8 Water Quality

8.1 Legislation and Standards

8.1.1 Environmental Impact Assessment Ordinance (EIAO), Cap.499, S16

8.1.1.1 This Study follows the TM-EIAO to assess the potential water quality impact that may arise during the construction and operational phases of the Project. Sections in the TM-EIAO relevant to the water quality impact assessment are:

· Annex 6 - Criteria for Evaluating Water Pollution; and

· Annex 14 - Guidelines for Assessment of Water Pollution

8.1.2 Water Quality Objectives (WQOs)

8.1.2.1 The Water Pollution Control Ordinance (WPCO) (Cap.358) provides the major statutory framework for the protection and control of water quality in Hong Kong. According to WPCO and its subsidiary legislation, the whole Hong Kong waters are divided into ten Water Control Zones (WCZs). Water Quality Objectives (WQOs) were established to protect the beneficial uses of water quality in each WCZ.

8.1.2.2 The proposed CBL is located within the Junk Bay WCZ and the study area covers Junk Bay, Victoria Harbour, Eastern Buffer, Port Shelter, Southern and Mirs Bay WCZs. According to the approved EIA Report for the Further Development of Tseung Kwan O Feasibility Study (EIA-111/2005) (EIA-TKOFS), the affected waterbodies are limited to Junk Bay, Victoria Harbour and Eastern Buffer WCZs. Specific WQOs are applied to each of these affected WCZs and are summarized in Tables 8.1, 8.2 and 8.3 below.

Table 8.1 Summary of Water Quality Objectives for Junk 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
Dissolved Oxygen (DO) within 2 m of the seabed	Not less than 2.0 mg/L for 90% of samples	Marine waters
Depth-averaged DO	Not less than 4.0 mg/L for 90% of samples	Marine waters excepting fish culture subzones
	Not less than 5.0 mg/L for 90% of samples	Fish culture subzones
	Not less than 4.0 mg/L	Inland waters
5-Bay Biochemical Oxygen Demand (BOD5)	Change due to waste discharges not to exceed 5 mg/L	Inland waters
Chemical Oxygen Demand (COD)	Change due to waste discharges not to exceed 30 mg/L	Inland waters
pH	To be in the range of 6.5 - 8.5, change due to waste discharges not to exceed 0.2	Marine waters
	To be in the range of 6.0 –9.0	Inland waters
Salinity	Change due to waste discharges not to exceed 10% of ambient	Whole zone
Temperature	Change due to waste discharges not to exceed 2^oC	Whole zone
Suspended solids (SS)	Not to raise the ambient level by 30% caused by waste discharges and shall not affect aquatic communities	Marine waters
	Change due to waste discharges not to exceed 25 mg/L of annual median	Inland waters
Unionised Ammonia (UIA)	Annual mean not to exceed 0.021 mg/L as unionised form	Whole zone
Nutrients	Shall not cause excessive algal growth	Marine waters
Total Inorganic Nitrogen (TIN)	Annual mean depth-averaged inorganic nitrogen not to exceed 0.3 mg/L	Marine waters
Dangerous substances	Should not attain such levels as to produce significant toxic effects in humans, fish or any other aquatic organisms	Whole zone
	Waste discharges should not cause a risk to any beneficial use of the aquatic environment	Whole zone
Bacteria	Not exceed 610 per 100ml, calculated as the geometric mean of all samples collected in one calendar year	Secondary contact recreation subzones and fish culture subzones
	Not exceed 1000 per 100ml, calculated as the geometric mean of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days	Inland waters
Colour	Change due to waste discharges not to exceed 50 Hazen units	Inland waters

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

Table 8.2 Summary of Water Quality Objectives for Victoria Harbour 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
Dissolved Oxygen (DO) within 2 m of the seabed	Not less than 2.0 mg/L for 90% of samples	Marine waters
Depth-averaged DO	Not less than 4.0 mg/L for 90% of samples	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
Salinity	Change due to human activity not to exceed 10% of ambient	Whole zone
Temperature	Change due to human activity not to exceed 2^oC	Whole zone
Suspended solids (SS)	Not to raise the ambient level by 30% caused by human activity	Marine waters
Unionised Ammonia (UIA)	Annual mean not to exceed 0.021 mg/L as unionised form	Whole zone
Nutrients	Shall not cause excessive algal growth	Marine waters
Total Inorganic Nitrogen (TIN)	Annual mean depth-averaged inorganic nitrogen not to exceed 0.4 mg/L	Marine waters
Toxic substances	Should not attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms.	Whole zone
	Human activity should not cause a risk to any beneficial use of the aquatic environment.	Whole zone

Source: Statement of Water Quality Objectives (Victoria Harbour Water Control Zone).

Table 8.3 Summary of Water Quality Objectives for Eastern 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
Dissolved Oxygen (DO) within 2 m of the seabed	Not less than 2.0 mg/L for 90% of samples	Marine waters
Depth-averaged DO	Not less than 4.0 mg/L for 90% of samples	Marine waters excepting fish culture subzones
	Not less than 5.0 mg/L for 90% of samples	Fish Culture Subzones
	Not less than 4.0 mg/L	Water Gathering Ground Subzone and other Inland waters
5-Bay Biochemical Oxygen Demand (BOD5)	Change due to waste discharges not to exceed 3 mg/L	Water Gathering Ground Subzones
	Change due to waste discharges not to exceed 5 mg/L	Inland waters
Chemical Oxygen Demand (COD)	Change due to waste discharges not to exceed 15 mg/L	Water Gathering Ground Subzones
	Change due to waste discharges not to exceed 30 mg/L	Inland waters
pH	To be in the range of 6.5 – 8.5, change due to waste discharges not to exceed 0.2	Marine waters
	To be in the range of 6.5 – 8.5	Water Gathering Ground Subzones
	To be in the range of 6.0 – 9.0	Inland waters
Salinity	Change due to waste discharges not to exceed 10% of ambient	Whole zone
Temperature	Change due to waste discharges not to exceed 2^oC	Whole zone
Suspended solids (SS)	Not to raise the ambient level by 30% caused by waste discharges and shall not affect aquatic communities	Marine waters
	Change due to waste discharges not to exceed 20 mg/L of annual median	Water Gathering Ground Subzones
	Change due to waste discharges not to exceed 25 mg/L of annual median	Inland waters
Unionised Ammonia (UIA)	Annual mean not to exceed 0.021 mg/L as unionised form	Whole zone
Nutrients	Shall not cause excessive algal growth	Marine waters
Total Inorganic Nitrogen (TIN)	Annual mean depth-averaged inorganic nitrogen not to exceed 0.4 mg/L	Marine waters
Dangerous substances	Should not attain such levels as to produce significant toxic effects in humans, fish or any other aquatic organisms	Whole zone
	Waste discharges should not cause a risk to any beneficial use of the aquatic environment	Whole zone
Bacteria	Not exceed 610 per 100ml, calculated as the geometric mean of all samples collected in one calendar year	Fish Culture Subzones
	Less than 1 per 100ml, 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
	Not exceed 1000 per 100ml, calculated as the geometric mean of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days	Inland waters
Colour	Change due to waste discharges not to exceed 30 Hazen units	Water Gathering Ground
	Change due to waste discharges not to exceed 50 Hazen units	Inland waters

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

8.1.3 Technical Memorandum on Effluent Discharge Standards

8.1.3.1 Discharges of effluents are subject to control under the WPCO. The Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS) specifies limits for effluent discharges in different water control zones.

8.1.4 WSD Seawater Intakes

8.1.4.1 The criteria for assessing the water quality impact on the Water Supplies Department (WSD) seawater intakes are based on the Water Quality Criteria of Seawater for Flushing Supply (at intake point) issued by the Water Supplies Department (WSD) and are summarized in the Table 8.3a.

Table 8.3a: WSD Water Quality Criteria for Salt Water Intakes

Parameter	Concentration
Colour	< 20 H.U.
Turbidity	< 10 N.T.U.
Threshold Odour No.	< 100
Ammonia Nitrogen	< 1 mg/l
Suspended Solids	< 10 mg/l
Dissolved Oxygen	> 2 mg/l
Biochemical Oxygen Demand	< 10 mg/l
Synthetic Detergents	< 5 mg/l
E. coli.	< 20,000 cfu/100 ml

8.1.5 Practice Note for Professional Persons on Construction Site Drainage

8.1.5.1 The Practice Note for Professional Persons (ProPECC Note PN1/94) on Construction Site Drainage provides guidelines for the handling and disposal of construction discharges. This note is applicable to this study in controlling the site runoff and wastewater generated during the construction phase. The types of discharges from construction sites outlined in the ProPECC Note PN1/94 include:

· Surface run-off,

· Groundwater,

· Boring and drilling water,

· Wastewater from concrete batching,

· Wheel washing water,

· Bentonite slurries,

· Water for testing and sterilization of water retaining structures and water pipes,

· Wastewater from building construction and site facilities, and

· Acid cleaning, etching and pickling wastewater.

8.2 Description of Existing Environment

8.2.1 Marine Water Quality

8.2.1.1 The marine water quality monitoring data routinely collected by EPD were used to establish the baseline condition. The EPD monitoring stations in the Junk Bay WCZ (JM3 and JM4), Eastern Buffer WCZ (EM1 and EM2) and Victoria Harbour WCZ (VM1 and VM2) are shown in Drawing No. 209506/EIA/WQ/001. Other WCZs such as Southern WCZ are considered far away from site and will not take into account. Summaries of the EPD’s Routine Water Quality Monitoring Data in year 2009 and 2010 are given in Tables 8.4, 8.5 and 8.6 as below.

Table 8.4 Summary of 2009-2010 Marine Water Quality in Junk Bay WCZ Monitoring Stations

Parameter		JM3		JM4
		2009	2010	2009	2010
Temperature (OC)		23.5 (16.8-28.4)	22.5 (16.3-28.7)	23.3 (17.0-28.4)	22.4 (16.3-27.6)
Salinity (ppt)		32.1 (27.7-33.6)	32.4 (30.8-33.8)	32.5 (29.5-33.8)	32.6 (30.9-33.9)
Dissolved Oxygen (DO) (% saturation)		86 (71-112)	86 (71-96)	83 (69-102)	87 (68-100)
	Bottom	79 (50-100)	82 (56-98)	74 (39-101)	81 (42-100)
DO (mg/L)		6.0 (4.9-7.3)	6.2 (4.9-7.6)	5.8 (4.8-7.0)	6.3 (4.5-7.9)
	Bottom	5.6 (3.5-7.0)	6.0 (3.9-7.7)	5.3 (2.7-7.1)	5.9 (2.9-8.0)
pH		8.0 (7.7-8.3)	7.9 (7.6-8.2)	8.0 (7.7-8.3)	7.9 (7.6-8.2)
Secchi Disc Depth (m)		2.7 (1.8-3.5)	2.9 (1.8-4.2)	2.8 (1.8-3.5)	3.0 (1.8-5.6)
Turbidity (NTU)		4.0 (1.2-9.1)	2.8 (0.7-6.4)	4.6 (2.0-9.9)	3.2 (1.3-7.2)
Suspended Solids (mg/L)		4.3 (2.2-7.9)	2.5 (0.8-4.6)	5.0 (2.5-8.6)	2.8 (1.7-5.3)
5-day Biochemical Oxygen Demand (mg/L)		0.8 (0.2-1.7)	0.7 (0.3-1.5)	0.8 (<0.1-1.8)	0.6 (0.1-1.5)
Ammonia Nitrogen (mg/L)		0.05 (0.017-0.089)	0.058 (0.027-0.097)	0.04 (0.021-0.068)	0.047 (0.020-0.082)
Unionised Ammonia (mg/L)		0.002 (<0.001-0.003)	0.002 (<0.001-0.006)	0.001 (<0.001-0.003)	0.002 (<0.001-0.005)
Nitrite Nitrogen (mg/L)		0.019 (0.003-0.091)	0.021 (0.006-0.051)	0.015 (0.002-0.057)	0.019 (0.005-0.048)
Nitrate Nitrogen (mg/L)		0.064 (0.029-0.174)	0.068 (0.017-0.111)	0.056 (0.020-0.147)	0.056 (0.007-0.099)
Total Inorganic Nitrogen (mg/L)		0.13 (0.05-0.29)	0.15 (0.07-0.20)	0.11 (0.05-0.24)	0.12 (0.04-0.19)
Total Kjeldahl Nitrogen (mg/L)		0.18 (0.08-0.29)	0.18 (0.10-0.26)	0.15 (0.06-0.22)	0.16 (0.10-0.22)
Total Nitrogen (mg/L)		0.26 (0.14-0.41)	0.27 (0.14-0.35)	0.23 (0.11-0.33)	0.23 (0.12-0.32)
Orthophosphate Phosphorus (mg/L)		0.013 (0.004-0.022)	0.014 (0.006-0.019)	0.012 (0.007-0.018)	0.012 (0.004-0.023)
Total Phosphorus (mg/L)		0.03 (<0.02-0.04)	0.03 (<0.02-0.05)	0.03 (0.02-0.03)	0.03 (<0.02-0.05)
Silica (as SiO2) (mg/L)		0.6 (0.09-1.77)	0.063 (0.15-0.97)	0.59 (0.15-1.40)	0.61 (0.13-0.89)
Chlorophy ll-α (µg/L)		4.4 (0.8-11.5)	3.9 (0.5-21.4)	4.0 (0.6-13.0)	3.3 (0.5-14.3)
E. Coli (cfu/100ml)		49 (11-430)	46 (5-140)	55 (11-150)	30 (4-240)
Faecal Coliforms (cfu/100ml)		140 (59-770)	110 (10-400)	140 (18-380)	66 (12-720)

Notes:

(1) Data presented are depth averaged (except as specified) and are the annual arithmetic mean except for E. coli (geometric mean)

(2) Data in bracket indicate ranges

Table 8.5 Summary of 2009-2010 Marine Water Quality in Eastern Buffer WCZ Monitoring Stations

Parameter		EM1		EM2
		2009	2010	2009	2010
Temperature (OC)		23.2 (17.4-28.5)	22.4 (16.5-27.5)	23.4 (17.5-28.5)	22.4 (16.4-27.7)
Salinity (ppt)		32.7 (30.8-33.9)	32.6 (30.8-33.9)	32.2 (25.7-33.9)	32.7 (30.9-33.9)
Dissolved Oxygen (DO) (% saturation)		79 (53-103)	88 (64-98)	82 (66-106)	87 (69-101)
	Bottom	75 (38-102)	81 (44-100)	76 (44-102)	83 (45-101)
DO (mg/L)		5.6 (3.7-7.1)	6.3 (4.2-7.7)	5.8 (4.5-7.3)	6.3 (4.5-8.0)
	Bottom	5.3 (2.7-7.1)	5.9 (3.0-8.0)	5.4 (3.1-7.2)	6.0 (3.1-8.0)
pH		8.0 (7.6-8.2)	7.9 (7.6-8.2)	8.0 (7.6-8.3)	8.0 (7.7-8.1)
Secchi Disc Depth (m)		2.6 (2.0-3.2)	2.9 (1.8-4.5)	2.7 (1.8-4.0)	3.0 (1.9-4.5)
Turbidity (NTU)		4.4 (2.0-9.9)	3.5 (1.4-7.2)	4.4 (2.3-9.3)	3.6 (1.0-6.8)
Suspended Solids (mg/L)		4.5 (2.8-6.9)	3.2 (1.0-7.5)	4.0 (2.8-6.6)	3.2 (1.3-7.7)
5-day Biochemical Oxygen Demand (mg/L)		0.6 (<0.1-1.6)	0.7 (0.2-1.7)	0.6 (<0.1-1.6)	0.5 (0.1-1.0)
Ammonia Nitrogen (mg/L)		0.039 (0.014-0.063)	0.051 (0.012-0.101)	0.029 (0.008-0.055)	0.041 (0.009-0.099)
Unionised Ammonia (mg/L)		0.001 (<0.001-0.003)	0.002 (<0.001-0.006)	0.001 (<0.001-0.003)	0.002 (<0.001-0.005)
Nitrite Nitrogen (mg/L)		0.016 (0.003-0.073)	0.018 (0.005-0.047)	0.015 (<0.002-0.087)	0.018 (0.005-0.047)
Nitrate Nitrogen (mg/L)		0.062 (0.019-0.197)	0.058 (0.007-0.113)	0.055 (0.009-0.217)	0.054 (0.006-0.108)
Total Inorganic Nitrogen (mg/L)		0.12 (0.04-0.30)	0.13 (0.03-0.23)	0.10 (0.02-0.34)	0.11 (0.03-0.22)
Total Kjeldahl Nitrogen (mg/L)		0.15 (0.11-0.23)	0.16 (0.09-0.31)	0.15 (0.09-0.20)	0.13 (0.08-0.25)
Total Nitrogen (mg/L)		0.23 (0.14-0.40)	0.24 (0.12-0.41)	0.22 (0.11-0.47)	0.21 (0.12-0.37)
Orthophosphate Phosphorus (mg/L)		0.012 (0.008-0.018)	0.013 (0.003-0.029)	0.010 (0.005-0.019)	0.013 (0.004-0.027)
Total Phosphorus (mg/L)		0.03 (0.02-0.03)	0.03 (<0.02-0.04)	0.02 (<0.02-0.03)	0.03 (<0.02-0.05)
Silica (as SiO2) (mg/L)		0.62 (0.23-1.76)	0.61 (0.15-0.85)	0.58 (0.20-1.87)	0.61 (0.25-0.94)
Chlorophy ll-α (µg/L)		3.5 (0.8-8.6)	4.8 (0.5-24.3)	3.4 (0.6-10.7)	1.9 (0.5-9.5)
E. Coli (cfu/100ml)		65 (6-470)	25 (1-330)	19 (3-240)	15 (1-180)
Faecal Coliforms (cfu/100ml)		140 (7-1400)	61 (7-1400)	46 (5-970)	33 (2-1100)

Notes:

(1) Data presented are depth averaged (except as specified) and are the annual arithmetic mean except for E. coli (geometric mean)

(2) Data in bracket indicate ranges

Table 8.6 Summary of 2009-2010 Marine Water Quality in Victoria Harbour WCZ Monitoring Stations

Parameter		VM1		VM2
		2009	2010	2009	2010
Temperature (OC)		23.6 (18.6-28.4)	22.8 (16.5-27.3)	23.8 (18.7-28.5)	23.0 (16.5 - 27.3)
Salinity (ppt)		32.3 (27.0-33.6)	32.0 (29.2-33.6)	31.7 (22.5-33.5)	31.7 (29.1 - 33.7)
Dissolved Oxygen (DO) (% saturation)		78 (53-102)	77 (49-95)	79 (61-102)	74 (53 - 90)
	Bottom	76 (48-102)	67 (16-84)	78 (61-102)	67 (17 - 93)
DO (mg/L)		5.5 (3.5-7.0)	5.6 (3.3-7.6)	5.6 (4.1-7.0)	5.4 (3.5 - 6.7)
	Bottom	5.4 (3.3-7.1)	4.8 (1.1-6.3)	5.5 (4.2-7.0)	4.8 (1.2 - 6.4)
pH		8.0 (7.8-8.3)	7.9 (7.6-8.2)	8.0 (7.6-8.3)	7.9 (7.6 - 8.2)
Secchi Disc Depth (m)		2.5 (1.5-3.4)	3.0 (1.9-4.1)	2.3 (1.5-3.2)	2.9 (2.0 - 4.6)
Turbidity (NTU)		5.6 (2.6-11.3)	4.0 (1.5-12.1)	4.9 (2.2-9.9)	3.2 (1.1 - 5.9)
Suspended Solids (mg/L)		7.2 (3.5-17.9)	4.0 (1.4-8.1)	5.2 (2.7-8.3)	3.6 (0.9 - 7.6)
5-day Biochemical Oxygen Demand (mg/L)		0.6 (0.2-1.0)	0.7 (<0.1-1.2)	0.7 (<0.1-1.2)	0.9 (<0.1 - 1.6)
Ammonia Nitrogen (mg/L)		0.06 (0.029-0.190)	0.083 (0.042-0.187)	0.08 (0.041-0.200)	0.120 (0.063 - 0.197)
Unionised Ammonia (mg/L)		0.002 (0.001-0.005)	0.003 (<0.001-0.010)	0.003 (0.002-0.006)	0.004 (<0.001 - 0.011)
Nitrite Nitrogen (mg/L)		0.021 (0.004-0.102)	0.024 (0.008-0.055)	0.027 (0.004-0.154)	0.027 (0.007 - 0.053)
Nitrate Nitrogen (mg/L)		0.076 (0.022-0.201)	0.097 (0.027-0.203)	0.097 (0.020-0.313)	0.123 (0.029 - 0.257)
Total Inorganic Nitrogen (mg/L)		0.16 (0.07-0.34)	0.20 (0.09-0.32)	0.21 (0.07-0.60)	0.27 (0.10 - 0.40)
Total Kjeldahl Nitrogen (mg/L)		0.19 (0.09-0.33)	0.21 (0.12-0.32)	0.21 (0.10-0.35)	0.25 (0.15 - 0.32)
Total Nitrogen (mg/L)		0.29 (0.19-0.48)	0.33 (0.16-0.45)	0.33 (0.18-0.75)	0.4 (0.19 - 0.59)
Orthophosphate Phosphorus (mg/L)		0.016 (0.008-0.030)	0.020 (0.010-0.036)	0.019 (0.008-0.041)	0.024 (0.011 - 0.039)
Total Phosphorus (mg/L)		0.03 (0.02-0.05)	0.03 (0.02-0.06)	0.03 (0.02-0.06)	0.04 (0.02 - 0.05)
Silica (as SiO2) (mg/L)		0.65 (0.18-1.80)	0.74 (0.25-1.30)	0.72 (0.21-2.60)	0.79 (0.22 - 1.50)
Chlorophy ll-α (µg/L)		2.8 (0.4-7.3)	2.8 (0.5-12.2)	3.1 (0.7-9.1)	3.3 (0.5 - 15.4)
E. Coli (cfu/100ml)		210 (53-950)	710 (180-4400)	710 (100-9400)	2000 (420 - 17000)
Faecal Coliforms (cfu/100ml)		490 (69-3400)	1600 (410-9400)	1400 (150-21000)	4500 (680 - 27000)

Notes:

(1) Data presented are depth averaged (except as specified) and are the annual arithmetic mean except for E. coli (geometric mean)

(2) Data in bracket indicate ranges

8.2.1.2 According to EPD’s Marine Water Quality Report 2010, with the implementation of the HATS Stage 1 in 2002 by which all sewage generated from Junk Bay and Eastern Buffer WCZ was diverted and treated at the Stonecutter Island Sewerage Treatment Works, the water quality of these two WCZs has improved significantly with full compliance (100%) with the WQOs.

8.2.1.3 In the Victoria Harbour WCZ, the 2010 compliance rate was 77% compared with 93% in 2009. The lower compliance rate was mainly due to the non-compliance with DO objective at 6 stations in west of Victoria Harbour (VM1, 4, 5, 6, 12 and 15) in the summer months of 2010. Similar to the Tolo Harbour WCZ, the low DO situation was likely related to the unusually hot and wet weather during July to September. The E. coli level in the general western Victoria Harbour area decreased by 47%-68% compared with that in 2009 which could be attributed to the commissioning of the Advance Disinfection Facilities (ADF) at the Stonecutters Island Sewage Treatment Works (SCISTW) in March 2010. However, no decrease in E. coli level was observed in central Victoria Harbour (from North Point to Sai Wan) because the discharges from the four remaining sewage screening plants on the north side of Hong Kong Island have not yet been intercepted for treatment at the SCISTW.

8.3 Water Quality Sensitive Receivers & Pollution Sources

8.3.1 Water Quality Sensitive Receivers

8.3.1.1 The water quality sensitive receivers (WSR) in the vicinity will include the followings:

· Cooling Water Intakes,

· Salt Water Intakes,

· Gazetted Beaches,

· Fish Culture Zones,

· Coral Communities,

· Site of Special Scientific Interest (SSSI), and

· Benthic Communities, in particular Amphioxus (Spotted Occurrence of Amphioxus).

8.3.1.2 The key WSRs that are potentially affected during the construction and operational phases of the CBL project are listed in Table 8.7. Drawing No. 209506/EIA/WQ/001 shows the locations of these water quality sensitive receivers. The information of benthic and coral sites have been updated in accordance with the latest dive survey results.

Table 8.7 Water Sensitive Receivers

WSR ID	Description	Reference
SWI1	WSD’s Salt Water Intakes at Tseung Kwan O	1, 3
SWI2	WSD’s Salt Water Intakes at Yau Tong	1, 3
SWI3	WSD’s Salt Water Intakes at Tai Wan	1
SWI4	WSD’s Salt Water Intakes at Cha Kwo Lang	1, 3
SWI5	WSD’s Salt Water Intakes at North Point	1, 3
SWI6	WSD’s Salt Water Intakes at Quarry Bay	1, 3
SWI7	WSD’s Salt Water Intakes at Sai Wan Ho	1, 3
SWI8	WSD’s Salt Water Intakes at Heng Fa Chuen	1, 3
SWI9	WSD’s Salt Water Intakes at Siu Sai Wan	1, 3
SWI10	Salt Water Intakes at Cape D’Aguilar for Swire Institute of Marine Science, The University of Hong Kong	3
CWI1	Cooling Water Intakes for Dairy Farm Ice Plant	1, 3
CWI2	Cooling Water Intakes for Pamela Youde Nethersole Eastern Hospital	1, 3
CWI3	Future Kai Tak Cooling Water Intakes	9
CC1	Coral Sites at Chiu Keng Wan	1, 3, 4, 8
CC2	Coral Sites at Junk Bay	3, 4, 8
CC3	Coral Sites at Junk Island	3, 4, 8
CC4	Coral Sites at Fat Tong Chau West	3, 4
CC5	Coral Sites at Tso Tui Wan North	3, 4
CC6	Coral Sites at Joss House Bay	1, 4
CC7	Coral Sites at Tung Lung Chau West	1, 3, 4
CC8	Coral Sites at Tung Lung Chau East	1, 4
CC9	Coral Sites at Shek Mei Tau	3, 4
CC10	Coral Sites at So Shi Tau	1
CC11	Coral Sites at Tai Wang Tau	1
CC12	Coral Sites at Po Keng Teng	1
CC13	Coral Sites at Junk Bay near Chiu Keng Wan	8
SS1	SSSI at Shek O Headland	1, 6
SS2	SSSI at Cape D’Aguilar	1, 6
FCZ1	Fish Culture Zone at Po Toi O	1, 3, 7
FCZ2	Fish Culture Zone at Tung Lung Chau	1, 3, 7
AM1	Spotted Occurrence of Amphioxus (historical record of summer survey)	3
AM2	Spotted Occurrence of Amphioxus (Yr 2006 record of summer survey)	3
AM3	Spotted Occurrence of Amphioxus (Yr 2006 record of summer survey)	3
GB1	Shek O Rocky Bay	1, 3, 5
GB2	Shek O Beach	1, 3, 5
GB3	Big Wave Bay Beach	1, 3, 5
GB4	Clear Water Bay First Beach	1, 3, 5
GB5	Clear Water Bay Second Beach	1, 3, 5

References:

(1) EIA-TKOFS

(2) Not used

(3) EIA Report for Hong Kong Offshore Wind Farm in Southeastern Waters (EIA-167/2009)

(4) Binnie Consultants Ltd (1995) Marine Ecology of Hong Kong - Report on Underwater Dive Surveys

(5) LCSD websites: http://www.lcsd.gov.hk

(6) Tai Tam & Shek O Outline Zoning Plan S/H18/10

(7) AFCD websites: http://www.afcd.gov.hk/tc_chi/fisheries/fish_aqu/fish_aqu_mpo/fish_aqu_mpo.html

(8) AECOM Marine Ecological Survey Report, 2003

(9) Revised Preliminary Outline Development Plan for Kai Tak Development

8.3.2 Pollution Sources

Construction Phase

8.3.2.1 The principal water quality concern associated with the CBL is related to the seabed disturbance during the construction period. There will be a need for excavation and filling activities for the bridge piers of the project. These operations will inevitably result in the loss and resuspension of sediment into the water column where they will add to the suspended sediment loads.

8.3.2.2 During excavation works, fine material will be displaced and may be carried downstream of the works area. The extent of the suspended sediment plume will depend on the rate of release, the working methods adopted, the particle size of the excavated material, settling velocity, the prevailing currents and hydrodynamic conditions. Similar disturbance may be experienced during backfilling, the backfill material will be very much coarser grained and heavier.

8.3.2.3 Sediment laden plumes may directly affect marine organisms through abrasion and clogging of fish gills and other organs or possibly result in reducing light penetration.

8.3.2.4 Depending on the sediment quality, excavation operations can give rise to concerns about possible release of nutrients or organically rich material which could result in oxygen depletion.

8.3.2.5 In addition to the marine works, the CBL project would entail significant land based works for construction works. The main water quality related issues will be to prevent erosion on site and minimise suspended sediment loads washed out in stormwater and to control wastewater streams from temporary sewage facilities, cementitious waters and general construction refuse. Control of construction phase sewage will also be an issue. Toilets are required to be connected to the local sewerage system if possible during construction. Otherwise, chemical toilets will be used.

8.3.2.6 In summary, the key construction phase water pollution sources will be as follows:

· Excavation activities during the construction period, which may cause release of suspended solids, contaminants and nutrients into the water body;

· Changes in sediment deposition rate, which may affect the adjacent WSRs and ecological sensitive receivers;

· Construction site runoff, which may cause the increase in suspended solids levels and possibly oils due to erosion of exposed surfaces, stockpiles and material storage areas, fuel and oil storage and maintenance areas and dust suppression sprays;

· Wastewater and sewage generated from construction activities, which may cause pollution to the surrounding water bodies;

· Litter from packaging materials and waste construction materials; and

· Construction workforce sewage.

Operational Phase

8.3.2.7 There will be no routine discharge of wastewater or contaminated surface drainage to sea or surface watercourse in the operational phase but there will be some run-off from the road surfaces that could be marginally contaminated with pollution from vehicles fuel.

8.3.2.8 In summary, the key operational phase water pollution sources will be as follows:

· Changes in hydraulic friction that may lead to long-term impacts on the hydrodynamic and water quality conditions, and WSRs within the Junk Bay WCZ, Eastern Buffer WCZ and Victoria Harbour WCZ; and

· Surface run-off from the road surfaces.

8.4 Potential Concurrent Projects

8.4.1.1 The tentative construction period of marine works (excavation) for CBL will be from May 2017 to August 2018. The major existing/planned projects and bridge projects that might potentially affect the hydrodynamic regime and water quality are listed in Table 8.8.

Table 8.8 Planned Projects that will Affect the Hydrodynamic Regime and Water Quality

Project	Construction Programme	Effect on Cumulative Water Quality Impact (Construction Phase)	Effect on Hydrodynamic Regime (Operational Phase)
Shatin Central Link ^(1)
Dredging at Kai Tak Runway	Jul 2012 to Dec 2012	û	û
Dredging at Open Harbour	2016	û	û
Dredging at Causeway Bay Typhoon Shelter	2016	û	û
Cruise Terminal ^(2)
Dredging Stage 1 - Seawall	2011 to 2012	û	û
Dredging Stage 1 – Manoeuvre	2011 to 2012	û	ü
Dredging Stage 1 - Fireboat Berth	2011 to 2012	û	ü
Dredging Stage 2 - Phase II Berth	2013 to 2014	û	ü
Trunk Road T2 ^(3)
Dredging	Mar 2012 to Jan 2014	û	û
Dredging	Feb 2015 to May 2017	ü	û
Filling - Public Fill	May 2012 to Dec 2012	û	û
Filling - Public Fill	Apr 2013 to Dec 2016	ü	û
TKO LT-Tunnel Reclamation ^(4)
Reclamation (Public fill)	Jul 2018 to Sept 2018	ü	ü
CLP Windfarm ^(5)
Grab Dredging - Cable	Jan 2017 to Apr 2017	ü	û
Jetting – Cable	Jan 2017 to Apr 2017	ü	û
Suction Caisson - Windfarm foundation	Apr 2017 to Sep 2017	û	û
Gas Pipeline ^(2)
Grab Dredging - TKW to NP	Apr 2012 to Dec 2012	û	û

Note:

(1) Information from MTR (SCL-COR-HSD-ENV-040363 dated 9 Dec 2010) and SCL project teams. According to the findings of the EIA study, there will be no impact to Junk Bay from the SCL dredging works.

(2) EIA reports of Submerged Gas Pipeline and Cruise Terminus.

(3) Information from T2 project team (A0516-EB000560-HCL-HKL-00 dated 1 Nov 2010).

(4) Information from TKO-LT Tunnel project team.

(5) Information from CLP project team, the Suction Caisson of windfarm are considered far away from site and not included in the model.

8.5 Assessment Methodology

8.5.1 Introduction

8.5.1.1 Indicator points have been selected in the water quality model to provide hydrodynamic and water quality outputs to evaluate the water quality impact. The selected indicator points include the WSR and EPD marine water sampling stations. The locations of EPD marine water sampling stations JM3 & JM4 in the Junk Bay WCZ; EM1, EM2 & EM3 in the Eastern Buffer WCZ; and VM1 & VM2 in the Victoria Harbour WCZ are also shown in Drawing No. 209506/EIA/WQ/001.

8.5.1.2 The 3-dimensional modelling tool, Delft3D, has been adopted to simulate the hydrodynamic and water quality impact due to the construction and operation of CBL. The Delft3D-FLOW module and Delft3D-WAQ module have been used for hydrodynamic and water quality simulations respectively.

8.5.1.3 The hydrodynamic outputs from the model will provide inputs for the water quality simulation. The hydrodynamic forcing including averaged fresh water flows, wind and boundary conditions of the dry season and wet seasons will be applied separately in the corresponding hydrodynamic simulations.

8.5.1.4 The Junk Bay Model was nested and validated with the Update Model, which is already well calibrated against the criteria in Table 8.9.

Table 8.9 Calibration Parameters for Update Model

Criteria	Level of fitness with field data
Tidal elevation (rms)	< 8%
Maximum phase error at high water and low water	< 20 minutes
Maximum current speed deviation	< 30%
Maximum phase error at peak speed	< 20 minutes
Maximum direction error at peak speed	< 15 degrees
Maxium salinity deviation	< 2.5 ppt

8.5.1.5 The hydrodynamic parameters of Junk Bay model has been validated and linked to the Update Model under EIA-TKOFS (EIA-111/2005). The model has therefore been adopted for hydrodynamic and water quality modelling in the present study.

8.5.2 Assessment Criteria

Water Quality Objectives

8.5.2.1 For the WCZs of interest, the WQO for suspended solids is defined as “waste discharge not to raise the natural ambient level by 30% nor cause the accumulation of suspended solids which may adversely affect aquatic communities.” In order to determine the ambient suspended solids concentrations in the waters likely to be impacted by the construction works, the suspended solids level for Stations JM3, JM4, VM1, VM2, EM1, EM2, EM3 and MM19 (see Drawing No. 209506/EIA/WQ/001) has been adopted as the ambient suspended solids concentrations (Table 8.10).

8.5.2.2 The WQO of suspended solid is usually interpreted as the depth averaged suspended solids concentrations. However, the suspended solids concentrations near the seabed, especially when impacted by dredging and filling works, can be significantly larger than the depth averaged suspended solids concentrations. As a result, when assessing the impacts of the dredging and filling works on the suspended solids concentrations, it is proposed that ambient SS level shall be the depth averaged 90th percentile concentrations. Table 8.11 summarises the depth averaged 90th percentile concentrations. Thus, the WQO for each EPD monitoring station shall be 30% increment of the 90th percentile concentration and are presented in Table 8.12.

Table 8.10 Average Suspended Solids Concentrations from EPD Routine Monitoring Programme (2001-2010)

Station	Suspended Solids Concentrations (mg/L) 2001 - 2010
	Dry Season				Wet Season
	Surface	Middle	Bottom	Depth Averaged	Surface	Middle	Bottom	Depth Averaged
JM3	3.1 (13-0.8)	3.8 (31-0.6)	4.9 (14-0.9)	4.0 (15.2-1.2)	2.3 (7.2-0.6)	2.8 (9.9-0.7)	3.9 (9.0-1.0)	3.0 (8.4-0.8)
JM4	2.9 (7.5-0.5)	5.2 (110-1)	5.6 (16-1.1)	4.5 (38.7-1.1)	2.9 (13-0.7)	3.5 (17-1.2)	6.5 (31-1.4)	4.3 (19-1.6)
EM1	2.8 (7.7-0.8)	3.2 (9.2-1.1)	5.3 (23-1.3)	3.8 (12.8-1.2)	2.9 (11-1)	3.7 (12-0.8)	5.8 (21-1.7)	4.1 (13.2-1.3)
EM2	2.8 (9-0.6)	3.2 (13-0.8)	6.3 (64-0.6)	4.1 (22.9-0.7)	2.7 (11-0.6)	3.1 (17-0.8)	5.3 (19-1.2)	3.7 (15.7-1.3)
EM3	3.0 (10-0.7)	3.7 (15-0.8)	5.6 (21-1.3)	4.1 (14.2-1.2)	2.3 (11-0.6)	2.7 (13-0.8)	5.9 (52-1.2)	3.6 (25.3-1.1)
VM1	3.4 (9.5-1)	4.2 (18-1)	6.0 (47-0.8)	4.6 (17.9-0.9)	3.2 (12-1.2)	5.8 (19-1.1)	10.1 (36-2.4)	6.4 (18-1.9)
VM2	3.4 (6.9-1)	4.1 (9.2-1.1)	5.0 (15-1.2)	4.2 (9.9-1.3)	3.8 (8.3-0.6)	4.3 (26-0.8)	5.3 (20-0.9)	4.5 (12.8-0.9)
MM19	1.9 (6.1-0.5)	2.5 (12-0.6)	5.5 (23-0.9)	3.3 (13.7-0.8)	1.6 (3.8-0.5)	1.9 (4.2-0.6)	5.5 (13-0.8)	3.0 (6.4-0.7)

Notes: The data are presented as the arithmetic mean and range (max – min) of the suspended solids concentrations at each station at the three monitoring levels and as the depth averaged concentrations.

Table 8.11 90^th Percentile Suspended Solids Concentrations from EPD Routine Monitoring Programme (2001-2010)

Station	90^th Percentile Suspended Solids Concentrations (mg/L) 2001 - 2010
	Dry Season				Wet Season
	S	M	B	DA	S	M	B	DA
JM3	4.5	5.9	9.8	6.4	4.0	4.1	6.7	5.4
JM4	4.7	6.3	11.0	7.4	4.7	5.1	12.0	8.8
EM1	4.2	4.8	8.9	7.0	4.6	5.9	9.5	7.8
EM2	4.5	4.7	9.4	6.4	4.5	5.0	7.6	6.6
EM3	6.5	7.7	11.1	7.7	3.9	4.4	7.8	6.2
VM1	5.7	6.9	8.9	7.4	5.3	8.9	18.0	12.0
VM2	5.5	7.0	8.8	6.9	6.2	6.7	8.8	7.2
MM19	2.8	4.7	12.0	6.8	2.8	3.1	9.4	6.2

Note:

1. S – Surface; M – Middle; B – Bottom; DA – Depth-averaged

Table 8.12 Water Quality Objectives for the Assessment of Elevations in Suspended Solids Concentrations (mg/L) due to Construction Impacts

Station	30% of 90^th Percentile Suspended Solids Concentrations (mg/L) 2001 - 2010
	Dry Season				Wet Season
	S	M	B	DA	S	M	B	DA
JM3	1.4	1.8	2.9	1.9	1.2	1.2	2.0	1.6
JM4	1.4	1.9	3.3	2.2	1.4	1.5	3.6	2.6
EM1	1.3	1.4	2.7	2.1	1.4	1.8	2.8	2.3
EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
VM1	1.7	2.1	2.7	2.2	1.6	2.7	5.4	3.6
VM2	1.7	2.1	2.6	2.1	1.9	2.0	2.7	2.2
MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9

Note:

1. S – Surface; M – Middle; B – Bottom; DA – Depth-averaged

8.5.2.3 In the current study, rather than averaging the 90^th percentile concentrations over the whole area which could be impacted by the construction works, it is proposed to assign each sensitive receiver to the nearest EPD water quality monitoring station and to set the WQO at each station as 30% of the 90^th percentile at that station.

8.5.2.4 Based upon the values detailed in Table 8.12 above, each specific point/sensitive receiver has been assigned a specific WQO for suspended solids, as detailed in Table 8.13.

Table 8.13 Allowable SS Elevation for Water Quality Sensitive Receivers

Observation Points	Associated EPD Station	WQO/WQC (mg/L)
		Dry Season				Wet Season
		S	M	B	DA	S	M	B	DA
SWI1	JM3	1.4	1.8	2.9	1.9	1.2	1.2	2.0	1.6
SWI2	VM1	1.7	2.1	2.7	2.2	1.6	2.7	5.4	3.6
SWI3	VM2	1.7	2.1	2.6	2.1	1.9	2.0	2.7	2.2
SWI4	VM1	1.7	2.1	2.7	2.2	1.6	2.7	5.4	3.6
SWI5	VM2	1.7	2.1	2.6	2.1	1.9	2.0	2.7	2.2
SWI6	VM2	1.7	2.1	2.6	2.1	1.9	2.0	2.7	2.2
SWI7	VM1	1.7	2.1	2.7	2.2	1.6	2.7	5.4	3.6
SWI8	EM1	1.3	1.4	2.7	2.1	1.4	1.8	2.8	2.3
SWI9	EM1	1.3	1.4	2.7	2.1	1.4	1.8	2.8	2.3
SWI10	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
CWI1	VM1	1.7	2.1	2.7	2.2	1.6	2.7	5.4	3.6
CWI2	EM1	1.3	1.4	2.7	2.1	1.4	1.8	2.8	2.3
CC1	JM4	1.4	1.9	3.3	2.2	1.4	1.5	3.6	2.6
CC2	JM3	1.4	1.8	2.9	1.9	1.2	1.2	2.0	1.6
CC3	JM3	1.4	1.8	2.9	1.9	1.2	1.2	2.0	1.6
CC4	JM4	1.4	1.9	3.3	2.2	1.4	1.5	3.6	2.6
CC5	EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
CC6	EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
CC7	EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
CC8	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
CC9	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
CC10	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
CC11	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
CC12	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
CC13	JM3	1.4	1.8	2.9	1.9	1.2	1.2	2.0	1.6
SS1	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
SS2	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
FCZ1	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
FCZ2	EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
AM1	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
AM2	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
AM3	EM2	1.4	1.4	2.8	1.9	1.3	1.5	2.3	2.0
GB1	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
GB2	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
GB3	EM3	2.0	2.3	3.3	2.3	1.2	1.3	2.4	1.9
GB4	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9
GB5	MM19	0.8	1.4	3.6	2.0	0.8	0.9	2.8	1.9

Note:

S – Surface Layer, M – Middle Layer, B – Bottom Layer, DA – Depth Averaged

Criteria for Seawater Intakes

8.5.2.5 In addition to the general WQO described above, other beneficial uses of the coastal waters, for example, fish culture zones and seawater abstraction pumping stations, have specific limit levels on the absolute maximum suspended solids concentrations at the intake points.

8.5.2.6 The Water Quality Objectives of Sea Water for Flushing Supply (at intake point) issued by the Water Supplies Department (WSD) specify the criteria for assessing the water quality impacts on WSD’s seawater intakes. Table 8.14 tabulates a list of the criteria.

Table 8.14 WSD’s Water Quality Criteria for Flushing Water at Sea Water Intakes

Parameter	Concentration (mg/L)
Colour (H.U.)	< 20
Turbidity (N.T.U.)	< 10
Threshold Odour No.	< 100
Ammonia Nitrogen	< 1
Suspended Solids	< 10
Dissolved Oxygen	> 2
Biological Oxygen Demand	< 10
Synthetic Detergents	< 5
E. coli 100 ml	< 20,000

8.5.2.7 According to the EIA-TKOFS, no specific requirement on seawater quality was imposed at the cooling water intakes for both Dairy Farm Ice Plant and Pamela Youde Nethersole Eastern Hospital. Thus, the WQO was adopted to these cooling water intakes.

Criteria for Coral Sites

8.5.2.8 Deposition of fine sediment in ecologically sensitive areas including coral sites could also have an adverse impact on the marine ecosystem. In previous studies (Binnie 1996, Meinhardt 2007, Mouchel 2002), an indicator level above which sustained deposition could harm sediment sensitive hermatypic corals of 200g/m²/day has been used. Typical soft corals in the north western coastal waters where the sediment regime is more dynamic than in other parts of Hong Kong’s coastal waters are expected to be even more tolerant of deposition. In a recent study in Tolo Harbour and north eastern waters (ERM 2003), an impact criterion of 100g/m²/day has been used for eastern waters and this criterion has been adopted in the current study.

SS Criterion for Fish Cultural Zone (FCZ)

8.5.2.9 The AFCD consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment (2001) suggests a maximum suspended solid (SS) concentration of 50mg/L for protecting the local marine fisheries resources in terms of their short-term acute effects.

Assessment Criteria for Heavy Metals and Trace Organics

8.5.2.10 Elutriate tests were conducted to estimate the amount of pollutants that would be released into the water during seawall excavation and filling. However, there are no relevant standards in Hong Kong for assessment of acceptable concentrations of heavy metals and micro-pollutants in marine water.

8.5.2.11 There is no existing legislation or guideline for individual heavy metals and trace organics (PCBs, PAHs and TBT) in Hong Kong waters. According to the common practices in the past EIA studies, a conservative selection was made by comparing the standards of EU and USA. The lowest values from various international standards have been adopted as the assessment criteria. The adopted criteria for heavy metals and trace organics are presented in Table 8.15.

Table 8.15 Proposed Assessment Criteria for Heavy Metal and Trace Organics

Heavy Metal/Trace Organics	Proposed Criteria (mg/l)	Reference
Arsenic	25	2
Cadmium	2.5	2
Chromium	15	2
Copper	5	2
Lead	25	2
Mercury	0.3	2
Nickel	30	2
Silver	1.9	3
Zinc	40	2
Total PAHs	3.0	4, 6
PCBs	0.3	1, 5
TBT	0.01	3

References:

(1) Proposed Marine Water Quality Standards of EU Shellfish Waters Directive (79/923/EEC).

(2) The European Union Water Quality Standards.

(3) USEPA National Recommended Water Quality Criteria, Criterion Continuous Concentration.

(4) Australian Water Quality Guidelines for Fresh and Marine Waters.

(5) EIA of Hong Kong Zhuhai Macro Bridge Hong Kong Boundary Crossing Facilities (EIA-173/2009).

(6) EIA of Hong Kong Offshore Windfarm in Southern Waters (EIA-167/2009).

8.5.3 Modeling Parameters

Grid Layout and Bathymetry Schematisation

8.5.3.1 The grid layout of Junk Bay Model is shown in Drawing No. 209506/EIA/WQ/002. In the Junk Bay Model, finer grids have been made in the vicinity of Junk Bay. Coarser grids have been made in the region far away from the CBL in order to maintain a reasonable total grid number in the refined grid model.

8.5.3.2 The Junk Bay Model consists of 2,971 active grid cells. The smallest grid is inside Junk Bay and is less than 50m. The grid sizes are comparatively larger at the open boundaries of the model and the largest grid is about 650m x 500m.

8.5.3.3 The reference level of the model is the Principal Datum Hong Kong and the depth data is relative to this datum. The bathymetry schematisation of the Junk Bay Model, which was based on the depth data from the Update Model, is shown in Drawing No. 209506/EIA/WQ/003.

Simulation Period

8.5.3.4 The simulation period for this modeling exercise is the same as that adopted in the EIA-TKOFS, which covers a duration of 15 days spring-neap tidal cycle. The simulation period were as follows:

· Dry Season: 9 Feb 1996 15:00 to 24 Feb 1996 15:00

· Wet Season: 31 May 2003 12:00 to 15 Jun 2003 12:00

Modeling Scenarios

Construction Phase

8.5.3.5 Potential water quality impact will be due to excavation of marine sediment. Marine excavators with cage type silt curtain will be used to remove the marine deposits to reach a suitable depth and ground layer for the construction of pile caps. Excavated materials will be placed into barges for transport to disposal or reuse sites in accordance with the regulations.

8.5.3.6 Appendix 8.1 shows the comparison of sediment loss rate of CBL and all relevant concurrent projects. In considering the highway connectivity, CBL and TKO-LT will be considered together in the model run as the worst scenario. Cumulative impacts with TKO-LT Tunnel, offshore windfarm and T2 were taken into account and the modeling scenarios for construction phase is described below:

· Scenario 1a – CBL and TKO-LT Tunnel Marine Works (Item 1, 2, 3, 5 and 23 in App 8.1)

· Scenario 1c – CBL and TKO-LT Tunnel Marine Works (Item 1, 2, 3, 5 and 23 in App 8.1) with cumulative projects (Item 17 to 20 & 24 to 26 in App 8.1) (N.B. Although there might be no concurrent works with those projects, Scenario 1c is done to allow hypothesis and potential programme change.)

Operational Phase

8.5.3.7 Changes in hydraulic friction may lead to long-term impacts on the hydrodynamic and water quality conditions. In order to compare the impact on flow regime with and without the project, two modeling scenarios were conducted:

· Scenario 2a – Ultimate Scenario (with CBL piers and TKO-LT Tunnel Reclamation)

· Scenario 2b – Ultimate Scenario (Do-nothing)

Meteorological Conditions

8.5.3.8 The wind conditions adopted in the hydrodynamic simulation are 5m/s NE for the dry season and 5 m/s SW for the wet season. The horizontal eddy viscosity and diffusivity to be used are 1m²/s. The values for vertical eddy viscosity and diffusivity were computed using the k-e model. For the vertical eddy viscosity, a minimum value is set at 5 x 10^-5 m²/s.

8.5.3.9 The ambient environmental conditions including solar surface radiation and water temperature are closely linked to the process of water quality changes. Meteorological forcing including solar surface radiation and water temperature are required to define in the model for water quality simulation.

8.5.3.10 Solar radiation is recorded only at King’s Park station by Hong Kong Observatory. The monthly averaged solar radiation was calculated based on the hourly data recorded at this station. Average values of solar radiation for the simulation period were adopted in the model.

8.5.3.11 The ambient water temperature were determined based on the EPD routine monitoring data collected within the Hong Kong Waters. Average water temperature values for both dry and wet seasons were adopted in the water quality model.

Initial Conditions

8.5.3.12 Hydrodynamic computations were first carried out using the Update Model. A restart file from previous hydrodynamic computations was then used to provide initial conditions to the Update Model. The initial conditions for the Junk Bay Model were selected to be the same as those for the Update Model. This was done by using a utility program to map the information contained in the restart file of the Update Model to the restart file of the Junk Bay model.

Open Boundary Conditions

8.5.3.13 The open boundary conditions of Junk Bay Model were regenerated through the nesting process from the Update Model. The coastline and additional pier friction in Update Model were revised based on the projects listed in Table 8.8.

8.5.3.14 During the nesting process, both the water level and velocity boundaries were defined in the Junk Bay Model for both dry and wet seasons. As the Update Model covers the discharges from the major Pearl River estuaries, which include Humen, Jiaomen, Hongqili, Hengmen, Muodaomen and Aimen, the influences on hydrodynamics due to the discharges from Pearl River estuaries were therefore incorporated into the Junk Bay Model.

Sediment Plume

8.5.3.15 Delf3D-WAQ module was used to model dispersion of sediment during excavation activities. The settling velocity adopted in the Junk Bay Model is 0.5mm/s. The hydrodynamic conditions generated from the Delf3D-FLOW module provided basic hydrodynamic information for modeling of sediment plume dispersion. The processes of settling of sediment particles and exchange of sediment particles between the water column and the seabed govern the sediment transport.

8.5.3.16 Erosion and deposition in the water quality model are defined in terms of a critical stress for deposition above which no deposition can take place and a critical stress for erosion above which erosion can take place. The critical stress for deposition was set at 0.2N/m² while the water depth of 0.2m was selected as the minimum depth in which deposition can take place. The critical stress for erosion was set at 0.3N/m² which is applicable to relatively soft new deposits with a density of around 200kg/m³ (HWR, 1993) and typically applied in Hong Kong (e.g., HZMB (EIA 173/2009), To Kwa Wan Gas Pipeline (EIA 182/2010), etc).

8.5.3.17 The deposition rate and erosion rate were calculated using the following equations:

(1) Bed Shear Stress (t) < Critical Shear Stress for Deposition (t_d = 0.2 Pascal)

Deposition rate = W_s C_b (1 - t / t_d)

where: W_s = settling velocity (= 0.5 mm/s); and C_b = bottom layer SS concentration

(2) Bed Shear Stress (t) > Critical Shear Stress for Erosion (t_e = 0.3 Pascal)

Erosion rate = Re (t / t_e – 1)

where: Re = erosion coefficient (= 0.0002 kg/m²/s).

(3) Water depth of 0.2m has been selected as the minimum depth in which deposition can take place.

8.5.3.18 No open sea dredging will be required. Excavation activities will be carried out during the construction of pier foundations and within a cofferdam. Under normal condition there will be no contact with seawater when the construction activities were within the cofferdam and water quality impact is negligible. A sediment loss of 25kg per unit excavated material for excavation activities was adopted. Silt curtain will normally be adopted to mitigate the potential water quality impact. The effectiveness of silt curtain is summarized in Table 8.16. Sediment loss reduction efficiency for excavation works within the cofferdam is much higher than all types of silt curtains since there will be no contact with seawater under normal condition. In conservative approach, 80% is adopted.

Table 8-16 Summary Table of Loss Reductions from Silt Curtain Configurations

Mitigation Measures	Loss Reduction Factor	Remark
Excavation with cage type silt curtain (1)	80%	Approved HKBCF EIA (EIA-173/2009)
Floating Single Silt Curtain (2)	75%	Approved HKBCF EIA (EIA-173/2009)
Filling Behind Seawall (3)	80%	Approved HKBCF EIA (EIA-173/2009)
Combined Reduction (1+2)	95%	Approved HKBCF EIA (EIA-173/2009)
Combined Reduction (2+3)	95%

Note [1]: Before construction, the contactor shall conduct field measurement before construction to re-confirm the efficiency of the silt curtain. This requirement will be incorporated into the particular specification.

Sediment Disposal

8.5.3.19 Disposal of sediment during construction in Hong Kong Water would be made according to ETWB TC 34/2002. It is anticipated that the daily excavated quantity is small and the disposal site in Hong Kong may have enough capacity for the sediment/mud. Given that the disposal sites (such as East of Ninepins, South Cheung Chau) are far away from the study area, well controlled and monitored, the cumulative impact is hence negligible.

Frictional Loss for Bridge Piers

8.5.3.20 The sizes of bridge piers (including both from CBL and TKO-LT Tunnel) are expected to be small in comparison to the modeling grid sizes. It is not practicable to refine the model grid accordingly as the computation capacity would be overloaded. Additional frictional losses due to bridge piers have been included in the Junk Bay Model by using an add-on function for porous plate in Delft3D-FLOW module.

8.5.3.21 The approach to simulate the frictional loss for bridge piers on current flows has been employed in several EIA studies. The loss terms take the following form:

Loss term in u-direction = { C_loss,u U |<U>| } / { Δx } [m/s²]

Loss term in v-direction = { C_loss,v V |<U>| } / { Δy } [m/s²] (Eq 8.1)

where:

<U> = Velocity vector (u,v) [m/s]

|<U>| = Magnitude of the velocity vector (u²+v²)^1/2 [m/s]

Δx Δy = Grid distances in the u and v coordinate directions [m]

C_loss,u = Loss coefficients in the u-direction

C_loss,v = Loss coefficients in the v-direction

8.5.3.22 This additional friction terms influence the horizontal flow distribution in each model layer according to the current velocity in each model cell. Consequently, these would affect the vertical turbulent exchange indirectly.

8.5.3.23 The bridge piers would also reduce the flow area resulting in local increase in current velocities. This effect is taken into account by calculating the effective flow area (A_eff) (i.e. the original total flow area (A_tot) minus the area blocked by the bridge piers). Using the ratio of the original total flow area to the effective area (a), the increased approach velocity <U_eff> can be calculated by:

A_eff = A_tot – area blocked by piles as seen by the flow

A = A_tot/A_eff

<U_eff> = a ´ <U>

8.5.3.24 The forces due to the flow on a vertical section Δz of a single pier can be described as follows:

F_u = ½ C_d ρ D u_eff |<U_eff>| Δz

F_v = ½ C_d ρ D v_eff |<U_eff>| Δz

where:

F_u = the drag force in u-direction on a pile [N];

F_v = the drag force in v- direction on a pile [N];

C_d = the drag coefficient (»1 in the case of a cylinder in a tidal regime);

ρ = the density of water [kg/m³];

<Ueff> = the effective approach velocity vector (u_eff,v_eff) [m/s];

|<U_eff>| = magnitude of the effective approach velocity (u_eff² + v_eff²)^1/2 [m/s];

D = the diameter of a pier [m]; and

Δz = the length of the vertical section [m].

8.5.3.25 For multiple piers in the same model grid cell, on assuming that the piles under consideration are not in the shadow of each other, the total force on the flow equals to:

F_tot,u = ½ n ´ C_d ρ D u_eff |<U_eff>| Δz

F_tot,v = ½ n ´ C_d ρ D v_eff |<U_eff>| Δz.

where:

n = The number of piers in the control grid cell;

F_tot,_u, F_tot,_v = The total force in the (u,v) coordinate directions [N]

8.5.3.26 Dividing the forces by the mass in the control volume (=ρ Δx Δy Δz) yields the following terms in the u-momentum equation and the v-momentum equation respectively:

Loss term in u-direction = {½ n ´ C_d D u_eff |<U_eff>| } / { Δx ´ Δy }

Loss term in v-direction = {½ n ´ C_d D v_eff |<U_eff>| } / { Δx ´ Δy } (Eq 8.2)

8.5.3.27 Combining Equation (8.1) and Equation (8.2), the loss coefficients for n numbers of piles in the x and y directions are:

C_loss,u = {½ n ´ C_d D ´ a² } / { Δy }

C_loss,v = {½ n ´ C_d D ´ a² } / { Δx }

8.5.3.28 Based on the above calculation, the loss coefficients of piers are 0.29 to 0.69.

Oxygen Depletion

8.5.3.29 The degree of oxygen depletion exerted by a sediment plume is a function of the sediment oxygen demand of the sediment, its concentration in the water column and the rate of oxygen replenishment. For the purposes of this assessment, the impact of the sediment oxygen demand on dissolved oxygen concentrations has been calculated based on 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/day for worse case estimate)

8.5.3.30 An SOD of 16,000mg/kg has been taken with reference to EPD Marine Monitoring data in Year 2010 as a suitably representative value for sediments in Junk Bay (JS2).

8.5.3.31 The analysis using the above equation does not allow for re-aeration which would tend to reduce any impact of the suspended sediment on the water column DO concentrations. The analysis, therefore, tends to be on the conservative side so as not to underestimate the extent of DO depletion. Further, it should be noted that, for sediment in suspension to exert any oxygen demand on the water column will take time and, in that time, the sediment will be transported and mixed/dispersed with oxygenated water. As a result, the oxygen demand and the impact on dissolved oxygen concentrations will diminish as the suspended sediment concentrations decrease.

8.5.3.32 Oxygen depletion is not instantaneous and thus previous studies have assumed that the impact of suspended sediment on dissolved oxygen will depend on tidally averaged suspended sediment concentrations. The previous studies (ERM, 1997) assumed that the oxygen demand would be satisfied at the same rate as the biological demand which equates to a K value of 0.23/day.

8.5.3.33 However for the purposes of this demonstration, the maximum increase in suspended sediment has been used as the basis for the calculation in order to identify the hypothetical worst case. As such, the daily uptake factor, K, in the equation above was set to be equal to 1.0 which indicates instantaneous oxidation of the sediment oxygen demand and represents a worst case to ensure oxidation rates are not underestimated. The resulting calculated dissolved oxygen deficit, therefore, is anticipated to be much larger than that would be experienced in reality.

Model Outputs

8.5.3.34 Statistical analysis of hydrodynamic and water quality changes were conducted at representative indicator points in the study area. The locations of the water quality sensitive receivers and EPD marine water sampling stations are shown in Drawing No. 209506/EIA/WQ/001. Cross sections were put across Junk Bay, Victoria Harbour (North Point to Hung Hom), Lei Yu Mun and Tathong Channel to assess the changes of accumulated flows. The proposed cross sections are shown in Drawing No. 209506/EIA/WQ/004.

8.5.3.35 Suspended solids (SS) and sedimentation rate are the key water quality parameters to be assessed using the Junk Bay Model. The dissolved oxygen depletions were further evaluated based on the SS modeling results.

8.5.3.36 Dry and Wet Seasons results in the form of table, contour plots and time series plots for depth-averaged SS and sedimentation rate at bottom layer were included in the water quality impact assessment. The predicted SS levels at the water quality sensitive receivers summarised in tables to compare with the relevant criteria for compliance check.

8.6 Construction Phase Assessment

8.6.1 Pile Excavation and Filling

8.6.1.1 The main potential impact on water quality arising from this project during the construction phase will be related to disturbances to the seabed and re-suspension of marine sediment, which lead to the potential for physio-chemical changes in the water column. Conventional grab dredgers may release sediment into suspension by the following activities:

· Impact of the grab on the seabed as it is lowered;

· Washing of sediment off the outside of the grab as it is raised through the water column and when it is lowered again after being emptied;

· Leakage of water from the grab as it is hauled above the water surface;

· Spillage of sediment from over-full grabs;

· Loss from grabs which cannot be fully closed due to the presence of debris; and

· Disturbance of the seabed as the closed grab is removed.

8.6.1.2 Sediment excavation for CBL will only be carried out within the pile casing. Closed grab with a maximum size of 5m³ will be used. All the excavation area (i.e. pier locations) will be covered by a cofferdam and separated from the sea. Thus, sediment loss is considered negligible. Nevertheless, water quality modelling was conducted in a conservative side. The sediment loss rate for CBL excavation and filling activities are 25kg/m³ and 5% respectively. These values have been widely used in previous EIA such as Cruise Terminal and Kai Tak Development. The maximum excavation and filling rates and the associated sediment loss rate under the worst scenarios are summarized in Tables 8.17 to 8.18. The detailed calculations of excavation/filling are attached in Appendix 8.1 and the sediment loss locations are presented in Drawing No. 209506/EIA/WQ/005. Although there may not be concurrent CBL+TKO-LT Tunnel excavation/filling with other projects (see Table 8.8), a hypothetical worst scenario is assumed to cater for potential overlapping of CBL+TKO-LT Tunnel excavation/filling with T2 and Windfarm due to programme change. The assessment has thus been based on worst case scenario in terms of source location and work program.

Table 8.17 Summary of Excavation/Filling Rate and Sediment Loss Rate under the Worst Scenario (Scenario 1a, CBL and TKO-LT Tunnel Only)

Project	Excavation / Filling Activities	Description	Production Rate	Sediment Loss Rate
CBL	Excavating Main Bridge Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Excavating Eastern Approach Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Excavating Western Approach Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Filling	1 trip per day with floating single silt curtain	769 m^3/event	0.32 kg/event
TKO-LT Tunnel	Reclamation Filling	3 trips per day with floating single silt curtain and behind seawall	1000 m^3/event x 3 trips	0.11 kg/s

Table 8.18 Summary of Excavation/Filling Rate and Sediment Loss Rate under the Worst Scenario (Scenario 1c, Hypothetical worst case scenario)

Project	Excavation / Filling Activities	Description	Production Rate	Sediment Loss Rate
CBL	Excavation Main Bridge Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Excavating Eastern Approach Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Excavating Western Approach Piles / Pile Caps	1 excavator (with cage type silt curtain), plus floating single silt curtain	400 m^3/day	0.06 kg/s
CBL	Filling Eastern Approach	1 trip per day with floating single silt curtain	769 m^3/event	0.32 kg/event
TKO-LT Tunnel	Reclamation Filling	3 trips per day with floating single silt curtain and behind seawall	1000 m^3/event x 3 trips	0.11 kg/s
Windfarm	Dredging at P1 – cable	2 grab dredgers with floating single silt curtain	6,300 m^3/day	0.455 kg/s x 2 dredgers
Windfarm	Jetting – cable	Moving at 150 m/hr	-	18.43 kg/s
T2^[1]	Dredging	1 grab dredger with floating single silt curtain	8,000 m^3/day	0.93 kg/s
T2^[1]	Filling	-	9,000 m^3/day	0.83 kg/s

Note:

[1] According to the approved EIA reports for Cruise Terminal (EIA-138-2007) and Submarine Gas Pipeline (EIA-182/2010), plume from T2 project will be localised in Kai Tak Approach channel and will not encroach to Junk Bay. Furthermore, according to the latest information from the T2 project team, the T2 tunnel is now envisaged as TBM method. Cumulative impact is taken as a conservative approach.

8.6.1.3 The sediment loss locations (Drawing No. 209506/EIA/WQ/005) have been selected as the worst case scenario[1] for the following reasons:

· CBL Emission: Emission point 1 and 2 has been selected at the largest pier location (Main Bridge Pier Pylon A and B) where the longer dredging period is anticipated. Emission point 3 has been based on construction separation constraint and closest to SWI1.

· TKO-LT Tunnel Emission: Emission point 23 has been selected at the location of seawall opening as worst scenario.

· Wind Farm Emission: Emission point 24 and 25 have been selected according to the representative locations in the EIA-Wind farm.

Suspended Solids

8.6.1.4 The predicted SS extents, sedimentation rates and time series plots are shown in Appendix 8.2. According to the modeling results of Scenario 1a, it is observed that the plume due to CBL and TKO-LT Tunnel project is highly localised. The envelope of 1 mg/L SS elevation due to CBL and TKO-LT Tunnel project did not reach the coastal areas (Drawings S1a-SS-Dry-Map and S1a-SS-Wet-Map of Appendix 8.2) and the affected WSR due to CBL project involves CC1 to CC3, CC13 and SWI1 only. Impact to other WSRs such as fish culture zones outside Junk Bay is not anticipated.

8.6.1.5 The predicted maximum elevations in SS at selected observation points are summarised in Tables 8.19 to 8.20. A full compliance of SS levels at identified WSRs was predicted due to CBL and TKO-LT Tunnel project (Scenario 1a) and with cumulative projects (Scenario 1c).

Table 8.19 Predicted Maximum SS (mg/L) Elevations (Dry Season)

WSR	Scenario 1a				Scenario 1c				WQO/WQC				Compliance to WQO/WQC
	S	M	B	DA	S	M	B	DA	S	M	B	DA
SWI1	0.1	0.1	0.2	0.1	0.2	0.4	0.6	0.4	1.4	1.8	2.9	1.9	Yes
CC1	0.0	0.0	0.0	0.0	0.2	0.3	0.4	0.3	1.4	1.9	3.3	2.2	Yes
CC2	0.1	0.1	0.1	0.1	0.1	0.2	0.3	0.2	1.4	1.8	2.9	1.9	Yes
CC3	0.1	0.1	0.2	0.1	0.1	0.2	0.3	0.2	1.4	1.8	2.9	1.9	Yes
CC4	0.1	0.1	0.1	0.1	0.3	0.4	0.6	0.4	1.4	1.8	2.9	1.9	Yes
CC13	0.1	0.2	0.2	0.2	0.3	0.5	0.5	0.5	1.4	1.8	2.9	1.9	Yes

Notes:

(1) WQO = Water Quality Objective; WQC = Water Quality Criteria.

(2) Grey cell = Values with WQO/WQC exceedances.

(3) S – Surface Layer, M – Middle Layer; B – Bottom Layer; DA – Depth Averaged.

(4) Brackets shows the percentage of exceedance period

Table 8.20 Predicted Maximum SS (mg/L) Elevations (Wet Season)

WSR	Scenario 1a				Scenario 1c				WQO/WQC				Compliance to WQO/WQC
	S	M	B	DA	S	M	B	DA	S	M	B	DA
SWI1	0.0	0.2	0.4	0.2	0.1	0.2	0.6	0.2	1.2	1.2	2.0	1.6	Yes
CC1	0.0	0.2	0.3	0.2	0.3	0.5	0.5	0.5	1.4	1.5	3.6	2.6	Yes
CC2	0.3	0.5	0.5	0.3	0.5	1.0	1.5	1.0	1.2	1.2	2.0	1.6	Yes
CC3	0.2	0.2	0.4	0.2	0.1	0.5	1.5	0.5	1.2	1.2	2.0	1.6	Yes
CC4	0.0	0.0	0.0	0.0	0.4	0.7	1.5	0.7	1.4	1.8	2.9	1.9	Yes
CC13	0.2	0.3	0.4	0.3	0.3	0.5	1.0	0.5	1.2	1.2	2.0	1.6	Yes

Notes:

(1) WQO = Water Quality Objective; WQC = Water Quality Criteria.

(2) Grey cell = Values with WQO/WQC exceedances.

(3) S – Surface Layer, M – Middle Layer; B – Bottom Layer; DA – Depth Averaged.

(4) Brackets shows the percentage of exceedance period.

8.6.1.6 For WSR SWI1, the maximum SS elevation is 0.6 mg/L. According to Table 8.4, the baseline total SS levels are within 1.7 to 8.6mg/L. Non-compliance with the assessment criteria for WSD’s salt water intakes for flushing water (10 mg/L) in the vicinity is not anticipated.

8.6.1.7 Similar to the SS elevations, the plume of daily sedimentation rates due to CBL and TKO-LT Tunnel project is highly localised (Scenario S1a). The envelope of 20g/m²/day due to CBL and TKO-LT Tunnel project is constrained within Junk Bay (Drawings S1a-Sed-Dry-Map and S1a-Sed-Wet-Map of Appendix 8.2) and the affected ecological sensitive receivers will be limited to CC1 to CC3 and CC13 only.

8.6.1.8 The predicted maximum daily sedimentation rates at affected ecological sensitive receivers are summarised in Table 8.21. According to the modeling results, it is clear that the predicted daily sedimentation rates due to CBL and TKO-LT Tunnel project (Scenario 1a) and with cumulative impact (Scenario 1c) at all WSRs are well within the criterion of 100 g/m²/day.

Table 8.21 Predicted Maximum Sedimentation Rates

Ecological Sensitive Receivers	Predicted Maximum Sedimentation Rates (g/m^2/day)
	Dry Season		Wet Season
	Scenario 1a	Scenario 1c	Scenario 1a	Scenrio 1c
CC1	0	16	5	20
CC2	4	12	20	50
CC3	6	13	20	55
CC4	3	26	0	62
CC13	10	20	10	48

Notes:

(1) Grey cell = Values exceed the criterion of 100 g/m²/day.

(2) Brackets shows the percentage of exceedance period.

Oxygen Depletion

8.6.1.9 The oxygen depletion exerted by the SS elevation is calculated in Table 8.22 below. It is anticipated that the oxygen depletion at most WSR will be less than 0.02mg/L, which is less a detection limit of 0.1mg/L. Thus the DO depletion of all sensitive receivers will be same as prevailing conditions.

Table 8.22 Predicted Oxygen Depletion (mg/L)

WSR	Scenario 1a				Scenario 1c
	S	M	B	DA	S	M	B	DA
Dry Season
SWI1	0.00	0.00	0.00	0.01	0.00	0.01	0.01	0.01
CC1	0.00	0.00	0.00	0.00	0.00	0.00	0.01	0.00
CC2	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
CC3	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
CC4	0.00	0.00	0.00	0.01	0.00	0.01	0.01	0.01
CC13	0.00	0.00	0.00	0.01	0.00	0.01	0.01	0.01
Wet Season
SWI1	0.00	0.00	0.01	0.00	0.00	0.00	0.01	0.00
CC1	0.00	0.00	0.00	0.00	0.00	0.01	0.01	0.01
CC2	0.00	0.01	0.01	0.00	0.01	0.02	0.02	0.02
CC3	0.00	0.00	0.01	0.00	0.00	0.01	0.02	0.01
CC4	0.00	0.00	0.00	0.00	0.01	0.01	0.02	0.01
CC13	0.00	0.00	0.01	0.00	0.00	0.01	0.02	0.01

Notes:

(1) S – Surface Layer, M – Middle Layer; B – Bottom Layer; DA – Depth Averaged.

Release of Contaminants and Nutrients

8.6.1.10 There is no open sea dredging to be conducted under the CBL project since all marine works will be undertaken within cofferdam. In general, release in contaminants and nutrients should be negligible and much less than open sea dredging with silt curtain.

8.6.1.11 Nevertheless, release of contaminants and nutrients were quantified in a conservative approach. Therefore, elutriate tests were conducted. The details of elutriate test results are summarised in Appendix 8.3 and the highest concentrations with exceedance levels are listed in Table 8.23. The elutriate results for other concurrent projects are presented in Table 8.24.

8.6.1.12 The concentration and dilution factor from dredging points to WSR is determined by tracer simulation. The initial discharge is estimated by first order equation[2]: C(x) = q/DXωπ^0.5. Same approach has been adopted in several previous approved EIA studies[3]. On assuming that the radius of initial release is 10m and an average water depth of about 6 to 9m, the initial dilution within a modelling grid was then calculated.

8.6.1.13 A tracer simulation was then conducted by using Delft3D-WAQ as far field plume dispersion. The total concentrations of contaminants and nutrients due to CBL projects at the affected WSRs are presented in Tables 8.25 and 8.26. The maximum extent of mixing zone and time series plot are presented in Appendix 8.4.

8.6.1.14 According to Tables 8-25 and 8-26, all the calculated concentrations of heavy metals, metalloid, TIN and UIA comply with the proposed criteria. Thus, adverse impacts due to release of contaminants on WSRs is not anticipated for all scenario.

Table 8.23 Elutriate Test Results (for those sampling points with exceedance only)

Sampling Location	Metals (μg/L)				Metalloid (μg/L)	TKN (mg/L)	NH4-N (mg/L)	UIA (mg/L)	NO3-N (mg/L)	TIN (mg/L)	NO2-N (mg/L)	Total P (mg/L)	Ortho-P (mg/L)
	Cr	Cu	Pb	Zn	As
Criteria / Baseline	15	5	25	40	25	0.1675	0.04875	0.021	0.061	0.3	0.0185	0.03	0.01275
VB1 (CBL)	22	57	41	80	33	4.10	3.80	0.21	1.30	4.07	0.02	0.39	0.11
VB2 (CBL)	-	44	61	-	41	-	0.15	-	-	-	0.03	0.23	0.03
VB3 (CBL)	-	71	48	85	26	2.20	2.10	0.12	0.19	2.15	0.02	0.34	0.07
VB4 (CBL)	-	41	38	61	37	3.60	2.70	0.15	0.21	2.81	0.02	0.38	0.11
VB5 (CBL)	-	43	58	-	38	-	0.12	-	-	-	0.03	0.26	0.03
VB6 (CBL)	-	43	58	-	43	-	0.13	-	-	-	0.03	0.33	0.03
VB7 (CBL)	-	40	39	-	34	4.10	4.10	0.23	0.77	4.29	0.04	0.65	0.13
VB8 (CBL)	-	42	61	-	48	-	0.10	-	-	-	0.03	0.26	0.03
VB9 (CBL)	-	42	57	-	44	-	0.16	-	0.13	-	0.03	0.54	0.03
VB11 (CBL)	-	45	55	-	42	-	0.22	-	-	-	0.03	0.53	0.03
VB12 (CBL)	-	44	62	-	43	-	0.25	-	-	-	0.03	0.57	0.03
Maximum	22	71	62	85	48	4.1	4.1	0.23	1.3	4.29	0.04	0.65	0.13

Table 8.24 Elutriate Test Results for Concurrent Projects

	Metals (μg/L)				Metalloid (μg/L)	UIA (mg/L)	TIN (mg/L)	Reference
	Cr	Cu	Pb	Zn	As
Windfarm (P1)	^[1]	^[1]	^[1]	^[1]	72.7	^[1]	^[1]	Windfarm EIA
Windfarm (P2)	^[1]	^[1]	^[1]	^[1]	104	^[1]	^[1]	Windfarm EIA
Windfarm (trench)	^[1]	^[1]	^[1]	^[1]	98.9	^[1]	^[1]	Windfarm EIA

Note:

(1) Data is far away less than the proposed criteria and thus not taken into account.

(2) According to the approved EIA reports for Cruise Terminal (EIA-138-2007) and Submarine Gas Pipeline (EIA-182/2010), plume from T2 project will be localised in Kai Tak Approach channel and will not encroach to Junk Bay. Thus, elutriate results in T2 is not taken into account.

Table 8.25 Modeling Results for Contaminants (Depth Averaged) (Scenario 1a)

	Dry Season							Wet Season
	Metals (μg/L)				Metalloid (μg/L)	UIA^[1][2] (mg/L)	TIN^[1][2] (mg/L)	Metals (μg/L)				Metalloid (μg/L)	UIA^[1][2] (mg/L)	TIN^[1][2] (mg/L)
	Cr	Cu	Pb	Zn	As			Cr	Cu	Pb	Zn	As
Criteria	15	5	25	40	25	0.021	0.3	15	5	25	40	25	0.021	0.3
SWI1	1	2.0	2	3	3	0.010	0.26	0	1.3	2	2	1	0.006	0.20
CC1	0	0.3	0	0	0	0.003	0.15	0	0.7	1	1	1	0.005	0.17
CC2	0	0.5	0	1	0	0.005	0.16	0	1.0	2	2	1	0.006	0.18
CC3	0	0.9	2	2	1	0.009	0.18	0	0.7	1	1	0	0.005	0.18
CC4	0	1.3	1	2	1	0.006	0.21	0	0.1	0	0	0	0.002	0.14
CC13	0	0.7	1	2	1	0.010	0.18	0	1.3	1	1	1	0.006	0.18

Note:

(1) For nutrient, WQO criteria is only applicable to TIN and UIA, thus this table only presents these parameters.

(2) Include baseline levels.

Table 8.26 Modeling Results for Contaminants (Depth Averaged, incl background levels) (Scenario 1c)

	Dry Season							Wet Season
	Metals (μg/L)				Metalloid (μg/L)	UIA^[1][2] (mg/L)	TIN^[1][2] (mg/L)	Metals (μg/L)				Metalloid (μg/L)	UIA^[1][2] (mg/L)	TIN^[1][2] (mg/L)
	Cr	Cu	Pb	Zn	As			Cr	Cu	Pb	Zn	As
Criteria	15	5	25	40	25	0.021	0.3	15	5	25	40	25	0.021	0.3
SWI1	^[3]	^[3]	^[3]	^[3]	3	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]
CC1	^[3]	^[3]	^[3]	^[3]	1	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]
CC2	^[3]	^[3]	^[3]	^[3]	1	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]
CC3	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]
CC4	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	1	^[3]	^[3]
CC13	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]	^[3]	^[3]	^[3]	^[3]	2	^[3]	^[3]

Note:

(1) For nutrient, WQO criteria is only applicable to TIN and UIA, thus this table only presents these parameters.

(2) Include baseline levels.

(3) Refer to Table 8.24, no cumulative impact is anticipated for this parameters. Results for Scenario 1c is anticipated to be identical to Scenario 1a.

8.6.2 Construction Site Runoff

8.6.2.1 The construction site runoff comprises the following:

· Runoff and erosion from site surfaces, earth working areas and stockpiles;

· Wash water from dust suppression sprays and wheel washing facilities; and

· Fuel, oil, solvents and lubricants from maintenance of construction machinery and equipment.

8.6.2.2 Construction runoff may cause physical, biological and chemical effects. The physical effects include potential blockage of drainage channels and increase of SS levels in Junk Bay. Runoff containing significant amounts of concrete and cement-derived material may cause primary chemical effects such as increasing turbidity and discoloration, elevation in pH, and accretion of solids. A number of secondary effects may also result in toxic effects to water biota due to elevated pH values, and reduced decay rates of faecal micro-organisms and photosynthetic rate due to the decreased light penetration. Mitigation measures will be in place to control runoff.

8.6.3 Sewage from Workforce

8.6.3.1 Sewage effluents will arise from the sanitary facilities provided for the on-site construction workforce. The characteristics of sewage would include high levels of BOD₅, Ammonia and E. coli counts. Since portable chemical toilets and sewage holding tank will be provided, no adverse water quality impact is anticipated.

8.6.4 Mitigation Measures

Dredging and Filling

8.6.4.1 No exceedance of SS, sedimentations, DO depletion and release of contaminants were anticipated under both Scenario 1a (CBL+TKO-LT Tunnel dredging/filling) and Scenario 1c (CBL+TKO-LT Tunnel dredging/filling and cumulative projects). Non-compliance with the assessment criteria for WSD’s salt water intakes for flushing water (10 mg/L) and any Fish Culture Zone in the vicinity is not anticipated either. Although the interface of the marine works for CBL project with T2 is anticipated, the plume from CBL was well confined in Junk Bay area and superpositions of plume with T2 is not anticipated (refer to Drawings S1a-SS-Dry-Map, S1a-SS-Wet-Map, S1a-Sed-Dry-Map and S1a-Sed-Wet-Map of Appendix 8.2).

8.6.4.2 To further protect WSRs and ensure the effectiveness of mitigation measures, it is recommended to monitor the SS and TIN during construction phase under the EM&A programme.

8.6.4.3 Pile excavation works operations should be undertaken in such a manner as to minimise resuspension of sediments. Standard good site practice measures should, therefore, be implemented including the following requirements which should be written into the contract.

· all excavation works shall be conducted within the cofferdam (Drawing No. 209506/EIA/WQ/006);

· floating single silt curtain shall be employed for all marine works;

· mechanical grabs (with a maximum size of 5m³) shall be designed and maintained to avoid spillage and should seal tightly while being lifted;

· barges and hopper excavators shall have tight fitting seals to their bottom openings to prevent leakage of material;

· any pipe leakages shall be repaired quickly. Plant should not be operated with leaking pipes;

· loading of barges and hoppers shall be controlled to prevent splashing of excavated material to the surrounding water. Barges or hoppers shall not be filled to a level which will cause overflow of materials or pollution of water during loading or transportation;

· excess material shall be cleaned from the decks and exposed fittings of barges and hopper excavators before the vessel is moved;

· 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; and

· 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.

Construction Site Runoff

8.6.4.4 In accordance with the Practice Note for Professional Persons on Construction Site Drainage, Environmental Protection Department, 1994 (ProPECC PN 1/94), construction phase mitigation measures, where appropriate, should include the following:

· The design of efficient silt removal facilities should be based on the guidelines in Appendix A1 of ProPECC PN 1/94. The detailed design of the sand/silt traps should be undertaken by the contractor prior to the commencement of construction.

· Open stockpiles of construction materials (for example, aggregates, sand and fill material) of more than 50m3 should be covered with tarpaulin or similar fabric during rainstorms. Measures should be taken to prevent the washing away of construction materials, soil, silt or debris into any marine water bodies.

· 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 facilities should be provided at every construction site exit where practicable. Wash-water should have sand and silt settled out and removed at least on a weekly basis 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.

· Construction solid waste, debris and rubbish on site should be collected, handled and disposed of properly to avoid water quality impacts.

· All fuel tanks and storage areas should be provided with locks and sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank to prevent spilled fuel oils from reaching water sensitive receivers nearby.

· Regular environmental audit on the construction site should be carried out in order to prevent any malpractices. Notices should be posted at conspicuous locations to remind the workers not to discharge any sewage or wastewater into the meander, wetlands and fish ponds. 

8.6.4.5 By adopting the above mitigation measures with best management practices, it is anticipated that the impacts of construction site runoff from the construction site will be reduced to satisfactory levels before discharges.

Sewage from Workforce

8.6.4.6 Portable chemical toilets and sewage holding tanks should be provided for handling the construction sewage generated by the workforce. A licensed contractor should be employed to provide appropriate and adequate portable toilets and be responsible for appropriate disposal and maintenance.

8.6.4.7 Notices should be posted at conspicuous locations to remind the workers not to discharge any sewage or wastewater into the nearby environment during the construction phase of the Project. Regular environmental audit on the construction site should be conducted in order to provide an effective control of any malpractices and achieve continual improvement of environmental performance on site. It is anticipated that sewage generation during the construction phase of the Project would not cause water quality impact after undertaking all required measures.

8.7 Operational Phase Assessment

8.7.1 Change of Hydrodynamic Regime

8.7.1.1 The key operational phase issues are related to the change in hydraulic friction and coastline due to CBL and TKO-LT Tunnel would have impact on the hydrodynamic regime within the Junk Bay WCZ, Eastern Buffer WCZ and Victoria Harbour WCZ. The key issues are as follows:

· reduction or acceleration of tidal flows resulting in siltation or erosion of seabed and scour hole formation;

· poorly flushed embayments;

· accumulation of floating debris; and

· increase in siltation and loss of water depth if significant change in hydrodynamic regime predicted.

8.7.1.2 The coastline with and without CBL and TKO-LT Tunnel reclamation is presented in Appendix 8.5. Tidal flows simulations have been undertaken in order to obtain results for:-

· Scenario 2a – Ultimate Scenario (with CBL piers and TKO-LT Tunnel Reclamation)

· Scenario 2b – Ultimate Scenario (Do-nothing)

8.7.1.3 By comparing the results from these simulations, the possible hydrodynamic impacts for the CBL and TKO-LT Tunnel were assessed.

8.7.1.4 The modeling results are presented in Appendix 8.5. The graphical presentations for flow velocity vectors and accumulated flows show an insignificant hydrodynamic impact with and without the CBL and TKO-LT Tunnel.

8.7.1.5 A summary of depth averaged velocities within a whole spring-neap cycle are presented in Table 8.28 for both dry and wet seasons.

Table 8.28 Depth Averaged Velocities in Dry and Wet Season (in m/s)

Locations	Ultimate Scenario (Scenario 2a)	Do-nothing Scenario (Scenario 2b)	Ultimate Scenario (Scenario 2a)	Do-nothing Scenario (Scenario 2b)
	Dry Season		Wet Season
JM3	0.04 (0.01 to 0.08)	0.04 (0.01 to 0.08)	0.08 (0.02 to 0.26)	0.08 (0.02 to 0.26)
JM4	0.15 (0.02 to 0.32)	0.14 (0.02 to 0.32)	0.20 (0.05 to 0.43)	0.20 (0.05 to 0.43)
Seashore outside Ocean Shores (Refer to Appendix 8.5)^[1]	0.01 (0.01 to 0.04)	0.02 (0.01 to 0.04)	0.03 (0.01 to 0.10)	0.04 (0.01 to 0.12)

Notes:

(1) It should be noted that the reduction of current velocities in the seashore outside Ocean Shores were due to TKO-LT Tunnel reclamation but not the CBL project. Nevertheless, the zoom-in figures of current velocities in flood/ebb at this embayed area are presented in Appendix 8.5.

8.7.1.6 As the Junk Bay is already a semi-enclosed water body, the existing flow condition is already limited. Based on the model results there is no significant surface/bottom flow retardation even stagnation of water at the seashore outside Ocean Shores (embayed area formed by TKO-LT Tunnel reclamation) in both dry and wet season.

8.7.1.7 According to the drainage design of Road P2 of TKO-LT Tunnel reclamation, all the stormwater from west TKO will be discharged to the east of Road P2, i.e. open sea of Junk Bay, except a stormwater discharge point was diverted to embayed area formed by TKO-LT Tunnel reclamation. However, the catchment of this stormwater pipe is only 69200m² and the land use is only residential area or park. In ideal case there will be no discharge unless during rainy periods. Nevertheless, there might be minor baseflow in reality and pollutant might be trapped within the embayed area if inadequate flushing capacity.

8.7.1.8 According to the hydrodynamic modelling results in Table 8.28, it is observed that the average velocity within the embayed area will be reduced by 0.01 m/s, compared with the prevailing velocity of 0.01-0.04 m/s and 0.01-0.12 m/s for dry and wet season respectively. Given the small change of average velocity, significant change in flushing capacity is not anticipated. In order to further supplement the interpretation, a drogue track analysis has been conducted to investigate the residence time of pollutants within the embayed area and the Junk Bay. As a worst scenario consideration, the model assumes the drogue track starting in neap tide under dry season and hourly drogue track is predicted.

8.7.1.9 The modelled hourly drogue track is presented in Appendix 8.6. It is observed that it takes about 3-4 hours for the pollutants to flush out of the embayment and more than 12 hours to flush out of the Junk Bay. As the residence time is relatively short, accumulation of pollutant (e.g. BOD₅ or DO depletion) within the embayed area and the Junky Bay is not anticipated.

8.7.2 Runoff from Road Surfaces

8.7.2.1 During operational phase, vehicle dust, tyre scraps and oils might be washed away from the road surfaces to the nearby marine water environment by surface runoff or road surface cleaning. Therefore, potential water quality impacts may arise from the road runoff discharge during operational phase. Substances such as dust and lubricant oil deposited and accumulated on the road surfaces will be washed into the marine water bodies during rainfall or road cleaning. Measures to mitigate the water quality from road runoff would be required.

8.7.3 Mitigation Measures

Change of Hydrodynamic Regime

8.7.3.1 No significant change in hydrodynamic and water quality regime is anticipated and therefore no mitigation measure such as maintenance dredging is required.

Runoff from Road Surfaces

8.7.3.2 As a precautionary measure, proper drainage systems with silt traps and oil interceptors should be installed, and maintained and cleaned at regular intervals.

8.8 Residual Impacts

8.8.1.1 No adverse residual water quality impact is anticipated. To further protect the WSRs and to ensure the effectiveness of mitigation measures, it is recommended to monitor the SS during construction phase under the EM&A programme.

8.9 Conclusion

8.9.1.1 During construction phase, it is anticipated that the SS elevation, sedimentations and DO depletion due to CBL+TKO-LT Tunnel dredging/filling works and all concurrent projects will be well within the proposed criteria.

8.9.1.2 During operational phase, an insignificant change in hydrodynamic regime is predicted for CBL+TKO-LT Tunnel project. Therefore, the change of water quality regime, which associated with the hydrodynamic impact, is not anticipated.

8.9.1.3 The water quality assessment has been conducted according to Annex 15, Guidelines for Assessment of Water Pollution, of the TM-EIAO. Overall, it is concluded that water quality impacts will comply with Annex 6, Criteria for Evaluating Water Pollution, during both the construction and operational phases of CBL.

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[1] According to the approved EIA reports for Cruise Terminal (EIA-138-2007) and Submarine Gas Pipeline (EIA-182/2010), plume from T2 project will be localised in Kai Tak Approach channel and will not encroach to Junk Bay. Therefore it is not presented in (Drawing No. 20 9506/EIA/WQ/005).

[2] Where C(x) = concentration at distance x from the source, q = sediment loss rate, D = water depth, x = distance from source, ω = diffusion velocity (=0.01 m/s).

[3] Hong Kong Boundary Crossing Facilities (EIA-173/2009), Hong Kong Link Road (EIA-172/2009), Hong Kong Electric’s 132kV cable in Deep Water Bay EIA-065/2001 and Penny’s Bay Theme Park EIA-041/2000.