30	7.3	0.2	1.2	<0.5	<0.1	<0.001	<0.002	0.03	0.07	<0.002	0.02	<0.2	1	0.5	<0.005	<0.002	0.15	<0.05	<0.2	1
	Max	30.7	37.0	17.6	200	8.8	3.8	678.4	26.0	6.4	0.047	0.520	2.40	1.90	0.087	0.36	49.0	28000	210.0	0.570	1.900	2.72	8.90	22.0	92000
	Avg	23.4	27.6	6.0	82	8.0	1.5	16.6	2.1	0.8	0.006	0.069	0.57	0.38	0.030	0.07	2.8	685	12.5	0.144	0.355	0.80	1.96	1.3	1380
NM6 (Chek Lap Kok (North))	Min	12.0	3.3	2.4	34	6.9	0.4	1.2	<0.5	<0.1	0.001	<0.002	0.01	<0.05	<0.002	<0.02	<0.2	<1	0.9	<0.005	<0.002	0.09	<0.05	<0.2	<1
	Max	31.2	33.9	13.4	170	8.7	3.0	148.3	20.0	9.0	0.032	0.440	2.15	1.70	0.120	0.48	82.0	4200	130.0	0.578	1.800	2.61	10.00	24.0	7600
	Avg	23.6	26.5	6.5	89	8.0	1.5	12.9	2.0	0.9	0.004	0.069	0.56	0.32	0.024	0.06	4.1	30	11.0	0.098	0.388	0.77	2.06	1.6	63
NM8 (Chek Lap Kok (West))	Min	14.8	5.3	2.4	35	7.3	0.5	0.7	<0.5	<0.1	<0.001	<0.002	0.01	0.08	<0.002	<0.02	<0.2	<1	1.3	<0.005	<0.002	0.12	0.08	<0.2	<1
	Max	31.3	33.8	12.6	180	8.7	3.0	79.0	14.0	8.0	0.026	0.380	2.13	1.30	0.047	0.14	75.0	3700	73.0	0.440	1.600	2.44	8.30	37.0	39000
	Avg	23.6	28.2	6.6	92	8.1	1.5	15.7	2.2	0.8	0.003	0.055	0.41	0.22	0.015	0.04	4.6	4	13.3	0.056	0.301	0.58	1.62	1.7	9

Note: All averages represent depth averaged values. The max and min values represent the highest and lowest values on record for the entire data period (not depth-averaged). Averages for Faecal Coliforms and E. coli are geometric means. All other averaged values are arithmetic means.

1. NM1 and NM5 monitoring results started from 1988

2. NM2 and NM3 monitoring results started from 1986

3. NM6 monitoring results started from 1991

4. NM8 monitoring results started from 1999

Table 8.10: Marine Water Quality in Western Buffer Water Control Zone at Selected Stations in 1986 to 2012

Marine Water Quality Parameters
Monitoring Stations		Temperature (oC)	Salinity (psu)	Dissolved Oxygen (mg/L)	Dissolved Oxygen (%saturation)	pH	Secchi Disc Depth (M)	Turbidity (NTU)	Volatile Suspended Solids (mg/L)	5-day Biochemical Oxygen Demand (mg/L)	Unionised Ammonia (mg/L)	Nitrite Nitrogen (mg/L)	Total Inorganic Nitrogen (mg/L)	Total Kjeldahl Nitrogen (mg/L)	Orthophosphate Phosphorus (mg/L)	Total Phosphorus (mg/L)	Chlorophyll-a (µg/L)	Escherichia coli (cfu/100ml)	Suspended Solids (mg/L)	Ammonia Nitrogen (mg/L)	Nitrate Nitrogen (mg/L)	Total Nitrogen (mg/L)	Silica (mg/L)	Phaeo-pigments (µg/L)	Faecal Coliforms (cfu/100ml)
WM1 (Hong Kong Island (West))	Min	14.7	13.0	1.6	23	6.5	0.5	0.1	<0.5	<0.1	<0.001	<0.002	0.02	<0.05	<0.002	<0.02	<0.2	<1	<0.5	<0.005	<0.002	0.06	<0.05	<0.2	1
	Max	29.4	34.9	13.1	185	8.9	6.3	98.6	11.0	4.9	0.044	0.190	1.08	1.90	0.200	0.44	45.0	6900	53.0	0.340	0.970	2.03	4.10	39.0	19000
	Avg	22.8	31.9	6.2	85	8.1	2.4	7.9	1.2	0.7	0.003	0.024	0.18	0.31	0.018	0.05	2.6	168	5.5	0.064	0.091	0.42	0.86	1.0	277
WM2 (Hong Kong Island (West))	Min	14.7	11.7	2.3	30	7.0	0.5	0.5	<0.5	<0.1	0.001	<0.002	0.03	0.08	<0.002	<0.02	<0.2	1	<0.5	<0.005	<0.002	0.11	<0.05	<0.2	1
	Max	30.4	34.4	11.5	157	8.9	6.5	98.6	19.0	4.1	0.026	0.230	1.12	1.56	0.124	0.63	49.0	30000	62.0	0.625	0.910	1.82	4.90	45.0	77000
	Avg	23.0	31.0	6.1	84	8.1	2.1	8.4	1.3	0.7	0.004	0.034	0.28	0.36	0.023	0.06	2.8	268	6.6	0.101	0.141	0.53	1.07	1.2	455
WM3 (Tsing Yi (South))	Min	14.0	14.8	0.5	9	6.0	0.5	0.8	<0.5	<0.1	0.001	<0.002	0.04	0.07	<0.002	<0.02	<0.2	1	<0.5	<0.005	0.003	0.12	<0.05	<0.2	1
	Max	29.2	34.5	12.0	159	9.0	20.0	111.8	19.0	6.8	0.038	0.160	1.38	2.44	0.199	0.38	30.0	71000	87.0	0.663	1.200	2.71	4.50	34.0	190000
	Avg	22.9	31.4	5.7	79	8.0	1.9	9.4	1.5	0.7	0.006	0.033	0.30	0.42	0.029	0.06	2.3	966	8.4	0.135	0.131	0.58	1.04	1.0	1749
WM4 (Tsing Yi (West))	Min	14.7	13.2	1.4	20	7.4	0.5	0.7	<0.5	<0.1	0.001	<0.002	0.04	<0.05	<0.002	<0.02	<0.2	<1	<0.5	<0.005	0.011	0.14	0.06	<0.2	<1
	Max	29.8	34.6	12.2	160	8.9	4.5	102.5	11.0	3.5	0.022	0.470	1.04	1.84	0.157	0.62	41.0	56000	110.0	0.310	0.860	2.08	5.00	24.0	150000
	Avg	22.9	31.0	5.7	79	8.1	2.0	10.0	1.5	0.7	0.005	0.037	0.29	0.37	0.025	0.06	2.2	308	9.2	0.104	0.152	0.56	1.13	1.1	547

Note: All averages represent depth averaged values . The max and min values represent the highest and lowest values on record for the entire data period (not depth-averaged). Averages for Faecal Coliforms and E. coli are geometric means. All other averaged values are arithmetic means.

1. WM1 and WM2 monitoring results started from 1988

2. WM3 and WM4 monitoring results started from 1986

Table 8.11: Marine Water Quality in Deep Bay Water Control Zone at Selected Stations in 1986 to 2012

	Marine Water Quality Parameters
Monitoring Stations		Temperature (oC)	Salinity (psu)	Dissolved Oxygen (mg/L)	Dissolved Oxygen (%saturation)	pH	Secchi Disc Depth (M)	Turbidity (NTU)	Volatile Suspended Solids (mg/L)	5-day Biochemical Oxygen Demand (mg/L)	Unionised Ammonia (mg/L)	Nitrite Nitrogen (mg/L)	Total Inorganic Nitrogen (mg/L)	Total Kjeldahl Nitrogen (mg/L)	Orthophosphate Phosphorus (mg/L)	Total Phosphorus (mg/L)	Chlorophyll-a (µg/L)	Escherichia coli (cfu/100ml)	Suspended Solids (mg/L)	Ammonia Nitrogen (mg/L)	Nitrate Nitrogen (mg/L)	Total Nitrogen (mg/L)	Silica (mg/L)	Phaeo-pigments (µg/L)	Faecal Coliforms (cfu/100ml)
DM1 (Inner Deep Bay)	Min	9.8	0.3	0.1	2	6.2	0.1	2.4	1.0	0.3	0.001	<0.002	0.27	0.28	0.054	0.17	<0.2	1	5.5	<0.005	0.003	1.16	0.11	<0.2	1
	Max	33.2	29.5	14.3	165	8.6	2.0	600.0	40.0	20.0	0.521	1.830	14.05	18.00	2.900	16.00	260.0	1100000	420.0	14.000	3.750	18.05	17.00	210.0	1500000
	Avg	24.2	17.3	4.3	56	7.5	0.4	47.9	7.6	3.5	0.058	0.279	4.35	4.47	0.465	0.73	11.4	2823	52.5	3.501	0.565	5.32	5.77	7.7	4177
DM2 (Inner Deep Bay)	Min	9.9	0.3	0.6	8	6.3	0.1	1.2	0.5	0.1	0.001	0.003	0.18	0.22	0.049	0.10	<0.2	<1	1.5	<0.005	<0.002	0.57	0.12	<0.2	<1
	Max	32.4	29.5	16.1	201	8.8	3.0	189.9	29.0	21.0	0.760	1.500	8.64	11.00	1.185	2.39	170.0	430000	190.0	8.400	2.830	11.27	16.00	110.0	530000
	Avg	24.1	19.2	5.2	69	7.6	0.6	31.7	5.1	2.5	0.050	0.268	3.14	2.98	0.334	0.47	10.6	634	32.3	2.295	0.578	3.84	4.78	6.2	942
DM3 (Inner Deep Bay)	Min	11.0	0.8	2.4	39	6.2	0.1	2.3	<0.5	<0.1	0.001	<0.002	0.01	0.11	<0.002	0.04	<0.2	1	2.0	<0.005	<0.002	0.43	<0.05	<0.2	1
	Max	31.6	32.1	14.2	183	8.9	3.0	442.0	18.0	12.0	0.553	0.636	6.33	6.20	0.901	1.50	180.0	19000	140.0	5.550	4.300	7.19	12.00	77.0	25000
	Avg	24.1	21.6	6.3	85	7.8	0.8	21.9	3.0	1.5	0.020	0.161	1.43	1.02	0.125	0.19	6.2	66	18.1	0.640	0.627	1.81	3.47	3.1	110
DM4 (Outer Deep Bay)	Min	11.0	2.4	0.6	9	6.1	0.1	1.2	<0.5	<0.1	0.001	0.003	0.09	<0.05	<0.002	0.02	<0.2	<1	1.0	<0.005	0.032	0.25	0.20	<0.2	<1
	Max	32.8	34.2	11.4	164	9.0	4.5	500.0	21.0	5.1	0.108	1.100	3.75	2.60	0.220	1.35	68.0	9500	110.0	2.200	3.620	4.04	9.60	37.0	12000
	Avg	23.9	23.3	6.3	85	7.9	1.0	17.9	2.3	0.9	0.010	0.115	0.95	0.57	0.056	0.11	3.4	143	14.1	0.272	0.559	1.25	3.03	1.6	234
DM5 (Outer Deep Bay)	Min	12.0	1.4	2.6	38	6.2	0.1	1.1	<0.5	<0.1	0.001	<0.002	0.08	0.08	<0.002	0.03	<0.2	1	1.1	<0.005	0.032	0.14	<0.05	<0.2	1
	Max	31.5	34.3	13.7	183	9.3	8.0	162.6	35.0	11.0	0.067	0.360	2.55	1.50	0.120	0.65	72.0	41000	130.0	0.720	1.900	2.80	9.15	72.0	58000
	Avg	23.8	26.1	6.2	84	7.9	1.3	16.6	2.0	0.9	0.007	0.087	0.72	0.43	0.036	0.07	2.6	346	11.9	0.177	0.452	0.97	2.44	1.3	667

Note: All averages represent depth averaged values . The max and min values represent the highest and lowest values on record for the entire data period (not depth-averaged). Averages for Faecal Coliforms and E. coli are geometric means. All other averaged values are arithmetic means.

1. DM5 monitoring results started from 1991

Table 8.12: Marine Sediment Quality in North Western Water Control Zone at Selected Stations in 1986 to 2012

Monitoring Stations	NS2 (Pearl Island)			NS3 (Pillar Point)			NS4 (Urmston Road)			NS6 (Chek Lap Kok (North))
	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg
Zinc (mg/kg)	38	180	102	39	160	97	57	180	97	32	130	82
Vanadium (mg/kg)	11	50	33	17	64	39	18	73	33	17	71	34
Total Volatile Solid (% Total Solid)	3.8	11.0	6.7	3.1	10.0	6.5	2.9	9.5	5.7	2.2	9.4	5.5
Total Sulphide (mg/kg)	<1	81	17	<1	130	20	<1	220	21	<1	47	8
Total Solid (%w/w)	35	64	49	38	70	51	34	77	57	37	76	56
Total Polychlorinated Biphenyls (μg/kg)	<5	18	14	<5	23	15	<5	18	14	<5	18	14
Total Phosphorus (mg/kg)	84	860	211	86	1200	214	77	1100	197	73	340	159
Total Kjeldahl Nitrogen (mg/kg)	120	1500	377	77	1200	364	23	810	327	74	860	290
Total Cyanide (mg/kg)	<0.1	0.3	0.1	<0.1	0.5	0.1	<0.1	0.3	0.1	<0.1	0.2	0.1
Total Carbon (%w/w)	0.4	1.2	0.7	0.3	1.6	0.7	0.3	1.3	0.6	0.2	1.2	0.5
Silver (mg/kg)	<1	1	1	<1	1	1	<1	1	1	<1	1	1
Pyrene (μg/kg)	<5	26	11	<5	31	12	<5	34	11	<5	19	6
Phenanthrene (μg/kg)	<5	19	6	<5	26	8	<5	24	7	<5	17	6
Particle Size Fraction <63 micrometer (%w/w)	35	99	72	5	98	68	12	97	50	10	98	60
Nickel (mg/kg)	6	30	20	7	35	20	7	40	18	8	32	19
Mercury (mg/kg)	<0.05	0.36	0.11	0.03	1.28	0.15	<0.05	0.35	0.10	<0.05	0.22	0.08
Manganese (mg/kg)	250	790	475	230	900	531	440	1200	641	200	720	477
Lead (mg/kg)	20	84	43	20	71	41	29	82	42	16	55	34
Iron (mg/kg)	14000	39000	29889	14000	47000	32127	5500	62000	36902	14000	57000	32813
Indeno(1,2,3-cd)pyrene (μg/kg)	<5	15	7	<5	33	8	<5	24	7	3	8	5
Fluorene (μg/kg)	<10	<10	<10	<10	<10	<10	<10	<10	<10	<10	<10	<10
Fluoranthene (μg/kg)	<5	24	10	<5	44	12	<5	30	11	<5	18	6
Electrochemical Potential (mV)	-380	1	-146	-432	1	-144	-418	1	-163	-372	1	-132
Dry Wet Ratio	0.35	0.72	0.49	0.33	0.69	0.49	0.33	0.71	0.56	0.37	0.72	0.54
Dibenzo(ah)anthracene (μg/kg)	3	5	5	3	5	5	3	5	5	3	5	5
Copper (mg/kg)	7	95	43	8	84	36	5	67	28	7	84	21
Chrysene (μg/kg)	<5	18	7	<5	30	8	<5	18	7	<5	13	5
Chromium (mg/kg)	12	57	36	8	61	34	9	68	31	15	61	31
Chemical Oxygen Demand (mg/kg)	5900	20000	13646	140	23000	14328	5600	19000	13325	7400	20000	13063
Cadmium (mg/kg)	0.1	11.0	0.4	0.1	10.0	0.4	0.1	8.9	0.4	0.1	13.0	0.4
Boron (mg/kg)	9	56	23	1	49	22	1	74	23	7	66	22
Benzo(k)fluoranthene (μg/kg)	1	50	6	1	50	7	1	50	6	1	50	4
Benzo(ghi)perylene (μg/kg)	3	19	8	3	27	9	1	23	7	1	11	3
Benzo(b)fluoranthene (μg/kg)	2	22	8	2	44	10	1	30	8	1	12	4
Benzo(a)pyrene (μg/kg)	1	50	9	1	50	10	1	50	8	1	50	5
Benzo(a)anthracene (μg/kg)	<3	14	6	<3	31	7	<3	12	6	1	10	4
Barium (mg/kg)	9	49	32	17	55	33	18	64	30	15	56	28
Arsenic (mg/kg)	1.8	20.0	10.2	2.4	25.0	11.9	3.7	26.0	12.5	6.1	24.0	12.3
Anthracene (μg/kg)	<5	<5	<5	<5	<5	<5	<5	<5	<5	<5	<5	<5
Ammonia Nitrogen (mg/kg)	<0.05	26.10	5.44	<0.05	23.00	6.69	0.10	39.00	9.50	<0.05	17.00	4.48
Aluminium (mg/kg)	7600	42000	26149	12000	46000	27143	12000	52000	22647	9600	51000	24283
Acenaphthylene (μg/kg)	3	250	64	5	250	64	4	250	64	1	250	64
Acenaphthene (μg/kg)	1	100	51	3	100	52	2	100	51	1	100	51

Note:

1. NS2 monitoring data before 1987 is not available.

2. Both NS3 and NS4 monitoring data started from 1986.

3. NS6 monitoring data before 1991 is not available.

Table 8.13: Marine Sediment Quality in Western Buffer Water Control Zone at Selected Stations in 1986 to 2012

Monitoring Stations	WS1 (Tsing Yi (South))			WS2 (Tsing Yi (West))
	Min	Max	Avg	Min	Max	Avg
Zinc (mg/kg)	9	190	111	66	170	107
Vanadium (mg/kg)	15	51	33	28	50	37
Total Volatile Solid (% Total Solid)	0.6	71.0	8.0	3.5	10.0	7.1
Total Sulphide (mg/kg)	0.1	220.0	60.0	0.2	200.0	27.1
Total Solid (%w/w)	35	79	47	36	54	44
Total Polychlorinated Biphenyls (μg/kg)	<5	25	16	<5	24	15
Total Phosphorus (mg/kg)	48	450	199	140	1100	225
Total Kjeldahl Nitrogen (mg/kg)	8.9	1100	450	260	1800	472
Total Cyanide (mg/kg)	<0.1	0.3	0.1	<0.1	0.2	0.1
Total Carbon (%w/w)	0.3	2.5	0.8	0.4	1.6	0.6
Silver (mg/kg)	<1	3	1	<1	3	1
Pyrene (μg/kg)	<5	110	22	<5	43	12
Phenanthrene (μg/kg)	<5	39	10	<5	30	8
Particle Size Fraction <63 micrometer (%w/w)	27	98	79	66	99	87
Nickel (mg/kg)	8	47	22	13	31	24
Mercury (mg/kg)	<0.05	2.30	0.22	<0.05	0.57	0.15
Manganese (mg/kg)	33	890	524	440	760	596
Lead (mg/kg)	5	68	41	22	54	41
Iron (mg/kg)	3400	40000	30193	22000	39000	32370
Indeno(1,2,3-cd)pyrene (μg/kg)	<5	55	15	<5	22	9
Fluorene (μg/kg)	<10	<10	<10	<10	<10	<10
Fluoranthene (μg/kg)	<5	90	23	<5	35	13
Electrochemical Potential (mV)	-603	42	-156	-762	58	-133
Dry Wet Ratio	0.33	0.71	0.46	0.36	0.50	0.43
Dibenzo(ah)anthracene (μg/kg)	<5	12	6	3	6	5
Copper (mg/kg)	1	280	63	17	140	40
Chrysene (μg/kg)	<5	40	11	<5	17	7
Chromium (mg/kg)	13	84	41	23	59	38
Chemical Oxygen Demand (mg/kg)	190	21000	14796	3900	21000	13965
Cadmium (mg/kg)	0.1	8.6	0.4	<0.1	9.2	0.3
Boron (mg/kg)	1	47	26	11	49	29
Benzo(k)fluoranthene (μg/kg)	2	50	12	2	50	8
Benzo(ghi)perylene (μg/kg)	2	55	17	2	23	10
Benzo(b)fluoranthene (μg/kg)	2	63	18	1	25	10
Benzo(a)pyrene (μg/kg)	2	67	20	2	50	12
Benzo(a)anthracene (μg/kg)	<3	48	13	<3	21	7
Barium (mg/kg)	15	58	36	25	56	39
Arsenic (mg/kg)	2.2	14.0	8.7	1.4	17.0	9.3
Anthracene (μg/kg)	<5	<5	<5	<5	<5	<5
Ammonia Nitrogen (mg/kg)	0.11	38.00	10.56	<0.05	35.00	6.11
Aluminium (mg/kg)	1400	45000	27408	18000	45000	30627
Acenaphthylene (μg/kg)	12	250	65	4	250	64
Acenaphthene (μg/kg)	7	100	52	3	100	52

Note:

1. Both WS1 and WS2 monitoring data started from 1988.

Table 8.14: Marine Sediment Quality in Deep Bay Water Control Zone at Selected Stations in 1986 to 2012

Monitoring Stations	DS1 (Inner Deep Bay)			DS2 (Inner Deep Bay)			DS3 (Outer Deep Bay)			DS4 (Outer Deep Bay)
	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg
Zinc (mg/kg)	86	560	227	69	420	166	49	230	127	36	180	102
Vanadium (mg/kg)	21	50	35	21	54	40	22	60	44	9	64	39
Total Volatile Solid (% Total Solid)	3.3	11.0	6.9	3.0	11.0	7.1	3.2	71.0	7.9	4.0	9.0	6.2
Total Sulphide (mg/kg)	<1	1200	294	<1	570	86	<1	160	28	<1	140	15
Total Solid (%w/w)	34	61	47	37	59	46	38	69	49	29	72	52
Total Polychlorinated Biphenyls (μg/kg)	<5	27	15	<5	24	15	<5	18	14	<5	19	14
Total Phosphorus (mg/kg)	110	954	387	120	660	311	100	780	238	60	550	184
Total Kjeldahl Nitrogen (mg/kg)	210	1800	557	160	1100	449	150	2300	418	100	1300	326
Total Cyanide (mg/kg)	<0.1	0.5	0.2	<0.1	0.6	0.1	<0.1	0.3	0.1	<0.1	0.3	0.1
Total Carbon (%w/w)	0.3	2.7	0.7	0.3	1.8	0.6	<1	1.4	0.5	0.3	1.3	0.6
Silver (mg/kg)	<1	3	1	<1	2	1	<1	1	1	<1	1	1
Pyrene (μg/kg)	<5	850	65	<5	170	23	<5	46	16	<5	44	11
Phenanthrene (μg/kg)	<5	350	30	<5	30	8	<5	41	8	<5	35	8
Particle Size Fraction <63 micrometer (%w/w)	8	222	76	17	96	77	32	98	80	<1	98	62
Nickel (mg/kg)	14	140	28	7	37	24	10	37	25	7	32	21
Mercury (mg/kg)	<0.05	0.52	0.16	<0.05	0.61	0.16	<0.05	0.36	0.13	<0.05	0.29	0.09
Manganese (mg/kg)	190	600	365	270	930	501	240	860	583	280	1100	566
Lead (mg/kg)	38	92	60	30	87	56	24	79	51	18	93	43
Iron (mg/kg)	17000	41000	29370	21000	44000	33055	17000	52000	35436	18000	79000	37490
Indeno(1,2,3-cd)pyrene (μg/kg)	<5	310	23	<5	41	10	<5	23	7	<5	23	6
Fluorene (μg/kg)	<10	81	14	<10	<10	<10	<10	<10	<10	<10	<10	<10
Fluoranthene (μg/kg)	<5	810	58	<5	61	18	<5	43	14	<5	53	11
Electrochemical Potential (mV)	-387	1	-215	-398	1	-162	-412	1	-163	-370	1	-133
Dry Wet Ratio	0.27	0.60	0.45	0.37	0.59	0.45	0.33	0.66	0.47	0.22	0.73	0.51
Dibenzo(ah)anthracene (μg/kg)	<5	91	9	<5	18	6	3	22	5	3	5	5
Copper (mg/kg)	14	210	72	18	100	53	11	230	47	6	65	29
Chrysene (μg/kg)	<5	370	40	<5	190	16	<5	46	10	<5	16	7
Chromium (mg/kg)	26	86	46	21	79	42	17	53	40	14	54	34
Chemical Oxygen Demand (mg/kg)	5400	29000	20174	140	22000	15541	7700	32000	14791	8300	21000	14020
Cadmium (mg/kg)	0.1	7.3	0.6	0.1	9.4	0.6	0.1	11.0	0.5	0.1	13.0	0.4
Boron (mg/kg)	1	29	14	7	47	17	8	54	20	11	58	23
Benzo(k)fluoranthene (μg/kg)	1	190	15	1	50	8	1	50	7	1	50	6
Benzo(ghi)perylene (μg/kg)	1	300	23	1	56	12	1	16	9	1	20	6
Benzo(b)fluoranthene (μg/kg)	1	410	29	1	52	13	1	23	9	1	29	7
Benzo(a)pyrene (μg/kg)	1	370	26	1	50	11	2	50	10	1	50	8
Benzo(a)anthracene (μg/kg)	<3	410	27	<3	29	9	<3	31	7	1	26	6
Barium (mg/kg)	23	160	55	27	74	47	17	59	40	13	61	35
Arsenic (mg/kg)	4.5	20.0	11.6	4.5	18.0	13.4	3.9	20.0	13.9	7.6	26.0	14.3
Anthracene (μg/kg)	<5	87	11	<5	32	6	<5	<5	<5	<5	6	5
Ammonia Nitrogen (mg/kg)	0.08	600.00	51.57	<0.05	95.00	10.93	<0.05	35.20	4.79	<0.05	36.00	6.04
Aluminium (mg/kg)	11000	53000	29843	11000	46000	30686	12000	50000	31196	9900	46000	26631
Acenaphthylene (μg/kg)	15	250	60	9	250	59	4	250	64	1	250	64
Acenaphthene (μg/kg)	8	100	51	5	100	50	2	100	52	1	100	51

Note:

1. All monitoring data started from 1987.

Table 8.15: Marine Beach Water Quality in Tuen Mun

	E. coli counts per 100ml (annual geometric mean)
Beach	1997	1998	1999	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012
Butterfly	259	121	44	61	74	60	74	55	55	94	84	56	49	30	41	42
Cafeteria New	309	100	60	51	104	62	80	54	70	120	68	48	38	31	27	47
Cafeteria Old	435	138	58	57	125	74	76	61	81	150	67	45	46	34	29	48
Castle Peak	332*	199*	57*	58*	105*	58*	64*	80*	90	139	64	47	35	63	49	48
Golden	352	98	44	50	87	66	84	46	62	117	87	63	42	37	26	62
Kadoorie	290	130	109	68	120	114	160	98	117	118	101	87	48	45	37	40

Source: EPD Beach Water Quality 2012

Note: *The beach was closed in the selected years

Table 8.16: Marine Beach Water Quality in Tsuen Wan

	E. coli counts per 100ml (annual geometric mean)
Beach	1997	1998	1999	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012
Anglers’	691*	502*	442*	326*	621*	1169*	693*	619*	895*	772*	496*	510*	276*	134*	27*	69*
Approach	1009*	435*	387*	316*	411*	696*	762*	470*	663*	599*	352*	251*	208*	124*	59	83
Casam	609	239	231	209	233	741	702*	594*	716*	426*	305*	289*	144*	102*	21	50
Gemini	458	399	350	258	323	1155	875*	1102*	1042*	853*	566*	481*	410*	137*	19*	40*
Hoi Mei Wan	471	280	109	177	199	547	442*	287*	641*	308*	286*	271*	130*	87*	23	51
Lido	600	262	231	181	269	683	734*	523*	782*	459*	280*	296*	178*	87*	21	32
Ma Wan Tung Wan	110	92	51	39	133	201	159	101	132	171	78	53	60	17	10	24
Ting Kau	1583*	1045*	515*	593*	739*	742*	831*	412*	512*	469*	405*	258*	145*	141*	58*	88*

Source: EPD Beach Water Quality 2012

Note: *The beach was closed in the selected years

8.3.4 Non-Statutory Marine Environmental Monitoring for Hong Kong International Airport

8.3.4.1 The Airport Authority Hong Kong is committed to monitoring the surrounding environment of the airport island and has conducted four rounds of monitoring since 2002.

8.3.4.2 Mott MacDonald Hong Kong Limited was commissioned to carry out the latest non-statutory marine environmental monitoring update 2009/10 for the marine environment surrounding HKIA including the Southern Sea Channel and East Tung Chung Bay. The study consisted of marine water quality monitoring and marine sediment quality monitoring. The marine water quality information provides a useful comparison against the EPD monitoring data as the monitoring locations for this study are much closer to the boundary of the airport island.

8.3.4.3 Water quality surveys as part of this non-statutory monitoring has been carried out between November 2002 to January 2011. The water quality monitoring locations are indicated in Appendix 8.1. A summary of water quality monitoring results is presented in Table 8.17.

Table 8.17: Summary of Water Quality Parameters Recorded from November 2002 to January 2011

Averaging Period	Area	Surface Temp.	Mid-Depth Temp.	Surface Salinity	DO	Turbidity	SS	BOD₅	TKN	TIN	TRC
Unit		ºC	ºC	ppt	mg/L	NTU	mg/L	mg/L	mg/L	mg/L	mg/L
WQO		<±2ºC	<±2ºC	<±10%	> 4 mg/L	-	<+30%	-	-	< 0.5 mg/L	-
Nov 2002	Impact	23.6	23.5	31.4	6.2	339.3	10.4	<2	0.4	N/A	N/A
Nov 2002	Control	23.6	23.5	31.4	6.2	390.3	23.0	<2	0.6	N/A	N/A
Jan 2003	Impact	17.8	17.8	28.9	9.2	7.3	13.4	2.0	0.5	N/A	N/A
Jan 2003	Control	17.6	17.5	28.8	9.5	5.3	12.5	2.0	0.5	N/A	N/A
Mar 2003	Impact	21.2	21.0	31.8	7.0	12.4	13.6	<2	0.6	N/A	N/A
Mar 2003	Control	20.9	20.1	31.0	7.0	12.0	15.5	<2	0.6	N/A	N/A
May 2003	Impact	26.3	26.0	24.8	8.5	8.0	6.2	<2	0.1	N/A	N/A
May 2003	Control	26.5	25.8	25.7	6.7	-16.6	10.5	<2	0.2	N/A	N/A
Jun 2003	Impact	27.4	27.3	14.9	5.3	15.7	14.2	<2	0.1	N/A	N/A
Jun 2003	Control	27.5	27.4	13.2	5.4	20.0	13.0	<2	0.2	N/A	N/A
Jul 2003	Impact	30.5	30.3	16.0	6.0	24.3	10.4	<2	0.1	N/A	N/A
Jul 2003	Control	29.6	29.0	16.5	4.6	47.7	13.0	<2	0.2	N/A	N/A
Aug 2003	Impact	30.3	30.1	20.7	5.8	21.1	19.8	<2	0.1	N/A	N/A
Aug 2003	Control	30.4	29.4	18.7	4.9	17.5	11.0	<2	0.1	N/A	N/A
Oct 2003	Impact	26.4	26.4	32.0	9.5	9.8	5.8	<2	0.2	N/A	N/A
Oct 2003	Control	26.2	26.1	32.0	8.2	12.4	9.5	<2	0.4	N/A	N/A
Dec 2005	Impact	17.9	17.8	32.7	8.1	5.0	5.8	<2	0.8	0.1	<0.2
Dec 2005	Control	17.9	17.3	32.7	8.7	7.8	8.0	<2	0.8	0.1	<0.2
Feb 2006	Impact	17.7	17.8	30.2	7.1	6.7	7.2	<2	0.3	0.3	<0.2
Feb 2006	Control	17.8	17.8	30.6	7.1	6.8	7.0	<2	0.3	0.3	<0.2
Apr 2006	Impact	22.4	22.2	26.5	6.6	8.0	8.0	<2	0.4	0.8	<0.2
Apr 2006	Control	21.9	21.5	28.0	6.4	7.1	12.5	<2	0.4	0.5	<0.2
Jun 2006	Impact	26.2	26.3	8.8	7.0	6.2	3.6	<2	0.3	1.5	<0.2
Jun 2006	Control	26.3	26.3	8.6	6.5	5.3	4.0	<2	0.3	1.5	<0.2
Aug 2006	Impact	29.8	29.8	11.6	6.5	7.2	6.0	<2	0.1	1.1	<0.2
Aug 2006	Control	29.9	29.8	10.5	6.3	7.2	5.5	<2	0.3	1.2	<0.2
Oct 2006	Impact	28.1	28.0	28.4	5.2	8.0	9.4	<2	0.5	0.6	<0.2
Oct 2006	Control	28.0	27.6	26.9	5.0	5.5	6.0	<2	0.5	0.5	<0.2
Mar 2010	Impact	20.5	20.5	29.2	7.1	11.6	9.2	<2	0.2	0.6	<0.2
Mar 2010	Control	19.8	20	29.1	7.4	14.2	11.5	<2	0.3	0.6	<0.2
May 2010	Impact	26.6	26.4	18.2	5.5	7	7.2	<2	0.4	1.1	<0.2
May 2010	Control	25.7	25.1	20.7	5.4	8.8	9	<2	0.4	0.8	<0.2
Jul 2010	Impact	29.2	29.1	9.7	10.8	12.2	12.8	2	0.4	1.1	<0.2
Jul 2010	Control	29.1	29	8.6	9.6	9.7	10	2.5	0.5	1.2	<0.2
Sep 2010	Impact	28.3	27.7	21.7	4.4	12.1	12.4	<2	0.3	1.1	<0.2
Sep 2010	Control	27.9	26.4	21.8	3.4	17.4	18	<2	0.3	0.9	<0.2
Nov 2010	Impact	23.2	23	30.6	6.7	14.7	15.2	<2	0.2	0.3	<0.2
Nov 2010	Control	23.3	23	30.3	6.3	11.7	20	<2	0.3	0.3	<0.2
Jan 2011	Impact	16.8	16.8	32.6	8.6	18.6	25.4	<2	0.2	0.2	<0.2
Jan 2011	Control	17.1	17.1	32.6	8.1	29.8	19	<2	0.2	0.2	<0.2
Average	Impact	24.5	24.4	24.0	7.1	27.8	10.8	<2	0.3	0.7	<0.2
Average	Control	24.3	24.0	23.9	6.6	31.0	11.9	<2	0.4	0.7	<0.2

Note:

§ All data are mid-depth average value unless stated otherwise.

§ Shaded cell represents the value exceeded the relevant WQOs.

8.3.4.4 The marine water quality monitoring results indicated that most of the water quality parameters recorded at the Control and Impact Stations complied with the relevant North Western WCZ WQOs, except that some average salinity and SS levels of the Impact Stations, the average TIN level of both Control Stations and Impact Stations, and the average DO level of one Control Stations exceeded the WQOs. However, the exceedances were within the long term variation as observed in EPD’s nearest monitoring stations (refer to NM6 and NM8 as presented in Table 8.9) and therefore the potential water quality impacts associated with operation of HKIA was not considered to be significant.

8.3.5 Water Quality Monitoring for New CMPs at East of Sha Chau

8.3.5.1 Routine water quality monitoring has been conducted by CEDD throughout the operation of the Contaminated Mud Pits at Airport East / East Sha Chau. The monitoring is conducted at a frequency of once per quarter and at three monitoring locations. When comparing the results with the SS criteria (30 % of the 90^th percentile at the nearest EPD monitoring station) set in Table 8.21 for NM3 and NM6, the closest EPD monitoring station, it was observed that all SS elevations would comply with the criteria. A summary of the water quality monitoring is provided in Table 8.18.

8.3.5.2 Water quality monitoring has also been conducted during the course of construction works for the Contaminated Mud Pit V at East of Sha Chau. Impact water quality monitoring commenced in September 2009 and was conducted at a frequency of three days per week, at mid-flood and mid-ebb tides, at three depths (surface, mid-depth and bottom) during the course of construction. The results are shown in Table 8.19. In general, the impact water quality monitoring results complied with the relevant North Western WCZ WQOs.

Table 8.18: Routine Water Quality Monitoring Results from Aug 2006 to May 2013

	SS	Turbidity	DO	Cr	Cu	Pb	Zn
	(mg/L)	(NTU)	(mg/L)	(µg/L)	(µg/L)	(µg/L)	(µg/L)
Reference Station	11.21	7.33	6.70	0.63	4.55	1.15	8.93
Mid-field	11.45	7.26	6.65	0.62	4.21	1.27	7.32
Impact Station	11.39	6.93	6.63	0.60	5.07	1.08	8.78

Source: CEDD Routine Water Quality Monitoring at Airport East / East Sha Chau

Note: All data are mid-depth and time average value unless stated otherwise.

Table 8.19: Impact Water Quality Monitoring Results at Near Field Stations from Sep 2009 to Jan 2013

Parameter	Near Field Stations	Results (average)
Salinity (ppt)	DS1(Down Stream Station)	24.68
	DS2(Down Stream Station)	24.50
	DS3(Down Stream Station)	24.62
	DS4(Down Stream Station)	24.59
	DS5(Down Stream Station)	24.28
	MW1(Ma Wan Station)	27.69
	US1(Upstream Station)	24.69
	US2(Upstream Station)	24.94
Dissolved Oxygen (mg/L)	DS1(Down Stream Station)	7.13
	DS2(Down Stream Station)	7.15
	DS3(Down Stream Station)	7.07
	DS4(Down Stream Station)	7.07
	DS5(Down Stream Station)	7.11
	MW1(Ma Wan Station)	6.72
	US1(Upstream Station)	7.17
	US2(Upstream Station)	7.14
Turbidity (NTU)	DS1(Down Stream Station)	12.95
	DS2(Down Stream Station)	11.14
	DS3(Down Stream Station)	10.81
	DS4(Down Stream Station)	9.54
	DS5(Down Stream Station)	8.95
	MW1(Ma Wan Station)	5.86
	US1(Upstream Station)	10.94
	US2(Upstream Station)	11.04
pH	DS1(Down Stream Station)	7.80
	DS2(Down Stream Station)	7.80
	DS3(Down Stream Station)	7.79
	DS4(Down Stream Station)	7.79
	DS5(Down Stream Station)	7.78
	MW1(Ma Wan Station)	7.77
	US1(Upstream Station)	7.79
	US2(Upstream Station)	7.79
Suspended Solids (mg/L)	DS1(Down Stream Station)	17.41
	DS2(Down Stream Station)	14.45
	DS3(Down Stream Station)	14.11
	DS4(Down Stream Station)	12.42
	DS5(Down Stream Station)	11.37
	MW1(Ma Wan Station)	8.52
	US1(Upstream Station)	14.50
	US2(Upstream Station)	14.35

Source: ERM (2009). Environmental Monitoring and Audit for Contaminated Mud Pit at Sha Chau (2009-2013) – EM&A Impact Results (http://www.cmp-monitoring.com.hk/EM&A%20Data.html).

8.4 Assessment Criteria

8.4.1 Water Quality Objectives

8.4.1.1 For assessment of water quality impacts due to suspended solid (SS) release during construction phase, the criterion specified in the WQO limits the allowable SS elevation to less than 30 % of the ambient level.

8.4.1.2 To determine the ambient SS level for assessment of water quality impacts due to SS release, data from each of EPD’s marine water quality monitoring stations in the North Western, Western and Deep Bay WCZs were collated into dry season (October to March) and wet season (April to September), and the 90^th percentile concentration for the entire period of monitoring data (1986 to 2012) for the surface, middle, bed and depth-averaged layers are presented in Table 8.20 below.

Table 8.20: 90th Percentile Suspended Solids from EPD Routine Monitoring Programme (1986-2012)

EPD Stations	Wet Season				Dry Season
EPD Stations	Surface	Middle	Bed	Depth Averaged	Surface	Middle	Bed	Depth Averaged
NM1	6.8	11.3	21.0	12.1	17.0	20.0	28.4	21.5
NM2	7.8	8.6	15.0	11.0	13.0	17.9	25.6	20.5
NM3	8.9	15.0	25.6	14.5	12.0	16.0	28.0	18.9
NM5	12.0	16.0	41.0	20.7	16.4	18.0	36.8	22.6
NM6	9.0	10.0	23.3	13.5	21.8	25.0	32.4	25.9
NM8	10.0	18.0	34.1	18.7	24.9	28.0	44.7	30.6
WM1	4.8	5.8	16.0	7.9	8.1	10.1	16.0	11.2
WM2	6.0	7.9	14.0	8.8	11.1	15.0	23.0	16.0
WM3	8.1	11.0	19.0	12.4	13.0	17.0	21.0	16.9
WM4	6.7	10.3	19.6	11.3	15.7	23.0	30.0	23.3
DM1*	78.8	N/A	9.0	78.8	130.0	N/A	9.0	130.0
DM2	55.2	N/A	N/A	55.2	72.4	N/A	N/A	72.4
DM3	22.6	N/A	92.2	25.8	36.7	N/A	28.2	36.7
DM4	15.0	9.7	29.0	23.4	21.0	5.5	39.2	29.4
DM5	14.0	15.9	24.0	16.9	16.8	23.6	41.6	28.2

Note: units are in mg/L. Values rounded to 1 decimal place.

Where the criteria is “N/A”, this means that no data was available from the reference EPD monitoring station.

* At DM1, there is very limited data for bed layer, hence the derived depth-averaged value is primarily based on the data for surface layer.

8.4.1.3 Based on the 90^th percentile from each EPD monitoring station, the criteria for assessment of elevations in SS concentration during construction phase are shown in Table 8.21.

Table 8.21: Water Quality Objectives for the Assessment of Elevations in Suspended Solids Concentrations due to Construction Impacts

EPD Station	Wet Season				Dry Season
EPD Station	Surface	Middle	Bed	Depth Averaged	Surface	Middle	Bed	Depth Averaged
NM1	2.0	3.4	6.3	3.6	5.1	6.0	8.5	6.5
NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
WM1	1.4	1.7	4.8	2.4	2.4	3.0	4.8	3.4
WM2	1.8	2.4	4.2	2.6	3.3	4.5	6.9	4.8
WM3	2.4	3.3	5.7	3.7	3.9	5.1	6.3	5.1
WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
DM1	23.6	N/A	2.7	23.6	39.0	N/A	2.7	39.0
DM2	16.6	N/A	N/A	16.6	21.7	N/A	N/A	21.7
DM3	6.8	N/A	27.7	7.7	11.0	N/A	8.5	11.0
DM4	4.5	2.9	8.7	7.0	6.3	1.6	11.8	8.8
DM5	4.2	4.8	7.2	5.1	5.0	7.1	12.5	8.5

Note: Units are in mg/L. Values rounded to 1 decimal place. Where the criteria is “N/A”, this means that no data was available from the reference EPD monitoring station.

8.4.1.4 The assessment criteria to be adopted for each WSR are taken as 30 % of the 90^th percentile at the nearest EPD monitoring station. This approach is consistent with the approach adopted by similar past projects (e.g. the HZMB EIA project). Based on the results shown in Table 8.21, the criteria for SS release at each WSR are shown in Table 8.22.

Table 8.22: Water Quality Objectives for Suspended Solids

WSR / Obs Points	Associated EPD Stations	Wet Season				Dry Season
WSR / Obs Points	Associated EPD Stations	S	M	B	DA	S	M	B	DA
B1	NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
B2	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
B3	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
B4	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B5	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B6	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
B7	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
B8	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
B9	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B10	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B11	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B12	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
B13	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
C1	DM5	4.2	4.8	7.2	5.1	5.0	7.1	12.5	8.5
C2	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
C4	NM1	2.0	3.4	6.3	3.6	5.1	6.0	8.5	6.5
C7a	NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
C7b	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
C8	NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
C9	DM4	4.5	2.9	8.7	7.0	6.3	1.6	11.8	8.8
C10	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
C11	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
C13	WM1	1.4	1.7	4.8	2.4	2.4	3.0	4.8	3.4
C14	WM1	1.4	1.7	4.8	2.4	2.4	3.0	4.8	3.4
C15	NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
CR2	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
CR3	NM3	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
CR4	WM1	1.4	1.7	4.8	2.4	2.4	3.0	4.8	3.4
CR5	WM2	1.8	2.4	4.2	2.6	3.3	4.5	6.9	4.8
E1	DM3	6.8	N/A	27.7	7.7	11.0	N/A	8.5	11.0
E2	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
E3	NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
E4	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
E5	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
E6	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
E7	NM6	2.7	3.0	7.0	4.0	6.5	7.5	9.7	7.8
E8	NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
E9	NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
E10	NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
E11	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
E12	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
F1	WM4	2.0	3.1	5.9	3.4	4.7	6.9	9.0	7.0
F2	NM5	3.6	4.8	12.3	6.2	4.9	5.4	11.0	6.8
F3	NM8	3.0	5.4	10.2	5.6	7.5	8.4	13.4	9.2
T1	NM2	2.3	2.6	4.5	3.3	3.9	5.4	7.7	6.2
T2	WM1	1.4	1.7	4.8	2.4	2.4	3.0	4.8	3.4

Note: The criteria follows the same definitions for “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged, that are adopted by EPD monitoring stations. Units are in mg/L. Values rounded to 1 decimal place.

Where the criteria is “N/A”, this means that no data was available from the reference EPD monitoring station.

8.4.1.5 As the WQO typically applies to depth-averaged SS concentrations, the depth-averaged criteria will be adopted as the principal assessment criteria for compliance, however, the findings at other depths will also be reviewed and compared to their reference criteria in the assessment.

8.4.1.6 For assessment of construction phase water quality impacts due to dissolved oxygen (DO) depletion, the predicted DO depletion will be compared with the long-term (1986 to 2012) mean DO from EPD’s baseline monitoring stations (presented in Table 8.23 below) in order to determine the predicted DO levels at WSRs.

Table 8.23: Long-term Mean DO Levels from EPD’s Baseline Monitoring Stations

EPD Stations	Wet Season		Dry Season
	Bottom Layer	Depth-averaged	Bottom Layer	Depth-averaged
NM1	4.6	5.2	6.6	6.5
NM2	5.2	5.8	6.7	6.6
NM3	4.7	5.3	6.8	6.8
NM5	4.6	5.3	6.8	6.8
NM6	5.8	6.1	7.0	7.0
NM8	5.8	6.3	7.0	7.0
WM1	4.8	5.6	6.9	6.8
WM2	5.1	5.6	6.5	6.5
WM3	4.8	5.1	6.4	6.3
WM4	4.7	5.2	6.3	6.3
DM1	N/A	3.8	N/A	4.7
DM2	N/A	4.6	N/A	5.8
DM3	6.4	5.9	7.5	6.8
DM4	5.6	5.9	6.7	6.7
DM5	5.1	5.6	6.7	6.7

Units are in mg/L. Values rounded to 1 decimal place. Where the criteria is “N/A”, this means that no data was available from the reference EPD monitoring station.

8.4.2 Water Supplies Department (WSD) Water Quality Criteria

8.4.2.1 For assessment of construction phase water quality impacts at WSD’s seawater intakes for flushing water, the water quality criteria as specified by WSD (shown in Table 8.24) were adopted for the depth-averaged (surface to middle layer) of the water column. No new cooling water or sewage discharge point is located within 100 m from any seawater intake point.

Table 8.24: WSD’s Water Quality Criteria for Flushing Water at Sea Water Intakes

Parameter (in mg/L unless otherwise stated)	Target Limit
Colour (HU)	< 20
Turbidity (NTU)	< 10
Threshold Odour Number (odour unit)	< 100
Ammonia Nitrogen (NH₃-N)	< 1
Suspended Solids (SS)	< 10
Dissolved Oxygen (DO)	> 2
5-day Biochemical Oxygen Demand (BOD₅)	< 10
Synthetic Detergents	< 5
E. coli (no. per 100 mL)	< 20,000

Note: The WSD criteria has been applied to the depth-averaged surface to middle layer of the water column.

8.4.2.2 It should be noted that the WSD criteria are specified at WSD’s seawater intake, however the depth of each individual intake varies and it is difficult to define the exact layer of the water column at each intake. Similarly, the depth of the intakes below sea level can change significantly with the tides, hence the layer of the water column at each intake would also be constantly fluctuating. To represent the ambient SS level for assessment of water quality impacts at WSD intakes, the 90^th percentile SS concentration for the entire period (1986 to 2012) of EPD’s monitoring data for surface and middle layers, and the depth-averaged of these two layers are adopted in the assessment. These are presented in Table 8.25.

Table 8.25: 90^th Percentile Suspended Solids from EPD Monitoring Stations Representing WSD Seawater Intakes

EPD Stations	Wet Season			Dry Season
EPD Stations	Surface	Middle	Depth Averaged	Surface	Middle	Depth Averaged
NM3	8.9	15.0	11.1	12.0	16.0	14.4
WM1	4.8	5.8	5.5	8.1	10.1	9.3
WM3	8.1	11.0	8.5	13.0	17.0	14.5

Note: Units are in mg/L. Bold values show exceedance of WSD’s SS criteria of 10 mg/L. Values rounded to 1 decimal place.

8.4.2.3 Based on the ambient SS levels summarised in Table 8.25, the allowable SS elevations at WSRs representing WSD seawater intakes (up to the WSD criterion of 10 mg/L) are summarised in Table 8.26.

Table 8.26: Allowable SS Elevations at WSD Seawater Intakes

WSRs	Associated EPD Stations	Wet Season			Dry Season
WSRs	Associated EPD Stations	Surface	Middle	Depth Averaged	Surface	Middle	Depth Averaged
C3	NM3	1.2	0.0	0.0	0.0	0.0	0.0
C12	WM1	5.2	4.2	4.5	2.0	0.0	0.8
C20	WM3	1.9	0.0	1.5	0.0	0.0	0.0

Note: Units are in mg/L. Values rounded to 1 decimal place (same as EPD’s monitoring station data).

8.4.2.4 At EPD monitoring stations where the ambient SS level already exceeds the WSD criterion for SS, any change from the existing baseline will be considered as an exceedance of the SS criterion in the assessment.

8.4.3 Sediment Deposition and Suspended Solids Criteria for Corals

8.4.3.1 It is acknowledged that corals may suffer damage to their respiratory function as a result of sediment deposition blocking the respiratory and feeding organs of these organisms. According to Hawker and Connell¹, a sedimentation rate higher than 200 g/m² per day would introduce moderate to severe impact upon all corals. As such, this limit was adopted as the assessment criterion for protecting the corals and other ecological sensitive receivers in this study.

1 Hawker, D. W. and Connell, D. W. (1992). “Standards and Criteria for Pollution Control in Coral Reef Areas” in Connell, D. W and Hawker, D. W. (eds.), Pollution in Tropical Aquatic Systems, CRC Press, Inc.

8.4.3.2 While there are no established legislative criteria for water quality for corals, an elevation criterion of SS levels less than 30 % of ambient baseline conditions¹ has been adopted as the critical value, above which impacts to the habitat may occur. This criterion has been adopted in previously approved EIA reports² for assessing SS impacts on corals.

2 Mott MacDonald (2010) Environmental Impact Assessment for Installation of Submarine Gas Pipelines and Associated Facilities from To Ka Wan to North Point for Former Kai Tak Airport Development Consultancy Services for Feasibility Study and Detailed Design, EIA Report, The Hong Kong and China Gas Company Limited

8.4.4 Suspended Solids Criterion for Fish Culture Zones

8.4.4.1 In the fish culture zones, the WQO for SS applies, i.e., elevation of SS should be less than 30 % of ambient baseline conditions.

8.4.5 Criteria for Cooling Water Discharges

8.4.5.1 Cooling water discharges are associated with thermal plumes and release of residual chlorine and biocide. The WQOs for the North Western WCZ stipulate that the temperature rise in the water column due to human activity should not exceed 2 ^oC (as shown in Table 8.2).

8.4.5.2 Chlorine is a commonly used anti-fouling agent for treatment of cooling water within the seawater cooling system. An ecotoxicology study commissioned by EPD³ found the lowest No Observable Effect Concentration (NOEC) value to be 0.02 mg/L. However, past approved EIA studies have adopted more stringent criteria such as the United States Environmental Protection Agency (USEPA) Criterion Continuous Concentration (CCC) limit of 0.0075 mg/L for residual chlorine. As ecological and fisheries sensitive receivers are the primary concern in relation to potential impacts due to residual chlorine, the USEPA criterion has been adopted for these WSRs. For cooling / flushing water intakes, residual chlorine has no impact and hence no criteria is applied to WSRs representing cooling / flushing water intakes.

3 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.

8.4.5.3 In addition to chlorine, biocide such as Drewsperse 767 is currently being used at HKIA and may also be used in small doses to control biofouling within the new system. The criterion adopted for biocide (based on amine content) is 0.1 mg/L, based on an ecotoxicology study by Ma et al. (1998)⁴ which considered this maximum permissible concentration to be acceptable from an ecotoxicology standpoint. This is consistent with the approach adopted by past approved EIA studies (e.g. Kai Tak Development EIA). For cooling / flushing water intakes, biocide has no impact and hence no criteria is applied to WSRs representing cooling / flushing water intakes.

4 S.W.Y. Ma, C.S.W. Kueh, G.W.L. Chiu, S.R. Wild, and J.Y. Yip (1998). Environmental Management of Coastal Cooling Water Discharges in Hong Kong. Wat. Sci. Tech. Vol. 38, Nos. 8-9, pp. 267-274.

8.4.6 Criteria for Dissolved Metals and Other Contaminants

8.4.6.1 For assessment of water quality impacts at WSRs for dissolved metals and organic compounds (other than the ones specified in WQOs), overseas criteria such as the European Union’s Environmental Quality Standards (EU EQS) and the USEPA’s Water Quality Criteria were adopted. A summary of the assessment criteria is shown in Table 8.27.

Table 8.27: Overseas Water Quality Criteria for Metals and Other Contaminants

Parameter (in µg/L unless otherwise stated)	Target Limit
Cadmium (Cd) ^#	0.2
Chromium (Cr)^{^}	15
Copper (Cu)*	3.1
Lead (Pb)^#	7.2
Nickel (Ni)*	8.2
Silver (Ag)^@	1.9
Zinc (Zn)^{^}	10
Mercury (Hg)^#	0.05
Metalloid (Arsenic - As)^{^}	25
TBT^#	0.0002
PCBs*	0.03
PAH^#	0.05

Source:

^{^} UK Council Directive on the quality required of shellfish waters (Shellfish Waters Directive), http://evidence.environment-agency.gov.uk/ChemicalStandards/Driver.aspx?did=13, 13 June 2013

^#Directive 2008/105/EC of the European Parliament and of the Council of 16 December 2008 on environmental quality standards in the field of water policy, http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:348:0084:0097:EN:PDF, 13 June 2013

^@ The USEPA Criteria Maximum Concentration (CMC), http://water.epa.gov/scitech/swguidance/standards/criteria/current/index.cfm#Z2, 13 June 2013

* The USEPA Criterion Continuous Concentration (CCC), http://water.epa.gov/scitech/swguidance/standards/criteria/current/index.cfm#Z2, 13 June 2013

Note: The PAH criteria is based on benzo(a)pyrene.

8.4.6.2 Other contaminants (such as nutrients) which do not have relevant local or overseas criteria were assessed against the baseline water quality from EPD’s marine water quality monitoring stations. For nutrients, the 90^th percentile values from all of EPD’s marine water quality monitoring stations in the North Western WCZ for the period between 1986 and 2012 were adopted. A summary of the assessment criteria is shown in Table 8.28.

Table 8.28: Water Quality Criteria for Nutrients

Parameter (mg/L)	Target Limit
Ammonia (NH₃-N)	0.2
Nitrite (NO₂-N)	0.12
Nitrate (NO₃-N)	0.69
Total Kjeldahl Nitrogen (TKN)	0.51
Total Phosphorus (Total P)	0.08
Ortho Phosphorus (Ortho-P)	0.04

8.5 Identification of Pollution Sources

8.5.1 Construction Phase

8.5.1.1 Construction of the project involves primarily land formation to the north of the existing airport island to provide a platform for development of the third runway and all associated airport infrastructure and facilities. Key components include approximately 650 ha of land formation, construction of a third runway and associated airfield systems and facilities, construction of a new passenger concourse, expansion or extension of existing facilities and infrastructure including Terminal 2, the automated people mover and baggage handling system, and improvements to transportation facilities on HKIA. It also requires the diversion and/or modification of some existing marine / coastal infrastructure including pipelines, cables and outfalls, and provision of new marine structures including runway approach lights and Hong Kong International Airport Approach Area (HKIAAA) marker beacons.

8.5.1.2 Potential key sources of water quality impact associated with the construction activities for the proposed project include:

¡ Land formation works including ground improvement, seawall construction and filling activities, parts of which will be constructed over the existing contaminated mud pits (CMPs) that are already capped;

¡ Modification of the existing seawall along the northern boundary of HKIA;

¡ Diversion of the submarine fuel pipelines (including marine site investigation within the Sha Chau and Lung Kwu Chau Marine Park) and diversion of the 11 kV submarine cable;

¡ Construction of new stormwater outfalls and modifications to existing outfalls;

¡ Piling activities for construction of new runway approach lights and HKIAAA marker beacons;

¡ Construction site runoff and drainage; and

¡ Sewage effluent from construction workforce and general construction activities.

8.5.1.3 The main potential water quality impact during construction phase is the release of SS during land formation (sand blanket laying and marine filling activities) and submarine cable diversion (which will occur within a marine environment). As described in Section 3.6, non-dredge methods will be adopted for land formation as this will substantially reduce the environmental impacts compared with the conventional dredging method, thereby minimising the potential water quality impacts associated with land formation from the outset. Nevertheless, while non-dredge methods will be adopted, there will inevitably still be some disturbance to the seabed during ground improvement works and other activities associated with land formation. The water jetting activities and the field joint excavation associated with the submarine cable diversion will also directly disturb the seabed. These activities may generate SS that can adversely impact marine water quality. The sand blanketing laying and marine filling activities themselves will also result in SS release to the surrounding marine environment.

8.5.1.4 For ground improvement, a combination of methods including prefabricated vertical drains (PVD), deep cement mixing (DCM), stone columns, steel cells, vertical sand drains and sand compaction piles may be adopted at different locations depending on geotechnical as well as environmental requirements. For ground improvement over the CMPs, the DCM method⁵ has been recommended as the most environmentally suitable option as it enables in-situ stabilisation of the CMPs, however, this method has not previously been adopted in Hong Kong, despite extensive use in other countries. Examples of some previous DCM applications overseas (and the findings of their water quality monitoring) are presented in Appendix 8.2. Overseas application and the local site trial of DCM held in February 2012⁶ has demonstrated that there are no adverse water quality impacts associated with this method. The findings of the DCM trial concluded that the DCM installation works did not result in any deterioration in marine water quality for the monitored parameters, and no leakage of contaminants during the course of the DCM trial. However, given the scale of the DCM ground improvement works proposed as part of this project, there may be some water quality impact due to cumulative release of small amounts of SS.

5 Note that DCM refers to a ground improvement method / technique in which cement is mixed into soil to produce a cemented soil compound with higher strength and stiffness than the original soil. Different variants of this method have been widely adopted in other countries and exist under different terms such as Cement Deep Mixing (CDM), Cutter Soil Mixing (CSM), Cement Deep Soil Mixing (CDSM), Deep Soil Mixing (DSM) or Deep Jet Mixing (DJM) (all based on the same operating principals).

6 The local site trial of DCM held in February 2012 included a comprehensive environmental monitoring programme was conducted before, during and after the DCM trial, which included in-situ testing of parameters such as dissolved oxygen, turbidity, pH, salinity, ammonia nitrogen and total alkalinity; laboratory testing of suspended solids, heavy metals and organics; as well as measurement of under-water sound levels.

8.5.1.5 The CMPs cover approximately one third of the proposed land formation area and although these have all been filled and capped and are no longer active, large volumes of contaminated mud originating from various sources elsewhere in Hong Kong have been deposited within the CMPs. Marine sediment is classified as contaminated if it contains concentrations of certain heavy metals and organics which exceed the limits specified in the sediment quality criteria under the Dumping at Sea Ordinance (DASO). The criteria for sediment quality are set out in the Practice Notes for Authorised Persons, Registered Structural Engineers and Registered Geotechnical Engineers, PNAP ADV-21 – Management Framework for Disposal of Dredged / Excavated Sediment (April 2007). As the CMPs contain the disposed marine sediment which exceeds the sediment quality criteria under DASO, higher levels of heavy metals and other contaminants such as organic chemicals are expected to be present within the CMPs. This raises concern relating to the potential release of contaminated pore water from the CMPs during the DCM process and during surcharge (when an overburden is applied to aid the settlement and consolidation of the filling materials laid over the CMPs). The DCM process was recommended as it provides in-situ strengthening of the marine sediment within the CMPs via injection and mixing of cement slurry (under a 2 m sand blanket layer), and thereby limits the amount of settlement that will occur during surcharge. This significantly reduces the amount of pore water released from the CMPs. Nevertheless, given the large area of the CMPs to be treated, potential water quality impacts due to release of contaminants from pore water remain a potential concern.

8.5.1.6 Other potential water quality impacts associated with the DCM process, such as a rise in water temperature associated with the exothermic process, is not considered to be significant as the major contact area is along the longitudinal surface of the cement-mud mixing column, thus heat dissipation would largely occur within the mud layer immediately surrounding the DCM column, which is beneath the seabed. While there would be minor heat dissipation through the upper ends of DCM columns, the heat will be absorbed by the 2 m sand blanket that will be placed on top of the seabed prior to ground improvement works. Therefore, any residual heat transfer to the water column above the sand blanket will be minimal, and potential impacts on water temperature from the DCM process would be negligible. Similarly, the potential impact on increase of contaminant release from the contaminated mud dumping process at the active CMP at East Sha Chau (due to the potential rise in water temperature in the vicinity of the DCM area, which may enhance the dissociation of contaminants from the soil matrix of the contaminated sediment) is also unlikely given the aforementioned analysis on heat transfer, in addition to the large buffer distance between the nearest boundary of the active CMP at East Sha Chau and the land formation works (nearest distance is approx. 1 km away). Thus no impact on the contaminated mud dumping process at the active CMP at East Sha Chau is anticipated due to DCM works.

8.5.1.7 For areas outside the CMPs where DCM ground improvement may not be applied, a larger quantity of pore water will likely be extruded as part of the ground improvement process in order to achieve the required consolidation of the marine sediment. This process may result in the release of nutrients or contaminants from the pore water of marine sediment in these areas.

8.5.2 Operation Phase

8.5.2.1 Potential sources of water quality impact associated with the operational activities for the proposed project include:

¡ Changes in tidal flows, direction and speed as a result of the permanent new landform;

¡ Embayment of water at western end of HKIA;

¡ Sewage discharge;

¡ Reuse of treated greywater;

¡ Spent cooling water discharge;

¡ Stormwater discharge;

¡ Accidental fuel spillage; and

¡ Potential maintenance dredging of the navigable waters north of HKIA.

8.5.2.2 The key operation phase water quality impacts relate to permanent changes to the existing tidal and current regime around the expanded airport and potential discharge of pollutants from the HKIA site.

8.5.2.3 Changes to the tidal regime can result in siltation at areas with reduced flow velocity and/or erosion of seabed and scour hole formation at areas with increased tidal velocity. The flushing capacity of the existing airport (Southern Sea) channel may also be affected. Such changes to the tidal and current regime may have impact to the existing water quality and can affect sensitive ecological habitats, such as corals and seagrass beds.

8.5.2.4 After land formation, an embayment will be formed at the western end of HKIA, between the existing north and new third runway. Potential water quality concerns associated with the embayment of water include a potential reduction in the flushing of pollutants and potential accumulation of floating refuse. Depending upon the prevailing water quality and the potential materials entrapped, this can lead to lower dissolved oxygen level and increase deposition of suspended solids. These conditions may potentially lead to the creation of anaerobic conditions, odour, and associated deterioration in water quality in extreme situations.

8.5.2.5 The discharge of stormwater and spent cooling water may contribute a pollution load to the marine environment. Pollutants typically found in stormwater runoff include sediment, heavy metals, synthetic organics (e.g., fuels, oils, solvents, lubricants) and pesticides. These substances are generated from potentially polluting activities including maintenance, fuelling, etc. Potential water quality impacts associated with discharge of the spent cooling water include increased thermal loading and release of residual chlorine and biocide into the marine environment.

8.5.2.6 Increased quantities of sewage generated by the project may create adverse water quality impacts if it is not properly conveyed to a foul sewerage system. Reuse of treated greywater may also be a potential water quality risk if not properly conveyed and treated prior to reuse.

8.5.2.7 The potential for accidental fuel spillage during operation phase of the project has been identified in the EIA Study Brief as a water quality concern to be addressed in this study. Based on the scheme design for operation of the fuel storage and transfer facilities, the risk of such incidents of accidental fuel spillage directly into the marine environment is considered to be extremely low.

8.5.2.8 The potential need for maintenance dredging of the navigable waters north of HKIA was also identified in the EIA Study Brief as a water quality concern to be addressed in this study.

8.5.2.9 All of the aforementioned potential operation phase water quality impacts are further discussed and assessed in Section 8.7.2.

8.5.3 Concurrent Projects

8.5.3.1 Potential cumulative water quality impacts of the project within the concerned WCZs, through interaction or in combination with the following projects are considered in the cumulative water quality impact assessment. Based on the review of concurrent projects presented in Section 4.5.1, the concurrent projects identified with potential cumulative water quality impacts are listed below:

¡ Container Terminal 10 Development at Southwest Tsing Yi (CT10);

¡ Development of the Integrated Waste Management Facilities (IWMF) Phase 1;

¡ Effluent Polishing Scheme at Yuen Long Sewage Treatment Works (STW);

¡ Harbour Area Treatment Scheme (HATS) - Stage 2A;

¡ Hong Kong-Zhuhai-Macao Bridge - Hong Kong Boundary Crossing Facilities (HKBCF);

¡ Hong Kong-Zhuhai-Macao Bridge - Hong Kong Link Road (HKLR);

¡ Hong Kong-Zhuhai-Macao Bridge (HZMB) – Outside HK SAR;

¡ Lantau Logistics Park (LLP);

¡ Leisure and Entertainment Node at Sunny Bay (Sunny Bay Development);

¡ New Contaminated Mud Marine Disposal Facility at HKIA East/ East Sha Chau Area (MDF);

¡ Outlying Islands Sewerage Stage 2 - upgrading of Cheung Chau and Tai O sewage collection, Treatment and Disposal Facilities (Upgrading of Tai O Sewage Collection, Treatment and Disposal Facilities) (Tai O Study);

¡ Planned developments on the existing airport island, including the Midfield development, the North Commercial District (NCD) and the Intermodal Transfer Terminus (ITT) and other airport facilities related works;

¡ Proposed Residential Development at Tung Chung (Area 54);

¡ Providing sufficient water depth at Kwai Tsing Container Basin (KTCB) and its Approach Channel;

¡ Public Housing Development at Tung Chung West (Area 39);

¡ Sludge Treatment Facilities (STF);

¡ Tonggu Channel;

¡ Tuen Mun – Chek Lap Kok Link (TM-CLKL);

¡ Tung Chung New Town Extension Study (Tung Chung Study); and

¡ West New Territories Landfill Extensions (WENT).

8.5.3.2 The status of these potential concurrent projects at the time of the study and the potential cumulative impacts are summarised in Table 8.29. Other projects listed in Section 4.5.1 are not considered for cumulative water quality impact as they either do not contribute to marine water quality impact, or there is insufficient information available at the time of preparation of this study (refer to discussions in Section 4.5.1 and Table 4.4 for details).

Concurrent Project	Latest Construction Schedule	Target Commencement of Operation Phase	Construction Phase Cumulative Impact	Operation Phase Cumulative Impact	Latest Information
Container Terminal 10 Development at Southwest Tsing Yi	Not yet available	Not yet available	No – insufficient information on construction programme and construction activities available	Yes – new land boundary and stormwater discharge incorporated	Information provided by project proponent in January and August 2013
Development of Integrated Waste Management Facilities Phase 1	Not yet available	Not yet available	N/A – no marine works associated with the Tsang Tsui site, while the Shek Kwu Chau site is outside assessment area	Yes – new land boundary and stormwater discharge incorporated	Based on communication with project proponent in January 2013. Details referred from approved EIA Report
Effluent Polishing Scheme at Yuen Long Sewage Treatment Works	Not yet available	Not yet available	No – insufficient information on construction programme and construction activities available	Yes – new discharge information incorporated	Information provided by project proponent in August 2013
Harbour Area Treatment Scheme – Stage 2A	Under construction	By 2014	No – no programme overlap	Yes – new discharge information incorporated	Based on communication with project proponent in January 2013. Details referred from approved EIA Report
Hong Kong-Zhuhai-Macao Bridge - Hong Kong Boundary Crossing Facilities	Under construction	By 2016	Yes – reclamation boundary and sediment loss incorporated	Yes – new land boundary and intake / discharge information incorporated	Based on communication with project proponent in February and August 2013. Details referred from approved EIA Report and latest VEP (EP-353/2009/G)
Hong Kong-Zhuhai-Macao Bridge - Hong Kong Link Road	Under construction	By 2016	Yes – reclamation boundary and sediment loss incorporated	Yes – new land boundary and stormwater discharge incorporated	Based on communication with project proponent in August 2013. Details referred from approved EIA Report
Hong Kong-Zhuhai-Macao Bridge – Outside HK SAR	Under construction	By 2016	No – no programme overlap	Yes – new land boundary incorporated	Project website for Hong Kong-Zhuhai-Macao Bridge http://www.hzmb.hk/
Lantau Logistics Park	Not yet available	Not yet available	Yes – reclamation boundary and sediment loss incorporated	Yes – new land boundary and intake / discharge information incorporated	Information provided by project proponent in January and September 2013
Leisure and Entertainment Node at Sunny Bay	Not yet available	Not yet available	No – insufficient information on construction programme and construction activities available	Yes – new land boundary and stormwater discharge incorporated	Referred from the 2007 Lantau Concept Plan
New Contaminated Mud Marine Disposal Facility at Airport East / East Sha Chau Area	Disposal of contaminated marine mud at South Brothers from mid 2013 to early 2016. Disposal of contaminated marine mud at CMP Vb to start after completion of filling at South Brothers	Capping of Va from early 2014 to late 2015. Capping of South Brothers to be completed by end 2016 / early 2017	Yes – bathymetry and sediment loss incorporated	Yes – new bathymetry incorporated	Updated information provided by project proponent in October 2013
Outlying Islands Sewerage Stage 2 – upgrading of Cheung Chau and Tai O sewage collection, Treatment and Disposal Facilities (Upgrading of Tai O Sewage Collection, Treatment and Disposal Facilities)	Scheduled to commence in mid 2015 (Tai O marine works)	By 2019	Yes – reclamation boundary and sediment loss incorporated	Yes – new land boundary and discharges incorporated	Information provided by project proponent in August 2013
Planned developments on the existing airport island, including the Midfield development, the North Commercial District (NCD) and the Intermodal Transfer Terminus (ITT)	Anticipated to commence in 2014/2015	Scheduled for 2017 to 2019	No – no marine works	Yes – new discharge information incorporated	Information provided by project proponent in August 2013
Proposed Residential Development at Tung Chung (Area 54)	To be confirmed	In 2019/20	No – no marine works	Yes – induced discharges incorporated	Information provided by project proponent in October 2013
Providing sufficient water depth at Kwai Tsing Container Basin and its Approach Channel	Scheduled to commence in end 2013	By 2016	Yes – bathymetry and sediment loss incorporated	Yes – new bathymetry incorporated	Based on communication with project proponent in January 2013. Details referred from approved EIA Report
Public Housing Development at Tung Chung West (Area 39)	Scheduled to commence in mid 2014	By early 2018	No – no marine works	Yes – induced discharges incorporated	Information provided by project proponent in October 2013
Sludge Treatment Facilities	Under construction	By late 2013	No – no programme overlap	Yes – new intake / discharge incorporated	Information provided by project proponent in February 2013
Tonggu Channel	Completed	In operation – maintenance dredging schedule not available	Yes – sediment loss incorporated	No – insufficient information available	Details referred from HKBCF EIA Report
Tuen Mun – Chek Lap Kok Link	Under construction	By 2016 (southern connection) and 2018 (northern connection)	No – marine works anticipated to be completed in 2014, hence no concurrent construction anticipated	Yes – new land boundary and stormwater discharge incorporated	Based on communication with project proponent in August 2013. Details referred from approved EIA Report
Tung Chung New Town Extension Study	Starting from 2018	Anticipated first population intake in 2023 / 24	Not incorporated – as the seawall for the third runway land formation would be substantially completed by end 2017, thus potential cumulative impacts would be very limited. Commencement of marine works for Tung Chung New Town Extension is also outside the worst case assessment years of the project (refer to Section 8.6.3.9)	Yes – new land boundary and intake / discharges incorporated	Based on published information from the Stage 2 Public Engagement held in May and July 2013
West New Territories Landfill Extensions (WENT)	Not yet available	Not yet available	No – no marine works	Yes – new discharge information incorporated	Information provided by project proponent in January 2013

8.6 Water Quality Assessment Methodology

8.6.1 Hydrodynamic Model for Quantitative Impact Assessment

8.6.1.1 To assess the key potential water quality impact arising from the construction and operation of the project, hydrodynamic modelling was undertaken to quantify SS and contaminant release.

8.6.1.2 The proposed hydrodynamic model adopted for this project is based on the existing, validated 3-dimensional hydrodynamic model - Western Harbour Model (WHM) derived from the Update Model by Deltares in 2000-2001. This model has been set up, calibrated and validated under previous agreements with the Government of Hong Kong and since 1996, the Update models have been applied in a large number of marine environmental studies in Hong Kong’s coastal waters, such as HKBCF, HATS Stage 2A, and Kai Tak Development. This model covers the study area for this project (i.e. the Northwestern WCZ, Northwestern Supplementary WCZ, Western Buffer WCZ, and Deep Bay WCZ), including the Pearl Estuary and the Dangan (Lema) Channel. As the model has been successfully applied in a number of past approved EIAs, including the EIA for HKBCF, (which is in close proximity to the project), this model is considered to be suitable for application in this project with some refinement.

Model Grid Refinement and Validation

8.6.1.3 To obtain the desired resolution for this project, a domain decomposition model (refined grid) was generated from the original WHM. A 3x3 domain decomposition grid was created covering the larger northern Lantau waters including Tuen Mun to the north and Tsing Yi to the west. The grid refinement and model validation results are shown in Appendix 8.3.

8.6.1.4 Four sets of runs (for both dry and wet seasons) were simulated and their results were analysed against the original WHM (Update Model) by Deltares in 2000-2001. Validation was carried out between the original WHM (Run00d and Run00w) and the refined WHM (Run01d and Run01w), and the results showed very small differences between the two models, which can be interpreted as attributed to the finer model grid. An analysis of residual flows across important channels / cross sections generally shows little change as a result of the refinement. The results of the validation demonstrates that the refined WHM is consistent with the results of the original WHM and differences are mainly the result of finer horizontal grid resolution.

8.6.1.5 Based on the validated refined WHM, hydrodynamic models was set up according to the different worst case scenarios identified for construction and operation phases. All simulations covered complete spring-neap tidal cycles in dry and wet seasons (15 days) and was preceded a spin-up period of at least 15 days to ensure the stability of flow conditions and water quality parameters had been reached.

8.6.2 Construction Phase Modelling

8.6.2.1 Construction phase simulations were based on the refined WHM grid (‘without project’), with refinements to land boundaries and bathymetry depending on the worst case years to be simulated (and associated concurrent projects).

8.6.2.2 Quantitative assessment using the Delft3D suite of mathematic models (FLOW and PART modules), was applied to quantify the water quality impacts associated with marine works, e.g. marine sand blanket, ground improvement via DCM, marine sand filling activities and water jetting / field excavation activities for the submarine 11 kV cable diversion. Quantitative assessment was carried out for SS, dissolved oxygen ‘DO’, and contaminants from pore water release, which includes nutrients (Unionised Ammonia ‘NH₃’, Nitrite ‘NO₂’, Nitrate ‘NO₃’, Total Kjeldahl Nitrogen ‘TKN’, Total Phosphorus, and Reactive Phosphorus); heavy metals (Arsenic ‘As’, Cadmium ‘Cd’, Chromium ‘Cr’, Copper ‘Cu’, Lead ‘Pb’, Mercury ‘Hg’, Nickel ‘Ni’, Silver ‘Ag’, and Zinc ‘Zn’); Poly-aromatic Hydrocarbons (PAH); Polychlorinated Biphenyls (PCB); and Tributyltin (TBT).

8.6.2.3 Other potential sources of water quality impacts would be mainly from land-based construction activities (e.g. surface runoff) that would only arise after completion of the land formation. These would be minor compared to the scale of the marine activities for land formation, hence these were not included in the model, but have been qualitatively assessed. All water quality impacts were subsequently evaluated and their impact significance was determined. Depending on the acceptability of the impact, the need for mitigation measures to reduce any identified adverse impacts in water quality to acceptable levels is discussed in Section 8.8.1.

8.6.3 Construction Phase – Determination of Worst Case Scenarios

Key Land Formation Stages and Sequence of Construction

8.6.3.1 As described in Section 8.5.1, during construction phase of the project, the key water quality impacts will mainly be due to sediment release from various construction activities, particularly the works related to land formation.

8.6.3.2 It is planned that the land formation work would be undertaken from start of late 2015 / early 2016 to mid-2022, noting that the third runway and taxiway sections (which account for the majority of the land formation) would be completed by 2020 for closure of the existing north runway and opening of the third runway by 2021. Based on the construction planning, the land formation works have been primarily divided into three main stages (as shown in Drawing No. MCL/P132/EIA/8-003). The works for each stage are described below:

¡ Stage 1 has a T-shaped footprint and consists mainly of the land formation works for the third runway, the associated west taxiways, the western support area and other supporting facilities.

¡ Stage 2 consists of land formation works for the new third runway concourse and aprons supported by facilities within the east support area.

¡ Stage 3 is the land formation area at both ends of the existing north runway associated with the new wrap-around taxiways, whereby construction activities are restricted by the need to maintain operation of the existing north runway until completion of the third runway.

8.6.3.3 Based on the land formation programme, a number of key construction periods with potential impacts to the WSRs have been identified and their details and significance are summarised in Table 8.30. Refer to Appendix 8.4 for the key land formation stages and construction plant quantities.

Table 8.30: Key stages for land formation

Case no.	Construction period	Descriptions / Reasons for Significance	Committed Concurrent Projects
1	Q1 of 2016	At the early stage of land formation, sand blanket laying and initial ground improvement works would be carried out at various works areas; the production rate is lower initially; filling is not yet commenced so no land would have been formed. Nearest WSRs are located to the north and west and on the existing airport island.	CMP at East Sha Chau and South of Brothers; HKBCF; HKLR; KTCB; Tai O Study; Tonggu Channel Maintenance Dredging
2	Q4 of 2016	Installation of steel cells around the western end of the third runway is complete and marine filling activities dominate along the western side of the land formation, while ground improvement works and seawall construction continue along the northern and southern ends. Some sand blanket laying continue at the eastern side of the land formation, while the smaller works areas immediately adjacent to the existing airport island are completed above high tide mark (and undergoing land filling). Rate of production is high when compared to Case 1. Nearest WSRs are located to the north and east of the land formation footprint.	CMP at East Sha Chau and South of Brothers; HKBCF; HKLR; KTCB; Tai O Study; Tonggu Channel Maintenance Dredging
3	Q1 of 2017	Ground improvement, seawall construction and marine filling activities behind advance seawalls dominate in the north eastern works areas with most of the southern works areas completed above high tide mark. Rate of production is highest out of all cases. Nearest WSRs are located to the north and east of the land formation footprint.	CMP at East Sha Chau; Tai O Study; Tonggu Channel Maintenance Dredging
4	Q4 of 2017	Seawall largely completed with substantial completion of ground improvement and marine filling activities; Stage 1 works areas completed above high tide mark except for the east end of the third runway; active marine filling works areas limited to the east end of the third runway and the west end of the existing north runway; production rate is lower when compared to Case 1, 2 and 3. Nearest WSRs are located to the east and southwest of the land formation footprint.	CMP at East Sha Chau; Tai O Study; Tonggu Channel Maintenance Dredging
5	Q4 of 2018	All ground improvement, seawall and marine filling activities for Stage 1 and 2 completed; remaining works entirely land-based (except for remaining Stage 3 works areas); low production rate when compared to Case 1, 2, 3 and 4. Nearest WSRs are located to the east of the land formation footprint.	CMP at East Sha Chau; Tai O Study; Tonggu Channel Maintenance Dredging
6	Q3 of 2021	All Stage 1 and 2 activities completed; remaining Stage 3 works areas undergoing primarily ground improvement, seawall construction and marine filling activities; low production rate when compared to Case 5. Nearest WSRs are those located along North Lantau.	Tonggu Channel Maintenance Dredging

8.6.3.4 Case 1 represents primarily sand blanket laying and ground improvement activities prior to construction of seawall. There is no land formation at this stage, hence no impact to the hydrodynamics of the marine environment. Sediment plumes generated from the construction activities would be governed by similar hydrodynamic flow conditions as for the existing baseline conditions.

8.6.3.5 Cases 2 and 3 are considered to be similar as they are both likely to occur near the peak of marine works for the third runway but they differ by the amount of seawall progressed and there would be a larger amount of reclaimed land for Case 3. A greater number of plant and higher production rates also occurs in Case 3, hence the latter may pose both larger sediment plumes and greater changes in hydrodynamic flow due to the presence of more land formation.

8.6.3.6 Case 4 and 5 represent near full completion of the seawall and substantial to full completion of marine filling activities. Land formation would have proceeded further in Stage 2 area for Case 5. With completion of the seawall, the land formation platform is closed off and hence sediment plumes are likely to be restricted. The hydrodynamic flow in the surrounding waters will more closely represent that of the completed land formation for the third runway.

8.6.3.7 Case 6 is not considered to be critical as in Year 2020 and afterwards, the main land formation would have been completed and the remaining works are confined to areas where strong currents are not anticipated. The remaining areas are either sheltered from the tidal current by the new land formed or surrounded by other reclaimed land. Although the works areas may be closer to some WSRs, the production rate of filling for this case is lower than other cases.

8.6.3.8 For all cases, marine filling activities will only be carried out behind an advance seawall of at least 200 m (comprising either rows of contiguous permanent steel cells completed above high tide mark or partially completed seawalls with rock core to high tide mark and filter layer on the inner side). This sequencing of marine filling activities behind an advance seawall has been adopted as a measure to reduce sediment plume dispersion in all cases when marine filling activities take place.

8.6.3.9 Based on the construction phasing, the likely worst case scenarios for water quality modelling are proposed as follows:

8.6.3.10 Worst Case Scenario A (Year 2016) – based on Case 1, where the dominant activity is sand blanket laying. While the total number of active works area is less than subsequent periods of the year, the number of works areas undergoing sand blanket laying is the highest, and the potential sediment loss rate associated with sand blanket laying is higher than that for the ground improvement works that begin to dominate in the later part of the year. Similarly, water jetting and excavation activities associated with the field joint for the diversion of the 11 kV submarine cable will be in progress, and a larger number of concurrent projects remain active during this period.

8.6.3.11 Worst Case Scenario B (Year 2017) – based on Case 3, where the dominant activity is a combination of ground improvement works and marine sand filling. Compared to other cases, Case 3 represents the largest number of active works areas for marine sand filling and well as the largest number of DCM barges in operation.

8.6.4 Construction Phase – Suspended Solids

8.6.4.1 The main construction activities that will generate SS include sand blanketing laying and marine filling, the impacts of which have been quantitatively assessed by the sediment plume model. As no dredging is required for construction of the new seawall / modification of the existing seawall and only rockfill will be used in construction of the seawall core, the potential SS release during seawall construction is considered to be insignificant. Where steel cells are used as part of seawall core construction, sand fill will be deposited directly into the steel cell structures, which are isolated from the surrounding marine waters, hence no release of SS will arise from this activity. Ground improvement activities (including use of vertical drains which have been extensively applied in Hong Kong in the past) are generally not associated with significant SS release, given that a 2 m thick sand blanket layer will be in place. However, the DCM ground improvement method has not previously been adopted in Hong Kong, hence the potential impacts due to SS release from this construction activity will also be included in the model.

Sediment Loss for DCM Column Installation

8.6.4.2 During the course of DCM column installation, no sediment loss is anticipated as the environmental monitoring results for the DCM field trial in February 2012 showed no exceedance or elevation of SS levels attributable to the installation work. Nevertheless, there was only one DCM rig involved in the trial exercise whereas up to 42 DCM rigs would be deployed in the proposed land formation. Therefore, for the purpose of sediment plume modeling for worst case scenarios, it is assumed that sediment loss would only occur when the rotating DCM auger blades are penetrating into or withdrawing from the sand blanket. No sediment loss is assumed when the DCM augers are penetrating into or withdrawing from the contaminated mud/marine mud below the sand blanket. Accordingly, the sediment loss rate for each DCM rig can be estimated based on the following assumptions:

¡ A typical working area for “square four” cluster of DCM columns = 2.2 m x 2.2 m = 4.84 m². However, larger working area sizes are also available for different DCM configurations. The largest cluster size available on the market is 6.91 m². To account for the worst case scenario, it is assumed that all DCM rigs located in land formation Stage 1 and 2 will adopt the 6.91 m² working area size, though in reality, this is very unlikely to be feasible due to market availability. For works areas located in land formation Stage 3, which are severely restricted by the existing airport operation, the largest working area for each DCM cluster limited to 3.36 m².

¡ Thickness of sand blanket = 2.0 m

¡ Estimated volume of sand agitated by the rotating auger blades during the penetration or withdrawal process = 6.91 m² x 2 m = 13.82 m³ for Stage 1 and 2 areas (6.72 m³ for Stage 3 areas)

¡ Estimated time for the DCM auger blades to penetrate through the sand blanket, taking into account the DCM field trial completed in February 2012 = 4.4 minutes or 264 seconds per DCM installation cycle (each cycle lasted for about 80 to 120 minutes during the DCM trial in February 2012). However, the fastest feasible rate of sand blanket penetration, taking into account the need for quality control of the auger speed, is 60 seconds per 1 m sand blanket. The worst case (fastest) rate of sand blanket penetration is thus 120 seconds per DCM installation cycle.

¡ Similarly, the estimated time for the DCM auger blades to completely withdraw from the sand blanket would also be 120 seconds per DCM installation cycle.

¡ Density of sand = 1,835 kg/m³, as advised by the Land Formation Scheme Design Consultant with respect to the planned material.

¡ Fine content of sand = 5 % to 10 % (the fines content of the sand agitated by the DCM is equivalent to the fines content of the sand blanket, which has an upper limit of 10 % due to the need to maintain adequate drainage properties.)

¡ Estimated sediment loss fraction = 5 % of the fine content of sand. This is a conservative assumption, as this is the assumption made in the EIA for HKBCF for filling by trailer suction hopper dredger (TSHD), which involves discharging sand at a much higher rate (7.408 m³/s) when compared to the rate of sand agitated by the auger blades (13.82 m³/120 seconds or 0.115 m³/s).

8.6.4.3 With the above assumptions, the worst case sediment loss rate for one DCM rig is estimated as:

Sediment loss rate for DCM installation in Stage 1 and 2 areas = 13.82 m³ x 1,835 kg/m³ x (5 % to 10 %) x 5 % / 120 seconds = 0.528 to 1.057 kg/s per DCM installation cycle

Sediment loss rate for DCM installation in Stage 3 area = 6.72 m³ x 1,835 kg/m³ x (5 % to 10 %) x 5 % / 120 seconds = 0.257 to 0.514 kg/s per DCM installation cycle

8.6.4.4 Note that installation of one DCM cluster comprises two ‘installation cycles’ (i.e. one cycle for penetration into sand blanket, and one for withdrawal). The estimated sediment loss rate for the higher fines content of 10 % has been adopted in the sediment plume modelling for the various worst case scenarios.

8.6.4.5 According to the environmental monitoring results for the DCM field trial carried out in February 2012, turbidity or SS levels were found to be elevated during the mobilisation and demobilisation periods when the tugboats and derrick lighter were travelling around the DCM trial site during each round of the trial. Such mobilisation and demobilisation activities were mainly stemmed from the fact that the DCM rig exceeded the Airport Height Restriction (AHR), which would affect operation of the Sha Chau radar. Thus the DCM trial had to be completed within the designated NOTAM period when the existing north runway was closed (normally between 1:30am and 7:30am) such that no disruption would be caused to the re-opening of the runway and the operations of the airport. As a result of the AHR constraint, the DCM barge was towed to the trial site to carry out the trial and was then immediately towed to leave the site upon completion of the trial, hence resulting in a lot of vessel movements during the mobilisation and demobilisation processes for every round of the trial. As a result of such vessel movements, elevated turbidity / SS levels were recorded for a short period of time during and after each round of mobilisation and demobilisation activities during the DCM trial works.

8.6.4.6 During the future full-scale DCM or similar, non-intrusive works for the proposed land formation of the Project, it is expected that the AHR will no longer be a constraint. This is because AAHK is in close liaison with Civil Aviation Department (CAD) to uplift the AHR by implementing a number of technical safeguards to ensure the continued provision of radar service is afforded through Sha Chau and other radars in the territories to maintain the current airport operation. Positive feedback had been received from CAD and firm arrangement for the implementation of the identified technical safeguards on the radar and related equipment would be subsequently confirmed. Therefore, all the DCM barges will be able to stay at the proposed land formation site for installation of DCM columns throughout the construction period, and the mobilisation / demobilisation activities as well as the associated frequent vessel movements required for the DCM trial will not occur during the full-scale DCM work. Instead, each DCM barge will be shifted from one DCM installation location to another by the action of winching the steel wires that are mounted at the barge on one end and anchored at the seabed on the other. Shifting of the DCM barges that are flat-bottomed would be done slowly and therefore no water quality impact is anticipated to arise from such barge movements. According to the Land Formation Scheme Design Consultants, it is estimated that the marine traffic incurred by the supporting vessels (e.g., tug boat) to serve the DCM barges in the full-scale DCM work would be not more than two to three trips per hour. As compared to the existing marine traffic in the vicinity of the land formation footprint (which is estimated to be about 56 movements per hour) according to the marine traffic projections by the Land Formation Scheme Design Consultant, it is anticipated the potential water quality impact due to movement of the supporting vessels would be minimal, and thus is not included in the model.

Fill Types

8.6.4.7 References have been made to the General Specifications for Civil Engineering Works 2006 and marine work specifications of the similar government projects in determining the fill types for use at the proposed land formation for the project. In general, the recommended fill types for the project comprise rock fill, public fill, sand fill, rock armour and underlayer. The acceptability of these fill materials would be controlled by a number of factors including particle size distribution, shape, material properties and the sources of acquisition. Table 8.31 summarises the properties of the recommended fill types.

Table 8.31: Summary of recommended fill types

Fill Type	Descriptions	Particle Size (mm unless otherwise specified)	% fine content by mass (with grain size < 63μm)	Estimated quantities required (Mm³)	Application areas
A	Rock Fill	31.5 – 250	0	7.5	Seawall core and underneath runway and taxiways
B	Public Fill without pre-sorting	< 250	0 – 25 *	8.6 to 20.7	Landscape areas at-grade and piled areas
C	Sand Fill	20 – 37.5	5 – 20	82.8 to 97.5	At-grade and piled areas
D	Rock Armour and Underlayer	0.3 – 5 tonnes for Rock Armour) 10 – 300 kg for Underlayer)	0	0.6	Seawall protective layer

*Note: According to the General Specification of Civil Engineering Works (CEDD, 2006), public fill materials (Type 2) suitable for land formation should have less than 25% fine content (<63 µm).

Sediment Loss for Sand Filling by TSHD

8.6.4.8 It is assumed that two different sizes of TSHD will be deployed. A number of 9,000 m³ capacity TSHDs will be deployed at the north eastern side of the land formation where it will cover the majority of Stage 2 works, while 3,700 m³ capacity TSHDs will be deployed at all other works areas. Due to water depth restrictions, filling activities using the 9,000 m³ capacity TSHDs will be carried out ‘remotely’ via a sand pipe from the TSHD to a spreader pontoon for laying the sand at the required works areas.

8.6.4.9 The sediment loss rates during sand filling can be estimated based on the following assumptions:

Sand Blanket Filling

¡ One TSHD with a discharge capacity of 1,000 m³/hr or 0.278 m³/s in a controlled manner

¡ Density of sand = 1,835 kg/m³, as advised by the Land Formation Scheme Design Consultant with respect to the planned material

¡ Fine content of sand (to be specified in the relevant works contracts) = 5 % to 10 %

¡ Estimated sediment loss fraction = 5 % of the fine content of sand. This is made reference to the assumption made in the EIA for HKBCF for filling by TSHD, which involves discharging sand at a much higher rate (7.408 m³/s).

8.6.4.10 With the above assumptions, the sediment loss rate for one TSHD is estimated as:

Sediment loss rate for sand blanket filling = 0.278 m³/s x1,835 kg/m³ x (5 % to 10 %) x 5 % = 1.275 to 2.551 kg/s per TSHD

Marine Sand Filling

¡ One TSHD with a discharge capacity of 3,000 m³/hr or 0.833 m³/s

¡ Density of sand = 1,835 kg/m³, according to the Land Formation Scheme Design Consultant

¡ Fine content of sand (to be specified in the relevant works contracts) = 5 % to 20 %

8.6.4.11 With the above assumptions, the sediment loss rate for one TSHD is estimated as:

Sediment loss rate for marine sand filling = 0.833 m³/s x1,835 kg/m³ x (5 % to 20 %) x 5 % = 3.821 to 15.286 kg/s per TSHD

8.6.4.12 The above estimated sediment loss rates for the higher fines content of 10 % for sand blanket and 20 % for sand filling was adopted in the sediment plume modelling for the various worst case scenarios. The sand is assumed to be released near the seabed.

Sediment Loss for Water Jetting (for diversion of 11kV submarine cable)

8.6.4.13 Water jetting would be deployed for the installation of the 11 kV submarine cable. The speed of the jetting machine is taken as 100 m to 500 m per day (with the higher rate assumed for worst case).

8.6.4.14 As confirmed by the Design Consultant, the maximum burial depth is assumed to be 5 m typically and will only require one pass of the jetting machine to reach the required burial depth. The jetting trench is approximately 0.45 m in width and 1 m long.

8.6.4.15 The volumes of seabed sediments to be fluidised are assumed to be:

1 Pass = 5 m x 0.45 m x 1 m = 2.25 m³/metre

8.6.4.16 Assuming volume of sediment disturbed is 2.25 m³/metre and a water jetting duration of 10 hours/ day, the rate of sediment fluidised would be:

Rate of sediment fluidized = 500 m/ day /(10 hrs/day x 3,600 secs/hr) x 2.25 m³/ m = 0.03125 m³/s

8.6.4.17 The fluidised sediments would constitute a layer of fluid mud flowing across the seabed on either side of the jetting machine and only a small portion of such sediments would enter the water column. With reference to the EIA Report for Black Point Gas Supply Project, it is conservatively assumed that 10 % of the fluidised sediments would enter the suspension.

8.6.4.18 To estimate the mass entrainment rate due to the fluidised sediments, it is necessary to apply a dry density for the material, which is taken as 900 kg/m³ (based on sediment analysis for this project). The sediments are entered into the sediment plume model in the model layer closest to the seabed because this represents the entrainment of sediments to suspension from the layer of fluid mud flowing over the existing seabed. This approach is considered valid as the jetting machine is fluidising the seabed sediments and not excavating the sediments, consequently there would be little vertical entrainment of sediments into the water column.

8.6.4.19 The sediment release in the bed layer (constitutes 10 %) of the water column is assumed in the model. These rates have been adopted in the EIA Report for Black Point Gas Supply Project. Therefore, the sediment loss rate for water jetting is estimated as:

Sediment loss rate for water jetting = 0.03125 m³/s x 900 kg/m³ x 10 % = 2. 8125 kg/s

8.6.4.20 The above estimated sediment loss was entered into the model within a series of grid cells to represent the jetting machine moving along the cable route. Thus each grid cell represented a section of the pipeline route and the estimated sediment loss was entered into that grid cell for the length of time it takes the jetting machine to pass the length of that cell, based on the jetting machine speed given above. Once the jetting machine has passed that grid cell, the estimated sediment loss will then be entered into the next grid cell on the route.

Sediment Loss for Field Joint Excavation (for diversion of 11kV submarine cable)

8.6.4.21 Field joint excavation will be performed to connect the new 11 kV submarine cable with the existing cable. The dredging rate of the field joint excavation is estimated to be 200 to 300 m³/day. This slow rate is required to ensure that the existing cable is not damaged by the dredging activities.

8.6.4.22 With reference to the EIA Report for HKZM BCF, it is conservatively assumed that 20 kg/m³ of sediment release per turn using grab dredger.

8.6.4.23 Assuming a conservative case for dredging duration of 10 hours per day at 300 m³ per day, the rate of sediment loss would be:

Rate of sediment loss (at 300 m³/day) =300 m³/day / (10 hrs/day x 3,600 secs/hr) x 20 kg/m³ = 0.167 kg/s

Worst Case Scenarios for Sediment Release

8.6.4.24 The two worst case scenarios identified were simulated using sediment plume models for wet and dry season. A description of the worst case scenario assumptions are shown in Table 8.32. Sediment loss rates adopted in the model are presented in Appendix 8.6. For modelling purpose, construction plants were assumed to be located at the outer edges of their works areas, which is the shortest distance from nearby WSRs, and hence would represent a worst case configuration. The configuration of the construction activities used to generate the worst case scenarios are shown in Drawing No. MCL/P132/EIA/8-004 and MCL/P132/EIA/8-005.

Table 8.32: Proposed Worst Case Scenarios for Land Formation Works

Worst Case Scenarios	Land formation period represented	Descriptions		Locations of ground improvement works and filling works
A (Year 2016)	Q1 2016 to Q3 2016	Assuming no land formation yet. Highest production rates to be adopted include: ¡ Sand blanket using TSHD = 18 nos. (total productivity of approx. 115,000 m³/day) ¡ DCM barges = 5 rigs/day	Central parts of Stage 1 and southern side of Stage 2
B (Year 2017)	Q4 of 2016 to Q3 of 2017	Assuming land formation at the centre part of Stage 1 and partial seawall along the runway. Highest production rates adopted include: ¡ Sand blanket using TSHD = 1 nos. (total productivity of approx. 9,000 m³/day) ¡ DCM barges = up to 42 rigs/day* ¡ Marine sand filling using TSHD = 31 nos. (total productivity of approx. 222,000 m³/day)	Western and eastern ends of Stage 1 and eastern side of Stage 2 land formation area

*Note: The number of DCM rigs assumed for this scenario has included a 30% contingency in the event of programme delays, thereby representing a very worst case assumption. For detailed calculations, refer to Appendix 8.6.

TSHD – Trailer suction hopper dredger

8.6.4.25 The proposed diversion of submarine cable via water jetting is scheduled to commence in advance of the land formation works for the third runway and would last for approximately 12 months. As there is partial overlap of the construction programmes in Q1 and Q2 of 2016, it is proposed that the worst case scenario C as detailed in Table 8.33 be simulated as a concurrent project with worst case scenario A as defined in Table 8.32.

Table 8.33: Proposed Worst Case Scenario for Submarine 11 kV Cable Diversion

Worst Case Scenario	Installation period represented	Descriptions	Location of water jetting works
C (Year 2016)	Q2 of 2015 to Q2 2016	Production rates adopted: ¡ Water Jetting Machine = 1 plant working at a rate of 500 m/day ¡ Grab dredger = 1 boat working at a rate of 300 m³/day	Connection point to the south of SCLKC Marine Park

Worst Case Scenario

Installation period represented

Descriptions

Location of water jetting works

C (Year 2016)

Q2 of 2015 to Q2 2016

Production rates adopted:

¡ Water Jetting Machine = 1 plant working at a rate of 500 m/day

¡ Grab dredger = 1 boat working at a rate of 300 m³/day

Connection point to the south of

SCLKC Marine Park

8.6.4.26 A summary of the sediment loss rates adopted for sediment plume modelling is presented in Table 8.34.

Table 8.34: Summary of sediment loss rates from Worst Case Scenarios

Activity	Sediment Loss Rate (kg/s)	Duration
Sand blanket laying by TSHD¹	2.551	3.7 hours per cycle (for 3,700 m TSHD) 9 hours per cycle (for 9,000 m TSHD)
Ground improvement by DCM¹	1.057 (Stage 1 and 2 works areas) 0.514 (Stage 3 works areas)	2 mins per cycle, with up to 60 cycles (i.e. up to 30 clusters) per plant per day
Marine sand filling by TSHD²	15.286	1 hour per cycle, with 2.5 trips per plant per day
Water jetting for diversion of the 11 kV submarine cable	2.8125	Continuous for 10 hours / day
Field joint excavation for diversion of the 11 kV submarine cable	0.167	Continuous for 10 hours / day

¹ assumes a fines content of 10%

² assumes a fines content of 20%

8.6.4.27 The concurrent projects identified in Section 8.5.3 have been incorporated into the quantitative assessment and details of the assumptions and calculations for sediment release are presented in Appendix 8.5.

8.6.4.28 Based on the worst case scenarios identified above, hydrodynamic models were set up for construction phase scenarios representing the Year 2016 and 2017 (with updated coastline, bathymetry and new land formation taking into account concurrent projects). The description of the model setup and each model run is shown in Appendix 8.6.

Water Quality Impacts due to Suspended Solids Release

8.6.4.29 For assessment of water quality impacts associated with sediment release during construction phase, the effects on dissolved oxygen, nutrients and other contaminants will be derived from the calculated SS elevations for water jetting and excavation of marine sediments at the field joint area for the diversion of submarine cable.

8.6.4.30 For dissolved oxygen (DO), DO depletion will be calculated from the following equation:

DO_Dep = C * SOD * K * 0.001

where DO_Dep =dissolved oxygen depletion (mg/L)

C = suspended solids concentration (kg/m³)

SOD = sediment oxygen demand

K = daily oxygen uptake factor (set at 1.0 for worst case estimate)

8.6.4.31 Sediment sampling and testing was undertaken in December 2012 for the proposed submarine cable diversion alignment and the field joint location. The highest SOD measured in the sediment samples collected from the 21 sampling locations along the proposed submarine cable alignment and field joint location was 2,230 mg/kg. This value is adopted for calculation of DO depletion due to the water jetting and excavation of marine sediments at the field joint area for the diversion of submarine cable. The results are presented in Table 8.65 and Table 8.66.

8.6.4.32 For other water quality parameters, elutriate tests are referred to identify whether there would be any exceedances of specific water quality parameters at the source. Where there are no exceedances from the elutriate tests, it can be inferred that concentrations at WSRs will also be below the relevant criteria limits, given the effects of dilution.

8.6.4.33 The results of the elutriate tests are shown in Table 8.35.

Table 8.35: Summary of Elutriate Test Results from the Submarine Cable Alignment

Parameter				Concentration	Criteria / Baseline*	Exceedance
	Unit	Max	Min	Average
Cd	(ug/L)	<0.2	<0.2	<0.2	0.2	No
Cr	(ug/L)	<1	<1	<1	15	No
Cu	(ug/L)	2	<1	<1	3.1	No
Pb	(ug/L)	1	<1	<1	7.2	No
Ni	(ug/L)	2	<1	<1	8.2	No
Ag	(ug/L)	<1	<1	<1	1.9	No
Zn	(ug/L)	5	<1	<1	10	No
Hg	(ug/L)	<0.1	<0.1	<0.1	0.05	Possible
As	(ug/L)	41	2	8	25	Yes
Tributyltin	(ug TBT/L)	<0.015	<0.015	<0.015	0.0002	Possible
NH₃-N	(mg/L)	7.60	0.10	1.48	0.2	Yes
NO₂-N	(mg/L)	0.08	<0.1	0.04	0.12	No
NO₃-N	(mg/L)	0.67	0.07	0.27	0.69	Yes
TKN	(mg/L)	10.3	0.2	2.1	0.51	Yes
Total P	(mg/L)	0.6	<0.1	<0.2	0.08	Yes
Ortho-P	(mg/L)	0.16	<0.01	<0.05	0.04	Yes
Total PCBs	(ug/L)	<0.18	<0.18	<0.18	0.03	Possible
Total PAHs	(ug/L)	<6.8	<6.8	<6.8	0.05	Possible

Note: * For metals and non-nutrients, the criteria is taken from Table 8.27. For nutrients, the criteria is taken from Table 8.28.

Where the exceedance is denoted as ‘Possible’, this is due to contaminants with criteria concentrations that are below detection limit, thus the detection limit value is assumed for water quality assessment.

8.6.4.34 For those nutrient and contaminant concentrations showing exceedance or possible exceedance at source, the concentrations at individual WSRs were determined based on the dilution potential derived from the water jetting and excavation activities associated with the submarine cable diversion. Taking the SS release at the source as presented in Table 8.34 as the ‘tracer’ and assuming conservative, non-settling properties, the worst case scenario ‘C’ only was modelled using the PART model for both wet and dry season for a period of 45 days. Subsequent comparison between the release rate at the source and the resultant concentration at the model grid cell representing each WSR enables a dilution potential to be determined. The dilution potential for each WSR is then applied to water quality parameters showing exceedance in order to estimate the contaminant concentration at each WSR. The results are presented in Table 8.67 and Table 8.68.

8.6.4.35 It should be noted that for the ground treatment and sand filling activities, clean sand will be sourced to form the sand blanket and the marine / land fill, therefore, no depletion of dissolved oxygen or release of nutrients and contaminants will be associated with the elevated SS concentrations due to sand blanket laying and marine filling activities.

8.6.5 Construction Phase – Release of Contaminants from Pore Water

8.6.5.1 Pore water tests have been proposed as part of the Sediment Sampling and Testing Plan (SSTP) for this project. The locations of the vibrocore samples taken are shown in Drawing No. MCL/P132/EIA/8-006. For CMP areas, a representative vibrocore was taken from each pit that overlaps the project boundary, while for non-CMP areas, representative vibrocore samples were taken along the southern and western parts of the land formation extent which covers the areas that lie outside the CMPs.

8.6.5.2 To determine the types and concentration of contaminants that may be released from pore water in both CMP and non-CMP areas, a weighted average approach was adopted as both the contaminant concentrations and the amount of pore water that could be extracted from individual subsamples at each depth varies greatly within a vibrocore. By using the weighted average approach, the contaminant concentrations at individual subsamples can be more accurately captured and combined with the results at other subsampled depths to provide a representative concentration for each vibrocore. Subsequent adoption of the maximum contaminant concentration out of the weighted average from each vibrocore produces a more worst case contaminant concentration for representing the CMP versus non-CMP areas in the assessment. A summary of the contaminant concentration results is shown in Table 8.36.

Table 8.36: Summary of Contaminant Concentrations from Pore Water Samples at CMP and Non-CMP areas

Parameter	Unit	Maximum Weighted-Average Concentration in CMP Area	Maximum Weighted-Average Concentration in non-CMP Area
Cd	(ug/L)	0.217	0.2
Cr	(ug/L)	1.345	1
Cu	(ug/L)	4.519	1.352
Pb	(ug/L)	1.171	1.172
Ni	(ug/L)	5.788	2.046
Ag	(ug/L)	1	1.221
Zn	(ug/L)	5.744	3.862
Hg	(ug/L)	0.1	0.1
As	(ug/L)	46.76	57.03
Tributyltin	(ug TBT/L)	0.013	0.013
NH₃-N	(mg/L)	41.85	21.34
NO₂-N	(mg/L)	0.01	0.011
NO₃-N	(mg/L)	0.02	0.014
TKN	(mg/L)	45.8	23.49
Total P	(mg/L)	0.948	1.033
Ortho-P	(mg/L)	0.785	0.578
Total PCBs	(ug/L)	0.18	0.18
Total PAHs	(ug/L)	6.8	6.8

Note: For each vibrocore, the concentrations are weighted by the pore water volumes extracted from each subsample at each depth to obtain a weighted average concentration for each vibrocore. The maximum concentration (out of the weighted average from each vibrocore) for each contaminant within the CMP / non-CMP areas is shown.

8.6.5.3 The proposed approach to assessing contaminant release from pore water during the DCM ground improvement works, as well as during surcharge, are described below.

Contaminant Release from Pore Water during DCM Process

8.6.5.4 The potential release of contaminants in pore water due to land formation activities over the CMPs has been identified as a water quality issue. Potential release of contaminants during the course of DCM or similar, non-intrusive methods may occur during construction phase. While the comprehensive water quality monitoring results of the DCM trial completed in early 2012 have demonstrated that there would be no leakage of contaminants from the CMP during the trial, the limited scale of the DCM trial cannot represent the cumulative impacts when a large number of DCM rigs will be operating simultaneously over the CMP area. To take into account the potential release of contaminants during the DCM process, the hypothetical case of 100 % release of pore water from the CMPs was developed based on the pore water tests conducted by the laboratory. It should be noted that the laboratory used a high speed centrifugal process to squeeze out the pore water from the vibrocore samples. In reality, the rate of agitation of the contaminated mud during the DCM process would be much slower, hence the adoption of a 100 % pore water release represents an absolute worst case.

8.6.5.5 To calculate the maximum pore water content of the CMPs, the depth-averaged maximum volume of pore water that was extracted by the laboratory is compared to the total volume of the vibrocore sample. Table 8.37 shows that pore water (that can be released from the laboratory process) comprises up to 1.3 % of the total volume of the vibrocore sample.

Table 8.37: Pore Water Content of Vibrocore Samples from CMPs

Vibrocore Samples within CMP Area	Total Pore Water Content (l)	Total Sample Volume (m³)	Depth-Averaged Pore Water Content (%)
AV03	1	0.118	0.849
AV08	1.29	0.118	1.095
AV09	1.53	0.118	1.299
AV10	0.58	0.118	0.492
AV01	0.47	0.141	0.332
AV02	1.61	0.141	1.139
AV04	0.78	0.141	0.552
AV05	0.43	0.141	0.304
AV06	0.37	0.141	0.262
AV07	1.29	0.141	0.912
AV11	0.66	0.141	0.467

Note: Bold value denotes the highest depth-averaged pore water content obtained from the vibrocore samples.

8.6.5.6 Based on the maximum pore water that can be extracted from the laboratory, the rate of pore water release is calculated by the following equation:

Rate of pore water release (per DCM cluster) = (total volume of marine sediment agitated x pore water fraction) / DCM installation time

8.6.5.7 The following worst case assumptions are applied to the DCM process:

¡ Area of CMP agitated by each DCM cluster (based on worst case) = 6.91 m².

¡ Maximum depth of CMP = 30 m

¡ Shortest time required for installation of one DCM cluster = 48 minutes or 2,880 seconds

8.6.5.8 With the above assumptions, the rate of pore water release for one DCM cluster is estimated as:

Rate of pore water release (per DCM cluster) = ((6.91 m² x 30 m) x 0.013) / 2,880 seconds

= 0.00094 m³/s or 0.936 L/s

8.6.5.9 The rate of release of contaminants from pore water during the DCM ground treatment process (i.e. the contaminant release rate ‘R’) can then be determined by multiplying the rate of pore water release with the pore water concentration for each contaminant. The calculated release rates are summarised in Table 8.38. The higher value out of the CMP / non-CMP area is adopted to represent the maximum release rate for assessment.

Table 8.38: Summary of Rate of Release for Contaminants from Pore Water

Parameter	Unit	Release Rate		Maximum Release Rate
		CMP Area	non-CMP Area	‘R’
Cd	(ug/s)	0.203	0.187	0.203
Cr	(ug/s)	1.259	0.936	1.259
Cu	(ug/s)	4.230	1.265	4.230
Pb	(ug/s)	1.096	1.097	1.097
Ni	(ug/s)	5.418	1.915	5.418
Ag	(ug/s)	0.936	1.143	1.143
Zn	(ug/s)	5.376	3.615	5.376
Hg	(ug/s)	0.094	0.094	0.094
As	(ug/s)	43.767	53.380	53.380
Tributyltin	(ug TBT/s)	0.012	0.012	0.012
NH₃-N	(mg/s)	39.172	19.974	39.172
NO₂-N	(mg/s)	0.009	0.010	0.010
NO₃-N	(mg/s)	0.019	0.013	0.019
TKN	(mg/s)	42.869	21.987	42.869
Total P	(mg/s)	0.887	0.967	0.967
Ortho-P	(mg/s)	0.735	0.541	0.735
Total PCBs	(ug/s)	0.168	0.168	0.168
Total PAHs	(ug/s)	6.365	6.365	6.365

Note: values are rounded to three decimal place.

8.6.5.10 It should be noted that the aforementioned calculation assumes that one DCM cluster can be installed in 48 minutes (based on the maximum productivity of 30 clusters per day, however in reality, the number of DCM clusters that can be installed each day is proportional to the depth of the marine sediment, whereby the thicker the mud layer, the longer it takes for a complete DCM cluster to be completed. Consequently, for a CMP with depth of 30 m, it would not be possible to complete the DCM cluster within such a short period of time. The collective assumptions adopted for calculation of pore water release rate is thus representative of an absolute worst case that is unlikely to occur.

8.6.5.11 Similar to the method proposed for quantitative assessment of contaminants associated with sediment release, the release of contaminants from pore water during DCM works was modelled using a conservative tracer. Based on the worst case sediment loss scenario with the highest number of DCM in operation (Worst Case Scenario B), a separate model was prepared containing only DCM sources. A unit release at each source (1 kg/s) was assumed for each DCM rig, and the PART model was run for both wet and dry season for a period of 45 days. The resultant maximum tracer ‘concentration’ ‘C’ (in mg/L) identified at each WSR represents the dilution arising from the ‘N’ nos. of DCM rigs in operation. The unit dilution ‘F’ is thus N / C.

8.6.5.12 The contaminant release rate ‘R’ is derived from the calculated pore water release rate multiplied by the contaminant concentration obtained from laboratory testing of vibrocore samples (see Table 8.38). Under Scenario B (with 42 DCM rigs in operation), total release of contaminated pore water ‘R_T’= 42 x R.

8.6.5.13 The theoretical contaminant concentration at the nearest WSR can then be obtained by the following equation:

Contaminant concentration at the nearest WSR = R_T / F

8.6.5.14 Based on this method, the dilution results are presented in Table 8.69 and Table 8.70.

Contaminant Release from Pore Water during Surcharge

8.6.5.15 During surcharge of the new land formation, some pore water from the CMP areas may be extruded, allowing release of contaminants. Non-CMP areas will be treated by various ground improvement methods (e.g. PVD, sand drain, stone columns, etc.) that will involve extrusion of pore water during surcharge, hence the potential release of contaminants outside the CMPs were also assessed.

8.6.5.16 At the CMP areas, which will be treated by DCM or similar, non-intrusive methods prior to filling and surcharge, the amount of pore water that may be released from the CMPs is small based on the volume of settlement that will result from surcharge over the CMPs.

8.6.5.17 The following assumptions and calculations for pore water release during surcharge were applied to the CMP area:

¡ Area of CMP to be treated by DCM = 2,770,000 m².

¡ Settlement of untreated CMP between DCM clusters = 0.3 m

¡ Improvement ratio of DCM in CMP = 32 % (i.e. 68 % of the CMP will not be mixed with DCM)

8.6.5.18 Total volume of pore water release from CMP area = 2,770,000 m² x 0.3 m x 68 % = 565,080 m³

8.6.5.19 The surcharge process will take place over a period of 3 months (assume 90 days), and during this time, the degree of consolidation is expected to be 50 %, therefore, the pore water release rate can be calculated as:

Rate of pore water release from CMP during surcharge = (565,080 m³x 50 %) / (90 x 24 x 60 x 60)

= 0.036 m³/s

8.6.5.20 After removal of surcharge, consolidation will continue at a much slower rate for up to 50 years, but this is considered to be insignificant compared to the consolidation rate during surcharge, hence the consolidation during operation phase will not be included in the analysis.

8.6.5.21 At the non-CMP areas, extrusion of pore water will occur at a faster rate. It is estimated that the volume of water which would be extruded from the various ground improvement processes is approximately equal to the settled volume.

8.6.5.22 The following assumptions and calculations for pore water release during surcharge were applied to the non-CMP area:

¡ Non-CMP area to be treated = 3,720,000 m².

¡ Average settlement of marine mud over the non-CMP area = 2.57 m

8.6.5.23 Total volume of pore water release from non-CMP area = 3,720,000 m² x 2.57 m = 9,560,400 m³

8.6.5.24 The surcharge process will take place over a period of 6 months (assume 180 days), and during this time, the degree of consolidation is expected to be 90 %, therefore, the pore water release rate can be calculated as:

Rate of pore water release from non-CMP area during surcharge = (9,560,400 m³x 90 %) / (180 x 24 x 60 x 60) = 0.554 m³/s

8.6.5.25 After removal of surcharge, the remaining 10 % consolidation will occur during a 50 year timespan, thus is considered to be insignificant and will not be included in the analysis.

8.6.5.26 The calculated pore water release rates for both the CMP and non-CMP areas occur collectively for the whole land formation area, however, the area of release to the marine environment will be confined to the boundary of the land formation (i.e. the seawall area below high tide mark), and there is likely to be some mixing of the pore water from the CMP and non-CMP areas before release. The total pore water release from the whole land formation area would thus be approximately 0.590 m³/s. Given the total length of new seawall is approx. 13 km, and the average depth to mean sea level is approx. 7.5 m, the unit release rate of pore water from the land formation can be calculated as follows:

Unit release rate of pore water from land formation = total pore water release rate / area of seawall

= 0.590 m³/s / (13,000 m x 7.5 m) = 6.05x10^-6 m/s

8.6.5.27 This pore water release rate is compared to the modelled average flow speed of the bottom layer around the new land formation to determine the dilution potential and consequently, whether any exceedance of water quality criteria would be expected at WSRs. The findings are presented in Table 8.71.

8.6.6 Operation Phase Modelling

8.6.6.1 Operation phase simulations were based on the refined WHM grid (‘with project’, whereby the project boundary as well as the land boundary for the HKBCF and the HKLR are now land masses and thus have been removed from the refined grid, and the boundary grid cells along the project land boundary has been smoothed within the confines of the domain decomposition), with associated refinements to land boundaries and bathymetry taking into account concurrent projects.

8.6.6.2 Quantitative assessment using the mathematical model, Delft3D suite (FLOW, PART and WAQ), was applied to quantify the impacts under normal operation, such as changes in tidal flows, direction and speed, embayment of water at western end of HKIA, sewage discharge, spent cooling water discharge, and stormwater discharge from the project. All water quality impacts were then evaluated and their impact significance was determined. Depending on the acceptability of the impact, the need for mitigation measures to reduce any identified adverse impacts in water quality to acceptable levels is discussed in Section 8.8.2.

Determination of Assessment Year

8.6.6.3 Land formation activities associated with the project are anticipated to be completed by Year 2023, and full operation of the three-runway system is targeted before 2030.

8.6.6.4 Major projects currently under construction, including the TM-CLKL, HKBCF, HKLR, Sludge Treatment Facilities, and HATS 2A are expected to be completed and in operation before or by end 2016. The Tai O Study is targeted for completion by 2019, while the first population intake for Tung Chung Study is targeted for 2021/22. Other major projects currently under planning, including LLP, IWMF and WENT do not yet have a confirmed completion date, but may be assumed to be operational by 2026.

8.6.6.5 For concurrent projects with no land formation or intake / outfalls but will nevertheless affect the bathymetry of the study area, such as KTCB and MDF (South of The Brothers), both projects are anticipated to be completed by end 2016. The timeline for completion of the MDF (East of Sha Chau) would depend on future demand for contaminated mud disposal, however, disposal at this location is likely to be completed by Year 2020, though capping works will continue until completion.

8.6.6.6 Given the above, it may be assumed that by the Year 2026, all existing and committed projects will be operational. The HKBCF EIA also assumed the Year 2026 as the worst case year for pollution loading. Thus the Year 2026 has been adopted for water quality modelling for the ‘with’ and ‘without project’ operation phase scenarios. Details of the model scenarios are shown in Appendix 8.6.

Incorporation of Concurrent Projects

8.6.6.7 During operation phase, the main contributions from concurrent projects mainly fall within three main categories: changes to land boundaries due to reclamation, changes to bathymetry due to dredging / filling operations, and changes to pollution loading due to various discharges including storm water, sewage and spent cooling water. Based on the concurrent projects identified in Section 8.5.3, Table 8.39 summarises the relevant aspects of each applicable concurrent project that will be incorporated into the operation phase models.

Table 8.39: Summary of Concurrent Projects incorporated into Operation Phase Model

Concurrent Project	Land Boundary	Bathymetry	Pollution Loading
CT10	Yes	N/A	Storm water
IWMF	Yes	N/A	Storm water
Yuen Long STW			Sewage
HATS 2A	N/A	N/A	Sewage
HKBCF	Yes	N/A	Storm water Sewage
HKLR	Yes²	N/A	Storm water¹
HZMB – Outside HK SAR	Yes	N/A	N/A
LLP	Yes	N/A	Storm water Sewage³
Sunny Bay Development	Yes	N/A	Storm water
MDF	N/A	Yes	N/A
Tai O Study	Yes	N/A	Sewage
NCD / ITT	N/A	N/A	Storm water¹ Spent cooling water Sewage³
Tung Chung Area 54	N/A	N/A	Storm water Sewage³
KTCB	N/A	Yes	N/A
PRH Tung Chung Area 39	N/A	N/A	Storm water Sewage³
STF	N/A	N/A	Storm water
TM-CLKL	Yes²	N/A	Storm water
Tung Chung Study	Yes	N/A	Storm water Sewage³
WENT	N/A	N/A	Storm water Sewage³

1. Part of updated HKIA storm water load.

2. Excluding the bridge piers, as the potential impact to hydrodynamics associated with these structures are considered to be insignificant.

3. Incorporated as part of the loading from the relevant STW.

8.6.6.8 The land boundaries for concurrent projects can be referred in Drawing No. MCL/P132/EIA/4-008. Bathymetry changes due to KTCB assumes the completion depth of -17.5 mCD for the dredged area, as specified in the approved KTCB EIA, while the bathymetry at the MDF sites at East Sha Chau and South of the Brothers are assumed to be restored to the same level as the surrounding seabed, as specified in the approved MDF EIA. The pollution loading from concurrent projects are incorporated into the pollution loading inventory, presented in Appendix 8.7.

Operation Phase Hydrodynamic Model

8.6.6.9 Tidal flow simulations have incorporated the changes to bathymetry and/or land boundary resulting from operation of relevant concurrent projects as shown in Table 8.39, which are assumed to be operational in the Year 2026 for the ‘with project’ and ‘without project’ scenarios. The Delft3D-FLOW model simulations cover a complete spring-neap tidal cycle in dry and wet seasons (15 days) and were preceded by a spin-up period to ensure the stability of flow conditions and water quality parameters had been reached. The FLOW simulations directly modelled the thermal plumes associated with the spent cooling water discharge from HKIA. The output from the FLOW models also provide the hydrodynamic forcing for the annual water quality (Delft3D-WAQ) models.

8.6.7 Operation Phase Thermal Plume Discharge

8.6.7.1 During the operational phase, seawater will be utilised to carry waste heat from the air conditioning system of HKIA and after being circulated through the system, this ‘heated’ seawater will be discharged from the cooling systems and returned back to the sea.

8.6.7.2 Currently, there are two seawater pumping houses with associated seawater intakes located at the northeastern end of the airport island (SWPH-1) and halfway along the airport’s southern perimeter road (SWPH-5), which supply cooling water to HKIA and Airport Authority buildings. With implementation of the third runway, SWPH-5 will continue to operate as before (i.e. no change with or without the third runway project), while SWPH-1 will need to be expanded to cope with the additional demands from the expanded Terminal 2 operation. Several schemes for meeting the future cooling demand from both the expanded Terminal 2 and the new third runway facilities are under consideration. Based on the initial scheme design, it is assumed that the existing SWPH-1 will be relocated and expanded to serve the needs of the existing HKIA plus expanded Terminal 2, while a new seawater pumping house (SWPH-7) will be provisioned to meet the additional capacity requirements of the third runway facilities (e.g. the third runway concourse and ancillary facilities).

8.6.7.3 The existing eastern seawater pump house (SWPH-1) provided a peak load of 4,255 L/s of water to the existing terminal buildings for cooling in 2012. The discharge for the existing spent cooling water outlets at HKIA are summarised in Table 8.40. The maximum temperature from the existing spent cooling is about 4^oC higher than the maximum background marine water quality, while the average temperature of the spent cooling water is well within the range of the background marine water quality as per EPD’s monitoring stations. It should be noted that the higher water temperatures were recorded in the summer months (Aug 2011 and Jul 2012), when the background marine water temperature is also relatively high.

Table 8.40: Results from HKIA Environmental Monitoring Data for Spent Cooling Water from Aug 2011 to Jul 2012

	Results
Parameters	Average	Max	Min
Daily Usage (m³)	148,817	285,941	14,250
Temp (^oC)	26.5	34.9	14
Total residual Chlorine (mg/L)	0.3	0.5	0
Biocide (mg/L)	1-2	2	1

Without Project Scenario

8.6.7.4 Under the ‘without project’ scenario, the existing seawater pumping house (SWPH-1) located at the northeastern end of the airport island will continue to operate as before, except the intake capacity may be increased to enable SWPH-1 to also handle the future cooling demands from the proposed NCD development. Based on communications with the project proponent, the seawater cooling demands associated with the NCD is anticipated to be up to 5,368 L/s. The existing thermal discharges from SWPH-1 would not be affected by the increased capacity of SWPH-1, as the additional discharge component due to NCD will be routed separately to another discharge point. Table 8.41 summarises the discharge parameters for the ‘without project’ scenario.

Table 8.41: Summary of Spent Cooling Discharge Parameters for ‘without Project’ scenario

Design Parameters	SWPH-1	NCD* (Concurrent Project)
Peak Flow	4255 L/s	5368 L/s
Temperature of spent cooling water discharge	5^oC above ambient	5^oC above ambient
Assumed ambient water temperature	25^oC (dry season) 30^oC (wet season)	25^oC (dry season) 30^oC (wet season)
Discharge point	Existing stormwater outfall No.7	Existing stormwater outfall No.8

* Based on communications with the project proponent, however, details of the discharges and discharge point are subject to further detailed design and may change.

8.6.7.5 The diurnal loading pattern and discharge rates of the existing SWPH-1 (based on monitored loading patterns during the peak flow in 2012) and the assumed diurnal loading pattern and corresponding discharge rates for the NCD (based on communication with the project proponent) are shown in Table 8.42 and Table 8.43 respectively.

Table 8.42: Diurnal Pattern for the for ‘without Project’ scenario (SWPH-1)

Time	Percentage of peak loading	Model Value (L/s)
0000 to 0200	75%	2,979
0200 to 0500	50%	2,128
0500 to 0600	70%	2,979
0600 to 0000	100%	4,255

Table 8.43: Diurnal Pattern for the for ‘without Project’ scenario (NCD)

Time	Percentage of peak loading*	Model Value (L/s)
0000 to 0200	75%	4,026
0200 to 0500	50%	2,684
0500 to 0600	70%	3,758
0600 to 0000	100%	5,368

* Based on communications with the project proponent, however, details of the discharges and discharge point are subject to further detailed design and may change.

With Project Scenario

8.6.7.6 Under the ‘with project’ scenario, the cooling demand from the existing SWPH-1 is expected to increase due to the expanded Terminal 2. Based on the initial scheme design for the Terminal 2 expansion, an additional 2,815 L/s will be supplied as part of the expanded SWPH-1. Consequently, the total peak load to be supplied by SWPH-1 during operation of the project is approx. 7070 L/s.

8.6.7.7 In addition, a new seawater pumping house (SWPH-7) and associated seawater intakes for the third runway facilities will likely be situated on the east side of the third runway. The indicative location of the proposed new intake are shown in Drawing No. MCL/P132/EIA/8-008. The location of the seawater intake will be at least 100 m away from the existing outfalls per design requirements. As advised by the infrastructure scheme design consultant for the third runway project, there will be no new outfall for discharge of spent cooling water, as this will be connected to the local stormwater drainage system for discharge at the nearest stormwater outfall. This is likely to be via a new stormwater outfall located along the northeastern boundary of the third runway (nearest to the new third runway passenger concourse). The estimated cooling demand for these new facilities are presented in Table 8.44.

Table 8.44: Estimated Cooling Demand for New Facilities associated with the Third Runway

Third Runway Facilities	Estimated Cooling Demand (Ultimate Design Scenario)
Third Runway Concourse (assuming a commercial floor area of 350,000m² and a peak occupancy of 15,000 people)	60 MW / 17,000 TR
East Support Area	5.3 MW / 1,501 TR
West Support Area	3.8 MW / 1,092 TR
Total	69.1 MW / 19,593 TR
Total + 5 % uncertainty margin due to preliminary design	72.6 MW / 20,573 TR

Note: TR = Tons of Refrigeration

1. The above preliminary cooling demand will be subjected to adjustment during the initial scheme design and scheme design development.

2. The above estimated cooling load has included a 20 % plant sizing allowance.

3. Values have been rounded to the nearest decimal place

8.6.7.8 Using the aforementioned cooling demands, the preliminary calculations of the loading from the new third runway facilities are shown below.

Q_p = (D_p x H_r) / C / ΔT

where Q_p =peak cooling discharge (L/s)

D_p = peak cooling demand (kJ/s)

H_r = chiller heat rejection rate (taken as 120 %)

C = specific heat capacity of seawater (specified as 3.925 kJ/kg/K)

ΔT = change in temperature (K) (assumed to be 3 ^oC)

Thus Q_p = (72.6MW x 1000) x 1.2 / 3.925 / 3

= 7,400 L/s (rounded to nearest hundred, and where 1 kg/s ≈ 1 L/s)

8.6.7.9 This increased spent cooling load is added to the existing loads from HKIA as well as the planned NCD project in order to assess the cumulative impacts with implementation of the third runway project. Table 8.45 summarises the discharge parameters for the ‘with project’ scenario.

Table 8.45: Summary of Spent Cooling Discharge Parameters for ‘with Project’ scenario

Design Parameters	SWPH-1	SWPH-7	NCD* (Concurrent Project)
Peak Flow	7070 L/s	7400 L/s	5368 L/s
Temperature of spent cooling water discharge^#	5 ^oC above ambient	5 ^oC above ambient	5 ^oC above ambient
Assumed ambient water temperature	25 ^oC (dry season) 30 ^oC (wet season)	25 ^oC (dry season) 30 ^oC (wet season)	25 ^oC (dry season) 30 ^oC (wet season)
Discharge point	Existing stormwater outfall No.7	New stormwater outfall No.14	Existing stormwater outfall No.8

* Based on communications with the project proponent, however, details of the discharges and discharge point are subject to further detailed design and may change.

^# A higher temperature difference is assumed for modelling worst case

8.6.7.10 For the expanded SWPH-1 and the proposed NCD, the diurnal loading pattern is assumed to be the same as for the ‘without project’ scenario. The modelled discharge rates are presented in Table 8.46.

Table 8.46: Diurnal Pattern for the Proposed T2 Expansion (SWPH-1)

Time	Percentage of peak loading	Model Value (L/s)
0000 to 0200	75%	5,303
0200 to 0300	50%	3,535
0500 to 0600	70%	4,949
0600 to 0000	100%	7,070

8.6.7.11 For SWPH-7, the diurnal loading pattern is derived from the infrastructure scheme design consultant. Table 8.47 presents the diurnal loading patterns and discharge rates adopted for the new SWPH-7.

Table 8.47: Diurnal Pattern for the Proposed Third Runway Concourse (SWPH-7)

Wet			Dry
Time	Percentage of peak loading	Model Value (L/s)	Time	Percentage of peak loading	Model Value (L/s)
0000 to 0200	75%	5,551	0000 to 0100	75%	5,353
0200 to 0500	60%	4,441	0200 to 0400	60%	4,283
0500 to 0900	90%	6,661	0500 to 0800	90%	6,424
0900 to 2100	100%	7,401	0900 to 2000	100%	7,138
2100 to 0000	85%	6,291	2100 to 2300	85%	6,067

8.6.7.12 For the NCD development, the same diurnal loading pattern and discharge rate (as presented in Table 8.43) is applied to the ‘with project’ scenario.

8.6.8 Residual Chlorine and Biocide

8.6.8.1 The Delft3D-PART model will be used to model the residual chlorine due to the spent cooling water discharges. Based on the limits set under the existing WPCO license for the spent cooling water discharge from HKIA, the maximum threshold of 0.5 mg/L for total residual chlorine (which represents the worst case) will be used as the discharge value for modelling the worst case spent cooling water discharge for both wet and dry season. With reference to the XRL EIA report (AEIAR-143/2009), the T90 factor (time to decay by 90 %) of 8289 seconds was adopted for use in this study as this value is the most conservative value amongst the previous EIA studies.

8.6.8.2 The residual chlorine is assumed to be discharging continuously for a complete spring neap cycle (15 days) at all spent cooling water discharge outfalls. The model parameters adopted are presented in Appendix 8.6. Due to the high decay rate of chlorine in marine waters, the ambient chlorine level is assumed to be negligible. As no background chlorine would be included in the water quality model, only the elevation of residual chlorine would be evaluated.

8.6.8.3 Similarly, the PART model will also be used to model the residual biocide from the spent cooling water discharges. Based on the existing WPCO license for the spent cooling water discharge from HKIA, a maximum dosage of 6 mg/L of biocide (measured as ‘amine’) is permitted for one hour per week at the intake point, with a maximum resultant residual discharge of 2 mg/L amine. For modelling purpose, the biocide is initially assumed to act as an inert, conservative tracer discharging 2 mg/L. A pre-run of 24 hour continuous discharge is used to determine the worst case tidal period for the actual 1 hour per week discharge at each spent cooling discharge outfall, such that the worst case ‘plume’ from the 1 hour per week discharge can be captured within a complete spring neap cycle. The model parameters adopted is presented in Appendix 8.6.

8.6.9 Operation Phase Water Quality Model

8.6.9.1 To simulate a complete year in operation phase, the water quality model was run for an entire year (with time varying loads) using the dry and wet season hydrodynamics for the dry and wet season periods and a combined (interpolated) hydrodynamics using the dry and wet season hydrodynamics for the intermediate seasons.

8.6.9.2 The impact on tidal flow, water dispersion and water quality during operation phase with and without the project was simulated using the Delft3D-WAQ model using the hydrodynamic result files from Delft3D-FLOW model. The pollution loading inventory provided the overall effluent loading conditions that are representative of the model year when all existing and planned projects are operational, i.e. 2026. Details of the pollution loading inventory is described in Appendix 8.7.

8.6.9.3 Data from the pollution loading inventory was input to the WAQ model to simulate the following water quality parameters:

¡ Water temperature (in ^oC);

¡ Salinity (in ppt);

¡ DO (mg/L);

¡ BOD (mg/L);

¡ SS (mg/L);

¡ Total Inorganic Nitrogen (mg/L);

¡ Ammonia (mg/L);

¡ E. coli (count per 100ml), and

¡ Sedimentation.

8.6.10 Impact Assessment and Presentation of Results

Construction Phase

8.6.10.1 To assess whether the WQO criteria are exceeded during construction phase, the maximum SS elevations predicted at all WSRs were tabulated and compared against the allowable SS elevations as presented in Table 8.22 to determine if any exceedances arise. These results are presented in Section 8.7.1. The residual impacts (if any) are quantified at representative WSRs and evaluated against the relevant standards and guidelines. Representative simulation results from the sediment plume model for the key tidal conditions (spring high and low water and neap high and low water) in wet and dry season are also presented as contour plans in Appendix 8.8, 8.10 and 8.11. The tidal times for contour presentation were selected based on more worst case sediment plume spread occurring at around the time of each key tidal condition.

8.6.10.2 For potential water quality impact due to pore water release during DCM ground improvement, similar tabulated results and contour plans from the dilution model are presented in Section 8.7.1 and Appendix 8.12.

8.6.10.3 For potential water quality impacts associated with sediment release due to water jetting and excavation of marine sediments at the field joint area for the diversion of the 11 kV submarine cable, the maximum SS elevation predicted at all WSRs was used to calculate the nutrient and contaminant concentrations. Results are presented in table format in Section 8.7.1. As the sediment plumes associated with water jetting and excavation at the field joint area were modelled as part of the worst case scenario A, the plume dispersion associated with these activities can be referred from the contour plans for Year 2016 in Appendix 8.8, 8.10 and 8.11.

Operation Phase

8.6.10.4 To assess whether the WQO criteria are exceeded in the thermal plume model, the maximum temperature difference between the with and without project scenarios, and maximum elevation in residual chlorine / biocide concentrations at nearby WSRs were tabulated and compared against relevant water quality standards and criteria to determine if any exceedances arise. These results are presented in Section 8.7.2. Simulation results from the hydrodynamic and water quality modelling are presented as contour plans and time-history plots (the latter plots are produced for only those WSRs identified with exceedances of relevant criteria) in Appendix 8.14 to 8.16. As the thermal plume model is run on a 15 day spring neap cycle, the tidal times for contour presentation were selected based on more worst case thermal plume spread occurring at around the time of each key tidal (spring high and low water and neap high and low water) condition.

8.6.10.5 For the annual water quality model, the monthly average concentrations of the key water quality parameters at all WSRs were tabulated and compared against relevant water quality standards and criteria to determine if any exceedances arise in Section 8.7.2. Simulation results from the water quality modelling are presented as contour plans and time-history plots (the latter plots are produced for only those WSRs identified with exceedances of relevant criteria) in Appendix 8.15. The contribution of the project to water quality within the study area is determined by comparing the ‘with’ and ‘without project’ scenario runs to identify the difference in water quality. The residual impacts (if any) are quantified at representative WSRs and evaluated against the relevant standards and guidelines.

8.7 Evaluation and Assessment of Water Quality Impacts

8.7.1 Construction Phase

Release of Suspended Solids due to Marine Construction Activities

Year 2016 Scenario - Unmitigated

8.7.1.1 The Year 2016 scenario is based on a period of construction that is tentatively programmed to occur during the first quarter (between January and March) and represents the dominant construction activities of sand blanket laying, ground improvement, water jetting and excavation for submarine cable diversion, prior to commencement of seawall construction for land formation (i.e. when local flow conditions remain unaltered and sediment plume spreading is unrestricted).

8.7.1.2 Predicted elevations in SS were plotted as sediment plume contours representing the high and low water levels for both spring and neap tides in both dry and wet seasons. These plots are show in Appendix 8.8. The maximum elevation in SS observed at each WSR and observation point over the entire modelling timeframe was extracted and compared against the relevant SS exceedance criteria shown in Table 8.22. The results are summarised in Table 8.48.

8.7.1.3 Based on the results, sediment plumes arising from the project appear to occur mainly near seabed level. Dry season plots show the sediment plumes to be vertically distributed, but with limited horizontal dispersion, while wet season plots show limited vertical dispersion but more significant horizontal dispersion particularly during ebb tides. Exceedance of the principal criteria (depth-averaged) occurs at WSR C7a and C8 during wet season only. C7a is the cooling water intake at HKIA (North), while C8 represents the future cooling water intake for HKBCF. Both of these WSRs are located adjacent to the construction activities on the eastern side, and are susceptible to adverse water quality impacts during ebb tides. Mitigation measures are recommended at these locations. SS levels are also predicted to be above the reference criteria at WSRs C20, CR3, E12 and F2, however there is no exceedance of the principal depth-averaged criteria, and the frequency of exceedance is very small (0.1 % to 0.3 % of the time only). At source mitigation measures to reduce SS levels at C7a and C8 would similarly reduce SS levels at these WSRs accordingly.

8.7.1.4 Aside from the WSRs, notable elevations in SS levels also occur at EPD’s existing monitoring station (observation point M9), however, this is located immediately adjacent to the construction activities, hence high SS levels at this location would be expected. Relatively higher SS levels are also detected near the seabed during wet season at observation points M4d and M4e, which represents the southern boundary of the Sha Chau and Lung Kwu Chau Marine Park. However, other monitoring locations within the Marine Park (e.g. M4c, CR2 and E5) do not show particularly high elevations or exceedances in SS criteria, which suggests that the relatively higher SS levels at M4d and M4e are limited to a small area at the southern boundary which is the closest to the construction activities for the project. Given that the higher SS levels occur near seabed level and other monitoring stations in Sha Chau and Lung Kwu Chau Marine Park are not affected, it can be deduced that the marine ecological sensitive receivers at the Marine Park would not be adversely affected by the localised elevations predicted at these locations.

8.7.1.5 In summary, the findings show only a few locations with exceedance in SS criteria in Year 2016, and mitigation measures are recommended to reduce the potential impacts at these WSRs.

Year 2017 Scenario - Unmitigated

8.7.1.6 The Year 2017 scenario is based on a period of construction that is tentatively programmed to occur during the first quarter (between January and March) and represents the period with the overall highest sediment loss due to the highest number of plant undertaking ground improvement (via DCM) and marine filling activities. This scenario takes into account the partial seawall completion along mainly the western edge, which consequently impedes local flow conditions, thereby altering the sediment plume dispersion effect.

8.7.1.7 Predicted elevations in SS were plotted as sediment plume contours representing the high and low water levels for both spring and neap tides in both dry and wet seasons. These plots are show in Appendix 8.8. The maximum elevation in SS observed at each WSR and observation point over the entire modelling timeframe was extracted and compared against the relevant SS exceedance criteria shown in Table 8.22. The results are summarised in Table 8.49.

8.7.1.8 As shown on the contour plots, the partially completed seawalls are generally very effective in containing and reducing the spread of the sediment plumes, however, ‘leakage’ of sediment plumes occur in the gaps between seawalls, and this is particularly evident during ebb tides whereby sediment plumes generated from construction activities near the southeastern side of the land formation appear to drift further afield. Along the southwestern side, sediment plumes may also form outside the land formation area due to the seawall gap, and also towards the north during flood tides.

8.7.1.9 Under this scenario, WSRs C7a and C8 will experience exceedance of the SS criteria. Mitigation measures are recommended to reduce adverse impacts to these WSRs. No exceedances are predicted at other WSRs, except for a minor exceedance of the reference SS criteria at CR3, which occurs for only 0.1% of the time and is unlikely to substantially affect this WSR. As WSR CR3 is located downstream of WSRs C7a and C8 during ebb tides, it is likely that ‘at source’ mitigation measures applied for the purpose of mitigating exceedances at C7a and C8 would similarly reduce SS levels predicted at CR3.

8.7.1.10 Similar to the Year 2016 scenario, notable elevations in SS levels are also predicted along the southern boundary of the Sha Chau and Lung Kwu Chau Marine Park (M4c and M4d) in the Year 2017 scenario. However, other monitoring locations within the Marine Park (e.g. M4e, CR2 and E5) do not show particularly high elevations or exceedances in SS criteria, hence the predicted maximum SS levels at M4c and M4d are very localised elevations that do not affect other parts of the Sha Chau and Lung Kwu Chau Marine Park, and it is unlikely that marine ecological sensitive receivers at the Marine Park would be adversely affected by such localised elevations.

Table 8.48: Predicted Maximum SS (mg/L) Elevations at WSRs and Observation Points for the Scenario Year 2016 (Unmitigated)

WSR / Obs Points	Associated EPD Stations	Maximum SS (mg/L) Elevation								Exceedance Above SS Criteria (mg/L)								Frequency of Exceedance (% Time)
		Wet Season				Dry Season				Wet Season				Dry Season				Wet Season				Dry Season
		S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA
B1	NM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B2	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B3	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B4	WM4	0.00	1.67	0.00	0.44	0.93	0.00	0.00	0.15	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B5	WM4	0.00	0.00	1.69	0.34	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B6	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B7	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B8	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B9	WM4	0.59	0.69	0.40	0.17	0.52	0.68	0.00	0.07	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B10	WM4	0.00	0.78	0.60	0.13	0.55	0.00	0.00	0.07	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B11	WM4	1.99	0.97	0.00	0.20	0.00	0.90	0.00	0.35	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B12	WM4	0.00	2.11	0.00	0.21	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B13	WM4	0.00	0.00	0.00	0.32	0.00	0.00	0.00	0.15	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C1	DM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C2	NM5	0.00	0.61	0.44	0.06	0.00	0.00	0.00	0.06	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C3	NM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C4	NM1	0.00	1.19	1.19	0.36	1.18	1.07	0.00	0.29	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C7a	NM3	18.26	38.63	20.81	24.61	7.75	6.26	2.47	3.77	15.61	34.13	13.13	20.26	4.15	1.46	Nil	Nil	2.5%	5.0%	1.7%	4.9%	4.3%	0.3%	0.0%	0.0%
C7b	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C8	NM3	3.99	19.56	19.97	13.65	5.09	7.12	3.16	2.18	1.34	15.06	12.29	9.29	1.49	2.32	Nil	Nil	0.2%	1.7%	1.5%	1.1%	0.3%	0.1%	0.0%	0.0%
C9	DM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C10	NM2	0.00	1.19	0.98	0.21	0.00	0.00	0.00	0.06	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C11	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C12	WM1	0.00	0.00	0.00	0.04	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C13	WM1	0.00	0.27	0.00	0.03	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C14	WM1	0.00	0.44	0.39	0.08	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C15	NM3	0.00	0.48	0.39	0.07	0.44	0.39	0.00	0.04	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C20	WM3	0.62	0.32	0.31	0.19	0.00	0.00	0.00	0.00	Nil	0.32	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.3%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR2	NM6	0.00	1.75	2.48	1.57	2.79	3.02	1.81	1.57	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR3	NM3	0.00	0.92	9.09	1.57	2.88	3.66	1.05	0.56	Nil	Nil	1.41	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.1%	0.0%	0.0%	0.0%	0.0%	0.0%
CR4	WM1	0.28	0.14	0.00	0.07	0.00	0.00	0.00	0.01	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR5	WM2	0.00	0.59	0.57	0.20	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E1	DM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	N/A	Nil	Nil	Nil	N/A	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E2	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E3	NM8	0.00	0.00	0.00	0.01	0.31	0.32	0.00	0.13	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E4	NM2	0.00	0.78	3.50	0.35	1.68	0.87	0.89	0.35	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E5	NM5	0.00	1.90	1.67	0.64	1.34	1.95	0.68	0.85	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E6	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E7	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E8	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E9	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E10	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E11	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E12	NM2	3.99	2.49	1.89	2.16	1.61	1.03	0.99	0.36	1.65	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.1%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F1	WM4	0.50	0.85	1.14	0.36	0.52	0.80	0.48	0.16	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F2	NM5	0.81	9.12	2.68	2.22	1.92	1.93	2.03	1.61	Nil	4.32	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.1%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F3	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
M1	NM3	0.00	0.37	0.56	0.27	0.38	0.19	0.19	0.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M2	NM3	0.00	0.32	0.36	0.04	0.00	0.00	0.35	0.04	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M3	NM6	0.00	1.93	1.88	1.38	3.83	3.15	2.48	2.28	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4a	NM5	0.00	0.29	0.00	0.05	0.30	0.00	0.54	0.11	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4b	NM5	0.00	0.20	0.40	0.08	0.20	0.39	0.19	0.12	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4c	NM6	0.00	4.40	10.88	2.52	3.01	2.43	1.96	1.35	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4d	NM6	0.12	15.97	39.48	9.60	4.55	4.27	2.74	3.14	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4e	NM6	0.54	5.68	27.53	5.00	5.46	7.60	4.19	4.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M5	NM1	0.26	1.48	0.81	0.64	0.27	0.27	0.14	0.11	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M6	NM2	0.30	3.90	0.64	1.27	0.33	0.33	0.34	0.12	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M7	NM3	0.00	0.77	0.74	0.30	0.27	0.52	0.27	0.08	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M8	NM5	0.00	0.20	0.38	0.04	0.38	0.77	0.20	0.13	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M9	NM6	0.00	5.03	69.60	11.87	20.98	32.24	22.45	13.90	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M10	NM8	0.00	0.18	4.08	0.75	2.26	1.15	1.14	1.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M11	WM1	0.11	0.11	0.10	0.02	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M12	WM2	0.24	0.47	0.24	0.11	0.23	0.00	0.00	0.02	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M13	WM3	0.24	0.24	0.23	0.07	0.23	0.23	0.00	0.02	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M14	WM4	0.44	0.60	0.30	0.19	0.30	0.15	0.15	0.06	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M15	DM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M16	DM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M17	DM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M18	DM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M19	DM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
T1	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
T2	WM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

N/A = not applicable (applies to observation points and WSD seawater intakes – bottom layer)

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

Table 8.49: Predicted Maximum SS (mg/L) Elevations at WSRs and Observation Points for the Scenario Year 2017 (Unmitigated)

WSR / Obs Points	Associated EPD Stations	Maximum SS (mg/L) Elevation								Exceedance Above SS Criteria (mg/L)								Frequency of Exceedance (% Time)
		Wet Season				Dry Season				Wet Season				Dry Season				Wet Season				Dry Season
		S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA
B1	NM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B2	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B3	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B4	WM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B5	WM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B6	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B7	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B8	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B9	WM4	0.00	0.00	0.00	0.22	1.46	2.27	0.00	0.41	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B10	WM4	0.00	0.00	0.00	0.23	0.00	0.00	0.00	0.23	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B11	WM4	0.00	0.00	0.00	0.00	2.83	0.00	0.00	0.28	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B12	WM4	0.00	0.00	0.00	0.49	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B13	WM4	0.00	0.00	0.00	0.42	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C1	DM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C2	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C3	NM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C4	NM1	0.00	0.00	0.00	0.37	4.54	2.84	0.00	0.46	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C7a	NM3	3.28	22.22	531.50	73.17	92.09	84.04	44.50	60.69	0.63	17.72	523.82	68.82	88.49	79.24	36.10	55.02	0.1%	1.7%	15.1%	4.6%	18.2%	12.6%	7.8%	10.9%
C7b	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C8	NM3	2.39	11.21	15.86	9.39	24.58	19.90	13.95	14.90	Nil	6.71	8.18	5.04	20.98	15.10	5.55	9.22	0.0%	0.8%	0.8%	0.5%	5.0%	2.5%	0.6%	2.5%
C9	DM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C10	NM2	0.00	0.00	0.00	0.26	0.00	0.00	0.00	0.32	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C11	NM6	0.00	0.00	2.77	0.55	3.70	0.00	0.00	0.37	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C12	WM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C13	WM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C14	WM1	0.00	0.00	0.00	0.00	0.00	1.52	0.00	0.15	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C15	NM3	0.00	0.00	0.00	0.18	0.00	0.00	0.00	0.09	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C20	WM3	0.00	0.00	0.76	0.16	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR2	NM6	0.00	0.00	4.22	0.63	0.00	2.18	0.00	0.60	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR3	NM3	0.00	4.56	4.31	0.74	4.01	2.41	2.47	0.51	Nil	0.06	Nil	Nil	0.41	Nil	Nil	Nil	0.0%	0.1%	0.0%	0.0%	0.1%	0.0%	0.0%	0.0%
CR4	WM1	0.47	0.00	0.49	0.05	0.00	0.00	0.48	0.05	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR5	WM2	0.00	0.00	1.04	0.11	1.13	0.00	0.00	0.11	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E1	DM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	N/A	Nil	Nil	Nil	N/A	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E2	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E3	NM8	0.00	0.44	0.00	0.04	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E4	NM2	0.00	0.00	2.94	0.29	2.52	3.00	2.38	0.30	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E5	NM5	0.00	0.00	0.00	0.00	2.43	2.39	1.68	0.25	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E6	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E7	NM6	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E8	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E9	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E10	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E11	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E12	NM2	0.00	1.67	2.00	0.36	2.06	2.28	1.87	0.78	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F1	WM4	0.00	1.73	0.00	0.18	1.74	1.90	1.77	0.33	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F2	NM5	0.00	0.00	2.98	0.45	3.06	2.03	1.46	2.18	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F3	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
M1	NM3	0.00	0.68	0.69	0.14	0.68	0.68	0.68	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M2	NM3	0.00	0.00	1.21	0.12	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M3	NM6	0.00	0.84	0.00	0.09	0.00	0.00	0.00	0.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4a	NM5	0.00	0.00	2.12	0.21	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4b	NM5	0.00	0.76	0.00	0.08	0.00	0.00	0.49	0.14	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4c	NM6	0.00	2.36	28.52	11.58	4.55	9.29	4.71	3.46	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4d	NM6	0.00	0.00	1.55	0.16	12.31	26.85	13.36	17.37	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4e	NM6	0.00	0.00	9.55	1.22	2.56	2.49	2.38	0.51	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M5	NM1	0.34	1.00	0.50	0.22	0.51	0.98	0.49	0.27	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M6	NM2	0.00	1.20	1.13	0.12	1.19	1.15	0.84	0.12	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M7	NM3	0.00	0.00	0.93	0.09	0.00	0.00	0.00	0.10	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M8	NM5	0.00	0.00	0.00	0.08	0.00	0.49	0.00	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M9	NM6	0.00	2.06	6.06	0.82	2.07	0.00	0.00	0.21	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M10	NM8	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M11	WM1	0.39	0.00	0.00	0.04	0.00	0.00	0.00	0.04	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M12	WM2	0.63	0.85	0.00	0.09	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M13	WM3	0.61	0.00	0.80	0.09	0.83	0.00	0.58	0.14	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M14	WM4	0.55	0.54	0.53	0.11	0.54	0.55	0.52	0.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M15	DM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M16	DM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M17	DM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M18	DM4	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M19	DM5	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
T1	NM2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
T2	WM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

N/A = not applicable (applies to observation points and WSD seawater intakes – bottom layer)

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

Table 8.52: Predicted Maximum SS (mg/L) Elevations at WSRs and Observation Points for the Scenario Year 2016 (Mitigated)

WSR / Obs Points	Associated EPD Stations	Maximum SS (mg/L) Elevation								Exceedance Above SS Criteria (mg/L)								Frequency of Exceedance (% Time)
		Wet Season				Dry Season				Wet Season				Dry Season				Wet Season				Dry Season
		S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA
B4	WM4	0.00	1.67	0.00	0.17	0.93	0.00	0.00	0.15	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B5	WM4	0.00	0.00	0.00	0.20	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B9	WM4	0.59	0.69	0.36	0.13	0.00	0.00	0.00	0.07	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B10	WM4	0.00	0.78	0.60	0.13	0.55	0.00	0.00	0.07	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B11	WM4	1.99	0.00	0.00	0.20	0.00	0.00	0.00	0.35	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B12	WM4	0.00	2.11	0.00	0.21	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
B13	WM4	0.00	0.00	0.00	0.13	0.00	0.00	0.00	0.15	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C2	NM5	0.00	0.00	0.00	0.04	0.00	0.00	0.00	0.04	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C4	NM1	0.00	1.19	1.19	0.24	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C7a	NM3	7.69	18.35	9.44	12.15	4.17	3.24	2.38	1.46	5.03	13.85	1.76	7.80	0.57	Nil	Nil	Nil	1.6%	2.9%	0.2%	2.4%	0.1%	0.0%	0.0%	0.0%
C8	NM3	2.76	8.06	9.83	5.59	2.16	2.53	2.28	1.08	0.10	3.56	2.15	1.23	Nil	Nil	Nil	Nil	0.1%	0.7%	0.3%	0.6%	0.0%	0.0%	0.0%	0.0%
C10	NM2	0.00	0.92	0.98	0.21	0.00	0.00	0.00	0.06	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C12	WM1	0.00	0.00	0.00	0.04	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C13	WM1	0.00	0.27	0.00	0.03	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C14	WM1	0.00	0.42	0.39	0.08	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C15	NM3	0.00	0.00	0.39	0.05	0.38	0.39	0.00	0.04	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C20	WM3	0.62	0.27	0.31	0.12	0.00	0.00	0.00	0.00	Nil	0.27	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.1%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR2	NM6	0.00	0.74	2.48	1.03	2.42	1.88	1.18	1.07	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR3	NM3	0.00	0.92	3.92	0.99	2.88	3.66	1.05	0.56	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR4	WM1	0.28	0.14	0.00	0.07	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR5	WM2	0.00	0.31	0.30	0.14	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E3	NM8	0.00	0.00	0.00	0.01	0.31	0.00	0.00	0.09	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E4	NM2	0.00	0.78	1.75	0.17	1.68	0.87	0.89	0.35	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E5	NM5	0.00	1.90	0.83	0.60	1.34	1.95	0.66	0.57	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E12	NM2	0.99	2.45	1.54	1.63	1.04	0.52	0.99	0.27	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F1	WM4	0.48	0.66	1.14	0.31	0.51	0.53	0.48	0.10	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F2	NM5	0.00	4.91	2.40	1.73	1.92	1.66	1.91	1.29	Nil	0.11	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.1%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
M1	NM3	0.00	0.19	0.55	0.20	0.38	0.19	0.19	0.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M2	NM3	0.00	0.32	0.36	0.04	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M3	NM6	0.00	1.93	1.88	0.66	3.00	2.55	1.91	1.93	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4a	NM5	0.00	0.29	0.00	0.03	0.15	0.00	0.54	0.08	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4b	NM5	0.00	0.20	0.21	0.06	0.20	0.39	0.00	0.10	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4c	NM6	0.00	4.40	10.88	2.39	3.01	1.98	1.96	1.29	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4d	NM6	0.00	14.69	39.48	9.19	2.92	4.27	2.47	2.76	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4e	NM6	0.37	5.33	26.12	5.00	4.01	7.05	3.20	3.04	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M5	NM1	0.26	1.48	0.81	0.56	0.14	0.27	0.14	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M6	NM2	0.30	3.90	0.64	1.07	0.33	0.33	0.34	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M7	NM3	0.00	0.77	0.57	0.30	0.26	0.52	0.00	0.08	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M8	NM5	0.00	0.00	0.38	0.04	0.38	0.77	0.20	0.10	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M9	NM6	0.00	5.03	69.60	11.46	15.84	29.14	21.49	12.69	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M10	NM8	0.00	0.18	4.08	0.58	1.75	1.15	0.59	0.53	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M11	WM1	0.11	0.11	0.10	0.01	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M12	WM2	0.23	0.46	0.23	0.09	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M13	WM3	0.24	0.24	0.23	0.07	0.23	0.22	0.00	0.02	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M14	WM4	0.44	0.60	0.15	0.18	0.30	0.15	0.15	0.03	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

N/A = not applicable (applies to observation points and WSD seawater intakes – bottom layer)

Only those WSRs / Observation Points with elevated SS levels are shown.

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

Table 8.54: Predicted Maximum SS (mg/L) Elevations at WSRs and Observation Points for the Scenario Year 2017 (Mitigated)

WSR / Obs Points	Associated EPD Stations	Maximum SS (mg/L) Elevation								Exceedance Above SS Criteria (mg/L)								Frequency of Exceedance (% Time)
		Wet Season				Dry Season				Wet Season				Dry Season				Wet Season				Dry Season
		S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA	S	M	B	DA
B9	WM4	0.00	0.00	0.00	0.14	0.00	0.00	0.00	0.10	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C4	NM1	0.00	0.00	0.00	0.00	3.30	2.84	0.00	0.33	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C7a	NM3	0.00	11.32	134.05	15.37	37.93	28.28	23.59	22.58	Nil	6.82	126.37	11.02	34.33	23.48	15.19	16.91	0.0%	0.1%	3.7%	1.5%	8.5%	6.5%	1.6%	6.1%
C8	NM3	0.00	1.81	4.61	0.80	8.93	7.64	6.02	5.36	Nil	Nil	Nil	Nil	5.33	2.84	Nil	Nil	0.0%	0.0%	0.0%	0.0%	1.0%	0.4%	0.0%	0.0%
C10	NM2	0.00	0.00	0.00	0.26	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C15	NM3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.09	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
C20	WM3	0.00	0.00	0.76	0.16	0.00	0.00	0.00	0.00	Nil	Nil	N/A	Nil	Nil	Nil	N/A	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR2	NM6	0.00	0.00	1.52	0.30	0.00	1.61	0.00	0.32	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR3	NM3	0.00	0.00	2.12	0.66	2.60	2.41	2.47	0.51	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR4	WM1	0.36	0.00	0.00	0.04	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
CR5	WM2	0.00	0.00	0.00	0.08	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E3	NM8	0.00	0.44	0.00	0.04	0.00	0.00	0.00	0.00	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E4	NM2	0.00	0.00	2.46	0.25	0.00	0.00	0.00	0.28	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E5	NM5	0.00	0.00	0.00	0.00	0.00	1.66	1.68	0.18	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
E12	NM2	0.00	0.00	0.00	0.14	1.51	1.63	1.42	0.30	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F1	WM4	0.00	1.44	0.00	0.14	0.00	0.71	0.59	0.19	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
F2	NM5	0.00	0.00	0.00	0.00	3.06	2.03	1.12	1.52	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%
M1	NM3	0.00	0.00	0.48	0.05	0.00	0.00	0.00	0.05	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M3	NM6	0.00	0.84	0.00	0.09	0.00	0.00	0.00	0.09	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4b	NM5	0.00	0.00	0.00	0.00	0.00	0.00	0.49	0.05	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4c	NM6	0.00	1.68	16.91	4.79	1.68	1.69	1.72	0.83	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4d	NM6	0.00	0.00	1.09	0.11	12.31	26.85	13.36	14.32	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M4e	NM6	0.00	0.00	3.48	0.52	1.62	1.67	1.68	0.36	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M5	NM1	0.34	0.36	0.36	0.07	0.35	0.36	0.35	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M6	NM2	0.00	0.00	0.00	0.08	0.73	0.80	0.84	0.08	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M7	NM3	0.00	0.00	0.69	0.07	0.00	0.00	0.00	0.07	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M8	NM5	0.00	0.00	0.00	0.00	0.00	0.49	0.00	0.05	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M9	NM6	0.00	0.00	2.76	0.29	1.49	0.00	0.00	0.15	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M11	WM1	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.03	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M12	WM2	0.63	0.61	0.00	0.06	0.00	0.00	0.00	0.00	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M13	WM3	0.61	0.00	0.61	0.06	0.58	0.00	0.58	0.06	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
M14	WM4	0.39	0.40	0.00	0.08	0.37	0.38	0.38	0.08	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

N/A = not applicable (applies to observation points and WSD seawater intakes – bottom layer)

Only those WSRs / Observation Points with elevated SS levels are shown.

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

8.7.1.35 Aside from C7a, which was identified to be affected entirely by construction of the third runway project, exceedance of the principal criteria is predicted at WSRs representing the WSD seawater intake at Tsing Yi (C20), hard corals at The Brothers Islands (CR3), and ecologically sensitive areas at Sham Shui Kok (E12). A comparison was made between the SS elevations under the ‘project only’ and ‘concurrent project’ scenarios, and the percentage contribution due to the third runway project is summarised in Table 8.60.

Table 8.60: Third Runway project contribution to total SS elevations at WSRs showing cumulative exceedance of the principal SS criteria – Year 2017 Mitigated

WSR		Wet Season	Dry Season
C7a	Cooling water intake at HKIA north	100 %	100 %
C20	WSD seawater intake at Tsing Yi	10 %	Nil
CR3	Hard corals at The Brothers Islands	12 %	N/A
E12	Sham Shui Kok	2 %	N/A

Note:

Nil values = no detected SS elevations due to ‘project only’ scenario

N/A values = no cumulative exceedance of principal SS criteria in ‘cumulative’ scenario

8.7.1.36 As with the Year 2016 scenario, the results for Year 2017 also show that high elevations in SS predicted at C7a are due mainly to the third runway project, while the high SS predicted at C20, CR3 and E12 are primarily due to the modelled SS release from concurrent projects.

8.7.1.37 For C7a, the SS elevations are entirely due to the third runway project, and with the additional mitigation measures in the form of double silt curtain and silt screens in place, the SS elevations would be reduced to below the principal criteria, and these results would not be substantially changed due to cumulative SS release from concurrent projects (see Table 8.61).

Table 8.61: Summary of Predicted Maximum SS (mg/L) Elevations at WSR C7a with Application of Additional Mitigation Measures for the Scenario Year 2017 with Concurrent Projects

	Wet Season				Dry Season
WSR C7a	S	M	B	DA	S	M	B	DA
Criteria	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
With Additional Mitigation	0.00	1.81	21.45	2.46	6.07	4.52	3.77	3.61
Residual Exceedance	Nil	Nil	13.75	Nil	2.47	Nil	Nil	Nil

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

8.7.1.38 At C20, the cumulative exceedance is similar to the Year 2016 scenario, and is primarily due to the KTCB concurrent project, which is located in close proximity to this WSR. As this WSR already showed exceedances due to the KTCB project (as stated in the approved KTCB EIA report), silt screens have been recommended by the KTCB project and water quality monitoring will be in place to address any potential water quality impacts as part of their environmental monitoring and audit requirements.

8.7.1.39 Exceedance at E12 is primarily attributable to the assumptions adopted for the LLP project. As there is currently no implementation programme for the LLP project, this project may not be constructed at the same time as the third runway project. Nevertheless, given that the future project at this site will also require an EIA, it is likely that the construction programme and assumptions for sediment loss would be updated to account for, and thus minimise, the potential water quality impacts associated with this concurrent project.

8.7.1.40 At CR3, exceedances are primarily due to the very conservative modelling assumptions that were adopted for the disposal / capping operations at the CMPs at East Sha Chau and South of the Brothers (refer to Appendix 8.5 for the values adopted for MDF project).

8.7.1.41 Based on communications with the project proponent in October and December 2013, the forecast for average annual disposal in Year 2017 is 0.64 million m³, while capping is anticipated to be completed subject to the progress of the disposal activities, which is dependent on the disposal demand from various marine works projects in Hong Kong. Nevertheless, the forecasts are lower than the forecasts for Year 2016 and substantially lower than the modelled worst case (assuming a daily rate of 26,700 m³/day occurring continuously for 15 days would mean a total disposal of 0.4 million m³ – over half of the total annual disposal forecast for Year 2017 completed in just 15 days. Or conversely, for a disposal forecast of 0.64 million m³ in Year 2017, the entire year’s productivity would be completed in just 24 days). The modelled worst case cumulative impact is thus very unlikely to be representative of the average daily disposal rates

8.7.1.42 Taking the same approach as that which was adopted for Year 2016 scenario, a sensitivity test was undertaken using the historic rates of 5,850 m³/day and 12,350 m³/day for disposal and capping respectively. The modelled result for CR3 using this reduced sediment loss rate from the MDF project is shown in Table 8.62.

Table 8.62: Predicted Maximum SS (mg/L) Elevations at WSR CR3 for the Scenario Year 2017 (mitigated) with Concurrent Projects – Sensitivity Test

	Wet Season				Dry Season
WSR CR3	S	M	B	DA	S	M	B	DA
Criteria	2.7	4.5	7.7	4.4	3.6	4.8	8.4	5.7
Original Cumulative Result	1.35	16.22	3.60	5.62	4.96	5.08	2.47	1.81
Sensitivity Test Result	0.00	10.66	2.12	2.11	2.60	2.41	2.47	0.51
Residual Exceedance (Sensitivity Test)	Nil	6.16	Nil	Nil	Nil	Nil	Nil	Nil

Note: “S” Surface, “M” Middle, “B” Bottom, “DA” Depth Averaged.

Nil values = no exceedances of WQO / WQC

Note that the depth averaged criteria is the main criteria for compliance. Others are for reference only.

8.7.1.43 The results show that using the reduced production rates in the model, the SS elevations at CR3 would be significantly reduced and no cumulative exceedance of the principal criteria would arise. Based on this sensitivity test, it is reasonable to conclude that exceedance of the principal criteria at CR3 is due to the very conservative modelling assumptions only, and assuming that the future production rate of the MDF project is comparable to the historical production rates, adverse impacts to CR3 due to cumulative SS are unlikely to be significant.

8.7.1.44 For WSR B4, C8, C12, and E4, cumulative SS levels are predicted to be above the reference criteria at these locations, however there is no exceedance of the principal depth-averaged criteria. The reference criteria exceedances are also very infrequent (between 0.1 % and 1 % of the time only under the worst case model shown in Table 8.59). Thus adverse cumulative impacts are not anticipated.

Sedimentation – with Concurrent Projects

8.7.1.45 The maximum daily sediment deposition rate over the entire simulation period for the ‘concurrent project’ scenarios were extracted and is shown in Table 8.63. The findings show that the cumulative sediment deposition at all ecological sensitive receiver locations are well below the criteria of 200 g/m²/day specified for corals. Hence no cumulative impact due to sedimentation is anticipated.

Table 8.63: Summary of Sediment Deposition at WSRs and Observation Points Representing Ecological Sensitive Receivers with Concurrent Projects

WSR / Observation Point (representing ecological sensitive receivers)	Sediment Deposition Rate (g/m²/day)
	Year 2016 – Mitigated		Year 2017 – Mitigated
	Wet Season	Dry Season	Wet Season	Dry Season
CR2	1.80	10.76	2.17	1.85
CR3	16.19	10.86	8.58	11.94
CR4	1.50	3.00	1.50	3.75
CR5	3.74	1.50	4.40	1.40
E3	0.78	0.00	0.78	0.00
E4	14.27	31.03	11.29	33.59
E5	1.05	5.48	0.00	1.09
E9	0.00	0.00	1.57	0.78
E12	17.19	46.53	19.06	39.42
F1	4.48	5.98	4.50	5.23
F2	10.61	12.80	8.21	8.05
F3	0.00	0.00	1.57	0.78
M4a	4.48	1.00	2.24	0.75
M4b	23.89	11.20	25.38	11.20
M4c	9.87	10.43	19.54	4.38
M4d	135.01	30.26	1.09	63.60
M4e	33.00	45.70	2.17	1.85

Note: Only those locations where sediment deposition occurred in the model are shown.

Post-Year 2017 Construction Activities

8.7.1.46 By the end of Year 2017, there will be substantial completion of the seawall surrounding the new land formation, with only a short section of the northeastern seawall (<500 m gap) remaining to be constructed. This northeastern section is generally parallel to the dominant flood and ebb current directions, such that the remaining body of water behind the seawall gap would not be subject to strong flood / ebb currents passing through the seawall gap. In the absence of strong currents, the potential for release of SS to the surrounding marine environment from this seawall gap would be very limited. Hence while predominantly sand fill will be used for marine filling activities until the end of Year 2017, construction activities from Year 2018 onwards may adopt the use of sand or public fill with up to 25% fines content.

8.7.1.47 Based on the plant quantities shown in Appendix 8.4, a comparison was made between sediment loss in Year 2017 and post-Year 2017, and the associated water quality impact at WSRs (presented in Table 8.64). The worst affected WSR in Year 2017 (C7a) was adopted as a basis for direct comparison of SS results.

Table 8.64: Comparison between Year 2017 and Post-Year 2017 Activities and Potential Water Quality Impact

Comparison of Potential Water Quality Impact	Year 2017 (worst case)	Post-Year 2017
Potential Sediment Loss
No. plant undergoing marine filling activities	31	4
Sediment loss rate per marine plant	15.286 kg/s (based on 20 % fines content)	19.107 kg/s (based on 25 % fines content)
Total sediment loss rate (marine filling activities)	473.866 kg/s	76.428 kg/s
Total sediment loss rate (all marine activities)	520.811 kg/s	93.340 kg/s
Percentage of Year 2017 worst case	100 %	16 %
Mitigated SS Elevations at WSR C7a (based on model results assuming 61 % reductions due to application of double layer silt curtains at source)
Modelled result of maximum depth-average SS elevation	22.58 mg/L	-
Equivalent result of maximum depth-average SS elevation in Year 2018 (assuming no difference between Year 2017 and Year 2018 except for total sediment loss rate)	-	3.61 mg/L
Additional Mitigated SS Elevations at WSR C7a (calculated results assuming 84 % reductions due to additional double layer silt curtain and silt screens at receiver)
Calculated result of maximum depth-average SS elevation	3.61 mg/L	0.58 mg/L
Residual Exceedance	Nil	Nil

8.7.1.48 The comparison shows that the substantial reductions in total sediment loss rate associated with post-Year 2017 activities would enable similar reductions in SS elevations at C7a, such that there would be no residual impacts to C7a in post-Year 2017. It should be noted that the comparison presented in Table 8.64 does not take into account the much larger extent of completed seawall in post-Year 2017, which would further reduce tidal influences to the active works areas and enable better containment of sediment plumes. Thus it is unlikely that the additional ‘at receiver’ mitigation measures would be required in order to achieve compliance of the WQOs.

8.7.1.49 Given the findings of the comparison, it is anticipated that sand or public fill with up to 25 % fines content can be used for marine filling activities after Year 2017 without adversely affecting nearby WSRs. To ensure the fines content of the public fill sources are suitable, quality control tests will be carried out on selected samples taken from the source and/or from individual batches of public fill delivered to the site. The requirement for marine filling activities to be carried out behind an advance seawall of at least 200 m (i.e. marine filling activities behind the seawall gap would need to maintain a distance of at least 200 m from the entrance of the gap) will also remain in force until the seawall gap is reduced to <200 m. Silt curtains will be deployed to cover the seawall gap as an additional precautionary measure until such time as the seawall construction is completed and the gap is closed. However, the need for ‘at receiver’ mitigations in post-Year 2017 will be reviewed as part of environmental monitoring and audit requirements.

Water Quality Impacts Associated with Sediment Release

Oxygen Depletion

8.7.1.50 Dissolved oxygen (DO) depletion due to the release of sediment from the water jetting and excavation activities associated with the submarine cable diversion was calculated using the formula specified in Section 8.6.4. The maximum SS concentration is based on the Year 2016 model scenario in the absence of land formation activities (i.e. worst case scenario C only). A summary of the depth averaged and bottom layer DO results is shown in Table 8.65 and Table 8.66 respectively.

Table 8.65: Summary of Changes to Depth-averaged DO Levels due to Elevated SS Release

WSR / Obs Point	Associated EPD monitoring station	Max. SS Concentration (kg/m³)		DO Depletion (mg/L)		Baseline DO¹ – depth averaged (mg/L)		Depth averaged DO Level at WSR / Observation Point (mg/L)		DO Criteria (mg/L)
WSR / Obs Point	Associated EPD monitoring station	Wet	Dry	Wet	Dry	Wet	Dry	Wet	Dry
B1	NM3	6.70E-04	1.01E-03	1.49E-03	2.26E-03	5.3	6.8	5.3	6.8	>4
B2	NM5	2.65E-04	8.62E-04	5.92E-04	1.92E-03	5.3	6.8	5.3	6.8	>4
B3	NM2	8.58E-04	1.05E-03	1.91E-03	2.35E-03	5.8	6.6	5.8	6.6	>4
B4	WM4	1.55E-03	1.30E-03	3.46E-03	2.89E-03	5.2	6.3	5.2	6.3	>4
B5	WM4	7.94E-04	8.74E-04	1.77E-03	1.95E-03	5.2	6.3	5.2	6.3	>4
B6	NM2	7.67E-04	1.07E-03	1.71E-03	2.38E-03	5.8	6.6	5.8	6.6	>4
B7	NM5	6.21E-04	1.11E-03	1.39E-03	2.47E-03	5.3	6.8	5.3	6.8	>4
B8	NM5	6.21E-04	1.11E-03	1.39E-03	2.47E-03	5.3	6.8	5.3	6.8	>4
B9	WM4	3.76E-04	6.90E-04	8.38E-04	1.54E-03	5.2	6.3	5.2	6.3	>4
B10	WM4	4.38E-04	5.74E-04	9.78E-04	1.28E-03	5.2	6.3	5.2	6.3	>4
B11	WM4	5.01E-04	7.15E-04	1.12E-03	1.59E-03	5.2	6.3	5.2	6.3	>4
B12	WM4	1.00E-03	9.58E-04	2.23E-03	2.14E-03	5.2	6.3	5.2	6.3	>4
B13	WM4	3.90E-04	5.17E-04	8.71E-04	1.15E-03	5.2	6.3	5.2	6.3	>4
C1	DM5	2.61E-04	6.02E-04	5.83E-04	1.34E-03	5.6	6.7	5.6	6.7	>4
C2	NM5	3.35E-04	5.89E-04	7.48E-04	1.31E-03	5.3	6.8	5.3	6.8	>4
C3*	NM3	5.86E-04	9.85E-04	1.31E-03	2.20E-03	5.3	6.8	5.3	6.8	>2
C4	NM1	4.40E-04	6.11E-04	9.81E-04	1.36E-03	5.2	6.5	5.2	6.5	>4
C7a	NM3	2.60E-03	1.92E-03	5.80E-03	4.28E-03	5.3	6.8	5.3	6.8	>4
C7b	NM6	9.47E-03	1.79E-03	2.11E-02	3.98E-03	6.1	7.0	6.1	6.9	>4
C8	NM3	1.16E-03	1.99E-03	2.58E-03	4.43E-03	5.3	6.8	5.3	6.8	>4
C9	DM4	2.67E-04	6.18E-04	5.95E-04	1.38E-03	5.9	6.7	5.9	6.7	>4
C10	NM2	4.27E-04	1.12E-03	9.53E-04	2.51E-03	5.8	6.6	5.8	6.6	>4
C11	NM6	7.18E-04	8.12E-04	1.60E-03	1.81E-03	6.1	7.0	6.1	6.9	>4
C12*	WM1	9.04E-05	7.36E-05	2.02E-04	1.64E-04	5.6	6.8	5.6	6.8	>2
C13	WM1	1.65E-04	1.73E-04	3.68E-04	3.85E-04	5.6	6.8	5.6	6.8	>4
C14	WM1	2.50E-04	2.61E-04	5.58E-04	5.83E-04	5.6	6.8	5.6	6.8	>4
C15	NM3	2.89E-04	5.96E-04	6.43E-04	1.33E-03	5.3	6.8	5.3	6.8	>4
C20*	WM3	1.87E-04	3.04E-04	4.17E-04	6.78E-04	5.1	6.3	5.1	6.2	>2
CR2	NM6	1.36E-02	4.39E-03	3.04E-02	9.79E-03	6.1	7.0	6.1	6.9	>4
CR3	NM3	8.50E-04	2.53E-03	1.90E-03	5.64E-03	5.3	6.8	5.3	6.8	>4
CR4	WM1	8.23E-05	2.11E-04	1.83E-04	4.70E-04	5.6	6.8	5.6	6.8	>4
CR5	WM2	1.95E-04	3.62E-04	4.35E-04	8.07E-04	5.6	6.5	5.6	6.5	>4
E1	DM3	5.67E-04	8.56E-04	1.26E-03	1.91E-03	5.9	6.8	5.9	6.8	>4
E2	NM6	2.91E-03	3.73E-03	6.48E-03	8.32E-03	6.1	7.0	6.1	6.9	>4
E3	NM8	4.24E-04	1.10E-03	9.46E-04	2.44E-03	6.3	7.0	6.3	7.0	>4
E4	NM2	6.38E-04	2.70E-03	1.42E-03	6.02E-03	5.8	6.6	5.8	6.6	>4
E5	NM5	3.58E-03	3.92E-03	7.97E-03	8.74E-03	5.3	6.8	5.3	6.8	>4
E6	NM6	8.48E-03	2.82E-03	1.89E-02	6.30E-03	6.1	7.0	6.1	6.9	>4
E7	NM6	1.43E-02	1.77E-02	3.18E-02	3.95E-02	6.1	7.0	6.1	6.9	>4
E8	NM8	1.75E-03	3.68E-03	3.91E-03	8.20E-03	6.3	7.0	6.3	7.0	>4
E9	NM8	1.05E-03	1.61E-03	2.34E-03	3.60E-03	6.3	7.0	6.3	7.0	>4
E10	NM8	4.21E-03	6.68E-03	9.39E-03	1.49E-02	6.3	7.0	6.3	7.0	>4
E11	NM2	7.79E-04	1.97E-03	1.74E-03	4.40E-03	5.8	6.6	5.8	6.6	>4
E12	NM2	7.03E-04	1.01E-03	1.57E-03	2.25E-03	5.8	6.6	5.8	6.6	>4
F1	WM4	4.35E-04	7.10E-04	9.69E-04	1.58E-03	5.2	6.3	5.2	6.3	>5
F2	NM5	1.44E-03	3.15E-03	3.21E-03	7.03E-03	5.3	6.8	5.3	6.8	>4
F3	NM8	1.05E-03	1.61E-03	2.34E-03	3.60E-03	6.3	7.0	6.3	7.0	>4
M1	NM3	3.46E-04	6.10E-04	7.71E-04	1.36E-03	5.3	6.8	5.3	6.8	N/A
M2	NM3	2.33E-04	6.25E-04	5.20E-04	1.39E-03	5.3	6.8	5.3	6.8	N/A
M3	NM6	8.99E-03	1.40E-02	2.01E-02	3.11E-02	6.1	7.0	6.1	6.9	N/A
M4a	NM5	3.93E-04	1.43E-03	8.76E-04	3.18E-03	5.3	6.8	5.3	6.8	N/A
M4b	NM5	2.62E-04	6.40E-04	5.84E-04	1.43E-03	5.3	6.8	5.3	6.8	N/A
M4c	NM6	7.76E-03	5.45E-03	1.73E-02	1.21E-02	6.1	7.0	6.1	6.9	N/A
M4d	NM6	1.43E-02	4.80E-03	3.19E-02	1.07E-02	6.1	7.0	6.1	6.9	N/A
M4e	NM6	7.81E-03	6.40E-03	1.74E-02	1.43E-02	6.1	7.0	6.1	6.9	N/A
M5	NM1	2.23E-04	6.89E-04	4.98E-04	1.54E-03	5.2	6.5	5.2	6.5	N/A
M6	NM2	3.95E-04	7.09E-04	8.81E-04	1.58E-03	5.8	6.6	5.8	6.6	N/A
M7	NM3	2.99E-04	5.88E-04	6.67E-04	1.31E-03	5.3	6.8	5.3	6.8	N/A
M8	NM5	2.60E-04	6.05E-04	5.79E-04	1.35E-03	5.3	6.8	5.3	6.8	N/A
M9	NM6	5.15E-03	5.78E-03	1.15E-02	1.29E-02	6.1	7.0	6.1	6.9	N/A
M10	NM8	4.75E-03	5.58E-03	1.06E-02	1.24E-02	6.3	7.0	6.3	7.0	N/A
M11	WM1	8.68E-05	1.23E-04	1.94E-04	2.75E-04	5.6	6.8	5.6	6.8	N/A
M12	WM2	1.23E-04	3.55E-04	2.74E-04	7.92E-04	5.6	6.5	5.6	6.5	N/A
M13	WM3	1.59E-04	3.43E-04	3.55E-04	7.65E-04	5.1	6.3	5.1	6.2	N/A
M14	WM4	1.67E-04	3.98E-04	3.73E-04	8.88E-04	5.2	6.3	5.2	6.3	N/A
M15	DM1	5.90E-04	8.04E-04	1.32E-03	1.79E-03	3.8	4.7	3.8	4.7	N/A
M16	DM2	2.91E-04	5.40E-04	6.49E-04	1.20E-03	4.6	5.8	4.6	5.8	N/A
M17	DM3	1.81E-04	4.94E-04	4.03E-04	1.10E-03	5.9	6.8	5.9	6.8	N/A
M18	DM4	2.45E-04	5.60E-04	5.47E-04	1.25E-03	5.9	6.7	5.9	6.7	N/A
M19	DM5	2.38E-04	6.49E-04	5.32E-04	1.45E-03	5.6	6.7	5.6	6.7	N/A
T1	NM2	3.98E-04	8.02E-04	8.88E-04	1.79E-03	5.8	6.6	5.8	6.6	>4
T2	WM1	2.57E-04	1.40E-04	5.73E-04	3.12E-04	5.6	6.8	5.6	6.8	>4

Note: ¹ Based on the mean of all values between 1986 and 2012 for wet season and dry season from each of EPD’s baseline monitoring stations (refer to Table 8.23)

* Represents WSD seawater intake, therefore, DO criteria is > 2 mg/L

N/A = not applicable (for observation points)

Table 8.66: Summary of Changes to Bottom Layer DO Levels due to Elevated SS Release

WSR / Obs Point	Associated EPD monitoring station	Max. SS Concentration (kg/m³)		DO Depletion (mg/L)		Baseline DO¹ – bottom layer (mg/L)		Bottom Layer DO Level at WSR / Observation Point (mg/L)		DO Criteria (mg/L)
WSR / Obs Point	Associated EPD monitoring station	Wet	Dry	Wet	Dry	Wet	Dry	Wet	Dry
B1	NM3	2.34E-03	2.99E-03	5.21E-03	6.66E-03	4.7	6.8	4.7	6.8	>2
B2	NM5	1.61E-03	2.60E-03	3.59E-03	5.81E-03	4.6	6.8	4.6	6.7	>2
B3	NM2	2.40E-03	3.67E-03	5.35E-03	8.18E-03	5.2	6.7	5.2	6.6	>2
B4	WM4	6.15E-03	3.12E-03	1.37E-02	6.95E-03	4.7	6.3	4.7	6.3	>2
B5	WM4	1.81E-03	4.13E-03	4.04E-03	9.22E-03	4.7	6.3	4.7	6.3	>2
B6	NM2	2.70E-03	4.25E-03	6.03E-03	9.48E-03	5.2	6.7	5.2	6.6	>2
B7	NM5	2.95E-03	4.41E-03	6.58E-03	9.83E-03	4.6	6.8	4.6	6.7	>2
B8	NM5	2.95E-03	4.41E-03	6.58E-03	9.83E-03	4.6	6.8	4.6	6.7	>2
B9	WM4	1.01E-03	9.78E-04	2.25E-03	2.18E-03	4.7	6.3	4.7	6.3	>2
B10	WM4	9.71E-04	1.28E-03	2.16E-03	2.86E-03	4.7	6.3	4.7	6.3	>2
B11	WM4	1.29E-03	1.97E-03	2.87E-03	4.38E-03	4.7	6.3	4.7	6.3	>2
B12	WM4	2.61E-03	2.53E-03	5.82E-03	5.64E-03	4.7	6.3	4.7	6.3	>2
B13	WM4	9.10E-04	1.06E-03	2.03E-03	2.35E-03	4.7	6.3	4.7	6.3	>2
C1	DM5	7.66E-04	1.32E-03	1.71E-03	2.93E-03	5.1	6.7	5.1	6.7	>2
C2	NM5	5.67E-04	8.78E-04	1.26E-03	1.96E-03	4.6	6.8	4.6	6.8	>2
C3*	NM3	2.19E-03	3.29E-03	4.89E-03	7.33E-03	4.7	6.8	4.7	6.8	>2
C4	NM1	1.19E-03	1.56E-03	2.66E-03	3.48E-03	4.6	6.6	4.6	6.6	>2
C7a	NM3	1.59E-03	3.40E-03	3.56E-03	7.58E-03	4.7	6.8	4.7	6.8	>2
C7b	NM6	4.76E-03	2.58E-03	1.06E-02	5.76E-03	5.8	7.0	5.8	7.0	>2
C8	NM3	1.83E-03	3.39E-03	4.08E-03	7.56E-03	4.7	6.8	4.7	6.8	>2
C9	DM4	1.32E-03	1.88E-03	2.95E-03	4.19E-03	5.6	6.7	5.6	6.7	>2
C10	NM2	1.00E-03	1.73E-03	2.24E-03	3.86E-03	5.2	6.7	5.2	6.6	>2
C11	NM6	7.47E-04	1.24E-03	1.67E-03	2.77E-03	5.8	7.0	5.8	7.0	>2
C12*	WM1	1.61E-04	1.74E-04	3.59E-04	3.89E-04	4.8	6.9	4.8	6.9	>2
C13	WM1	3.95E-04	2.63E-04	8.80E-04	5.85E-04	4.8	6.9	4.8	6.9	>2
C14	WM1	3.83E-04	5.09E-04	8.54E-04	1.14E-03	4.8	6.9	4.8	6.9	>2
C15	NM3	6.69E-04	7.81E-04	1.49E-03	1.74E-03	4.7	6.8	4.7	6.8	>2
C20*	WM3	3.78E-04	5.59E-04	8.42E-04	1.25E-03	4.8	6.4	4.8	6.4	>2
CR2	NM6	9.44E-02	5.20E-03	2.11E-01	1.16E-02	5.8	7.0	5.6	7.0	>2
CR3	NM3	1.85E-03	2.91E-03	4.13E-03	6.48E-03	4.7	6.8	4.7	6.8	>2
CR4	WM1	1.19E-04	3.55E-04	2.66E-04	7.92E-04	4.8	6.9	4.8	6.9	>2
CR5	WM2	3.67E-04	8.45E-04	8.18E-04	1.88E-03	5.1	6.5	5.1	6.5	>2
E1	DM3	4.31E-03	3.27E-03	9.62E-03	7.29E-03	6.4	7.5	6.3	7.5	>2
E2	NM6	8.08E-03	1.35E-02	1.80E-02	3.00E-02	5.8	7.0	5.8	7.0	>2
E3	NM8	3.79E-04	1.37E-03	8.45E-04	3.06E-03	5.8	7.0	5.8	7.0	>2
E4	NM2	2.08E-03	4.33E-03	4.64E-03	9.65E-03	5.2	6.7	5.2	6.6	>2
E5	NM5	2.70E-02	5.90E-03	6.01E-02	1.31E-02	4.6	6.8	4.5	6.7	>2
E6	NM6	6.71E-03	5.55E-03	1.50E-02	1.24E-02	5.8	7.0	5.8	7.0	>2
E7	NM6	7.20E-02	5.29E-02	1.61E-01	1.18E-01	5.8	7.0	5.6	6.9	>2
E8	NM8	3.42E-03	5.90E-03	7.63E-03	1.32E-02	5.8	7.0	5.8	7.0	>2
E9	NM8	1.52E-03	3.29E-03	3.38E-03	7.33E-03	5.8	7.0	5.8	7.0	>2
E10	NM8	3.12E-02	3.34E-02	6.95E-02	7.45E-02	5.8	7.0	5.7	6.9	>2
E11	NM2	3.16E-03	4.99E-03	7.05E-03	1.11E-02	5.2	6.7	5.2	6.6	>2
E12	NM2	8.33E-04	1.64E-03	1.86E-03	3.66E-03	5.2	6.7	5.2	6.6	>2
F1	WM4	7.04E-04	1.35E-03	1.57E-03	3.02E-03	4.7	6.3	4.7	6.3	>2
F2	NM5	5.82E-03	4.94E-03	1.30E-02	1.10E-02	4.6	6.8	4.6	6.7	>2
F3	NM8	1.52E-03	3.29E-03	3.38E-03	7.33E-03	5.8	7.0	5.8	7.0	>2
M1	NM3	4.82E-04	1.09E-03	1.08E-03	2.43E-03	4.7	6.8	4.7	6.8	N/A
M2	NM3	6.20E-04	1.66E-03	1.38E-03	3.70E-03	4.7	6.8	4.7	6.8	N/A
M3	NM6	4.50E-02	1.48E-02	1.00E-01	3.31E-02	5.8	7.0	5.7	7.0	N/A
M4a	NM5	1.05E-03	2.68E-03	2.34E-03	5.98E-03	4.6	6.8	4.6	6.7	N/A
M4b	NM5	6.07E-04	1.07E-03	1.35E-03	2.39E-03	4.6	6.8	4.6	6.8	N/A
M4c	NM6	5.46E-02	5.87E-03	1.22E-01	1.31E-02	5.8	7.0	5.6	7.0	N/A
M4d	NM6	9.99E-02	5.99E-03	2.23E-01	1.33E-02	5.8	7.0	5.5	7.0	N/A
M4e	NM6	5.79E-02	1.05E-02	1.29E-01	2.33E-02	5.8	7.0	5.6	7.0	N/A
M5	NM1	3.51E-04	1.09E-03	7.83E-04	2.44E-03	4.6	6.6	4.6	6.6	N/A
M6	NM2	5.60E-04	1.25E-03	1.25E-03	2.79E-03	5.2	6.7	5.2	6.7	N/A
M7	NM3	5.67E-04	1.18E-03	1.26E-03	2.63E-03	4.7	6.8	4.7	6.8	N/A
M8	NM5	5.81E-04	1.04E-03	1.30E-03	2.31E-03	4.6	6.8	4.6	6.8	N/A
M9	NM6	2.89E-02	4.52E-03	6.44E-02	1.01E-02	5.8	7.0	5.7	7.0	N/A
M10	NM8	1.56E-02	5.49E-03	3.49E-02	1.23E-02	5.8	7.0	5.8	7.0	N/A
M11	WM1	9.23E-05	2.73E-04	2.06E-04	6.09E-04	4.8	6.9	4.8	6.9	N/A
M12	WM2	2.04E-04	5.06E-04	4.54E-04	1.13E-03	5.1	6.5	5.1	6.5	N/A
M13	WM3	3.85E-04	7.47E-04	8.58E-04	1.67E-03	4.8	6.4	4.8	6.4	N/A
M14	WM4	2.60E-04	7.34E-04	5.80E-04	1.64E-03	4.7	6.3	4.7	6.3	N/A
M15	DM1	3.75E-03	4.73E-03	8.35E-03	1.05E-02	N/A	N/A	N/A	N/A	N/A
M16	DM2	2.26E-03	2.26E-03	5.03E-03	5.03E-03	N/A	N/A	N/A	N/A	N/A
M17	DM3	9.77E-04	1.87E-03	2.18E-03	4.17E-03	6.4	7.5	6.3	7.5	N/A
M18	DM4	1.36E-03	1.43E-03	3.04E-03	3.19E-03	5.6	6.7	5.6	6.7	N/A
M19	DM5	7.59E-04	1.54E-03	1.69E-03	3.43E-03	5.1	6.7	5.1	6.7	N/A
T1	NM2	1.46E-03	2.96E-03	3.26E-03	6.61E-03	5.2	6.7	5.2	6.6	>2
T2	WM1	6.78E-04	2.97E-04	1.51E-03	6.63E-04	4.8	6.9	4.8	6.9	>2

Note: ¹ Based on the mean of all values for wet season and dry season from each of EPD’s baseline monitoring stations (refer to Table 8.23)

* Represents WSD seawater intake, therefore, DO criteria is > 2 mg/L

N/A = not applicable (for observation points)

None = no baseline DO at this layer

8.7.1.51 As shown in Table 8.65 and Table 8.66, no significant depletion of DO due to elevated SS arising from the construction activities is anticipated, and consequently, there will be no adverse impact to DO levels at WSRs.

Nutrients and Other Contaminants

8.7.1.52 The results for the water jetting and excavation activities was obtained from a model simulation of the worst case scenario ‘C’ only. A summary of the dilution potential and associated contaminant concentration is shown in Table 8.67 and Table 8.68.

Table 8.67: Nutrient and Contaminant Concentrations at WSRs – Wet Season

		Concentration at WSR
WSR / Obs Point	Dilution	Hg (ug/L)	As (ug/L)	Tributyltin (ug TBT/L)	NH₃-N (mg/L)	NO₃-N (mg/L)	TKN (mg/L)	Total P (mg/L)	Ortho-P (mg/L)	Total PCBs (ug/L)	Total PAHs (ug/L)
Criteria		5.0E-02	2.5E+01	2.0E-04	2.0E-01	6.9E-01	5.1E-01	8.0E-02	4.0E-02	3.0E-02	5.0E-02
B1	8.4E+05	4.7E-06	1.9E-03	7.1E-07	3.6E-04	3.2E-05	4.9E-04	2.8E-05	7.6E-06	8.5E-06	3.2E-04
B2	1.9E+06	2.1E-06	8.8E-04	3.2E-07	1.6E-04	1.4E-05	2.2E-04	1.3E-05	3.4E-06	3.8E-06	1.5E-04
B3	5.6E+05	7.1E-06	2.9E-03	1.1E-06	5.4E-04	4.7E-05	7.3E-04	4.2E-05	1.1E-05	1.3E-05	4.8E-04
B4	4.3E+05	9.2E-06	3.8E-03	1.4E-06	7.0E-04	6.1E-05	9.5E-04	5.5E-05	1.5E-05	1.7E-05	6.2E-04
B5	7.1E+05	5.6E-06	2.3E-03	8.3E-07	4.2E-04	3.7E-05	5.7E-04	3.3E-05	8.9E-06	1.0E-05	3.8E-04
B6	9.2E+05	4.3E-06	1.8E-03	6.4E-07	3.3E-04	2.9E-05	4.4E-04	2.6E-05	6.9E-06	7.7E-06	2.9E-04
B7	1.0E+06	3.9E-06	1.6E-03	5.9E-07	3.0E-04	2.6E-05	4.0E-04	2.4E-05	6.3E-06	7.1E-06	2.7E-04
B8	1.0E+06	3.9E-06	1.6E-03	5.9E-07	3.0E-04	2.6E-05	4.0E-04	2.4E-05	6.3E-06	7.1E-06	2.7E-04
B9	2.2E+06	1.8E-06	7.5E-04	2.7E-07	1.4E-04	1.2E-05	1.9E-04	1.1E-05	2.9E-06	3.3E-06	1.2E-04
B10	2.4E+06	1.7E-06	6.8E-04	2.5E-07	1.3E-04	1.1E-05	1.7E-04	1.0E-05	2.7E-06	3.0E-06	1.1E-04
B11	9.5E+05	4.2E-06	1.7E-03	6.2E-07	3.2E-04	2.8E-05	4.3E-04	2.5E-05	6.7E-06	7.5E-06	2.8E-04
B12	7.5E+05	5.3E-06	2.2E-03	7.9E-07	4.0E-04	3.5E-05	5.4E-04	3.2E-05	8.4E-06	9.5E-06	3.6E-04
B13	1.2E+06	3.2E-06	1.3E-03	4.9E-07	2.5E-04	2.2E-05	3.3E-04	1.9E-05	5.2E-06	5.8E-06	2.2E-04
C1	3.7E+06	1.1E-06	4.4E-04	1.6E-07	8.2E-05	7.2E-06	1.1E-04	6.4E-06	1.7E-06	1.9E-06	7.3E-05
C2	2.6E+06	1.5E-06	6.2E-04	2.3E-07	1.1E-04	1.0E-05	1.6E-04	9.0E-06	2.4E-06	2.7E-06	1.0E-04
C3	6.9E+05	5.7E-06	2.4E-03	8.6E-07	4.4E-04	3.8E-05	5.9E-04	3.4E-05	9.2E-06	1.0E-05	3.9E-04
C4	2.3E+06	1.7E-06	7.0E-04	2.6E-07	1.3E-04	1.1E-05	1.8E-04	1.0E-05	2.7E-06	3.1E-06	1.2E-04
C7a	6.9E+05	5.7E-06	2.4E-03	8.6E-07	4.4E-04	3.8E-05	5.9E-04	3.4E-05	9.2E-06	1.0E-05	3.9E-04
C7b	1.9E+05	2.1E-05	8.7E-03	3.2E-06	1.6E-03	1.4E-04	2.2E-03	1.3E-04	3.4E-05	3.8E-05	1.4E-03
C8	1.1E+06	3.5E-06	1.4E-03	5.2E-07	2.6E-04	2.3E-05	3.6E-04	2.1E-05	5.6E-06	6.2E-06	2.4E-04
C9	2.2E+06	1.8E-06	7.2E-04	2.6E-07	1.3E-04	1.2E-05	1.8E-04	1.1E-05	2.8E-06	3.2E-06	1.2E-04
C10	1.3E+06	3.2E-06	1.3E-03	4.7E-07	2.4E-04	2.1E-05	3.3E-04	1.9E-05	5.1E-06	5.7E-06	2.1E-04
C11	1.4E+06	2.8E-06	1.1E-03	4.2E-07	2.1E-04	1.9E-05	2.9E-04	1.7E-05	4.4E-06	5.0E-06	1.9E-04
C12	8.4E+06	4.7E-07	1.9E-04	7.1E-08	3.6E-05	3.2E-06	4.9E-05	2.8E-06	7.5E-07	8.5E-07	3.2E-05
C13	4.6E+06	8.6E-07	3.5E-04	1.3E-07	6.5E-05	5.8E-06	8.8E-05	5.2E-06	1.4E-06	1.5E-06	5.8E-05
C14	2.8E+06	1.4E-06	5.7E-04	2.1E-07	1.1E-04	9.3E-06	1.4E-04	8.3E-06	2.2E-06	2.5E-06	9.4E-05
C15	3.6E+06	1.1E-06	4.6E-04	1.7E-07	8.4E-05	7.4E-06	1.1E-04	6.7E-06	1.8E-06	2.0E-06	7.5E-05
C20	4.7E+06	8.5E-07	3.5E-04	1.3E-07	6.4E-05	5.7E-06	8.7E-05	5.1E-06	1.4E-06	1.5E-06	5.8E-05
CR2	3.2E+04	1.3E-04	5.1E-02	1.9E-05	9.5E-03	8.4E-04	1.3E-02	7.5E-04	2.0E-04	2.3E-04	8.5E-03
CR3	1.2E+06	3.3E-06	1.4E-03	5.0E-07	2.5E-04	2.2E-05	3.4E-04	2.0E-05	5.3E-06	6.0E-06	2.3E-04
CR4	5.1E+06	7.8E-07	3.2E-04	1.2E-07	5.9E-05	5.2E-06	8.0E-05	4.7E-06	1.2E-06	1.4E-06	5.3E-05
CR5	2.8E+06	1.4E-06	5.7E-04	2.1E-07	1.1E-04	9.4E-06	1.4E-04	8.4E-06	2.2E-06	2.5E-06	9.5E-05
E1	6.9E+05	5.7E-06	2.4E-03	8.6E-07	4.4E-04	3.8E-05	5.9E-04	3.4E-05	9.2E-06	1.0E-05	3.9E-04
E2	2.2E+05	1.8E-05	7.3E-03	2.7E-06	1.4E-03	1.2E-04	1.8E-03	1.1E-04	2.9E-05	3.2E-05	1.2E-03
E3	1.4E+06	2.9E-06	1.2E-03	4.4E-07	2.2E-04	2.0E-05	3.0E-04	1.8E-05	4.7E-06	5.3E-06	2.0E-04
E4	1.4E+06	2.8E-06	1.1E-03	4.2E-07	2.1E-04	1.9E-05	2.8E-04	1.7E-05	4.4E-06	5.0E-06	1.9E-04
E5	1.1E+05	3.6E-05	1.5E-02	5.4E-06	2.7E-03	2.4E-04	3.7E-03	2.2E-04	5.7E-05	6.5E-05	2.4E-03
E6	1.8E+05	2.2E-05	8.9E-03	3.2E-06	1.6E-03	1.4E-04	2.2E-03	1.3E-04	3.5E-05	3.9E-05	1.5E-03
E7	4.1E+04	9.6E-05	3.9E-02	1.4E-05	7.3E-03	6.4E-04	9.9E-03	5.7E-04	1.5E-04	1.7E-04	6.5E-03
E8	8.7E+05	4.5E-06	1.9E-03	6.8E-07	3.5E-04	3.0E-05	4.7E-04	2.7E-05	7.3E-06	8.2E-06	3.1E-04
E9	1.3E+06	3.1E-06	1.3E-03	4.7E-07	2.4E-04	2.1E-05	3.2E-04	1.9E-05	5.0E-06	5.6E-06	2.1E-04
E10	9.6E+04	4.1E-05	1.7E-02	6.2E-06	3.1E-03	2.8E-04	4.3E-03	2.5E-04	6.6E-05	7.5E-05	2.8E-03
E11	9.4E+05	4.2E-06	1.7E-03	6.3E-07	3.2E-04	2.8E-05	4.3E-04	2.5E-05	6.7E-06	7.6E-06	2.9E-04
E12	2.1E+06	1.9E-06	7.7E-04	2.8E-07	1.4E-04	1.3E-05	1.9E-04	1.1E-05	3.0E-06	3.4E-06	1.3E-04
F1	2.7E+06	1.4E-06	5.9E-04	2.2E-07	1.1E-04	9.7E-06	1.5E-04	8.7E-06	2.3E-06	2.6E-06	9.8E-05
F2	5.1E+05	7.7E-06	3.2E-03	1.2E-06	5.9E-04	5.2E-05	8.0E-04	4.6E-05	1.2E-05	1.4E-05	5.3E-04
F3	1.3E+06	3.1E-06	1.3E-03	4.7E-07	2.4E-04	2.1E-05	3.2E-04	1.9E-05	5.0E-06	5.6E-06	2.1E-04
M1	3.5E+06	1.1E-06	4.6E-04	1.7E-07	8.5E-05	7.5E-06	1.2E-04	6.7E-06	1.8E-06	2.0E-06	7.6E-05
M2	3.8E+06	1.0E-06	4.2E-04	1.5E-07	7.8E-05	6.9E-06	1.1E-04	6.2E-06	1.7E-06	1.9E-06	7.0E-05
M3	6.6E+04	6.0E-05	2.5E-02	9.0E-06	4.5E-03	4.0E-04	6.2E-03	3.6E-04	9.6E-05	1.1E-04	4.1E-03
M4a	2.0E+06	2.0E-06	8.0E-04	2.9E-07	1.5E-04	1.3E-05	2.0E-04	1.2E-05	3.1E-06	3.5E-06	1.3E-04
M4b	3.8E+06	1.0E-06	4.2E-04	1.5E-07	7.8E-05	6.9E-06	1.1E-04	6.2E-06	1.7E-06	1.9E-06	7.0E-05
M4c	5.5E+04	7.3E-05	3.0E-02	1.1E-05	5.5E-03	4.9E-04	7.5E-03	4.4E-04	1.2E-04	1.3E-04	4.9E-03
M4d	3.0E+04	1.3E-04	5.4E-02	2.0E-05	1.0E-02	8.9E-04	1.4E-02	8.0E-04	2.1E-04	2.4E-04	9.0E-03
M4e	5.1E+04	7.7E-05	3.2E-02	1.2E-05	5.9E-03	5.2E-04	7.9E-03	4.6E-04	1.2E-04	1.4E-04	5.2E-03
M5	3.5E+06	1.1E-06	4.7E-04	1.7E-07	8.7E-05	7.7E-06	1.2E-04	6.9E-06	1.8E-06	2.1E-06	7.8E-05
M6	2.9E+06	1.4E-06	5.6E-04	2.1E-07	1.0E-04	9.2E-06	1.4E-04	8.3E-06	2.2E-06	2.5E-06	9.4E-05
M7	3.2E+06	1.2E-06	5.1E-04	1.9E-07	9.4E-05	8.3E-06	1.3E-04	7.4E-06	2.0E-06	2.2E-06	8.4E-05
M8	4.1E+06	9.6E-07	3.9E-04	1.4E-07	7.3E-05	6.4E-06	9.9E-05	5.8E-06	1.5E-06	1.7E-06	6.5E-05
M9	1.0E+05	3.8E-05	1.6E-02	5.8E-06	2.9E-03	2.6E-04	4.0E-03	2.3E-04	6.1E-05	6.9E-05	2.6E-03
M10	1.9E+05	2.1E-05	8.5E-03	3.1E-06	1.6E-03	1.4E-04	2.1E-03	1.2E-04	3.3E-05	3.7E-05	1.4E-03
M11	6.5E+06	6.1E-07	2.5E-04	9.2E-08	4.7E-05	4.1E-06	6.3E-05	3.7E-06	9.8E-07	1.1E-06	4.2E-05
M12	4.5E+06	8.8E-07	3.6E-04	1.3E-07	6.7E-05	5.9E-06	9.1E-05	5.3E-06	1.4E-06	1.6E-06	6.0E-05
M13	5.0E+06	8.0E-07	3.3E-04	1.2E-07	6.0E-05	5.3E-06	8.2E-05	4.8E-06	1.3E-06	1.4E-06	5.4E-05
M14	5.8E+06	6.8E-07	2.8E-04	1.0E-07	5.2E-05	4.6E-06	7.0E-05	4.1E-06	1.1E-06	1.2E-06	4.6E-05
M15	8.0E+05	5.0E-06	2.0E-03	7.5E-07	3.8E-04	3.3E-05	5.1E-04	3.0E-05	8.0E-06	9.0E-06	3.4E-04
M16	1.3E+06	3.0E-06	1.2E-03	4.5E-07	2.3E-04	2.0E-05	3.1E-04	1.8E-05	4.8E-06	5.4E-06	2.0E-04
M17	2.7E+06	1.5E-06	6.1E-04	2.2E-07	1.1E-04	9.9E-06	1.5E-04	8.9E-06	2.4E-06	2.7E-06	1.0E-04
M18	2.2E+06	1.8E-06	7.4E-04	2.7E-07	1.4E-04	1.2E-05	1.9E-04	1.1E-05	2.9E-06	3.3E-06	1.2E-04
M19	3.9E+06	1.0E-06	4.1E-04	1.5E-07	7.7E-05	6.8E-06	1.0E-04	6.0E-06	1.6E-06	1.8E-06	6.9E-05
T1	2.0E+06	1.9E-06	8.0E-04	2.9E-07	1.5E-04	1.3E-05	2.0E-04	1.2E-05	3.1E-06	3.5E-06	1.3E-04
T2	2.8E+06	1.4E-06	5.8E-04	2.1E-07	1.1E-04	9.5E-06	1.5E-04	8.5E-06	2.3E-06	2.6E-06	9.7E-05

Table 8.68: Nutrient and Contaminant Concentrations at WSRs – Dry Season

			Concentration at WSR
WSR / Obs Point	Dilution	Hg (ug/L)		As (ug/L)	Tributyltin (ug TBT/L)	NH₃-N (mg/L)	NO₃-N (mg/L)	TKN (mg/L)	Total P (mg/L)	Ortho-P (mg/L)	Total PCBs (ug/L)	Total PAHs (ug/L)
Criteria		5.0E-02		2.5E+01	2.0E-04	2.0E-01	6.9E-01	5.1E-01	8.0E-02	4.0E-02	3.0E-02	5.0E-02
B1	5.9E+05	6.7E-06		2.8E-03	1.0E-06	5.1E-04	4.5E-05	6.9E-04	4.0E-05	1.1E-05	1.2E-05	4.6E-04
B2	1.1E+06	3.6E-06		1.5E-03	5.5E-07	2.8E-04	2.4E-05	3.8E-04	2.2E-05	5.8E-06	6.6E-06	2.5E-04
B3	5.7E+05	7.0E-06		2.9E-03	1.0E-06	5.3E-04	4.7E-05	7.2E-04	4.2E-05	1.1E-05	1.3E-05	4.7E-04
B4	2.5E+05	1.6E-05		6.6E-03	2.4E-06	1.2E-03	1.1E-04	1.6E-03	9.6E-05	2.6E-05	2.9E-05	1.1E-03
B5	7.2E+05	5.5E-06		2.3E-03	8.2E-07	4.2E-04	3.7E-05	5.7E-04	3.3E-05	8.8E-06	9.9E-06	3.7E-04
B6	6.5E+05	6.1E-06		2.5E-03	9.2E-07	4.6E-04	4.1E-05	6.3E-04	3.7E-05	9.8E-06	1.1E-05	4.2E-04
B7	4.4E+05	9.0E-06		3.7E-03	1.3E-06	6.8E-04	6.0E-05	9.3E-04	5.4E-05	1.4E-05	1.6E-05	6.1E-04
B8	4.4E+05	9.0E-06		3.7E-03	1.3E-06	6.8E-04	6.0E-05	9.3E-04	5.4E-05	1.4E-05	1.6E-05	6.1E-04
B9	1.8E+06	2.2E-06		8.8E-04	3.2E-07	1.6E-04	1.4E-05	2.2E-04	1.3E-05	3.4E-06	3.9E-06	1.5E-04
B10	1.9E+06	2.1E-06		8.5E-04	3.1E-07	1.6E-04	1.4E-05	2.1E-04	1.2E-05	3.3E-06	3.7E-06	1.4E-04
B11	6.7E+05	5.9E-06		2.4E-03	8.8E-07	4.5E-04	3.9E-05	6.1E-04	3.5E-05	9.4E-06	1.1E-05	4.0E-04
B12	6.9E+05	5.8E-06		2.4E-03	8.6E-07	4.4E-04	3.9E-05	5.9E-04	3.5E-05	9.2E-06	1.0E-05	3.9E-04
B13	1.5E+06	2.6E-06		1.1E-03	3.9E-07	2.0E-04	1.7E-05	2.6E-04	1.5E-05	4.1E-06	4.6E-06	1.7E-04
C1	2.1E+06	1.9E-06		7.7E-04	2.8E-07	1.4E-04	1.3E-05	1.9E-04	1.1E-05	3.0E-06	3.4E-06	1.3E-04
C2	1.5E+06	2.6E-06		1.1E-03	4.0E-07	2.0E-04	1.8E-05	2.7E-04	1.6E-05	4.2E-06	4.7E-06	1.8E-04
C3	4.8E+05	8.3E-06		3.4E-03	1.2E-06	6.3E-04	5.6E-05	8.5E-04	5.0E-05	1.3E-05	1.5E-05	5.6E-04
C4	1.4E+06	2.9E-06		1.2E-03	4.4E-07	2.2E-04	2.0E-05	3.0E-04	1.8E-05	4.7E-06	5.3E-06	2.0E-04
C7a	7.1E+05	5.6E-06		2.3E-03	8.3E-07	4.2E-04	3.7E-05	5.7E-04	3.3E-05	8.9E-06	1.0E-05	3.8E-04
C7b	7.5E+05	5.3E-06		2.2E-03	7.9E-07	4.0E-04	3.5E-05	5.4E-04	3.2E-05	8.4E-06	9.5E-06	3.6E-04
C8	8.8E+05	4.5E-06		1.8E-03	6.8E-07	3.4E-04	3.0E-05	4.6E-04	2.7E-05	7.2E-06	8.1E-06	3.1E-04
C9	1.3E+06	3.0E-06		1.2E-03	4.6E-07	2.3E-04	2.0E-05	3.1E-04	1.8E-05	4.9E-06	5.5E-06	2.1E-04
C10	5.0E+05	8.0E-06		3.3E-03	1.2E-06	6.1E-04	5.3E-05	8.2E-04	4.8E-05	1.3E-05	1.4E-05	5.4E-04
C11	1.2E+06	3.2E-06		1.3E-03	4.8E-07	2.4E-04	2.2E-05	3.3E-04	1.9E-05	5.1E-06	5.8E-06	2.2E-04
C12	8.3E+06	4.8E-07		2.0E-04	7.2E-08	3.6E-05	3.2E-06	4.9E-05	2.9E-06	7.6E-07	8.6E-07	3.3E-05
C13	6.0E+06	6.6E-07		2.7E-04	9.8E-08	5.0E-05	4.4E-06	6.7E-05	3.9E-06	1.0E-06	1.2E-06	4.5E-05
C14	4.2E+06	9.4E-07		3.9E-04	1.4E-07	7.2E-05	6.3E-06	9.7E-05	5.6E-06	1.5E-06	1.7E-06	6.4E-05
C15	1.9E+06	2.1E-06		8.7E-04	3.2E-07	1.6E-04	1.4E-05	2.2E-04	1.3E-05	3.4E-06	3.8E-06	1.4E-04
C20	3.6E+06	1.1E-06		4.5E-04	1.6E-07	8.3E-05	7.3E-06	1.1E-04	6.5E-06	1.7E-06	2.0E-06	7.4E-05
CR2	4.9E+05	8.1E-06		3.3E-03	1.2E-06	6.2E-04	5.5E-05	8.4E-04	4.9E-05	1.3E-05	1.5E-05	5.5E-04
CR3	6.5E+05	6.1E-06		2.5E-03	9.2E-07	4.7E-04	4.1E-05	6.3E-04	3.7E-05	9.8E-06	1.1E-05	4.2E-04
CR4	6.5E+06	6.1E-07		2.5E-04	9.1E-08	4.6E-05	4.1E-06	6.2E-05	3.6E-06	9.7E-07	1.1E-06	4.1E-05
CR5	3.5E+06	1.1E-06		4.6E-04	1.7E-07	8.5E-05	7.5E-06	1.2E-04	6.7E-06	1.8E-06	2.0E-06	7.6E-05
E1	8.9E+05	4.4E-06		1.8E-03	6.7E-07	3.4E-04	3.0E-05	4.6E-04	2.7E-05	7.1E-06	8.0E-06	3.0E-04
E2	1.8E+05	2.3E-05		9.2E-03	3.4E-06	1.7E-03	1.5E-04	2.3E-03	1.4E-04	3.6E-05	4.1E-05	1.5E-03
E3	1.7E+06	2.3E-06		9.6E-04	3.5E-07	1.8E-04	1.6E-05	2.4E-04	1.4E-05	3.8E-06	4.2E-06	1.6E-04
E4	6.9E+05	5.8E-06		2.4E-03	8.6E-07	4.4E-04	3.9E-05	5.9E-04	3.5E-05	9.2E-06	1.0E-05	3.9E-04
E5	5.1E+05	7.8E-06		3.2E-03	1.2E-06	6.0E-04	5.2E-05	8.1E-04	4.7E-05	1.3E-05	1.4E-05	5.3E-04
E6	5.2E+05	7.6E-06		3.1E-03	1.1E-06	5.7E-04	5.1E-05	7.8E-04	4.5E-05	1.2E-05	1.4E-05	5.1E-04
E7	4.4E+04	9.0E-05		3.7E-02	1.3E-05	6.8E-03	6.0E-04	9.3E-03	5.4E-04	1.4E-04	1.6E-04	6.1E-03
E8	4.1E+05	9.6E-06		3.9E-03	1.4E-06	7.3E-04	6.5E-05	9.9E-04	5.8E-05	1.5E-05	1.7E-05	6.5E-04
E9	9.1E+05	4.4E-06		1.8E-03	6.5E-07	3.3E-04	2.9E-05	4.5E-04	2.6E-05	7.0E-06	7.9E-06	3.0E-04
E10	7.6E+04	5.2E-05		2.1E-02	7.9E-06	4.0E-03	3.5E-04	5.4E-03	3.1E-04	8.4E-05	9.4E-05	3.6E-03
E11	5.7E+05	7.0E-06		2.9E-03	1.0E-06	5.3E-04	4.7E-05	7.2E-04	4.2E-05	1.1E-05	1.3E-05	4.7E-04
E12	1.3E+06	3.2E-06		1.3E-03	4.7E-07	2.4E-04	2.1E-05	3.2E-04	1.9E-05	5.0E-06	5.7E-06	2.1E-04
F1	2.1E+06	1.9E-06		7.7E-04	2.8E-07	1.4E-04	1.3E-05	1.9E-04	1.1E-05	3.0E-06	3.4E-06	1.3E-04
F2	6.0E+05	6.6E-06		2.7E-03	9.8E-07	5.0E-04	4.4E-05	6.8E-04	3.9E-05	1.1E-05	1.2E-05	4.5E-04
F3	9.1E+05	4.4E-06		1.8E-03	6.5E-07	3.3E-04	2.9E-05	4.5E-04	2.6E-05	7.0E-06	7.9E-06	3.0E-04
M1	2.6E+06	1.5E-06		6.1E-04	2.2E-07	1.1E-04	1.0E-05	1.5E-04	9.0E-06	2.4E-06	2.7E-06	1.0E-04
M2	1.8E+06	2.2E-06		9.0E-04	3.3E-07	1.7E-04	1.5E-05	2.3E-04	1.3E-05	3.5E-06	4.0E-06	1.5E-04
M3	1.3E+05	3.0E-05		1.2E-02	4.5E-06	2.3E-03	2.0E-04	3.1E-03	1.8E-04	4.8E-05	5.4E-05	2.1E-03
M4a	1.1E+06	3.6E-06		1.5E-03	5.3E-07	2.7E-04	2.4E-05	3.7E-04	2.1E-05	5.7E-06	6.4E-06	2.4E-04
M4b	2.7E+06	1.5E-06		6.0E-04	2.2E-07	1.1E-04	9.7E-06	1.5E-04	8.7E-06	2.3E-06	2.6E-06	9.9E-05
M4c	4.3E+05	9.2E-06		3.8E-03	1.4E-06	7.0E-04	6.2E-05	9.5E-04	5.5E-05	1.5E-05	1.7E-05	6.3E-04
M4d	4.8E+05	8.3E-06		3.4E-03	1.2E-06	6.3E-04	5.5E-05	8.5E-04	5.0E-05	1.3E-05	1.5E-05	5.6E-04
M4e	2.8E+05	1.4E-05		5.7E-03	2.1E-06	1.1E-03	9.3E-05	1.4E-03	8.3E-05	2.2E-05	2.5E-05	9.5E-04
M5	2.4E+06	1.6E-06		6.8E-04	2.5E-07	1.3E-04	1.1E-05	1.7E-04	9.9E-06	2.6E-06	3.0E-06	1.1E-04
M6	1.8E+06	2.2E-06		9.0E-04	3.3E-07	1.7E-04	1.5E-05	2.3E-04	1.3E-05	3.5E-06	4.0E-06	1.5E-04
M7	2.5E+06	1.6E-06		6.4E-04	2.4E-07	1.2E-04	1.1E-05	1.6E-04	9.4E-06	2.5E-06	2.8E-06	1.1E-04
M8	2.2E+06	1.8E-06		7.5E-04	2.7E-07	1.4E-04	1.2E-05	1.9E-04	1.1E-05	2.9E-06	3.3E-06	1.2E-04
M9	4.4E+05	9.1E-06		3.7E-03	1.4E-06	6.9E-04	6.1E-05	9.4E-04	5.5E-05	1.5E-05	1.6E-05	6.2E-04
M10	4.1E+05	9.6E-06		3.9E-03	1.4E-06	7.3E-04	6.4E-05	9.9E-04	5.8E-05	1.5E-05	1.7E-05	6.5E-04
M11	8.1E+06	4.9E-07		2.0E-04	7.4E-08	3.7E-05	3.3E-06	5.1E-05	2.9E-06	7.9E-07	8.8E-07	3.3E-05
M12	4.4E+06	9.1E-07		3.7E-04	1.4E-07	6.9E-05	6.1E-06	9.4E-05	5.4E-06	1.5E-06	1.6E-06	6.2E-05
M13	3.9E+06	1.0E-06		4.1E-04	1.5E-07	7.7E-05	6.8E-06	1.0E-04	6.1E-06	1.6E-06	1.8E-06	6.9E-05
M14	4.0E+06	9.9E-07		4.0E-04	1.5E-07	7.5E-05	6.6E-06	1.0E-04	5.9E-06	1.6E-06	1.8E-06	6.7E-05
M15	6.3E+05	6.3E-06		2.6E-03	9.4E-07	4.8E-04	4.2E-05	6.5E-04	3.8E-05	1.0E-05	1.1E-05	4.3E-04
M16	9.8E+05	4.0E-06		1.6E-03	6.0E-07	3.1E-04	2.7E-05	4.1E-04	2.4E-05	6.4E-06	7.2E-06	2.7E-04
M17	1.6E+06	2.5E-06		1.0E-03	3.7E-07	1.9E-04	1.7E-05	2.6E-04	1.5E-05	4.0E-06	4.5E-06	1.7E-04
M18	2.1E+06	1.9E-06		7.9E-04	2.9E-07	1.5E-04	1.3E-05	2.0E-04	1.2E-05	3.1E-06	3.5E-06	1.3E-04
M19	1.9E+06	2.0E-06		8.4E-04	3.1E-07	1.6E-04	1.4E-05	2.1E-04	1.2E-05	3.3E-06	3.7E-06	1.4E-04
T1	1.0E+06	3.9E-06		1.6E-03	5.9E-07	3.0E-04	2.6E-05	4.1E-04	2.4E-05	6.3E-06	7.1E-06	2.7E-04
T2	5.2E+06	7.5E-07		3.1E-04	1.1E-07	5.7E-05	5.1E-06	7.8E-05	4.5E-06	1.2E-06	1.4E-06	5.1E-05

8.7.1.53 The dilution results show that concentrations of all contaminants at WSRs are below the relevant criteria or baseline. Thus no adverse water quality impacts will arise due to construction activities for the submarine cable diversion.

Release of Contaminants from Pore Water

Release of Contaminants from Pore Water during DCM Process

8.7.1.54 Based on the calculated pore water release rates described in Section 8.6.5, a tracer dilution model was run using Delft3D-PART for the worst case scenario (Year 2017 which assumes 42 nos. of DCM operating simultaneously and each releasing 1 kg/s), and the dilution results from the model are shown in Table 8.69.

Table 8.69: Modelled Concentration and Equivalent Dilution for Contaminant Release due to the DCM Process

WSR / Obs Point	Modelled Concentration ‘C’ (mg/L) - Year 2017 Wet season			Modelled Concentration ‘C’ (mg/L) - Year 2017 Dry season			Equivalent Unit Dilution ‘F’ (L/s) - Year 2017 Wet season			Equivalent Unit Dilution ‘F’ (L/s) - Year 2017 Dry season
WSR / Obs Point	Surface	Middle	Bottom	Surface	Middle	Bottom	Surface	Middle	Bottom	Surface	Middle	Bottom
B1	5.86E+00	7.57E+00	3.99E+00	9.70E+00	8.72E+00	8.88E+00	7.17E+06	5.55E+06	1.05E+07	4.33E+06	4.82E+06	4.73E+06
B2	3.05E+00	3.24E+00	3.44E+00	8.07E+00	8.74E+00	9.14E+00	1.38E+07	1.30E+07	1.22E+07	5.20E+06	4.81E+06	4.60E+06
B3	1.83E+01	1.51E+01	4.25E+00	1.75E+01	1.11E+01	1.29E+01	2.30E+06	2.78E+06	9.89E+06	2.40E+06	3.79E+06	3.26E+06
B4	3.42E+01	1.17E+01	1.53E+01	2.93E+01	1.69E+01	1.21E+01	1.23E+06	3.59E+06	2.75E+06	1.43E+06	2.49E+06	3.47E+06
B5	9.00E+00	8.36E+00	5.87E+00	1.09E+01	7.82E+00	8.36E+00	4.67E+06	5.03E+06	7.16E+06	3.84E+06	5.37E+06	5.03E+06
B6	6.49E+00	1.00E+01	5.30E+00	1.20E+01	1.56E+01	8.19E+00	6.48E+06	4.19E+06	7.93E+06	3.50E+06	2.69E+06	5.13E+06
B7	5.69E+00	5.31E+00	8.10E+00	1.07E+01	1.06E+01	1.07E+01	7.38E+06	7.91E+06	5.19E+06	3.91E+06	3.98E+06	3.93E+06
B8	5.69E+00	5.31E+00	8.10E+00	1.07E+01	1.06E+01	1.07E+01	7.38E+06	7.91E+06	5.19E+06	3.91E+06	3.98E+06	3.93E+06
B9	3.82E+00	2.85E+00	2.07E+00	4.84E+00	3.45E+00	3.28E+00	1.10E+07	1.47E+07	2.03E+07	8.68E+06	1.22E+07	1.28E+07
B10	3.29E+00	2.48E+00	2.62E+00	4.23E+00	4.16E+00	3.21E+00	1.28E+07	1.70E+07	1.60E+07	9.94E+06	1.01E+07	1.31E+07
B11	6.42E+00	5.06E+00	5.06E+00	8.07E+00	5.23E+00	5.79E+00	6.54E+06	8.30E+06	8.30E+06	5.21E+06	8.04E+06	7.25E+06
B12	9.68E+00	9.64E+00	6.68E+00	8.31E+00	6.91E+00	6.31E+00	4.34E+06	4.36E+06	6.29E+06	5.05E+06	6.08E+06	6.66E+06
B13	5.45E+00	4.65E+00	3.11E+00	4.93E+00	4.95E+00	3.02E+00	7.70E+06	9.04E+06	1.35E+07	8.52E+06	8.48E+06	1.39E+07
C1	1.19E+00	1.81E+00	2.16E+00	3.52E+00	3.78E+00	3.76E+00	3.52E+07	2.32E+07	1.95E+07	1.19E+07	1.11E+07	1.12E+07
C2	2.36E+00	2.31E+00	1.75E+00	5.20E+00	5.18E+00	2.32E+00	1.78E+07	1.82E+07	2.40E+07	8.08E+06	8.11E+06	1.81E+07
C3	1.29E+01	5.06E+00	4.95E+00	1.52E+01	1.01E+01	7.64E+00	3.25E+06	8.30E+06	8.48E+06	2.76E+06	4.14E+06	5.50E+06
C4	3.12E+00	3.98E+00	2.44E+00	6.45E+00	5.01E+00	5.56E+00	1.35E+07	1.05E+07	1.72E+07	6.51E+06	8.38E+06	7.56E+06
C7a	4.60E+00	1.34E+01	1.96E+02	3.31E+01	3.40E+01	2.69E+01	9.13E+06	3.14E+06	2.14E+05	1.27E+06	1.24E+06	1.56E+06
C7b	5.14E+00	4.44E+00	2.52E+00	7.45E+00	8.00E+00	6.10E+00	8.17E+06	9.46E+06	1.67E+07	5.64E+06	5.25E+06	6.88E+06
C8	5.20E+00	6.67E+00	6.89E+00	9.14E+00	9.38E+00	9.66E+00	8.08E+06	6.30E+06	6.10E+06	4.59E+06	4.48E+06	4.35E+06
C9	2.32E+00	3.34E+00	2.50E+00	4.47E+00	6.01E+00	4.57E+00	1.81E+07	1.26E+07	1.68E+07	9.40E+06	6.99E+06	9.19E+06
C10	5.78E+00	5.05E+00	2.51E+00	8.53E+00	7.77E+00	4.96E+00	7.27E+06	8.32E+06	1.67E+07	4.92E+06	5.41E+06	8.46E+06
C11	4.40E+00	5.06E+00	1.78E+00	6.69E+00	6.58E+00	3.47E+00	9.55E+06	8.31E+06	2.37E+07	6.28E+06	6.39E+06	1.21E+07
C12	1.07E+00	8.17E-01	4.32E-01	6.43E-01	8.17E-01	4.40E-01	3.91E+07	5.14E+07	9.71E+07	6.54E+07	5.14E+07	9.54E+07
C13	1.75E+00	1.21E+00	9.13E-01	1.72E+00	1.17E+00	1.15E+00	2.40E+07	3.46E+07	4.60E+07	2.44E+07	3.58E+07	3.65E+07
C14	2.14E+00	1.73E+00	1.08E+00	1.91E+00	1.65E+00	1.55E+00	1.96E+07	2.43E+07	3.88E+07	2.20E+07	2.55E+07	2.72E+07
C15	1.83E+00	2.38E+00	1.20E+00	4.20E+00	3.81E+00	2.34E+00	2.30E+07	1.77E+07	3.49E+07	1.00E+07	1.10E+07	1.79E+07
C20	1.71E+00	1.22E+00	8.58E-01	1.69E+00	2.32E+00	1.53E+00	2.46E+07	3.44E+07	4.90E+07	2.48E+07	1.81E+07	2.75E+07
CR2	2.07E+00	3.35E+00	2.99E+00	7.16E+00	6.01E+00	5.81E+00	2.02E+07	1.25E+07	1.40E+07	5.86E+06	6.98E+06	7.22E+06
CR3	6.06E+00	6.57E+00	4.68E+00	7.47E+00	8.52E+00	6.35E+00	6.94E+06	6.39E+06	8.97E+06	5.63E+06	4.93E+06	6.62E+06
CR4	9.29E-01	4.07E-01	2.70E-01	1.50E+00	1.49E+00	8.11E-01	4.52E+07	1.03E+08	1.56E+08	2.79E+07	2.82E+07	5.18E+07
CR5	2.09E+00	1.75E+00	1.08E+00	2.15E+00	2.43E+00	2.30E+00	2.01E+07	2.39E+07	3.90E+07	1.96E+07	1.73E+07	1.82E+07
E1	8.96E+00	4.23E+00	5.27E+00	8.21E+00	7.67E+00	7.05E+00	4.69E+06	9.94E+06	7.97E+06	5.12E+06	5.48E+06	5.96E+06
E2	1.59E+01	2.63E+01	2.08E+01	3.66E+01	3.04E+01	2.28E+01	2.64E+06	1.60E+06	2.02E+06	1.15E+06	1.38E+06	1.84E+06
E3	1.20E+00	9.54E-01	5.86E-01	1.84E+00	1.88E+00	1.57E+00	3.51E+07	4.40E+07	7.17E+07	2.28E+07	2.23E+07	2.68E+07
E4	3.84E+00	4.84E+00	3.50E+00	6.94E+00	8.01E+00	7.26E+00	1.09E+07	8.68E+06	1.20E+07	6.05E+06	5.24E+06	5.79E+06
E5	2.67E+00	3.08E+00	4.78E+00	6.07E+00	7.44E+00	6.78E+00	1.58E+07	1.36E+07	8.78E+06	6.92E+06	5.65E+06	6.19E+06
E6	8.23E+00	8.28E+00	5.68E+00	1.36E+01	1.45E+01	1.20E+01	5.10E+06	5.07E+06	7.39E+06	3.08E+06	2.90E+06	3.51E+06
E7	7.65E+01	7.65E+01	7.65E+01	1.09E+02	8.92E+01	8.13E+01	5.49E+05	5.49E+05	5.49E+05	3.87E+05	4.71E+05	5.16E+05
E8	4.25E+00	4.29E+00	4.62E+00	6.89E+00	8.57E+00	6.41E+00	9.87E+06	9.78E+06	9.10E+06	6.10E+06	4.90E+06	6.56E+06
E9	4.18E+00	4.56E+00	2.86E+00	4.73E+00	4.86E+00	5.30E+00	1.00E+07	9.21E+06	1.47E+07	8.89E+06	8.64E+06	7.93E+06
E10	6.83E+01	7.15E+01	7.15E+01	8.10E+01	7.78E+01	7.73E+01	6.15E+05	5.87E+05	5.87E+05	5.18E+05	5.40E+05	5.43E+05
E11	6.45E+00	6.13E+00	8.69E+00	1.53E+01	1.19E+01	1.48E+01	6.51E+06	6.85E+06	4.83E+06	2.75E+06	3.52E+06	2.85E+06
E12	4.44E+00	4.51E+00	2.80E+00	7.03E+00	6.51E+00	4.61E+00	9.46E+06	9.31E+06	1.50E+07	5.97E+06	6.45E+06	9.11E+06
F1	3.29E+00	3.12E+00	2.14E+00	4.88E+00	3.64E+00	3.11E+00	1.28E+07	1.35E+07	1.96E+07	8.61E+06	1.16E+07	1.35E+07
F2	4.48E+00	5.21E+00	6.03E+00	6.35E+00	6.44E+00	6.94E+00	9.38E+06	8.05E+06	6.97E+06	6.62E+06	6.53E+06	6.05E+06
F3	4.18E+00	4.56E+00	2.86E+00	4.73E+00	4.86E+00	5.30E+00	1.00E+07	9.21E+06	1.47E+07	8.89E+06	8.64E+06	7.93E+06
M1	1.60E+00	1.46E+00	1.36E+00	3.17E+00	2.83E+00	3.08E+00	2.62E+07	2.88E+07	3.09E+07	1.33E+07	1.48E+07	1.36E+07
M2	1.59E+00	1.45E+00	2.12E+00	3.60E+00	4.31E+00	4.49E+00	2.64E+07	2.90E+07	1.98E+07	1.17E+07	9.75E+06	9.36E+06
M3	4.36E+00	4.52E+00	4.51E+00	6.55E+00	4.98E+00	5.44E+00	9.63E+06	9.29E+06	9.31E+06	6.41E+06	8.43E+06	7.72E+06
M4a	1.65E+00	2.88E+00	2.87E+00	3.98E+00	4.56E+00	6.23E+00	2.54E+07	1.46E+07	1.46E+07	1.06E+07	9.20E+06	6.74E+06
M4b	1.93E+00	1.94E+00	1.23E+00	2.82E+00	3.43E+00	3.68E+00	2.18E+07	2.17E+07	3.42E+07	1.49E+07	1.22E+07	1.14E+07
M4c	2.93E+00	5.03E+00	4.08E+00	7.22E+00	7.30E+00	7.71E+00	1.43E+07	8.36E+06	1.03E+07	5.82E+06	5.75E+06	5.44E+06
M4d	4.48E+00	1.05E+01	1.49E+01	5.99E+00	6.73E+00	7.22E+00	9.38E+06	3.99E+06	2.82E+06	7.01E+06	6.24E+06	5.81E+06
M4e	3.10E+00	5.71E+00	3.93E+00	5.54E+00	6.52E+00	6.29E+00	1.35E+07	7.35E+06	1.07E+07	7.59E+06	6.44E+06	6.68E+06
M5	1.70E+00	1.21E+00	6.67E-01	2.49E+00	2.78E+00	2.40E+00	2.47E+07	3.47E+07	6.29E+07	1.69E+07	1.51E+07	1.75E+07
M6	1.88E+00	1.89E+00	1.29E+00	3.63E+00	3.68E+00	3.16E+00	2.24E+07	2.22E+07	3.26E+07	1.16E+07	1.14E+07	1.33E+07
M7	1.76E+00	1.55E+00	1.36E+00	3.17E+00	3.05E+00	3.64E+00	2.38E+07	2.72E+07	3.08E+07	1.33E+07	1.38E+07	1.15E+07
M8	2.21E+00	1.57E+00	1.19E+00	3.71E+00	3.19E+00	3.18E+00	1.90E+07	2.67E+07	3.54E+07	1.13E+07	1.32E+07	1.32E+07
M9	3.73E+00	4.37E+00	7.72E+00	6.73E+00	6.12E+00	6.09E+00	1.13E+07	9.62E+06	5.44E+06	6.24E+06	6.86E+06	6.89E+06
M10	2.33E+00	3.85E+00	2.21E+00	3.92E+00	3.89E+00	4.10E+00	1.80E+07	1.09E+07	1.90E+07	1.07E+07	1.08E+07	1.02E+07
M11	9.40E-01	4.23E-01	2.06E-01	9.58E-01	8.49E-01	6.30E-01	4.47E+07	9.94E+07	2.04E+08	4.38E+07	4.95E+07	6.66E+07
M12	1.57E+00	9.36E-01	4.70E-01	2.09E+00	2.04E+00	1.59E+00	2.67E+07	4.49E+07	8.94E+07	2.01E+07	2.06E+07	2.64E+07
M13	1.34E+00	1.11E+00	6.70E-01	1.99E+00	2.03E+00	1.83E+00	3.15E+07	3.77E+07	6.27E+07	2.11E+07	2.07E+07	2.29E+07
M14	1.35E+00	8.91E-01	7.30E-01	2.27E+00	2.02E+00	1.74E+00	3.12E+07	4.72E+07	5.75E+07	1.85E+07	2.08E+07	2.41E+07
M15	4.73E+00	5.63E+00	5.20E+00	1.05E+01	1.31E+01	7.64E+00	8.88E+06	7.46E+06	8.08E+06	3.98E+06	3.20E+06	5.49E+06
M16	3.41E+00	3.22E+00	2.58E+00	5.73E+00	5.47E+00	5.92E+00	1.23E+07	1.31E+07	1.63E+07	7.33E+06	7.68E+06	7.09E+06
M17	1.68E+00	1.86E+00	2.79E+00	5.02E+00	3.80E+00	4.34E+00	2.49E+07	2.25E+07	1.51E+07	8.37E+06	1.11E+07	9.68E+06
M18	2.11E+00	2.44E+00	2.58E+00	4.42E+00	3.65E+00	4.76E+00	1.99E+07	1.72E+07	1.63E+07	9.50E+06	1.15E+07	8.82E+06
M19	1.33E+00	1.98E+00	2.35E+00	3.12E+00	3.46E+00	3.26E+00	3.17E+07	2.12E+07	1.79E+07	1.34E+07	1.21E+07	1.29E+07
T1	2.72E+00	3.93E+00	2.39E+00	5.89E+00	5.57E+00	6.72E+00	1.54E+07	1.07E+07	1.75E+07	7.13E+06	7.54E+06	6.25E+06
T2	2.34E+00	1.97E+00	1.74E+00	1.20E+00	1.28E+00	1.38E+00	1.79E+07	2.13E+07	2.41E+07	3.49E+07	3.28E+07	3.04E+07

Note: The ‘Modelled Concentration’ refers to the results obtained at individual WSRs due to a hypothetical unit release of ‘N’ nos. of DCM rigs operating simultaneously (i.e. based on the modelled assumption of 1 kg/s from 42 DCM, ‘N’ = 42 kg/s or 42,000,000 mg/s). This hypothetical unit release is adopted for the purpose of deriving the equivalent dilution based on the calculation specified in Section 8.6.5.11, and does not represent actual contaminant release from DCM, hence the ‘Modelled Concentration’ does not directly reflect the concentration of individual contaminants at WSRs.

‘Nil’ means that the tracer was not detected at this location and layer.

Shaded cells represent the minimum dilution obtained for dry and wet season.

8.7.1.55 The maximum contaminant release rate was calculated by multiplying the maximum contaminant concentration with the pore water release rate (calculated to be 0.936 L/s). The extracted minimum dilution for dry and wet season (shown in Table 8.69) was then used to estimate the worst case contaminant concentration that may be observed at WSRs. The results are summarised in Table 8.70.

Table 8.70: Summary of the Dilution Potential for each Contaminant during the DCM Process

Parameter	Maximum Contaminant Release Rate ‘R_T’ (for a total of 42 nos. DCM operating simultaneously)	Rate Unit	Maximum Concentration at WSR		Concentration Unit	Relevant Criteria / Baseline*
			Wet Season	Dry Season
			(Minimum Unit Dilution ‘F’ = 2.14E+05 L/s)	(Minimum Unit Dilution ‘F’ = 3.87E+05 L/s)
Cd	8.531	(ug/s)	3.99E-05	2.20E-05	(ug/L)	0.2
Cr	52.875	(ug/s)	2.47E-04	1.37E-04	(ug/L)	15
Cu	177.651	(ug/s)	8.30E-04	4.59E-04	(ug/L)	3.1
Pb	46.074	(ug/s)	2.15E-04	1.19E-04	(ug/L)	7.2
Ni	227.538	(ug/s)	1.06E-03	5.88E-04	(ug/L)	8.2
Ag	48.000	(ug/s)	2.24E-04	1.24E-04	(ug/L)	1.9
Zn	225.808	(ug/s)	1.06E-03	5.83E-04	(ug/L)	10
Hg	3.931	(ug/s)	1.84E-05	1.02E-05	(ug/L)	0.05
As	2241.963	(ug/s)	1.05E-02	5.79E-03	(ug/L)	25
Tributyltin	0.511	(ug TBT/s)	2.39E-06	1.32E-06	(ug TBT/L)	0.0002
NH₃-N	1645.207	(mg/s)	7.69E-03	4.25E-03	(mg/L)	0.2
NO₂-N	0.432	(mg/s)	2.02E-06	1.12E-06	(mg/L)	0.12
NO₃-N	0.786	(mg/s)	3.67E-06	2.03E-06	(mg/L)	0.69
TKN	1800.490	(mg/s)	8.41E-03	4.65E-03	(mg/L)	0.51
Total P	40.609	(mg/s)	1.90E-04	1.05E-04	(mg/L)	0.08
Ortho-P	30.860	(mg/s)	1.44E-04	7.97E-05	(mg/L)	0.04
Total PCBs	7.076	(ug/s)	3.31E-05	1.83E-05	(mg/L)	0.03
Total PAHs	267.322	(ug/s)	1.25E-03	6.91E-04	(mg/L)	0.05

Note: The maximum contaminant release rate ‘R_T’ is calculated from the maximum release rate (shown in Table 8.38) multiplied by 42 (representing the maximum number of DCM rigs operating simultaneously).

* For metals and non-nutrients, the criteria are taken from Table 8.27. For nutrients, the criteria are taken from Table 8.28.

8.7.1.56 Based on the modelled dilutions, equivalent concentration contour plots (using NH₃-N as a reference) are shown in Appendix 8.12.

8.7.1.57 The findings from the tracer dilution model show that even with the assumption of 100 % release of pore water during the DCM process, the concentrations of all contaminants observed at the WSRs would still be well below the relevant criteria or baseline. It is thus anticipated that there will be no adverse water quality impact due to pore water release from the CMPs during ground improvement.

Release of Contaminants from Pore Water during Surcharge

8.7.1.58 Potential release of contaminants from pore water during the surcharge process was estimated according to the approximate volume of pore water that would be extruded. The calculations (refer to Section 8.6.5) suggest a unit release rate of 6.05x10^-6 m/s, evenly spread across the area of the seawall. Flow velocity results from the model indicate that the average flow speed of the bottom layer in the vicinity of the land formation is approx. 0.15 m/s. This implies an immediate average dilution potential of 24,500 times the pore water concentration (for any contaminant) at the seawall.

8.7.1.59 Table 8.71 compares the pore water concentrations (after dilution) with the relevant criteria / baseline.

Table 8.71: Summary of the Dilution Potential for each Contaminant during the Surcharge Process

Parameter	Unit	Maximum Weighted-Average Concentration	Maximum Weighted-Average Concentration (with 24,500x dilution)	Relevant Criteria / Baseline*	Maximum Weighted-Average Concentration (% of Criteria / Baseline)
Cd	(ug/L)	0.217	8.86E-06	0.2	0.0044 %
Cr	(ug/L)	1.345	5.49E-05	15	0.0004 %
Cu	(ug/L)	4.519	1.84E-04	3.1	0.0059 %
Pb	(ug/L)	1.172	4.78E-05	7.2	0.0007 %
Ni	(ug/L)	5.788	2.36E-04	8.2	0.0029 %
Ag	(ug/L)	1.221	4.98E-05	1.9	0.0026 %
Zn	(ug/L)	5.744	2.34E-04	10	0.0023 %
Hg	(ug/L)	0.1	4.08E-06	0.05	0.0082 %
As	(ug/L)	57.03	2.33E-03	25	0.0093 %
Tributyltin	(ug TBT/L)	0.013	5.31E-07	0.0002	0.2653 %
NH₃-N	(mg/L)	41.85	1.71E-03	0.2	0.8541 %
NO₂-N	(mg/L)	0.011	4.49E-07	0.12	0.0004 %
NO₃-N	(mg/L)	0.02	8.16E-07	0.69	0.0001 %
TKN	(mg/L)	45.8	1.87E-03	0.51	0.3665 %
Total P	(mg/L)	1.033	4.22E-05	0.08	0.0527 %
Ortho-P	(mg/L)	0.785	3.20E-05	0.04	0.0801 %
Total PCBs	(ug/L)	0.18	7.35E-06	0.03	0.0245 %
Total PAHs	(ug/L)	6.8	2.78E-04	0.05	0.5551 %

Note:

The maximum weighted-average concentration shown is for CMP and non-CMP areas (whichever is higher).

* For metals and non-nutrients, the criteria is taken from Table 8.27. For nutrients, the criteria is taken from Table 8.28.

8.7.1.60 As shown in Table 8.71, the dilution potential at the seawall will bring all contaminant concentrations from the pore water results well below existing baseline or criteria limits, and contributions to the existing baseline / criteria limits would be less than 1 %. Based on the above considerations, it is considered that the rate of pore water release during surcharge is insignificant compared to the typical flow speeds that can be expected in the vicinity of the land formation. Consequently, any contaminant release from the seawall will be rapidly diluted at source to below criteria limit / baseline levels, and the potential for background build-up of contaminants would similarly be insignificant. Therefore, no adverse water quality impact during the surcharge process is anticipated.

Modification of the Existing Seawall

8.7.1.61 The existing northern seawall at HKIA is a sloping seawall formed from rockfill and rock armour. During land formation, the existing rock armour would need to be removed, however, no dredging is required as the existing seawalls are already formed on previously dredged seabed (during construction of the original HKIA), thus the seabed beneath the existing seawalls do not require ground improvement or dredging prior to land formation. It is currently envisaged that derrick lighters will be deployed to remove the existing rock armour, which are placed above seabed level. After the rock armour has been removed, filters (comprising crushed rock and gravel) would be placed on the exposed face before marine filling activities commence as part of the land formation works. As rock armour are not associated with significant SS, and there will be no direct disturbance of the seabed, potential water quality impacts due to SS release from modification works at the existing seawall is anticipated to be minimal. Nevertheless, silt curtains will be deployed around the modification works and during marine filling activities to further minimise the potential for SS release.

Drilling Activities for the Submarine Aviation Fuel Pipelines

8.7.1.62 Diversion of the submarine fuel pipelines is proposed to be via horizontal directional drilling (HDD) method. This is a trenchless installation technique that involves the installation of pipes, conduits, and cables in a shallow arc using a land-based drilling rig and a steerable down hole system commonly used in drilling oil and gas wells. The HDD method will be deployed to install the pipelines directly from the existing airport island to the aviation fuel receiving facility (AFRF) at Sha Chau by underground drilling (mostly at sub-seabed rock level) without any disturbance to the seabed (shown in Drawing No. MCL/P132/EIA/8-007). The adoption of this method thus avoids potential water quality impacts associated with SS release that would otherwise arise under traditional construction methods (such as open trench excavation) for laying the submarine pipelines.

8.7.1.63 To prepare for construction using the HDD method, ground investigation (GI) works will first need to be conducted along the proposed alignment of the HDD to provide detailed geotechnical information for detailed design. The GI works will involve drilling a small number of boreholes (approximately four) into the seabed within the Sha Chau and Lung Kwu Chau Marine Park (the actual locations of these boreholes will be subject to detailed design requirements). While the Marine Park is a WSR, such GI works are not typically associated with adverse water quality impacts given that the diameter of each borehole is only approx. 0.2 m. Thus the area of seabed that is disturbed is very small and will not result in adverse SS release.

Landing Point at Sha Chau

8.7.1.64 The landing point for the submarine pipelines on Sha Chau will be inshore (on dry land) and adjacent to the AFRF. From there, the pipelines will route to the existing pipelines via the existing steel escape walkway linking the island and the AFRF. A temporary floating platform formed by two to three barges is proposed to be set up between the Sha Chau Island and the AFRF to provide a working platform for pipeline welding in order to minimise direct impacts to Sha Chau Island. As this construction method does not require any removal or disturbance of marine sediments from the seabed, no water quality impacts due to sediment loss are anticipated.

8.7.1.65 Potential water quality impacts arising from the activities at Sha Chau Island have been identified as a key concern, and measures have been incorporated into the design from the outset to minimise such impacts as far as possible. As part of the construction planning and design, only welding works will be carried out on the floating platform and bulk storage of chemicals is not required. The fuel tank associated with the self-propelled barges would be limited to approx. 15,000 liters. No dewatering will be required at the Sha Chau side of the pipeline, and water used for pipe cleaning will be introduced from the airport island side and will be discharged at the same side (not at Sha Chau Island). As this is an aviation fuel pipeline, no hydrotesting is required.

8.7.1.66 Based on the aforementioned arrangements, the risk of discharges from the drill holes to the surrounding area at Sha Chau would be minimal. As an added precaution, a containment pit would be constructed around the drill holes. Subject to detailed design, the containment pit may be formed from reinforced concrete with impermeable lining to prevent seepage (shown in Drawing No. MCL/P132/EIA/8-009, Figure A). Where the drill hole breaks through to the ground surface, a steel casing will be inserted and grouted into the hole, and the floor of the pit surrounding the casing will be concreted and sealed to secure the containment. Examples of similar containment pits applied in previous projects include the Ma Wan water pipeline between Sham Tseng and Ma Wan Island and the CLP cable project from Lantau to Ma Wan Island. An additional measure to be implemented during construction phase involves drilling both pilot holes first. Then one hole can act as a conduit for pumping any potential discharges (generated by drilling at the other pipeline hole) back to the airport island side, thereby further minimising the risk of accidental releases occurring at Sha Chau side (refer to diagram shown in Drawing No. MCL/P132/EIA/8-009, Figure B). Measures to prevent inflow of surface runoff into the pit include provision of a small concrete bund wall around the high side of the pit, and a temporary cover to prevent rain entry during rainstorm events (if necessary).

8.7.1.67 With the aforementioned design parameters in place, the possibility of water quality impacts at Sha Chau Island due to drilling, dewatering, storage of chemicals / fuels and pipe cleaning is considered to be extremely low.

Launching Site at Airport Island

8.7.1.68 At the airport island side, drilling is conducted via a closed-loop system, whereby the drilling fluid (anticipated to be mainly bentonite or Xanthan gum depending on contractor’s preferences) circulates around from the surface through the drill pipe back up the annulus to the surface, then through the cleaning system before recirculation back down the drill pipe again (see (Drawing No. MCL/P132/EIA/8-009, Figure C). Examples of similar closed-loop systems applied in previous projects include the Ma Wan water pipeline between Sham Tseng and Ma Wan Island and the CLP cable project from Lantau to Ma Wan Island and from Sham Tseng to Ma Wan Island.

8.7.1.69 The cleaning system comprises a mud mixing (shaker) system that separates the drill cuttings from the drilling fluid. The drill cuttings come out as dry solid (from sand size to <10mm chips depending on the rock formation grain size and the shape of the drill cutter) that is collected for either on-site reuse as trench backfill or land fill material, or for off-site disposal. At the end of the drilling process and during the pipe installation, the drilling fluid remaining inside the drill hole will be displaced and collected daily. The maximum daily volume generated is equivalent to the displacement volume and can be estimated by the following equation:

Volume = Cross Section Area (Cylinder) x Length

8.7.1.70 Assuming a pipe diameter of 0.6 m and a daily installation progress of approximately 240 m of pipe each day, the volume of waste drilling fluid that is displaced and removed from the drill hole is approximately 68 m³/day. According to the ProPECC Note PN 1/94, the drilling fluid should be recycled as far as possible and the discharge / disposal of the drilling fluid should obtain prior approval from the Director of Environmental Protection. Subject to detailed design, the wastewater will be treated on-site via chemical flocculation or similar treatment as necessary to meet the respective effluent standards as stipulated in the discharge license(s) under WPCO prior to discharge. With provision of on-site treatment of the wastewater, no water quality impact from the drilling process is anticipated.

8.7.1.71 Dewatering is not anticipated to be required as the drilling fluid has a higher density and head pressure in the hole which prevents the ingress of groundwater into the bore hole. Storage of chemicals will be limited at the site as the closed-loop drilling system means that only a small amount of drilling fluid needs to be added as the drilling progresses, and consequently, it is estimated that less than 3 tonnes may be stored on-site at any one time. Potential water quality impacts associated with accidental spillage or leakage of chemicals can be readily mitigated with the provision of appropriate chemical storage / containment areas. Wastewater generated from the pipe cleaning (approximately 1,500 m³ per pipe, calculated from assuming a pipe diameter of 0.6 m and a total pipe length of approximately 5,200 m) will be collected and treated before discharge in accordance with the discharge license(s) under WPCO. The contractor will obtain the required discharge license(s) under WPCO for discharges into the marine environment.

8.7.1.72 Based on the aforementioned construction process, potential water quality impacts arising from drilling, dewatering, storage of chemicals / fuels and pipe cleaning at the airport island site would be of low to negligible concern and can be readily mitigated with the implementation of appropriate mitigation measures.

Construction of New Stormwater Outfalls and Modifications to Existing Outfalls

8.7.1.73 New stormwater outfalls will be required in the new land formation areas to accommodate the expanded drainage, while existing outfalls located along the northern seawall of the existing airport island will need to be modified / extended. The discharge locations of the existing, modified and new outfalls are shown in Drawing No. MCL/P132/EIA/8-008.

Construction Activities associated with Modification of Existing Outfalls

8.7.1.74 For modification of the four existing outfalls (outfalls no. 3 to 6) that will be affected by the new land formation, it is proposed that these will be consolidated into two relocated outfalls which will be extended to the new edge of the land formation, as shown in Drawing No. MCL/P132/EIA/8-008. The main connection route of the combined and extended drainage culverts will be parallel to the existing northern seawall and the construction sequence will follow the land formation staging. The indicative construction sequence is shown in Appendix 8.13.

8.7.1.75 Based on the current scheme design, the stormwater culverts will be placed via open trench and traditional cast in-situ methods after completion of land formation. As these construction activities would be land-based, the potential water quality impact would be limited to construction site runoff and drainage. A temporary drainage channel will be provided between the existing seawall and the new land formation. This temporary channel will be formed as part of the filling activities for the land formation and will be retained until completion of the new diverted stormwater culverts. Runoff control measures such as bunding or silt fence would be implemented at both sides of the channel to prevent SS release via the temporary drainage channel. Good site practices such as proper collection, handling and disposal of construction solid waste, debris and refuse would also be implemented to avoid waste entering the temporary drainage channel.

8.7.1.76 Construction of the new relocated outfalls will take place at the same time as seawall construction. Based on the scheme design, the outfall structures will be placed as precast units with temporary bulkheads installed (to keep the tides from back flooding through the outfall structures). With the adoption of this construction method (which is not a significant source of SS), the potential for release of SS during construction of the relocated outfalls would be minimal.

8.7.1.77 Upon completion of the permanent culvert diversion, the temporary drainage channel will be filled and surcharged as part of the new land formation. As the temporary drainage channel is surrounded by the existing and new land formation, there would no adverse water quality impacts associated with filling the temporary channel.

Construction Activities for New Stormwater Outfalls

8.7.1.78 For the new stormwater culverts to be provisioned for the third runway expansion area, construction is envisaged to commence after completion of the land formation activities (due to the need for completion of surcharge to consolidate the fill materials beneath the new drainage culvert location), except for the outfalls, which will be constructed as part of the overall seawall construction. At the current stage of design, it is envisaged that the outfalls will be placed as precast units at an appropriate time during the seawall construction, and temporary bulkheads will be installed to allow the land formation works and the culvert extensions to be completed. The temporary bulkheads will be removed after the culvert extensions are completed and the drainage system is brought into service.

8.7.1.79 Construction of the culvert would be land-based, and the potential water quality impact would be limited to construction site runoff and drainage. For construction at the outfalls, dredging operation would not be anticipated and dredging of marine sediment would not be required. Given that both the placement of rock fill for the seawall and placement of precast units for the outfalls are not a significant source of SS, no adverse impact to WSRs are anticipated due to these construction activities.

Piling Activities for Construction of New Runway Approach Lights and HKIAAA Marker Beacons

New Runway Approach Lights

8.7.1.80 At the two ends of the new runway, approach lights are required. The approach light structures will consist of rows of sequence flashing lights (approx. 11 nos.) supported by piers extending approx. 300 m offshore along the centreline from the runway threshold. The initial scheme design for these approach lights are shown in Drawing No. MCL/P132/EIA/8-010.

8.7.1.81 At the western end of the runway, the approach lights will be constructed using pre-bored H piles. The piles will be bored to a depth of approx. 50-60 m below seabed level, and approx. 12 m³ of spoil will be excavated for each pile. The duration of piling activities for the complete set of approach lights is anticipated to be completed in several weeks. Based on these considerations, the anticipated SS release from construction of the approach lights are anticipated to be very small. Silt curtains will be deployed to completely enclose the pile installation works. By adopting this preventive measure, the impacts of the marine pile installation works on water quality are expected to be minimal.

8.7.1.82 At the eastern end of the new runway, the approach lights will need to be constructed over the CMPs. The proposed construction method is to first treat the CMP area surrounding each pile using DCM. Then the approach lights will be constructed using large diameter bored piles within the DCM treated CMPs, such that the excavated spoil will consist of cement mixed materials only. Steel casings will be driven through DCM area and excavation would be carried out by grabbing and chiselling within the steel casing.

8.7.1.83 The aforementioned method developed for installation of the eastern approach lights involves multiple levels of mitigation to minimise the potential for release of contaminated sediment. The sequence for implementation of the mitigation is outlined below:

1. Ground improvement using close-spaced DCM (with at least 80 % replacement ratio as shown in Drawing No. MCL/P132/EIA/8-010) to achieve UCS of 300 kPa will be completed prior to commencement of piling. Using the DCM method, including the application of a sand blanket, enables the in-situ stabilisation of CMP marine sediment and will reduce the potential for release of contaminated sediment or pore water. Bored piling works will be conducted after the DCM process has been confirmed to have fully stabilised the contaminated sediment in the CMP.

2. Following this, a silt curtain will be deployed around the area identified for piling activities.

3. Prior to initiating piling, steel casings will be driven through the DCM treated sediment using non-percussive piling methods. The casings will further act to contain disturbed sediment from entering the water column.

4. As an additional precautionary measure, material will then be extracted from the piles using a closed grab to reduce the potential for spillage into the surrounding marine environment as it is transferred to the barge. Therefore, the piling activities will be confined within the casings.

8.7.1.84 To reduce the transportation of waste materials off-site, priority will be given to the reuse of inert cement mixed materials on site, whereby the excavated cement mixed materials will be temporarily stockpiled on site for reuse as backfill material. Instructions and conditions for waste material reuse will be stipulated in the project’s Construction and Demolition Waste Management Plan to be developed by the contractor in the construction phase. There will be no discharge of the cement mixed materials into the marine environment. With the adoption of these measures, the potential for release of contaminated sediment or pore water from the CMPs due to marine pile installation works at the eastern approach lights would be reduced to insignificant levels, and adverse impacts associated with the marine piling works are not anticipated.

HKIAAA Marker Beacons

8.7.1.85 As part of the future requirements for operation of the new third runway, a new Hong Kong International Airport Approach Area would be designated at the marine waters surrounding the new runway strip. This future HKIAAA would be a restricted access area and markers positioned along the boundaries of this future HKIAAA would be required to ward vessels away from the perimeter of the HKIAAA. Based on discussions with Marine Department, it is expected that fixed beacons (instead of anchored buoys) would be required.

8.7.1.86 To demarcate the HKIAAA boundary, it is proposed to install nine beacons along the western side of the northern HKIAAA edge as shown in Drawing No. MCL/P132/EIA/8-011. Depending on the requirements by Marine Department, these beacons may need to be provided as fixed structures.

8.7.1.87 Based on initial scheme design, the beacons are anticipated to be single piled structures topped with steel light posts. Subject to Marine Department requirements, these beacons may be constructed using rock socketed H piles. The piles will be bored to a depth of approx. 50-60 m below seabed level, and approx. 20 m³ of spoil will be excavated for each pile. The duration of piling activities for the complete set of beacons is anticipated to be completed in several weeks. Based on these considerations, the anticipated SS release from construction of the HKIAAA beacons are anticipated to be very small. Silt curtains will be deployed to completely enclose the pile installation works. By adopting this preventive measure, the impacts of the marine pile installation works on water quality are expected to be minimal.

Construction Site Runoff and Drainage

8.7.1.88 After completion of land formation, potential water quality impacts may arise due to surface runoff containing high levels of SS and other contaminants. Potential sources of pollution from site drainage include:

¡ Erosion and runoff from the surcharge materials and other stockpiles, excavations and other exposed surfaces;

¡ Release of any concrete washings, bentonite slurries and other grouting materials with construction runoff and stormwater;

¡ Release of any fuel, oil, solvents and lubricants from construction vehicle / equipment maintenance or storage areas; and

¡ Wash water from dust suppression and wheel washing activities.

8.7.1.89 Runoff may enter the marine environment via temporary construction site drainage systems or via the permanent stormwater drainage system that will be provisioned for the third runway expansion area. However, sediment laden runoff can generally be controlled through implementation of good site management practices and provision of sediment removal facilities. This includes installation of runoff interception, collection and settlement facilities to treat or de-silt the runoff before discharge to stormwater drains. Discharge into public drainage systems or directly into the marine environment would require a discharge license to be issued by EPD under the WPCO. Each contractor for the project would be required to follow ProPECC Note PN 1/94 for control of construction site runoff and drainage, and be responsible for ensuring that any discharge from their construction site meets the requirements under the WPCO. With the implementation of appropriate mitigation measures specified in Section 8.8.1, adverse water quality impacts due to construction site runoff and drainage is not anticipated.

8.7.1.90 For potentially contaminated areas of the existing HKIA, runoff / groundwater discharge from excavations within these areas may affect the surrounding groundwater and seep into the marine environment, if uncontrolled. Based on the land contamination assessment (Chapter 11 refers), the presence of contaminated land, if any, is subject to further site investigation. In the event that contaminated groundwater is identified, this should be properly treated to comply with WPCO and the TM-DSS by either an onsite treatment facility or arranged for disposal to a licensed waste treatment facility. If onsite treatment is employed, the wastewater treatment unit shall comprise of a suitable treatment process taking into account the type of contaminants to be treated (e.g. oil interceptor or activated carbon). All treated effluent from the wastewater treatment unit shall meet the requirements as stated in the TM-DSS prior to discharge into the foul sewers or collected for proper off-site disposal. Direct discharge of contaminated groundwater would be prohibited. It should be noted that a Contamination Assessment Report (CAR) needs to be prepared after completion of the further site investigation and in the event of land contamination identified, a Remediation Action Plan (RAP) would be required (Chapter 11 refers). Details of the treatment requirements for contaminated soils and groundwater would be specified in the RAP.

Sewage Effluent from Construction Workforce and General Construction Activities

8.7.1.91 For marine vessel based activities, potential water quality impacts include sewage generated by the construction workforce and accidental spillage of chemicals / chemicals waste into the marine environment. The potential impact associated with sewage generated by the workforce can be readily controlled by provision of adequate sanitary facilities such as portable chemical toilets and proper control of wastewater from site facilities as outlined in ProPECC Note PN 1/94, while the storage and disposal of chemical waste will follow the guidelines stipulated in the Waste Disposal (Chemical Waste) (General) Regulations.

8.7.1.92 For land based activities (after completion of the land formation), the wastewater to generated from sewage effluent from construction workforce and general construction activities can similarly be readily controlled with the implementation of good site practices specified in ProPECC Note PN 1/94. Thus adverse water quality impact is anticipated to be minimal.

8.7.2 Operation Phase

Changes to Hydrodynamic Regime

8.7.2.1 Tidal flow simulations for the Year 2026 has been undertaken to identify the changes resulting from operation of the project (the ‘with project’ scenario) versus the base scenario in the absence of the project (the ‘without project’ scenario). A comparison between the two scenarios provides an indication of how the project will affect the future marine environment, taking into account the operation of concurrent projects. Plots comparing the with and without project scenarios are shown in Appendix 8.14.

8.7.2.2 For assessing the difference in tidal circulation on the regional scale, tidal discharges have been obtained from the computed velocities across selected cross-sections representing main channels. These cross-sections are shown in Drawing No. MCL/P132/EIA/8-012.

8.7.2.3 A summary of the tidal discharges and percentages of change at key areas are presented in Table 8.72 below for residual, peak flood, peak ebb for both the wet and dry seasons.

Table 8.72 Wet and Dry Season Tidal Discharges (m³/s)

Section	Season	Dry		Wet
Section	Flow Direction	2026 Base Scenario	2026 Project Scenario	2026 Base Scenario	2026 Project Scenario
Sha Chau	Flood	36,700	37,777	33,258	34,409
	% change		2.9 %		3.5 %
	Ebb	33,468	34,032	38,407	38,718
	% change		1.7 %		0.8 %
	Residual (+ve flood)	1,188	1,026	-987	-1,214
	% change		-13.6 %		23.0 %
East of Airport Channel	Flood	1,106	881	800	478
	% change		-20.3 %		-40.3 %
	Ebb	1,294	1,178	1,500	1,373
	% change		-8.9 %		-8.5 %
	Residual (+ve flood)	29	13	-96	-107
	% change		-55.0 %		11.7 %
Urmston Road	Flood	48,567	48,852	45,345	45,538
	% change		0.6 %		0.4 %
	Ebb	47,791	47,377	53,205	52,721
	% change		-0.9 %		-0.9 %
	Residual (+ve flood)	1,179	1,018	-995	-1,222
	% change		-13.7 %		22.8 %
Kap Shui Mun	Flood	17,690	17,800	17,214	17,216
	% change		0.6 %		0.0 %
	Ebb	14,626	14,752	16,278	16,146
	% change		0.9 %		-0.8 %
	Residual (+ve flood)	1,019	977	281	216
	% change		-4.1 %		-23.1 %
Ma Wan Channel	Flood	31,111	31,208	28,815	28,891
	% change		0.3 %		0.3 %
	Ebb	33,489	32,959	36,307	36,011
	% change		-1.6 %		-0.8 %
	Residual (+ve flood)	589	488	-368	-512
	% change		-17.1 %		39.1 %
Rambler Channel	Flood	2,073	2,084	1,742	1,766
	% change		0.5 %		1.4 %
	Ebb	3,236	3,227	3,894	3,745
	% change		-0.3 %		-3.8 %
	Residual (+ve flood)	-428	-447	-908	-926
	% change		4.4 %		2.0 %

8.7.2.4 Based on Table 8.72, it can be generally seen that the changes in peak tidal discharges, including both increases and decreases, are relatively small after implementation of the project as compared to the base scenario for all locations except the East of Airport Channel.

8.7.2.5 To the west of the airport island (i.e. flow across Sha Chau) in wet and dry seasons, the peak flood and ebb flow are found to increase by 3.5 % (wet) to 2.9 % (dry) and by 0.8 % (wet) to 1.7 % (dry), and the residual flows are increased in the wet season by 23.0%, but reduced in dry season by -13.6 %. This suggests that the project generally induces a small increase in peak discharges and a tendency towards residual flows in the ebb direction (or a reduction in the residual flows in the flood direction), but compared to the high flow volumes experienced across this area, these changes in peak and residual discharge are unlikely to significantly affect the existing flow regime across this area.

8.7.2.6 Tidal discharges across other major channels in the North Lantau area (i.e. Urmston Road, Kap Shui Mun, Ma Wan Channel and Rambler Channel) show similarly limited changes in peak flood and ebb flow, though there is a similar small tendency towards increasing residual flows in the ebb direction or a reduction in the residual flows in the flood direction. While the percentage residual flow tends to be quite high at some locations (e.g. Ma Wan Channel), actual residual flow differences between the base scenario and the project scenario are similar to that of other locations during both wet and dry season. These residual flow changes are nevertheless unlikely to be significant when considered in the context of the much larger tidal flow regime occurring across these sections.

8.7.2.7 More significant changes are identified for the flow through the East of Airport Channel. In dry season, the peak flood, ebb flow and residual flow through the East of Airport Channel are shown to reduce by 20.3 % and 8.9 % respectively with an fairly large reduction of 55.0 % in residual flow (from 29 m³/s to 13 m³/s); while in wet season, the peak flood and ebb flow decrease by 40.3 % and 8.5 % respectively with an increase in the residual ebb flow by 11.7 %. The high percentage difference in residual flows during dry season is largely due to the very low residual flow volumes that occur in this area and does not represent significant changes in the residual flow (in absolute terms), however, the general reductions in peak flow in both directions during both wet and dry season may indicate a tendency towards reduced flushing and assimilative capacity of the water body. However, the water quality results do not appear to show significant deteriorations in water quality in this area despite the reduced flows (refer to the results for DO, BOD₅, TIN, NH₃ and SS shown in Appendix 8.15). Thus it is not anticipated that the flow reductions will adversely affect water quality in this area.

8.7.2.8 For assessment of local effects due to the project, flow velocities at individual WSR locations were extracted and compared. Appendix 8.14 (Table 1) compares the maximum, minimum and average surface velocities for the with and without project scenarios. The results show generally minimal changes in flow velocities at most WSRs (<0.1 m/s), which suggests that the project would not induce significant changes to the hydrodynamic regime at most locations. Areas showing more significant changes in peak velocity (e.g. >0.2 m/s) are generally areas immediately surrounding the project (e.g. the area immediately north and east of the airport and the embayed areas to the west of the airport).

8.7.2.9 At the area immediately west of the existing airport island, the current speed and flow vector plots show that the new third runway land formation generally creates an area of reduced flows (covering the southern part of the new third runway’s west tip), which becomes more ‘sheltered’ from the dominant Pearl River Delta tidal regime (see Appendix 8.14 Figures 1 to 12 and 25 to 36). As a result of the reduced flows, there may be some sedimentation in this area, but there does not appear to be adverse deteriorations in water quality in this area (based on the water quality results shown in Appendix 8.15, which are discussed in the following sub-sections of this chapter).

8.7.2.10 To the immediate north of the project, reductions in peak velocity are also predicted with implementation of the project (see Appendix 8.14 Figures 1 to 12). The effect is more pronounced during the wet season, when flow velocities in the North Lantau area are generally faster due to the additional freshwater flows from the Pearl River Delta estuaries. With the project in place, reductions in flow velocity to the north of the project would be expected, though these reductions are not anticipated to lead to water quality issues as the peak flow velocity remains relatively high despite the reductions associated with the project.

8.7.2.11 To the immediate east of the project, WSR C8 shows more notable changes in peak flow velocity, whereby the velocity is predicted to increase by up to 0.27 m/s (see Appendix 8.14 Table 1). However, this predicted increase in peak velocity is unlikely to lead to erosion issues given the generally low flow velocities associated with this partially embayed area.

Temperature

8.7.2.12 Appendix 8.15 (Table 1) compares the monthly depth-averaged temperature between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 1 to 24). The findings show the temperature differences to be within the WQO criteria at all WSRs. Changes in monthly depth-averaged temperature at ecological and fisheries sensitive receivers due to implementation of the project are very small. With the dominant Pearl River Delta discharges affecting the study area, natural fluctuations in temperature within the North Western WCZ is high (between 12 ^oC and 31.3 ^oC as shown in Table 8.9). Thus ecological and fisheries sensitive receivers located in this area would already be tolerant to such variations, and it is not anticipated that the small changes arising from the new land formation associated with the project will adversely affect ecological and fisheries sensitive receivers in the study area.

Salinity

8.7.2.13 Appendix 8.15 (Table 2) compares the monthly averaged salinity between the with and without project scenarios at Year 2026 at all WSRs. The findings show the salinity differences to be within the WQO criteria at all WSRs. Relatively larger salinity differences are noted at a number of WSRs between July and August, which show differences of up to ±7 %. This is nevertheless well within the seasonal variations associated with the Pearl River Delta area (refer to salinity results from EPD’s baseline monitoring stations within the study area shown in Table 8.9 to Table 8.11), and is unlikely to adversely affect ecological and fisheries sensitive receivers.

8.7.2.14 At the embayed area to the west of the airport (observation point M9), average salinities increase overall in the with project scenario. This is primarily due to the ‘sheltering’ effect of the new land formation. As shown in the contour plots in Appendix 8.15 (Figure 25 to 48), the presence of the third runway creates a change in the local flow regime in the immediate vicinity of the project such that the freshwater influences of the Pearl River Delta to the waters immediately west of the airport are reduced. Consequently, salinity levels at the western edge of the airport (and south of the third runway) remains comparatively higher than other areas which are not sheltered by the project. Relatively large differences are also predicted immediately north of the project (e.g. at observation point M4d representing the south western corner of the Sha Chau and Lung Kwu Chau Marine Park), whereby salinity reductions occur during the summer months as a result of a general accumulation of freshwater in the area immediately north of the project. With the already high background salinity variations experienced in the North Lantau area, ecological and fisheries sensitive receivers in this area would already be highly tolerant of the large variations in salinity. Given that the modelled salinities (11.4 – 30.0 ppt at M9 and 9.4 – 27.7 ppt at M4d) remains within the long term baseline salinity range (between 3.3 – 37.0 ppt at EPD’s monitoring stations within the North Western WCZ shown in Table 8.9), the salinity differences immediately surrounding the project area during wet season is unlikely to have adverse impacts on ecological and fisheries sensitive receivers.

Dissolved Oxygen (DO)

8.7.2.15 Appendix 8.15 (Table 3-a and 3-b) compares the monthly depth-averaged DO level and the near-bottom DO levels between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 49 to 60). The WQO for DO is specified as a minimum concentration for 90 % of the sampling occasions within a year. Assuming that each monthly-averaged result represents one sampling occasion, the WQO criteria would need to be met for at least 11 out of 12 months in order to demonstrate no exceedance. Based on this approach, the findings show that the monthly depth-averaged DO levels and the near-bottom DO levels at all WSRs would be compliant with the WQO criteria.

8.7.2.16 Notwithstanding the findings, low DO levels are predicted at some observation points located within the Inner Deep Bay area (e.g. M15 and M16 shown in Appendix 8.15 (Table 3-a), which shows depth-averaged DO levels ranging between 1.2 mg/L and 4.9 mg/L). This occurs for both with and without project scenarios. Long term baseline DO levels from EPD’s actual monitoring stations DM1 and DM2 show a DO range of between 0.1 mg/L and 16.1 mg/L. The Deep Bay area is known for its nutrient-rich discharges and low levels of DO, whereby depth-averaged DO levels at EPD’s Inner Deep Bay stations (DM1, and to a lesser extent DM2) have been below the DO criteria for at least the past 10 years (with the exception of the 2012 results for DM2)⁷. Given these findings, the low DO levels predicted at both M15 and M16 are not considered to be attributable to implementation of the project.

7 EPD’s Annual Report on Marine Water Quality in Hong Kong in 2012

Biological Oxygen Demand (BOD₅)

8.7.2.17 Appendix 8.15 (Table 4) compares the monthly averaged BOD₅ between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 61 to 72). For WSD seawater intakes, the findings show that the BOD₅ levels are in compliance at all WSRs representing WSD seawater intakes. For other WSRs, there is no WQO for BOD₅, but comparison between the results for with and without project scenarios show that there is very little difference due to implementation of the project (see Table 8.73). Thus no adverse impact is anticipated due to implementation of the project.

Table 8.73: Comparison between Predicted BOD₅ Levels at WSRs

BOD₅ (mg/L)

North Western WCZ

Western WCZ

Deep Bay WCZ

Predicted monthly depth-averaged range at WSRs (without project)

0.7 – 6.3

0.2 – 1.4

1.5 – 11.7

Predicted monthly depth-averaged range at WSRs (with project)

0.7 – 6.5

0.2 – 1.4

1.6 – 11.9

Suspended Solids (SS)

8.7.2.18 Appendix 8.15 (Table 5) compares the monthly depth-averaged SS between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 73 to 84). The findings show the SS differences to be within the WQO criteria at all WSRs, except at the WSD seawater intakes.

8.7.2.19 At the WSD seawater intakes (e.g. C3, C5 and C6), the predicted SS levels for both the with and without project scenarios show exceedance of the WSD criteria (<10 mg/L) (see Appendix 8.15). A comparison between the predicted SS levels for these three WSRs is shown in Table 8.74. Time history plots are shown in Appendix 8.15 (Figure 122 to 124).

Table 8.74: Comparison between Predicted SS Levels at WSRs and the Long Term Baseline Range from EPD’s Monitoring Stations

SS (mg/L)	C3	C5	C6
Long term baseline range (depth-averaged)	NM3 1.7 – 90.3 (mean 10.1)	NM2 1.0 – 51.5 (mean 8.2)	NM2 1.0 – 51.5 (mean 8.2)
Predicted monthly depth-averaged range at WSRs (without project)	8.2 – 11.8	8.7 – 13.1	9.4 – 14.8
Predicted monthly depth-averaged range at WSRs (with project)	8.3 – 12.0	8.8 – 13.2	9.6 – 14.9

8.7.2.20 The predicted results show that there is generally very little difference between the with and without project scenarios, while all three WSRs show a very small increase compared to the without project scenario (up to 0.2 mg/L which is equivalent to up to 3.4 % increase). Taking into account the long term monitoring data at the nearest EPD monitoring stations (NM2 and NM3), mean depth-averaged SS levels are already close to or exceeding the WSD criteria. Thus the exceedance in SS at the WSD seawater intakes are mainly associated with existing background levels and is not considered to be adversely affected by implementation of the project.

Total Inorganic Nitrogen (TIN)

8.7.2.21 Appendix 8.15 (Table 6) compares the monthly and annual TIN levels between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 85 to 96). The results show that monthly exceedances occur at the majority of WSRs for both the with and without project scenarios, particularly during the summer months. However, annual mean TIN levels at the majority of WSRs will comply with the WQO criteria. Exceedances of the annual mean depth-averaged TIN criteria for the with project scenario occurs at WSRs C1, C9, and E1. These WSRs are all located in the Deep Bay WCZ, where exceedances are predicted in both the with and without project scenarios (see Appendix 8.15). The results of the WSRs showing exceedances are shown in Table 8.75. Time history plots are shown in Appendix 8.15 (Figure 125 to 127).

Table 8.75: Comparison between Predicted TIN Levels at WSRs and the Long Term Baseline Range from EPD’s Monitoring Stations

TIN (mg/L)	C1	C9	E1
Long term baseline range (depth-averaged)	DM5 0.10 – 2.16 (mean 0.72)	DM4 0.10 – 2.85 (mean 0.95)	DM3 0.01 – 6.33 (mean 1.43)
Predicted depth average range at WSRs (without project)	0.48 – 0.77 (monthly) 0.61 (annual average)	0.64 – 1.38 (monthly) 1.03 (annual average)	0.72 – 5.30 (monthly) 3.57 (annual average)
Predicted depth average range at WSRs (with project)	0.48 – 0.77 (monthly) 0.62 (annual average)	0.62 – 1.43 (monthly) 1.05 (annual average)	0.66 – 5.39 (monthly) 3.61 (annual average)

8.7.2.22 As shown in Table 8.75, the predicted TIN ranges do not differ much between the with and without project scenarios, while the nearest EPD monitoring stations within the Deep Bay WCZ show a long term depth-averaged range of between 0.01 – 6.33 mg/L for TIN. As reported in EPD’s Annual Marine Water Quality Report for 2012, none of the monitoring stations in the Deep Bay WCZ were able to meet the TIN objective in 2012. As the pollution loading inventory has incorporated the high pollution loadings from the Deep Bay / Shenzhen River area, exceedances predicted at WSRs located in the Deep Bay area for the with and without project scenarios are thus not unexpected. Given that the without project scenario already shows exceedance of the WQO criteria, and predicted TIN levels in the with project scenario remains within the long term baseline range, the increased TIN resulting from implementation of the project is not anticipated to adversely affect the WSRs in the Deep Bay area.

Unionised Ammonia (NH₃)

8.7.2.23 Appendix 8.15 (Table 7) compares the monthly and annual NH₃ levels between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 97 to 108). The results show that monthly exceedances occur at some of the WSRs for both the with and without project scenarios. However, annual mean NH₃ levels at the majority of WSRs will comply with the WQO criteria. Exceedances of the annual mean depth-averaged NH₃ criteria for the with project scenario occurs at WSRs C9 and E1. These WSRs are located in the Deep Bay WCZ, and exceedances occur in both the with and without project scenarios (see Appendix 8.15). The results of the WSRs showing exceedances are shown in Table 8.76. Time history plots are shown in Appendix 8.15 (Figure 128 to 129).

Table 8.76: Comparison between Predicted NH₃ Levels at WSRs and the Long Term Baseline Range from EPD’s Monitoring Stations

NH₃ (mg/L)	C9	E1
Long term baseline range (depth-averaged)	DM4 0.001 – 0.068 (mean 0.010)	DM3 0.001 – 0.553 (mean 0.020)
Predicted depth average range at WSRs (without project)	0.010 – 0.035 (monthly) 0.025 (annual average)	0.016 – 0.195 (monthly) 0.133 (annual average)
Predicted depth average range at WSRs (with project)	0.009 – 0.037 (monthly) 0.026 (annual average)	0.015 – 0.198 (monthly) 0.134 (annual average)

8.7.2.24 As shown in Table 8.76, the without project scenario already shows exceedance of the WQO criteria, while the modelled values for both with and without project scenarios are well within the long term baseline variation experienced at EPD’s monitoring stations in Deep Bay. Given that the difference in annual average NH₃ between the with and without project scenarios is only 0.001 mg/L at both C9 and E1 (representing a 4.0 % and 0.7 % difference respectively), the change in NH₃ due to implementation of the project is not considered to be significant, and WSRs in the Deep Bay area are unlikely to be adversely affected by this change.

E. coli

8.7.2.25 Appendix 8.15 (Table 8) compares the monthly averaged E. coli levels between the with and without project scenarios at Year 2026 at all WSRs. Contour plots are shown in Appendix 8.15 (Figure 109 to 120). The findings show that there are no counts of E. coli at any of the WSRs or observation points, i.e. all modelled E. coli levels are <1 cfu/100 ml. Thus the E. coli levels are within the WQO criteria at all WSRs, and no adverse impacts are anticipated due to implementation of the project.

Sedimentation

8.7.2.26 Appendix 8.15 (Table 9) shows the predicted annual sedimentation (in g/m²) for the with and without project scenarios at Year 2026 at WSRs representing ecological sensitive receivers. Contour plot is shown in Appendix 8.15 (Figure 121). Assuming a density of 750 kg/m³, a sedimentation rate in units of mm is also derived. The findings show that the majority of locations would experience no appreciable change in sedimentation rates after implementation of the project. The only notable differences occur at WSR F1, whereby sedimentation is predicted to increase after implementation of the project, though the rate of sedimentation remains very low (on the order of <0.01 mm per year). The cultured fish are also generally confined within the surface to middle layer of the water column and is unlikely to be affected by change in sedimentation pattern. This difference is thus considered to be insignificant and is unlikely to lead to any adverse impacts on WSRs.

Spent Cooling Discharge

Temperature

8.7.2.27 For assessment of impacts due to the spent cooling discharges, the maximum, minimum and average surface temperature for the with and without project scenarios (which takes into account both the change in ambient temperature regime due to the new land formation as well as the additional thermal discharges associated with the 3RS) was extracted from the hydrodynamic model and the difference between the scenarios was compared against the WQO criteria (presented in Appendix 8.16 (Table 1 and Figures 1 to 18)). The findings showed similar non-exceedances during both wet and dry season as identified in the monthly depth-averaged results presented in Appendix 8.15 (Table 1). As shown in Appendix 8.15 (Figures 13 to 24), wet season temperature differences are primarily due to changes in the background temperature regime, whereby the presence of the new land formation affects the local mixing of the warmer Pearl River Delta discharges with the cooler waters from other parts of Hong Kong. As a result, temperature elevations due to the spent cooling discharges may be counteracted by the more dominant changes in ambient temperature pattern around the new land formation area. Nevertheless, the findings show the temperature differences to be within the WQO criteria at all WSRs, which confirms that there are no impacts due to temperature associated with the new land formation and the spent cooling discharges from the project.

Residual Chlorine

8.7.2.28 Appendix 8.16 (Table 2) shows the predicted maximum depth-averaged residual chlorine levels at individual WSRs. At WSRs representing ecological or fisheries sensitive receivers, the findings show that there is limited to no detection of residual chlorine at these WSRs, and no exceedances are predicted. Thus no areas of ecological or fisheries importance will be affected by residual chlorine release. The only location with notably elevated residual chlorine levels is at WSR C7a, however the criterion is not applicable to this WSR as the level of residual chlorine would have no adverse impact on the operation of the cooling water intake.

8.7.2.29 The result plots of the worst case periods showing the extent of the mixing zone⁸ are shown in Appendix 8.16 (Figures 19 to 26). The spent cooling discharges associated with the project are located at outfall No.7 and No.14, while discharge from outfall No.8 is due to the concurrent NCD project which is not part of 3RS. The locations of the spent cooling discharge outfalls are shown in Drawing No. MCL/P132/EIA/8-008.

8 This refers to the zone of initial dilution around the discharge point whereby the concentration of the contaminant exceeds the relevant criteria. It should be noted that the EIAO-TM recognises that water quality criteria may not be achievable at the point of discharge as there are areas which are subjected to greater impacts where the initial dilution of the discharge takes place. In general, the criteria for acceptance of the mixing zone are that it must not impair the integrity of the water body as a whole and must not damage the ecosystem.

8.7.2.30 At outfall No.7, under the worst case tidal period, the maximum extent of the mixing zone for residual chlorine release is approximately 260 m (as shown in Appendix 8.16 (Figure 21)). However, this occurs only at certain tidal conditions (e.g. during neap high tide in wet season). During other tidal conditions, the mixing zone is notably reduced or not present. Outfall No. 7 is located in a relatively sheltered area compared to other parts of the seawall along the northeastern side of the airport expansion, hence current speeds are generally low and dispersion is reduced. The mixing zone is thus largely confined to the immediate area around the discharge point. As shown in Appendix 8.16 (Figure 19 to 22), during wet season when current speeds are higher, the mixing zone is flushed during each low tide event, such that there is only intermittent accumulation of residual chlorine at the location. During dry season (shown in Appendix 8.16 (Figure 23 to 26)) when conditions are more stable, the mixing zone appears to remain present at all tidal conditions. However, it should be noted that during dry season, cooling demand from the seawater pumping house would be reduced, thus the maximum mixing zone associated with peak discharge during dry season (as shown in Appendix 8.16 (Figure 23 to 26)) represents a worst case situation that is unlikely to occur for long periods of time.

8.7.2.31 At outfall No.14, under the worst case tidal period, the maximum extent of the mixing zone for residual chlorine release is approximately 550 m (as shown in Appendix 8.16 (Figure 20)). However, this occurs only at certain tidal conditions (e.g. during spring low tide in wet season). During other tidal conditions, the mixing zone is notably reduced or not present. Outfall No. 14 is located in a more tidally-exposed area, hence as shown in Appendix 8.16 (Figures 19 to 26), the mixing zone can stretch for longer distances and shift with the tides, but will diminish quickly due to the high flushing potential associated with the stronger currents. Evidence of this can be seen in Appendix 8.16 (Figure 23 to 26), whereby compared to the mixing zone associated with outfall No.7 (which remains largely the same both at surface and mid depth), the mixing zone associated with outfall No.14 shows a much smaller mixing zone at the surface compared to mid depth. The outfall is located near mid depth, hence the much smaller surface mixing zone suggests that the mixing zone associated with outfall No.14 is able to disperse quickly and thus is unlikely to linger for long periods at the same location.

8.7.2.32 Discharge from outfall No. 8 is due to the concurrent NCD project which is not part of 3RS, hence the mixing zone associated with this outfall (which is particularly evident in Appendix 8.16 (Figures 20 and 24)) is due to the concurrent NCD project only and is not related to the 3RS project. The result plots show that there is no merging of the mixing zone from the NCD discharge outfall No.8 and that of the project outfall No.7 and No.14, hence there is no accumulated impact due to combined residual chlorine release. Similar to outfall No.14, the maximum extent of the mixing zone associated with outfall No.8 occurs during spring low tide (shown in Appendix 8.16 (Figure 20)), but is notably reduced or not present during other tidal conditions. During both wet and dry seasons, the mixing zone is generally flushed during each high tide event, such that there is only intermittent occurrence of residual chlorine at the location. Generally, the findings show that the mixing zone shifts constantly with the tides and is unlikely to linger for long periods at the same location. It should be noted that the discharge assumptions adopted for the concurrent NCD project is still subject to further detailed design, thus the discharge quantities and discharge point may change.

8.7.2.33 Potential impacts to marine ecology including fishes and marine mammals due to the presence of these mixing zones have been reviewed. In terms of location and spread, none of the mixing zones are located in areas of ecological or fisheries importance, and while a mixing zone is present for most tidal periods (due to the 24 hour release), the precise location and size of the mixing zone will fluctuate with the tide, hence the effects are intermittent. In addition, the adopted criteria of 0.0075 mg/L is very conservative compared to EPD’s No Observable Effect Concentration (NOEC) value of 0.02 mg/L for residual chlorine. Based on these findings, it is concluded that the localised and generally intermittent presence of these mixing zones are unlikely to have adverse impacts on marine ecology. The presence of the mixing zones would thus not have adverse effects on the ecosystem and water body as a whole.

8.7.2.34 It should be noted that the model assumes a worst case release of 0.5 mg/L of residual chlorine under peak discharge occurring 24 hours a day, seven days a week, for both wet and dry season. In reality, spent cooling discharges from the seawater pumping house would vary according to daily and seasonal demand (i.e. peak demand would only occur during peak times each day, and during the summertime), while according to historical records of residual chlorine concentrations, the average residual chlorine concentration is 0.3 mg/L (see Table 8.40). The model result thus represents a very worst case situation.

Biocide

8.7.2.35 Appendix 8.16 (Figure 27) shows the predicted maximum depth-averaged residual amine levels at the nearest WSR (taken as C7a) based on the 24 hour release pre-run, which has been used to determine the worst case tidal period for biocide release.

8.7.2.36 Based on the worst case period as identified from the 24 hour pre-run, the results of the 1 hour per week release are shown in Appendix 8.16 (Table 3 and Figures 28 to 33). The findings show that residual amine levels were predicted to be below criteria levels at all WSRs representing ecological and fisheries sensitive receivers. The maximum mixing zone radius for residual amine release from spent cooling discharges from outfall No.7 and No.14 is approximately 700 m and 140 m respectively. However, this occurs for only a short time after the biocide release. During wet season, the mixing zone is mainly restricted to the near surface water depth and any mixing zone in the mid-depth has fully dispersed by approximately 3 hours after release. During dry season, the mixing zone remains largely confined to the immediate area of the outfalls and is largely dispersed by 2.5 hours after release. Thus the intermittent presence of the residual amine mixing zone is unlikely to have adverse effects on the ecosystem and water body as a whole.

8.7.2.37 It should be noted that while elevated amine level is predicted at C7a, which is the cooling water intake at HKIA, the level of residual amine would have no adverse impact on the operation of the cooling water intake and so the criterion is not applicable to this WSR.

Summary of Quantitative Water Quality Assessment Results

8.7.2.38 The findings of the predicted water quality for the with and without project scenarios (shown in Appendix 8.15 and Appendix 8.16) and the evaluations as discussed in the preceding sections have shown that overall, implementation of the project will not result in significant changes to the water quality of the study area. Based on these findings, it can be concluded that adverse water quality impacts (e.g. impacts associated with DO, BOD₅, SS, TIN, NH₃, E. coli, sedimentation and spent cooling water discharge) as a result of implementation of the project are not predicted.

Sewage Discharge

8.7.2.39 Sewage effluent would be generated from a range of activities at HKIA including from the airport-based workforce, passengers, staff and other visitors using airport facilities, food and beverage outlets, offices and hotels, as well as from certain maintenance activities in HKIA. Some of the wastewater generated will be reused on site following treatment at the greywater treatment facilities. During full operation phase, foul sewage would be disposed to the public sewerage system and transferred to the Siu Ho Wan Sewage Treatment Works (STW) for treatment. As such, there will be no sewage outfall at HKIA and any surplus discharge of treated greywater will divert to the foul sewer as is currently the case at HKIA.

8.7.2.40 Due to the scale of the project, there will be an interim operation phase after completion of the land formation whereby the existing South Runway and the new third runway will be in operation while the existing North Runway will be closed for construction (Phase 2 operation as described in Section 4.3.1). During this period, only a small number of airport facilities on the new land formation (such as the new airside fire station and the new air traffic control tower) will be in operation, while the new sewerage system for the third runway facilities would still be under construction. Consequently, sewage generated by these new facilities during Phase 2 operation will be temporarily collected by a pump sump. The estimated sewage load from these new facilities is approximately 130 m³/day and this will be collected at least seven times daily by truck to Siu Ho Wan STW. Upon completion of the new sewerage system for the third runway area, all sewage loads generated within the HKIA will be collected and conveyed via the sewerage network to the Siu Ho Wan STW.

8.7.2.41 The impact of the additional sewage load to the Siu Ho Wan STW was assessed in Chapter 9 of this report. The findings from the assessment showed that the Siu Ho Wan STW has adequate treatment capacity to handle the additional sewage loads (daily flow in m³/day) from the project, as well as concurrent projects in North Lantau expected to be operational up to the Year 2038, though the existing design peak flow (in L/s) would be reached in Year 2026. As the water quality model has taken the daily flow design capacity of the STW for calculating the pollution loads to the receiving waters in Year 2026, the additional sewage loading due to the project has been adequately captured in the water quality assessment.

8.7.2.42 A new sewage pumping station will be needed to serve the additional sewage capacity requirements of the third runway expansion, however, the design of the new sewage pumping station will not include an emergency sewage overflow system, hence there will be no sewage effluent discharge during storm event or emergency discharge under any circumstances. The sewage pumping station will be designed with spare capacity, a generator for backup power supply, and at least one standby pump to minimise the risk of service disruption due to pump failure. In the event of total failure, the contingency will be to transport the sewage effluent by truck to Siu Ho Wan STW. Based on these provisions, there will be no discharge of sewage effluent from HKIA into the marine environment, and no adverse water quality impact due to sewage disposal is anticipated.

Reuse of Treated Greywater

8.7.2.43 Greywater reuse is one of the water conservation measures currently adopted at the existing HKIA. The existing greywater treatment facility has a capacity of 6,000 m³/day and mainly collects greywater from the passenger terminal buildings and catering facilities for reuse as irrigation water for the landscaped areas. The capacity of this greywater treatment facility would not be sufficient to handle the additional greywater generated from the third runway facilities, hence an additional greywater treatment facility is proposed to be located at the airport expansion area to serve the new third runway facilities.

8.7.2.44 Based on the current scheme design, an additional greywater treatment plant with a handling capacity of 700 m³/day is proposed. This new greywater treatment plant is proposed to provide treated greywater for reuse in irrigation and general cleaning activities. The treatment process is shown in Chart 8.1.

Chart 8.1: Greywater Treatment Process Diagram

8.7.2.45 The treatment quality of the system will be designed to the minimum ‘end of pipe’ requirements specified in Table 8.77. While the exact membrane bioreactor (MBR) system to be adopted is subject to detailed design and future procurement, current manufacturer specifications for MBR systems available on the market are able to meet the minimum requirements specified in Table 8.77, and this would form part of the procurement requirements for the future grey water treatment system.

Table 8.77: Minimum Requirements for ‘End of Pipe’ Effluent Quality from the Greywater Treatment System

Parameter	Minimum Requirements
Suspended Solids	≤ 5 mg/L
Biological Oxygen Demand	≤ 10 mg/L
Chemical Oxygen Demand	≤ 50 mg/L
Oil and Grease	≤ 10 mg/L
Surfactants (total)	≤ 5 mg/L
E. coli	< 1 count / 100ml
pH	6.0 – 9.0
Turbidity	< 2 NTU
Faecal Coliforms	Non detectable / 100ml

8.7.2.46 With the greywater effluent treated to the minimum requirements specified in Table 8.77, no adverse water quality impact is anticipated from reuse of treated greywater for irrigation and general cleaning. System piping for the greywater treatment plant will be a separate system from the potable water network and will be identified by appropriate signage and labelling. Any surplus treated greywater not reused would be discharged to the foul sewer system, thus there will be no direct discharges to the marine environment.

Stormwater Discharge

8.7.2.47 During operation phase, stormwater generated from the paved surfaces on HKIA will be discharged via the stormwater culverts as shown in Drawing No. MCL/P132/EIA/8-008. Pollution loading from these stormwater discharges have been incorporated into the operation phase water quality model (Appendix 8.7 refers), and the findings of the quantitative assessment for DO, BOD₅, SS, TIN, NH₃ and E. coli show that no adverse water quality impacts are predicted due to the stormwater discharges from operation of the project.

8.7.2.48 Notwithstanding the results of the quantitative assessment, surface runoff from paved surfaces may carry additional pollutants such as fuels, oils from vehicular and aircraft traffic, and cleaning agents from vehicle and aircraft washing facilities. The existing stormwater system at HKIA is equipped with oil interception systems to remove oil and fuel from stormwater before discharge into the marine environment and such systems will also be implemented for the expanded airport areas. Runoff from vehicle and aircraft washing facilities on HKIA are not permitted to be discharged to the stormwater system. Wastewater generated from these facilities will either be discharged to foul sewer system or collected by a temporary storage tank for off-site disposal at a licensed wastewater treatment facility. With the aforementioned measures in place, no adverse water quality impact is anticipated due to stormwater discharge.

Fuel Spillage

8.7.2.49 With reference to the Permanent Aviation Fuel Facility (PAFF) EIA report, the risk of fuel spillage at the facility was considered extremely low. As described in Section 8.7.1, the preferred option for the diversion of the submarine pipelines is by drilling through the sub-seabed rock layer with the use the horizontal drilling method. The risk of accidental spillage of fuel from a pipeline drilled in bedrock would be substantially lower than that of a pipeline that is buried within the marine sediment layer of the seabed (which may be subject to damage from anchoring, vessel sink or dredging). Within the confines of the bedrock, any unlikely event of leakage of fuel from the pipelines would occur inside the pipeline tunnel and be contained within this space, unless there is a significant fracture of the bedrock allowing seepage of fuel to other areas. Even in the presence of such fractures (if any) in the bedrock, seepage of the fuel will need to migrate through the bedrock and the different layers of sub-seabed strata before reaching the bottom layer of marine sediment, which is at least 10 m beneath the seabed level (refer to Drawing No. MCL/P132/EIA/8-007). Any further migration of the leaked fuel will be significantly hindered by the low permeability clay, which will effectively trap the leaked fuel. Thus it is very unlikely that there will be any release of leaked fuel into the water column. In addition, there are existing preventive measures in place for the fuel pipelines including continuous monitoring of the computerised leak detection system and monthly checks on the cathodic protection system to minimise the risk of pipeline failure. Should leakage be detected, the computerised system would generate alarms that would alert the 24-hour duty supervisor to immediately initiate the emergency shutdown procedures to stop the flow. These measures will also be put in place for the newly diverted pipelines. In view of these reasons, the risk of significant accidental fuel spillage into the marine environment would be negligible, and there is no reasonable case for assuming any fuel spillage scenarios for the marine sections of the fuel pipelines.

8.7.2.50 Aside from the fuel pipeline, incidences of aviation fuel leakage / spillage may arise during refuelling operations and/or aircraft-related accidents. Currently, the airport apron areas are equipped with a spill trap containment system including petrol separators with 10,000 litre capacity, with runoff from areas that have potentially polluting activities designed to drain away from the airport’s southern sea channel. AAHK has continued to install oil interception systems as required to fit the land use and size of different areas. Fuel spillage response plans are also in place at HKIA to contain any spilt fuel. Currently, AAHK maintains an appropriate level of spill response capability via agreements with its term maintenance contractor. The contractor is required to have sufficient spill response equipment available to effectively respond to all spill scenarios that are likely to be encountered at HKIA, and the contractor is on call 24 hours a day. Similar measures to contain any fuel spillages within the boundaries of the airport island will be implemented for the third runway project. With these measures in place, the risk of jet fuel spillage into the marine environment would be minimal.

Maintenance Dredging of the Navigable Waters North of HKIA

8.7.2.51 During operation phase, it has been identified that the changes to the tidal flow regime resulting from the new land formation may induce sedimentation along the navigable waters to the north of HKIA, thereby creating a potential need for periodical maintenance dredging at the navigable area.

8.7.2.52 Referring to the sedimentation results shown in Appendix 8.15 (Figure 121), it can be seen that aside from some sedimentation within the embayed area to the south of the runway and a small area of potential accumulation along the north east facing seawall, no other areas around the project would show any appreciable change in sedimentation after one year, include the area of the navigable waters to the north of HKIA. These findings suggest that despite the local changes in the hydrodynamic flow regime resulting from implementation of the project, there would be no increase in sedimentation along the navigable waters to the north of HKIA.

8.7.2.53 Separately, a morphology study was also undertaken as part of the scheme design, whereby sediment transport patterns were computed using Delft3D-FLOW. The findings from this morphology study concurs with the sedimentation results shown in Appendix 8.15 (Figure 121), as it also indicated a potential for sediment accretion within the embayed areas and along some of the edges of the airport island, but showed limited to no potential for sedimentation along the navigable northern waters of HKIA.

8.7.2.54 Based on the sedimentation results from the water quality model and taking into account the finding of the separately morphology study completed as part of the scheme design, it can be concluded that maintenance dredging would not be required along the navigable waters to the north of HKIA. Consequently, no further assessment of impacts due to possible maintenance dredging is required.

8.8 Mitigation Measures

8.8.1 Construction Phase

Marine Construction Activities

8.8.1.1 Based on the findings from the water quality impact assessment, the design and mitigation measures to be applied during marine construction activities are specified as follows:

General Measures to be Applied to All Works Areas

8.8.1.2 The following good practices shall be adopted for the marine works:

¡ Barges or hoppers shall not be filled to a level which will cause overflow of materials or pollution of water during loading or transportation;

¡ Use of Lean Material Overboard (LMOB) systems shall be prohibited;

¡ Excess materials shall be cleaned from the decks and exposed fittings of barges and hopper dredgers before the vessels are moved;

¡ Plants should not be operated with leaking pipes and any pipe leakages shall be repaired quickly;

¡ Adequate freeboard shall be maintained on barges to reduce the likelihood of decks being washed by wave action;

¡ All vessels shall be sized such that adequate clearance is maintained between vessels and the sea bed at all states of the tide to ensure that undue turbidity is not generated by turbulence from vessel movement or propeller wash;

¡ The 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; and

¡ For ground improvement activities including DCM, the wash water from cleaning of the drilling shaft should be appropriately treated before discharge. The Contractor should ensure the waste water meets the WPCO / TM requirements before discharge. No direct discharge of contaminated water is permitted.

8.8.1.3 In addition to the general measures listed above, the following specific measures shall be adopted for the marine works:

Specific Measures to be Applied to All Marine Works Areas

¡ The daily maximum production rates shall not exceed those assumed in the water quality assessment (specified in Table 8.32);

¡ A maximum of 10 % fines content to be adopted for sand blanket and 20 % fines content for marine filling below +2.5 mPD prior to substantial completion of seawall (until end of Year 2017) shall be specified in the works contract document. From Year 2018 onwards, provided the remaining eastern seawall opening is limited to approx. 500 m wide, a combination of sand and public filling below +2.5 mPD with fines content up to 25 % may be adopted; and

¡ An advance seawall of at least 200 m to be constructed (comprising either rows of contiguous permanent steel cells completed above high tide mark or partially completed seawalls with rock core to high tide mark and filter layer on the inner side) prior to commencement of marine filling activities.

Specific Measures to be Applied to Land Formation Activities prior to Commencement of Marine Filling Works

¡ Double layer ‘Type III’ silt curtains to be applied around the active eastern works areas prior to commencement of sand blanket laying activities. The silt curtains shall be configured to minimise SS release during ebb tides. A silt curtain efficiency test shall be conducted to validate the performance of the silt curtains;

¡ Double layer silt curtains to enclose WSR C7a and silt screens installed at the intake points for both WSR C7a and C8 prior to commencement of construction; and

¡ The silt curtains and silt screens should be regularly checked and maintained.

Specific Measures to be Applied to Land Formation Activities during Marine Filling Works

¡ Double layer ‘Type II’ or ‘Type III’ silt curtains to be applied around the eastern openings between partially completed seawalls prior to commencement of marine filling activities. The silt curtains shall be configured to minimise SS release during ebb tides;

¡ Double layer silt curtains to be applied at the south-western opening prior to commencement of marine filling activities;

¡ Double layer silt curtain to enclose WSR C7a and silt screens installed at the intake points for both WSR C7a and C8 prior to commencement of marine filling activities; and

¡ The silt curtains and silt screens should be regularly checked and maintained.

Specific Measures to be Applied to the Field Joint Excavation Works for the Submarine Cable Diversion

¡ Only closed grabs designed and maintained to avoid spillage shall be used and should seal tightly when operated. Excavated materials shall be disposed at designated marine disposal area in accordance with the DASO permit conditions; and

¡ Silt curtains surrounding the closed grab dredger to be deployed as a precautionary measure.

Modification of the Existing Seawall

8.8.1.4 Silt curtains shall be deployed around the seawall modification activities to completely enclose the active works areas, and care should be taken to avoid splashing of rockfill / rock armour into the surrounding marine environment. For the connecting sections with the existing outfalls, works for these connection areas should be undertaken during the dry season in order that individual drainage culvert cells may be isolated for interconnection works.

Construction of New Stormwater Outfalls and Modifications to Existing Outfalls

8.8.1.5 During operation of the temporary drainage channel, runoff control measures such as bunding or silt fence shall be provided on both sides of the channel to prevent accumulation and release of SS via the temporary channel. Measures should also be taken to minimise the ingress of site drainage into the culvert excavations.

Piling Activities for Construction of New Runway Approach Lights and HKIAAA Marker Beacons

8.8.1.6 Silt curtains shall be deployed around the piling activities to completely enclose the piling works, and care should be taken to avoid spillage of excavated materials into the surrounding marine environment.

8.8.1.7 For construction of the eastern approach lights at the CMPs, the following shall also apply:

¡ Ground improvement via DCM using a close-spaced layout shall be completed prior to commencement of piling works;

¡ Steel casings shall be installed to enclose the excavation area prior to commencement of excavation;

¡ The excavated materials shall be removed using a closed grab within the steel casings;

¡ No discharge of the cement mixed materials into the marine environment will be allowed; and

¡ Excavated materials shall be treated and reused on-site.

Construction Site Runoff and Drainage

8.8.1.8 The site practices outlined in ProPECC Note PN 1/94 should be followed as far as practicable in order to minimise surface runoff and erosion from the land-based construction works areas. The following measures are recommended to protect water quality of the inland and marine areas, and when properly implemented should be sufficient to adequately control site discharges so as to avoid water quality impacts:

¡ Install perimeter cut-off drains to direct off-site water around the site and implement internal drainage, erosion and sedimentation control facilities. Channels, earth bunds or sand bag barriers should be provided on site to direct storm water to silt removal facilities. The design of the temporary on-site drainage system should be undertaken by the Contractors prior to the commencement of construction (for works areas located on the existing airport island) or as soon as the new land is completed (for works areas located on the new landform);

¡ Sand / silt removal facilities such as sand/silt traps and sediment basins should be provided to remove sand / silt particles from runoff to meet the requirements of the TM-DSS standards under the WPCO. The design of efficient silt removal facilities should make reference to the guidelines in Appendix A1 of ProPECC Note PN 1/94. Sizes may vary depending upon the flow rate. The detailed design of the sand/silt traps should be undertaken by the Contractors prior to the commencement of construction;

¡ All drainage facilities and erosion and sediment control structures should be regularly inspected and maintained to ensure proper and efficient operation at all times and particularly during rainstorms. Deposited silt and grit should be regularly removed, at the onset of and after each rainstorm to ensure that these facilities are functioning properly;

¡ Measures should be taken to minimise the ingress of site drainage into excavations. If excavation of trenches in wet periods is necessary, they should be dug and backfilled in short sections wherever practicable. Water pumped out from foundation excavations should be discharged into storm drains via silt removal facilities;

¡ In the event that contaminated groundwater is identified at excavation areas, this should be treated on-site using a suitable wastewater treatment process, The effluent should be treated according to the requirements of the TM-DSS standards under the WPCO prior to discharge to foul sewers or collected for proper disposal off-site. No direct discharge of contaminated groundwater is permitted;

¡ All vehicles and plant should be cleaned before leaving a construction site to ensure no earth, mud, debris and the like is deposited by them on roads. An adequately designed and sited wheel washing facility should be provided at construction site exits. Wash-water should have sand and silt settled out and removed regularly to ensure the continued efficiency of the process. The section of access road leading to, and exiting from, the wheel-wash bay to the public road should be paved with sufficient backfall toward the wheel-wash bay to prevent vehicle tracking of soil and silty water to public roads and drains. All washwater should be treated according to the requirements of the TM-DSS standards under the WPCO prior to discharge;

¡ Open stockpiles of construction materials or construction wastes on-site should be covered with tarpaulin or similar fabric during rainstorms. Measures should be taken to prevent the construction materials, soil, silt or debris from washing away into the drainage system;

¡ Manholes (including newly constructed ones) should be adequately covered and temporarily sealed so as to prevent silt, construction materials or debris being washed into the drainage system and to prevent stormwater runoff being directed into foul sewers; and

¡ Precautionary measures should be taken at any time of the year when rainstorms are likely. Actions to be taken when a rainstorm is imminent or forecasted are summarised in Appendix A2 of ProPECC Note PN 1/94. This includes actions to be taken during and/or after rainstorms. Particular attention should be paid to the control of silty surface runoff during storm events.

Sewage Effluent from Construction Workforce and General Construction Activities

8.8.1.9 Temporary sanitary facilities, such as portable chemical toilets, should be employed on-site where necessary to handle sewage from the workforce. A licensed contractor should be employed to provide appropriate and adequate portable toilets and be responsible for appropriate disposal and maintenance.

8.8.1.10 Construction solid waste, debris and refuse generated on-site should be collected, handled and disposed of properly to avoid entering any nearby stormwater drain. Stockpiles of cement and other construction materials should be kept covered when not being used.

8.8.1.11 Oils and fuels should only be stored in designated areas which have pollution prevention facilities. To prevent spillage of fuels and solvents to any nearby storm water drain, all fuel tanks and storage areas should be provided with locks and be sited on sealed areas, within bunds of a capacity equal to 110 % of the storage capacity of the largest tank. The bund should be drained of rainwater after a rain event.

Drilling Activities for the Submarine Aviation Fuel Pipelines

8.8.1.12 To prevent potential water quality impacts at Sha Chau, the following measures shall be applied:

¡ A ‘zero-discharge’ policy shall be applied for all activities to be conducted at Sha Chau;

¡ No bulk storage of chemicals shall be permitted; and

¡ A containment pit shall be constructed around the drill holes. This containment pit shall be lined with impermeable lining and bunded on the outside to prevent inflow from off-site areas.

8.8.1.13 At the airport island side of the drilling works, the following measures shall be applied for treatment of wastewater:

¡ During pipe cleaning, appropriate desilting or sedimentation device should be provided on site for treatment before discharge. The Contractor should ensure discharge water from the sedimentation tank meet the WPCO / TM requirements before discharge.

¡ Drilling fluid used in drilling activities should be reconditioned and reused as far as possible. Temporary enclosed storage locations should be provided on-site for any unused chemicals that needs to be transported away after all related construction activities are completed. The requirements in ProPECC Note PN 1/94 should be adhered to in the handling and disposal of bentonite slurries.

8.8.2 Operation Phase

8.8.2.1 The findings from the water quality assessment showed that no adverse impacts are anticipated due to implementation of the project during operation phase. Notwithstanding the assessment findings, precautionary measures should be applied to reduce pollutant discharges from the project.

8.8.2.2 Regular inspection should be carried out along the artificial seawall to check for any accumulation of floating refuse, and if necessary, regular removal of accumulated / floating refuse should be undertaken.

8.8.2.3 For stormwater discharges, the following measures should be applied to minimise contaminants in runoff:

¡ Install and maintain roadside gullies to trap and remove silt and grit from stormwater;

¡ Install and maintain oil/grease interceptors for removal of oil and fuel from stormwater; and

¡ Runoff from aircraft and vehicle washing activities should be intercepted and discharged to foul sewer or diverted to temporary storage for subsequent removal and treatment off-site.

8.8.2.4 Precautionary measures for fuel management and spill response should include the following:

¡ Fuel pipelines and hydrant systems should be designed with adequate protection and pressure / leakage detection systems;

¡ A ‘spill trap containment system’ should be designed and provided at aircraft apron and stand areas;

¡ An emergency spill response plan should be in place to provide timely and effective response and remediation of spillage events;

¡ Spill response equipment should be available on site and regularly checked and maintained;

¡ Operation of the fuel supply and refuelling systems should be restricted to qualified and trained personnel with adequate knowledge of the spill response procedures in place;

¡ A penalty system should be set up to discourage poor practices associated with maintenance of aircraft, vehicle and refuelling systems by airport tenants and franchisees; and

¡ Detailed records of all spillage events should be kept and maintained.

8.9 Evaluation of Residual Impacts

8.9.1 Construction Phase

8.9.1.1 With the implementation of the recommended mitigation measures for SS, all WSRs will comply with the principal SS criteria and hence no adverse residual impacts are anticipated. Relevant mitigation measures have also been recommended for other general and specific construction activities and with the implementation of the recommended mitigation measures, no adverse residual impacts are anticipated for all other construction activities.

8.9.2 Operation Phase

8.9.2.1 As implementation of the project will not result in significant changes to the water quality of the study area, the implementation of the recommended precautionary measures are predicted to be sufficient to control water quality impacts to acceptable levels during operational phase. Thus, no adverse residual water quality impacts are expected.

8.10 Environmental Monitoring and Audit

8.10.1 Construction Phase

8.10.1.1 During construction phase, specific mitigation measures in the form of silt curtains will be required, and other measures in the form of general good construction works practices have been specified. An environmental monitoring and audit (EM&A) programme is recommended to check and review the effectiveness of these mitigation measures during construction phase. A silt curtain efficiency pilot test is also recommended to confirm the silt removal efficiency of the silt curtains. Details of the EM&A requirements are specified in the EM&A Manual.

8.10.1.2 To ensure no adverse water quality impacts during construction activities, a water quality monitoring programme as well as a specific DCM monitoring programme is recommended to be implemented throughout construction phase, as part of the management and control programme defined in the action plan of the EM&A Manual. Details of the water quality monitoring programme are specified in the EM&A Manual.

8.10.2 Operation Phase

8.10.2.1 With the implementation of the recommended mitigation measures, no adverse water quality impacts are anticipated during operation phase, hence no specific environmental monitoring and audit is required. However, water quality monitoring for the spent cooling water discharges will be undertaken in accordance with the future WPCO license conditions. Water quality monitoring is also proposed for the greywater treatment facility during commissioning and operation to ensure the treated effluent quality complies with the reuse standards as defined in the EIA.

8.11 Conclusion

8.11.1 Construction Phase

8.11.1.1 Quantitative assessment of water quality impacts associated with SS release during construction of the project has been undertaken. The findings have shown that with the implementation of mitigation measures, there will be no exceedance of the SS criteria at any WSR due to project activities. However, when combined with the assumptions of SS release from concurrent projects, cumulative exceedance is predicted at a few WSRs. Nevertheless, the findings show that the cumulative exceedances are primarily due to the very conservative assumptions for concurrent projects rather than due to the contributions from this project. Therefore, adverse residual water quality impacts due to the project are not anticipated.

8.11.1.2 Based on the findings of the quantitative assessments for dissolved oxygen, nutrients and contaminant, no adverse water quality impacts associated with the submarine 11 kV cable diversion, ground improvement via DCM and surcharge of the land formation are anticipated, hence no specific mitigation measures for dissolved oxygen, nutrients and contaminant release are required.

8.11.1.3 Other specific construction activities including diversion of the submarine aviation fuel pipelines, construction of stormwater outfalls, piling for the new runway approach lights and HKIAAA marker beacons, as well as general construction site drainage and sewage effluent from the construction workforce are not anticipated to result in adverse water quality impacts with the implementation of mitigation measures.

8.11.2 Operation Phase

8.11.2.1 Quantitative assessment of water quality impacts associated with operation of the project has been undertaken. The findings show that despite minor exceedances in SS, TIN and NH₃ were predicted at some WSRs, these were all identified as not attributed to the project. Therefore, implementation of the project will not result in significant changes to the water quality of the study area, and thus adverse water quality impacts as a result of implementation of the project are not predicted.

8.11.2.2 Other operation phase activities including sewage discharge, reuse of treated greywater and accidental fuel spillage are not anticipated to result in adverse water quality impacts with the proposed design / precautionary measures in place. Based on the sedimentation results, maintenance dredging of the navigable waters north of HKIA is not required due to implementation of the project.

Works Areas	Activity	Unmitigated Sediment Loss Rate (per plant)	Mitigated Sediment Loss Rate (per plant)
A2-03B, A2-04, A2-06, A2-07A, A2-07B	Sand Blanket Laying	2.551 kg/s	0.995 kg/s

WSRs / Observation Point (representing ecological sensitive receivers)	Sediment Deposition Rate (g/m²/day)
	Year 2016		Year 2017
	Wet Season	Dry Season	Wet Season	Dry Season
CR2	1.80	10.76	7.62	3.01
CR3	11.21	1.67	4.61	1.51
CR4	0.00	0.00	0.00	1.52
CR5	1.26	0.00	0.00	0.00
E4	5.38	0.84	3.34	1.55
E5	2.91	7.03	0.00	1.09
E12	4.18	2.48	1.55	3.09
F1	1.68	1.26	0.00	4.64
F2	5.44	15.06	1.55	9.16
M4a	0.00	0.25	1.55	0.00
M4b	1.25	0.42	0.00	1.04
M4c	9.87	10.43	36.46	10.67
M4d	135.01	30.54	1.52	62.85
M4e	33.00	47.83	5.98	1.52

8.2 Water Quality Legislation, Standards and Guidelines

8.2.1.1 Relevant legislations, standards and guidelines governing water quality in Hong Kong include the following:

8.2.2 Environmental Impact Assessment Ordinance

8.3.1.1 In accordance with Clause 3.4.6.2 of the EIA Study Brief, water quality impact assessment has been carried out in the study area covering the North Western, North Western Supplementary, Deep Bay and Western Buffer WCZs. The study area is shown in Drawing No. MCL/P132/EIA/8-001.

8.3.2.1 Key water sensitive receivers (WSRs) that may potentially be affected by the proposed third runway project include:

Summary of Latest Baseline Monitoring Data

8.3.3.7 A summary of marine beach water quality monitoring data routinely collected by EPD at relevant monitoring stations is presented in Table 8.15 and Table 8.16.

8.3.4 Non-Statutory Marine Environmental Monitoring for Hong Kong International Airport

8.3.4.1 The Airport Authority Hong Kong is committed to monitoring the surrounding environment of the airport island and has conducted four rounds of monitoring since 2002.

8.3.4.3 Water quality surveys as part of this non-statutory monitoring has been carried out between November 2002 to January 2011. The water quality monitoring locations are indicated in Appendix 8.1. A summary of water quality monitoring results is presented in Table 8.17.

8.3.5 Water Quality Monitoring for New CMPs at East of Sha Chau

8.4 Assessment Criteria

8.4.1.1 For assessment of water quality impacts due to suspended solid (SS) release during construction phase, the criterion specified in the WQO limits the allowable SS elevation to less than 30 % of the ambient level.

8.4.1.3 Based on the 90th percentile from each EPD monitoring station, the criteria for assessment of elevations in SS concentration during construction phase are shown in Table 8.21.

8.4.1.5 As the WQO typically applies to depth-averaged SS concentrations, the depth-averaged criteria will be adopted as the principal assessment criteria for compliance, however, the findings at other depths will also be reviewed and compared to their reference criteria in the assessment.

8.4.2.3 Based on the ambient SS levels summarised in Table 8.25, the allowable SS elevations at WSRs representing WSD seawater intakes (up to the WSD criterion of 10 mg/L) are summarised in Table 8.26.

8.4.2.4 At EPD monitoring stations where the ambient SS level already exceeds the WSD criterion for SS, any change from the existing baseline will be considered as an exceedance of the SS criterion in the assessment.

1 Hawker, D. W. and Connell, D. W. (1992). “Standards and Criteria for Pollution Control in Coral Reef Areas” in Connell, D. W and Hawker, D. W. (eds.), Pollution in Tropical Aquatic Systems, CRC Press, Inc.

8.4.4 Suspended Solids Criterion for Fish Culture Zones

8.4.4.1 In the fish culture zones, the WQO for SS applies, i.e., elevation of SS should be less than 30 % of ambient baseline conditions.

8.4.5.1 Cooling water discharges are associated with thermal plumes and release of residual chlorine and biocide. The WQOs for the North Western WCZ stipulate that the temperature rise in the water column due to human activity should not exceed 2 oC (as shown in Table 8.2).

3 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.

4 S.W.Y. Ma, C.S.W. Kueh, G.W.L. Chiu, S.R. Wild, and J.Y. Yip (1998). Environmental Management of Coastal Cooling Water Discharges in Hong Kong. Wat. Sci. Tech. Vol. 38, Nos. 8-9, pp. 267-274.

8.4.6 Criteria for Dissolved Metals and Other Contaminants

8.5.1 Construction Phase

8.5.1.2 Potential key sources of water quality impact associated with the construction activities for the proposed project include:

8.5.2.1 Potential sources of water quality impact associated with the operational activities for the proposed project include:

8.5.2.2 The key operation phase water quality impacts relate to permanent changes to the existing tidal and current regime around the expanded airport and potential discharge of pollutants from the HKIA site.

8.5.2.6 Increased quantities of sewage generated by the project may create adverse water quality impacts if it is not properly conveyed to a foul sewerage system. Reuse of treated greywater may also be a potential water quality risk if not properly conveyed and treated prior to reuse.

8.5.2.8 The potential need for maintenance dredging of the navigable waters north of HKIA was also identified in the EIA Study Brief as a water quality concern to be addressed in this study.

8.5.2.9 All of the aforementioned potential operation phase water quality impacts are further discussed and assessed in Section 8.7.2.

8.5.3 Concurrent Projects

8.6 Water Quality Assessment Methodology

8.6.1.1 To assess the key potential water quality impact arising from the construction and operation of the project, hydrodynamic modelling was undertaken to quantify SS and contaminant release.

Model Grid Refinement and Validation

8.6.2.1 Construction phase simulations were based on the refined WHM grid (‘without project’), with refinements to land boundaries and bathymetry depending on the worst case years to be simulated (and associated concurrent projects).

8.6.3.1 As described in Section 8.5.1, during construction phase of the project, the key water quality impacts will mainly be due to sediment release from various construction activities, particularly the works related to land formation.

8.6.3.3 Based on the land formation programme, a number of key construction periods with potential impacts to the WSRs have been identified and their details and significance are summarised in Table 8.30. Refer to Appendix 8.4 for the key land formation stages and construction plant quantities.

8.6.3.9 Based on the construction phasing, the likely worst case scenarios for water quality modelling are proposed as follows:

8.6.4 Construction Phase – Suspended Solids

8.6.4.3 With the above assumptions, the worst case sediment loss rate for one DCM rig is estimated as:

8.6.4.9 The sediment loss rates during sand filling can be estimated based on the following assumptions:

8.6.4.10 With the above assumptions, the sediment loss rate for one TSHD is estimated as:

8.6.4.11 With the above assumptions, the sediment loss rate for one TSHD is estimated as:

8.6.4.12 The above estimated sediment loss rates for the higher fines content of 10 % for sand blanket and 20 % for sand filling was adopted in the sediment plume modelling for the various worst case scenarios. The sand is assumed to be released near the seabed.

8.6.4.13 Water jetting would be deployed for the installation of the 11 kV submarine cable. The speed of the jetting machine is taken as 100 m to 500 m per day (with the higher rate assumed for worst case).

8.6.4.14 As confirmed by the Design Consultant, the maximum burial depth is assumed to be 5 m typically and will only require one pass of the jetting machine to reach the required burial depth. The jetting trench is approximately 0.45 m in width and 1 m long.

8.6.4.15 The volumes of seabed sediments to be fluidised are assumed to be:

8.6.4.16 Assuming volume of sediment disturbed is 2.25 m3/metre and a water jetting duration of 10 hours/ day, the rate of sediment fluidised would be:

8.6.4.19 The sediment release in the bed layer (constitutes 10 %) of the water column is assumed in the model. These rates have been adopted in the EIA Report for Black Point Gas Supply Project. Therefore, the sediment loss rate for water jetting is estimated as:

8.6.4.22 With reference to the EIA Report for HKZM BCF, it is conservatively assumed that 20 kg/m3 of sediment release per turn using grab dredger.

8.6.4.23 Assuming a conservative case for dredging duration of 10 hours per day at 300 m3 per day, the rate of sediment loss would be:

8.6.4.26 A summary of the sediment loss rates adopted for sediment plume modelling is presented in Table 8.34.

8.6.4.27 The concurrent projects identified in Section 8.5.3 have been incorporated into the quantitative assessment and details of the assumptions and calculations for sediment release are presented in Appendix 8.5.

8.6.4.30 For dissolved oxygen (DO), DO depletion will be calculated from the following equation:

8.6.4.33 The results of the elutriate tests are shown in Table 8.35.

8.4.1.3 Based on the 90^th percentile from each EPD monitoring station, the criteria for assessment of elevations in SS concentration during construction phase are shown in Table 8.21.

8.4.5.1 Cooling water discharges are associated with thermal plumes and release of residual chlorine and biocide. The WQOs for the North Western WCZ stipulate that the temperature rise in the water column due to human activity should not exceed 2 ^oC (as shown in Table 8.2).

8.6.4.16 Assuming volume of sediment disturbed is 2.25 m³/metre and a water jetting duration of 10 hours/ day, the rate of sediment fluidised would be:

8.6.4.22 With reference to the EIA Report for HKZM BCF, it is conservatively assumed that 20 kg/m³ of sediment release per turn using grab dredger.

8.6.4.23 Assuming a conservative case for dredging duration of 10 hours per day at 300 m³ per day, the rate of sediment loss would be: