EIA Report - Part 2 Section6

Table 6.1 Water Qulaity Objectives Application to the Study~~Table~~ 6.1 ~~Water Quality Objectives Applicable to the Study~~

Water Quality Objective	Deep Bay WCZ	North Western WCZ	Southern WCZ
A. AESTHETIC APPEARANCE
a) Waste discharges shall cause no objectionable odours or discolouration of the water.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
b) Tarry residues, floating wood, articles made of glass, plastic, rubber or of any other substances should be absent.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
c) Mineral oil should not be visible on the surface. Surfactants should not give rise to a lasting foam.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
d) There should be no recognisable sewage-derived debris.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
e)Floating, submerged and semi-submerged objects of a size likely to interfere with the free movement of vessels, or cause damage to vessels, should be absent.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
f) Waste discharges shall not cause the water to contain substances which settle to form objectionable deposits.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
B. BACTERIA
a) The level of Escherichia coli should not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in one calendar year..	Secondary Contact Recreation Subzone and Mariculture Subzone	Secondary Contact Recreation Subzone and North Western Supplementary Zone	Secondary Contact Recreation Subzones and Fish Culture Subzones; and Second Southern Supplementary Zone
b)The level of Escherichia coli should not exceed 180 per 100 mL, calculated as the geometric mean of all samples collected from March to October inclusive in one calendar year. Samples should be taken at least 3 times in a calendar month at intervals of between 3 and 14 days.	Yung Long Bathing Beach Subzone	Bathing Beach Subzone	Bathing Beach Subzones
c)The level of Escherichia coli should be less than 1 per 100 mL, calculated as the geometric mean of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days.	-	-	Southern Supplementary Zone
C. DISSOLVED OXYGEN
a)Waste discharges shall not cause the level of dissolved oxygen to fall below 4 mg per litre for 90% of the sampling occasions during the year; values should be taken at 1 metre below surface.	Inner Marine Subzone excepting Mariculture Subzone	-	-
b)Waste discharges shall not cause the level of dissolved oxygen to fall below 4 mg per litre for 90% of the sampling occasions during the year; values should be calculated as water column average. In addition, the concentration of dissolved oxygen should not be less than 2 mg per litre within 2 metres of the seabed for 90% of the sampling occasions during the year.	Outer Marine Subzone excepting Mariculture Subzone (water column average specified as arithmetic mean of at least 2 measurements at 1 metre below surface and 1 metre above seabed)	Marine Waters (water column average specified as arithmetic mean of at least 3 measurements at 1 metre below surface, mid-depth and 1 metre above seabed); and North Western Supplementary Zone	Marine waters excepting Fish Culture Subzones and Second Supplementary Zone
c)The dissolved oxygen level should not be less than 5 mg per litre for 90% of the sampling occasions during the year; values should be taken at 1 metre below surface.	Mariculture Subzone	-	Fish Culture Subzones
d)Waste discharges shall not cause the level of dissolved oxygen to be less than 4 milligrams per litre.	-	-	Inland waters of the Zone and Southern Supplementary Zone
D. pH
a) The pH of the water should be within the range of 6.5 - 8.5 units. In addition, waste discharges shall not cause the natural pH range to be extended by more than 0.2 units.	Marine waters excepting Yung Long Bathing Beach Subzone	Marine waters (including North Western Supplementary Zone) excepting Bathing Beach Subzones	Beach Subzones; Mui Wo (A), Mui Wo (B), Mui Wo (C), Mui Wo (E), Mui Wo (F) Subzones; and Second Southern Supplementary Zone
b)The pH of the water should be within the range of 6.0 - 9.0 units for 95% of samples. In addition, waste discharges shall not cause the natural pH range to be extended by more than 0.5 units.	Yung Long Bathing Beach Subzone	Bathing Beach Subzones	Bathing Beach Subzones
c) The pH of the water should be within the range of 6.0-9.0 units.	-	-	Mui Wo (D) Sub-zone and other inland waters
d)Human activity should not cause the pH of the water to exceed the range of 6.5-8.5 units.	-	-	Southern Supplementary Zone
E. TEMPERATURE
Waste discharges shall not cause the natural daily temperature range to change by more than 2.0 ^oC.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
F. SALINITY
Waste discharges shall not cause the natural ambient salinity level to change by more than 10%.	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
G. SUSPENDED SOLIDS
a)Waste discharges shall neither cause the natural ambient level to be raised by 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.	Marine waters	Marine waters (including North Western Supplementary Zone)	Marine waters (including Second Southern Supplementary Zone)
b)Waste discharges shall not cause the annual median of suspended solids to exceed 20 milligrams per litre.	-	-	Beach Subzones; Mui Wo (A), Mui Wo (B), Mui Wo (C), Mui Wo (E), Mui Wo (F) Subzones; and Southern Supplementary Zone
c)Waste discharges shall not cause the annual median of suspended solids to exceed 25 milligrams per litre.	-	-	Mui Wo (D) Subzone and other Inland Waters
H. AMMONIA
The un-ionized ammoniacal nitrogen level should not be more than 0.021 mg per litre, calculated as the annual average (arithmetic mean).	Whole zone	Whole zone (including North Western Supplementary Zone)	Whole zone (including Southern Supplementary Zone and Second Southern Supplementary Zone)
I. NUTRIENTS
a)Nutrients shall not be present in quantities sufficient to cause excessive or nuisance growth of algae or other aquatic plants.	Inner and Outer marine Subzones	Marine waters (including North Western Supplementary Zone)	Marine waters (including Second Southern Supplementary Zone)
b)Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.1 milligram per litre, expressed as annual water column average (arithmetic mean of at least 3 measurements at 1 metre below surface, mid-depth and metre above seabed).	-	-	Marine waters (including Second Southern Supplementary Zone)
c)Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.3 mg per litre, expressed as annual water column average (arithmetic mean of at least 3 measurements at 1m below surface, mid-depth and 1m above seabed).	-	Castle Peak Bay Subzone	-
d)Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.7 mg per litre, expressed as annual mean.	Inner Marine Subzone	-	-
e)Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.5 mg per litre, expressed as annual water column average.	Outer Marine Subzone (water column average specified as arithmetic mean of at least 2 measurements at 1 metre below surface and 1 metre above seabed)	Marine waters (including North Western Supplementary Zone) excepting Castle Peak Bay Subzone (water column average specified as arithmetic mean of at least 3 measurements at 1m below surface, mid-depth and 1m above seabed)	-
J. 5-DAY BIOCHEMICAL OXYGEN DEMAND
a) Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 5 milligrams per litre.	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Inland waters (except the subzones stated in b))	Inland waters of the Zone
b) Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 3 milligrams per litre.	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Southern Supplementary Zone
K. CHEMICAL OXYGEN DEMAND
a) Waste discharges shall not cause the chemical oxygen demand to exceed 30 milligrams per litre.	Yuen Long & Kam Tin (Lower) Subzone and other inland waters	Inland waters (except the subzones stated in b))	Inland waters of the Zone
b) Waste discharges shall not cause the chemical oxygen demand to exceed 15 milligrams per litre.	Yuen Long & Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and Water Gathering Ground Subzones	Tuen Mun (A), Tuen Mun (B) and Tuen Mun (C) Subzones and Water Gathering Ground Subzones	Southern Supplementary Zone
L. TOXINS
a)Waste discharges shall not cause the toxins in water to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to interactions of toxic substances with each other.	Whole zone	Whole zone (including North Western Supplementary Zone)	Southern Supplementary Zone and Second Southern Supplementary Zone
b)Waste discharges shall not cause a risk to any beneficial uses of the aquatic environment.	Whole zone	Whole zone (including North Western Supplementary Zone)	Southern Supplementary Zone and Second Southern Supplementary Zone
M. DANGEROUS SUBSTANCES
a) Waste discharges shall not cause the concentrations of dangerous substances in marine waters to attain such levels as to produce significant toxic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to toxicant interactions with each other.	-	-	Whole zone
b) Waste discharges of dangerous substances shall not put a risk to any beneficial uses of the aquatic environment.	-	-	Whole zone
N. PHENOLS
Phenols shall not be present in such quantities as to produce a specific odour, or in concentration greater than 0.05 mg per litre as C₆H₅OH.	Yung Long Bathing Beach Subzone	Bathing Beach Subzones	-
O. TURBIDITY
Waste discharges shall not reduce light transmission substantially from the normal level.	Yung Long Bathing Beach Subzone	Bathing Beach Subzones	-

6.2.2 Technical Memorandum Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters

All discharges during both the construction and operational phases of the proposed development are required to comply with the Technical Memorandum Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM) issued under Section 21 of the WPCO.

The TM defines acceptable discharge limits to different types of receiving waters. Under the TM, effluents discharged into the drainage and sewerage systems, inshore and coastal waters of the WCZs are subject to pollutant concentration standards for specified discharge volumes. These are defined by the Environmental Protection Department (EPD) and are specified in licence conditions for any new discharge within a WCZ.

The proposed LNG terminal at South Soko will be required to comply with Table 10a of the TM - Standards for effluents discharged into the inshore waters of Southern, Mirs Bay, Junk Bay, North Western, Eastern Buffer and Western Buffer Water Control Zones.

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

Annexes 6 and 14 of the EIAO-TM provide general guidelines and criteria to be used in assessing water quality impacts.

The EIAO-TM recognises that, in the application of the above water quality criteria, it may not be possible to achieve the WQO at the point of discharge as there are areas which are subjected to greater impacts (which are termed by the EPD as the mixing zones), where the initial dilution of the discharge takes place. The definition of this area is determined on a case-by-case basis. In general, the criteria for acceptance of the mixing zones are that it must not impair the integrity of the water body as a whole and must not damage the ecosystem.

6.2.4 Suspended Solids Impacts

The Water Quality Objective (WQO) for suspended solids in marine waters of the Southern WCZ, the North Western WCZ and the Deep Bay WCZ states that:

Waste discharges shall neither cause the natural ambient level to be raised by 30% nor give rise to accumulation of suspended solids, which may adversely affect aquatic communities

As the proposed submarine pipeline alignment passes through these three WCZs, the impact assessment of the submarine pipeline will be divided between the respective WCZs.

Analysis of EPD routine water quality monitoring data from the years of 1996 to 2006 has been undertaken to determine the allowable increase in suspended solids concentrations within the WCZ. Data have been analysed from EPD monitoring stations that are in the proximity of the proposed works (Figure 6.2).

The SS criterion, in accordance with the WQO, at specific sensitive receivers is discussed in Section 6.3.5, Part 2.

WQO for SS in Deep Bay Water Control Zone

Suspended solids data from EPD monitoring station DM4 and DM5, have been analysed to determine the allowable increase at the sensitive receivers close to the shore approach at Black Point within the outer Deep Bay WCZ. For those sensitive receivers within the inner Deep Bay WCZ, the SS criterion will make reference to station DM4.

WQO for SS North Western Water Control Zone

Suspended solids data from EPD monitoring stations NM5, NM6 and NM8, have been analysed to determine the allowable increase at the sensitive receivers close to relevant sections of the proposed submarine gas pipeline.

WQO for SS Southern Water Control Zone

Suspended solids data from EPD monitoring station SM20 have been analysed to determine the allowable increase at sensitive receivers close to the proposed terminal at South Soko within the Southern WCZ. The SS criteria derived from stations SM13 and SM17 will be used for those respective sensitive receivers near to them.

SS Criterion for Seawater Intakes

The power station intakes have specific requirements for intake water quality. The applicable criteria for the Black Point Power Station and Castle Peak Power Station seawater intakes are temperature between 17 and 32°C and SS levels below 764 mg L^-1 respectively. It is hence reasonable to adopt an SS assessment criterion of 700 mg L^-1 for these two seawater intakes.

There are no particular criteria specified for the industrial intake at Tuen Mun Area 38, the Airport intakes ([1]) and Tai Kwai Wan pumping station intakes and hence the WQO was used as the criteria for these intakes.

The Water Supplies Department (WSD) has a set of standards for the quality of abstracted seawater (Table 6.2). Water quality at the Tuen Mun WSD sea water intake has been assessed against these standards, in addition to the WQOs.

Table 6.26.2 WSD Water Quality Criteria for Abstracted Seawater

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

SS Criterion for Fish Culture Zones

There is a general water quality protection guideline for suspended solids (SS), which has been proposed by the AFCD ([2]). The guideline requires the maximum SS levels to remain below 50 mg L^-1. This criterion has been adopted in approved EIA Reports ([3]) ([4]).

~~There is a general water quality protection guideline for suspended solids (SS), which has been proposed by the AFCD (~~~~[5]). The guideline requires the maximum SS levels to remain below 50 mg L^-1.~~ ~~This criterion has been adopted in approved EIA Reports~~ (~~[6]) (~~~~[7]~~).

· SS Criterion for Subtidal Hard Bottom Habitat

There are no established legislative criteria for water quality at subtidal hard bottom habitat (coral). An elevation criterion of 10 mg L^-1 in SS has been adopted as the critical value above which impacts to the habitat may occur, as adopted in approved EIA Reports ([8]).

6.2.5 Sediment Quality

Dredged sediments destined for marine disposal are classified according to a set of regulatory guidelines (Management of Dredged / Excavated Sediment, ETWBTC No. 34/2002) issued by the Environment, Transport and Works Bureau (ETWB) in August 2002. These guidelines comprise a set of sediment quality criteria, which include organic pollutants and other substances. The requirements for the marine disposal of sediment are specified in the ETWBTC No. 34/2002. Marine disposal of dredged materials is controlled under the Dumping at Sea Ordinance 1995.

6.2.6 Other Assessment Criteria

Sediment Deposition

In the marine ecological impact assessment, a hard coral species was found at the south western coast of South Soko (see Part 2 - Sections 6.3 and 6.9). Impacts to coral communities have also been assessed with regard to sediment deposition. The assessment criterion of 200 g m^-2 day^-1, has been used in an approved EIA Report ([9]) and has been adopted here. Impacts to artificial reefs (ARs) through deposited sediments have also been assessed using this criterion.

Dissolved Oxygen

The release of sediment contaminants into the water column or the effluent discharge due to the Project may consume the dissolved oxygen (DO) in the receiving water. Oxygen depletion resulting from the dredging operations or the effluent discharge will be assessed against the WQO. The allowable change in DO levels in each WCZ has been calculated based on the EPD routine water quality monitoring data over the period 1996 to 2006.

The assessment criterion for DO, in accordance with the WQO, at each sensitive receiver is discussed in Section 6.3.5, Part 2.

In addition, the WQO that is specific to Fish Culture Zones is set at no less than 5 mg L^-1measured at 1 m below the water surface (Table 6.1).

Dissolved Metals and Organic Compounds

There are no quantitative standards for dissolved metals in the marine waters of Hong Kong. It is thus proposed to make reference to the relevant UK water quality standards ([10]). This standard has been adopted in the previous approved EIAs, i.e., EIA for Decommissioning of Cheoy Lee Shipyard at Penny’s Bay ([11]), EIA for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit ([12]) and EIA for Wanchai Development Phase II ([13]).

Water sampling was conducted and the results showed that the concentrations of the dissolved metals in the marine water column at all sampling stations were found below the reporting limits, with the exception of copper. This indicates that the ambient concentrations of these dissolved metals are minimal. For copper, the mean concentration has been calculated based on the water sampling results for each WCZ. Table 6.3 shows the assessment criteria and the respective allowable increases for dissolved metals due to the Project.

Table 6.3 Summary of Assessment Criteria and the Allowable Increases for Dissolved Metals due to the Project

Parameter	Assessment Criterion (µg L^-1)	Ambient Concentration ^(a) (µg L^-1)	Allowable Increase (µg L^-1)
Arsenic	25.0	<1	24.5
Cadmium	2.5	<0.5	2.25
Chromium	15.0	<5	12.5
Copper – Deep Bay WCZ	5.0	2.3	2.7
Copper – North Western WCZ	5.0	2.3	2.7
Copper – Southern WCZ	5.0	2.6	2.4
Lead	25.0	<2	24
Mercury	0.3	<0.2	0.2
Nickel	30.0	<2	29.0
Silver	2.3	<1	1.8
Zinc	40.0	<10	35.0
Total PCBs	0.03	-	-
Total PAHs	3.0	-	-
TBT	0.1	-	-
Alpha-BHC	0.0049 ^c	-	-
Beta BHC	0.017 ^c	-	-
Gamma BHC	0.16 ^b	-	-
Delta-BHC	- ^d	-	-
Heptachlor	0.053 ^b	-	-
Aldrin	1.3^b	-	-
Heptachlor epoxide	0.053 ^b	-	-
Alpha Endosulfan	0.034 ^b	-	-
p, p'-DDT	0.13 ^b	-	-
p, p'-DDD	0.00031 ^c	-	-
p, p'-DDE	0.00022 ^c	-	-
Endosulfan sulfate	89 ^c	-	-
Notes: (a) The ambient concentrations were derived from the water sampling results for this project. (b) The water quality criteria were derived from the USEPA water quality criteria. The Criteria Maximum Concentration (CMC) is an estimate of the highest concentration of a material in surface water to which an aquatic community can be exposed briefly without resulting in an unacceptable effect. CMC is used as the criterion of the respective compounds in this study. (c) No saltwater criteria for this chlorinated pesticide were defined by USEPA. The water quality criterion to protect human health for the consumption of aquatic organisms is provided for reference. (d) No water quality criteria for delta-BHC were defined by USEPA.

The water sampling results also showed that the concentrations of the organic compounds were all below the reporting limits. There are no existing regulatory standards or guidelines for total PCBs, total PAHs and TBT in water and hence reference has been made to the USEPA water quality criteria ([14]), Australian water quality guidelines ([15]), and international literature ([16]), , respectively. The assessment criteria for total PCBs, total PAHs and TBT are 0.03 µg L^-1, 3.0 µg L^-1 and 0.1 µg L^-1.

Residual Chlorine

As discussed in the Project Description (Section 3) the water system used to warm up the LNG will require the use of chlorine as an antifoulant. The resultant discharge to the marine environment will contain total residual chlorine. A suggested water quality criterion for total residual chlorine has been proposed by the EPD based on the results of the Harbour Area Treatment Scheme (HATS) Environmental and Engineering Feasibility Assessment Studies. The criterion value of 0.01 mg L^-1 (daily maximum) at the edge of the mixing zone has been chosen as the criterion against which to assess the results from the computer modelling of chlorine dispersion. This is also the criterion adopted in the previously approved EIA for the 1,800 MW Gas-fired Power Station at Lamma Extension ([17]).

6.3 Baseline Conditions and Water Quality Sensitive Receivers

6.3.1 Hydrodynamics

In general, long period swell waves generated in the South China Sea propagate into Hong Kong waters, with energy dissipation due to refraction, diffraction, shoaling, wave breaking, bottom friction and shielding due to offshore islands. This results in wave energy reduction inshore of the outer islands and into shallower Hong Kong waters. It also gives Hong Kong a distinctive two peak frequency distribution, where one peak represents offshore swells and the other the shorter period inshore wind-driven waves. The NE Monsoon is generally stronger and more persistent than the SW Monsoon. The highest percentage of strong winds and hence waves are generated from north to southeast.

Current velocities are influenced by the semi-diurnal tidal regime of the South China Sea and the freshwater flows of the Pearl River Estuary during the wet season. The further upstream of the Pearl River Estuary the greater the tidal distortion, shorter floodtide, longer ebb, and the greater the effect of fresh water flows.

Deep Bay Water Control Zone

The Black Point landing point is surrounded by a shallow and sediment-laden water body in the Outer Deep Bay region between Hong Kong and Shenzhen. Deep Bay has a surface area of approximately 112 km² (11,200 ha) with a length of about 15 km and an average depth of 3 m ([18]). The hydrodynamic regime of the Deep Bay area is unidirectional and the current direction reverses during ebb and flood tides. Tidal flow is dynamic and complex in the Deep Bay areas due to the seasonal influx of freshwater from the Pearl River to the Urmston Road. The Urmston Road is one of the main flow routes into and out of the Pearl River Estuary and carries significant volumes of water on each tide ([19]).

North Western Water Control Zone

The North Western WCZ is situated at the mouth of the Pearl River Estuary and, as such, is heavily influenced by the freshwater flows from the hinterland. The area shows 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 strong salinity and temperature stratification is prominent. During winter months water conditions are more typically marine (with lower nutrient levels and higher DO levels) and 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 East of Sha Chau have been predicted in previous studies to be less than 2.0 m s^-1on the surface and rarely exceeding 0.25 m s^-1 near seabed ([20]).

Southern Water Control Zone

Hydrodynamics at South Soko are influenced by the fringing coastal estuarine plume to the west generated by the output from the Pearl River. These are stronger in the summer months when rainfall increases. Tidal currents are moderate at the south-eastern side of South Soko Island relative to the northern-western side. The northern side of the Island is, however, less exposed to the oceanic swells than the southern side of the Island.

The southern waters are also influenced by the semi diurnal tidal regime of the South China Sea and the freshwater flows of the Pearl River Estuary, particularly during the wet season. The southern waters wave climate is mostly determined by the seasonal monsoon winds, typhoon events and the coastal geomorphology, which influences the wave trains as they propagate inshore. Long period swell waves generated in the South China Sea propagate into Hong Kong waters, with energy dissipation due to refraction, diffraction, shoaling, wave breaking, bottom friction and shielding due to offshore islands.

6.3.2 Water Quality

Water quality has been determined through a review of EPD routine water quality monitoring data collected between 1996 and 2006. This dataset provides Hong Kong’s most comprehensive long term water quality monitoring data and provides an indication of temporal and spatial change in marine water quality in Hong Kong.

Deep Bay Water Control Zone

On the basis of the 1996 to 2006 monitoring data, Dissolved Oxygen (DO) levels in Deep Bay the WCZ exhibited a decline from 1996 to 2003 followed by an increase, whereas, Total Inorganic Nitrogen (TIN) and Unionised Ammonia have been increasing over time. An increasing trend of SS levels between 1998 and 2001 is observed; however, between 2002 and 2006 SS levels have been declining. It is noted from reviewing the data for SS that the range of values recorded is high and values up to 62 mg L^-1 at DM5 and 66 mg L^-1 at DM4 have been recorded. Water quality within the Deep Bay WCZ is generally compliant with the WQOs. The exception as discussed above has been TIN, the levels of which have exceeded the WQO of < 0.5 mg L^-1 in all years. The increased levels in E. coli have been attributed to discharges from the Pearl River Estuary (Table 6.4).

North Western Water Control Zone

The water quality in the North Western WCZ is influenced by effluent discharges from sewage treatment works, such as those at Siu Ho Wan and Pillar Point and Pearl River Delta flows in general. Data collected between 1996 and 2006 indicate that there have been elevations of SS and Unionised Ammonia. A decreasing trend for DO is observed over 1996-2003 and an increase is found afterwards. In terms of compliance with the WQOs, no exceedances have been recorded, with the exception of TIN, which exceeds the WQO of 0.5 mg L^-1 on a continual basis, particularly at NM5 and NM6 (Table 6.4). It is noted from reviewing the data for SS that the range of values recorded is high and values up to 81 mg L^-1 at NM5 and 73 mg L^-1 at NM8 have been recorded. Among the mentioned monitoring stations, NM5 recorded the highest geometric mean of E. coli, equals to 520 cfu 100mL^-1.

Southern Water Control Zone

Data collected between 1996 and 2006 indicate that there is an increasing trend for DO, Unionised Ammonia and TIN within the Southern WCZ and followed by a decrease since 2004. E. coli, has exhibited a decrease since 2002 and E. coli levels in the Southern WCZ are considered to be low in comparison to other stations in Hong Kong. In terms of WQO compliance, only exceedances in TIN (> 0.1 mg L^-1) have been recorded consistently over time (Table 6.4). It is noted from reviewing the data for SS that the range of values recorded is moderate and values up to 53 mg L^-1 at SM20, 40 mg L^-1 at SM17 and 42 mg L^-1 at SM13 have been recorded.

6.3.3 Water Quality in the Marine Park

The Agriculture, Fisheries and Conservation Department (AFCD) commenced a routine water quality monitoring programme in 1999 to collect baseline water quality data from the Sha Chau and Lung Kwu Chau Marine Park. The water quality monitoring results for the Sha Chau and Lung Kwu Chau Marine Park (1999 – 2005) are presented in Table 6.5.

It is apparent from the data that the mean values of suspended sediment range between stations from 9.7 to 37.2 mg L^-1.

Table 6.4 EPD Water Quality Monitoring Data 1996 - 2006 in the Deep Bay, North Western and Southern Water Control Zones

Water Quality Parameter	Deep Bay WCZ		North Western WCZ			Southern WCZ
	DM4	DM5	NM5	NM6	NM8	SM13	SM17	SM20
Temperature (ºC)	23.9	23.6	23.4	23.5	23.5	23.5	23.1	23.4
	(14.4 - 32.8)	(14.4 - 31.1)	(15.5 - 30.3)	(15.1 - 29.8)	(15.4 - 30.1)	(15.5 - 29.8)	(15.6 - 29.8)	(15.4 - 29.8)

pH	7.9	7.9	8.0	8.1	8.1	8.2	8.1	8.1
	(6.3 - 9.0)	(6.2 - 8.7)	(7.3 - 8.7)	(6.9 - 8.5)	(7.4 - 8.7)	(7.6 - 9.1)	(7.2 - 9.3)	(7.6 - 8.9)

Dissolved Oxygen (mg L^-1) Depth-averaged	6.0	5.9	5.9	6.4	6.5	6.9	6.6	6.5
	(0.6 - 10.2)	(2.6 - 10.0)	(2.3 - 9.2)	(3.3 - 11.8)	(2.7 - 11.7)	(1.8 - 10.3)	(2.4 - 10.4)	(2.3 - 9.9)

Dissolved Oxygen (mg L^-1) Bottom	6.1	5.7	5.5	6.3	6.4	6.6	6.1	6.3
	(2.9 - 10.2)	(2.6 - 10.0)	(2.3 - 8.8)	(3.3 - 11.8)	(2.7 - 11.7)	(1.8 - 10.2)	(2.4 - 10.4)	(2.3 - 8.6)

Dissolved Oxygen (% sat.) Depth-averaged	82.2	81.2	80.4	87.2	89.8	97.2	92.6	91.5
	(8.8 - 144.9)	(37.7 - 136.0)	(32.7 - 130.0)	(47.1 - 170.2)	(40.0 - 166.5)	(26.9 - 157.8)	(36.0 - 207.3)	(32.3 - 147.4)

Dissolved Oxygen (% sat.) Bottom	82.5	79.1	76.1	86.5	88.2	93.3	85.4	88.5
	(40.1 - 144.9)	(37.7 - 122.1)	(32.7 - 110.3)	(47.1 - 167.4)	(40.0 - 166.5)	(26.9 - 156.9)	(36.0 - 145.6)	(32.3 - 131.2)

5-day Biochemical Oxygen Demand (mg L^-1)	1.1	0.9	0.8	0.9	0.8	1.0	0.7	0.8
	(<0.1 - 3.7)	(<0.1 - 4.9)	(<0.1 - 4.1)	(<0.1 - 4.9)	(<0.1 - 5.5)	(<0.1 - 6.7)	(<0.1 - 4.0)	(<0.1 - >7.4)

Suspended Solids (mg L^-1)	14.3	11.1	12.3	9.6	13.3	7.8	6.8	10.0
	(2.4 - 66.0)	(1.1 - 62.0)	(1.6 - 81.0)	(0.9 - 48.0)	(1.3 - 73.0)	(1.0 - 42.0)	(0.8 - 40.0)	(1.0 - 53.0)

Total Inorganic Nitrogen (mg L^-1)	1.02	0.67	0.56	0.51	0.33	0.19	0.14	0.19
	(0.13 - 2.77)	(0.14 - 2.46)	(0.03 - 2.30)	(0.01 - 1.74)	(0.01 - 1.80)	(0.02 - 0.59)	(0.01 - 0.68)	(0.01 - 0.87)

Unionised Ammonia (mg L^-1)	0.012	0.007	0.006	0.005	0.003	0.003	0.002	0.002
	(0.000 - 0.050)	(0.000 - 0.028)	(0.000 - 0.027)	(0.000 - 0.027)	(0.000 - 0.016)	(0.000 - 0.011)	(0.000 - 0.008)	(0.000 - 0.009)

Chlorophyll-a (microgram L^-1)	3.2	2.3	2.5	3.4	3.5	5.0	3.2	4.2
	(<0.2 - 63.0)	(<0.2 - 49.0)	(<0.2 - 28.0)	(<0.2 - 44.0)	(<0.2 - 50.0)	(<0.2 - 27.0)	(<0.2 - 30.0)	(0.2 - 28.0)

Escherichia coli (cfu 100mL^-1)	222	408	520	27	3	3	1	1
	(2 - 9,500)	(4 - 41,000)	(4 - 28,000)	(<1 - 4,200)	(<1 - 270)	(<1 - 2,000)	(<1 - 200)	(<1 - 320)

Notes: 1. Data presented are depth averaged calculated by taking the means of three depths, i.e. surface (S), mid-depth (M) and bottom (B), except as specified. 2. Data presented are annual arithmetic means except for E. coli, which are geometric means. 3. Data enclosed in brackets indicate the ranges regardless of the depths. 4. Shaded cells indicate non-compliance with the WQOs. 5. Outliers have been removed.

Table 6.5 Summary of Water Quality in the Sha Chau & Lung Kwu Chau Marine Park ([21])

Water Quality Parameter	Sha Chau and Lung Kwu Chau Marine Park
	N Lung Kwu Chau	N Sha Chau	Pak Chau	SE Sha Chau
	(1999 – 2005)	(1999 – 2000)	(1999 – 2005)	(1999 – 2000)
Temperature (°C)	24.1	24.3	24.1	24.3
Salinity (ppt)	24.7	23.9	25.1	25.1
pH	7.9	8.1	7.9	8.1
Dissolved Oxygen (mg L^-1)	6.2	5.8	6.2	5.8
Turbidity (NTU)	1.1	1.1	1.2	1.3
Suspended Solids (mg L^-1)	20.3	9.7	37.2	10.0
BOD₅ (mg L^-1)	1.1	0.8	1.2	0.7
Ammonia Nitrogen (mg L^-1)	0.2	0.2	0.2	0.2
Unionized Ammonia (mg L^-1)	0.050	0.029	0.071	0.030
Nitrite Nitrogen (mg L^-1)	0.29	0.34	0.29	0.33
Nitrate Nitrogen (mg L^-1)	1.50	3.77	1.38	3.68
Total Inorganic Nitrogen (mg L^-1)	1.38	0.54	1.31	0.56
Total Kjeldahl Nitrogen (mg L^-1)	2.26	3.98	2.37	3.81
Total Nitrogen (mg L^-1)	5.18	14.82	5.13	16.21
Orthophosphate Phosphorus (mg L^-1)	0.27	0.06	0.13	0.05
Total Phosphorus (µg L^-1)	0.74	0.10	0.65	0.09
Silica (mg L^-1)	1.02	1.16	1.02	1.10
Chlorophyll-a (µg L^-1)	2.59	2.59	2.09	2.78
Phaeo-pigment (µg L^-1)	1.90	1.07	1.81	1.09
E. coli (CFU/100 mL)	343	54	201	58
Faecal Coliforms (CFU/100 mL)	1298	117	1070	114
Notes: Data presented are mean depth averaged calculated by taking the means of three depths, i.e. surface (S), mid-depth (M) and bottom (B), except as specified.

Table 6.6 Summary of EPD Sediment Quality Monitoring Data Collected between 1996 and 2005

Parameter	Deep Bay WCZ		North Western WCZ		Southern WCZ	Sediment Quality Criteria
	DS3	DS4	NS4	NS6	SS6	LCEL	UCEL
COD (mg kg^-1)	14,885	14,540	13,635	13,300	9,945	-	-
COD (mg kg^-1)	(7,700 - 18,000)	(8,800 - 20,000)	(6,700 - 19,000)	(7,400 - 20,000)	(7,700 - 12,000)
Total Carbon (% w/w)	0.5	0.6	0.6	0.5	0.5	-	-
Total Carbon (% w/w)	(0.4 - 0.8)	(0.3 - 1.3)	(0.3 - 0.8)	(0.4 - 0.8)	(0.2 - 0.6)
Ammonia Nitrogen (mg kg^-1)	4.9	6.3	14.2	4.3	7.8	-	-
Ammonia Nitrogen (mg kg^-1)	(0.2 - 20.0)	(<0.05 - 36.0)	(0.2 - 39.0)	(0.1 - 16.0)	(0.3 - 21.0)
TKN (mg kg^-1)	316	285	275	269	290	-	-
TKN (mg kg^-1)	(150 - 470)	(110 - 820)	(160 - 530)	(140 - 480)	(200 - 410)
Total Phosphorous (mg kg^-1)	208	165	145	150	191	-	-
Total Phosphorous (mg kg^-1)	(100 - 320)	(77 - 270)	(92 - 220)	(73 - 260)	(130 - 260)
Total Sulphide (mg kg^-1)	44	15	23	6	18	-	-
Total Sulphide (mg kg^-1)	(2 - 160)	(<0.2 - 76)	(<0.2 - 77)	(<0.2 - 38)	(0.2 - 59)
Arsenic (mg kg^-1)	16	14	12	11	6	12	42
Arsenic (mg kg^-1)	(8 - 20)	(8 - 19)	(9 - 18)	(6 - 22)	(5 - 8)
Cadmium (mg kg^-1)	0.2	0.1	0.1	0.1	0.1	1.5	4
Cadmium (mg kg^-1)	(<0.1 - 0.4)	(<0.1 - 0.2)	(<0.1 - 0.2)	(<0.1 - 0.2)	(<0.1 - 0.1)
Chromium (mg kg^-1)	43	32	28	28	23	80	160
Chromium (mg kg^-1)	(23 - 53)	(14 - 50)	(20 - 44)	(15 - 45)	(16 - 32)
Copper (mg kg^-1)	48	26	23	17	12	65	110
Copper (mg kg^-1)	(12 - 77)	(6 - 64)	(17 - 42)	(7 - 34)	(8 - 17)
Lead (mg kg^-1)	54	40	39	30	26	75	110
Lead (mg kg^-1)	(30 - 69)	(18 - 68)	(29 - 47)	(17 - 49)	(22 - 32)

Mercury (mg kg^-1)	0.12	0.07	0.08	0.06	0.06	0.5	1
Mercury (mg kg^-1)	(<0.05 - 0.18)	(<0.05 - 0.15)	(<0.05 - 0.23)	(<0.05 - 0.15)	(<0.05 - 0.10)
Nickel (mg kg^-1)	28	19	18	18	15	40	40
Nickel (mg kg^-1)	(14 - 37)	(7 - 31)	(13 - 30)	(9 - 28)	(11 - 22)
Silver (mg kg^-1)	0.5	0.4	0.4	0.4	0.4	1	2
Silver (mg kg^-1)	(<0.2 - 0.8)	(<0.2 - 0.5)	(<0.2 - 0.5)	(<0.2 - 0.5)	(<0.2 - 0.5)
Zinc (mg kg^-1)	145	96	96	74	66	200	270
Zinc (mg kg^-1)	(69 - 230)	(36 - 180)	(67 - 110)	(34 - 120)	(52 - 86)
Total PCBs (µg kg^-1)	18	18	18	18	18	23	180
Total PCBs (µg kg^-1)	(18 - 18)	(18 - 18)	(18 - 18)	(18 - 18)	(18 - 18)
Low Molecular Wt PAHs (µg kg^-1)	92	91	92	90	90	550	3,160
Low Molecular Wt PAHs (µg kg^-1)	(90 - 96)	(90 - 94)	(90 - 99)	(90 - 94)	(90 - 90)
High Molecular Wt PAHs (µg kg^-1)	83	60	59	29	27	1,700	9,600
High Molecular Wt PAHs (µg kg^-1)	(29 - 151)	(16 - 254)	(21 - 139)	(16 - 84)	(19 - 47)
Notes: 1. Data presented in bracket is the minimum and maximum data range of each parameter. 2. Low Molecular Wt PAHs include acenaphthene, acenaphthylene, anthracene, fluoreneand phenanthrene. 3. High Molecular Wt PAHs include 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. 4. LCEL = Lower Chemical Exceedance Level 5. UCEL = Upper Chemical Exceedance Level 6. Shaded cells indicate exceedance of LCEL

Table 66.7 Shortest Distance to Sensitive Receivers (SRs) around Proposed LNG Terminal at South Soko and Submarine Pipeline Section from South Soko to Black Point

Sensitive Receiver	Name	ID	Shortest Distance to the LNG terminal	Shortest Distance to the Submarine Water Main¹	Shortest Distance to the Submarine Cable¹	Shortest Distance to the Pipeline¹	Assessment Criteria²
*Fisheries and Marine Ecological Sensitive Receivers*
*Fisheries Resources*
Spawning/ Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	2.6 km	1.1 km	1.3 km	2.4 km	Water Quality Objectives (WQO)
		SR27	1.1 km	1.7 km	1.9 km	1.0 km	Water Quality Objectives (WQO)
	Fisheries Spawning Ground in North Lantau	SR8	> 10 km	> 10 km	> 10 km	2.7 km	Water Quality Objectives (WQO)
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	SR6e	> 10 km	> 10 km	> 10 km	< 1 km	· Water Quality Objectives (WQO) · Deposition Rate below 200 gm^-2 day^-1
	Northeast Airport	SR7d	>10 km	> 10 km	> 10 km	7.7 km	· Water Quality Objectives (WQO) · Deposition Rate below 200 gm^-2 day^-1
Fish Fry Habitat	Pak Tso Wan	SR16b	< 1 km	< 1 km	< 1 km	< 1 km	Water Quality Objectives (WQO)
Fish Culture Zone	Cheung Sha Wan FCZ	SR38	> 10 km	> 10 km	> 10 km	> 10 km	Water Quality Objectives (WQO) ; except SS elevation below 50 mgL^-1
	Ma Wan	SR40a-b	> 10 km	> 10 km	> 10 km	> 10 km	Water Quality Objectives (WQO); except SS elevation below 50 mgL^-1
Oyster Production Farm	Pak Nai	SR2	> 10 km	> 10 km	> 10 km	5.1 km	Water Quality Objectives (WQO)
*Marine Ecological Resources*
Seagrass Beds	Pak Nai	SR2	> 10 km	> 10 km	> 10 km	5.1 km	Water Quality Objectives (WQO)
	Tung Chung Bay	SR39	> 10 km	7.8 km	7.8 km	6.6 km	Water Quality Objectives (WQO)
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR6a	> 10 km	> 10 km	> 10 km	< 1 km	Water Quality Objectives (WQO)
		SR6b	> 10 km	> 10 km	> 10 km	< 1 km	Water Quality Objectives (WQO)
		SR6c	> 10 km	> 10 km	> 10 km	1.4 km	Water Quality Objectives (WQO)
		SR6d	> 10 km	> 10 km	> 10 km	2.7 km	Water Quality Objectives (WQO)
	Potential Southwest Lantau Marine Park	SR19a	> 10 km	6.2 km	6.2 km	< 1 km	Water Quality Objectives (WQO)
		SR19b	> 10 km	6.5 km	6.3 km	< 1 km	Water Quality Objectives (WQO)
		SR19c	7.8 km	5.5 km	5.3 km	< 1 km	Water Quality Objectives (WQO)
Intertidal Mudflats	Pak Nai	SR1	> 10 km	> 10 km	> 10 km	1.7 km	Water Quality Objectives (WQO)
	Yi O	SR14	>10 km	5.6 km	5.1 km	1.7 km	Water Quality Objectives (WQO)
	Shui Hau Wan	SR33	6.6 km	2.9 km	2.1 km	5.9 km	Water Quality Objectives (WQO)
Mangroves	Pak Nai	SR2	> 10 km	> 10 km	> 10 km	5.1 km	Water Quality Objectives (WQO)
	Tung Chung Bay	SR39	> 10 km	7.8 km	7.8 km	6.6 km	Water Quality Objectives (WQO)
	Fan Lau Tung Wan	SR15b	7.05 km	3.9 km	3 km	1.8 km	Water Quality Objectives (WQO)
Horseshoe Crab Nursery Grounds	Pak Nai	SR1	> 10 km	> 10 km	> 10 km	1.7 km	Water Quality Objectives (WQO)
	Sham Wat Wan	SR10	> 10 km	6.9km	6.9 km	2.3 km	Water Quality Objectives (WQO)
	Tai O	SR12	> 10 km	5.7 km	5.7 km	1.9 km	Water Quality Objectives (WQO)
	Yi O	SR14	>10 km	5.6 km	5.1 km	1.6 km	Water Quality Objectives (WQO)
	Sha Lo Wan	SR18	> 10 km	7.7 km	7.7 km	3.1 km	Water Quality Objectives (WQO)
	Tong Fuk Miu Wan	SR33	6.6 km	2.9 km	2.1 km	5.9 km	Water Quality Objectives (WQO)
	Tung Chung Bay	SR39	> 10 km	7.8 km	7.8 km	6.6 km	Water Quality Objectives (WQO)
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	>10 km	>10 km	>10 km	4.2 km	Water Quality Objectives (WQO)
		SR11a	>10 km	9.2 km	8.3 km	1.9 km	Water Quality Objectives (WQO)
		SR11b	9.15 km	7.2 km	6. 5 km	1.9 km	Water Quality Objectives (WQO)
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR 31	370 m	1 km	1 km	< 1 km	· Water Quality Objectives (WQO) · SS elevations below 10 mg L^-1 · Deposition rate below 200 g m^-2 day^-1
*Water Quality Sensitive Receivers*
*Others*
Gazetted Beaches	Butterfly Beach	SR5c	>10 km	>10 km	>10 km	8.1 km	Water Quality Objectives (WQO)
	Tuen Mun Beaches	SR5d	>10 km	>10 km	>10 km	>10 km	Water Quality Objectives (WQO)
	Tong Fuk	SR34	7.8 km	4.4 km	4.4 km	6.9 km	Water Quality Objectives (WQO)
	Upper Cheung Sha Beach	SR35	8.93 km	5.9 km	5.9 km	8.0 km	Water Quality Objectives (WQO)
	Lower Cheung Sha Beach	SR36	9.8 km	7.2 km	7.2 km	8.9 km	Water Quality Objectives (WQO)
	Pui O Wan	SR37	> 10 km	9.8 km	9.8 km	>10 km	Water Quality Objectives (WQO)
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR5a	> 10 km	> 10 km	> 10 km	4.0 km	Water Quality Objectives (WQO)
	Lung Kwu Tan	SR5b	> 10 km	> 10 km	> 10 km	4.7 km	Water Quality Objectives (WQO)
	Fan Lau Sai Wan	SR15a	7.95 km	4.7 km	3.8 km	1.4 km	Water Quality Objectives (WQO)
	Fan Lau Tung Wan	SR15b	7.05 km	3.9 km	3 km	1.8 km	Water Quality Objectives (WQO)
	Tsin Yue Wan	SR15c	9.0 km	5.4 km	4.5 km	1.6 km	Water Quality Objectives (WQO)
Seawater Intakes	Black Point Power Station	SR4	> 10 km	> 10 km	> 10 km	< 1 km	· Temperature between 17-32 °C · SS elevations less than 700 mg L^-1
	Castle Peak Power Station	SR7a	> 10 km	> 10 km	> 10 km	4.1 km	· Temperature between 17-32 °C · SS elevations less than 700 mg L^-1
	Tuen Mun Area 38	SR7b	>10 km	> 10 km	> 10 km	5.8 km	Water Quality Objectives (WQO)
	Tuen Mun Flushing Water	SR 7h	>10 km	> 10 km	> 10 km	9.67 km	WSD Water Quality Standards
	Airport	SR7c SR7d SR7e SR7f	>10 km	> 10 km > 10 km 8.1 km 8.1 km	> 10 km > 10 km 8.1 km 8.1 km	6.4 km 7.7 km 5.1 km 6.1 km	Water Quality Objectives (WQO)
	Pumping Station at Tai Kwai Wan	SR7g	>10 km	> 10 km	> 10 km	> 10 km	Water Quality Objectives (WQO)
Notes: 1. Distances are approximate and will depend on the final design of the alignment of the submarine utilities which will be determined during the detailed design stage. 2. Refer to next two tables for the details of the WQO criteria for SS and DO at each station.

Table 66.8 Ambient Level and WQO Allowable Increase in SS at Sensitive Receivers (SRs) around Proposed LNG Terminal at South Soko and Submarine Pipeline from South Soko to Black Point

Sensitive Receiver	Name	ID		Respective EPD Monitoring Station	Relevant Depth	Suspended Solids (mg L^-1)
						Annual				Dry			Wet
						Ambient Level		WQO Allowable Increase		Ambient Level	WQO Allowable Increase		Ambient Level		WQO Allowable Increase
*Fisheries and Marine Ecological Sensitive Receivers*
*Fisheries Resources*
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau		SR24, 27	SM20	Depth-averaged	22.2	6.7		23			6.9	18.3	5.5
	Fisheries Spawning Ground in North Lantau		SR8	NM5	Depth-averaged	23.2	7		27.2			8.2	18.6	5.6
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau		SR6e	NM5	Depth-averaged	23.2	7		27.2			8.2	18.6	5.6
	Northeast Airport		SR7d	NM3	Depth-averaged	17	5.1		15.6			4.7	17.4	5.2
Fish Fry Habitat	Pak Tso Wan		SR16b	SM20	Depth-averaged	22.2	6.7		23			6.9	18.3	5.5
Fish Culture Zone	Cheung Sha Wan		SR38	NM3	Depth-averaged	17	N/A		15.6			N/A	17.4	N/A
	Ma Wan		SR40a, 40b	SM13	Depth-averaged	15.7	N/A		15.8			N/A	13.1	N/A
Oyster Production Farm	Pak Nai		SR2	DM4	Surface ⁴	21.7	6.5		23.6			7.1	12	3.6
*Marine Ecological Resources*
Seagrass Beds	Pak Nai	SR2		DM4	Surface ⁴	21.7	6.5			23.6	7.1		12		3.6
	Tung Chung Bay	SR39		NM8	Surface ⁴	17.5	5.3			21.5	6.5		12		3.6
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR6a-d		NM5	Depth-averaged	23.2	7			27.2	8.2		18.6		5.6
	Potential Southwest Lantau	SR19a-c		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
Intertidal Mudflats	Pak Nai	SR1		DM4	Surface ⁴	21.7	6.5			23.6	7.1		12		3.6
	Yi O	SR14		NM8	Surface ⁴	17.5	5.3			21.5	6.5		12		3.6
	Shui Hau Wan	SR33		SM13	Surface ⁴	12	3.6			13	3.9		8.3		2.5
Mangroves	Pak Nai	SR2		DM4	Surface ⁴	21.7	6.5			23.6	7.1		12		3.6
	Tung Chung Bay	SR39		NM8	Surface ⁴	17.5	5.3			21.5	6.5		12		3.6
	Fan Lau Tung Wan	SR15b		SM20	Surface ⁴	14	4.2			15	4.5		10		3
Horseshoe Crab Nursery Grounds	Pak Nai	SR1		DM4	Depth-averaged	32.4	9.7			32.2	9.7		19.9		6
	Sham Wat Wan	SR10		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
	Tai O	SR12		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
	Yi O	SR14		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
	Sha Lo Wan	SR18		NM6	Depth-averaged	20.8	6.2			25.9	7.8		16		4.8
	Tong Fuk Miu Wan	SR33		SM13	Depth-averaged	15.7	4.7			15.8	4.8		13.1		3.9
	Tung Chung Bay	SR39		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11, 11a-b		NM8	Depth-averaged	28.3	8.5			29.7	8.9		21.7		6.5
*Others*
Gazetted Beaches	Butterfly Beach	SR5c		NM5	Depth-averaged	23.2		7		27.2	8.2		18.6		5.6
	Tuen Mun Beaches	SR5d		NM3	Depth-averaged	17		5.1		15.6	4.7		17.4		5.2
	Tong Fuk	SR34		SM13	Depth-averaged	15.7		4.7		15.8	4.8		13.1		3.9
	Upper Cheung Sha Beach	SR35		SM13	Depth-averaged	15.7		4.7		15.8	4.8		13.1		3.9
	Lower Cheung Sha Beach	SR36		SM13	Depth-averaged	15.7		4.7		15.8	4.8		13.1		3.9
	Pui O Wan	SR37		SM13	Depth-averaged	15.7		4.7		15.8	4.8		13.1		3.9
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR5a		NM5	Depth-averaged	23.2		7		27.2	8.2		18.6		5.6
	Lung Kwu Tan	SR5b		NM5	Depth-averaged	23.2		7		27.2	8.2		18.6		5.6
	Fan Lau Sai Wan	SR15a		SM20	Depth-averaged	22.2		6.7		23	6.9		18.3		5.5
	Fan Lau Tung Wan	SR15b		SM20	Depth-averaged	22.2		6.7		23	6.9		18.3		5.5
	Tsin Yue Wan	SR15c		SM20	Depth-averaged	22.2		6.7		23	6.9		18.3		5.5
Seawater Intakes	Tuen Mun Area 38	SR7b		NM3	Bottom	51		15.3		47.4	14.2		32.8		9.8
	Airport	SR7c-f		NM6	Bottom	25.5		7.7		29.6	8.9		29.4		8.8
	Pumping Station at Tai Kwai Wan	SR7g		SM17	Bottom	26		7.8		25	7.5		26.2		7.9
	Tuen Mun WSD ⁵	SR7h		NM3	Bottom	51		N/A		47.4	N/A		32.8		N/A
Notes:
1. Ambient level is calculated as 90^th percentile of the EPD routine monitoring data (1996-2006) at respective EPD station close to the WSRs. 2. Allowable increase is calculated as 30% of the ambient SS levels in accordance with the WQO. 3. This table is applicable for those sensitive receivers which were assessed against the WQO. “N/A” denotes that the WQO is not applicable for the assessment and it should refer to Section 6.2.4 for the specific assessment criterion of SS for the other sensitive receivers. 4. These intertidal sensitive receivers occur at the water surface and are in fact completely unsubmerged for a substantial proportion of the time. Tidal range in Hong Kong is 2.5 m and this is the maximum depth these sensitive receivers would be submerged during the tidal cycle. It is considered that water quality reflecting surface conditions is appropriate for these periodically submerged sensitive receivers. 5. Seawater is abstracted via a box culvert of 1.38 m height situating at the seabed.

Table 66.9 Ambient Level and Allowable Increase in DO at Sensitive Receivers (SRs) around Proposed LNG Terminal at South Soko and Submarine Pipeline from South Soko to Black Point

Sensitive Receiver	Name	ID	Respective EPD Monitoring Station	Relevant Depth	Dissolved Oxygen (mg L^-1)
					Annual		Dry		Wet
					Ambient Level	Allowable Change	Ambient Level	Allowable Change	Ambient Level	Allowable Change
*Fisheries and Marine Ecological Sensitive Receivers*
*Fisheries Resources*
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24, 27	SM20	Depth-averaged	8	-4	8.2	-4.2	7.8	-3.8
	Fisheries Spawning Ground in North Lantau	SR8	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	SR6e	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
	Northeast Airport	SR7d	NM3	Depth-averaged	5.8	-1.8	6.6	-2.6	5.2	-1.2
Fish Fry Habitat	Pak Tso Wan	SR16b	SM20	Depth-averaged	8	-4	8	-4	7.9	-3.9
Fish Culture Zone	Cheung Sha Wan	SR38	SM13	Depth-averaged	8	-3	7.8	-2.8	8.5	-3.5
	Ma Wan	SR40a-b	NM3	Depth-averaged	5.8	-0.8	6.6	-1.6	5.2	-0.2
Oyster Production Farm	Pak Nai	SR2	SM20	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
*Marine Ecological Resources*
Seagrass Beds	Pak Nai	SR2	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
	Tung Chung Bay	SR39	NM8	Surface ⁵	7.9	-3.9	8	-4	7.9	-3.9
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR6a-d	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
	Potential Southwest Lantau	SR19a-c	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
Intertidal Mudflats	Pak Nai	SR1	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
	Yi O	SR14	NM8	Surface ⁵	7.9	-3.9	8.0	-4.0	7.9	-5.1
	Shui Hau Wan	SR33	SM13	Surface ⁵	8.4	-4.4	7.8	-3.8	9.1	-5.1
Mangroves	Pak Nai	SR2	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
	Yi O	SR14	NM8	Surface ⁵	7.9	-3.9	8	-4.0	7.9	-3.9
	Shui Hau Wan	SR33	SM13	Surface ⁵	8.4	-4.4	7.8	-3.8	9.1	-5.1
Horseshoe Crab Nursery Grounds	Pak Nai	SR1	DM4	Depth-averaged	7.5	-3.5	7.6	-3.6	7.3	-3.3
	Sham Wat Wan	SR10	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
	Tai O	SR12	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
	Yi O	SR14	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
	Sha Lo Wan	SR18	NM6	Depth-averaged	8.1	-4.1	8.1	-4.1	8.0	-4.0
	Tong Fuk Miu Wan	SR33	SM13	Depth-averaged	8.0	-4.1	7.8	-3.8	8.5	-4.5
	Tung Chung Bay	SR39	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11, 11a-b	NM8	Depth-averaged	7.9	-3.9	8.0	-4.0	7.9	-3.9
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	SM20	Depth-averaged	8.0	-4.0	8.0	-4.0	7.9	-3.9
*Water Quality Sensitive Receivers*
*Others*
Gazetted Beaches	Butterfly Beach	SR5c	NM5	Depth-averaged	8.0	-4.0	7.9	-3.9	6.8	-2.8
	Tuen Mun Beaches	SR5d	NM3	Depth-averaged	5.8	-1.8	6.6	-2.6	5.2	-1.2
	Tong Fuk	SR34	SM13	Depth-averaged	8.0	-4.1	7.8	-3.8	8.5	-4.5
	Upper Cheung Sha Beach	SR35	SM13	Depth-averaged	8.0	-4.1	7.8	-3.8	8.5	-4.5
	Lower Cheung Sha Beach	SR36	SM13	Depth-averaged	8.0	-4.1	7.8	-3.8	8.5	-4.5
	Pui O Wan	SR37	SM13	Depth-averaged	8.0	-4.1	7.8	-3.8	8.5	-4.5
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR5a	NM5	Depth-averaged	8.0	-4.0	7.9	-3.9	6.8	-2.8
	Lung Kwu Tan	SR5b	NM5	Depth-averaged	8.0	-4.0	7.9	-3.9	6.8	-2.8
	Fan Lau Sai Wan	SR15a	SM20	Depth-averaged	8.0	-4.0	8.0	-4.0	7.9	-3.9
	Fan Lau Tung Wan	SR15b	SM20	Depth-averaged	8.0	-4.0	8.0	-4.0	7.9	-3.9
	Tsin Yue Wan	SR15c	SM20	Depth-averaged	8.0	-4.0	8.0	-4.0	7.9	-3.9
Seawater Intakes	Black Point Power Station	SR4	DM5	Bottom	7.3	-5.3	7.7	-5.7	6.5	-4.5
	Castle Peak Power Station	SR7a	NM5	Bottom	8.0	-6.0	7.6	-5.6	6.2	-4.2
	Tuen Mun Area 38	SR7b	NM5	Bottom	8.0	-6.0	7.6	-5.6	6.2	-4.2
	Airport	SR7c-f	NM6	Bottom	8.2	-6.2	8.3	-6.3	7.6	-5.6
	Pumping Station at Tai Kwai Wan	SR7g	SM17	Bottom	8.0	-6.0	8.0	-6.0	7.9	-5.9
	Tuen Mun WSD ⁴	SR7h	NM3	Bottom	5.6	3.6	6.7	4.7	4.7	2.7
Notes:
1. Ambient level is calculated as 90^th percentile of the EPD routine monitoring data (1996-2006) at respective EPD station close to the WSRs.
2. For depth-averaged, surface layer and middle layer, allowable change is calculated as WQO criterion of 4 mg L^-1minus the ambient level.
3. For bottom layer, allowable change is calculated as WQO criterion of 2 mg L^-1 minus the ambient level.
4. Tuen Mun WSD intake has a DO criterion of more than 2 mg L^-1. Seawater is abstracted via a box culvert of 1.38 m height situating at the seabed.
5. These intertidal sensitive receivers occur at the water surface and are in fact completely unsubmerged for a substantial proportion of the time. Tidal range in Hong Kong is 2.5 m and this is the maximum depth these sensitive receivers would be submerged during the tidal cycle. It is considered that water quality reflecting surface conditions is appropriate for these periodically submerged sensitive receivers.

Fisheries Resources

The following fisheries resources have been identified as water quality sensitive receivers:

· Commercial Fisheries Spawning Grounds/Nursery Areas;

· Artificial Reef Deployment Sites;

· Fish Culture Zone; and

· Oyster Production.

Brief descriptions of these sensitive receivers are presented below.

Commercial Fisheries Spawning Grounds/Nursery Areas

The waters of South Lantau and Northwest Lantau have been identified as important fisheries spawning/nursery grounds for commercial fisheries in Hong Kong ([25]). A recent study has shown that the marine waters near Pak Tso Wan in South Soko support fish fry and hence this beach has been identified as a sensitive receiver ([26]). Recent findings from ichthyoplankton and fish fry baseline survey undertaken as part of this EIA have indicated that the waters at Pak Tso Wan do not appear to support fish fry abundances that are significantly different to other sites in Hong Kong (see Part 2 – Section 10: Fisheries Impact Assessment for further details).

To date there are no legislated water quality standards for spawning and nursery grounds in Hong Kong. Guideline values have been identified for fisheries and selected marine ecological sensitive receivers as part of the AFCD study, Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment. ⁽³⁾ The AFCD study recommends a maximum SS concentration of 50 mg L^-1. Although a maximum concentration value is recommended, the study acknowledges that site-specific data should be considered on a case-by-case basis and hence the WQOs are adopted in this Study as the assessment criteria for the grounds.

With regard to the water quality modelling, impacts to these and other transitory or mobile sensitive receivers were not plotted as discrete points, rather, an assessment of potential impacts was undertaken through a review of the modelling results and is discussed separately in the Fisheries Impact Assessment (Part 2 - Section 10).

Artificial Reef Deployment Sites

There are two gazetted Artificial Reef Deployment Sites (ARs):

· the Sha Chau and Lung Kwu Chau AR site (situated within the Sha Chau and Lung Kwu Chau Marine Park); and

· the Airport AR site (located at the northeast of the Hong Kong International Airport) (Figure 6.3).

The Sha Chau and Lung Kwu Chau AR site and the Airport AR site are approximately 0.8 km and 8.3 km from proposed pipeline alignment, respectively. The ARs have been deployed to act as a fisheries resource enhancement tool, to encourage growth and development of a variety of marine organisms, and to provide feeding opportunities for the Indo-Pacific Humpback Dolphin (see Part 2 - Section 9: Marine Ecology Assessment).

There is no specific water quality criterion for the AR sites, thus the WQOs were adopted as assessment criteria.

AR sites were treated as discrete assessment points in the model.

Fish Culture Zones

There are two fish culture zones (FCZs), which are Ma Wan North and East and Cheung Sha Wan, located within the North Western waters and the Southern waters, respectively. These FCZs are each over 10 km from the proposed terminal and pipeline. The only Water Quality Objective (WQO) that is specific to FCZs is for dissolved oxygen, which is set at no less than 5 mg L^-1. In addition to dissolved oxygen, there is a general water quality protection guideline for suspended solids (SS), which has been proposed by AFCD.^{^[27]}⁾The guideline requires that the SS levels remain below 50 mg L^-1.

There are two fish culture zones (FCZs), which are Ma Wan North and East and Cheung Sha Wan, located within the North Western waters and the Southern waters, respectively. These FCZs are each over 10 km from the proposed terminal and pipeline. The only Water Quality Objective (WQO) that is specific to FCZs is for dissolved oxygen, which is set at no less than 5 mg L-1. In addition to dissolved oxygen, there is a general water quality protection guideline for suspended solids (SS), which has been proposed by AFCD.[28])The guideline requires that the SS levels remain below 50 mg L-1.

With regard to the water quality modelling, the FCZs were regarded as discrete points for evaluation in the assessment against the above criterion and guideline.

Oyster Production Area

There is an area of oyster production along the coast of Deep Bay in Hong Kong waters. The shallowness of Deep Bay as a result of silt carried down from the Pearl River and typical estuarine conditions within Deep Bay enhances oyster cultivation.

There is no specific water quality criterion for an oyster production farm, thus water quality impacts have been assessed with reference to the WQOs.

The area was regarded as the nearest discrete point to the works site. If no non-compliances are found at the point, it is assumed that there will be no impacts to the area beyond this point.

· Marine Ecological Resources

The following Marine Ecological Resources have been identified as water quality sensitive receivers.

· Marine Park;

· Seagrass Beds, Mangroves, Intertidal Mudflats and Horseshoe Crabs;

· Chinese White Dolphin Protection Zone in Mainland China; and

· Subtidal Hard Bottom Habitat.

Marine Park

The Sha Chau and Lung Kwu Chau Marine Park, designated specifically for the protection of the Indo-Pacific Humpback Dolphin (Sousa chinensis), lies within the study area (Figure 6.3). Water quality impacts are compared to the WQO for SS. For the water quality assessment, discrete points have been plotted at a number of locations along the boundaries of the Marine Park which face the proposed pipeline alignment. A potential Marine Park is located to the southwest of Lantau Island.

Seagrass Beds, Mangroves, Intertidal Mudflats & Horseshoe Crabs

Seagrass beds, mangroves, mudflats and areas where horseshoe crabs are known to breed are identified (Figure 6.3). There are no specific legislative water quality criteria for these habitats and hence the WQO has been adopted. These habitats have been plotted as discrete points for evaluation. Note that SR2 is representative for the habitats at Pak Nai. If no impacts are determined at SR2, it is assumed that the impacts will not occur beyond SR2.

Marine Mammal Habitat

Of the two resident Hong Kong marine mammal species, Chinese White Dolphins (also called Indo-Pacific Humpback dolphins) have been recorded across all waters of the Study Area from Deep Bay to South Lantau, whereas Finless Porpoises are only recorded in the South Lantau part of the Study Area. The baseline conditions and ecological importance evaluated for these two species are elaborated in Part 2 – Section 9: Marine Ecology Assessment.

Given that the marine mammals are mobile within the Study Area, the habitat is not plotted as a discrete point for evaluation; rather it is assessed through the contour plots which show the mixing zones of the water quality assessment parameters.

Chinese White Dolphin Protection Zone in Mainland China

A Chinese White Dolphin Protection Zone is located west of Lantau Island, close to the Hong Kong SAR boundary, in Mainland Chinese waters (Figure 6.3). The closest boundary of the Protection Zone is approximately 8 km from the proposed terminal at South Soko and approximately 0.8 km from the proposed pipeline alignment. The Chinese White Dolphin Protection Zone is identified as a sensitive receiver and has been plotted as discrete points for evaluation in the water quality assessment. Water quality impacts are compared to the WQOs.

Subtidal Hard Bottom Habitat

Dive surveys have been conducted at South Soko and the results showed that hard corals were in low abundance and diversity (see Part 2 – Section 9: Marine Ecology Assessment for further details). The corals recorded during the dive surveys are all common Hong Kong species with the exception of the relatively little known hard coral recorded on the southern coast of the South Soko Island. The habitat has been plotted as a discrete point ([29]) for evaluation in the water quality assessment and specific tolerance criteria relevant to corals have been adopted.

· Other Water Quality Sensitive Receivers

The following additional water quality sensitive receivers have been identified and included in the assessment.

· Bathing Beaches; and

· Seawater Intakes.

Bathing Beaches

There are several gazetted beaches identified and a number of non-gazetted bathing beaches (Figure 6.3). Gazetted beaches include the beaches at Tong Fuk, Cheung Sha and Tuen Mun. Non-gazetted beaches are located at Lung Kwu Tan and around Fan Lau. The closest non-gazetted beach to the pipeline alignment is Fan Lau Sai Wan at a distance of approximately 1 km. The closest gazetted bathing beach is Tong Fuk at a distance of approximately 4.4 km from the water main and power cable. Bathing beaches have been plotted as discrete points for evaluation in the water quality assessment.

Water quality impacts at gazetted and non-gazetted bathing beaches have been determined based on the compliance with the WQOs (Table 6.1).

Seawater Intakes

There are nine seawater intakes identified as potential sensitive receivers, namely those at Black Point Power Station, Castle Peak Power Station, Tuen Mun Area 38, Tuen Mun WSD and the Airport and Tai Kwai Wan pumping station. The intakes are situated submerged in the water near to the seabed.

The intakes have been plotted as discrete points for evaluation in the water quality assessment.

6.4 Potential Sources of Impact

Potential sources of impacts to water quality as a result of the project may occur during both the construction and operation phases.

6.4.1 Construction Phase

The main construction activities associated with the proposed project that have the potential to cause impacts to water quality involve the following:

· Dredging and filling for seawall enhancements for the LNG terminal at South Soko;

· Filling for reclamation at the berths;

· Dredging for the approach channel and turning basin near the terminal for the LNG carrier;

· Dredging and jetting for the installation of the submarine gas pipeline connecting the LNG terminal at South Soko to the power station at Black Point;

· Dredging and jetting for the installation of the submarine water main connecting the LNG terminal at South Soko to Shek Pik Reservoir;

· Jetting for the installation of the submarine cable circuits connecting the LNG terminal at South Soko to the electricity sub station at Shek Pik;

· Piling for the jetty near the terminal for LNG carriers;

· Sewage discharges due to the on-site workforce;

· Site runoff including stockpiling of excavated materials and pollutants entering the receiving waters and/or water drainage system;

· Hydrotest water discharges; and,

· Oil spills due to accidental events.

6.4.2 Operational Phase

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

· Changes to the hydrodynamic regime through the reclamation of the terminal site;

· Maintenance dredging of the approach channel and turning basin for the LNG carrier causing a temporary increase in SS concentrations in the water column;

· Discharge of cooled water from the regasification process resulting in a decrease in temperature and the input of antifoulants into the surrounding waters;

· Storm water run-off from the terminal site;

· Sewage discharges due to the operational workforce;

· Vessel discharges;

· LNG spillage due to accidental events; and

· Fuel spillage due to accidental events.

6.5 Water Quality Impact Assessment Methodology

6.5.1 General Methodology

The methodology employed to assess the above impacts is presented in the Water Quality Method Statement (Annex 6A) and has been based on the information presented in the Project Description (Part 2 - Section 3).

Impacts due to the dispersion of fine sediment in suspension during the construction of the proposed LNG terminal and associated facilities have been assessed using computational modelling. Mitigation measures, as proposed in Section 6.8 such as the use of silt curtain, were assumed to be absent for modelling the worst case scenario.

The simulation of operational impacts on water quality has also been performed by means of computational modelling. The models have been used to simulate the effects of cooled water discharges on temperature and water quality (due to antifoulants).

Full details of the scenarios examined in the modelling works are provided in Annex 6A. As discussed previously, the water quality sensitive receivers as well as the additional water quality modelling output points in the vicinity of the proposed LNG terminal at South Soko Island and the submarine utilities are presented in Figure A2.1.

6.5.2 Uncertainties in the Assessment Methodology

Uncertainties in the assessment of the impacts from suspended sediment plumes should be considered when drawing conclusions from the assessment. In carrying out the assessment, worse case assumptions have been made in order to provide a conservative assessment of environmental impacts. These assumptions are as follows.

· The assessment is based on the peak dredging and filling rates. In reality, these will only occur for short periods of time; and

· The calculations of loss rates of sediment to suspension are based on conservative estimates for the types of plant and methods of working.

The assumptions presented above allow a conservative approach to be applied to the water quality assessment.

The following uncertainties has not included in the modelling assessment:

· Ad hoc navigation of marine traffic;

· Near shore scouring of bottom sediment; and

· Transits of marine barges to and from the site.

It is noted that the above present mechanisms through which minor localised and short term changes in SS levels may occur during construction. Elevations of this type will be picked up and monitored during the water quality monitoring programme for the construction works which is presented in Section 6.10.

6.6 Construction Phase Water Quality Impact Assessment

6.6.1 Suspended Sediment

The potential main impacts to water quality arising from this project during the construction phase relate to disturbances to the seabed and re-suspension of some marine sediment leading to the potential for physio-chemical changes in the water column.

· Assessment of Concurrent Construction Phase Activities

As discussed in the Water Quality Method Statement (Annex 6A), during the construction phases, a number of marine activities have the potential to occur simultaneously. The locations of the marine activities are shown in Figure 6.5 and the indicative drawings for each activity are illustrated in Figures 6.6 – 6.9.

In order to assess the potential cumulative impacts to water quality as a result of activities running concurrently, a total of 13 scenarios have been developed (Table 6.10). It should be noted that of these 13 scenarios, SR4a and SR4b are variations of the same construction activities, i.e., trailing suction hopper dredger versus closed grab dredger.

The selected scenarios represent periods during the construction programme when the maximum number of activities may take place in close proximity at any given time. Such works include those associated with the construction of the LNG terminal at South Soko Island, as well as the installation of the submarine pipeline (including the gas receiving station) and utilities (i.e., water main and power cable). The construction programme and the construction sequence for the marine works is shown in Part 2 - Annex 6A.

Note that the scenarios may not occur in sequential order, for example, Scenario 1 may not necessarily be the first batch of works to be performed whereas it is possible that Scenario 2 will be taken place prior to it. Assessment of each scenario enables the examination of impacts due to the concurrent activities. Whenever the scenarios are compliant with the assessment criteria, the individual activities are considered to be environmentally acceptable. When any non-compliances with the WQO or specific assessment criteria are identified in the assessment, further discussions on the activity(ies) that contribute to the exceedance will be presented. Mitigation measures, if deemed necessary, will also be recommended.

Data were extracted from the modelling results to determine the predicted levels of suspended sediment at each of the sensitive receivers. The maximum and mean elevations of SS at relevant depths for the respective sensitive receivers are presented under each scenario.

The determination of the acceptability of any elevation in SS levels has been based on the WQO or specific tolerance criteria. It should be noted that elevations in the SS level due to concurrent operations have been assessed as the maximum concentrations at water depths over a full 15 day spring-neap tidal cycle in both the dry and wet season, as required by the EIA Study Brief (ESB-126/2005).

In the following text, each scenario shown in Table 6.10 will be discussed in the subsequent paragraphs followed by a discussion of the results for the gas pipeline installation works.

Scenario ID	Tasks	Details of Construction Activities	No. of Plant	Plant Type	Code
Scenario 1	Reclamation Areas	Grab Dredging underneath Seawall at Tung Wan (Area A)	1 no.	Grab Dredger	SS	01
	Reclamation Areas	Grab Dredging underneath Seawall for Western Berth at Sai Wan (Area B)	1 no.	Grab Dredger	SS	02
	Reclamation Areas	Sand filling Seawall Trench and Reclamation for the Western Berth	1 no.	Pelican Barge	SS	32
Scenario 2	Submarine Water Main	Grab Dredging at South Soko Shore Approach	1 no.	Grab Dredger	SS	06
	Submarine Water Main	Grab Dredging at Shek Pik Shore Approach	1 no.	Grab Dredger	SS	07
	Submarine Water Main	Grab Dredging Waterway Crossing Sand Borrow Area & Marine Navigation Channel	1 no.	Grab Dredger	SS	08
Scenario 3	Submarine Water Main	Post Trenching Jetting near South Soko	1 no.	Jetting Machine	SS	09
	Submarine Water Main	Post Trenching Jetting near Shek Pik	1 no.	Jetting Machine	SS	10
Scenario 4a	Jetty Box	Grab Dredging at Jetty Box	1 no.	Grab Dredger	SS	03
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area C	1 no.	Grab Dredger	SS	04a
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area D	1 no.	Grab Dredger	SS	05
Scenario 4b	Jetty Box	Grab Dredging at Jetty Box	1 no.	Grab Dredger	SS	03
	Approach Channel and Turning Basin	TSHD Dredging at Approach Channel & TB at Area C	1 no.	TSHD	SS	04b
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area D	1 no.	Grab Dredger	SS	05
Scenario 5	Submarine Cable Circuit	Submarine Cable Installation by Direct Burying (Jetting)	1 no.	Jetting Machine	SS	14
	Submarine Intake	Grab Dredging under intake	1 no.	Grab Dredger	SS	15
	Cooled Water Outfall	Grab Dredging under outfall	1 no.	Grab Dredger	SS	28
Scenario 6	Gas Receiving Station	Grab Dredging at GRS	1 no.	Grab Dredger	SS	29
	Gas Receiving Station	Grab Dredging at GRS	1 no.	Grab Dredger	SS	30
	Gas Receiving Station	Sand filling Seawall Trench and Reclamation at GRS	1 no.	Pelican Barge	SS	31
Scenario 7	Submarine Gas Pipeline	Grab Dredging at South Soko Shore Approach (KP 0 - KP 1)	1 no.	Grab Dredger	SS	21
Scenario 8	Submarine Gas Pipeline	TSHD Dredging from Fan Lau Crossing to West Lantau (KP 1 - KP 24.5)	1 no.	TSHD	SS	32
Scenario 9	Submarine Gas Pipeline	Grab Dredging from Northwest Lantau to Urmston Road Crossing (KP 24.5 – KP 31)	3 nos.	Grab Dredger	SS	33
Scenario 10	Submarine Gas Pipeline	Grab Dredging across Urmston Road Crossing (KP31– KP 33.5)	1 no.	Grab Dredger	SS	34
Scenario 11	Submarine Gas Pipeline	Grab Dredging at West of Black Point (KP33.5 – KP 37)	3 nos.	Grab Dredger	SS	19
Scenario 12	Submarine Gas Pipeline	Grab Dredging at West of Black Point (KP 37 – KP 37.803)	1 no.	Grab Dredger	SS	35
Scenario 13	Submarine Gas Pipeline	Grab Dredging at Black Point Shore Approach (KP37.803 - KP38.303)	1 no.	Grab Dredger	SS	16

Table 66.11 Predicted SS Elevation (mg L^-1) in Scenario 1

Sensitive Receiver	Name	ID	Relevant Water Depth ^(a)	Allowable Elevation		Predicted SS Elevation (mg L^-1)
				Dry	Wet	Dry	Wet	Dry	Wet		Dry	Wet
				Dry	Wet	Max	Max	Mean	Mean		90%-tile	90%-tile
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	a	8.9	6.5	0.1	0.1	0.0	0.0		0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11a	a	8.9	6.5	0.1	0.1	0.0	0.0		0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11b	a	8.9	6.5	0.1	0.1	0.0	0.0		0.1	0.1
Horseshoe Crab Nursery Grounds	Tai O	SR12	a	8.9	6.5	0.0	0.0	0.0	0.0		0.0	0.0
Intertidal Mudflats	Yi O	SR14	s	6.5	3.6	0.0	0.0	0.0	0.0		0.0	0.0
Horseshoe Crab Nursery Grounds	Yi O	SR14	a	8.9	6.5	0.0	0.1	0.0	0.0		0.0	0.0
Non-gazetted Beaches	Fan Lau Sai Wan	SR15a	a	6.9	5.5	0.0	0.1	0.0	0.0		0.0	0.0
Mangroves	Fan Lau Tung Wan	SR15b	s	4.5	3	0.0	0.0	0.0	0.0		0.0	0.0
Non-gazetted Beaches	Fan Lau Tung Wan	SR15b	a	6.9	5.5	0.0	0.1	0.0	0.0		0.0	0.0
Non-gazetted Beaches	Tsin Yue Wan	SR15c	a	6.9	5.5	0.0	0.0	0.0	0.0		0.0	0.0
Fish Fry Habitat	Pak Tso Wan	SR16b	a	6.9	5.5	22.9 ^(c)	36.8 ^(c)	5.0	8.9		11.0	19.1
Horseshoe Crab Nursery Grounds	Sha Lo Wan	SR18	a	7.8	4.8	0.0	0.0	0.0	0.0		0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	a	6.9	5.5	0.6	0.4	0.1	0.1		0.2	0.1
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR27	a	6.9	5.5	2.5	2.6	0.3	0.5		0.6	1.4
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	a	10 ^(b)	10 ^(b)	2.9	1.6	0.7	0.3		1.5	0.6
Intertidal Mudflats	Shui Hau Wan	SR33	s	3.9	2.5	0.0	0.0	0.0	0.0		0.0	0.0
Horseshoe Crab Nursery Grounds	Tong Fuk Miu Wan	SR33	a	4.8	3.9	0.0	0.0	0.0	0.0		0.0	0.0
Gazetted Beaches	Tong Fuk	SR34	a	4.8	3.9	0.0	0.0	0.0	0.0		0.0	0.0
Gazetted Beaches	Upper Cheung Sha Beach	SR35	a	4.8	3.9	0.0	0.0	0.0	0.0		0.0	0.0
Seagrass Beds/Mangroves	Tung Chung Bay	SR39	s	6.5	3.6	0.0	0.0	0.0	0.0		0.0	0.0
Horseshoe Crab Nursery Grounds	Tung Chung Bay	SR39	a	8.9	6.5	0.0	0.0	0.0	0.0		0.0	0.0
Notes: a. s = surface, m = middle, b = bottom, a = depth-averaged b. The tolerance assessment criterion of 10 mg L^-1 was adopted for the coral. c. Shaded area indicates non-compliance with the assessment criterion.										8.9		6.5

Sensitive Receiver	Name	ID	Relevant Water Depth ^(a)	Allowable Elevation	Predicted SS Elevation (mg L^-1)
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11a	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11b	a	8.9	6.5	0.0	0.1	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tai O	SR12	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Intertidal Mudflats	Yi O	SR14	s	6.5	3.6	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Yi O	SR14	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Sai Wan	SR15a	a	6.9	5.5	0.1	0.1	0.0	0.0	0.0	0.0
Mangroves	Fan Lau Tung Wan	SR15b	s	4.5	3	0.1	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Tung Wan	SR15b	a	6.9	5.5	0.2	0.1	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Tsin Yue Wan	SR15c	a	6.9	5.5	0.1	0.1	0.0	0.0	0.1	0.0
Fish Fry Habitat	Pak Tso Wan	SR16b	a	6.9	5.5	16.2 ^(c)	15.5 ^(c)	1.6	3.1	4.4	7.8 ^(c)
Horseshoe Crab Nursery Grounds	Sha Lo Wan	SR18	a	7.8	4.8	0.0	0.0	0.0	0.0	0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	a	6.9	5.5	2.5	1.1	0.1	0.1	0.2	0.2
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR27	a	6.9	5.5	0.8	0.4	0.0	0.0	0.1	0.1
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	a	10 ^(b)	10 ^(b)	0.2	0.2	0.0	0.0	0.1	0.0
Intertidal Mudflats	Shui Hau Wan	SR33	s	3.9	2.5	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tong Fuk Miu Wan	SR33	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Tong Fuk	SR34	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Upper Cheung Sha Beach	SR35	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Seagrass Beds/Mangroves	Tung Chung Bay	SR39	s	6.5	3.6	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tung Chung Bay	SR39	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Notes: 1. s = surface, m = middle, b = bottom, a = depth-averaged 2. The tolerance assessment criterion of 10 mg L^-1 was adopted for the coral. 3. Shaded area indicates non-compliance with the assessment criterion.

Sensitive Receiver	Name	ID	Relevant Water Depth ^(a)	Allowable Elevation	Predicted SS Elevation (mg L^-1)
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11a	a	8.9	6.5	0.1	0.0	0.0	0.0	0.1	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11b	a	8.9	6.5	0.3	0.1	0.0	0.0	0.1	0.0
Horseshoe Crab Nursery Grounds	Tai O	SR12	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Intertidal Mudflats	Yi O	SR14	s	6.5	3.6	0.1	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Yi O	SR14	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Sai Wan	SR15a	a	6.9	5.5	0.1	0.0	0.0	0.0	0.1	0.0
Mangroves	Fan Lau Tung Wan	SR15b	s	4.5	3	1.6	0.0	0.1	0.0	0.2	0.0
Non-gazetted Beaches	Fan Lau Tung Wan	SR15b	a	6.9	5.5	2.3	0.1	0.1	0.0	0.3	0.0
Non-gazetted Beaches	Tsin Yue Wan	SR15c	a	6.9	5.5	0.2	0.0	0.0	0.0	0.1	0.0
Fish Fry Habitat	Pak Tso Wan	SR16b	a	6.9	5.5	36.1 ^(c)	57.4 ^(c)	0.7	1.2	1.4	0.5
Horseshoe Crab Nursery Grounds	Sha Lo Wan	SR18	a	7.8	4.8	0.0	0.0	0.0	0.0	0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	a	6.9	5.5	0.2	0.1	0.0	0.0	0.1	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR27	a	6.9	5.5	2.5	2.6	0.1	0.1	0.2	0.1
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	a	10 ^(b)	10 ^(b)	3.7	2.3	0.1	0.0	0.3	0.1
Intertidal Mudflats	Shui Hau Wan	SR33	s	3.9	2.5	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tong Fuk Miu Wan	SR33	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Tong Fuk	SR34	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Upper Cheung Sha Beach	SR35	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Seagrass Beds/Mangroves	Tung Chung Bay	SR39	s	6.5	3.6	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tung Chung Bay	SR39	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Notes: a. s = surface, m = middle, b = bottom, a = depth-averaged b. The tolerance assessment criterion of 10 mg L^-1 was adopted for the coral. c. Shaded area indicates non-compliance with the assessment criterion.

T~~able~~ 6~~.14 Predicted SS Elevation (mg L^-1) in Scenario 4a~~

Sensitive Receiver	Name	ID	Relevant Water Depth ^(a)	Allowable Elevation		Predicted SS Elevation (mg L^-1)
				Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet
				Dry	Wet	Max	Max	Mean	Mean	90%-tile	90%-tile
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11a	a	8.9	6.5	0.1	0.0	0.0	0.0	0.1	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11b	a	8.9	6.5	0.1	0.0	0.0	0.0	0.1	0.0
Horseshoe Crab Nursery Grounds	Tai O	SR12	a	8.9	6.5	0.1	0.1	0.0	0.0	0.0	0.0
Intertidal Mudflats	Yi O	SR14	s	6.5	3.6	0.1	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Yi O	SR14	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Sai Wan	SR15a	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Mangroves	Fan Lau Tung Wan	SR15b	s	4.5	3	0.0	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Tung Wan	SR15b	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Tsin Yue Wan	SR15c	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Fish Fry Habitat	Pak Tso Wan	SR16b	a	6.9	5.5	0.3	0.2	0.1	0.0	0.1	0.1
Horseshoe Crab Nursery Grounds	Sha Lo Wan	SR18	a	7.8	4.8	0.1	0.0	0.0	0.0	0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	a	6.9	5.5	0.2	0.1	0.0	0.0	0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR27	a	6.9	5.5	0.2	0.2	0.0	0.0	0.1	0.1
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	a	10 ^(b)	10 ^(b)	15.5 ^{4, 5}	10.0	5.0	3.7	8.3	6.0
Intertidal Mudflats	Shui Hau Wan	SR33	s	3.9	2.5	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tong Fuk Miu Wan	SR33	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Tong Fuk	SR34	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Upper Cheung Sha Beach	SR35	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Seagrass Beds/Mangroves	Tung Chung Bay	SR39	s	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tung Chung Bay	SR39	a	8.9	6.5	0.0	0.0	0.0	0.0	0.0	0.0
Notes: · s = surface, m = middle, b = bottom, a = depth-averaged · The tolerance assessment criterion of 10 mg L^-1 was adopted for the coral. · Shaded area indicates non-compliance with the assessment criterion. · Contribution of each individual activities are 24% from grab dredging at jetty box, 29% from grab dredging at approach channel and turning basin (area C), 46% from grab dredging at approach channel and turning basin (area D).

Table 66.15 Predicted SS Elevation (mg L^-1) in Scenario 4b

Sensitive Receiver	Name	ID	Relevant Water Depth ^(a)	Allowable Elevation		Predicted SS Elevation (mg L^-1)
				Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet
				Dry	Wet	Max	Max	Mean	Mean	90%-tile	90%-tile
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11a	a	8.9	6.5	0.1	0.0	0.0	0.0	0.1	0.0
Protection Zone	Chinese White Dolphin Protection Zone in Mainland Waters	SR11b	a	8.9	6.5	0.2	0.1	0.1	0.0	0.1	0.0
Horseshoe Crab Nursery Grounds	Tai O	SR12	a	8.9	6.5	0.1	0.1	0.0	0.0	0.0	0.0
Intertidal Mudflats	Yi O	SR14	s	6.5	3.6	0.1	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Yi O	SR14	a	8.9	6.5	0.1	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Sai Wan	SR15a	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Mangroves	Fan Lau Tung Wan	SR15b	s	4.5	3	0.0	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Fan Lau Tung Wan	SR15b	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Non-gazetted Beaches	Tsin Yue Wan	SR15c	a	6.9	5.5	0.0	0.0	0.0	0.0	0.0	0.0
Fish Fry Habitat	Pak Tso Wan	SR16b	a	6.9	5.5	0.2	0.3	0.1	0.0	0.2	0.1
Horseshoe Crab Nursery Grounds	Sha Lo Wan	SR18	a	7.8	4.8	0.0	0.0	0.0	0.0	0.0	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR24	a	6.9	5.5	0.2	0.1	0.0	0.0	0.1	0.0
Spawning/Nursery Grounds	Fisheries Spawning/Nursery Grounds in South Lantau	SR27	a	6.9	5.5	0.2	0.3	0.0	0.0	0.1	0.1
Subtidal Hard Bottom Habitat (coral)	Southern Side of South Soko	SR31	a	10 ^(b)	10 ^(b)	12.1 ^{(c), (d)}	10.5 ^{(c), (e)}	2.9	2.5	5.6	4.3
Intertidal Mudflats	Shui Hau Wan	SR33	s	3.9	2.5	0.0	0.0	0.0	0.0	0.0	0.0
Horseshoe Crab Nursery Grounds	Tong Fuk Miu Wan	SR33	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Gazetted Beaches	Tong Fuk	SR34	a	4.8	3.9	0.0	0.0	0.0	0.0	0.0	0.0
Notes: a. s = surface, m = middle, b = bottom, a = depth-averaged b. The tolerance assessment criterion of 10 mg L^-1 was adopted for the coral. c. Shaded area indicates non-compliance with the assessment criterion. d. Contribution of each individual activities are 31% from grab dredging at jetty box, 10% from grab dredging at approach channel and turning basin (area C), 59% from TSHD dredging at approach channel and turning basin (area D). e. Contribution of each individual activities are 16% from grab dredging at jetty box, 46% from TSHD dredging at approach channel and turning basin (area C), 37% from grab dredging at approach channel and turning basin (area D).

6.1 Water Quality Assessment

6.1 IntroductionIntroduction

6.2 Legislative Requirements and Assessment Criteria

6.2.1 Water Pollution Control Ordinance

6.2.2 Technical Memorandum Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters

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

6.2.4 Suspended Solids Impacts

WQO for SS in Deep Bay Water Control Zone

WQO for SS North Western Water Control Zone

WQO for SS Southern Water Control Zone

SS Criterion for Seawater Intakes

SS Criterion for Fish Culture Zones

· SS Criterion for Subtidal Hard Bottom Habitat

6.2.5 Sediment Quality

6.2.6 Other Assessment Criteria

Sediment Deposition

Dissolved Oxygen

Dissolved Metals and Organic Compounds

Residual Chlorine

6.3 Baseline Conditions and Water Quality Sensitive Receivers

6.3.1 Hydrodynamics

Deep Bay Water Control Zone

North Western Water Control Zone

Southern Water Control Zone

6.3.2 Water Quality

Deep Bay Water Control Zone

North Western Water Control Zone

Southern Water Control Zone

6.3.3 Water Quality in the Marine Park

6.3.4 Sediment Quality

EPD Sediment Quality Monitoring

Ground Investigation Works ([22])

6.3.5 Water Quality Sensitive Receivers

Fisheries Resources

Commercial Fisheries Spawning Grounds/Nursery Areas

Artificial Reef Deployment Sites

Fish Culture Zones

With regard to the water quality modelling, the FCZs were regarded as discrete points for evaluation in the assessment against the above criterion and guideline.

Oyster Production Area

· Marine Ecological Resources

· Other Water Quality Sensitive Receivers

6.4 Potential Sources of Impact

6.4.1 Construction Phase

6.4.2 Operational Phase

6.5 Water Quality Impact Assessment Methodology

6.5.1 General Methodology

6.5.2 Uncertainties in the Assessment Methodology

6.6 Construction Phase Water Quality Impact Assessment

6.6.1 Suspended Sediment

· Assessment of Concurrent Construction Phase Activities