[Client]

9.1.1.1 This section presents the assessment on water quality impact arising from the construction and operation of the Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities (HKBCF) and the Hong Kong Link Road (HKLR).

9.1.1.2 Modelling tools have been used to predict the hydrodynamic and water quality conditions before, during and after implementation of the above-mentioned proposed Projects. Modelling results are compared with the relevant water quality objectives and criteria to check for compliance. Mitigation measures are then proposed to mitigate the impacts to safeguard the aquatic environment in the potentially affected areas. This section also includes assessment of the potential cumulative water quality impacts taking account of other concurrent projects.

9.2 Description of the Project

HKBCF

9.2.1.1 HKBCF will involve approx. 130 ha of reclamation. As discussed in Section 4, two options are formulated as regards the construction sequence of the reclamation works for HKBCF. The reclamation layouts of these two options are shown in Figures 4.6 and 4.7 in Section 4; they are referred to as Sequence A and Sequence B.

9.2.1.2 A comparison of the key aspects of Sequence A and Sequence B is given in Section 4. As explained therein, Sequence B should be adopted as it is environmentally more advantageous and as it can still just meet the vital programme target. However, for such a complicated project as HKBCF, there is a possibility that the need to change to Sequence A may occur; for instance, in case of unforeseen delay in the earlier tasks, a change from Sequence B to Sequence A will enable the project to gain back time to compensate for earlier delay. In view of the above, though the planning of HKBCF should be based on Sequence B, it is also necessary to consider Sequence A in the assessment of water quality impacts as the worse scenario.

9.2.1.3 The reclamation layout and envisaged construction programme of HKBCF based on Sequence B are shown in Figures 9A2-1 and 9A2-2 in Appendix 9A2. In general, it is envisaged that the seawall at the peripheral of HKBCF site would be carried out first and the reclamation would start when substantial length of seawall is constructed to protect the reclamation filling. Temporary steel sheet pile wall would be installed near the northern edge of HKBCF site so as to protect silt curtain against current. A detailed description and drawings showing the reclamation sequence is attached in Appendix 9A2.

9.2.1.4 The reclamation layout and envisaged construction programme of HKBCF based on Sequence A are shown in Figures 9A1-1 and 9A1-2 in Appendix 9A1. When compared to Sequence B, Sequence A adopts a series of interim/temporary seawalls around the proposed locations of Passengers Clearance Building (PCB) and the Government Buildings so as to minimise the extent of reclamation to enable early completion of Phase 1 of HKBCF. It is envisaged that the reclamation works would start at Portion A of HKBCF Phase 1 first. In order to minimise the impact to the water quality, Portion A of HKBCF Phase 1 would be enclosed by a temporary seawall with a gap of about 100m for marine access before the reclamation filling. Upon completion of reclamation filling in Portion A of HKBCF Phase 1, substantial length of seawalls would have been completed in Portions B and C of HKBCF Phase 1. Then the reclamation would be carried out in the sequence of Portion B, Portion C, Portion D of HKBCF Phase 1 and finally HKBCF Phase 2. A detailed description and drawings showing the reclamation sequence is attached in Appendix 9A1.

9.2.1.5 The estimated volume of dredging and filling for Sequence A and Sequence B is summarised in Table 9.1.

Table 9.1 Estimated volume of dredging and filling in HKBCF

Option	Bulk Volume of Marine Deposit to be Dredged (million m³) ^{[1] [2]}	Bulk volume of filling (million m³) ^{[1], [3]}
Sequence A	29.90	52.0
Sequence B	18.70	40.8

Notes:

1) A bulk factor of 1.3 is applied to the insitu volume.

2) The volume of dredging includes dredging to form the pits for Mf sediment and excavation of sediment in bored pile excavation after the land is reclaimed.

3) The filling includes sandfill and public fill (excluding rockfill) for seawalls and reclamation.

9.2.1.6 As shown in Table 9.1 above, Sequence A would involve more dredging and more reclamation filling due to the need of interim/temporary seawalls and adoption of fully dredge method at some critical areas of HKBCF reclamation. In addition, Sequence A aims for a shorter construction time to complete Phase 1 of HKBCF by End 2014, whilst Sequence B would allow longer construction time to complete Phase 1 of HKBCF by End 2015. Therefore, the dredging and filling works in Sequence A are more intensive than those in Sequence B, thus entailing larger water quality impacts. Based on the overall programme and sediment loss rates for Sequence A and Sequence B, a comparison of the sediment loss rate between these two reclamation sequences is attached in Appendix 9B. The comparison shows that sediment loss rate of Sequence B is substantially less than that in Sequence A. Therefore, it is more conservative to adopt Sequence A than Sequence B in assessing the water quality impacts.

9.2.1.7 In view of the above, the assessment of water quality in this Chapter will be based on Sequence A for conservatism. In order to demonstrate that Sequence B will perform better than Sequence A from the water quality perspective, additional modeling of the worse construction scenario of Sequence B has been carried out and a comparison of the water quality impacts due to Sequence A and Sequence B will be presented in the relevant Sections below.

HKLR

9.2.1.8 The layout and envisaged construction programme/sequence of HKLR including its marine substructures and its reclamation work are shown in Figures 9C1 to 3 in Appendix 9C. Based on the available site investigation results, the estimated quantity of dredging and filling for HKLR is about 5.5 Mm³ (bulk volume) and 7.0 Mm³ (bulk volume) respectively.

9.2.1.9 The reclamation layout and sequence of HKLR are shown in Appendix 9C. In general, it is anticipated that the reclamation work of HKLR would be carried out in three portions. The general reclamation is as follows:

· Construct the seawall at Portion 1 (i.e. the southern portion of relcamation site) – A gap of about 100m will be allowed at the seawall for marine access during reclamation works. The portion of seawall at this gap would be completed after the reclmation filling;

· Dredging and filling for the reclamation in Portion 1;

· Dredging and filling for the reclamation and seawalls in Portion 2 (i.e. the portion at the middle of reclamation site). As the reclamation in Portion 2 is small, it is envisaged that the dredging and filling works for reclamation and seawall would be carried out at the same time;

· Dredging and filling for the reclamation and seawalls in Portion 3 (i.e. the northern portion of reclamation site). Similar to the case in Portion 2, the dredging and filling works for reclamation and seawall would be carried out at the same time.

9.2.1.10 As the construction of HKLR and HKBCF will be carried out independently in different works contracts, the construction programme/sequence of HKLR is not affected by the adoption of Sequence A or Sequence B of HKBCF reclamation. To assess the water quality impacts due to concurrent projects, Sequence A of HKBCF reclamation is assumed in the water quality model for conservatism as discussed in Section 9.2.1.7 above.

9.3 Environmental Legislation, Standards and Criteria

9.3.1 Environmental Impact Assessment Ordinance (Cap. 499)

9.3.1.1 Both the HKBCF and HKLR are Designated Projects under Schedule 2 of the EIAO. Under Section 16 of the Ordinance, the Environmental Protection Department (EPD) issued the Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO) which specifies the assessment methods and criteria for the EIA. Annexes 6 and 14 of the TM-EIAO stipulate the “Criteria for Evaluating Water Pollution” and “Guidelines for the Assessment of Water Pollution” respectively.

9.3.2 Water Pollution Control Ordinance (Cap. 358)

9.3.2.1 The Water Pollution Control Ordinance (WPCO) is the principal legislation governing the marine water quality in Hong Kong. Under the provision of the WPCO, Hong Kong’s waters have been divided into a series of Water Control Zones (WCZs). Water Quality Objectives (WQOs) have been declared to protect the specific beneficial uses and conservation goals of each of the zones. The proposed projects of HKBCF and HKLR are situated within the North- western Water Control Zone (WCZ), which is identified with the following beneficial uses:

· Source of food for human consumption;

· Commercial fisheries resource;

· Habitat for marine organisms generally;

· Recreational bathing beach;

· Secondary contact recreation including diving, sailing and windsurfing;

· Domestic and industrial supply;

· Navigation and shipping;

· Aesthetic enjoyment.

9.3.2.2 The relevant Water Quality Objectives (WQOs) applicable to the North Western WCZ are summarised in Table 9.2.

Table 9.2 WQOs of North Western WCZ

Water Quality Objectives
Aesthetic Appearance
· There should be no objectionable odours or discolouration of the water; · Tarry residues, floating wood, articles made of glass, plastic, rubber or any other substances should be absent; · Mineral oil should not be visible on the surface; · There should be no recognisable sewage derived debris; and · Floating, submerged and semi-submerged objects of a size likely to interfere with the free movement of vessels, or cause damage to vessels, should be absent.
Bacteria
· The levels of E coli should not exceed 180 counts per 100 ml at bathing beaches, calculated as the geometric mean of all samples collected from March to October inclusive. Samples have to be taken at least 3 times a month at intervals of between 3 and 14 days; · The levels of E coli should not exceed 610 counts per 100 ml at secondary contact recreation sub-zones, calculated as the geometric annual mean; and · Waste discharges shall not cause a risk to any beneficial use of the aquatic environment.
Dissolved Oxygen
· The depth averaged concentration of dissolved oxygen should not fall below 4 mg/l for 90% of the sampling occasions during the whole year; and · The concentration of dissolved oxygen should not be less than 2 mg/l within 2m of the seabed for 90% of the sampling occasions during the whole year.
pH
· The pH of the water should be within the range 6.5-8.5 units; and · Human activity should not cause the natural pH range to be extended by more than 0.2 units.
Temperature
· Waste discharges shall not cause the natural daily temperature range to change by more than 2.0°C.
Salinity
· Waste Discharges shall not cause the natural ambient salinity to change by more than 10%.
Suspended Solids
· Human activity should neither cause the natural ambient level to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.
Ammonia
· The un-ionised ammoniacal nitrogen level should not be more than 0.021 mg/l calculated as the annual average (arithmetic mean).
Nutrients
· Nutrients should not be present in quantities sufficient to cause excessive or nuisance growth of algae or other aquatic plants; and
· Without limiting the generality of the above point, the level of inorganic nitrogen should not exceed 0.5 mg/l, or 0.3 mg/l within Castle Peak sub-zone, expressed as the annual water column average.
Toxins
· Waste discharges shall not cause the toxins in water to attain such a level as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or other aquatic organisms, with due regard to biologically cumulative effects in food chains and to interactions of toxic substances with each other.

9.3.3 Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems

9.3.3.1 Discharges of effluents are subject to control under the WPCO. The Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters sets limits for effluent discharges. Specific limits apply for different areas and are different between surface waters and sewers. The limits vary with the rate of effluent flow. Standards for effluent discharged into the inshore waters and marine waters of North-western WCZ are summarized in Tables 9.3a and 9.3b.

Table 9.3a Standards for Effluents Discharged into the Inshore Waters of North Western Control Zones

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

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

Table 9.3b Standards for Effluents Discharged into the Marine Waters of North Western Control Zones

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

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

9.3.4 Practice Note for Professional Persons on Construction Site Drainage

9.3.4.1 The Practice Note for Professional Persons on Construction Site Drainage (ProPECC Note PN1/94) provides guidelines for the handling and disposal of construction discharges. This note is applicable for control of site runoff and wastewater generated during the construction phase of the HKBCF and HKLR. The types of discharges from construction sites outlined in the ProPECC Note PN1/94 that are relevant would include:

· Surface run-off;

· Boring and drilling water;

· Wastewater from concrete batching and precast concrete casting;

· Wheel washing water; and

· Wastewater from construction activities and site facilities.

9.4 Description of Existing Environment

9.4.1 Background

9.4.1.1 The North-western waters are situated at the mouth of the Pearl River Estuary and as such are heavily influenced by the massive freshwater flows from the hinterland. The area shows a distinct seasonality as a result of the seasonal influx of freshwater from the Pearl River. The estuarine influence is especially pronounced in the wet summer months when the freshwater flows are greatest and a strong salinity and temperature stratification are evident. During winter months, water conditions are more typical marine and the salinity and other parameters vary less with depth. Ebb tide currents are towards the southeast where the flood tide currents move to the northwest. Current velocities in areas near to the project area have been predicted in previous studies to be less than 2.0 m/s on the surface and rarely exceeding 0.25 m/s near seabed (ERM, 1997, 2005)

9.4.1.2 Water temperature ranges between about 15°C and 30°C over an annual cycle with a mean of about 22-23°C. Salinity typically varies within the range 10-32ppt.

9.4.1.3 The Pearl River carries very heavy loads of suspended sediment and nitrates and as a consequence concentrations of these parameters within North-western waters are variable but generally far higher than in the more oceanic influenced waters to the south and east of Hong Kong.

9.4.2 Pollution Sources

9.4.2.1 The North Western WCZ contains several significant sewage outfalls (Pillar Point, Northwest New Territories and Siu Ho Wan) and cooling water discharges from a number of users including Castle Peak Power Station, Hong Kong International Airport (HKIA) and Shiu Wing Steelworks.

9.4.2.2 In the past, dredging of marine mud and sand extraction has been extensive in the North-western Waters coastal area for reclamation projects including the land to be occupied by the Permanent Aviation Fuel Facility site (PAFF) at Tuen Mun Area 38, River Trade Terminal, Tin Shui Wai New Town and Hong Kong International Airport platform at Chek Lap Kok. Mud dredging to construct and maintain the navigation channel in Urmston Road and the berthing area at Castle Peak Power Station is periodic and on-going and the present temporary Aviation Fuel Receiving Facility (AFRF) at Sha Chau required the construction of a navigation channel and berthing area, which is, also, subject to maintenance dredging. The recently constructed Tonggu Channel just outside the HKSAR boundary will also require periodic maintenance dredging. To date, no adverse environmental impacts have been reported for any of these previous dredging exercises.

9.4.2.3 Disposal of contaminated dredged material, which began in 1992, is also on-going at the Contaminated Mud Pits (CMP) at East of Sha Chau. The capacity of the existing pits were predicted to be exhausted by early 2009 and two potential sites for future CMPs near the HKIA have been identified (Figures 9.4 and 9.5) and the EIA for the tentative sites have been approved by the Director of Environmental Protection (DEP). Disposal of Category M material that passes biological screening/uncontaminated dredged material continues intermittently at the North Brothers which has a remaining capacity of about 5 Mm³. The operation of the open sea disposal ground at North Lantau Borrow pit has been suspended since 2000 and there is currently no schedule for the reopening of the facility.

9.4.2.4 Commercial trawling is undertaken over much of the North-western waters and the Urmston Road is a very busy shipping channel for river trade vessels, high speed ferries, large coal vessels servicing Castle Peak Power Station and the existing temporary Aviation Fuel Receiving Facility delivery vessels.

9.4.2.5 The locations of the principal areas of seabed disturbance and the major sewage outfalls in the study area are indicated in Figure 9.4.

9.4.3 Sensitive Receivers

9.4.3.1 There are a number of important water sensitive receivers (WSRs) within the study area as shown in Figure 9.5. These include areas of ecological sensitivity and conservation importance, commercial fishing resources, areas of direct human contact, e.g. bathing beaches, and various points where seawater is abstracted for domestic, commercial or industrial purposes.

9.4.3.2 The Indo-Pacific humpback dolphin (Sousa chinensis) is frequently observed within the study area and in and around Sha Chau and Lung Kwu Chau Marine Park, with the areas close to the Brothers Islands being shown to be a recent key site for the dolphins (see Section 10). The North-western waters of Hong Kong actually represent the eastern range of the Pearl River Estuary dolphin population which extends far into the mainland Chinese waters.

9.4.3.3 Not Used.

9.4.3.4 Other features of conservation concern in the wider study area include the mangrove stands and seagrasses (Zostera japonica, Halophilia ovata and Halopila beccarii) at Tai Ho and along the Tung Chung Channel south of the HKIA at Sha Lo Wan and San Tau. This area also provides the preferred habitat for horseshoe crab (Tachypleus tridentatus and Carcinoscorpius rotundicauda) which have been also observed near the beaches of Lung Kwu Tan, Lung Kwu Chau, the Brothers, San Tau and Tai Ho Wan. Previous surveys near Sha Chau have identified the presence of the stone coral Faviidea as well as gorgonians and sea pens which are of ecological interest.

9.4.3.5 The study area contains two ungazetted bathing beaches at Lung Kwu Tan as well as a number of gazetted bathing beaches in Tuen Mun and along Castle Peak Road. The Butterfly Beach is the nearest to the study area, which is located about 1 km to the east of the proposed northern landing in Tuen Mun. Further east towards Castle Peak Road are the Castle Peak Beach, Kadoorie Beach, Cafeteria Old and New Beaches and Golden Beach. These beaches have historically suffered from high sewage derived bacterial loads. However, as a result of recent pollution enforcement activities and sewerage infrastructure improvements, the water quality at all the gazetted beaches in the North West WCZ is now deemed ‘fair’ according to the EPD’s criteria and suitable for bathing.

9.4.3.6 As part of the mitigation for the temporary aviation fuel line at Sha Chau, artificial reefs have been deployed in the Sha Chau and Lung Kwu Chau Marine Park. These reefs are designed to enhance fisheries resources and promote feeding opportunities for the Chinese White Dolphins which frequent the area. In addition, the Hong Kong Jockey Club, with the support from the AAHK, financed a project to deploy artificial reefs in the Chek Lap Kok Marine Exclusion Zone off the north eastern corner of the HKIA.

9.4.3.7 There are a number of major seawater intakes in the study area serving Tung Chung new town, the HKIA and industrial users, particularly the Castle Peak Power Station and Shiu Wing Steelworks immediately to the west of Tuen Mun Area 38. For the Castle Peak Power Station intake, there is a specific requirement that suspended sediment concentrations in water must be maintained below a level of 150 mg/l within a 5 km radius of the intake.

9.4.3.8 Based upon the above, a series of specific points and sensitive receivers for inclusion in the water quality modelling have been defined. These are shown in Figure 9.5 and detailed in Table 9.5 below.

Table 9.5 Observation Points and Water Sensitive Receivers for Water Quality Modelling

Code	Description	Impact
WSR 7	Black Point Cooling Water Intake	Operation
WSR 8	Lung Kwu Sheung Tan (non-gazetted beach)	Construction
WSR 9a	Urmston Road (Main Channel)	Construction and Operation
WSR 10	Sha Chau and Lung Kwu Chau Marine Park	Construction and Operation
WSR 11	Castle Peak Power Station Cooling Water Intake	Construction
WSR 12	Butterfly Beach	Construction and Operation
WSR 13	WSD Seawater Intake at Tuen Mun	Construction
WSR 15	Gazetted Beaches at Tuen Mun	Construction
WSR 18	Gazetted beaches along Castle Peak Road	Construction
WSR 19	Gazetted beaches at Ma Wan	Construction
WSR 20	Ma Wan Fish Culture Zone	Construction and Operation
WSR 21	Proposed Ta Pang Po Intake (Pumping Station)	Construction
WSR 22a	Tai Ho Wan Inlet (inside)	Construction
WSR 22b	Tai Ho Bay (inner), Near Tai Ho Stream SSSI	Construction and Operation
WSR 22c	Tai Ho Wan Inlet (outside)	Construction and Operation
WSR 23	Future seawater intake for LLP	Operation
WSR 24	Future seawater intake point for Tung Chung	Operation
WSR 25	Cooling water intake at HK International Airport	Construction and Operation
WSR 26	HKBCF South	Operation
WSR 27	San Tau Beach SSSI	Construction and Operation
WSR 28	Cooling water intake at HK International Airport	Construction and Operation
WSR 29	Hau Hok Wan (Horseshoe Crab Habitat)	Construction and Operation
WSR 30	Sha Lo Wan (Horseshoe Crab Habitat)	Construction and Operation
WSR 31	Sham Wat Wan (Mangrove and Horseshoe Crab Habitat)	Construction
WSR 32	Tai O (Mangrove Habitat)	Construction and Operation
WSR 34	Yi O (Mangrove and Horseshoe Crab Habitat)	Construction and Operation
WSR 40	Cheung Sha Wan Fish Culture Zone	Operation
WSR 41	Artificial Reef at NE Airport	Construction and Operation
WSR 42	Artificial Reef at Sha Chau	Construction
WSR 43	Future seawater intake for Tung Chung	Operation
WSR 44	Future HKBCF Intake	Operation
WSR 45c	Sham Shui Kok	Construction
WSR 46	Tai Mo To deep water channel	Construction
WSR 47a	River Trade Terminal	Construction
WSR 47b	River Trade Terminal	Construction
WSR 48	Airport Channel western end	Construction
WSR 49	Tai Mo To (Dolphin Habitat)	Construction and Operation
WSR 50	Potential embayed area for HKBCF	Operation

9.4.4 Baseline Water Quality

9.4.4.1 The existing water quality in the North Western waters have been monitored for many years as part of the EPD’s routine monitoring programme. The water quality is monitored monthly at six stations within the North-western WCZ as shown in Figure 9.5. A summary of the EPD’s Routine Water Quality Data for the North-western WCZ (2006 and 2007) is given in Tables 9.6a and 9.6b below.

Table 9.6a Summary of EPD’s Routine Water Quality Data for North Western WCZ (2006 – 2007)

Parameters	Monitoring Station
Temperature (°C)	23.7 (17.6 – 27.4)	23.0 (17.2 – 27.8)	23.8 (17.5 – 27.6)	23.4 (17.3 – 28.4)	23.7 (17.7 – 27.6)	23.2 (17.3 – 28.2)
Salinity (ppt)	29.6 (22.2 – 33.1	30.9 (26.1 – 33.1)	28.6 (19.0 – 33.1)	29.5 (18.8 – 33.1)	29.4 (23.7 – 33.1)	30.1 (24.9 – 33.1)
Dissolved Oxygen (mg/L)	6.3 (4.4 – 8.0)	5.7 (3.5 – 9.2)	6.5 (4.9 – 8.4)	6.0 (3.3 – 9.7)	6.3 (4.4 – 8.3)	5.8 (3.2 – 9.6)
BOD5 (mg/L)	0.6 (0.4 – 1.1)	1.0 (0.4 – 1.9)	0.6 (0.2 – 1.0)	1.0 (0.4 – 2.5)	0.7 (0.4 – 1.2)	1.1 (0.5 – 2.5)
SS (mg/L)	7.4 (2.5 – 17.4)	8.2 (2.3 – 14.7)	6.4 (2.9 – 21.3)	5.8 (1.8 – 9.3)	8.1 (3.0 – 14.0)	7.4 (3.9 – 11.7)
TIN (mg/L)	0.43 (0.17 – 0.75)	0.39 (0.09 – 0.70)	0.49 (0.18 – 0.85)	0.48 (0.09 – 1.05)	0.50 (0.22 – 0.80)	0.47 (0.13 – 0.87)
NH3 – N (mg/L)	0.005 (<0.001 – 0.010)	0.005 (0.001 – 0.007)	0.005 (0.001 – 0.011)	0.006 (0.001 – 0.010)	0.005 (0.001 – 0.011)	0.006 (0.001 – 0.012)
Chlorophyll-a (mg/L)	3.6 (0.8 – 19.2)	5.4 (0.7 – 17.7)	2.8 (0.8 – 10.6)	6 (0.7 – 20.7)	3.3 (1.0 – 7.7)	5.9 (1.0 – 22.0)
E. coli (cfu/100mL)	1100 (340 – 2600)	670 (56 – 3100)	470 (280 – 1900)	360 (49 – 1900)	500 (140 – 2100)	430 (45 – 2400)

Parameters

Monitoring Station

NM1

NM2

NM3

2006

2007

2006

2007

2006

2007

Temperature (°C)

23.7

(17.6 – 27.4)

23.0

(17.2 – 27.8)

23.8

(17.5 – 27.6)

23.4

(17.3 – 28.4)

23.7

(17.7 – 27.6)

23.2

(17.3 – 28.2)

Salinity (ppt)

29.6

(22.2 – 33.1

30.9

(26.1 – 33.1)

28.6

(19.0 – 33.1)

29.5

(18.8 – 33.1)

29.4

(23.7 – 33.1)

30.1

(24.9 – 33.1)

Dissolved Oxygen (mg/L)

6.3

(4.4 – 8.0)

5.7

(3.5 – 9.2)

6.5

(4.9 – 8.4)

6.0

(3.3 – 9.7)

6.3

(4.4 – 8.3)

5.8

(3.2 – 9.6)

BOD5 (mg/L)

0.6

(0.4 – 1.1)

1.0

(0.4 – 1.9)

0.6

(0.2 – 1.0)

1.0

(0.4 – 2.5)

0.7

(0.4 – 1.2)

1.1

(0.5 – 2.5)

SS (mg/L)

7.4

(2.5 – 17.4)

8.2

(2.3 – 14.7)

6.4

(2.9 – 21.3)

5.8

(1.8 – 9.3)

8.1

(3.0 – 14.0)

7.4

(3.9 – 11.7)

TIN (mg/L)

0.43

(0.17 – 0.75)

0.39

(0.09 – 0.70)

0.49

(0.18 – 0.85)

0.48

(0.09 – 1.05)

0.50

(0.22 – 0.80)

0.47

(0.13 – 0.87)

NH3 – N (mg/L)

0.005

(<0.001 – 0.010)

0.005

(0.001 – 0.007)

0.005

(0.001 – 0.011)

0.006

(0.001 – 0.010)

0.005

(0.001 – 0.011)

0.006

(0.001 – 0.012)

Chlorophyll-a (mg/L)

3.6

(0.8 – 19.2)

5.4

(0.7 – 17.7)

2.8

(0.8 – 10.6)

(0.7 – 20.7)

3.3

(1.0 – 7.7)

5.9

(1.0 – 22.0)

E. coli (cfu/100mL)

1100

(340 – 2600)

670

(56 – 3100)

470

(280 – 1900)

360

(49 – 1900)

500

(140 – 2100)

430

(45 – 2400)

Notes:

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

[2] Data in brackets indicate ranges

[3] Underlined indicates occurrence of non-compliance with that parameter of WQO

Table 9.6b Summary of EPD’s Routine Water Quality Data for North Western WCZ (2006 – 2007)

Parameters	Monitoring Station
Temperature (°C)	24.0 (17.9 – 27.8)	23.4 (17.3 – 28.3)	24.0 (17.7 – 29.2)	23.8 (17.3 – 30.3)	23.8 (17.5 – 28.3)	23.6 (17.1 – 30.6)
Salinity (ppt)	27.2 (16.4 – 32.8)	28.6 (23.0 – 33.0)	26.0 (10.5 – 33.3)	27.5 (12.0 – 33.0)	27.6 (11.9 – 33.4)	28.9 (9.7 – 33.5)
Dissolved Oxygen (mg/L)	6.3 (4.3 – 8.2)	5.7 (3.0 – 9.3)	6.7 (4.8 – 8.7)	6.4 (3.2 – 10.0)	6.8 (4.8 – 8.2)	6.8 (3.7 – 9.8)
BOD5 (mg/L)	0.7 (0.5 – 0.9)	1.1 (0.5 – 2.7)	0.7 (0.3 – 1.3)	1.1 (0.5 – 2.7)	0.7 (0.3 – 1.9)	1.1 (0.4 – 2.1)
SS (mg/L)	15.7 (3.8 – 53.8)	11.1 (4.3 – 18.7)	12.6 (4.1 – 35.9)	10.0 (3.5 – 27.7)	15.8 (2.7 – 56.7)	11.6 (3.5 – 27.7)
TIN (mg/L)	0.67 (0.29 – 1.07)	0.64 (0.22 – 1.06)	0.66 (0.09 – 1.40)	0.58 (0.12 – 1.40)	0.44 (0.06 – 1.20)	0.44 (0.07 – 1.48)
NH3 – N (mg/L)	0.008 (0.03 – 0.017)	0.008 (0.001 – 0.014)	0.006 (0.002 – 0.022)	0.006 (0.001 – 0.012)	0.004 (0.001 – 0.019)	0.004 (<0.001 – 0.009)
Chlorophyll-a (mg/L)	4.2 (1.3 – 17.4)	5.5 (1.3 – 23.0)	3.9 (1.1 – 12.0)	7.4 (1.2 – 26.3)	3.5 (1.3 -14.7)	8.3 (0.8–20.7)
E. coli (cfu/100mL)	900 (220 – 2600)	1300 (160- 3600)	64 (2 – 1900)	46 (2 – 2400)	5 (1 – 420)	12 (1 – 240)

Parameters

Monitoring Station

NM5

NM6

NM8

2006

2007

2006

2007

2006

2007

Temperature (°C)

24.0

(17.9 – 27.8)

23.4

(17.3 – 28.3)

24.0

(17.7 – 29.2)

23.8

(17.3 – 30.3)

23.8

(17.5 – 28.3)

23.6

(17.1 – 30.6)

Salinity (ppt)

27.2

(16.4 – 32.8)

28.6

(23.0 – 33.0)

26.0

(10.5 – 33.3)

27.5

(12.0 – 33.0)

27.6

(11.9 – 33.4)

28.9

(9.7 – 33.5)

Dissolved Oxygen (mg/L)

6.3

(4.3 – 8.2)

5.7

(3.0 – 9.3)

6.7

(4.8 – 8.7)

6.4

(3.2 – 10.0)

6.8

(4.8 – 8.2)

6.8

(3.7 – 9.8)

BOD5 (mg/L)

0.7

(0.5 – 0.9)

1.1

(0.5 – 2.7)

0.7

(0.3 – 1.3)

1.1

(0.5 – 2.7)

0.7

(0.3 – 1.9)

1.1

(0.4 – 2.1)

SS (mg/L)

15.7

(3.8 – 53.8)

11.1

(4.3 – 18.7)

12.6

(4.1 – 35.9)

10.0

(3.5 – 27.7)

15.8

(2.7 – 56.7)

11.6

(3.5 – 27.7)

TIN (mg/L)

0.67

(0.29 – 1.07)

0.64

(0.22 – 1.06)

0.66

(0.09 – 1.40)

0.58

(0.12 – 1.40)

0.44

(0.06 – 1.20)

0.44

(0.07 – 1.48)

NH3 – N (mg/L)

0.008

(0.03 – 0.017)

0.008

(0.001 – 0.014)

0.006

(0.002 – 0.022)

0.006

(0.001 – 0.012)

0.004

(0.001 – 0.019)

0.004

(<0.001 – 0.009)

Chlorophyll-a (mg/L)

4.2

(1.3 – 17.4)

5.5

(1.3 – 23.0)

3.9

(1.1 – 12.0)

7.4

(1.2 – 26.3)

3.5

(1.3 -14.7)

8.3

(0.8–20.7)

E. coli (cfu/100mL)

900

(220 – 2600)

1300

(160- 3600)

(2 – 1900)

(2 – 2400)

(1 – 420)

(1 – 240)

Notes:

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

[2] Data in brackets indicate ranges

[3] Underlined indicates occurrence of non-compliance with that parameter of WQO

9.4.4.2 Some temporal and spatial variability is evident in this dataset, but compliance is usually observed with the key WQOs for unionised ammonia notwithstanding generally eutrophic conditions resulting from the heavy nutrient load carried by the Pearl River. Compliance with the total inorganic nitrogen objective was remained the same during 2006 and 2007. In general, the water quality parameters recorded in 2007 were largely stable compared with 2006.

9.4.4.3 A drop in the compliance with the dissolved oxygen objective was noted. EPD suggested that the drop was related to the general occurrence of low DO starting June 2007 in Marine Water Quality in Hong Kong 2007.

9.4.4.4 Of particular relevance to this assessment, the EPD data for these two years indicate that suspended solid concentrations demonstrated a drop for all stations from 2006 to 2007. Suspended solid concentrations typically lie in the range of 2.5 to 57 mg/l with the highest recorded value being 56.7 mg/l at the Chek Lap Kok West station NM8 in 2006 while that the range drops to of 1.8 to 28 mg/l with the highest recorded value being 27.7 mg/l at the Chek Lap Kok North and West stations NM6 and NM8 in 2007.

9.4.4.5 Compliance with the WQO for dissolved oxygen was not achieved at NM1, NM3 and NM5. Occasional drops in depth average measurements below the compliance value of 4 mg/l was also observed at all monitoring stations. Oxygen super-saturation is, also, observed, particularly at the south-western station NM8, again indicated that eutrophication predominantly influenced by the Pearl River discharge.

9.4.4.6 In addition to EPD’s long term programme, comprehensive water quality data sets have been obtained from various construction related environmental monitoring programmes, the most significant ongoing programme being that for the management of the Contaminated Mud Pits at East of Sha Chau. These data are essentially comparable with the longer-term EPD dataset and show general compliance with the WQOs in the region of the mud dumping operations. Data obtained to date from this programme support the hypothesis that the disposal activities have not had any significant adverse effect on water quality beyond the pit areas during dumping. Suspended sediment concentrations are again observed to range from less than 10 mg/L to over 80 mg/L although mean values tend to be a bit higher than reported by EPD. Over the period 1994 to 1997, for example, annual mean depth averaged suspended sediment concentrations ranged from about 18 to 40 mg/L illustrating the considerable variability for this parameter. Depth averaged dissolved oxygen at East Sha Chau varies within the range from 4 to 10 mg/L with a mean value of about 6.7 mg/L.

9.4.4.7 The AAHK has also conducted a serious of non-statutory water quality monitoring for the periods 1999-2000, 2002-2003 and 2005-2006 and the average concentrations of suspended sediment recorded at mid-depth was 11.3 mg/L and the values ranged between 3 to 40 mg/l (Meinhardt, 2006b). The concentrations of dissolved oxygen recorded mid-depth ranged between 2.9 to 15.8 mg/L with an average of 7.0 mg/L.

9.4.4.8 The statutory WQO for suspended sediments is not defined in absolute numerical terms but instead is worded to require that human activities should not result in an elevation of more than 30% above ambient levels (Table 9.2). This in part reflects the difficulty in trying to apply a single numerical value for environmental management purposes in the context of the naturally highly variable characteristics of Hong Kong’s marine waters. Previous workers assessing the environmental impacts associated with the temporary AFRF at Sha Chau adopted a value of up to 34 mg/L to represent ambient suspended solid concentrations in essentially the same study area as is being considered in this assessment.

9.4.4.9 However, for the purposes of this assessment, the WQO for suspended solids at each sensitive receiver will be based on an analysis of the EPD routine monitoring data from 1998 to 2007 at the nearest EPD monitoring station, as described in Section 9.5 below.

9.4.5 Baseline Sediment Quality

9.4.5.1 There is a wealth of sediment quality data for the study area, from EPD’s routine monitoring, previous project surveys and, also, from project specific investigation undertaken for the projects of HKBCF, HKLR and HKBCF. Details of the findings from the various sources are presented in the sections below.

EPD Routine Sediment Quality Monitoring

9.4.5.2 Some existing sediment quality data from EPD sediment monitoring station in the North Western WCZ are available within the study area, which are monitored by the EPD every six months at four stations: NS2, NS3, NS4 and NS6 as shown in Figure 9.5. NS5 is not included in this evaluation as it is located in Tuen Mun Typhoon Shelter which is not relevant to this evaluation. The locations of the EPD stations are as follows:

· NS2 is located to the north of Siu Mo To at ~2.5km east of the preferred alignment;

· NS3 is located in the waters off the tip of River Trade Terminal in Tuen Mun and is about 500m from the proposed north reclamation landing at Tuen Mun;

· NS4 is located between Lung Kwu Chau and Lung Kwu Tan; and

· NS6 is near the western end of the airport runway. As both are far (>5km) from the Project site, they are not considered relevant to this project.

9.4.5.3 The monitoring results of NS2, NS3 in 2003-2007 are summarised in Tables 9.7a and 9.7b, with reference to the ETWB TC(W) 34/2002 criteria, as well as nitrogen and phosphorus nutrient contents.

Table 9.7a EPD’s Sediment Quality Monitoring Data for NS2 and NS3 within North Western Waters (2003-2007)

Contaminants¹	Unit	NS2²	NS3²	LCEL	UCEL
Arsenic	mg/kg dry wt	7.2 – 14	8.3 – 14	12	42
Cadmium	mg/kg dry wt	<0.1 – 0.1	<0.1 – 0.1	1.5	4
Chromium	mg/kg dry wt	24 – 43	20 – 42	80	160
Copper	mg/kg dry wt	28 – 42	18 – 48	65	110
Mercury	mg/kg dry wt	0.07 – 0.13	0.06 – 0.15	0.5	1
Nickel	mg/kg dry wt	15 – 27	11 – 24	40	40
Lead	mg/kg dry wt	31 – 50	27 – 45	75	110
Silver	mg/kg dry wt	0 – 1	0 – <1	1	2
Zinc	mg/kg dry wt	77 – 130	62 – 120	200	270
Low Molecular Weight PAH³	mg/kg dry wt	14 – 67	18 – 64.5	550	3,160
High Molecular Weight PAH³	mg/kg dry wt	35.5 – 123.5	38 – 113.5	1,700	9,600
Total PCBs	mg/kg dry wt	18 – 18	18 – 18	23	180
Particle Size Fraction <63mm	%	35 – 63	23 – 87	--	--
Total Kjeldahl Nitrogen (TKN)	mg/kg dry wt	120 – 520	120 – 440	--	--
Ammonia Nitrogen	mg/kg dry wt	0.12 – 8.2	<0.05 – 16	--	--
Total Phosphorus	mg/kg dry wt	84 – 290	86 – 250	--	--

¹ Based on bulk samples;

² The presented results are in range (min-max) and values exceeding the LCELs are shown in underlined; and

³ Mostly below analytical reporting limits and numeric values shown are calculated from the available components with <RL substituted with ½RL.

Table 9.7b EPD’s Sediment Quality Monitoring Data for NS4 and NS6 within North Western Waters (2003-2007)

Contaminants¹	Unit	NS4²	NS6²	LCEL	UCEL
Arsenic	mg/kg dry wt	9.1 – 11	7.1 – 16	12	42
Cadmium	mg/kg dry wt	<0.1 – 0.1	<0.1 - 0.1	1.5	4
Chromium	mg/kg dry wt	26 – 36	18 – 37	80	160
Copper	mg/kg dry wt	18 – 42	8 – 27	65	110
Mercury	mg/kg dry wt	0.06 – 0.23	<0.05– 0.1	0.5	1
Nickel	mg/kg dry wt	16 – 22	10 – 24	40	40
Lead	mg/kg dry wt	29 – 46	20 – 46	75	110
Silver	mg/kg dry wt	<1 – 0	<1 – 0	1	2
Zinc	mg/kg dry wt	99 – 110	42 – 100	200	270
Low Molecular Weight PAH³	mg/kg dry wt	90 – 99	90 – 94	550	3,160
High Molecular Weight PAH³	mg/kg dry wt	35 – 120	16 – 49	1,700	9,600
Total PCBs	mg/kg dry wt	18 – 18	18 – 18	23	180
Particle Size Fraction <63mm	%	12 – 61	10 – 81	--	--
Total Kjeldahl Nitrogen (TKN)	mg/kg dry wt	160 – 350	130 – 400	--	--
Ammonia Nitrogen	mg/kg dry wt	0.19 – 30	0.05 – 13	--	--
Total Phosphorus	mg/kg dry wt	92 – 230	100 – 260	--	--

¹ Based on bulk samples;

² The presented results are in range (min-max) and values exceeding the LCELs are shown in underlined; and

³ Mostly below analytical reporting limits and numeric values shown are calculated from the available components with <RL substituted with ½RL.

9.4.5.4 It is observed that of all parameters except arsenic are lower than the LCELs. Only the upper range arsenic concentrations were observed to exceed the LCEL. Based on the EPD’s Marine Water Quality in Hong Kong 2000, the arsenic concentrations might be due to the high natural arsenic levels in the soil of some areas of the northern New Territories (e.g. Lok Ma Chau, Ngau Tam Mei and Pat Heung) which could have been transported to the marine environment through river discharges and storm runoff.

9.4.5.5 There were 6 occasions over the past 5 years have EPD detected arsenic concentrations in the North-western waters marine sediment above the UCEL criterion adopted to define a level above which adverse biological toxicological effects would be expected. Given that the arsenic concentrations in this region are likely to represent the result of gradual natural erosive processes over geologic timescales, it seems reasonable to assume that the existing ecosystem is tolerant to the widespread presence of this element.

East Sha Chau Contaminated Mud Disposal Pit

9.4.5.6 In addition to the EPD’s routine monitoring programme, comprehensive water quality data sets have been obtained from various environmental monitoring programmes, with the most significant on-going one being that for the management of Contaminated Mud Pits at East of Sha Chau. Figure 9.6 shows the locations of the monitoring stations used. These data are essentially comparable to the EPD’s routine monitoring dataset and show a general compliance with WQOs in the area near the mud dumping operations. Data obtained to date support the hypothesis that disposal activities have not had any significant adverse effects on the water quality beyond the immediate confines of the mud pit areas during dumping. Suspended sediment concentrations are observed to range from <10 mg/l to >80 mg/l, although mean values tend to be higher than those reported by the EPD. For examples, over the period of 1994-1997, the annual mean depth averaged suspended sediment concentrations ranged ~18-40 mg/l, illustrating the variability of this parameter. The depth averaged dissolved oxygen concentration at East Sha Chau varies within the range of 4-10 mg/l, with a mean value of ~6.7 mg/l.

Hong Kong Section of HZMB and Connection with North Lantau Highway (EIA in 2004)

9.4.5.7 A review of previous environmental marine ground investigation (GI) of the airport east conducted in 2004 has been conducted under the HyD’s Agreement No. CE26/2003 (HY) Hong Kong Section of Hong Kong-Zhuhai-Macao Bridge and Connection with North Lantau Highway – Investigation. Vibrocores and grab samples were collected at 23 locations and surface grab samples were collected at another 18 locations along the proposed route alignment of the Hong Kong Section of the HZMB in the western waters to the airport island, within the airport channel, and in northern waters of Tung Chung as shown in Figure 9.7. Elutriate testing of the surface grab samples was also carried out.

9.4.5.8 Sediment samples were tested for the suite of metals, metalloids and organic pollutants (PAHs, PCBs and TBT) as specified in the ETWB TC(W) No.34/2002. Chlorinated pesticides (11 components: a-BHC, b- & g-BHC, d-BHC, aldrin, endosulfan 1, endosulfan sulfate, heptachlor, heptachlor-epoxide, p,p’-DDE, p,p’-DDD, p,p’-DDT) were also tested for the 0-1m (surface) sub-samples. In addition to these parameters, elutriate testing of sediment samples was also conducted for nitrogen (ammonia, nitrate, nitrate and TKN) and phosphorus (total phosphorus and reactive phosphorus) nutrients.

9.4.5.9 There were 46 Category M samples with slightly exceedance of arsenic concentration for the LCEL (maximum: 22 mg/kg dry weight). There were 4 Category H samples with exceedance of nickel concentration for the UCEL (maximum: 59 mg/kg dry weight), chromium concentration for the LCEL (n=1, 88 mg/kg dry weight) or zinc concentration for the LCEL (n=3, maximum: 257 mg/kg dry weight). It should be noted that all tested samples had their total PAHs, total PCBs, TBT in interstitial water, and chlorinated pesticides below their respective analytical reporting limit (total PAHs: low molecular weight PAHs <55 μg/kg dry weight and high molecular weight PAH <170 μg/kg dry weight; total PCBs: <2 μg/kg dry weight; TBT in interstitial water: <0.015 μg/l; and chlorinated pesticides: <0.2 mg/kg dry weight). The 46 Category M samples (36.5% of 126 samples) were further tested for the biological screening in accordance with the ETWB TC(W) No.34/2002, in which 26 composite samples were formed. Half of the samples failed the biological screening.

9.4.5.10 There were 43 sediment samples tested for the elutriate testing. All the elutriate samples had the following parameters to be determined below the respective analytical reporting limits: cadmium <0.2 μg/l; mercury <0.1 μg/l; silver <1 μg/l; total PAHs: low molecular weight PAHs <0.1 μg/l per component and high molecular weight PAHs <0.1 μg/l per component; total PCBs <0.01 μg/l per congener; TBT <0.015 μg/l; and chlorinated pesticides <0.02 μg/l. Chromium was only detected in 2 samples (maximum: 2 μg/l), while lead was detected in 3 samples (maximum: 18 μg/l). Copper (range: <1-2.7 μg/l), nickel (range: <1-5.2 μg/l) and zinc (<4-14 μg/l) were occasionally detected, while arsenic was always detected (range: <2-9.8 μg/l). Ammonia (range: 130-2,100 μg/l), nitrite (range: 10-460 μg/l), nitrate (8-600 μg/l), TKN (range: 160-2,600 μg/l), total phosphorus (range: 0.1-0.27 mg/l) and reactive phosphorus (range: <2-110 μg/l) were detected in almost all elutriate samples.

AAHK – Non-Statutory Marine Environmental Monitoring

9.4.5.11 The AAHK has undertaken a programme of non-statutory marine environmental monitoring to verify the environmental performance of the airport platform. The programme included the collection of sediments using surface grab and three rounds of non-statutory monitoring have been conducted so far. The first round was conducted in 1999-2000 which included two sampling events. The second round was conducted in 2002-2003 which included 1 sampling event. The third round was conducted in 2005-2006 which also included 1 sampling event. The sediment monitoring stations were the same over the 3 rounds of monitoring although fewer stations were monitored in the second and third rounds. The locations of the latest monitoring stations are shown in Figure 9.7.

9.4.5.12 Sediment samples were analysed for the same suite of contaminants as listed in the ETWB TC(W) No.34/2002 including metals, metalloid, total PAHs and total PCBs, but there was no TBT. Chlorinated pesticides (15 components) were also analysed.

9.4.5.13 The monitoring results are summarised in Table 9.8 for the ETWB TC(W) No.34/2002 criteria on metals and metalloid. The total PAHs, total PCBs and chlorinated pesticides were below the analytical reporting limits (comparable to the requirement of ETWB TC(W) No.34/2002) and the results are not presented.

Table 9.8 Summary of AAHK Non-statutory Sediment Quality Monitoring Results (1999-2006)

Contaminant	Unit	Range	LCEL	UCEL
As	mg/kg dry weight	6.4 - 24.7	12	42
Cd	mg/kg dry weight	<0.05 - 0.29	1.5	4
Cr	mg/kg dry weight	16 - 60	80	160
Cu	mg/kg dry weight	16 - 52	65	110
Hg	mg/kg dry weight	<0.05 - 0.21	0.5	1
Ni	mg/kg dry weight	10 - 39	40	40
Pb	mg/kg dry weight	26 - 62	75	110
Ag	mg/kg dry weight	0.1 - <1	1	2
Zn	mg/kg dry weight	63 - 157	200	270

Study for New Contaminated Mud Disposal Facility (East of Sha Chau Pit V)

9.4.5.14 Sediment quality analyses were conducted under the Agreement No. CE 12/2002(EP) Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/East of Sha Chau Area. There were 12 vibrocores collected (Figure 9.7), yielding 68 sub-samples with a maximum depth of 20m investigated. The results suggested that most of the sediment samples were uncontaminated, but 2 sub-samples (10.9-11.9m of V10 and 14.9-15.9m of V11) indicated the exceedance of UCEL for nickel and zinc concentrations. Some sub-samples of V2 (15-16m), V7 (0.9-1.9m), V8 (9.9-10.9m, 18.8-19.8m) and V9 (0-0.9m, 0.19-1.9m and 1.9-2.9m) also exhibited marginal exceedance of the LCEL for arsenic, except a sub-sample of V2 (15-16m, exceeding LCEL of silver) and V9 (0-0.9m, marginal exceedance of LCEL for arsenic and mercury). Concentrations of total PAHs and total PCBs of all samples were determined to be below the analytical report limits. There were 4 out of 8 composite Category M samples have failed the subsequent biological test. Based on the test results, 84% of samples were uncontaminated (Category L), 13% were moderately contaminated (Category M) and 3% were highly contaminated (Category H).

HKBCF and HKLR (EIAs)

9.4.5.15 The details for the sediments sampling and results are presented in Section 7 and a summary is provided below.

9.4.5.16 There were 80 sub-samples from 10 vibrocores and 37 sub-samples from 6 vibrocores undertaken in the marine investigation for the reclamation of HKBCF and HKLR, respectively, in 2008 and 2009.

9.4.5.17 With reference to the chemical tests under the ETWB TC(W) No.34/2002, 90 samples exhibited compliance with the LCEL, but 27 samples showed exceedance of LCEL, which required biological tests to confirm their disposal options. All chemical exceedances were due to the metalloid arsenic (As) concentrations, except one case which was due to lead (Pb). Biological screening results for the samples from the HKBCF showing exceedance of the LCELs indicated that some of them should be disposed of at the confined mud pit, whilst some of them could be considered for Open Sea Disposal (Dedicated Sites).

9.4.5.18 Elutriate tests and porewater tests of sediment samples were carried out for the purpose of assessing the potential extent of contaminant release when dredging activities take place. The testing parameters for both tests included heavy metals (cadmium, chromium, copper, mercury, nickel, lead, zinc and silver), metalloid (arsenic) and organic micro-pollutants (PCB, PAHs and TBT), chlorinated pesticides and nutrients including TKN, NO₃-N, NO₂-N, NH₄-N, PO₄-P and total phosphorus. In respect of the elutriate test results, in general, the levels of cadmium, chromium, mercury, silver, TBT, PAHs, PCBs and Pesticides were mostly below the reporting limits, whereas other metals and metalloid including copper, nickel, zinc and arsenic, and nutrients including NH₃-N, NO₂-N, NO₃-N, TKN, PO₄-P and total phosphorus in elutriates varied among sediment samples from different locations. For porewater, the levels of cadmium, chromium, mercury, silver, PAHs, PCBs, TBT and Pesticides were mostly below the reporting limits, whereas other metals and metalloid including copper, nickel, lead, zinc and arsenic, and nutrients including NH₃-N, NO₂-N, NO₃-N, TKN, PO₄-P and total phosphorus in porewater samples varied among sediment samples from different locations.

TMCLKL

9.4.5.19 Sampling works were conducted by the Term Contractor of Geotechnical Engineering Office (GEO) of the Civil Engineering and Development Department (CEDD) between September and October 2008. Vibrocoring at 10 locations was undertaken for the TMCLKL, as shown in Figure 9.7 to reflect the areas of the preferred reclamation landfalls and marine viaduct alignment. The details for the sediments sampling and results are presented in Appendix 9D1 and a summary provided below.

9.4.5.20 There were 23 sediment sub-samples at the 10 vibrocore locations near the proposed route alignment and reclamation landfalls of the TMCLKL. With reference to the chemical tests under the ETWB TC(W) No.34/2002, 18 samples exhibited compliance with the LCEL, but 5 samples showed exceedance of LCEL, which required biological tests to confirm their disposal options. The chemical exceedance included metal (Pb), metalloid (As) and micro-organic pollutants (high molecular weight PAHs) concentrations. However, all of these 5 samples with exceedances of the LCEL passed the biological test. In summary, two classifications of sediment material have been identified, comprising Category L and Category M, that passes the biological testing (M_p). The materials are suitable for disposal in Type 1 open sea and Type 1 Open Sea (Dedicated) disposal, respectively.

9.4.5.21 Elutriate tests and porewater tests of the grab sediment samples were, also, carried out for the purpose of assessing the potential extent of contaminant release when dredging activities take place. The testing parameters for both tests included heavy metals (cadmium, chromium, copper, mercury, nickel, lead, zinc and silver), metalloid (arsenic) and organic micro-pollutants (PCB, PAHs and TBT), chlorinated pesticides and nutrients including TKN, NO₃-N, NO₂-N, NH₄-N, PO₄-P and total phosphorus. In respect of the elutriate test results, in general, the levels of cadmium, silver, TBT, PAHs, PCBs and Pesticides were all below the reporting limits, whereas other metals and metalloid including chromium, copper, mercury, nickel, lead, zinc and arsenic, and nutrients including NH₃-N, NO₂-N, NO₃-N, TKN, PO₄-P and total phosphorus in elutriates varied among sediment samples from different locations. For porewater, the levels of cadmium, lead, mercury, silver, PAHs, PCBs and TBT were all below the reporting limits, whereas other metals and metalloid including chromium, copper, nickel, zinc and arsenic, nutrients including NH₃-N, NO₂-N, NO₃-N, TKN, PO₄-P and total phosphorus in porewater samples varied among sediment samples from different locations.

Summary of Sediment Quality

9.4.5.22 In conclusion, there is an abundance of sediment quality data pertaining to the study area for this assessment which indicates that the sediments are overall not contaminated with only a few exceptions.

9.5 Assessment Criteria

9.5.1 Water Quality Objectives

9.5.1.1 For the WCZs of interest, the WQO for suspended solids is defined as “waste discharge not to raise the natural ambient level by 30% nor cause the accumulation of suspended solids which may adversely affect aquatic communities”. It is expected that the North Western WCZ will experience the largest impact from the construction works but the Western Buffer WCZ could also be impacted to some extent. As a result, in order to determine the ambient suspended solids concentrations in the waters likely to be impacted by the construction works, data in the North Western and Western Buffer WCZs from EPD’s routine water quality monitoring programme from 1998 to 2007 at Stations NM1, NM2, NM3, NM5, NM6, NM8 and WM4 and WM3 (see Figure 9.5) have been analysed.

9.5.1.2 The EPD data is obtained near the sea surface, mid-depth and near the seabed and a summary of the statistics are presented below in Tables 9.9a and 9.9b, where the wet season has been taken to be from mid-April until the end of September each year.

Table 9.9a Suspended solids concentrations from EPD Routine Monitoring Programme (1998-2007)

Station	Suspended Solids Concentrations (mg/L) 1998 - 2007
	Surface		Middle		Bed		Depth Averaged
	Dry Season	Wet Season	Dry Season	Wet Season	Dry Season	Wet Season	Dry Season	Wet Season
NM1	7.3	5.4	9.8	6.5	13.4	12.3	10.2	7.9
NM1	(43-1)	(25-0.7)	(43-1.1)	(21-1.3)	(53-1.4)	(45-1.2)	(41-1.5)	(20.5-3.1)
NM2	6.7	4.4	8.7	4.9	12.1	7.7	9.1	5.6
NM2	(21-1.1)	(9.7-1.2)	(28-1.6)	(14-1)	(47-2.2)	(32-1.7)	(30-1.7)	(17.3-2.4)
NM3	7.1	5.3	9.3	7.2	15.4	13.8	10.6	8.8
NM3	(16-1.6)	(15-1.2)	(21-1.2)	(20-1.4)	(71-2.3)	(46-2.1)	(32.3-1.9)	(23-2.7)
NM5	8.4	6.5	10.4	7.9	20.8	27.7	13.2	14
NM5	(19-1.6)	(17-1.2)	(29-1.6)	(44-2.3)	(81-2.3)	(210-3.2)	(37.7-2)	(86.9-3.3)
NM6	10.2	5.4	11.4	6.2	16.0	12.4	12.5	8.3
NM6	(32-2.9)	(12-0.9)	(40-2.1)	(12-1.8)	(60-3.2)	(84-2.4)	(42.7-2.8)	(35.7-2.6)
NM8	11.6	5.9	14.7	8.8	21.9	16.5	16	10.3
NM8	(48-1.3)	(17-2.4)	(63-2.6)	(25-2.0)	(73-3.6)	(63-2.4)	(56.7-2.7)	(30.5-4.5)
WM4	6.9	3.9	11.1	6.2	14.8	12.7	10.9	7.6
WM4	(21-0.8)	(7.9–0.9)	(52-0.6)	17-1.2	(80-1.5)	(110-1.2)	(49-1.3)	(40-1.2)
WM3	6.6	4.7	8.1	6.4	11.1	8.5	8.7	6.7
WM3	(17-1.4)	(18-1.0)	(19-1.0)	(26-1.2)	(32-1.4)	(30-1.2)	(19.8-1.3)	(17.3-1.1)

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

Table 9.9b 90th Percentile Suspended solids from EPD Routine Monitoring Programme (1998-2007)

Station	90th Percentile Suspended solids Concentrations (mg/L)
	Surface				Middle				Bed				Depth Averaged
	Dry Season		Wet Season		Dry Season		Wet Season		Dry Season		Wet Season		Dry Season		Wet Season
NM1	14.6	8.1		17.6		11.2		34.0		21.0		20.4		12.4
NM2	11.1	6.9		17.5		8.2		20.2		13.0		15.5		9.4
NM3	12.0	8.2		16.0		12.5		27.0		23.2		17.9		13.5
NM (1,2,3)	12.0	7.7		17.0		10.9		27.0		20.0		18.5		12.2
NM5	15.2	11.6		18.4		11.0		46.2		46.2^*		26.9		21.0^*
NM6	21.0	8.4		22.8		9.6		31.0		23.6		25.8		13.0
NM8	21.5	10.2		28.0		18.1		43.2		28.8		30.6		18.8
NM(5,6,8)	19.0	10.0		25.8		12.0		39.4		34.4		27.7		18.7
WM4	13.0	5.7		20.0		9.5		30.0		20.0^*		20.2		11.3^*

Notes *=outliers (unusual high SS removed) before the percentile calculation.

NM(1,2,3) = pooled results by combining the data set from NM1, NM2 and NM3

NM(5,6,8)=pooled results by combining the data set from NM5, NM6 and NM8

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

9.5.1.4 As indicated in Table 9.9a above, monitoring results of the NM1, NM2 and NM3 at the eastern half of the NWWCZ is fairly homogenous and reasonably distinct from the NM5, NM6 and NM6 at western side of NWWCZ. Based on the hydrodynamic of the NWWCZ, major flows at the western side is mainly north-south and more heavily influenced by the Pearl River discharge and this would also accounted for the higher ambient SS level recorded. Based on the data pattern, it is proposed to group the stations of similar characteristics with respect to the SS together into two parts, the eastern NM(1,2,3) and western NM(5,6,8). This simplified the WQO assignment exercise although the calculated 90 percentile for each individual station is also included in Table 9.9b as reference. The delineation of the eastern and western parts and also the EPD stations are presented in Figure 9.5.

9.5.1.5 The WQO is usually interpreted as applying to the depth averaged Suspended solids concentrations. However, near bed suspended solids concentrations, especially when impacted by dredging and filling works, can be significantly larger than the depth averaged suspended solids concentrations. As a result, when assessing the impacts of the dredging and filling works on the suspended solids concentrations, it is proposed that while the principal assessment criteria shall be the depth averaged 90th%ile concentrations in Table 9.9b, a secondary WQO criteria for each depth shall also be referenced in the assessment, especially when a higher SS elevation at the bottom level can be expected and that SS at bottom level are naturally higher than the water column. The WQO for each EPD monitoring station derived in this way are presented in Table 9.10.

Table 9.10 Water Quality Objectives for the Assessment of Elevations in Suspended Solids Concentrations (mg/L) due to Construction Impacts

Station	90th Percentile Suspended solids Concentrations (mg/L)
	Surface		Middle		Bed		Depth Averaged
	Dry Season	Wet Season	Dry Season	Wet Season	Dry Season	Wet Season	Dry Season	Wet Season
NM1	4.4	2.4	5.3	3.4	10.2	6.3	6.1	3.7
NM2	3.3	6.1	5.3	2.5	6.1	3.9	4.6	2.8
NM3	3.6	2.4	4.8	3.8	8.1	7.0	5.4	4.1
NM (1,2,3)	3.6	2.3	5.1	3.3	8.1	6.0	5.5	3.7
NM5	4.6	3.5	5.5	3.3	13.9	13.9^*	8.1	6.3^*
NM6	6.3	2.5	6.8	2.9	9.3	7.1	7.8	3.9
NM8	6.5	3.1	8.4	5.4	13.0	8.6	9.2	5.7
NM(5,6,8)	5.7	3.0	7.7	3.6	11.8	10.3	8.3	5.6
WM4	3.9	1.7	6.0	2.8	9.0	6.0^*	6.1	3.4^*

Notes *=outliers (unusual high SS removed) before the percentile calculation.

NM(1,2,3) = pooled results by combining the data set from NM1, NM2 and NM3

NM(5,6,8)=pooled results by combining the data set from NM5, NM6 and NM8

9.5.1.6 Based upon the values detailed in Table 9.10 above, each specific point / sensitive receiver that will be included in the water quality model has been assigned a specific WQO for suspended solids, as detailed in Table 9.11.

Table 9.11 Water Quality Objectives for Observation Points and Water Sensitive Receivers

			Associated EPD Station	WQO/WQC
Observation	Point			Dry Season				Wet Season
Points	SR	Name		S	M	B	DA	S	M	B	DA
WSR 08	Yes	Lung Kwu Sheung Tan (non-gazetted beach)	NM5,6,8	5.7	7.7	11.8	8.3	3.0	3.6	10.3	5.6
WSR 09a	No	Urmston Road (Main Channel)	NM5,6,8	5.7	7.7	11.8	8.3	3.0	3.6	10.3	5.6
WSR 10	Yes	Sha Chau and Lung Kwu Chau Marine Park	NM5,6,8	5.7	7.7	11.8	8.3	3.0	3.6	10.3	5.6
WSR 11	Yes	Castle Peak Power Station Cooling Water Intake (Note 1)	-	764	764	764	764	764	764	764	764
WSR 12	Yes	Butterfly Beach (gazetted beach)	NM1,2,3	3.6	5.1	8.1	5.5	2.3	3.3	6.0	3.7
WSR 13	Yes	WSD Seawater Intake at Tuen Mun	NM1,2,3	3.6	5.1	8.1	5.5	2.3	3.3	6.0	3.7
WSR 15	Yes	Gazetted Beaches at Tuen Mun	NM1,2,3	3.6	5.1	8.1	5.5	2.3	3.3	6.0	3.7
WSR 18	Yes	Gazetted Beaches along Castle Peak Road	NM1,2,3	3.6	5.1	8.1	5.5	2.3	3.3	6.0	3.7
WSR 19	Yes	Gazetted Beaches at Ma Wan	WM4	3.9	6.0	9.0	6.1	1.7	2.8	6.0	3.4
WSR 20	Yes	Ma Wan Fish Culture Zone (Note 2)	-	39.1	39.1