5. Hydrodynamics and water quality impacts

5.1 Introduction

Brief Project Description

5.1.1 The key elements of the Tseung Kwan O (TKO) further development comprise the Western Coast Road (WCR), the Cross Bay Link (CBL), and the land-based developments at Town Centre South (TCS) and Pak Shing Kok (PSK). A strip of land would be reclaimed under the Project for the WCR along the western shoreline of Junk Bay (Figure 2.35). The CBL bridge alignment is shown in Figure 2.38.

5.1.2 The proposed population in PSK and TCS is around 5,000 and 33,000 including some 9,200 existing population in Bauhina Garden respectively. The population intake for PSK and TCS would commence upon completion of infrastructure around Oct 2010 and May 2010 respectively. WCR and CBL are assumed to be in place around 2016. The construction programme is shown in Appendix 2.2.

5.1.3 It is also proposed under the present Study to use part of the Eastern Channel (EDC) and Junk Bay for recreation uses such as dragon boating, sailing and rowing etc. Figure 5.1 shows the existing drainage systems of the TKO catchment. The boundary of the proposed water recreation zone is shown in Figure 5.1a.

5.1.4 According to the current TKO Outline Zoning Plan (OZP), the existing and currently planned developments would bring the ultimate population up to around 480,000. The further developments proposed under the present Study would trim down the ultimate population at TKO to around 453,000. Table 5.1Table 5.1Table 5.1Table 5.1 summarises the ultimate population for TKO envisaged in the current OZP and in the current development scenario. The ultimate population has taken into account the planned population at TCS and PSK assuming all proposed developments and infrastructures at TKO would be fully utilized.

Table 5.1 Ultimate Population for TKO

Scenario	Residential Population	Commercial Employed Population	Industrial Employed Population	School Place
Ultimate population at TKO under current OZP	484,318	99,629	10,716	67,861
Ultimate population at TKO proposed under the present Study	453,318	99,629	10,716	67,861

Other Project Components with Water Quality Issue

Construction of Northern Cycle Track Footbridge and Southern Footbridge across EDC

5.1.5 The northern footbridge is a cycle track footpath bridge of about 110m long across EDC which also serve as an emergency vehicular access in the event of blockage of Wan Po Road due to serious traffic accident. The southern footbridge will only carry a footway which is also about 110m long. Both bridges are designed without bridge piers locating in the EDC.

Service Reservoir and Pumping Station

5.1.6 A new fresh water supply system comprising a new Pak Shing Kok fresh water pumping station, a new Pak Shing Kok high level fresh water service reservoir and the associated supply and distribution mains, will be constructed under the Project.

Culvert Realignment and Piled Deck at Western Drainage Box Culvert

5.1.7 A section of culvert in Tiu Keng Leng Area 72 would be clashed by the proposed depressed Road P2. This section of culvert will be realigned to avoid such conflict. A piled deck will be constructed at the downstream section of the western drainage box culvert which replaces the existing temporary box culvert to protect the existing tidal gates.

Sewage Pumping Station and Rising Mains

5.1.8 A new sewage pumping station and rising mains are proposed to carry the sewage arising from the recreational development at TKO landfill to the TKO preliminary treatment works. The emergency outfall of the pumping station will be located 500 m away from the TKO saltwater intake. The locations of the emergency bypass and TKO saltwater intake are shown in Figure 5.1b. A standby pump will be provided to minimize the potential water quality impact from sewage overflow.

Key Water Quality Issues

Operational Phase

5.1.9 The change in coastline configuration due to the reclamation for construction of the WCR and the placement of bridge structures for the CBL may change the hydrodynamic regime and water quality in Junk Bay and Victoria Harbour and thus, may adversely affect the nearby water quality and ecological sensitive receivers.

5.1.10 The acceptability of the EDC and Junk Bay for secondary contact recreation have been addressed, in particular the cumulative impact from the potential release of landfill leachate together with other pollutant discharges within the TKO catchment as well as the potential impact in the event of any sewage overflow or emergency bypass from the TKO Preliminary Treatment Works (PTW).

Construction Phase

5.1.11 Key water quality issues associated with the land-based construction would include the impacts from site run-off, sewage from workforce, accidental spillage and discharges of wastewater from various construction activities.

5.1.12 Potential water quality impacts arising from the proposed marine construction works would include:

· Increase of suspended solids concentration due to dredging and filling activities

· Release of contaminants during dredging of marine mud

· Release of suspended solids and contaminants during deep cement mixing (DCM) treatment

· Release of contaminants through vertical band drains during consolidation of reclamation.

5.1.13 Implementation of proper pollution control measures will be important for the construction works at or near box culverts / inland waters in order to prevent construction wastes from entering the storm system.

5.1.14 Groundwater generated from construction works in close proximity to the TKO landfill site boundary may potentially be contaminated by landfill leachate. Potential water quality impacts on the nearby receiving water may arise if the contaminated groundwater is not properly handled.

5.1.15 The performance of the existing and committed sewerage infrastructure under full development condition for the ultimate scenario was assessed and results are presented in Section 6. The results indicate that there are no risks of sewage overflow under various peak flow conditions for the ultimate scenario. The TKOPTW and the Harbour Area Treatment Scheme (HATS) Stage I Tunnel section from TKO to Kwun Tong are considered to be adequate to handle the ultimate catchment flows ⁽[1]⁾. The present Study would not pose any capacity constraint on HATS, as there would be an overall reduction in ultimate population and flows as a consequence of planned further developments.

5.2 Environmental Legislation, Policies, Plans, Standards and Criteria

Environmental Impact Assessment Ordinance (EIAO), Cap.499, S.16

5.2.1 The EIAO-TM is issued by the EPD under Section 16 of the EIAO. It specifies the assessment method and criteria that need to be followed in this Study. Reference sections in the EIAO-TM provide the details of the assessment criteria and guidelines that are relevant to the water quality impact assessment, including:

· Annex 6 Criteria for Evaluating Water Pollution

· Annex 14 Guidelines for Assessment of Water Pollution.

Marine Water Quality Objectives

5.2.2 The Water Pollution Control Ordinance (Cap.358) provides the major statutory framework for the protection and control of water quality in Hong Kong. According to the Ordinance and its subsidiary legislation, Hong Kong waters are divided into ten Water Control Zones (WCZ). Corresponding statements of Water Quality Objectives (WQO) are stipulated for different water regimes (marine waters, inland waters, bathing beaches subzones, secondary contact recreation subzones and fish culture subzones) in the WCZ based on their beneficial uses. A summary of WQOs for Junk Bay, Victoria Harbour and Eastern Buffer WCZs are given in Table 5.2Table 5.2Table 5.2Table 5.2, Table 5.3Table 5.3Table 5.3Table 5.3 and Table 5.4Table 5.4Table 5.4Table 5.4 respectively.

5.2.3 Given the planning intention of the EDC and Junk Bay for water recreation, the E.coli objective of 610 per 100mL for annual geometric mean set under the WPCO for secondary contact recreation should be adopted for the proposed water recreation zone as shown in Figure 5.1a.

Table 5.2 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 5.3 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 (Phases One, Two and Three) Water Control Zone).

Table 5.4 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

Hong Kong Planning Standards and Guidelines (HKPSG)

5.2.4 The HKPSG, Chapter 9 (Environment), provides additional information on regulatory guidelines against water pollution for sensitive uses such as aquaculture and fisheries zones, bathing waters and other contact recreational waters.

Water Supplies Department Water Quality Objectives

5.2.5 Besides the WQO set under the WPCO, the Water Supplies Department (WSD) has also specified a set of seawater quality objectives for water quality at seawater intakes. The list is shown in Table 5.5Table 5.5Table 5.5Table 5.5. The relevant criteria for suspended solids (SS) are the target limit of 10 mg/L.

Table 5.5 WSD Standards at Sea Water Intakes

Parameter (in mg/L unless otherwise stated)	WSD Target Limit
Colour (HU)	< 20
Turbidity (NTU)	< 10
Threshold Odour Number (odour unit)	< 100
Ammoniacal Nitrogen	< 1
Suspended Solids	< 10
Dissolved Oxygen	> 2
Biochemical Oxygen Demand	< 10
Synthetic Detergents	< 5
E. coli (no. / 100 ml)	< 20,000

Cooling Water Intake Standards

5.2.6 Based on the information provided by the individual cooling water intake operators (Dairy Farm Ice Plant and Pamela Youde Nethersole Eastern Hospital), no specific requirement on seawater quality at these two cooling water abstraction points was identified.

Technical Memorandum

5.2.7 Besides setting the WQOs, the WPCO controls effluent discharges into any WCZ through a licensing system. The Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS), issued under Section 21 of the WPCO, gives guidance on permissible effluent discharges based on the type of receiving waters (foul sewers, storm water drains, inland and coastal waters). The limits control the physical, chemical and microbial quality of effluent. Any sewage from the proposed construction activities should comply with the standards for effluent discharged into the foul sewers, inshore waters or marine waters of the Victoria Harbour WCZ and Junk Bay WCZ, shown in Table 1, Table 9a and Table 9b, Table 10a and Table 10b, respectively, of the TM-DSS.

Practice Note

5.2.8 A practice note for professional persons has been issued by the EPD to provide guidelines for handling and disposal of construction site discharges. The ProPECC PN 1/94 “Construction Site Drainage” provides good practice guidelines for dealing with ten types of discharge from a construction site. These include surface runoff, groundwater, boring and drilling water, bentonite slurry, water for testing and sterilisation of water retaining structures and water pipes, wastewater from building construction, acid cleaning, etching and pickling wastewater, and wastewater from site facilities. Practices given in the ProPECC PN 1/94 should be followed as far as possible during construction to minimise the water quality impact due to construction site drainage. For operational stage effluent handling, treatment and disposal, reference should be made to ProPECC PN 5/93.

Assessment Criteria for Coral Impact

5.2.9 According to Pastorok and Bilyard⁽[2]⁾ and Hawker and Connell⁽[3]⁾, a sedimentation rate higher than 0.1 kg/m²/day would introduce moderate to severe impact upon corals. This criterion has been adopted in other recently approved EIA. Detailed assessment criteria for marine ecological sensitive receivers including coral and fish culture zone (FCZ) are provided in Chapters 8 and 9.

SS Criterion for Fish Cultural Zone (FCZ)

5.2.10 Literature reviews indicate that lethal responses had not been reported in adult fish at a SS concentration of below 125 mg/L ⁽[4]⁾. The AFCD consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment ⁽[5]⁾ provides the guideline value for suspended solids (SS) for protection of local marine fisheries resources as given in Table 5.6Table 5.6Table 5.6Table 5.6 below.

Table 5.6 Assessment Criterion for SS for Local Marine Biota and Fisheries Resources

Parameter	Maximum Concentration (mg/L)
Total Suspended Solids	50

5.2.11 The maximum SS concentration value offers protection to short-term acute effects, and thus should be complied with during both the construction and operational phases. A description on legislation for fish cultural zone is presented in Section 9.2.

5.3 Description of the Environment

5.3.1 The marine water quality monitoring data routinely collected by EPD were used to establish the baseline condition. The EPD monitoring stations in Junk Bay WCZ (JM3 and JM4), Eastern Buffer WCZ (EM1 and EM2) and Victoria Harbour WCZ (VM1 and VM2) are shown in Figure 5.2. A summary of EPD monitoring data collected in 2002 and 2003 is presented in Table 5.7, Table 5.8 and Table 5.9 for Junk Bay, Eastern Buffer and Victoria Harbour WCZs representatively. As the Harbour Area Treatment Scheme (HATS) Stage I was commissioned in late 2001, the data shown in Table 5.7, Table 5.8 and Table 5.9 represent the situation after the commissioning of HATS Stage 1.

Table 5.7 Summary Statistics of 2002 and 2003 Marine Water Quality in Junk Bay WCZ

Parameter		EPD Monitoring Station				WPCO WQOs for Junk Bay WCZ(in marine waters)
		JM3		JM4
		2002	2003	2002	2003
Temperature (^oC)		23.7 (17.4 – 27.8)	23.1 (17.2– 27.2)	23.5 (17.4 – 27.7)	22.9 (17.1 – 27.0)	Change due to waste discharges not to exceed 2°C
Salinity (ppt)		32.4 (29.9 – 33.8)	32.9 (30.9– 33.9)	32.6 (30.0 – 33.9)	33.1 (32.2 – 33.8)	Change due to waste discharges not to exceed 10% of ambient
Dissolved Oxygen (DO) (% saturation)		92 (74 – 126)	86 (72 – 115)	89 (72 – 104)	83 (66 – 102)	-
	Bottom	90 (75 – 111)	80 (55 – 101)	88 (71 – 109)	78 (46 – 100)	-
DO (mg/L)		6.5 (5 – 8.3)	6.1 (4.9 – 7.8)	6.3 (4.7 – 7.9)	5.9 (4.4 – 8.1)	Not less 4 mg/L for 90% of the samples
	Bottom	6.4 (4.9 – 7.7)	5.7 (3.9 – 7.9)	6.3 (4.9 – 8.2)	5.6 (3.2 – 7.9)	Not less 2 mg/L for 90% of the samples
pH value		8.0 (7.7 – 8.2)	8.1 (7.9 – 8.3)	8.0 (7.8 – 8.2)	8.1 (7.9 – 8.3)	6.5 - 8.5 (± 0.2 from natural range)
Secchi disc (m)		2.2 (1.0 – 3.5)	2.7 (1.5 – 4.0)	2.0 (1.0 – 3.0)	2.8 (1.6 – 3.7)	-
Turbidity (NTU)		10.2 (6.2 – 16.4)	7.3 (3.2 – 11.5)	11.6 (6.2 – 22.6)	8.1 (5.4 – 11.0)	-
Suspended Solids (SS) (mg/L)		3.6 (1.7 – 5.0)	3.6 (1.7 – 5.8)	5.4 (2.2 – 15.4)	7.3 (1.7 – 38.7)	Not more than 30% increase
Silica (as SiO2) (mg/L)		0.6 (0.2 – 0.9)	0.6 (0.1 – 1.0)	0.6 (0.2 – 0.9)	0.6 (0.2 – 1.0)	-
5-day Biochemical Oxygen Demand (BOD5) (mg/L)		0.9 (0.3 – 2.5)	1.1 (0.4 – 3.1)	0.7 (0.1 – 1.6)	1.1 (0.4 – 3.1)	-
Nitrite Nitrogen (NO2-N) (mg/L)		0.02 (<0.01– 0.04)	0.02 (<0.01– 0.06)	0.02 (<0.01 – 0.04)	0.02 (<0.01 – 0.06)	-
Nitrate Nitrogen (NO3-N) (mg/L)		0.06 (0.02 – 0.19)	0.06 (0.02– 0.12)	0.05 (0.02 – 0.20)	0.05 (0.01 – 0.10)	-
Ammonia Nitrogen (NH3-N) (mg/L)		0.10 (0.02 – 0.23)	0.07 (0.01– 0.19)	0.08 (0.02 – 0.14)	0.05 (0.01 – 0.12)	-
Unionised Ammonia (UIA) (mg/L)		0.004 (0.001 – 0.008)	0.004 (0.001–0.006)	0.003 (0.001 – 0.007)	0.003 (0.001 – 0.005)	Not more than annual average of 0.021 mg/L
Total Inorganic Nitrogen (TIN) (mg/L)		0.18 (0.05 – 0.36)	0.15 (0.09–0.27)	0.15 (0.07 – 0.26)	0.12 (0.05 – 0.20)	Not more than annual water column average of 0.3 mg/L
Total Nitrogen (Total-N) (mg/L)		0.31 (0.15 – 0.50)	0.28 (0.17– 0.41)	0.26 (0.14 – 0.36)	0.24 (0.14 – 0.36)	-
Ortho-Phosphate (Ortho-P) (mg/L)		0.014 (0.002–0.021)	0.017 (0.01– 0.03)	0.012 (0.003 – 0.018)	0.015 (0.01 – 0.02)	-
Total Phosphorus (Total-P) (mg/L)		0.03 (0.02 – 0.04)	0.03 (0.02– 0.04)	0.03 (0.02 – 0.04)	0.03 (0.02 – 0.04)	-
Chlorophyll-a (µg/L)		3.6 (0.9 – 18.6)	3.9 (0.6 – 11.5)	2.3 (1.0 – 6.5)	3.4 (0.6 – 11.4)	-
E. coli (cfu/100 mL)		140 (19 – 1000)	65 (2 – 640)	200 (34 – 2700)	71 (12 – 730)	-
Faecal Coliform (cfu/100 mL)		320 (55 – 1800)	140 (3 – 1600)	450 (66 – 6600)	170 (51 – 1700)	-

Note: 1. Except as specified, data presented are depth-averaged values calculated by taking the means of three depths: Surface, mid-depth, bottom.

2. Data presented are annual arithmetic means of depth-averaged results except for E. coli and faecal coliforms that are annual geometric means.

3. Data in brackets indicate the ranges.

Table 5.8 Summary Statistics of 2002 and 2003 Marine Water Quality in Eastern Buffer WCZ

Parameter		EPD Monitoring Station				WPCO WQOs for Eastern Buffer(in marine waters)
		EM1		EM2
		2002	2003	2002	2003
Temperature (^oC)		23.4 (17.4 – 27.6)	23.0 (17.1– 26.8)	23.4 (17.5 – 27.6)	22.9 (16.9 – 26.9)	Change due to waste discharges not to exceed 2°C
Salinity (ppt)		32.5 (29.7 – 33.9)	32.9 (31.2– 33.8)	32.6 (29.5 – 34.0)	33.0 (30.4 – 34.2)	Change due to waste discharges not to exceed 10% of ambient
Dissolved Oxygen (DO) (% saturation)		86 (69 – 105)	83 (67 – 103)	90 (70 – 111)	83 (59 – 104)	-
	Bottom	88 (66 – 110)	77 (45 – 106)	90 (70 – 115)	78 (43 – 105)	-
DO (mg/L)		6.2 (4.7 – 7.9)	5.9 (4.5 – 8.2)	6.4 (4.7 – 8.3)	5.9 (4.0 – 8.2)	Not less 4 mg/L for 90% of the samples
	Bottom	6.2 (4.6 – 8.2)	5.5 (3.2 – 8.3)	6.4 (4.8 – 8.6)	5.6 (3.0 – 8.3)	Not less 2 mg/L for 90% of the samples
pH value		8.0 (7.8 – 8.2)	8.1 (7.9 – 8.3)	8.0 (7.8 – 8.3)	8.2 (7.9 – 8.3)	6.5 - 8.5 (± 0.2 from natural range)
Secchi disc (m)		2.3 (1.5 – 3.5)	2.9 (1.5 – 4.5)	2.4 (1.5 – 4.2)	2.7 (1.3 – 5.0)	-
Turbidity (NTU)		11.3 (6.3 – 16.1)	7.4 (4.4 – 10.6)	10.5 (5.9 – 15.5)	7.5 (3.9 – 10.0)	-
Suspended Solids (SS) (mg/L)		4.9 (2.4 – 8.7)	3.9 (1.3 – 7.1)	4.1 (1.7 – 7.0)	3.6 (0.9 – 5.6)	Not more than 30% increase
Silica (as SiO2) (mg/L)		0.7 (0.2 – 1.0)	0.6 (0.2 – 1.1)	0.6 (0.2 – 1.0)	0.7 (0.3 – 1.7)	-
5-day Biochemical Oxygen Demand (BOD5) (mg/L)		0.7 (0.1 – 1.7)	0.9 (0.3 – 1.4)	0.6 (0.2 – 1.4)	0.7 (0.3 – 1.2)	-
Nitrite Nitrogen (NO2-N) (mg/L)		0.02 (0.01– 0.06)	0.03 (0.01– 0.12)	0.02 (<0.01 – 0.06)	0.02 (<0.01 – 0.08)	-
Nitrate Nitrogen (NO3-N) (mg/L)		0.07 (0.03 – 0.29)	0.05 (0.01– 0.16)	0.06 (0.01 – 0.29)	0.06 (0.01 – 0.25)	-
Ammonia Nitrogen (NH3-N) (mg/L)		0.08 (0.04 – 0.15)	0.06 (0.01– 0.16)	0.07 (0.03 – 0.15)	0.04 (0.01 – 0.09)	-
Unionised Ammonia (UIA) (mg/L)		0.003 (0.001 – 0.008)	0.003 (<0.001–0.006)	0.003 (0.001 – 0.008)	0.002 (<0.001 – 0.005)	Not more than annual average of 0.021 mg/L
Total Inorganic Nitrogen (TIN) (mg/L)		0.17 (0.10 – 0.38)	0.14 (0.04 – 0.33)	0.14 (0.06 – 0.39)	0.12 (0.03 – 0.36)	Not more than annual water column average of 0.4 mg/L
Total Nitrogen (Total-N) (mg/L)		0.29 (0.19 – 0.52)	0.25 (0.13– 0.43)	0.26 (0.11 – 0.49)	0.22 (0.11 – 0.51)	-
Ortho-Phosphate (Ortho-P) (mg/L)		0.014 (0.003– 0.022)	0.016 (0.01– 0.03)	0.013 (0.003 – 0.029)	0.013 (0.01 – 0.02)	-
Total Phosphorus (Total-P) (mg/L)		0.03 (0.02 – 0.04)	0.03 (0.02– 0.04)	0.03 (0.02 – 0.10)	0.03 (0.02 – 0.04)	-
Chlorophyll-a (µg/L)		2.1 (0.7 – 5.9)	3.2 (0.6 – 8.5)	1.9 (0.8 – 6.2)	2.6 (0.5 – 10.9)	-
E. coli (cfu/100 mL)		280 (45 – 6000)	86 (11 – 1300)	110 (1 – 5000)	16 (1 – 510)	-
Faecal Coliform (cfu/100 mL)		570 (59 – 11000)	200 (22 – 2900)	220 (1 – 9900)	38 (3 – 1200)	-

Note: 1. Except as specified, data presented are depth-averaged values calculated by taking the means of three depths: Surface, mid-depth, bottom.

2. Data presented are annual arithmetic means of depth-averaged results except for E. coli and faecal coliforms that are annual geometric means.

3. Data in brackets indicate the ranges.

Table 5.9 Summary Statistics of 2002 and 2003 Marine Water Quality in Victoria Harbour WCZ

Parameter		EPD Monitoring Station				WPCO WQOs for Victoria Harbour WCZ (in marine waters)
		VM1		VM2
		2002	2003	2002	2003
Temperature (^oC)		22.8 (16.2 – 27.2)	23.0 (17.0– 26.6)	22.9 (16.2 – 27.4)	23.2 (16.9 – 27.1)	Change due to waste discharges not to exceed 2°C
Salinity (ppt)		32.7 (31.4 – 33.4)	33.0 (32.5– 33.6)	32.4 (30.4 – 33.4)	32.6 (31.6 – 33.7)	Change due to waste discharges not to exceed 10% of ambient
Dissolved Oxygen (DO) (% saturation)		82 (60 – 96)	77 (63 – 95)	84 (62 – 107)	78 (61 – 93)	-
	Bottom	76 (29 – 96)	75 (46 – 95)	78 (30 – 106)	74 (54 – 93)	-
DO (mg/L)		5.8 (4.2 – 7.2)	5.5 (4.3 – 7.5)	6.0 (4.2 – 7.1)	5.5 (4.1 – 7.4)	Not less 4 mg/L for 90% of the samples
	Bottom	5.5 (2.1 – 7.4)	5.4 (3.1 – 7.6)	5.6 (2.2 – 7.1)	5.3 (3.9 – 7.4)	Not less 2 mg/L for 90% of the samples
pH value		8.0 (7.6 – 8.2)	8.1 (8.0 – 8.3)	8.0 (7.8 – 8.2)	8.1 (8.0 – 8.3)	6.5 - 8.5 (± 0.2 from natural range)
Secchi disc (m)		2.2 (1.0 – 3.5)	2.8 (1.7 – 3.9)	2.1 (1.0 – 3.1)	2.5 (1.5 – 3.5)	-
Turbidity (NTU)		10.5 (6.3 – 14.2)	8.7 (5.9 – 11.8)	9.6 (6.4 – 14.0)	8.1 (5.4 – 10.8)	-
Suspended Solids (SS) (mg/L)		7.0 (3.1 – 15.2)	5.2 (2.3 – 9.2)	5.8 (2.4 – 9.9)	4.3 (1.9 – 6.4)	Not more than 30% increase
Silica (as SiO2) (mg/L)		0.7 (0.2 – 1.1)	0.7 (0.4 – 1.1)	0.6 (0.1 – 1.2)	0.7 (0.2 – 1.2)	-
5-day Biochemical Oxygen Demand (BOD5) (mg/L)		0.8 (0.4 – 2.1)	0.9 (0.4 – 1.6)	1.1 (0.5 – 2.3)	1.1 (0.5 – 1.8)	-
Nitrite Nitrogen (NO2-N) (mg/L)		0.02 (<0.01– 0.04)	0.02 (<0.01– 0.05)	0.02 (0.01 – 0.04)	0.02 (<0.01 – 0.05)	-
Nitrate Nitrogen (NO3-N) (mg/L)		0.06 (0.03 – 0.10)	0.06 (0.02– 0.11)	0.07 (0.03 – 0.13)	0.08 (0.02 – 0.14)	-
Ammonia Nitrogen (NH3-N) (mg/L)		0.10 (0.01 – 0.22)	0.09 (0.02– 0.22)	0.13 (0.02 – 0.26)	0.13 (0.04 – 0.26)	-
Unionised Ammonia (UIA) (mg/L)		0.003 (<0.001 – 0.009)	0.004 (0.002–0.008)	0.004 (0.001 – 0.010)	0.007 (0.002 – 0.012)	Not more than annual average of 0.021 mg/L
Total Inorganic Nitrogen (TIN) (mg/L)		0.18 (0.08 – 0.35)	0.18 (0.11 – 0.31)	0.23 (0.09 – 0.40)	0.24 (0.11 – 0.38)	Not more than annual water column average of 0.4 mg/L
Total Nitrogen (Total-N) (mg/L)		0.32 (0.20 – 0.49)	0.30 (0.20– 0.45)	0.38 (0.19 – 0.55)	0.39 (0.19 – 0.57)	-
Ortho-Phosphate (Ortho-P) (mg/L)		0.014 (0.002– 0.025)	0.021 (0.01– 0.04)	0.016 (0.002 – 0.035)	0.027 (0.02 – 0.05)	-
Total Phosphorus (Total-P) (mg/L)		0.04 (0.03 – 0.06)	0.04 (0.02– 0.06)	0.04 (0.02 – 0.06)	0.04 (0.02 – 0.06)	-
Chlorophyll-a (µg/L)		2.8 (0.7 – 12.7)	2.9 (0.4 – 12.5)	3.6 (0.7 – 11.3)	4.0 (0.2 – 19.0)	-
E. coli (cfu/100 mL)		440 (28 – 4300)	200 (48 – 2400)	660 (33 – 8000)	1100 (130 – 6600)	-
Faecal Coliform (cfu/100 mL)		870 (79 – 8000)	390 (70 – 3800)	1400 (90 – 27000)	2100 (160 – 13000)	-

Note: 1. Except as specified, data presented are depth-averaged values calculated by taking the means of three depths: Surface, mid-depth, bottom.

2. Data presented are annual arithmetic means of depth-averaged results except for E. coli and faecal coliforms that are annual geometric means.

3. Data in brackets indicate the ranges.

5.3.2 With reference to the EPD’s publication “Marine Water Quality in Hong Kong 2002”, the water quality at Junk Bay was largely unsatisfactory before 2002 with four major outfalls, including Kwun Tong PTW, Shau Kei Wan PTW, Chai Wan PTW and Tseung Kwan O PTW, discharging into the Lei Yue Mun area. Since commissioning of the HATS Stage I, these major pollution sources have been removed and the WCZ has experienced a marked improvement. The water quality conditions at Stations JM3 and JM4 fully complied with the key WQOs including DO, UIA and TIN in both 2002 and 2003.

5.3.3 Before 2002, the Eastern Buffer WCZ was subject to effluent discharges from the TKO and Chai Wan outfalls. These major pollution sources have been diverted to the Stonecutters Island Sewage Treatment Works following the commissioning of the HATS Stage I in 2001, the Eastern Buffer WCZ has experienced a very substantial improvement in water quality in 2002. In 2003, the concentrations of pollutants, such as E.coli, NH₄-N, TIN and total phosphorus showed further reductions. The water quality conditions at Stations EM1 and EM2 fully complied with the WQOs including DO, UIA and TIN in both 2002 and 2003.

5.3.4 The implementation of HATS Stage I in 2001 has resulted in a very substantial water quality improvement at the eastern end of the harbour (VM1 and VM2). Based on EPD’s publication “EPD Marine Water Quality in Hong Kong 2002”, there was a very significant reduction of E.coli at the Stations VM1 and VM2 in 2002 by more than 90%, reaching record low level. Although there is an increase in E.coli level at Station VM2 in 2003, the pattern of bacteria distribution was similar to that of 2002 based on EPD’s publication. The water quality conditions at Stations VM1 and VM2 fully complied with the WQOs including DO, UIA and TIN in both 2002 and 2003.

5.3.5 A baseline marine water quality survey was carried out in 2003 at the stations shown in Figure 5.3. The monitoring locations include 3 stations in the EDC (EC1-EC3), 4 stations within Junk Bay (JB1-JB4), and 2 stations at east and west of the bay mouth at Lei Yue Mun Channel (LYM) and Tathong (TT) Channel respectively. The measurements covered a complete spring-neap tidal cycle for both dry and wet seasons. The field survey results are summarised in Table 5.10Table 5.10Table 5.10Table 5.10. The long-term field data collected at 2 stations (namely M3 and M4 as shown in Figure 5.3) by the TKO Stage I Landfill restoration contractor are also presented in Table 5.10Table 5.10Table 5.10Table 5.10 to provide a fuller picture of the water quality.

Table 5.10 Field Survey Results

Station		Depth Averaged DO (mg/L)	Bottom DO (mg/L)	E. coli** (no./100mL)	UIA (mg/L)	TIN (mg/L)	BOD5 (mg/L)	SS (mg/L)
Junk Bay WCZ
EDC
EC1 ^##	Min	2.7 ^B	1.9^B	1	0.000	0.110	2	1.0
	Max	8.1	8.1	2900	0.337	6.775	2	21.5
	Annual Mean	5.7	5.6	86	0.025^A	0.442^A	2	5.8
	Annual Median	-	-	41	-	-	-	4
	10%ile	3.3 ^A, B	3.1^B	-	-	-	-	-
EC2 ^##	Min	3.1^B	3.0^B	1	0.000	0.035	2	1.0
	Max	8.2	8.3	3050	0.050	0.650	2	13.5
	Annual Mean	5.9	5.7	28	0.016	0.211	2	4.6
	Annual Median	-	-	22	-	-	-	4
	10%ile	3.5 ^A, B	3.4^B	-	-	-	-	-
EC3 ^##	Min	3.1^B	3.1^B	1	0.001	0.085	2	1.0
	Max	8.3	8.3	4900	0.068	0.520	2	19.5
	Annual Mean	5.9	5.8	25	0.016	0.192	2	5.1
	Annual Median	-	-	16	-	-	-	3
	10%ile	3.5 ^A, B	3.4^B	-	-	-	-	-
M3 ^++	Min	6.5	5.3	-	-	-	1.3	2.3
	Max	7.5	7.7	-	-	-	1.8	5.0
	Annual Mean	7.2	6.3	-	-	-	1.6	3.6
	Annual Median	-	-	-	-	-	-	3.3
	10%ile	6.7	5.3	-	-	-	-	-
M4 ^++	Min	6.8	5.7	-	-	-	1.0	3.3
	Max	8.0	7.6	-	-	-	2.3	5.0
	Annual Mean	7.4	6.6	-	-	-	1.5	4.2
	Annual Median	-	-	-	-	-	-	4.3
	10%ile	6.9	5.7	-	-	-	-	-
WQO for Junk Bay WCZ		≥4 (90%ile)	≥2 (90%ile)	≤610 (Annual Geometric Mean) ^@@	≤0.021 (Annual Mean)	≤0.3 (Annual Mean)	-	-
WQO for inland waters in Junk Bay WCZ		≥4	≥4	≤1000^R	-	-	≤5	≤25 (Annual median)
Junk Bay
JB1 ^##	Min	2.8	2.8	1	0.001	0.030	-	1.0
	Max	9.2	8.8	767	0.018	0.267	-	16.7
	Annual Mean	5.9	5.8	22	0.006	0.141	-	4.1
	10%ile	3.3^A	3.3	-	-	-	-	-
JB2 ^##	Min	3.1	3.0	1	0.001	0.047	-	1.0
	Max	9.1	9.5	613	0.014	0.260	-	9.0
	Annual Mean	6.0	5.9	23	0.005	0.129	-	3.6
	10%ile	3.4^A	3.3	-	-	-	-	-
JB3 ^##	Min	3.4	3.3	2	0.002	0.087	-	1.0
	Max	7.7	7.6	520	0.008	0.230	-	10.0
	Annual Mean	5.7	5.7	42	0.004	0.145	-	4.0
	10%ile	3.8^A	3.6	-	-	-	-	-
JB4 ^##	Min	3.0	2.9	5	0.001	0.067	-	1.0
	Max	9.2	9.4	730	0.027	0.277	-	17.7
	Annual Mean	5.9	5.9	59	0.006	0.134	-	4.5
	10%ile	3.2^A	3.1	-	-	-	-	-
WQO for Junk Bay WCZ		≥4 (90%ile)	≥2 (90%ile)	≤610 (Annual Geometric Mean) ^@@	≤0.021 (Annual Mean)	≤0.3 (Annual Mean)	-	-
Easter Buffer WCZ
LYM ^##	Min	2.9	2.7	1	0.001	0.077	-	1.0
	Max	8.4	8.6	1283	0.025	0.250	-	12.7
	Annual Mean	5.6	5.7	114	0.007	0.164	-	4.6
	10%ile	3.1^A	3.0	-	-	-	-	-
TT ^##	Min	3.4	3.4	1	0.001	0.040	-	1.0
	Max	8.9	9.0	1490	0.005	0.253	-	11.3
	Annual Mean	5.9	5.9	49	0.003	0.112	-	3.6
	10%ile	3.7^A	3.7	-	-	-	-	-
WQO for Eastern Buffer WCZ		≥4 (90%ile)	≥2 (90%ile)	-	≤0.021 (Annual Mean)	≤0.4 (Annual Mean)	-	-

Notes:

** The annual average of the E. coli level was calculated as geometric mean.

^## Based on field data collected under this Study during the dry season (Feb 03) and wet season (Jun 03) surveys.

++ Based on field data collected by the TKO Stage I Landfill restoration contractor in Aug 00, Nov 00, Jan 01, Feb 01, Aug 01, Nov 01, Feb 02, Aug 02, Nov 02, Feb 03, Aug 03, Mar 04.

A. Exceedance of marine water quality objective.

B. Exceedance of river water quality objective.

R. E.coli objective represents the running median of the 5 most recent consecutive samples taken at intervals between 7 and 21 days.

^@@ WQO for E.coli is applied for secondary contact recreation subzone and fish culture subzone only.

Dissolved Oxygen (DO)

5.3.6 The 10 percentile (%ile) depth averaged DO marginally exceeded the marine WQO of 4 mg/L for all survey stations except M3 and M4. The 10%ile bottom DO however complied very well with the WQO of 2 mg/L at all stations with values from 3.0 to 5.7 mg/L. The mean depth averaged DO levels ranged from 5.6 mg/L at LYM in the Tathong Channel to 7.4 mg/L at M4 in the EDC.

5.3.7 For stations located in the EDC, the DO levels measured at M3 and M4 fully complied with the WQO for inland waters in Junk Bay WCZ of 4 mg/L whereas DO exceedances of inland WQO occurred at EC1, EC2 and EC3. The lowest depth-averaged DO level was 2.7 mg/L recorded at the most upstream station (EC1).

5-day Biochemical Oxygen Demand (BOD₅)

5.3.8 The BOD₅ levels were only measured in the EDC and all measured values were low (< 2.5 mg/L) which complied very well with the inland WQO of 5 mg/L.

E.coli

5.3.9 The measured E. coli levels at all stations were in general low. The geometric mean E. coli levels ranged from 22 no./100mL in Inner Junk Bay (Station JB1) and in Eastern Channel (Station EC2) to 114 no./100mL at Lei Yue Mun (Station LYM). The E. coli levels at Lei Yue Mun were subject to the pollution sources discharged from Kowloon Bay and KTAC in the Victoria Harbour and are therefore relatively higher. It should be noted that only Station JB2 is located within the existing secondary contact recreation subzone in Junk Bay. The geometric mean E. coli level measured at JB2 was 23 no./100mL which complied very well with the WQO of 610 no./100mL for secondary contact recreation.

5.3.10 Within the EDC, E.coli was only measured in Stations EC1-EC3. All measured annual median E. coli values complied very well with the inland WQO of 1000 no./100mL.

Suspended Solids (SS)

5.3.11 The mean SS levels at the stations ranged from 3.6 mg/L in the EDC (Station M3) to 5.8 mg/L at the most upstream station in the EDC (EC1).

5.3.12 For stations in the EDC, all annual median SS levels complied very well with the inland WQO of 25 mg/L.

Unionized Ammonia (UIA)

5.3.13 The UIA levels measured at the most upstream station of the EDC (EC1) were the highest with a mean value of 0.025 mg/L. The mean UIA measured at the rest of the stations complied very well with the WQO of 0.021 mg/L with values from 0.003 to 0.016 mg/L.

Total Inorganic Nitrogen (TIN)

5.3.14 Similar to the UIA results, the mean TIN levels measured at the most upstream station of the EDC (EC1) were the highest with a mean value of 0.442 mg/L. The mean TIN measured at the other stations complied well with the relevant WQO (0.3 mg/L for Junk Bay WCZ and 0.4 mg/L for Eastern Buffer WCZ) with values from 0.112 to 0.211 mg/L. The survey results showed a concentration gradient with higher TIN levels in the upper EDC.

Summary

5.3.15 The field survey data revealed that the water quality in the vicinity of the Site (including EDC, Junk Bay, Lei Yue Mun and Tathong Channel) complied well with the relevant marine WQOs except for the DO levels which marginally breached the WQOs. The water quality in the EDC also complied well with the inland WQOs except for the DO levels. The EDC with weak tidal circulation is sensitive to increases of pollution discharges. These areas are also subject to the direct influence of pollution discharges from the upstream watercourses resulting from cross connections or unsewered properties. The survey results showed an increase trend of pollution levels towards the inner EDC.

5.4 Water Sensitive Receivers

5.4.1 Figure 5.2 shows the existing and planned marine sensitive receivers that may be affected by the Project. The main marine water sensitive receivers and beneficial uses include:

· cooling water intakes

· salt water intakes

· gazetted beaches

· fish culture zones

· coral habitats

· Site of Special Scientific Interest (SSSI).

5.4.2 A detailed description of coral occurrence along the southwest coast of Junk Bay outside the proposed reclamation area is provided in Sections 8.4.45 to 8.4.48. The coral habitats at Ninepins Islands to the east, Sung Kong Island, Waglan Island and Beaufort Island to the south as well as the SSSI in the Tai Tam Bay of Southern Hong Kong Island are not included as they are more than 8 km away from the Site. The impacts of this Project would be minimal on these distant areas. The boundary of the proposed water sports recreation zone is shown in Figure 5.1a.

5.5 Assessment Methodology

Operational Phase Impact from WCR Reclamation and CBL

Modelling Scenarios for Operational Phase

5.5.1 Hydrodynamic and water quality modelling is required to evaluate the change in the hydrodynamic regime due to the WCR reclamation and construction of the CBL. A strip of land would be reclaimed along the western shoreline of Junk Bay for the proposed WCR (Figure 2.35). The CBL running over Junk Bay is planned to link the traffic from the south-eastern part of TKO to the WCR (Figure 2.38). The extent of the reclamation has already been minimised to satisfy the Government’s requirement and the community’s aspiration.

5.5.2 Modelling was carried out for 3 scenarios as follows:

Scenario 1

· 2003 Baseline Scenario represents the existing baseline condition in 2003 without the Project.

Scenario 2

· Ultimate Scenario with no WCR and CBL represents the ultimate condition with the proposed developments in TCS and PSK but without WCR reclamation and CBL.

Scenario 3a

· Ultimate Scenario represents the ultimate condition with the Project (including the proposed developments at TCS and PSK, WCR reclamation as well as CBL).

5.5.3 The presence of the WCR reclamation and the bridge piers of CBL may reduce the flushing of Junk Bay and Victoria Harbour and thus impact upon the water quality. The ultimate scenario, with completion of both WCR reclamation and CBL, represents a worst case in terms of impact on tidal flushing. Additional scenario for addressing the hydrodynamic impact during different interim construction stages is considered not necessary.

5.5.4 The ultimate population predicted under the current OZP, as shown in Table 5.1Table 5.1Table 5.1Table 5.1, was adopted to estimate the residual pollution loading that would be discharged into the Junk Bay water under Scenario 2 and Scenario 3a. The population represents the ultimate population at TKO and is very conservative since the actual planned population is less. The population shown in Table 5.1 has taken into account all proposed development sites at TCS and PSK assuming all the proposed development sites and infrastructures at TKO would be fully utilized. There would not be any further natural population growth due to the limited infrastructure capacity that can be made available within the catchment.

Modelling Tools

5.5.5 A detailed 3-dimensional detailed model, namely ‘Junk Bay Model’, has been developed under the present Study using the Delft3D package and is used to simulate the operation and construction phases of the Project. The grid layout and bathymetry schematisation of the Junk Bay Model are shown in Appendix 5.1. Details of the model set-up and calibration of the Junk Bay Model are presented in the Junk Bay Model Calibration Report⁽[6]⁾.

Pier Friction

5.5.6 The cumulative impact from the CBL together with the WCR reclamation was simulated in the ultimate scenario. Figure 5.4a shows the alignment of the CBL bridge.

5.5.7 The CBL bridge piers have variable separation distance. The cross-sections for different piers are also different. The details of the spacing and the cross sections of the bridge piers are shown in Table 5.11Table 5.11Table 5.11Table 5.11 and Figure 5.4b (Sheet 1 to Sheet 3). Some of the piers have been designed with ship protection dolphins to protect the piers from ship impact while some have been designed with rubber arch fender. Figures 5.5a and 5.5b show the details of dolphins for the piers. Figures 5.5c shows the fender details for pile caps of other bridge piers.

Table 5.11 The Spacing and Cross Section of the Bridge Piers

Pier	Length (m)	Width (m)	Pier Spacing (m)
Pier Type A1	4.5	3	52.5
Pier Type A2	4.5	3	42.5
Pier Type A3	4	3	42.5
Pier Type A4	4	3	55
Pier Type A5	8	4	55
Pier with rubber arch fender
Pier Type B	27.6	6.5	80
Pier Type C	19.7	6.5	80
Pier Type D	15.6	6.5	80
Pier Type H	15	6.5	80
Pier Type I	15	6.5	45
Pier Type J	16.4	6.5	55
Pier Type K	18.2	6.5	55
Pier with Dolphin structure
	Length of the dolphin structure	Width of the dolphin structure	Pier Spacing
Pier Type E	26	15.5	80
Pier Type F	26	15.5	200
Pier Type G	57.9	24	100

5.5.8 As the dimensions of the bridge piers are much smaller than the grid size, the exact pier configurations cannot be adopted in the model simulation. Instead, only the overall influence of the bridge piers on the flow will be taken account. This overall influence is modelled by a special feature of the Delft3D-FLOW model, namely porous plate. Porous plates represent transparent structures in the model and are placed along the model gridline where momentum can still be exchanged across the plates. The porosity of the plates is controlled by a quadratic friction term in the momentum to simulate the energy losses due to the presence of the bridge piers. The forces on the flow due to a vertical pile or series of piles are used to determine the magnitude of the energy loss terms.

5.5.9 The mathematical expressions for representation of pier friction were based on the Cross Border Link Study[7] and the Delft 3D-FLOW module developed by Delft Hydraulics and are given in Appendix 5.2.

5.5.10 The loss coefficients were calculated for different pier types in the flow directions perpendicular to the bridge alignment in Table 5.12Table 5.12Table 5.12Table 5.12 for reference. As there are a number of different types of pier in the CBL, piers of link roads L5, L6, L7 and L8 (i.e. Pier Types A1, A2, A3, A4 and A5) have been grouped to facilitate the calculation (referred to as Section A in Table 5.12 and Figure 5.4a). Details of their pile structures are shown in Figure 5.4b (Sheet 1 of 3) and Figure 5.5c. For actual model input, separate calculations were performed to estimate the loss coefficients for relevant individual model grid cells. For each grid cell where the bridge pier(s) will be located, two loss coefficients have to be specified in the model for two different flow directions respectively (i.e. the two directions perpendicular to the gridline, namely u-direction and v-direction respectively). Details of the equations used are contained in Appendix 5.2.

Table 5.12 Loss Coefficient for the Piers in the Flow Direction Perpendicular to the Bridge Alignment

Type of Piers (refer to Figures 5.4a)	Loss Coefficient
Section A (including Pier A1-A5)	0.83
Pier Type B	0.11
Pier Type C	0.09
Pier Type D	0.08
Pier Type E	0.22
Pier Type F	0.07
Pier Type G	0.36
Pier Type H	0.08
Pier Type I	0.17
Pier Type J	0.14
Pier Type K	0.14

Coastline Configurations

5.5.11 The proposed coastline configurations for Scenario 2 (ultimate scenario with no WCR and CBL), highlighting the incorporated coastal developments, are shown in Figure 5.6. The coastline configuration in Figure 5.6 represents the conditions in 2011/2016 without the Project. The coastline configuration for 2011/2016 has taken into account the layouts in the latest approved EIA reports except for the reclamations at Yau Tong Bay, Wan Chai Development II and South East Kowloon Development. These 3 projects are not included as their reclamation layouts are still subject to planning review. A detailed layout (coastline configuration) of the present Project is shown in Figures 2.35 and 2.38 and was incorporated in the Junk Bay Model for assessment under Scenario 3a (ultimate scenario).

Pollution Loading

5.5.12 The 2003 and ultimate pollution loading for the Junk Bay catchment are presented in the separate Final Pollution Loading Inventory Report for the present Study ⁽[8]⁾. The inventory incorporates all possible pollution sources including those from landfill sites, non-point source surface run-off and sewage from cross connections. The ultimate pollution loading inventory has taken into account the ultimate developments at TKO which represent a worst-case in terms of pollution loading discharges to Junk Bay. The pollution loading inventory of other catchments outside TKO was derived from the Update Study and updated load estimates from Wan Chai Development Phase II ⁽[9]⁾ and South East Kowloon Development ⁽[10]⁾ studies.

5.5.13 To take account of the background pollution loading for cumulative assessment, pollution loading from the proposed HATS has been taken into account. Option 5a of HATS (chemical enhanced primary treatment CEPT with disinfection) is assumed in this EIA study for water quality modelling. Option 5a involves a discharge of effluent at the existing Stonecutters Island Sewage Treatment Works (SCISTW). The HATS loading assumed in this Study is given in Table 5.13Table 5.13Table 5.13Table 5.13 below. It should be noted that the HATS loading used in the model is slightly more conservative than that reported in the EEFS Final Report ⁽[11]⁾.

Table 5.13 Pollution Loading from Stonecutters Sewage Treatment Works under HATS

Parameters	Stonecutters
Flow (m^3 per day)	2,787,291
BOD5 (g per day)	188,978,330
SS (g per day)	117,066,222
Organic Nitrogen (g per day)	27,674,014
NH3-N (g per day)	49,443,560
E. coli (no. per day)	8.36187 x 10^15
Total Phosphorus (g per day)	836,1873
Ortho-Phosphate (g per day)	5,017,124
Silicate (g per day)	23,970,703
Total nitrite and nitrate (g per day)	0

Key Modelling Parameters

5.5.14 The key modelling parameters of the Junk Bay Model are summarised in Table 5.14Table 5.14Table 5.14Table 5.14. The key parameters of interest selected for presenting the modelling results are summarised in Table 5.15Table 5.15Table 5.15Table 5.15.

Table 5.14 Key Water Quality Modelling Parameters

Parameter	Description
Salinity	Salinity
ModTemp	Water Temperature
E Coli	E. coli Bacteria
Oxy	Oxygen
CBOD5	Carbonaceous 5-day Biochemical Oxygen Demand
NO3	Nitrate
NH4	Ammonium
PO4	Ortho-Phosphate
AAP	Adsorbed Ortho-Phosphorus
Si	Silica
Diat	Diatoms
Green	Algae
DetC	Detritus Carbon
DetN	Detritus Nitrogen
DetP	Detritus Phosphorus
DetSi	Detritus Silica
BOD5	5-day Biochemical Oxygen Demand
Chlfa	Chlorophyll a
SS	Suspended Solids
TotN	Total Nitrogen
TotP	Total Phosphorus
NH3	Unionised Ammonia
Fsed	Sedimentation flux

Table 5.15 Key Parameters Selected for Presentation

Parameter

Depth Averaged Dissolved Oxygen (DO)

Bottom DO

Depth Averaged Salinity

Depth Averaged Total Inorganic Nitrogen (TIN)

Depth Averaged Unionised Ammonia (UIA)

Depth Averaged Suspended Solids (SS)

Depth Averaged E. coli

Maximum Sedimentation Rate

Impact from Sewage Emergency Bypass

5.5.15 Under normal operation of the TKOPTW, treated effluent is discharged into the existing HATS Stage I Tunnel System for conveyance to the SCISTW for treatment and ultimate disposal into the western approaches of the Victoria Harbour. In the event of emergency situations such as shutdown of TKOPTW or power failure, raw sewage will be directly discharged into the Tathong channel via an existing 1,320mm diameter submarine outfall. Under a very remote condition when malfunctioning of the submarine outfall occurs during the emergency situation, effluent would be diverted to the south of Area 86 for discharge at the seawall. Figure 5.7 shows the emergency discharge locations.

5.5.16 Modelling was carried out for two scenarios to simulate the impact on inner Junk Bay and EDC as follows:

· Scenario 4a - continuous emergency bypass of raw sewage at the seawall for a period of 12 hours under ultimate scenario.

· Scenario 4b - continuous emergency bypass of raw sewage via the submarine outfall at Tathong channel for a period of 12 hours under ultimate scenario.

5.5.17 According to the information provided by DSD, emergency bypass at the existing TKOPTW have not had happened before due to the existing light load condition. At present, there is adequate spare capacity to handle emergency situation, if any, to avoid sewage bypass. Emergency sewage bypass at TKOPTW is however expected in the future when the loading is approaching the design capacity. According to DSD, there is a planned sewage bypass at TKOPTW in each month. During the planned sewage bypass, all the effluent generated in the TKOPTW will be discharged via the submarine outfall at Tathong channel for one hour.  

5.5.18 The historical records of emergency bypass for other similar PTWs in Victoria Harbour WCZ (including Wan Chai West SSP, Chai Wan PTW, To Kwa Wan PTW, Kwai Chung PTW, Shau Kei Wan PTW and Chai Wan PTW) were reviewed for the period from 1998 to 2002. The highest frequency of emergency bypass was recorded at Chai Wan PTW where emergency discharge had occurred five times in 2002. The longest duration of emergency discharge was 2 hours 40 minutes recorded at Kai Chung PTW in 2001. The recorded emergency bypasses were due to prolonged or very heavy rainfall or power interruption or system or equipment failure. Using a 12-hour discharge period for modelling (Scenarios 4a and 4b) is a conservative assessment approach.

5.5.19 For each of the two scenarios (4a and 4b), the emergency discharge was modelled for three typical tidal conditions, namely wet season spring tide, wet season neap tide and dry season neap tide. For all selected tide conditions, it is assumed that the discharge would start at a flood tide where the pollutants would be transported to the inner Junk Bay.

5.5.20 According to the SIA conducted under this Study (Section 6), the average dry weather flows (ADWF) generated by the TKO sewerage catchment was estimated to be 161,596 m³/day for ultimate scenario with further developments of TKO. The ADWF was estimated by applying appropriate unit sewage flow factors to the ultimate population data for the sewage catchments. The adopted unit flow factors are based the Sewerage Manual part 1 (DSD, 1995). The unit flow factors are tabulated in.

Table 5.16 Unit Flow Factors

Development Type	Unit Flow Factor (l/head/d)
Residential
Low Cost Rental	175
R1	240
R2	300
R3	370
Village	240
Government/Institution/Community	240
Commercial
Job Types J2 to J12	350
Industrial
Job Types J1	1,000
Schools
School	25

5.5.21 Peaking factors including stormwater allowance in accordance with the Sewerage Manual were applied to the ADWF to establish the peak flows. The peak flow of 4.48m³/s for ultimate scenario was used to assess the water quality impact under the emergency discharge condition (Scenarios 4a and 4b). The assumed quality of the raw sewage discharge is given in Table 5.17Table 5.17Table 5.17Table 5.17 and is based on the measured value of raw wastewater in the Tai Po Sewage Treatment Works.

Table 5.17 The Assumed Flow Rate and Quality of Emergency Discharges

Flow (m^3/s)	BOD5 (mg/L)	TSS (mg/L)	TKN (mg/L)	Total N (mg/L)	NH3-N (mg/L)	E. coli (no./100mL)
4.48	200	200	57	57	28	2 x 10^7

Construction Phase Impact

Marine Pile Construction for CBL

5.5.22 Brief descriptions of the pile construction works for CBL bridge are provided in the subsequent sections. No dredging would be required for the construction works and no release of sediment is normally expected according to the proposed construction method.

5.5.23 Dolphins - Bored piles or equivalent system would be provided for the dolphin. The piles are to be bored with a permanent steel casing, which remains to combine with the concrete hearting to sustain the design impact loading. The dolphin piles would be installed from a “spud” barge (i.e. jack-up) with templates and gates used to preserve the positioning. A derrick would be used to lift the tubes and the lowering off would be carried out on close monitoring of verticality. The pile would be driven into the bedrock head level with the soft material being excavated. While excavating within the casing, the excavation depth will not be deeper than the casing head depth at any time.

5.5.24 Marine Bored Piling for the Viaduct - Following completion of pile construction for the dolphin ring beams, the temporary stagings used to access the pile heads would be removed and replaced by a steel platform which serves as a piling platform for bored piles of the main cap. The intention is that these platforms enable the bored piling and cap construction to be carried out effectively as ‘land based’ operations with benefits in terms of output, safety and environmental protection. The platforms would be designed for convenience of construction and would be fully decked out, with wastewater collected for controlled discharge into a derrick lighter or other collection system.

5.5.25 The platforms would be designed to allow the piling rigs to stand in their best position for piling efficiency; and the decking would have circular upstands round each pile location such that a protective skirt formed in lapped conveyor belting can be strapped/clamped to the casing and upstand as sketched below. This is for effective control over spillage of excavated material or wash water.

5.5.26 Temporary steel casings would be provided for each pile; and this also protects the excavation against slumping. The casings would be driven into the seabed with soft material inside the temporary casing being excavated. After the bored pilling, steel reinforcement would then be placed into the excavated pile followed by concreting works. The concrete will be ready mixed off-site and delivered by truck which would drive onto a vessel from a facility on site adjacent to landing point. A mobile crane on the vessel or other service crane will lift the concrete to the piles by means of concreting skips.

5.5.27 All wastewater generated from the piling activities will be collected by a derrick lighter or other collection system and be treated before controlled discharge. Spoil will be collected by sealed hopper barges for proper disposal.

Deep Cement Mixing (DCM) Construction Sequences

5.5.28 The deep cement mixing (DCM) is a ground treatment method which involves injecting controlled volumes of cement into the compressible materials underlying the seawalls whilst simultaneously mixing the cement with the in-situ material to form a regular pattern of strengthened material. The pattern of treatment within soft marine deposit is depended upon strength requirements and the typical patterns may comprise individual walls, a lattice of walls, individual piles or a solid block of treated ground. A blanket layer of sand fill would be required to prevent the escape of cement slurry into the water and disturbance of sediment fines during the mixing. The construction sequences for DCM are summarized as follows:

1. Carrying out site investigation to determine the property, grading, chemical composition of the sediment.

2. Obtaining sediment samples for laboratory investigation to produce design mix of cement slurry.

3. Placing of sand blanket to cover the seabed at the area where DCM would be carried out.

4. Positioning of marine DCM plant.

5. Inserting piling pipe of mixing treatment equipment into the soft layer at the designated level.

6. Pulling up of piling pipe together with the injection of cement slurry and mixing of soft material by the agitator.

7. Monitor, control, review and adjust the cement slurry content during mixing.

8. Repositioning of the marine DCM plant and repeat the mixing procedure until the required pattern of strengthened material is formed.

9. Taking core samples of strengthened material and carrying out associated tests to verify the integrity of the strengthened material.

10. Removal of the sand blanket and heaved material where necessary.

Description of Interim Reclamation Phases

5.5.29 Reclamation will be carried out in 3 phases, namely Phase I, Phase II and Phase III, as indicated in Item 2.1 of Appendix 2.2. Boundaries of the three reclamation phases are shown in Figure 2.35. Three phases of the reclamation will not be carried out concurrently. For each reclamation phase, seawall will be constructed for the entire reclamation boundary first (including a temporary seawall at the northern boundary immediately adjacent to the next reclamation phase) before any filling activities to be carried out within the reclamation site. Storm diversion works would be conducted at an early stage of each reclamation phase. The storm diversion sequences for different reclamation stages are shown in Appendix 2.1. According to the construction programme, formation of a small embayment area to the north of Phase II reclamation (Figure 5.3b) would occur after Phase II seawall construction is completed in June 2011 and before the Phase III reclamation commences in April 2013. Creation of such temporary embayed area would not be a key concern as there is no water sensitive receiver identified in the embayed area and nearby waters. The associated water quality impact is considered minor.

Reclamation Works for WCR

5.5.30 The marine construction works for WCR and CBL would commence in 2010 and 2013 respectively for completion by 2016. The tentative construction programme for reclamation works is provided in Appendix 2.2. The reclamation is proposed to be carried out in three phases as shown on Figure 2.35 and they are described briefly as follows:

· Phase I- Dredged reclamation with dredged seawalls at the southern end to form the land for the tunnelling works;

· Phase II- the reclamation will be a drained reclamation with band drains and surcharge to treat the mud under the reclamation;

· Phase III- the reclamation will be a drained reclamation with band drains and surcharge to treat the mud under the reclamation.

5.5.31 Dredging would only be required for Phase I seawall construction and Phase I reclamation. No seawall dredging would be required for the Phase II and Phase III works. DCM would be conducted for Phase II and Phase III seawall construction. Sand filling would be required for seawall construction for Phase I and Phase II only. No sand filling would be required for Phase III seawall construction. As discussed in Section 5.5.29, backfilling would be carried out behind the completed seawall.

5.5.32 Rock armour, rock fill and sand fill would be used for construction of the seawall in the 3 phases. While public fill, sand fill and general fill would be used for reclamation in Phase II and Phase III, only sand fill is recommended to be used for the reclamation in Phase I. Table 5.18Table 5.18Table 5.18Table 5.18 shows the expected fill volumes within each phase of the WCR reclamation.

Table 5.18 Fill Volumes (with Phase II and Phase III Seawalls founded on Deep Cement Mixing Columns)

Reclamation Phase	Seawall Construction			Reclamation
	Rock Armour	Rockfill	Sandfill	Sandfill	Public Fill	General Fill ^(1)	Public Fill for Surcharge Use ^(2)
I	16,000	25,000	55,000	275,000	-	-	60,000
II	60,000	130,000	160,000	185,000	380,000	870,000	550,000
III	42,000	395,000	0.00	50,000	380,000	475,000	145,000
Total	118,000	550,000	215,000	510,000	760,000	1,345,000	755,000

Note (1) General fill material is basically completely decomposed granite (CDG) or completely decomposed volcanic (CDV) material which is better in quality as compared to the public fill.

Note (2): Surcharge Fill also comes from Public Fill. Surcharge fill material under Reclamation Phases 1 and II will be used as fill material for Reclamation Phases II and III respectively.

Sediment Quality and Approach for Construction Phase Modelling

5.5.33 The results of the marine site investigation carried out in the Feasibility Study for Intensification and Extension of Tseung Kwan O (IETKO) and the site investigation conducted under this Project have been reviewed to classify the sediment quality of the proposed dredged areas for the purpose of the EIA Study. The sampling points are presented in Figure 11.1. Details of the baseline sediment quality are provided in Section 11.

5.5.34 The seabed area would be dredged for construction of the seawall and reclamation area for the Phase 1 Reclamation of the WCR only. The total volume of dredged sediment was estimated to be approximately 20,000 m³. The sediment quality analysis results indicated the sediment at and near the WCR dredged area (i.e. Stations VC7, VC9, VC8, VC10 and G2) to be Category L. Sediment quality results for Stations VC7, VC9, VC8, VC10 and G2) are extracted from Section 11 and are summarized in Table 5.18a below. Thus, it is not expected that the sediment to be dredged for Phase I seawall and reclamation would be contaminated.

Table 5.18a Sediment Analysis Results from Marine Ground Investigation Works under IETKO and this Study

Sampling Location	Sampling Depth (m)		Metals and Metalloid Content (mg/kg)									µg/kg			µg/L	Category
	From	To	Cd	Cr	Cu	Ni	Pb	Zn	Hg	As	Ag	LMW PAHs	HMW PAHs	PCBs	TBT
VC10	0.00	0.55	0.1	9.1	13	5.3	32	44	0.09	3.2	0.2	<550	<1700	<23	<0.15	L
VC7	0.16	0.9	0.1	9.8	22	4.3	31	74	0.1	3.8	0.2	<550	<1700	<23	<0.15	L
VC7	0.90	1.80	<0.1	3.7	2.3	2.8	8.8	<10	0.06	1.3	<0.1	<550	<1700	<23	<0.15	L
VC9	0.00	0.90	<0.1	8.5	13	4.25	23	44	0.09	4.7	0.2	<550	<1700	<23	<0.15	L
VC9	0.90	1.90	<0.1	5.0	3.5	3.9	15	23	0.08	4.4	<0.1	<550	<1700	<23	<0.15	L
VC9	1.90	2.90	<0.1	5.6	2.5	3.8	11	15	<0.05	2.6	<0.1	<550	<1700	<23	<0.15	L
VC9	2.9	3.15	<0.1	1.3	1.2	1.4	8.6	<10	0.1	3.9	<0.1	<550	<1700	<23	<0.15	L
VC8	0.20	0.90	<0.1	15	6.1	7.4	29	46	0.2	3.9	0.1	<550	<1700	<23	<0.15	L
VC8	0.90	1.90	<0.1	5.0	1.3	4.0	8.3	<10	0.1	1.0	<0.1	<550	<1700	<23	<0.15	L
VC8	1.90	2.90	<0.1	5.6	1.5	4.4	5.9	13	0.1	1.3	<0.1	<550	<1700	<23	<0.15	L
VC8	2.90	3.90	<0.1	8.3	2.6	6.3	8.0	17	0.1	2.0	<0.1	<550	<1700	<23	<0.15	L
VC8	6.00	6.90	<0.1	11	3.4	8.4	11	22	0.1	2.4	<0.1	<550	<1700	<23	<0.15	L
VC8	8.90	9.90	<0.1	6.9	2.3	4.4	11	15	0.2	3.8	<0.1	<550	<1700	<23	<0.15	L
G2*	NA	NA	<0.6	30	56	10	38	130	0.1	8	<1	NM	NM	NM	NM	L
Criteria	LCEL		1.5	80	65	40	75	200	0.5	12	1	550	1700	23	0.15
	UCEL		4	160	110	40	110	270	1	42	2	3160	9600	180	0.15

Note:

1. Values in underline indicate exceedance of LCEL under ETWB TCW No. 34/2002.

2. LMW = Low molecular weight PAHs, that is, acenaphthene, acenaphthylene, anthracene, fluorene, naphthalene and phenanthrene.

3. HMW = High molecular weight PAHs, that is, benzo[a]anthracene, benzo[a]pyrene, chrysene, dibenzo[a,h]anthracene, fluoranthene, pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno [1,2,3-c,d]pyrene and benzo[g,h,i]perylene.

* Sample depth at seabed

NM – Not measured

5.5.35 The chemical testing results indicated that the sediment at Stations VC18 and G1 in close vicinity of the Phase III reclamation area was classified as Category H (refer to Section 11). To minimize any potential adverse impacts and as a mitigation measure, drained reclamation method with marine mud left in place (and using DCM beneath seawalls) is proposed for the Phase II and Phase III reclamation to prevent dredging. DCM is a more environmentally friendly method for seawall construction as compared to conventional dredging method. DCM would involve injection of cement into the materials underlying the seawalls and mixing the cement with the in-situ material for strengthening. A blanket layer of sand fill would be placed on top of the mud before the DCM treatment to avoid escape of cement slurry into the water and disturbance of sediment fines during the mixing. Thus, minimal sediment loss is expected from the DCM treatment.

5.5.36 Filling activities will be carried out during the seawall construction and the reclamation period. It is assumed that the sediment loss rate during the reclamation period would be negligible, as the filling (and/or dredging) activities during the reclamation period for Phase I, Phase II and Phase III would be carried out behind the completed seawall. The sediment plume generated during filling and/or dredging will be effectively contained within the reclamation area. Normally, fines content in the filling materials for seawall construction would be negligible and loss of fills during seawall construction is therefore not expected. Thus, dredging impact during Phase I seawall construction is considered most critical, which is also due to the close vicinity of the works to identified ecological sensitive receivers. Nevertheless, impact due to filling activities was also included in the Phase I modelling exercise for conservative assessment (see Section 5.5.42 below). Modelling for construction phase impact will therefore cover the Phase I works only.

5.5.37 An indication of the likelihood of release of metals and micro-organic from the sediment during dredging is given by the results of the elutriation tests from the site investigation works. If the contaminant levels are higher in the elutriates in comparison with the blanks (marine water from the same site), it can be concluded that the contaminants are likely to be released into the marine waters during dredging activities.

5.5.38 The elutriate results of the marine site investigation carried out in FSIETKO and the site investigation conducted under this Project were reviewed. Elutriate samples were only collected at G2 and G3 under the FSIETKO and V5 and V13 under this Study (refer to Figure 11.1). Table 5.18b shows a summary of the elutriate test results.

Table 5.18b Elutriate Test Results from Marine Ground Investigation Works under Feasibility Study for IETKO and this Study

Sampling Location	Metals Content (ug/L)									(ug/L)			(ng/L)
	Cd	Cr	Cu	Ni	Pb	Zn	As	Hg	Ag	LMW PAHs	HMW PAHs	PCBs	TBT
G2	<0.5	<10	<2	<5	<2	10	4	<2	<2	NM	NM	NM	NM
G3	<0.5	16	<2	<5	<2	10	6	<2	<2	NM	NM	NM	NM
Blank 1	<0.5	<10	<2	<5	<2	<5	<3	<2	<2	NM	NM	NM	NM
V5	0.8	45	420	26	40	76	25	4.1	2.1	<0.1	<0.1	<0.01	<15
Blank 2	0.6	5.2	12	5.3	3.9	96	4.2	4.2	2.5	<0.1	<0.1	<0.01	<15
V13	0.3	26	380	19	41	210	25	4.1	2.1	<0.1	<0.1	<0.01	<15
Blank 3	0.6	4.6	390	5.9	2.0	140	2.0	3.6	1.0	<0.1	<0.1	<0.01	<15

Note:

NM – Not measured

Blank 1 - Blank data to compare against the elutriate test results at G2 and G3.

Blank 2 - Blank data to compare against the elutriate test results at V5.

Blank 3 - Blank data to compare against the elutriate test results at V13.

5.5.39 It is considered that the sampling results for Stations G3, V5 and V13 are not representative for the assessment of dredging impact as they are considered far away from the proposed dredging area for Phase 1 reclamation (refer to Figure 11.1). The elutriate test results for G2, which is relatively close to the dredging site, indicated that the most of the metals (except Zn and As) in the elutriates were not higher than the blank results. It is therefore considered that the metals are unlikely to be released into the marine waters during dredging activities. The sediment quality results in Table 5.18a showed that the potential impact from PAHs, PCBs and TBT during dredging should be low (all measured values are under the detection limit). The potential release of metals during Phase I dredging is quantitatively assessed in Section 5.7. There is no existing legislative standard or guideline for individual heavy metals in marine waters. The UK Water Quality Standards for Coastal Surface Water ⁽[12]⁾ is adopted as the assessment criteria for metals.

Sediment Plume Modelling

5.5.40 The SS concentration in the water column may increase as a result of the dredging and filling activities during the reclamation works. The Junk Bay Model was used to model the dispersion of sediment during dredging and filling. The hydrodynamic conditions generated using the Junk Bay Model provide basic hydrodynamic information for sediment plume modelling. The processes of settling of sediment particles and exchange of sediment particles between the water column and the seabed govern the sediment transport. Sediment deposition only occurs when the bed shear stress is below a critical shear stress whereas erosion occurs when the bed shear stress is above the critical shear stress. The deposition rate and erosion rate can be calculated using the following equations:

(1) Bed Shear Stress (τ) < Critical Shear Stress for Deposition (τ_d = 0.05 Pascal)
Deposition rate = V_s C_b (1 - τ / τ_d)

Where: V_s = settling velocity (= 43 m/day); and

C_b = bottom layer SS concentration

(2) Bed Shear Stress (τ) > Critical Shear Stress for Erosion (τ_e = 0.4 Pascal)
Erosion rate = R_e (τ / τ _e - 1)

Where: R_e = erosion coefficient (= 0.0002 kg/m²/s).

Sediment Loss due to Dredging for Phase I Seawall Construction

5.5.41 It is assumed that closed grab dredgers will be used for sediment dredging in the WCR reclamation. The total volume of sediments to be dredged for the Phase I seawall construction and Phase I reclamation was estimated to be about 20,000 m³. According to the proposed reclamation programme, the sediment will be dredged for 27 days. The typical bucket sizes of the grabs of the dredgers will be from about 6 m³ to 8 m³ and the capacity in the hold will be about 1000 tonnes. The percentage of files in the dredged mud would range from 90% to 100%. It is assumed that the maximum dredging rate would be 1,400 m³/day. The maximum dredging rate was estimated with reference to the tentative marine construction programme as shown in Appendix 2.2.

Based on geotechnical information, the dry density of marine mud is 1,080 kg/m³. By assuming the loss rate of 5%, the calculation of the sediment loss rate for dredging is detailed below:

Dredged volume = 20,000 m³

Duration of dredging = 27 days

Working hour = 12 hours per day

Dry Density of marine mud = 1,080 kg/m³

Maximum dredging rate = 1,400 /12/60/60 = 0.0324 m³/s

Sediment loss rate for dredging = 0.0324 ´ 1080 ´ 5% = 1.75 kg/s

Loss of Fines due to Filling for Phase I Seawall Construction

5.5.42 Normally, fines content in the filling materials for seawall construction would be negligible and loss of fills during seawall construction is not expected. However, in view of the close proximity of the Phase I work to the ecological sensitive receivers, it is assumed that loss of fines from seawall filling will take place concurrently with the loss of sediment due to dredging at the Phase I seawall for conservative assessment. Assumptions for deriving the loss rate of fines from filling operation are described in the subsequent sections.

5.5.43 Marine construction works will be carried out six days per week for total 12 working hours each day from 7a.m. to 7p.m. It is assumed that bottom dumping barge will be used to dump sand and public fill. The amount of sandfill to be dumped each day would be about 3,000 m³. Pelican barge would be used for the sand filling activities. Dump volume per barge (or per dump cycle) would be about 250 m³. The time required for dumping all the fills carried on the barge (or the duration of each dump cycle) would be approximately 30 minutes. It is assumed that a maximum of two barges would be engaged each day for the filling operation but the two barges would not be working concurrently. Filling operation would be carried out by only one barge at a time. It is assumed that there would be a total of 12 dump cycles each day with a dump interval of 30 minutes.

5.5.44 Negligible fine content is normally expected in fills for seawall construction. However, for conservative assessment, a fine content of 5% has been assumed in the sandfill to be used for Phase I seawall filling. The loss rate due to filling was calculated by multiplying the maximum filling rate by the percentage loss rate by the dry density of the sand fill. It is also assumed that the loss of fine portion during filling is 5%. Details of the calculation are shown in Table 5.19.

Table 5.19 Sediment Loss Rate for Filling During the Phase I Seawall Construction

Description	Phase I
Total volume of sandfill (m^3)	55,000
Duration of sand filling (working day)	19
Dump volume per day (m^3)	3,000
Number of dump cycle per day	12
Duration of each dump cycle (hour)	0.5
Dump volume for each dump cycle (m^3)	250
Dry density of sandfill (kg/m^3)	1,680 **
Filling rate (m^3/s)	0.1389
Percentage of fines in the filling materials (%)	5
Filling rate of fines (kg/s)	11.67
Portion of fines lost to the marine environment (%)	5
Loss of fines for filling (kg/s)	0.58

** Based on the approved EIA for Wan Chai Development Phase II.

Details of Modelling Scenario for Phase I Seawall Construction

5.5.45 One scenario, namely Scenario A, is considered in sediment plume modelling. Table 5.20Table 5.20Table 5.20Table 5.20 summarises the details. Scenario A covers the situation where the dredging and filling activities are carried out concurrently at the southern area of the reclamation site as a worst-case scenario. Figure 5.8a shows the assumed dredging and filling locations and the nearby sensitive receivers. Figure 5.8b is a zoom-in plot of the assumed dredging and filling locations. According to the proposed reclamation programme, Phase I works would commence in 2010. The construction of CBL will be carried out after completion of the WCR reclamation. Therefore, the existing coastline of Junk Bay for 2003 baseline condition was adopted for modelling of Phase I seawall construction. For areas outside Junk Bay, the coastline configuration for year 2011/2016 as shown in Figure 5.6 was used.

Table 5.20 Scenario for Sediment Plume Modelling

Scenario	Location of Sediment loss (Figures 5.8a and 5.8b	Coastline Configuration for hydrodynamic calculation	Activity	Maximum Sediment Release Rate (kg/s)
A	D1	2011/2016 baseline without WCR and CBL	Dredging activity for the construction of Phase I Seawall	1.75 kg/s
	F1		Filling activity for the construction of Phase 1 seawall	0.58 kg/s

5.5.46 The loss rates in Table 5.20 were estimated using a working rate of 6 days/week. For conservative assessment, these loss rates were input into the model for 7 days per week. The constant sediment loss rate from dredging was adopted throughout the whole working period (i.e. total 12 hours from 7a.m to 7p.m) for each of the 15 simulation days. For loss of fines during filling, the constant rate was applied intermittently between 7a.m. and 7p.m. on each of the 15 simulation days to take into account the dumping features as described in Section 5.5.43 and Table 5.19 above (i.e. The model included a total 12 dump cycles each day between 7a.m. and 7p.m. and a dump interval of 30 minutes, and during each dump cycle, a continuous filling discharge rate of 0.58 kg/s was included).

5.6 Identification of Environmental Impact

Construction Phase

General Construction Activities

5.6.1 The land-based construction works would have the potential to cause water pollution. Various types of construction activities may generate wastewater. These include general cleaning and polishing, wheel washing, dust suppression and utility installation. These types of wastewater would contain high concentrations of suspended solids. Impacts could also result from the accumulation of solid and liquid waste such as packaging and construction materials, and sewage effluent from the construction work force involved with the construction. If uncontrolled, these could lead to deterioration in water quality. Contaminated discharges and sewage effluent could also lead to localised increase in ammonia and nitrogen concentrations in the marine environment.

Construction Site Runoff

5.6.2 During a rainstorm, site runoff generated would wash away the soil particles. The runoff is generally characterised by high concentrations of suspended solids. Release of uncontrolled site runoff would increase the SS levels and turbidity in the nearby water environment.

5.6.3 Wind blown dust would be generated from exposed soil surfaces in the works areas. It is possible that wind blown dust would fall directly onto the nearby water bodies when a strong wind occurs. Dispersion of dust within the works areas may increase the SS levels in surface runoff causing a potential impact to the nearby sensitive receivers.

Accidental Spillage

5.6.4 A large variety of chemicals may be used during construction activities. These may include surplus adhesives, spent paints, petroleum products, spent lubrication oil, grease and mineral oil, spent acid and alkaline solutions/solvent and other chemicals. Accidental spillage of chemicals in the works areas may contaminate the surface soils. The contaminated soil particles may be washed away by construction site runoff or storm runoff causing water pollution.

Construction Works at Storm Culvert or in Close Proximity of Inland Water or Seafront

5.6.5 Construction of the landing steps at the seawall of TCS would involve excavation of fill material and dredging for the construction of rubble mound foundation. Construction of northern and southern footbridges will be carried out in close proximity of the EDC. Potential water quality impacts may arise from these construction activities due to their close vicinity to the inland water or marine water. Construction of piled deck at the downstream section of western drainage box culvert would involve demolition of existing temporary culvert, excavation (including dredging) of fill material, piling (bored piles or driven piles) and construction of deck structure. These piled decking works as well as the proposed culvert realignment works at Tiu Keng Leng Area 72 and storm diversion works for WCR reclamation may pollute the storm water in the box culvert or inland waters due to potential release of construction wastes. Construction wastes are generally characterized by high concentration of SS and elevated pH. Adoption of good house keeping and mitigation measures would reduce the generation of construction wastes and potential water pollution. The implementation of measures to control runoff and drainage will be important for the construction works adjacent to the inland water or marine water in order to prevent runoff and drainage water with high levels of SS from entering the water environment. In addition, for any construction activities to be conducted near the WSD saltwater pumping station at Area 86, implementation of suitable pollution control measures will be required to prevent sediment and pollutants from discharging into the sea. With the implementation of adequate construction site drainage and the provision of mitigation measures as described in Section 5.8, it is anticipated that unacceptable water quality impacts would not arise.

Construction Activities near Landfill Site

5.6.6 Groundwater generated during construction of the northern cycle track footbridge and southern footbridge as well as the proposed sewage pumping station for TKO landfill development may potentially be contaminated by leachate seepage from the TKO landfill due to the close proximity of the works to the landfill site boundary. Mitigation measures are recommended in Section 5.8 to address the water quality concern.

Marine Construction Works

5.6.7 Potential water quality impacts may occur from dredging and filling activities. Appendix 2.2 and Figure 2.35 shows the reclamation phasing of WCR. As presented in Section 5.5, one worst-case construction scenario (Scenario A) has been modelled.

5.6.8 Potential impacts on water quality from dredging and filling will vary according to the quantities and level of contamination, as well as the nature and locations of the water sensitive receivers at or near the dredging sites.

5.6.9 Based on the results of the marine site investigation, the marine sediment to be dredged for the construction of Phase 1 reclamation is not expected to be contaminated. Details of the baseline sediment quality are discussed in Sections 5.5.33 to 5.5.37 and are detailed in Section 11. The water quality impact due to the potential release of contaminants from the dredging operation would be minimal. Thus, key water quality concern during dredging works would be the disturbance of the marine bottom sediment, causing an increase in SS & nutrient concentrations in the water column and forming sediment plume along the tidal flows with possible consequence of reducing DO levels.

Operation Phase

Hydrodynamics and Water Quality Impact

5.6.10 The WCR reclamation and CBL may affect the water levels, current velocity, and tidal flushing in the Junk Bay and, potentially, in the Victoria Harbour. In addition, the changes in the hydrodynamics in Junk Bay and Victoria Harbour may affect the pollutant distribution patterns from sewage outfalls and stormwater culverts into the surrounding waters.

Water Quality Impact on EDC and Inner Junk Bay

5.6.11 The EDC and inner Junk Bay are proposed to be used for secondary contact recreation. The potential release of landfill leachate together with other pollutant discharges within the TKO catchment under the ultimate scenario may pose a water quality constraint on the proposed beneficial use. Based on the long-term field data collected for the TKO Stage I Landfill presented in Table 5.10, there is no elevated leachate levels that exceed the target limits at TKO Stage I Landfill and there is no evidence to suggest that leachate from TKO Landfill Stage I is adversely impacting the marine water quality. In the event of any emergency sewage bypass from the TKO PTW, the water quality at the EDC and inner Junk Bay may also be adversely affected. The WQO of E. coli for secondary contact recreation is 610 no./100mL which is an annual geometric mean.

Reservoir Cleansing

5.6.12 Regular cleansing of the proposed Pak Shing Kok high level fresh water service reservoir would be required during operational phase. Cleansing will be conducted by lowering the water in the service reservoir by discharging the water to the stormwater drainage system. The remaining water in the bottom layer (the sludge) will be pumped out and disposed by a licensed waste collector. After the cleansing operation, the cleansing effluent will also be collected by a licensed waste collector and will not be discharged into the storm system. No significant water quality impact is therefore expected during the operational phase.

5.7 Prediction and Evaluation of Environmental Impacts

Operational Phase Impact from WCR Reclamation and CBL

Hydrodynamics

5.7.1 Figures DH1 to DH4 and Figures WH1 to WH4 in Appendix 5.3 show the time series comparison plots of momentary flow and accumulated flow at selected cross sections for the ultimate condition with no WCR and CBL (Scenario 2) and the ultimate condition (Scenario 3a). Momentary flow represents the instantaneous flow rate at a specific time in m³/s whereas accumulated flow represents the total flow accumulated at a specific time in m³. The cross sections selected for comparisons are Eastern Buffer, Victoria Harbour, Junk Bay and inner Junk Bay. Figure 5.9 shows the locations of these cross sections. These cross sections are defined in the hydrodynamics model through which the flux is determined and stored by the model as a function of time. As shown in Figures DH1, DH2, WH1 and WH2 in Appendix 5.3, no noticeable differences in momentary flow and accumulated flow are observed between Scenario 2 and Scenario 3a for both wet and dry seasons at Eastern Buffer, Victoria Harbour and Junk Bay. Figures DH3, DH4, WH3 and WH4 in Appendix 5.3 however showed some slight decreases in momentary flow and accumulated flow across inner Junk Bay due to the TKO development. The hydrodynamic impact is however considered minimal.

Water Quality

5.7.2 For assessment of the potential impact during the operational phase of the Project, the model results are presented as contour plots for DO, BOD₅, UIA, TIN, E. coli, SS, sedimentation rate and salinity. The water quality contour plots for 2003 baseline condition (Scenario 1), ultimate scenario with no WCR and CBL (Scenario 2) and ultimate condition (Scenario 3a) are shown in Appendix 5.4a, Appendix 5.5a and Appendix 5.6a respectively for dry season and Appendix 5.4b, Appendix 5.5b and Appendix 5.6b respectively for wet season. These contour plots are presented as arithmetic averages over the 15-day simulation period except for the E. coli levels which are geometric means and the sedimentation rates which are the maximum values.

5.7.3 The predicted water quality at selected indicator points is tabulated in Table 5.21 to Table 5.26. The results in these tables are the average of the model output except for the maximum sedimentation rates in Table 5.23 and Table 5.24 which are the peak values over the simulation period. Locations of the indicator points are shown in Figure 5.2. Table 5.21 to Table 5.22 present the predicted water quality at EDC. Table 5.23 and Table 5.24 show the predicted water quality at selected indicator points in Junk Bay and nearby marine waters. The data for seawater and cooling water intakes as shown in Tables 5.25 and Table 5.26 are the results predicted in the middle water layer where the intake points are located. Bolded values in tables represent non-compliances of WQO.

Water Quality at EDC – Ultimate Condition – Unmitigated Scenario (Scenario 3a)

5.7.4 Appendix 5.6c, Table 5.21 and Table 5.22 present the predicted water quality at EDC under the ultimate scenario. The predicted E. coli levels exceeded the WQO of 610 no./100mL in the upper half of the EDC for both dry and wet seasons (Appendix 5.6c). The predicted mean values for E.coli were 2216 and 2110 no./100mL for dry season and wet season respectively. The predicted dry season SS levels in the upper EDC (Station EDC1) ranged from 33.1 to 52.3 mg/L with a median value of 43.4 mg/L which breached the inland WQO of 25 mg/L for annual median. For wet season, the predicted BOD₅ at EDC also exceeded the inland WQO of 5 mg/L. The wet season BOD₅ values at Station EDC1 (upper part of EDC) ranged from 4.9 to 9.0 mg/L with a mean value of 7 mg/L whilst the predicted values at Station EDC2 (lower part of EDC) ranged from 2.8 to 6.9 mg/L with a mean value of 4.6 mg/L.

5.7.5 It should be noted that similar level of exceedances was also predicted for Scenario 2 (ultimate scenario without WCR and CBL). The presence of the WCR and CBL would cause no significant change in the water quality at EDC in comparison with the “without WCR and CBL” condition under Scenario 2. The extent of impact is considered similar between Scenario 2 (without WCR and CBL) and Scenario 3a (with WCR and CBL). The model predicted that the Project would not contribute any WQO exceedances.

Water Quality at EDC - Ultimate Condition – Mitigated Scenario (Scenario 3b)

5.7.6 In view of the predicted non-compliance of E.coli level for secondary contact recreation in the upper part of EDC. Drainage diversion works are proposed at Town Centre South as a mitigation measure to improve the water quality at EDC during the operational phase. Figure 5.1 shows the existing drainage systems of the TKO catchment. Figure 5.10 shows the proposed drainage diversion works at Town Centre South. Two existing drainage outfalls into the EDC will be diverted to the southern boundary of TCS to enhance the dispersion of pollutants. The proposed drainage diversions would be carried out under the construction of local infrastructure to serve Town Centre South which is scheduled between Jan 2008 and Dec 2010. Details of the diversion are described as follows:

Partial diversion of existing outfall L (refer to Figure 5.1):

· 10% of the total pollution loading (i.e. 3.59E+12 no./day out of 3.59E+13 no./day of E.coli loading) at the existing outfall L would be diverted to outfall C

· 50% of the total pollution loading (i.e. 1.80E+13 no./day out of 3.59E+13 no./day of E.coli loading) at the existing outfall L would be diverted to outfall N

Diversion of existing outfall M (refer to Figure 5.1):

· 100% of total pollution loading (i.e. 2.17E+13 no./day of E.coli Loading) at the existing outfall M will be diverted to outfall N

5.7.7 Water quality modelling was carried out for the mitigated scenario (Scenario 3b) with the proposed drainage diversion under the ultimate development condition. Appendix 5.7c presents the contour plots for the mitigated scenario. Table 5.21 and Table 5.22 summarize the results. The results for Scenario 2, Scenario 3a and Scenario 3b are presented as time-series plots for comparison in Appendix 5.8b.

5.7.8 With the proposed drainage diversion works, the mean depth-averaged E.coli at the EDC would comply with the WQO for secondary contact recreation of 610 no./100mL for both dry and wet seasons (Table 5.21 and Table 5.22). It was also predicted that the E.coli levels would meet the WQO for secondary contact recreation in most areas of Junk Bay except for only a few localized areas in the vicinity of the drainage outfalls at the seawall as shown in Appendix 5.7c.

5.7.9 As shown in Table 5.21, the predicted SS values at Station EDC1 for dry season ranged from 32.6 to 51.4 mg/L with a median of 42.8 mg/L which breached the inland WQO of 25 mg/L for annual median. Appendix 5.8a shows the time-series plot for the predicted dry season SS concentrations at EDC1 and EDC2.

5.7.10 For the wet season results under Scenario 3b, the predicted BOD₅ levels at Stations EDC1 and EDC2 in the wet season ranged from 2.9 to 8.9 mg/L as compared to the inland WQO of 5 mg/L. The % time in non-compliance for BOD₅ at Stations EDC1 and EDC2 during wet season was 98.6% and 33.2% respectively. Appendix 5.8a shows the time-series plot for the predicted wet season BOD₅ concentrations at EDC1 and EDC2.

5.7.11 The dry season mean UIA levels predicted at EDC1 and EDC2 of 0.15 mg/L and 0.074 mg/L respectively also exceeded the WQO of 0.021 mg/L. The wet season UIA levels are considered much lower than the dry season levels. The predicted wet season UIA levels complied very well with the WQO.

5.7.12 It should be noted that EDC1 is located at the very upstream of EDC (Figure 5.2) which is outside the boundary of the proposed secondary contact recreation zone as shown in Figure 5.1a. All the predicted exceedances at EDC were not caused by the Project as the same level of exceedances was also predicted for the “2016 without WCR and CBL” scenario (i.e. Scenario 2).

Table 5.21 Predicted Water Quality at EDC for Dry Season (Operational Phase)

Station (refer to Figure 5.2)		Depth Averaged DO (mg/L)	Bottom DO (mg/L)	Depth-averaged E.coli** (no./100mL)	Depth-averaged UIA (mg/L)	Depth-averaged TIN (mg/L)	Depth-averaged BOD5 (mg/L)	Depth-averaged SS (mg/L)
WQO for inland waters in Junk Bay WCZ		≥4	-	≤1000^R	≤0.021 (Annual mean)	-	≤5	≤25 (Annual median)
WQO for secondary contact recreation subzone		-	-	≤610 (Annual Geometric Mean)	-	-	-	-
2003 Baseline (Scn 1)
EDC1 (Eastern Channel – upstream)	Min	4.34	4.04	751	0.146	2.93	0.44	37.2
	Max	5.22	5.38	5750	0.261	5.59	0.78	102.6
	Mean **	4.69	4.67	2368	0.211	4.50	0.60	67.8
	Median	-	-	2328	-	-	-	66.8
	10%ile	4.43	4.39	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	4.80	4.79	1	0.021	0.36	0.13	5.1
	Max	6.11	6.11	5059	0.217	4.60	0.64	70.0
	Mean **	5.64	5.65	191	0.096	1.84	0.28	24.5
	Median	-	-	204	-	-	-	21.4
	10%ile	5.17	5.19	-	-	-	-	-
Ultimate Scenario with no WCR & CBL (Scn 2)
EDC1 (Eastern Channel – upstream)	Min	4.18	4.14	1238	0.179	5.11	0.69	46.4
	Max	4.75	4.89	3726	0.242	7.21	0.97	71.3
	Mean **	4.43	4.44	2249	0.207	6.12	0.84	60.2
	Median	-	-	2261	-	-	-	42.8
	10%ile	4.23	4.20	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	4.57	4.57	4	0.044	1.05	0.27	10.7
	Max	6.04	6.03	4029	0.203	6.03	0.82	57.8
	Mean **	5.45	5.46	255	0.111	2.93	0.47	27.4
	Median	-	-	235	-	-	-	25.9
	10%ile	4.96	4.99	-	-	-	-	-
Ultimate Scenario – unmitigated (Scn 3a)
EDC1 (Eastern Channel – upstream)	Min	4.76	4.74	1136	0.133	3.67	0.90	33.1
	Max	5.49	5.54	3529	0.183	5.44	1.44	52.3
	Mean **	5.08	5.09	2216	0.155	4.55	1.21	43.4
	Median	-	-	2289	-	-	-	43.5
	10%ile	4.82	4.79	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	5.29	5.32	16	0.041	1.07	0.50	11.3
	Max	6.41	6.40	3320	0.142	4.15	1.14	39.9
	Mean **	6.01	6.01	260	0.076	2.04	0.74	19.9
	Median	-	-	227	-	-	-	19.2
	10%ile	5.68	5.71	-	-	-	-	-
Ultimate Scenario – mitigated (Scn 3b)
EDC1 (Eastern Channel – upstream)	Min	5.04	5.01	66	0.129	3.59	0.79	32.6
	Max	5.74	5.76	1509	0.176	5.31	1.34	51.4
	Mean **	5.33	5.32	375	0.150	4.44	1.08	42.7
	Median	-	-	375	-	-	-	42.8
	10%ile	5.09	5.06	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	5.50	5.52	20	0.040	1.05	0.50	11.3
	Max	6.48	6.46	843	0.137	4.04	1.02	39.2
	Mean **	6.10	6.10	80	0.074	2.00	0.71	19.7
	Median	-	-	68	-	-	-	18.9
	10%ile	5.83	5.85	-	-	-	-	-

Notes:

1. Bolded value represents non-compliances of WQO.

R. WQO for E. coli level is the running median of the 5 most recent consecutive samples taken at intervals between 7 and 21 Days.

** Values are arithmetic mean over the 15-day simulation period except for E.coli mean levels which are geometric means.

Table 5.22 Predicted Water Quality at EDC for Wet Season (Operational Phase)

Station (refer to Figure 5.2)		Depth Averaged DO (mg/L)	Bottom DO (mg/L)	Depth-averaged E.coli** (no./100mL)	Depth-averaged UIA (mg/L)	Depth-averaged TIN (mg/L)	Depth-averaged BOD5 (mg/L)	Depth-averaged SS (mg/L)
WQO for inland waters in Junk Bay WCZ		≥4	-	≤1000^R	≤0.021 (Annual mean)	-	≤5	≤25 (Annual median)
WQO for secondary contact recreation subzone		-	-	≤610 (Annual Geometric Mean)	-	-	-	-
2003 Baseline (Scn 1)
EDC1 (Eastern Channel – upstream)	Min	7.03	6.13	192	0.004	0.50	2.8	11.1
	Max	14.00	13.33	5351	0.035	1.82	8.1	26.3
	Mean **	10.82	9.94	803	0.013	0.95	5.7	19.2
	Median	-	-	786	-	-		19.3
	10%ile	8.72	7.85	-	-	-
EDC2 (Eastern Channel –downstream)	Min	6.76	5.95	7	0.004	0.23	2.0	7.8
	Max	12.94	12.76	2240	0.023	1.19	6.7	22.8
	Mean **	9.71	8.77	514	0.010	0.58	3.9	13.3
	Median	-	-	654	-	-		12.9
	10%ile	8.12	7.04	-	-	-
Ultimate Scenario with no WCR & CBL (Scn 2)
EDC1 (Eastern Channel – upstream)	Min	8.32	7.54	568	0.025	1.45	5.3	17.7
	Max	11.45	11.38	3371	0.063	2.75	9.9	29.5
	Mean **	9.93	9.37	1409	0.044	2.15	7.6	24.1
	Median	-	-	1574	-	-	-	24.1
	10%ile	8.78	8.18	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	7.90	6.32	83	0.009	0.72	3.3	11.9
	Max	11.70	11.73	1063	0.035	1.77	7.7	25.6
	Mean **	9.58	9.16	354	0.019	1.10	5.2	17.7
	Median	-	-	350	-	-	-	17.6
	10%ile	8.41	7.57	-	-	-	-	-
Ultimate Scenario – unmitigated (Scn 3a)
EDC1 (Eastern Channel – upstream)	Min	8.25	7.34	818	0.023	1.28	4.9	16.5
	Max	11.90	11.08	3845	0.054	2.38	9.0	27.0
	Mean **	10.13	9.13	2110	0.038	1.84	7.0	22.3
	Median	-	-	2200	-	-	-	22.2
	10%ile	8.98	7.94	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	7.38	5.87	91	0.009	0.59	2.8	10.9
	Max	11.05	10.88	853	0.027	1.36	6.9	22.0
	Mean **	9.29	8.57	306	0.016	0.90	4.6	16.0
	Median	-	-	302	-	-	-	15.9
	10%ile	8.27	7.06	-	-	-	-	-
Ultimate Scenario – mitigated (Scn 3b)
EDC1 (Eastern Channel – upstream)	Min	8.43	7.52	94	0.022	1.26	4.8	16.4
	Max	12.31	11.33	549	0.051	2.32	8.9	26.5
	Mean **	10.42	9.34	252	0.035	1.80	6.9	22.0
	Median	-	-	272	-	-	-	21.9
	10%ile	9.16	8.14	-	-	-	-	-
EDC2 (Eastern Channel –downstream)	Min	7.43	5.87	100	0.008	0.58	2.9	10.9
	Max	11.19	11.08	1011	0.026	1.33	6.9	21.9
	Mean **	9.40	8.64	345	0.015	0.89	4.7	16.0
	Median	-	-	367	-	-	-	15.9
	10%ile	8.34	7.10	-	-	-	-	-

Notes:

1. Bolded value represents non-compliances of WQO.

R. WQO for E. coli level is the running median of the 5 most recent consecutive samples taken at intervals between 7 and 21 Days.

** Values are arithmetic mean over the 15-day simulation period except for E.coli mean levels which are geometric means.

Water Quality in Junk Bay and the Nearby Marine Waters

5.7.13 As shown in Appendix 5.4, Appendix 5.5 and Appendix 5.7, the modelling results for 2003 baseline condition (Scenario 1), ultimate scenario with no WCR and CBL (Scenario 2) and ultimate scenario (Scenario 3b – mitigated scenario) are in general similar. Full compliance with the marine WQO would be achieved at all selected sensitive receivers including the TKO saltwater intake (see Table 5.23 to Table 5.26). The predicted E.coli levels were predicted to be generally high in Shau Kei Wan Typhoon Shelter (T4) and Chai Wan Typhoon shelterCargo Basin (T5) for all the assessment scenarios which was essentially due to the pollutant discharge from the local sources.

5.7.14 The comparison between the modelling results of Scenario 2 (ultimate condition with no WCR and CBL) and Scenario 3b (ultimate condition – mitigated) indicated that there was no significant difference in the extent of water quality impact between the scenarios. The model predicted that the Project would not contribute any WQO exceedances. Appendix 5.8b shows the time-series comparison plots for relevant parameters for selected sensitivity receivers, namely S1, S2 and W1. These three sensitive receivers were selected as they are closest to the Project site. These plots are intended to shows the variation of pollutant levels over the tidal cycle. As shown in Appendix 5.8b, full compliance with the relevant water quality objectives could be achieved during operational phase of the Project.

Acceptability of Using EDC and Inner Junk Bay for Secondary Contact Recreation

5.7.15 Under the mitigated ultimate scenario (Scenario 3b), the predicted mean E.coli levels at EDC and most areas of inner Junk Bay would well below the WQO of 610 no./100 for both dry and wet seasons (Appendix 5.7). The predicted depth-averaged mean DO levels at EDC and inner Junk Bay would also well above the WQO of 4 mg/L. However, exceedance for UIA was predicted at the EDC in the dry season. It is recommended to conduct water quality field survey at EDC after the proposed drainage diversion works (as mentioned in Section 5.7.6) is completed to confirm the suitability of the proposed recreation uses at EDC. The field survey should be conducted at a frequency of twice per year in dry season and wet season respectively after operation of the drainage diversion works. The suitability of the proposed recreation uses at EDC should be continuously reviewed with reference to the field survey data. After a 3-year operation period, a review should be conducted to determine whether the field survey programme should be discontinued. Details of the survey programme are given in a separate Environmental Monitoring & Audit (EM&A) Manual.

Table 5.23 Predicted Water Quality at Selected Indicator Points for Dry Season (Operational Phase)

Indicator Point (refer to Figure 5.2)	Scenario	Depth-averaged DO 10 percentile (mg/L)	Bottom DO 10 percentile (mg/L)	Depth-averaged Salinity (ppt)	Depth-averaged TIN (mg/L)	Depth-averaged UIA (mg/L)	Depth-averaged SS (mg/L)	Depth-averaged E. coli (no./100mL)	Maximum Sedimentation Rate (g/m^2/day)
WQO for Junk Bay WCZ		≥4	≥2	≤10% change	≤0.3	≤0.021	≤30% increase	≤610 **	≤100 ^##
WQO for Eastern Buffer WCZ		≥4	≥2	≤10% change	≤0.4	≤0.021	≤30% increase	-	≤100 ^##
WQO for Victoria Harbour WCZ		≥4	≥2	≤10% change	≤0.4	≤0.021	≤30% increase	-	≤100 ^##
S1 (Junk bay Coral Site-South West), Junk Bay WCZ	2003 Baseline (Scn 1)	6.08	6.07	34.00	0.10	0.005	3.9	28	3.46
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.10	0.004	3.9	15	3.35
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.09	0.004	4.0	21	3.27
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.09	0.004	4.0	21	3.27
S2 (Junk bay Coral Site-Junk Island), Junk Bay WCZ	2003 Baseline (Scn 1)	6.08	6.08	34.00	0.09	0.005	3.8	21	3.35
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.10	0.004	3.9	19	3.26
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.10	0.004	4.0	21	3.28
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.10	0.004	4.0	21	3.28
S11 (Ngan Wan South Coral Site), Eastern Buffer WCZ	2003 Baseline (Scn 1)	6.08	6.08	34.00	0.08	0.004	3.9	23	3.38
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.08	0.003	3.9	33	3.33
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.08	0.003	4.0	27	3.30
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.08	0.003	4.0	27	3.30
T3 (San Ka Tsuen Typhoon Shelter), Victoria Harbour WCZ	2003 Baseline (Scn 1)	6.74	6.73	34.00	0.03	0.001	5.7	38	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.85	6.84	33.99	0.01	0.001	5.8	28	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	33.99	0.09	0.003	4.4	248	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	33.99	0.09	0.003	4.4	248	-
T4 (Shau Kei Wan Typhoon Shelter), Victoria Harbour WCZ	2003 Baseline (Scn 1)	5.38	5.36	34.00	0.11	0.006	4.0	2037	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.03	5.80	34.00	0.11	0.004	4.0	1909	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	33.99	0.10	0.004	4.1	627	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	33.99	0.10	0.004	4.1	627	-
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin), Eastern Buffer WCZ	2003 Baseline (Scn 1)	5.33	5.33	34.00	0.23	0.014	4.6	6677	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.10	0.004	4.2	2351	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.09	0.004	4.3	3204	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.09	0.004	4.3	3204	-
VM1 (EPD Marine Water Quality Monitoring Station), Victoria Harbour WCZ	2003 Baseline (Scn 1)	5.58	5.53	34.00	0.10	0.005	3.9	300	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.05	6.05	34.00	0.10	0.004	4.0	92	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.06	6.06	33.99	0.10	0.004	4.1	142	-
	Ultimate Scenario – mitigated (Scn 3b)	6.06	6.06	33.99	0.10	0.004	4.1	142	-
JM3 (EPD Marine Water Quality Monitoring Station), Junk Bay WCZ	2003 Baseline (Scn 1)	6.08	5.84	34.00	0.11	0.005	3.9	6	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	5.78	34.00	0.11	0.004	3.9	2	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.02	34.00	0.12	0.004	4.1	4	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.01	34.00	0.12	0.004	4.1	4	-
JM4 (EPD Marine Water Quality Monitoring Station), Junk Bay WCZ	2003 Baseline (Scn 1)	6.07	6.05	34.00	0.09	0.005	4.0	25	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.09	0.003	3.9	14	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.09	0.003	4.0	18	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.09	0.003	4.0	18	-
EM1 (EPD Marine Water Quality Monitoring Station), Eastern Buffer WCZ	2003 Baseline (Scn 1)	6.06	6.06	34.00	0.09	0.005	3.9	27	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.09	0.004	3.9	15	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.09	0.003	4.1	24	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.09	0.003	4.1	24	-
EM2 (EPD Marine Water Quality Monitoring Station), Eastern Buffer WCZ	2003 Baseline (Scn 1)	6.08	6.08	34.00	0.09	0.004	3.9	12	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.08	6.08	34.00	0.09	0.003	3.9	8	-
	Ultimate Scenario – unmitigated (Scn 3a)	6.08	6.08	34.00	0.08	0.003	4.0	16	-
	Ultimate Scenario – mitigated (Scn 3b)	6.08	6.08	34.00	0.08	0.003	4.0	16	-

** WQO for E.coli is applied for secondary contact recreation and fish culture subzones only.

^## WQO for sedimentation rate is applied for coral habitats only.

- Data not available.

Notes:

1. Bolded value represents non-compliances of WQO.

2. Data represent average of the model output except for the maximum sedimentation rates which are the peak values over the simulation period.

Table 5.24 Predicted Water Quality at Selected Indicator Points for Wet Season (Operational Phase)

Indicator Point (refer to Figure 5.2)	Scenario	Depth-averaged DO 10 percentile (mg/L)	Bottom DO 10 percentile (mg/L)	Depth-averaged Salinity (ppt)	Depth-averaged TIN (mg/L)	Depth-averaged UIA (mg/L)	Depth-averaged SS (mg/L)	Depth-averaged E.coli (no./100mL)	Maximum Sedimentation Rate (g/m^2/day)
WQO for Junk Bay WCZ		≥4	≥2	≤10% change	≤0.3	≤0.021	≤30% increase	≤610 **	≤100 ^##
WQO for Eastern Buffer WCZ		≥4	≥2	≤10% change	≤0.4	≤0.021	≤30% increase	-	≤100 ^##
WQO for Victoria Harbour WCZ		≥4	≥2	≤10% change	≤0.4	≤0.021	≤30% increase	-	≤100 ^##
S1 (Junk bay Coral Site-South West), Junk Bay WCZ	2003 Baseline (Scn 1)	5.37	5.33	27.28	0.20	0.0036	4.9	48	2.39
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.20	4.67	27.56	0.23	0.0036	5.2	26	3.28
	Ultimate Scenario – unmitigated (Scn 3a)	5.14	4.63	27.60	0.22	0.0036	5.2	34	3.15
	Ultimate Scenario – mitigated (Scn 3b)	5.14	4.63	27.60	0.22	0.0036	5.2	35	3.15
S2 (Junk bay Coral Site-Junk Island), Junk Bay WCZ	2003 Baseline (Scn 1)	5.33	4.72	27.34	0.20	0.0036	4.6	47	2.43
	Ultimate Scenario with no WCR & CBL (Scn 2)	4.90	4.58	27.60	0.22	0.0036	5.0	26	3.21
	Ultimate Scenario – unmitigated (Scn 3a)	4.74	4.58	27.68	0.22	0.0035	4.9	37	3.24
	Ultimate Scenario – mitigated (Scn 3b)	4.74	4.58	27.68	0.22	0.0035	4.9	37	3.24
S11 (Ngan Wan South Coral Site), Eastern Buffer WCZ	2003 Baseline (Scn 1)	5.32	4.62	27.66	0.18	0.0031	4.3	21	2.42
	Ultimate Scenario with no WCR & CBL (Scn 2)	4.64	4.58	28.10	0.20	0.0031	4.4	17	2.83
	Ultimate Scenario – unmitigated (Scn 3a)	4.67	4.58	28.09	0.19	0.0030	4.5	19	2.82
	Ultimate Scenario – mitigated (Scn 3b)	4.67	4.58	28.09	0.19	0.0030	4.5	19	2.82
T3 (San Ka Tsuen Typhoon Shelter), Victoria Harbour WCZ	2003 Baseline (Scn 1)	6.08	5.86	26.18	0.22	0.0033	5.3	243	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.49	5.44	25.88	0.27	0.0037	6.0	138	-
	Ultimate Scenario – unmitigated (Scn 3a)	5.38	5.15	26.02	0.27	0.0039	6.0	236	-
	Ultimate Scenario – mitigated (Scn 3b)	5.38	5.15	26.02	0.27	0.0039	6.0	236	-
T4 (Shau Kei Wan Typhoon Shelter) Victoria Harbour WCZ	2003 Baseline (Scn 1)	5.33	5.30	26.28	0.27	0.0053	4.7	1166	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.31	4.66	26.31	0.28	0.0051	5.7	1064	-
	Ultimate Scenario – unmitigated (Scn 3a)	5.29	4.60	26.60	0.27	0.0047	5.5	571	-
	Ultimate Scenario – mitigated (Scn 3b)	5.29	4.60	26.60	0.27	0.0047	5.5	571	-
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin), Eastern Buffer WCZ	2003 Baseline (Scn 1)	5.34	5.32	26.93	0.23	0.0045	5.6	3413	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.33	4.60	27.15	0.24	0.0039	5.5	509	-
	Ultimate Scenario – unmitigated (Scn 3a)	5.33	4.58	27.31	0.23	0.0037	5.3	336	-
	Ultimate Scenario – mitigated (Scn 3b)	5.33	4.58	27.31	0.23	0.0037	5.3	336	-
VM1 (EPD Marine Water Quality Monitoring Station), Victoria Harbour WCZ	2003 Baseline (Scn 1)	5.33	5.33	26.83	0.24	0.0044	4.6	364	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.25	4.65	26.91	0.26	0.0044	5.4	110	-
	Ultimate Scenario – unmitigated (Scn 3a)	4.93	4.61	26.98	0.25	0.0043	5.3	142	-
VM1	Ultimate Scenario – mitigated (Scn 3b)	4.93	4.61	26.98	0.25	0.0043	5.3	142	-
JM3 (EPD Marine Water Quality Monitoring Station), Junk Bay WCZ	2003 Baseline (Scn 1)	5.47	5.32	27.14	0.21	0.0037	5.1	69	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.35	4.64	27.34	0.24	0.0039	5.5	77	-
	Ultimate Scenario – unmitigated (Scn 3a)	5.37	4.63	27.34	0.24	0.0039	5.6	73	-
	Ultimate Scenario – mitigated (Scn 3b)	5.37	4.63	27.34	0.24	0.0039	5.6	75	-
JM4 (EPD Marine Water Quality Monitoring Station), Junk Bay WCZ	2003 Baseline (Scn 1)	5.33	5.07	27.32	0.20	0.0036	4.6	63	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.26	4.58	27.63	0.22	0.0035	5.0	28	-
	Ultimate Scenario – unmitigated (Scn 3a)	4.99	4.58	27.67	0.22	0.0035	4.9	41	-
	Ultimate Scenario – mitigated (Scn 3b)	4.99	4.58	27.67	0.22	0.0035	4.9	41	-
EM1 (EPD Marine Water Quality Monitoring Station), Eastern Buffer WCZ	2003 Baseline (Scn 1)	5.33	4.69	27.33	0.21	0.0036	4.5	92	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	4.64	4.58	27.65	0.22	0.0035	4.8	58	-
	Ultimate Scenario – unmitigated (Scn 3a)	4.61	4.58	27.73	0.22	0.0034	4.8	82	-
	Ultimate Scenario – mitigated (Scn 3b)	4.61	4.58	27.73	0.22	0.0034	4.8	82	-
EM2 (EPD Marine Water Quality Monitoring Station), Eastern Buffer WCZ	2003 Baseline (Scn 1)	5.33	4.59	27.52	0.20	0.0034	4.4	56	-
	Ultimate Scenario with no WCR & CBL (Scn 2)	4.61	4.58	27.88	0.21	0.0033	4.7	39	-
	Ultimate Scenario – unmitigated (Scn 3a)	4.60	4.58	27.90	0.21	0.0033	4.6	54	-
	Ultimate Scenario – mitigated (Scn 3b)	4.60	4.58	27.90	0.21	0.0033	4.6	54	-

** WQO for E.coli is applied for secondary contact recreation and fish culture subzones only.

^## WQO for sedimentation rate is applied for coral habitats only.

- Data not available.

Notes:

1. Bolded value represents non-compliances of WQO.

2. Data represent average of the model output except for the maximum sedimentation rates which are the peak values over the simulation period.

Table 5.25 Predicted Water Quality at Selected Cooling Water Intakes and Saltwater Intakes for Dry Season (Operational Phase)

Indicator Point (refer to Figure 5.2)	Scenario	DO (mg/L)	Salinity (ppt)	TIN (mg/L)	UIA (mg/L)	SS (mg/L)	E. coli (no./100mL)
WQO for WSD Saltwater Intake		> 2	-	-	-	<10	<20,000
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	2003 Baseline (Scn 1)	6.02	34.00	0.11	0.0056	4.0	142
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.10	34.00	0.10	0.0038	4.0	67
	Ultimate Scenario – unmitigated (Scn 3a)	6.18	34.00	0.10	0.0036	4.1	74
	Ultimate Scenario – mitigated (Scn 3b)	6.18	34.00	0.10	0.0036	4.1	74
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	2003 Baseline (Scn 1)	6.07	34.00	0.10	0.0050	3.9	589
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.10	34.00	0.10	0.0038	4.0	839
	Ultimate Scenario – unmitigated (Scn 3a)	6.15	34.00	0.09	0.0036	4.1	713
	Ultimate Scenario – mitigated (Scn 3b)	6.15	34.00	0.09	0.0036	4.1	713
W1 (Tseung Kwan O Salt Water Intake)	2003 Baseline (Scn 1)	6.11	34.00	0.17	0.0094	3.8	5
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.15	33.99	0.23	0.0093	4.0	6
	Ultimate Scenario – unmitigated (Scn 3a)	6.28	33.98	0.26	0.0091	4.7	7
	Ultimate Scenario – mitigated (Scn 3b)	6.28	33.98	0.26	0.0091	4.7	8
W2 (Yau Tong Salt Water Intake)	2003 Baseline (Scn 1)	6.06	34.00	0.11	0.0053	4.0	48
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.18	34.00	0.10	0.0035	4.0	40
	Ultimate Scenario – unmitigated (Scn 3a)	6.36	33.99	0.09	0.0032	4.4	38
	Ultimate Scenario – mitigated (Scn 3b)	6.36	33.99	0.09	0.0032	4.4	38
W3 (Cha Kwo Ling Salt Water Intake)	2003 Baseline (Scn 1)	6.02	34.00	0.11	0.0056	4.0	1600
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.09	34.00	0.10	0.0039	4.0	996
	Ultimate Scenario – unmitigated (Scn 3a)	6.14	33.99	0.10	0.0038	4.1	1068
	Ultimate Scenario – mitigated (Scn 3b)	6.14	33.99	0.10	0.0038	4.1	1068
W6 (Sai Wan Ho Salt Water Intake)	2003 Baseline (Scn 1)	6.00	34.00	0.11	0.0061	4.0	1452
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.07	33.99	0.11	0.0041	4.0	1170
	Ultimate Scenario – unmitigated (Scn 3a)	6.12	33.99	0.10	0.0038	4.1	681
	Ultimate Scenario – mitigated (Scn 3b)	6.12	33.99	0.10	0.0038	4.1	681
W7 (Heng Fa Chuen Salt Water Intake)	2003 Baseline (Scn 1)	6.08	34.00	0.10	0.0050	3.9	1046
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.10	34.00	0.10	0.0038	4.0	1205
	Ultimate Scenario – unmitigated (Scn 3a)	6.15	34.00	0.09	0.0038	4.1	2045
	Ultimate Scenario – mitigated (Scn 3b)	6.15	34.00	0.09	0.0038	4.1	2045
W8 (Siu Sai Wan Salt Water Intake)	2003 Baseline (Scn 1)	6.07	34.00	0.11	0.0066	4.1	11010
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.09	34.00	0.12	0.0054	4.2	8137
	Ultimate Scenario – unmitigated (Scn 3a)	6.15	34.00	0.11	0.0049	4.2	5588
W8	Ultimate Scenario – mitigated (Scn 3b)	6.15	34.00	0.11	0.0049	4.2	5588

Notes:

1. Bolded value represents non-compliances of WQO.

2. Data represent the mean model output predicted in the middle water layer where the intake points are located.

Table 5.26 Predicted Water Quality at Selected Cooling Water Intakes and Saltwater Intakes for Wet Season (Operational Phase)

Indicator Point (refer to Figure 5.2)	Scenario	DO (mg/L)	Salinity (ppt)	TIN (mg/L)	UIA (mg/L)	SS (mg/L)	E. coli (no./100mL)
WQO for WSD Saltwater Intake		> 2	-	-	-	<10	<20,000
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	2003 Baseline (Scn 1)	6.06	25.95	0.26	0.0043	4.9	610
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.87	25.62	0.30	0.0050	6.1	322
	Ultimate Development – unmitigated (Scn 3a)	5.92	25.76	0.29	0.0045	6.0	296
	Ultimate Development – mitigated (Scn 3b)	5.92	25.76	0.29	0.0045	6.0	296
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	2003 Baseline (Scn 1)	5.81	26.96	0.22	0.0037	4.8	578
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.43	27.16	0.24	0.0039	5.3	514
	Ultimate Scenario – unmitigated (Scn 3a)	5.34	27.25	0.24	0.0039	5.2	292
	Ultimate Scenario – mitigated (Scn 3b)	5.34	27.25	0.24	0.0039	5.2	292
W1 (Tseung Kwan O Salt Water Intake)	2003 Baseline (Scn 1)	6.85	27.05	0.19	0.0032	5.5	101
	Ultimate Scenario with no WCR & CBL (Scn 2)	7.03	27.14	0.23	0.0038	6.0	244
	Ultimate Scenario – unmitigated (Scn 3a)	7.16	27.15	0.20	0.0032	6.0	155
	Ultimate Scenario – mitigated (Scn 3b)	7.16	27.15	0.20	0.0032	6.0	155
W2 (Yau Tong Salt Water Intake)	2003 Baseline (Scn 1)	6.28	25.98	0.25	0.0038	5.0	374
	Ultimate Scenario with no WCR & CBL (Scn 2)	6.16	25.62	0.29	0.0043	6.0	167
	Ultimate Scenario – unmitigated (Scn 3a)	6.13	25.73	0.28	0.0041	6.0	185
	Ultimate Scenario – mitigated (Scn 3b)	6.13	25.73	0.28	0.0041	6.0	185
W3 (Cha Kwo Ling Salt Water Intake)	2003 Baseline (Scn 1)	5.87	26.28	0.26	0.0045	4.8	1193
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.64	26.04	0.29	0.0050	5.8	476
	Ultimate Scenario – unmitigated (Scn 3a)	5.67	26.07	0.29	0.0048	5.8	627
	Ultimate Scenario – mitigated (Scn 3b)	5.67	26.07	0.29	0.0048	5.8	627
W6 (Sai Wan Ho Salt Water Intake)	2003 Baseline (Scn 1)	5.66	26.29	0.27	0.0051	4.6	1551
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.45	26.27	0.28	0.0049	5.7	519
	Ultimate Scenario – unmitigated (Scn 3a)	5.43	26.38	0.28	0.0047	5.6	390
	Ultimate Scenario – mitigated (Scn 3b)	5.43	26.38	0.28	0.0047	5.6	390
W7 (Heng Fa Chuen Salt Water Intake)	2003 Baseline (Scn 1)	5.75	26.93	0.22	0.0039	4.7	907
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.37	27.13	0.24	0.0040	5.3	378
	Ultimate Scenario – unmitigated (Scn 3a)	5.33	27.25	0.24	0.0039	5.2	268
	Ultimate Scenario – mitigated (Scn 3b)	5.33	27.25	0.24	0.0039	5.2	268
W8 (Siu Sai Wan Salt Water Intake)	2003 Baseline (Scn 1)	5.93	26.94	0.22	0.0039	5.0	2508
	Ultimate Scenario with no WCR & CBL (Scn 2)	5.55	27.10	0.25	0.0045	5.6	2729
	Ultimate Scenario – unmitigated (Scn 3a)	5.50	27.18	0.25	0.0042	5.5	1820
	Ultimate Scenario – mitigated (Scn 3b)	5.50	27.18	0.25	0.0042	5.5	1820

Notes:

1. Bolded value represents non-compliances of WQO.

2. Data represent the mean model output predicted in the middle water layer where the intake points are located.

Water Quality Impacts on Corals

5.7.16 The predicted maximum daily sedimentation rates for the coral habitats in Junk Bay and Ngan Wan South, namely S1, S2 and S11 are presented in Table 5.23 and Table 5.24. The locations of these coral sites are shown in Figure 5.2.  All the predicted maximum values including those under Scenario 1 (baseline conditions), Scenario 2 (ultimate scenario with no WCR and CBL) and Scenario 3 (ultimate scenario) were all below 3.5 g/m²/day which are well below the assessment criterion of 100g/m²/day. 

5.7.17 As shown in Table 5.23 and Table 5.24, the predicted % increases of depth-averaged SS levels due to the implementation of the Project complied very well with the WQO that waste discharges shall not raise the ambient level by 30% at all selected sensitive receivers including S1, S2 and S11. The rest of the coral sites, namely S3 to S10, are far away from the Project site and smaller water quality impacts are expected. A more detailed assessment on the coral habitats is provided in Section 8.

Water Quality Impacts on Fish Culture Zones

5.7.18 The major water quality parameter of concern for fish culture zones (FCZ) would be the SS and DO levels.  The assessment criteria for SS and DO are that generally it should not exceed a maximum of 50mg/L and 5 mg/L respectively at FCZ.  The modelling results for Tung Lung Chau and Po Toi O FCZ, namely F1 and F2 (Figure 5.2), under mitigated ultimate development scenario (Scenario 3b) are summarized in Table 5.27. The results are presented for the surface water layer as the fish cages are normally kept in the surface water.

Table 5.27 Predicted Water Quality at Fish Culture Zones under Scenario 3b

Fish Culture Zone (FCZ)	Mean Surface SS (mg/L)	90% DO (Surface Layer) (mg/L)
Dry Season
F1 (Tung Lung Chau)	3.9	6.1
F2 (Po Toi O)	3.7	6.1
Wet Season
F1 (Tung Lung Chau)	4.8	5.4
F2 (Po Toi O)	3.9	5.4

5.7.19 The modelling results indicated that the mean surface SS levels at F1 and F2 are very low (below 5 mg/L) and would well comply with the limit of 50 mg/L.  The mean surface DO would also comply with the limit of 5 mg/L.  No adverse impacts would therefore be expected at the Tung Lung Chau and Po Toi O FCZ under the ultimate development scenario in terms of the predicted mean surface SS and DO levels.

Sedimentation Patterns

5.7.20 Simulation of the sedimentation conditions in Junk Bay was included as part of the water quality impact assessment. Appendix 5.5 and Appendix 5.7 include the contour plots for mean and maximum sedimentation fluxes (in unit of g/m²/d) for Scenario 2 (without CBL and WCR) and Scenario 3b (with CBL and WCR) in the dry and wet seasons. The mean sedimentation rates are the average values over a full spring-neap cycle of 15 days where as the maximum sedimentation rates are the peak values over the 15-day simulation period.

5.7.21 The shallow water regions in inner Junk Bay where the tidal current speed is slow are the areas with relatively higher sedimentation rates. The contour plots showed that relatively higher sediment deposition rates mainly occurred at the storm outlets and EDC near the TCS. As compared to the predicted wet season results, the predicted dry season sedimentation fluxes were comparatively higher in Junk Bay and Victoria Harbour. According to the sedimentation plots, it appeared to have a patch with high sedimentation rate close to shoreline of TCS during the dry season.

5.7.22 The plots also showed slight differences in sedimentation patterns near the TCS between Scenario 2 and Scenario 3b in both the dry and wet seasons. There would be some changes in velocity patterns mainly due to the WCR reclamation. As discussed in Section 5.7.1, the momentary and accumulated flow across the inner Junk Bay would also be slightly affected (Figures DH3, DH4, WH3 and WH4 in Appendix 5.3). The slight changes in flushing capacity and current speeds would slightly alter the hydrodynamic conditions in the Inner Junk Bay leading to the slight changes in sediment deposition.

5.7.23 The comparisons between Scenario 2 and Scenario 3b however showed that the overall sedimentation rates in Junk Bay and Victoria Harbour with WCR reclamation and CBL bridge in place would not be significantly different from the conditions without WCR and CBL.

Impact from Sewage Bypass during Operational Phase

5.7.24 Modelling was carried out for two scenarios to assess the potential constraint on the proposed beneficial use of EDC and Junk Bay during emergency sewage bypass as follows:

· Scenario 4a - continuous emergency bypass of raw sewage at the seawall for a period of 12 hours under ultimate scenario.

· Scenario 4b - continuous emergency bypass of raw sewage via the submarine outfall at Tathong channel for a period of 12 hours under ultimate scenario.

5.7.25 Figure 5.7 shows the locations of both seawall bypass and submarine outfall. For each of the two scenarios (4a and 4b), the emergency discharge was modelled for three different starting times, namely dry season neap tide, wet season spring tide and wet season neap tide respectively (also see Section 5.5.19).

5.7.26 The model results are presented as time series plots for E. coli covering the periods before, during and after the emergency discharges in Appendix 5.9 and Appendix 5.10 for Scenario 4a and Scenario 4b respectively. The indicator points selected for presentation include EDC, EPD monitoring stations (JM3 and JM4) and TKO saltwater intake (W1). Figure 5.2 shows these indicator points. The predicted results for ultimate scenario (Scenario 3b) are also included in these time series plots for comparison

5.7.27 It should be highlighted that the TKOPTW is an existing facility outside the scope of the Project. The Project would not result in any increase in the loading of TKOPTW as compared to the “without Project” situation. This assessment would only focus on the water quality constraints on the proposed water sport recreation at EDC and inner Junk Bay (Figure 5.1a) under emergency sewage bypass situations. This assessment is not intended to assess the sewage bypass impact related to other sensitive uses (such as saltwater intake). The TKO saltwater intake (W1) was selected in this assessment only as a reference assessment point within the proposed recreation zone.

5.7.28 During the emergency discharge period, it is likely that the water quality in the Junk Bay would be affected. As shown in Appendix 5.9 and Appendix 5.10, elevations of E.coli levels were observed immediately after the emergency discharge for most of the discharge scenarios. Table 5.28a summarizes the predicted peak E.coli values for various discharge scenarios and the time required to restore the baseline levels. Station JM4 is not located within the proposed water recreation zone and is included in Table 5.28a for reference.

Table 5.28a Summary of E.coli Impacts Due to Sewage Bypass

Scenario	Peak E.coli level (no./100mL)				Time required to restore the baseline level (days)
	EDC2	W1	JM3	JM4	EDC2	W1	JM3	JM4
Scenario 4a – Sewage Bypass at Seawall for 12 Hours
Dry season neap	No observable Impact	No observable Impact	319	352	NA	NA	2	2
Wet season spring	4089	100300	35670	657	2	2	2	2
Wet season neap	2007	72960	23600	267	2	2	2	2
Scenario 4b Sewage Bypass at Submarine Outfall for 12 Hours
Dry season neap	No observable Impact	No observable Impact	158	1392	NA	NA	2	2
Wet season spring	No observable Impact	No observable Impact	451	2561	NA	NA	2	2
Wet season neap	No observable Impact	No observable Impact	No observable Impact	425	NA	NA	NA	2

Emergency Sewage Bypass at Seawall for 12 Hours

5.7.29 The magnitude of impact is considered high for emergency bypass at seawall (Scenario 4a). The E. coli levels reached the peak value of 4089, 100300, 35670 and 657 no./100mL at EDC, JM3, JM4 and W1 respectively. The water quality conditions were predicted to recover within 2 days from the start of the emergency period. The model results for Scenario 4a represent the worst-condition of discharging the raw sewage at the seawall for 12 hours.

Emergency Sewage Bypass at Submarine Outfall for 12 Hours

5.7.30 Significantly less impact on the inner Junk Bay was predicted for the discharge of raw sewage at the submarine outfall (Scenario 4b) where the dispersion and dilution effect is better. The peak value predicted amongst EDC2, W1 and JM3 (i.e. stations within the proposed water recreation zone) was 451 no./100 mL which complied with the WQO of 610 no./100mL.

Planned Sewage Bypass at Submarine Outfall for 1 Hour

5.7.31 Based on the information provided by DSD, there would be planned discharge of effluent into the marine water for 1 hour each month via the submarine outfall. Based on the modelling results for the 12-hour emergency discharge at submarine outfall (Scenario 4b), it is not expected that the planned discharge for 1 hour would pose any water quality constraints on the recreational uses at EDC and inner Junk Bay.

5.7.32 It is recommended that no water recreational activities should be carried out during any sewage bypass at seawall until the baseline water quality condition is restored. Water quality monitoring should be conducted to confirm the suitability of water quality for water sports before re-opening of the EDC and Junk Bay.

5.7.33 The mean results over the 15-day simulation period for Scenario 4a and Scenario 4b at Stations EDC1, W1, JM3 and JM4 are tabulated in Tables 5.28b. Appendix 5.11 and Appendix 5.12 show the contour plots of mean results for Scenario 4a and Scenario 4b respectively. All the mean values predicted for Scenario 4a and Scenario 4b complied with the relevant WQO except only for the SS levels predicted at EDC1 for emergency discharge at dry season neap tide which breached the inland WQO. However, this SS exceedance was not caused by the emergency bypass as the same level of exceedance was also predicted for the ultimate scenario for dry season (Scenario 3b without any sewage bypass) (refer to Table 5.21).

Table 5.28b Predicted Water Quality During Emergency Bypass (Operational Phase)

Indicator Point (refer to Figure 5.2)		Scenario	Depth-averaged DO 10 percentile (mg/L)	Bottom DO 10 percentile (mg/L)	Depth-averaged TIN (mg/L)	Depth-averaged UIA (mg/L)	Depth-averaged SS (mg/L)	Depth-averaged E. coli (no./100mL)
WQO for inland water in Junk Bay WCZ			≥4	-	-	-	≤25 (Annual median)	≤1000
EDC1 (Eastern Channel – upstream)	Dry Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	4.65	4.66	4.44	0.150	42.7	375
		Emergency Bypass at Submarine Outfall (Scn 4b)	4.66	4.67	4.44	0.150	42.7	375
	Wet Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	9.82	8.50	1.78	0.034	22.0	252
		Emergency Bypass at Submarine Outfall (Scn 4b)	9.91	8.64	1.75	0.034	21.9	249
	Wet Season – Spring Tide	Emergency Bypass at Seawall (Scn 4a)	8.80	7.72	1.83	0.036	22.1	258
		Emergency Bypass at Submarine Outfall (Scn 4b)	9.14	8.09	1.80	0.036	22.0	252
EDC2 (Eastern Channel – downstream)	Dry Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	5.53	5.54	2.01	0.075	19.7	80
		Emergency Bypass at Submarine Outfall (Scn 4b)	5.55	5.54	2.00	0.074	19.7	80
	Wet Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	8.68	7.31	0.89	0.015	16.0	359
		Emergency Bypass at Submarine Outfall (Scn 4b)	8.74	7.33	0.86	0.014	15.9	343
	Wet Season – Spring Tide	Emergency Bypass at Seawall (Scn 4a)	7.86	6.84	0.91	0.016	16.1	371
		Emergency Bypass at Submarine Outfall (Scn 4b)	8.32	7.06	0.89	0.015	16.0	345
WQO for Junk Bay WCZ			≥4	≥2	≤0.3	≤0.021	-	≤610 **
JM3 (EPD Marine Water Quality Monitoring Station)	Dry Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	6.08	5.52	0.13	0.004	4.1	5
		Emergency Bypass at Submarine Outfall (Scn 4b)	6.08	5.80	0.12	0.004	4.1	5
	Wet Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	5.35	4.62	0.26	0.005	5.8	98
		Emergency Bypass at Submarine Outfall (Scn 4b)	5.37	4.64	0.23	0.004	5.7	75
	Wet Season – Spring Tide	Emergency Bypass at Seawall (Scn 4a)	5.35	4.60	0.25	0.005	5.7	100
		Emergency Bypass at Submarine Outfall (Scn 4b)	5.36	4.62	0.24	0.004	5.6	77
W1 (Tseung Kwan O Salt Water Intake	Dry Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	6.01	6.08	0.27	0.009	4.8	9
		Emergency Bypass at Submarine Outfall (Scn 4b)	6.08	6.08	0.26	0.009	4.8	9
	Wet Season – Neap Tide	Emergency Bypass at Seawall (Scn 4a)	6.03	6.32	0.26	0.005	6.1	210
		Emergency Bypass at Submarine Outfall (Scn 4b)	7.22	5.29	0.23	0.004	5.9	158
	Wet Season – Spring Tide	Emergency Bypass at Seawall (Scn 4a)	5.59	4.95	0.26	0.005	6.0	214
		Emergency Bypass at Submarine Outfall (Scn 4b)	5.90	5.25	0.23	0.004	5.9	161

** WQO for E.coli is applied for secondary contact recreation subzone and fish culture subzone only.

Notes:

1. Bolded value represents non-compliances of WQO.

Construction Phase Dredging and Filling Impacts – Unmitigated Scenarios

5.7.34 The impact of a sediment plume during the construction phase was modelled by simulating a 15-day construction period for both dry and wet seasons. Details of the modelling scenarios are given in Section 5.5.

5.7.35 The baseline depth-averaged and surface SS mean reading and 90 percentiles during the dry and wet seasons are summarised in Table 5.28c. These values are derived from the 2003 water quality field survey at JB1, JB2, JB3 and JB4 (Figure 5.3) located near the reclamation site. Based on the mean depth-averaged field data, the 30% allowable elevations of depth-averaged SS above the ambient will be 0.7 mg/L and 1.7 mg/L for dry and wet seasons, respectively. For bottom SS, the allowable elevations will be 1.1 mg/L and 1.9 mg/L for dry and wet seasons, respectively. For assessment of the impact on seawater intakes, the surface SS concentrations will be used as the ambient levels for comparison with the predicted SS elevations. For assessment of the impact on coral habitats, the maximum allowable elevations for bottom SS are used.

Table 5.28c Depth-averaged and Surface SS concentrations near the Reclamation Site

Stations (Figure 5.3)	Dry Season			Wet Season
JB1, JB2, JB3, JB4	Depth-averaged	Surface	Bottom	Depth-averaged	Surface	Bottom
Average SS (mg/L) in 2003	2.4	1.9	3.6	5.7	5.7	6.2
90 percentile (ambient level)	3.6	3	4.9	9.0	9.9	11
30% increase above the ambient level	0.7 **	N/A	1.1 **	1.7	N/A	1.9 **

** Calculated using the mean value.

5.7.36 For assessment on the coral impacts, the peak sedimentation rate predicted under the operational phase scenarios of 3.5 g/m²/day will be used as the ambient level.

5.7.37 Table 5.29 to Table 5.32 show the predicted mean pollutant elevations at selected sensitive receivers for unmitigated scenarios caused by the dredging and filling activities during Phase 1 seawall construction. The predicted mean SS values and mean sedimentation rates at all the selected sensitive receivers were below the relevant maximum allowable elevations as specified in the above sections. Non-compliance for SS and sedimentation rate was predicted at S1 during wet season for 8% and 4% of the time under the unmitigated scenario. Exceedance for SS was also predicted at S1 during dry season for 7% of the time. It is anticipated that the implementation of mitigation measures such as silt curtain around the construction activities will significantly reduce the dispersion of SS. Appendix 5.13a contains the time-series plots for Station S1 which shows the variations of SS and sedimentation elevations over a tidal cycle. Although SS and sedimentation exceedances were predicted at the coral site S1 (for <8% of the total time only) during the Phase I seawall construction, the peak SS elevations at S1 as shown in Appendix 5.13a were less than 5 mg/L under the unmitigated scenario. Appendix 5.13b shows the contour plots of average SS elevation over the simulation period. No unacceptable SS and sedimentation impact is therefore expected at the coral site provided that mitigation measures recommended in Section 5.8 are properly implemented. The predicted mean SS elevations at selected cooling water intakes and salt water intakes ranged from 0.008 to 0.12 mg/L which are considered low as compared to the mean and 90%ile surface ambient SS levels as tabulated in Table 5.28c. The peak SS elevations at the intakes were less than 0.7 mg/L under the unmitigated scenario. Appendix 5.13a contains the time-series plots showing the variation of SS elevations at water intakes C1, W3 and W6 during wet season. It is expected that the proposed dredging and filling works would not cause significant SS impacts on these water intakes.

Table 5.29 Predicted Water Quality at Selected Indicator Points for Dry Season (Construction Phase)

Indicator Point (refer to Figure 5.2)	Water Layer	Sedimentation elevation (g/m^2/day)		SS elevation due to dredging and filling (mg/L)		SS elevation due to dredging (mg/L)	Mean NH4N elevation (mg/L)	Mean TKN elevation (mg/L)	Mean TP elevation (mg/L)	Mean DO Depletion (mg/L)
		Mean Value	% time in compliance *	Mean Value	% time in compliance	Mean Value
S1 (Junk bay Coral Site-South West)	Bottom Layer	8.81	100	0.2916	93	0.2426	3.40E-06	1.26E-04	5.82E-05	4.37E-03
S2 (Junk bay Coral Site-Junk Island)	Bottom Layer	0.60	100	0.0144	100	0.0091	1.27E-07	4.73E-06	2.18E-06	1.64E-04
S11 (Ngan Wan South Coral Site)	Bottom Layer	0.44	100	0.0108	100	0.0027	3.78E-08	1.40E-06	6.48E-07	4.86E-05
T3 (San Ka Tsuen Typhoon Shelter)	Depth-average	13.94	100	0.3445	100	0.2674	3.74E-06	1.39E-04	6.42E-05	4.81E-03
T4 (Shau Kei Wan Typhoon Shelter)	Depth-average	1.46	100	0.0288	100	0.0185	2.59E-07	9.62E-06	4.44E-06	3.33E-04
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin)	Depth-average	0.03	100	0.0007	100	0.0004	5.60E-09	2.08E-07	9.60E-08	7.20E-06
EDC (Eastern Channel)	Depth-average	0.73	100	0.0144	100	0.0134	1.88E-07	6.97E-06	3.22E-06	2.41E-04
VM1 (EPD Station)	Depth-average	3.55	100	0.0849	100	0.0614	8.60E-07	3.19E-05	1.47E-05	1.11E-03
JM3 (EPD Station)	Depth-average	22.14	93	0.3461	87	0.2316	3.24E-06	1.20E-04	5.56E-05	4.17E-03
JM4 (EPD Station)	Depth-average	1.52	100	0.0320	100	0.0212	2.97E-07	1.10E-05	5.09E-06	3.82E-04
EM1 (EPD Station)	Depth-average	1.60	100	0.0371	100	0.0206	2.88E-07	1.07E-05	4.94E-06	3.71E-04
EM2 (EPD Station)	Depth-average	1.27	100	0.0275	100	0.0105	1.47E-07	5.46E-06	2.52E-06	1.89E-04

· The compliance rate was calculated using an ambient level of 3.5 g/m²/day which is the peak value predicted for the operational phase as shown in Table 5.23 and Table 5.24.

Table 5.30 Predicted Water Quality at Selected Indicator Points for Wet Season (Construction Phase)

Indicator Point (refer to Figure 5.2)	Water Layer	Sedimentation elevation (g/m^2/day)		SS elevation due to dredging and filling (mg/L)		SS elevation due to dredging (mg/L)	Mean NH4N elevation (mg/L)	Mean TKN elevation (mg/L)	Mean TP elevation (mg/L)	Mean DO Depletion (mg/L)
		Mean Value	% time in compliance *	Mean Value	% time in compliance	Mean Value
S1 (Junk bay Coral Site-South West)	Bottom Layer	24.59	96	0.6174	92	0.4715	6.60E-06	2.45E-04	1.13E-04	8.49E-03
S2 (Junk bay Coral Site-Junk Island)	Bottom Layer	1.53	100	0.0377	100	0.0227	3.18E-07	1.18E-05	5.45E-06	4.09E-04
S11 (Ngan Wan South Coral Site)	Bottom Layer	0.52	100	0.0128	100	0.0045	6.30E-08	2.34E-06	1.08E-06	8.10E-05
T3 (San Ka Tsuen Typhoon Shelter)	Depth-average	4.54	100	0.0383	100	0.0239	3.35E-07	1.24E-05	5.74E-06	4.30E-04
T4 (Shau Kei Wan Typhoon Shelter)	Depth-average	4.85	100	0.068	100	0.0356	4.98E-07	1.85E-05	8.54E-06	6.41E-04
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin)	Depth-average	0.57	100	0.0086	100	0.0048	6.72E-08	2.50E-06	1.15E-06	8.64E-05
EDC (Eastern Channel)	Depth-average	2.06	100	0.0143	100	0.0135	1.89E-07	7.02E-06	3.24E-06	2.43E-04
VM1 (EPD Station)	Depth-average	8.01	100	0.1889	100	0.1209	1.69E-06	6.29E-05	2.90E-05	2.18E-03
JM3 (EPD Station)	Depth-average	8.95	99.72	0.0944	100	0.0632	8.85E-07	3.29E-05	1.52E-05	1.14E-03
JM4 (EPD Station)	Depth-average	2.31	100	0.0633	100	0.0402	5.63E-07	2.09E-05	9.65E-06	7.24E-04
EM1 (EPD Station)	Depth-average	1.73	100	0.0509	100	0.0304	4.26E-07	1.58E-05	7.30E-06	5.47E-04
EM2 (EPD Station)	Depth-average	1.31	100	0.0319	100	0.0176	2.46E-07	9.15E-06	4.22E-06	3.17E-04

· The compliance rate was calculated using an ambient level of 3.5 g/m²/day which is the peak value predicted for the operational phase as shown in Table 5.23 and Table 5.24.

Table 5.31 Predicted Water Quality at Selected Cooling Water Intakes and Saltwater Intakes for Dry Season (Construction Phase)

Indicator Point (refer to Figure 5.2)	Water Layer	SS elevation due to dredging and filling (mg/L)	SS elevation due to dredging (mg/L)	Mean NH4N elevation (mg/L)	Mean TKN elevation (mg/L)	Mean TP elevation (mg/L)	Mean DO Depletion (mg/L)
		Mean Value	Mean Value
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	Middle Layer	0.0378	0.0296	4.14E-07	1.54E-05	7.10E-06	5.33E-04
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	Middle Layer	0.0150	0.0090	1.26E-07	4.68E-06	2.16E-06	1.62E-04
W1 (Tseung Kwan O Salt Water Intake)	Middle Layer	0.0356	0.0220	3.08E-07	1.14E-05	5.28E-06	3.96E-04
W2 (Yau Tong Salt Water Intake)	Middle Layer	0.0154	0.0120	1.68E-07	6.24E-06	2.88E-06	2.16E-04
W3 (Cha Kwo Ling Salt Water Intake)	Middle Layer	0.0627	0.0489	6.85E-07	2.54E-05	1.17E-05	8.80E-04
W6 (Sai Wan Ho Salt Water Intake)	Middle Layer	0.0416	0.0268	3.75E-07	1.39E-05	6.43E-06	4.82E-04
W7 (Heng Fa Chuen Salt Water Intake)	Middle Layer	0.0181	0.0107	1.50E-07	5.56E-06	2.57E-06	1.93E-04
W8 (Siu Sai Wan Salt Water Intake)	Middle Layer	0.0080	0.0045	6.30E-08	2.34E-06	1.08E-06	8.10E-05

Table 5.32 Predicted Water Quality at Selected Cooling Water Intakes and Saltwater Intakes for Wet Season (Construction Phase)

Indicator Point (refer to Figure 5.2)	Water Layer	SS elevation due to dredging and filling (mg/L)	SS elevation due to dredging (mg/L)	Mean NH4N elevation (mg/L)	Mean TKN elevation (mg/L)	Mean TP elevation (mg/L)	Mean DO Depletion (mg/L)
		Mean Value	Mean Value
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	Middle Layer	0.0448	0.025	3.50E-07	1.30E-05	6.00E-06	4.50E-04
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	Middle Layer	0.0464	0.027	3.78E-07	1.40E-05	6.48E-06	4.86E-04
W1 (Tseung Kwan O Salt Water Intake)	Middle Layer	0.0077	0.0049	6.86E-08	2.55E-06	1.18E-06	8.82E-05
W2 (Yau Tong Salt Water Intake)	Middle Layer	0.0216	0.0129	1.81E-07	6.71E-06	3.10E-06	2.32E-04
W3 (Cha Kwo Ling Salt Water Intake)	Middle Layer	0.1171	0.0762	1.07E-06	3.96E-05	1.83E-05	1.37E-03
W6 (Sai Wan Ho Salt Water Intake)	Middle Layer	0.0986	0.0561	7.85E-07	2.92E-05	1.35E-05	1.01E-03
W7 (Heng Fa Chuen Salt Water Intake)	Middle Layer	0.0713	0.0428	5.99E-07	2.23E-05	1.03E-05	7.70E-04
W8 (Siu Sai Wan Salt Water Intake)	Middle Layer	0.0146	0.0083	1.16E-07	4.32E-06	1.99E-06	1.49E-04

5.7.38 The predicted nutrient elevations shown in Table 5.29 to Table 5.32 are based on the maximum levels of ammoniacal nitrogen (NH₄-N), total kjeldahl nitrogen (TKN) and total phosphorus (TP) measured in the sediment collected at EPD Station JS2 in 2003, which were 14 mg/kg, 520 mg/kg and 240 mg/kg respectively, and the assumption that all the nutrients in the SS will be released into the water column. The ambient nutrient levels measured at EPD marine water monitoring stations JM3 and JM4 (Figure 5.2) in 2003 ranged from 0.01 to 0.14 mg/L, 0.12 to 0.3 mg/L and 0.02 to 0.04 mg/L for NH₄-N, TKN and TP respectively. With reference to Table 5.29 to Table 5.32, the predicted mean elevations for NH₄-N (ranged from 5.60x10^-9 to 6.60x10^-6 mg/L), TKN (ranged from 2.08x10^-7 to 2.45x10^-4 mg/L) and TP (ranged from 9.60x10^-8 to 1.13x10^-4 mg/L) are minimal as compared with the ambient levels measured at EPD’s stations. The impact from nutrient release is considered insignificant. It should be noted that organic nitrogen in TKN could undergo mineralization in marine water to produce NH₄-N and the prediction of NH₄-N increase above did not take into account the contribution of TKN released from dredging. However, even conservatively assuming all the TKN released from dredging would turn into NH₄-N, the resulted mean NH₄-N elevation would still be less than 0.0003 mg/L which is still considered insignificant.

5.7.39 The predicted DO depletions shown in Table 5.29 to Table 5.32 are based on the maximum level of chemical oxygen demand (COD) measured in the sediment collected at EPD Station JS2 in 2003, which was 18,000 mg/kg. It is assumed that all the COD in the suspended sediment would be consumed. It should be noted that this approach would likely overestimate the DO impact. The ambient depth-averaged and bottom DO levels measured at EPD marine water monitoring stations JM3 and JM4 (Figure 5.2) ranged from 3.2 to 8.1 mg/L whilst the predicted mean DO depletions in Table 5.29 to 5.32 ranged from 7.20x10^-6 to 8.49x10^-3 mg/L. Thus, the impact due to DO depletion is considered negligible.

5.7.40 Table 5.33 to Table 5.36 shows the predicted metal elevations at selected sensitive receivers for unmitigated scenarios caused by the dredging activities during Phase I seawall construction. The predicted metal elevations shown in Table 5.33 to Table 5.36 are based on the maximum levels of metal concentrations measured in the sediment collected at Stations VC7, VC9, VC8, VC10 and G2 (see Figure 11.1 for the locations) as shown in Table 5.18a, and the assumption that all the metals in the SS will be released into the water column. It can be seen from Table 5.33 to Table 5.36 that all the metal elevations are considered negligible as compared to the UK water quality standards.

Table 5.33 Predicted Metal Elevations at Selected Indicated Points for Dry Season (Construction Phase)

Indicator Point	Water Layer	SS elevation due to dredging (mg/L)	Cd	Cr	Cu	Ni	Pb	Zn	As	Hg	Ag
		Mean Value	µg/L
S1 (Junk bay Coral Site-South West)	Bottom Layer	0.2426	1.46E-04	7.28E-03	1.36E-02	2.43E-03	9.22E-03	3.15E-02	1.94E-03	4.85E-05	2.43E-04
S2 (Junk bay Coral Site-Junk Island)	Bottom Layer	0.0091	5.46E-06	2.73E-04	5.10E-04	9.10E-05	3.46E-04	1.18E-03	7.28E-05	1.82E-06	9.10E-06
S11 (Ngan Wan South Coral Site)	Bottom Layer	0.0027	1.62E-06	8.10E-05	1.51E-04	2.70E-05	1.03E-04	3.51E-04	2.16E-05	5.40E-07	2.70E-06
T3 (San Ka Tsuen Typhoon Shelter)	Depth-average	0.2674	1.60E-04	8.02E-03	1.50E-02	2.67E-03	1.02E-02	3.48E-02	2.14E-03	5.35E-05	2.67E-04
T4 (Shau Kei Wan Typhoon Shelter)	Depth-average	0.0185	1.11E-05	5.55E-04	1.04E-03	1.85E-04	7.03E-04	2.41E-03	1.48E-04	3.70E-06	1.85E-05
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin)	Depth-average	0.0004	2.40E-07	1.20E-05	2.24E-05	4.00E-06	1.52E-05	5.20E-05	3.20E-06	8.00E-08	4.00E-07
EDC (Eastern Channel)	Depth-average	0.0134	8.04E-06	4.02E-04	7.50E-04	1.34E-04	5.09E-04	1.74E-03	1.07E-04	2.68E-06	1.34E-05
VM1 (EPD Station)	Depth-average	0.0614	3.68E-05	1.84E-03	3.44E-03	6.14E-04	2.33E-03	7.98E-03	4.91E-04	1.23E-05	6.14E-05
JM3 (EPD Station)	Depth-average	0.2316	1.39E-04	6.95E-03	1.30E-02	2.32E-03	8.80E-03	3.01E-02	1.85E-03	4.63E-05	2.32E-04
JM4 (EPD Station)	Depth-average	0.0212	1.27E-05	6.36E-04	1.19E-03	2.12E-04	8.06E-04	2.76E-03	1.70E-04	4.24E-06	2.12E-05
EM1 (EPD Station)	Depth-average	0.0206	1.24E-05	6.18E-04	1.15E-03	2.06E-04	7.83E-04	2.68E-03	1.65E-04	4.12E-06	2.06E-05
EM2 (EPD Station)	Depth-average	0.0105	6.30E-06	3.15E-04	5.88E-04	1.05E-04	3.99E-04	1.37E-03	8.40E-05	2.10E-06	1.05E-05
UK Water Quality Standard (Refer to Section 5.5.39)			2.5	15	5	30	25	40	25	0.3	2.3

Table 5.34 Predicted Metal Elevations at Selected Indicated Points for Wet Season (Construction Phase)

Indicator Point	Water Layer	SS elevation due to dredging (mg/L)	Cd	Cr	Cu	Ni	Pb	Zn	As	Hg	Ag
		Mean Value	µg/L
S1 (Junk bay Coral Site-South West)	Bottom Layer	0.4715	2.83E-04	1.41E-02	2.64E-02	4.72E-03	1.79E-02	6.13E-02	3.77E-03	9.43E-05	4.72E-04
S2 (Junk bay Coral Site-Junk Island)	Bottom Layer	0.0227	1.36E-05	6.81E-04	1.27E-03	2.27E-04	8.63E-04	2.95E-03	1.82E-04	4.54E-06	2.27E-05
S11 (Ngan Wan South Coral Site)	Bottom Layer	0.0045	2.70E-06	1.35E-04	2.52E-04	4.50E-05	1.71E-04	5.85E-04	3.60E-05	9.00E-07	4.50E-06
T3 (San Ka Tsuen Typhoon Shelter)	Depth-average	0.0239	1.43E-05	7.17E-04	1.34E-03	2.39E-04	9.08E-04	3.11E-03	1.91E-04	4.78E-06	2.39E-05
T4 (Shau Kei Wan Typhoon Shelter)	Depth-average	0.0356	2.14E-05	1.07E-03	1.99E-03	3.56E-04	1.35E-03	4.63E-03	2.85E-04	7.12E-06	3.56E-05
T5 (Chai Wan Typhoon ShelterChai Wan Cargo Basin)	Depth-average	0.0048	2.88E-06	1.44E-04	2.69E-04	4.80E-05	1.82E-04	6.24E-04	3.84E-05	9.60E-07	4.80E-06
EDC (Eastern Channel)	Depth-average	0.0135	8.10E-06	4.05E-04	7.56E-04	1.35E-04	5.13E-04	1.76E-03	1.08E-04	2.70E-06	1.35E-05
VM1 (EPD Station)	Depth-average	0.1209	7.25E-05	3.63E-03	6.77E-03	1.21E-03	4.59E-03	1.57E-02	9.67E-04	2.42E-05	1.21E-04
JM3 (EPD Station)	Depth-average	0.0632	3.79E-05	1.90E-03	3.54E-03	6.32E-04	2.40E-03	8.22E-03	5.06E-04	1.26E-05	6.32E-05
JM4 (EPD Station)	Depth-average	0.0402	2.41E-05	1.21E-03	2.25E-03	4.02E-04	1.53E-03	5.23E-03	3.22E-04	8.04E-06	4.02E-05
EM1 (EPD Station)	Depth-average	0.0304	1.82E-05	9.12E-04	1.70E-03	3.04E-04	1.16E-03	3.95E-03	2.43E-04	6.08E-06	3.04E-05
EM2 (EPD Station)	Depth-average	0.0176	1.06E-05	5.28E-04	9.86E-04	1.76E-04	6.69E-04	2.29E-03	1.41E-04	3.52E-06	1.76E-05
UK Water Quality Standard (Refer to Section 5.5.39)			2.5	15	5	30	25	40	25	0.3	2.3

Table 5.35 Predicted Metal Elevations at Selected Cooling Water Intakes and Saltwater Intakes for Dry Season (Construction Phase)

Indicator Point	Water Layer	SS elevation due to dredging (mg/L)	Cd	Cr	Cu	Ni	Pb	Zn	As	Hg	Ag
		Mean Value	µg/L
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	Middle Layer	0.0296	1.78E-05	8.88E-04	1.66E-03	2.96E-04	1.12E-03	3.85E-03	2.37E-04	5.92E-06	2.96E-05
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	Middle Layer	0.0090	5.40E-06	2.70E-04	5.04E-04	9.00E-05	3.42E-04	1.17E-03	7.20E-05	1.80E-06	9.00E-06
W1 (Tseung Kwan O Salt Water Intake)	Middle Layer	0.0220	1.32E-05	6.60E-04	1.23E-03	2.20E-04	8.36E-04	2.86E-03	1.76E-04	4.40E-06	2.20E-05
W2 (Yau Tong Salt Water Intake)	Middle Layer	0.0120	7.20E-06	3.60E-04	6.72E-04	1.20E-04	4.56E-04	1.56E-03	9.60E-05	2.40E-06	1.20E-05
W3 (Cha Kwo Ling Salt Water Intake)	Middle Layer	0.0489	2.93E-05	1.47E-03	2.74E-03	4.89E-04	1.86E-03	6.36E-03	3.91E-04	9.78E-06	4.89E-05
W6 (Sai Wan Ho Salt Water Intake)	Middle Layer	0.0268	1.61E-05	8.04E-04	1.50E-03	2.68E-04	1.02E-03	3.48E-03	2.14E-04	5.36E-06	2.68E-05
W7 (Heng Fa Chuen Salt Water Intake)	Middle Layer	0.0107	6.42E-06	3.21E-04	5.99E-04	1.07E-04	4.07E-04	1.39E-03	8.56E-05	2.14E-06	1.07E-05
W8 (Siu Sai Wan Salt Water Intake)	Middle Layer	0.0045	2.70E-06	1.35E-04	2.52E-04	4.50E-05	1.71E-04	5.85E-04	3.60E-05	9.00E-07	4.50E-06
UK Water Quality Standard (Refer to Section 5.5.39)			2.5	15	5	30	25	40	25	0.3	2.3

Table 5.36 Predicted Metal Elevations at Selected Cooling Water Intakes and Saltwater Intakes for Wet Season (Construction Phase)

Indicator Point	Water Layer	SS elevation due to dredging (mg/L)	Cd	Cr	Cu	Ni	Pb	Zn	As	Hg	Ag
		Mean Value	µg/L
C1 (Dairy Farm Ice Plant Cooling Water Intakes)	Middle Layer	0.025	1.50E-05	7.50E-04	1.40E-03	2.50E-04	9.50E-04	3.25E-03	2.00E-04	5.00E-06	2.50E-05
C2 (Pamela Youde Nethersole Eastern Hospital Cooling Water Intake)	Middle Layer	0.027	1.62E-05	8.10E-04	1.51E-03	2.70E-04	1.03E-03	3.51E-03	2.16E-04	5.40E-06	2.70E-05
W1 (Tseung Kwan O Salt Water Intake)	Middle Layer	0.0049	2.94E-06	1.47E-04	2.74E-04	4.90E-05	1.86E-04	6.37E-04	3.92E-05	9.80E-07	4.90E-06
W2 (Yau Tong Salt Water Intake)	Middle Layer	0.0129	7.74E-06	3.87E-04	7.22E-04	1.29E-04	4.90E-04	1.68E-03	1.03E-04	2.58E-06	1.29E-05
W3 (Cha Kwo Ling Salt Water Intake)	Middle Layer	0.0762	4.57E-05	2.29E-03	4.27E-03	7.62E-04	2.90E-03	9.91E-03	6.10E-04	1.52E-05	7.62E-05
W6 (Sai Wan Ho Salt Water Intake)	Middle Layer	0.0561	3.37E-05	1.68E-03	3.14E-03	5.61E-04	2.13E-03	7.29E-03	4.49E-04	1.12E-05	5.61E-05
W7 (Heng Fa Chuen Salt Water Intake)	Middle Layer	0.0428	2.57E-05	1.28E-03	2.40E-03	4.28E-04	1.63E-03	5.56E-03	3.42E-04	8.56E-06	4.28E-05
W8 (Siu Sai Wan Salt Water Intake)	Middle Layer	0.0083	4.98E-06	2.49E-04	4.65E-04	8.30E-05	3.15E-04	1.08E-03	6.64E-05	1.66E-06	8.30E-06
UK Water Quality Standard (Refer to Section 5.5.39)			2.5	15	5	30	25	40	25	0.3	2.3

Construction Phase Impact from Deep Cement Mixing

5.7.41 DCM is considered to be the most suitable method of foundation improvement for the seawall foundations. The field trial should be conducted at a less exposed location behind the Phase 1 reclamation so as to minimize any potential water quality impact arising from the field trial. The scale of the field trial will be determined during the detailed design stage with consideration to meet the engineering requirements.

5.7.42 The preliminary contaminant analysis tests indicate that the mud is generally not contaminated (refer to Section 11), except at some isolated locations. At these isolated locations, treatment of the upper layers of marine mud may result in the release of potentially contaminated sediments into the water column.

5.7.43 Alkaline leachate can be caused by the use of cement stabilizer during the operation of DCM. Because the surrounding soils have inherent buffering ability, the alkaline leachate from the stabilized soils can be absorbed and neutralized. The degree of alkaline restraint of soils varies with the soil type, and the finer particle soil has greater alkaline restraint ability.

5.7.44 It is anticipated that the actual sediment loss caused by the DCM treatment would be in a much lesser extent as compared to the loss caused by conventional dredging and filling method. A major advantage of DCM is the capability to treat deep soils without excavation, shoring or dewatering, and thus there is less exposure of wastes to the surface environment.

5.7.45 Appendix 5.14 contains a paper on DCM method which concluded that the use of DCM would be a feasible method of ground treatment to improve the strength of the soft marine sediments for the WCR project, from both geotechnical and works (implementation) points of view. The paper also reviewed some water quality data collected from past DCM treatment projects which indicated that the DCM works caused no significant water quality impacts for various parameters including SS and pH. The environmental impact of DCM during seawall construction is considered to be minimal. Placement of a sand blanket on top of the mud prior to DCM treatment would reduce seabed sediment disturbance. No adverse impact from the potential sediment loss due to the proposed DCM treatment would be expected.

Construction Phase Impact During Consolidation of Reclamation

5.7.46 Use of vertical drains and surcharging is recommended to consolidate the undredged areas. During primary consolidation of reclamation, dissipation of excess pore water would occur due to the increasing pressure in the compressible soils. Installation of vertical drains allows the vertical movement of pore water, which would be drained to the ground surface. The vertical drains could be sand drains or prefabricated vertical band drains. Use of surcharge accelerates the consolidation process.

5.7.47 The outlets of vertical drains should be installed above the surface of the reclaimed land and be higher than the seawater level. Active pumping out of pore water is not to be used during consolidation of reclamation. Pore water released from vertical drains would spread on the interim ground surface. There would be no direct discharge of pore water into the nearby water body. The fill material would absorb the contaminants, if any.

5.7.48 Release of pore water during the consolidation process will be controlled to minimise the potential impacts to the surrounding environment. It is expected that the release rate would be low and the consolidation process would take several months to a year. The released pore water may contain contaminants and suspended solids. With suitable site arrangement and control facilities, the released pore water would be retained within the reclaimed land. It is unlikely that release of excess pore water would cause significant water quality impacts.

Impact from Land-based Construction Activities

General Construction Activities

5.7.49 The effects on water quality from general construction activities are likely to be minimal, provided that site drainage would be well maintained and good construction practices would be observed to ensure that litter, fuels, and solvents are managed, stored and handled properly.

5.7.50 Based on the Sewerage Manual, Part I, 1995 of the Drainage Services Department (DSD), the sewage production rate for construction workers is estimated to be 0.35 m³ per worker per day. For every 100 construction workers working simultaneously at the construction site, about 35 m³ of sewage would be generated per day. The sewage should not be allowed to discharge directly into the surrounding water body without treatment. Sufficient chemical toilets should be provided for workers.

Construction Runoff and Drainage

5.7.51 Construction run-off and drainage may cause local water quality impacts. Increase in SS arising from the construction site could block the drainage channels and may result in local flooding when heavy rainfall occurs. High concentrations of suspended degradable organic material in marine water could lead to a reduction in DO levels in the water column.

5.7.52 It is important that proper site practice and good site management be followed to prevent run-off with high level of SS from entering the surrounding waters. With the implementation of appropriate measures to control run-off and drainage from the construction site, disturbance of water bodies would be avoided and deterioration in water quality would be minimal. Thus, unacceptable impacts on the water quality are not expected, provided that the recommended measures described in Section 5.8 are properly implemented.

5.8 Mitigation of Adverse Environmental Impacts

5.8.1 This section specifies mitigation measures for water quality control. For specific ecological mitigation measures, please refer to Section 7 and Section 8 of this Report.

Operational Phase

Eastern Channel

5.8.2 The EDC and inner Junk Bay are proposed to be used for secondary contact recreation. To reduce the water quality impact on the EDC and inner Junk Bay under the ultimate development scenario, it is recommended to divert all storm discharges from Catchment M and 60% of the total discharges from Catchment L to the southern boundary of TCS (refer to Section 5.7.7).

Impact from Emergency Sewage Bypass

5.8.3 It is recommended to conduct water quality field survey at EDC after the proposed drainage diversion works (as mentioned in Section 5.7.6) is completed to confirm the suitability of the proposed recreation uses at EDC. The field survey should be conducted at a frequency of twice per year in dry season and wet season respectively after operation of the drainage diversion works. The suitability of the proposed recreation uses at EDC should be continuously reviewed with reference to the field survey data. After a 3-year operation period, a review should be conducted to determine whether the field survey programme should be discontinued. Details of the survey programme are given in a separate Environmental Monitoring & Audit (EM&A) Manual.

Impact from Emergency Sewage Bypass

5.8.4 In the very unlikely event of any sewage bypass occurring at the seawall, the proposed secondary contact recreation zone in EDC and Junk Bay should be closed. It is recommended that relevant government departments including EPD and LCSD shall be informed by DSD as soon as possible of any emergency bypass so that appropriate actions can be taken to prevent any water sports activities to be carried out in EDC and Junk Bay. The Plant operators should maintain good communications with various concerned parties. A list of address, email address, phone and fax number of key persons in relevant departments responsible for action should be made available to the plant operators. Water quality monitoring should be carried out by DSD and/or future operators of the proposed water recreation facilities to determine when conditions are suitable for re-opening of the EDC and Junk Bay for recreational purposes.

Reservoir Cleansing

5.8.5 All cleansing effluent generated from the proposed Pak Shing Kok high level fresh water service reservoir should be collected by a licensed waste collector for proper disposal and should not be discharged into the nearby water environment.

Sewage Pumping Station and Rising Mains

5.8.6 The emergency bypass location of the sewage pumping station for the recreational development at TKO landfill will be designed to be located 500 m away from the TKO saltwater intake. A standby pump will be provided to minimize the potential water quality impact from sewage overflow.

Handling of Site Drainage and Effluent

5.8.7 Connection of sewage generated from the administration building at the WCR toll plaza to the existing gravity sewer in TCS is considered not feasible (about 1km away). As the sewage quantity generated from the site (about 80 employed population) is small (about 5m³/d), sewage would be collected in holding tank and transferred by lorry to TKO Preliminary Treatment Works (PTW) for treatment. Transfer of sewage should be arranged within office hours of the TKO PTW to facilitate normal plant operators. The proposed sewage tankering away services should be provided on a regular basis to prevent any discharge of sewage to the nearby storm system. If the future operator of the administration building changes the sewage disposal scheme, using either a pumping scheme or a small treatment plant due to change of development parameter, the proposed holding tank could still be used to withhold the raw sewage in case of emergency. It is therefore not expected that there would be raw sewage discharges into the Junk Bay provided that the measures recommended above are properly implemented.

5.8.8 For handling, treatment and disposal of other operational stage effluent, the practices outlined in ProPECC PN 5/93 should be adopted where applicable. The following relevant recommendations should be followed:

· Drainage outlets provided in open areas and areas subjected to a substantial amount of wind-blown rain, including open carparks, balconies, podiums, yards, etc., should be connected to storm drains.

· Drainage outlets provided in covered areas, including covered podiums and other roofed areas, should be discharged to foul sewers.

· Subsoil drains of slopes, road embankments and earth retaining structures, and groundwater collection drains for basements, subways and tunnels, and similar drains, should under normal circumstances, be connected to storm water drains. Silt removal facilities should be provided where necessary. A separate drainage system that connects to foul sewers should be provided to collect wastewater from basements, subways and tunnels and similar areas.

· Drainage serving the proposed open lorry park should be connected to storm water drains via a petrol interceptor that would allow storm water bypass during peak flow periods.

· Drainage serving any covered carparks should be connected to foul sewers via petrol interceptors.

· To prevent hazards from sewage overflowing from the proposed pumping station for handling sewage arising from TKO landfill site, sewage pump sumps should be provided with a standby pump whose capacity should not be less than any of the duty pumps, and duty pumps should not be required to operate more than 10 on-off cycles per hour.

· Surface water drainage should be provided for discharging storm water off slopes and from open surfaces. Such drainage as normally collected in open surface channels should be led to storm water drains via silt removal facilities. Runoff in kerb gutters of roads or channels of building platforms should pass through a gully pit with necessary gratings to prevent objects from entering the storm water drains.

5.8.9 For maintenance of stormwater drainage system, reference should be made to Environment, Transport and Works Bureau (ETWB) Technical Circular (Works) No. 14/2004 “Maintenance of Stormwater Drainage Systems and Natural Watercourses” where applicable. The circular sets out the departmental responsibilities for the maintenance of stormwater drainage systems and natural watercourses in government and private lands. The circular is attached in Appendix 5.15.

Construction Phase

Dredging and Filling Activities

5.8.10 In view of the close vicinity of the coral community to the work site, silt curtain should be installed around the reclamation site.

5.8.11 Dredging and filling works should be carried out in a controlled manner such that release of sediments into the marine environment would be minimised. The following list of measures should be followed:

5.8.12 The modelling results indicated that the maximum permissible production rates of dredging activities should not exceed 1,400 m³/day for Phase 1 reclamation.

5.8.13 For filling activities for Phase 1 reclamation, no more than 12 dump cycles should be performed each day. The maximum volume of filling per dump cycle should not exceed 250 m³.

5.8.14 For backfilling using public fill, the maximum fine content of fills should not exceed 5%.

5.8.15 For each reclamation phase, core filing activities should be carried out after completion of the seawall of that particular phase.

5.8.16 Any gaps that may need to be provided for marine access should be shielded by silt curtains to control sediment plume dispersion away from the site. Filling activities for seawall construction should be carried out behind a silt curtain.

5.8.17 Closed-grab dredger should be used for dredging. Dredging activities should be carried out behind a silt curtain.

5.8.18 Properly maintained closed mechanical grabs should be used to minimise spillage and should be sealed tightly while being lifted.

5.8.19 All barges and hopper dredgers should be fitted with tight seals to their bottom opening to prevent leakage of materials.

5.8.20 The decks of all vessels should be kept tidy and free of oil or other substances that might be accidentally or otherwise washed overboard.

5.8.21 Loading of barges and hoppers should be controlled to prevent splashing of dredged materials to the surrounding environment and barges and hoppers should under no circumstances be filled to a level which would cause overflowing of material or sediment laden water during loading and transportation.

5.8.22 All barges and dredgers should maintain adequate clearance between vessels and the seabed at all states of the tide and should operate at a reduced speeds to ensure that undue turbidity is not generated by turbulence from vessel movement or propeller wash.

Deep Cement Mixing

5.8.23 To reduce any potential for water quality impact during the field trial of DCM, it is recommended to conduct the field trial after completion of the Phase 1 reclamation seawall so that the trial location can take place in a more sheltered location behind the Phase 1 reclamation seawall.

5.8.24 It is also recommended that silt curtains should be employed during both the DCM field trial and during full-scale DCM for seawall construction to minimize the potential for water quality impacts due to any unforeseen sediment release. A sand blanket should also be placed on top of the mud prior to DCM treatment to avoid seabed sediment disturbance. The sand fill layer is to be around 1 m deep covering the area of DCM treatment.

5.8.25 Because the cement slurry injection uses highly pressured air and liquids, there is a possibility that slurry waste could leach out to the water body. It is recommended that the cement slurry injection pressure should be carefully controlled to prevent leaching out of cement slurry and the slurry waste should be either properly disposed outside the site or used for back filling during reclamation after the slurry has solidified.

5.8.26 It is recommended to carry out water quality monitoring and audit during the DCM field trial. In-situ measurements of turbidity and pH should be measured at both upstream and downstream of the DCM field trial. If the measurements indicate that the field trial have caused significant changes in water quality conditions at the downstream station in terms of turbidity and pH, appropriate actions should be taken to stop the field trial and mitigation measures such as slowing down the DCM process, or rescheduling of works would be implemented to reduce the impacts. It is also recommended that water samples should be collected at selected water sensitive receivers during the field trial to confirm the water quality impact. More detailed water quality assessment and monitoring requirements for the DCM should be prepared based on the monitoring data of the field trial. All these should be summarized in a report to be submitted to EPD and AFCD for approval before starting the DCM operation.

Marine Piling Activities for CBL Construction

5.8.27 All wastewater generated from the piling activities should be collected by a derrick lighter or other collection system and be treated before controlled discharge. Spoil should be collected by sealed hopper barges for proper disposal.

5.8.28 In view of the close vicinity of the coral community to the work site, silt curtain should be installed around the marine piling activities to reduce the any impact due accidental release of excavated sediment.

Construction Site Runoff and General Construction Activities

5.8.29 To minimise the potential water quality impacts from construction site runoff and various construction activities, the practices outlined in ProPECC PN 1/94 Construction Site Drainage should be adopted.

Surface Run-off

5.8.30 Surface run-off from construction sites should be discharged into storm drains via adequately designed sand/silt removal facilities such as sand traps, silt traps and sedimentation basins. Channels or earth bunds or sand bag barriers should be provided on site to properly direct stormwater to such silt removal facilities. Perimeter channels at site boundaries should be provided where necessary to intercept storm run-off from outside the site so that it will not wash across the site. Catchpits and perimeter channels should be constructed in advance of site formation works and earthworks.

5.8.31 Silt removal facilities, channels and manholes should be maintained and the deposited silt and grit should be removed regularly, at the onset of and after each rainstorm to ensure that these facilities are functioning properly at all times. Any practical options for the diversion and re-alignment of drainage should comply with both engineering and environmental requirements in order to ensure adequate hydraulic capacity of all drains. Minimum distances of 100 m should be maintained between the discharge points of construction site runoff and the existing TKO saltwater intake.

5.8.32 There is a need to apply to EPD for a discharge licence for discharge of effluent from the construction site under the WPCO. The discharge quality must meet the requirements specified in the discharge licence. All the runoff and wastewater generated from the works areas should be treated so that it satisfies all the standards listed in the TM-DSS. Reuse and recycling of the treated effluent can minimise water consumption and reduce the effluent discharge volume. The beneficial uses of the treated effluent may include dust suppression, wheel washing and general cleaning. It is anticipated that only a small quantity of wastewater would be generated from the works areas.

5.8.33 Construction works should be programmed to minimize soil excavation works in rainy seasons (April to September). If excavation in soil could not be avoided in these months or at any time of year when rainstorms are likely, for the purpose of preventing soil erosion, temporary exposed slope surfaces should be covered e.g. by tarpaulin, and temporary access roads should be protected by crushed stone or gravel, as excavation proceeds. Intercepting channels should be provided (e.g. along the crest / edge of excavation) to prevent storm runoff from washing across exposed soil surfaces. Arrangements should always be in place to ensure that adequate surface protection measures can be safely carried out well before the arrival of a rainstorm.

5.8.34 Earthworks final surfaces should be well compacted and the subsequent permanent work or surface protection should be carried out immediately after the final surfaces are formed to prevent erosion caused by rainstorms. Appropriate drainage like intercepting channels should be provided where necessary.

5.8.35 Measures should be taken to minimize the ingress of rainwater into trenches. If excavation of trenches in wet seasons is necessary, they should be dug and backfilled in short sections. Rainwater pumped out from trenches or foundation excavations should be discharged into storm drains via silt removal facilities.

5.8.36 Open stockpiles of construction materials (e.g. aggregates, sand and fill material) on sites should be covered with tarpaulin or similar fabric during rainstorms. Measures should be taken to prevent the washing away of construction materials, soil, silt or debris into any drainage system.

5.8.37 Manholes (including newly constructed ones) should always be adequately covered and temporarily sealed so as to prevent silt, construction materials or debris from getting into the drainage system, and to prevent storm run-off from getting into foul sewers. Discharge of surface run-off into foul sewers must always be prevented in order not to unduly overload the foul sewerage system.

5.8.38 Good site practices should be adopted to remove rubbish and litter from construction sites so as to prevent the rubbish and litter from spreading from the site area. It is recommended to clean the construction sites on a regular basis.

Groundwater

5.8.39 Under normal circumstances, groundwater pumped out of wells, etc. for the lowering of ground water level in basement or foundation construction, and groundwater seepage pumped out of tunnels or caverns under construction should be discharged into storm drains after the removal of silt in silt removal facilities.

5.8.40 However, groundwater pumped out during construction of the northern cycle track footbridge and southern footbridge as well as the proposed sewage pumping station for TKO landfill development should not be discharged into the storm system as the groundwater may potentially be contaminated by leachate seepage from the TKO landfill. The pumped out groundwater should be temporarily held in storage tanks on site as the volume is anticipated to be small. It is recommended that the groundwater should be collected and tankered off site by a licensed wastewater collector for treatment and disposal at TKO PTW. The site investigation works at the detailed design stage of the Project should include groundwater sampling and analysis to determine the composition of groundwater. The monitoring results of groundwater quality should be submitted to EPD and DSD for their approval. Should the groundwater quality be found to exceed the TM standard for discharge into foul sewers, suitable treatment and disposal method of contaminated groundwater should be recommended. It is proposed that a packaged treatment unit be installed at the site should pre-treatment be required. All the required on-site pre-treatment of the collected groundwater should be implemented to the satisfaction of the EPD. Sampling should be conducted for the groundwater to ensure that the groundwater quality meets the TM-DSS prior to the discharge of groundwater to the TKO PTW. Estimate of the volume of groundwater should be made at the detailed design stage based on the site investigation data.

Boring and Drilling Water

5.8.41 Water used in ground boring and drilling for site investigation or rock / soil anchoring should as far as practicable be recirculated after sedimentation. When there is a need for final disposal, the wastewater should be discharged into storm drains via silt removal facilities.

Wastewater from Concrete Batching and Precast Concrete Casting

5.8.42 Wastewater generated from the washing down of mixing trucks and drum mixers and similar equipment should whenever practicable be recycled. The discharge of wastewater should be kept to a minimum.

5.8.43 To prevent pollution from wastewater overflow, the pump sump of any water recycling system should be provided with an on-line standby pump of adequate capacity and with automatic alternating devices.

5.8.44 Under normal circumstances, surplus wastewater may be discharged into foul sewers after treatment in silt removal and pH adjustment facilities (to within the pH range of 6 to 10). Disposal of wastewater into storm drains will require more elaborate treatment.

Wheel Washing Water

5.8.45 All vehicles and plant should be cleaned before they leave a construction site to ensure no earth, mud, debris and the like is deposited by them on roads. A wheel washing bay should be provided at every site exit if practicable and wash-water should have sand and silt settled out or removed before discharging into storm drains. The section of construction road between the wheel washing bay and the public road should be paved with backfall to reduce vehicle tracking of soil and to prevent site run-off from entering public road drains.

Bentonite Slurries

5.8.46 Bentonite slurries used in diaphragm wall and bore-pile construction should be reconditioned and reused wherever practicable. If the disposal of a certain residual quantity cannot be avoided, the used slurry may be disposed of at the marine spoil grounds subject to obtaining a marine dumping licence from EPD on a case-by-case basis.

5.8.47 If the used bentonite slurry is intended to be disposed of through the public drainage system, it should be treated to the respective effluent standards applicable to foul sewer, storm drains or the receiving waters as set out in the WPCO Technical Memorandum on Effluent Standards.

Water for Testing & Sterilization of Water Retaining Structures and Water Pipes

5.8.48 Water used in water testing to check leakage of structures and pipes should be reused for other purposes as far as practicable. Surplus unpolluted water could be discharged into storm drains.

5.8.49 Sterilization is commonly accomplished by chlorination. Specific advice from EPD should be sought during the design stage of the works with regard to the disposal of the sterilizing water. The sterilizing water should be reused wherever practicable.

Wastewater from Building Construction

5.8.50 Before commencing any demolition works, all sewer and drainage connections should be sealed to prevent building debris, soil, sand etc. from entering public sewers/drains.

5.8.51 Wastewater generated from building construction activities including concreting, plastering, internal decoration, cleaning of works and similar activities should not be discharged into the stormwater drainage system. If the wastewater is to be discharged into foul sewers, it should undergo the removal of settleable solids in a silt removal facility, and pH adjustment as necessary.

Acid Cleaning, Etching and Pickling Wastewater

5.8.52 Acidic wastewater generated from acid cleaning, etching, pickling and similar activities should be neutralized to within the pH range of 6 to 10 before discharging into foul sewers. If there is no public foul sewer in the vicinity, the neutralized wastewater should be tinkered off site for disposal into foul sewers or treated to a standard acceptable to storm drains and the receiving waters.

Wastewater from Site Facilities

5.8.53 Wastewater collected from canteen kitchens, including that from basins, sinks and floor drains, should be discharged into foul sewer via grease traps capable of providing at least 20 minutes retention during peak flow.

5.8.54 Drainage serving an open oil filling point should be connected to storm drains via a petrol interceptors with peak storm bypass.

5.8.55 Vehicle and plant servicing areas, vehicle wash bays and lubrication bays should as far as possible be located within roofed areas. The drainage in these covered areas should be connected to foul sewers via a petrol interceptor. Oil leakage or spillage should be contained and cleaned up immediately. Waste oil should be collected and stored for recycling or disposal in accordance with the Waste Disposal Ordinance.

Sewage from Workforce

5.8.56 The presence of construction workers generates sewage. It is recommended to provide sufficient chemical toilets in the works areas. The toilet facilities should be more than 30 m from any watercourse. A licensed waste collector should be deployed to clean the chemical toilets on a regular basis.

5.8.57 Notices should be posted at conspicuous locations to remind the workers not to discharge any sewage or wastewater into the nearby environment. Regular environmental audit on the construction site can provide an effective control of any malpractices and can encourage continual improvement of environmental performance on site. It is anticipated that sewage generation during the construction phase of the project would not cause water pollution problem after undertaking all required measures.

Accidental Spillage of Chemicals

5.8.58 Contractor must register as a chemical waste producer if chemical wastes would be produced from the construction activities. The Waste Disposal Ordinance (Cap 354) and its subsidiary regulations in particular the Waste Disposal (Chemical Waste) (General) Regulation should be observed and complied with for control of chemical wastes.

5.8.59 Any service shop and maintenance facilities should be located on hard standings within a bunded area, and sumps and oil interceptors should be provided. Maintenance of vehicles and equipment involving activities with potential for leakage and spillage should only be undertaken within the areas appropriately equipped to control these discharges.

5.8.60 Disposal of chemical wastes should be carried out in compliance with the Waste Disposal Ordinance. The Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes published under the Waste Disposal Ordinance details the requirements to deal with chemical wastes. General requirements are given as follows:

· Suitable containers should be used to hold the chemical wastes to avoid leakage or spillage during storage, handling and transport.

· Chemical waste containers should be suitably labelled, to notify and warn the personnel who are handling the wastes, to avoid accidents.

· Storage area should be selected at a safe location on site and adequate space should be allocated to the storage area.

Construction Works at Storm Culvert or in Close Proximity of Inland Water or Seafront

5.8.61 To minimize the potential water quality impacts from the construction works located at or near any river channels, natural streams or seafront, the practices outlined in ETWB TC (Works) No. 5/2005 “Protection of natural streams/rivers from adverse impacts arising from construction works” should be adopted where applicable. Relevant mitigation measures are listed below:

· The proposed works should preferably be carried out within the dry season where the flow in the storm culvert/river channel/stream is low.

· The use of less or smaller construction plants may be specified to reduce the disturbance to the riverbed.

· Temporary sewerage system should be designed to prevent wastewater from entering the river, streams and sea.

· Temporary storage of materials (e.g. equipment, filling materials, chemicals and fuel) and temporary stockpile of construction materials should be located well away from any water courses during carrying out of the construction works.

· Stockpiling of construction materials and dusty materials should be covered and located away from any water courses.

· Construction debris and spoil should be covered up and/or disposed of as soon as possible to avoid being washed into the nearby water receivers.

· Construction activities, which generate large amount of wastewater, should be carried out in a distance away from the waterfront, where practicable.

· Mitigation measures to control site runoff from entering the nearby water environment should be implemented to minimize water quality impacts. Surface channels should be provided along the edge of the waterfront within the work sites to intercept the runoff.

· Construction effluent, site run-off and sewage should be properly collected and/or treated.

· Any works site inside the storm water courses should be temporarily isolated, such as by placing of sandbags or silt curtains with lead edge at bottom and properly supported props to prevent adverse impact on the storm water quality.

· Silt curtain should be installed around the construction activities for the proposed landing steps at the seafront of TCS to minimize the potential impacts due to accidental spillage of excavated materials.

· Proper shoring may need to be erected in order to prevent soil/mud from slipping into the storm culvert/river/stream/sea.

· Supervisory staff should be assigned to station on site to closely supervise and monitor the works.

5.9 Evaluation of Residual Impacts

Operational Phase

5.9.1 Adverse water quality impact associated with normal operation of the Project is not expected. The model predicted that the Project would not cause any WQO exceedance. With the proposed drainage diversion as recommended in Sections 5.7.6 and 5.8.2, it was predicted that the water quality at EDC and Junk Bay would be suitable for secondary contact recreation under the ultimate condition with further development of TKO in 2016. No adverse residual water quality impacts would be expected during the operational phase of the Project.

5.9.2 The water quality impact on the proposed beneficial use of EDC and Junk Bay due to the emergency bypass at seawall is expected to be short-term. In the remote case that it occurs, the plant operators of TKO PTW should closely communicate with EPD and LCSD to ensure appropriate actions can be undertaken to advise the public against recreational uses of the EDC and Junk Bay. No insurmountable water quality impact on the proposed beneficial use is expected from these temporary discharges under emergency situation.

Construction Phase

5.9.3 The construction phase water quality impact would generally be temporary and localised during construction. No unacceptable residual water quality impacts would be expected during the construction phase of the Project, provided that all the recommended mitigation measures are properly implemented.

5.10 Environmental Monitoring and Audit

5.10.1 In any event of emergency sewage bypass at seawall, the proposed recreation zone in EDC and Junk Bay will be closed. Water quality monitoring is recommended to collect water quality information at EDC and Junk Bay before re-opening of the EDC and Junk Bay to ensure the suitability of water quality for water sports activities.

5.10.2 Monitoring of the discharge quality of effluent from land-based construction sites should be conducted. Marine water quality monitoring should also be carried out at selected stations before and during the proposed marine construction works. In addition, a water quality monitoring programme should be implemented during the field trial of DCM to confirm the water quality impact before the full-scale implementation of DCM for seawall construction.

5.10.3 A more detailed description of the water quality monitoring requirements is specified in Section 16.

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[1] Environmental Protection Department Agreement No. CE 42/2001 Environmental and Engineering Feasibility Assessment Studies Relation to the Way Forward of the Harbour Area Treatment Scheme Working Final Report.

^([2]) Pastorok, R.A. and Bilyard, G.R. (1985). “Effects of sewage pollution on coral-reef communities.” Marine Ecology Progress Series 21: 175-189.

^([3]) 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.

^([4]) References cited in BCL (1994) Marine Ecology of the Ninepin Islands including Peddicord R and McFarland V (1996) Effects of suspended dredged material on the commercial crab, Cancer magister. in PA Krenkel, J Harrison and JC Burdick (Eds) Dredging and its Environmental Effects. Proc. Speciality Conference. American Society of Engineers.

^([5]) City University of Hong Kong, Final Report, Agreement No. CE 62/98, Consultancy Study on Fisheries and marine Ecological Criteria for Impact Assessment, AFCD, July 2001.

^([6]) Civil Engineering and Development Department Agreement No. CE 87/2001 (CE) Further Development of Tseung Kwan O – Feasibility Study Junk Bay Model Calibration – Hydrodynamics and Water Quality.

^([7]) Planning Department Agreement No. CE48/97 Feasibility Study for Additional Cross-border Links Stage 2: Investigations on Environment, Ecology, Land Use Planning, Land Acquisition, Economic/Financial Viability and Preliminary Project Feasibility/Preliminary Design Final Water Quality Impact Assessment Working Paper WP2 Volume 1 1999.

^([8]) Civil Engineering and Development Department Agreement No. CE 87/2001 (CE) Further Development of Tseung Kwan O – Feasibility Study Pollution Loading Inventory Report.

^([9]) Civil Engineering and Development Department Agreement No. CE 74/98, Wan Chai Development Phase II Comprehensive Feasibility Study, Environmental Impact Assessment Report.

^([10]) Civil Engineering and Development Department Agreement No. CE 32/99, Comprehensive Feasibility Study for the Revised Scheme of South East Kowloon Development, Technical Note on Flow and Load Inventory.

^([11]) Environmental Protection Department Agreement No. CE 42/2001 Environmental and Engineering Feasibility Assessment Studies Relation to the Way Forward of the Harbour Area Treatment Scheme Working Final Report.

⁽¹²⁾ The same assessment criteria were also adopted in the approved EIA for Agreement No. CE 74/98 Wan Chai Development Phase II Comprehensive Feasibility Study.