Normal Template

Table 6.1 Water Quality Objectives Applicable to the Study

Water Quality Objective	Deep Bay WCZ	North Western 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)
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)
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)
d) There should be no recognisable sewage-derived debris.	Whole zone	Whole zone (including North Western 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)
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)
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
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
D. 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
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	-
E. 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
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
F. 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)
G. 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)
H. 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)
I. 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)
J. 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)
b) 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
c) 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	-
d) 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)
K. 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))
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
L. 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))
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
M. 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)
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)
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 also 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 Black Point will be required to comply with Table 8 of the TM - Standards for effluents discharged into the coastal waters of Deep Bay Water Control Zone.

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 zone 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 Solid Impacts

The Water Quality Objective (WQO) for suspended solids in marine waters of 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

Analysis of EPD routine water quality 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 the EPD monitoring stations that are in the proximity of the proposed works (Figure 6.2).

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 andNM6 have been analysed to determine the allowable increase at the sensitive receivers close to LNG Terminal and Associated Facilities.

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 reasonable to adopt on 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 and the Airport intakes ([1]) and hence the WQOs were 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 WSD seawater intakes has been assessed against these standards, in addition to the WQOs.

Table 6.2 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 AFCD ([2]). The guideline requires the maximum SS levels remain below 50 mg L^-1. This criterion has been adopted in previous approved EIA Reports ([3]) ([4]).

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

Impacts to artificial reefs (ARs) have been assessed with regard to sediment deposition. The assessment criterion of 200 g m^-2 day^-1, has been used in approved EIA Reports ([5]) and has been adopted here.

Dissolved Oxygen

The release of sediment into the water column or the effluent discharge due to the Project may consume the dissolved oxygen (DO) in the receiving water. The 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 for the period 1996 to 2006.

The DO assessment criterion, for each sensitive receiver is discussed in Section 6.3.5, Part 3.

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 proposed to make reference to the relevant UK water quality standards ([6]). This approach has been adopted in approved EIA Reports, i.e., EIA for Decommissioning of Cheoy Lee Shipyard at Penny’s Bay ([7]), EIA for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit ([8]) and EIA for Wanchai Development Phase II ([9]).

Water sampling was conducted for dissolved metals and organic compounds for the assessment. The results are presented in Annex 6D, Part 3, which showed that the concentrations of the dissolved metals in the marine water column at all sampling stations are below the reporting limits, with the exception of copper and arsenic. This means that the ambient concentrations of these dissolved metals are very low. For copper, the mean concentration has been calculated for each WCZ. Table 6.3 shows the assessment criteria and the respective allowable increases in dissolved metal concentrations.

There are no existing legislative standards or guidelines for total PCBs, total PAHs and TBT and hence reference has been made to the USEPA water quality criteria ([10]), Australian water quality guidelines ([11]), and international literature ([12]) , 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 ,} as shown in Table 6.3.

Similarly, there are no legislative standards or guidelines in Hong Kong for chlorinated pesticides and the assessment criteria are in accordance with the USEPA water quality criteria.

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	1.8	23.2
Cadmium	2.5	0.1	2.4
Chromium	15.0	0.5	14.5
Copper	5.0	0.9	4.1
Lead	25.0	0.5	24.5
Mercury	0.3	0.1	0.2
Nickel	30.0	1.4	28.6
Silver	2.3	0.5	1.8
Zinc	40.0	6.2	33.8
Total PCBs	0.03 ^b	-	-
Total PAHs	3.0 ^b	-	-
TBT	0.1 ^b	-	-
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.

Residual Chorine

As discussed in the Project Description (Section 3, Part 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. 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 modelling of chlorine dispersion. This is also the criterion adopted in the previously approved EIA Report for the 1,800 MW Gas-fired Power Station at Lamma Extension ([13]).

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 Delta 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.

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 the 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 Sha Chau have been predicted in previous studies to reach up to 2.0 ms^-1 ([14]).

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 ([15]). 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 ([16]).

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 (March). This dataset provides Hong Kong’s most comprehensive long term water quality monitoring data and allows 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 are exhibiting 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 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 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 from 1996 to 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, especially 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. Of these monitoring stations, NM5 recorded the highest geometric mean of E. coli, 520 cfu 100mL^-1.

6.3.3 Water Quality of Marine Parks

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

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

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

Water Quality Parameter	Deep Bay WCZ		North Western WCZ
	DM4	DM5	NM5	NM6
Temperature (ºC)	23.9	23.6	23.4	23.5
	(14.4 - 32.8)	(14.4 - 31.1)	(15.5 - 30.3)	(15.1 - 29.8)

pH	7.9	7.9	8.0	8.1
	(6.3 - 9.0)	(6.2 - 8.7)	(7.3 - 8.7)	(6.9 - 8.5)

Dissolved Oxygen (mg L^-1) Depth-averaged	6.0	5.9	5.9	6.4
	(0.6 - 10.2)	(2.6 - 10.0)	(2.3 - 9.2)	(3.3 - 11.8)

Dissolved Oxygen (mg L^-1) Bottom	6.1	5.7	5.5	6.3
	(2.9 - 10.2)	(2.6 - 10.0)	(2.3 - 8.8)	(3.3 - 11.8)

Dissolved Oxygen (% sat.) Depth-averaged	82.2	81.2	80.4	87.2
	(8.8 - 144.9)	(37.7 - 136.0)	(32.7 - 130.0)	(47.1 - 170.2)

Dissolved Oxygen (% sat.) Bottom	82.5	79.1	76.1	86.5
	(40.1 - 144.9)	(37.7 - 122.1)	(32.7 - 110.3)	(47.1 - 167.4)

5-day Biochemical Oxygen Demand (mg L^-1)	1.1	0.9	0.8	0.9
	(<0.1 - 3.7)	(<0.1 - 4.9)	(<0.1 - 4.1)	(<0.1 - 4.9)

Suspended Solids (mg L^-1)	14.3	11.1	12.3	9.6
	(2.4 - 66.0)	(1.1 - 62.0)	(1.6 - 81.0)	(0.9 - 48.0)

Total Inorganic Nitrogen (mg L^-1)	1.02	0.67	0.56	0.51
	(0.13 - 2.77)	(0.14 - 2.46)	(0.03 - 2.30)	(0.01 - 1.74)

Unionised Ammonia (mg L^-1)	0.012	0.007	0.006	0.005
	(0.000 - 0.050)	(0.000 - 0.028)	(0.000 - 0.027)	(0.000 - 0.027)

Chlorophyll-a (microgram L^-1)	3.2	2.3	2.5	3.4
	(<0.2 - 63.0)	(<0.2 - 49.0)	(<0.2 - 28.0)	(<0.2 - 44.0)

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

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 ([17])

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

Mercury (mg kg^-1)	0.12	0.07	0.08	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)
Nickel (mg kg^-1)	28	19	18	18	40	40
Nickel (mg kg^-1)	(14 - 37)	(7 - 31)	(13 - 30)	(9 - 28)
Silver (mg kg^-1)	0.5	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)
Zinc (mg kg^-1)	145	96	96	74	200	270
Zinc (mg kg^-1)	(69 - 230)	(36 - 180)	(67 - 110)	(34 - 120)
Total PCBs (µg kg^-1)	18	18	18	18	23	180
Total PCBs (µg kg^-1)	(18 - 18)	(18 - 18)	(18 - 18)	(18 - 18)
Low Molecular Wt PAHs (µg kg^-1)	92	91	92	90	550	3,160
Low Molecular Wt PAHs (µg kg^-1)	(90 - 96)	(90 - 94)	(90 - 99)	(90 - 94)
High Molecular Wt PAHs (µg kg^-1)	83	60	59	29	1,700	9,600
High Molecular Wt PAHs (µg kg^-1)	(29 - 151)	(16 - 254)	(21 - 139)	(16 - 84)
Notes: 1. Data presented are arithmetic mean and data presented in bracket indicate 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 6.7 Shortest Distance to Water Quality Sensitive Receivers (SRs) around Proposed LNG Terminal at Black Point

Sensitive Receiver	Name	ID	Shortest Distance to the LNG terminal	Assessment Criteria
*Fisheries and Marine Ecological Sensitive Receivers*
*Fisheries Resources*
Spawning/ Nursery Grounds	Fisheries Spawning Ground in North Lantau	SR8	2.6 km	· Water Quality Objectives (WQO)
		SR8a	6.3 km	· Water Quality Objectives (WQO)
		SR8b	8.9 km	· Water Quality Objectives (WQO)
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	SR6e	6 km	· Water Quality Objectives (WQO) · Deposition Rate below 200 mg L^-1
	Airport	SR7d	>10 km	· Water Quality Objectives (WQO) · Deposition Rate below 200 mg L^-1
Fish Culture Zone	Ma Wan	SR40a-b	>10 km	· Water Quality Objectives (WQO)
Oyster Bed	Lau Fau Shan	SR2c	9.9 km	· Water Quality Objectives (WQO)
*Marine Ecological Resources*
Seagrass Beds	Pak Nai	SR2	6.25 km	· Water Quality Objectives (WQO)
	Ngau Hom Shek	SR2a	7.5 km	· Water Quality Objectives (WQO)
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR6a	2.75 km	· Water Quality Objectives (WQO)
		SR6b	8.1 km	· Water Quality Objectives (WQO)
		SR6c	1.6 km	· Water Quality Objectives (WQO)
		SR6d	6.75 km	· Water Quality Objectives (WQO)
Intertidal Mudflats	Pak Nai	SR1	2.6 km	· Water Quality Objectives (WQO)
Mangroves	Pak Nai	SR2	6.25 km	· Water Quality Objectives (WQO)
	Ngau Hom Shek	SR2b	8.3 km	· Water Quality Objectives (WQO)
Horseshoe Crab Nursery Grounds	Pak Nai	SR1	2.6 km	· Water Quality Objectives (WQO)
	Between Ngau Hom Shek and Pak Nai	SR2a	7.5 km	· Water Quality Objectives (WQO)
	Sham Wat Wan	SR10	> 10 km	· Water Quality Objectives (WQO)
	Sha Lo Wan	SR18	> 10 km	· Water Quality Objectives (WQO)
	Tung Chung Bay	SR39	> 10 km	· Water Quality Objectives (WQO)
*Water Quality Sensitive Receivers*
Gazetted Beaches	Butterfly Beach	SR5c	6.6 km	· Water Quality Objectives (WQO)
Gazetted Beaches	Tuen Mun Beaches	SR5d	9.4 km	· Water Quality Objectives (WQO)
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR5a	1.5 km	· Water Quality Objectives (WQO)
Non-gazetted Beaches	Lung Kwu Tan	SR5b	2.7 km	· Water Quality Objectives (WQO)
Secondary Recreation Subzone	Deep Bay WCZ	SR4	Immediate vicinity	· Water Quality Objectives (WQO)
	NW WCZ	SR5b	2.7 km	· Water Quality Objectives (WQO)
		SR5c/SR7h	>10 km	· Water Quality Objectives (WQO)
Seawater Intakes	Black Point Power Station	SR4	Immediate vicinity	· Water Quality Objectives (WQO) · Temperature between 17-32 °C · SS elevations less than 700 mg L^-1
	Castle Peak Power Station	SR7a	3.25 km	· Water Quality Objectives (WQO) · Temperature between 17-32 °C · SS elevations less than 700 mg L^-1
	Tuen Mun Area 38	SR7b	5.2 km	· Water Quality Objectives (WQO)
	Airport	SR7c SR7d SR7e SR7f	> 10 km > 10 km > 10 km > 10 km	· Water Quality Objectives (WQO)
	Tuen Mun WSD	SR7h	> 10 km	· WSD Water Quality Criteria
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 6.8 Ambient Level and Allowable Increase in SS at Sensitive Receivers (SRs) around Proposed LNG Terminal at Black Point

Sensitive Receiver	Name		ID		Respective EPD Monitoring Station			Relevant Depth	Suspended Solids (mg L^-1)
									Annual			Dry (Nov to Mar)				Wet (Apr to Oct)
									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 Ground in North Lantau		SR8	NM5		Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
				SR8a	NM5		Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
				SR8b	NM5		Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
Artificial Reef Deployment Area		Sha Chau and Lung Kwu Chau		SR6e	NM5		Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
		Airport		SR7d	NM3		Depth-averaged		17	5.1	15.6		4.7		17.4		5.2
Fish Culture Zone		Ma Wan		SR40a-b	NM3		Depth-averaged		17	5.1	15.6		4.7		17.4		5.2
Oyster Production		Lau Fau Shan		SR2c	DM4		Surface ⁵		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
		Ngau Hom Shek		SR2a	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	7.0	27.2		8.2		18.6		5.6
Intertidal Mudflats		Pak Nai		SR1	DM4		Surface ⁴		21.7	6.5	23.6		7.1		12		3.6
Mangroves		Pak Nai		SR2	DM4		Surface ⁴		21.7	6.5	23.6		7.1		12		3.6
		Ngau Hom Shek		SR2b	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
Horseshoe Crab Nursery Grounds		Pak Nai		SR1	DM4		Depth-averaged		32.4	9.7	32.2		9.7		19.9		6.0
		Ngau Hom Shek		SR2a	DM4		Depth-averaged		32.4	9.7	32.2		9.7		19.9		6.0
		Sham Wat Wan		SR10	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		16.0		4.8
		Tung Chung Bay		SR39	NM8		Depth-averaged		28.3	8.5	29.7		8.9		21.7		6.5
*Water Quality Sensitive Receivers*
Gazetted Beaches		Butterfly Beach		SR5c		NM5	Depth-averaged		23.2	7.0	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
Non-gazetted Beaches		Lung Kwu Sheung Tan		SR5a		NM5	Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
		Lung Kwu Tan		SR5b		NM5	Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
Secondary Contact Recreation Subzone		Deep Bay WCZ		SR4		DM5	Depth-averaged		22.6	6.8	32.0		9.6		20.2		6.1
		NW WCZ		SR5b		NM5	Depth-averaged		23.2	7.0	27.2		8.2		18.6		5.6
Seawater Intakes		Tuen Mun Area 38		SR7b		NM3	Bottom		51.0	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
		Tuen Mun WSD		SR7h		NM3	Bottom		51.0	15.3	47.4		14.2		32.8		9.8
Notes:
1. The tolerance criterion of 700 mg L^-1 was adopted for the seawater intakes at Black Point Power Station and Castle Peak Power Station. 2. Ambient level is calculated as 90^th percentile of the EPD routine monitoring data (1996-2006) at respective EPD station close to the WSRs. 3. Allowable increase is calculated as 30% of the ambient SS levels in accordance with the WQO. 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.

Table 6.9 Ambient Level and Allowable Increase in DO at Sensitive Receivers (SRs) around Proposed LNG Terminal at Black Point

Sensitive Receiver	Name	ID	Respective EPD Monitoring Station	Relevant Depth	Dissolved Oxygen (mg L^-1)
					Annual		Dry (Nov to Mar)		Wet (Apr to Oct)
					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 Ground in North Lantau	SR8	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
		SR8a	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
		SR8a	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 Culture Zone	Ma Wan	SR40a-b	NM3	Depth-averaged	5.8	-0.8	6.6	-1.6	5.2	-0.2
Oyster Production Farm	Pak Nai	SR2c	DM4	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
	Ngau Hom Shek	SR2a	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
Intertidal Mudflats	Pak Nai	SR1	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
Mangroves	Pak Nai	SR2	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
	Ngau Hom Shek	SR2b	DM4	Surface ⁵	7.6	-3.6	7.6	-3.6	7.3	-3.3
Horseshoe Crab Nursery Grounds	Pak Nai	SR1	DM4	Depth-averaged	7.5	-3.5	7.6	-3.6	7.3	-3.3
	Ngau Hom Shek	SR2a	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	-4	7.9	-3.9
	Sha Lo Wan	SR18	NM6	Depth-averaged	8.1	-4.1	8.1	-4.1	8	-4
	Tung Chung Bay	SR39	NM8	Depth-averaged	7.9	-3.9	8	-4	7.9	-3.9
*Water Quality Sensitive Receivers*
Gazetted Beaches	Butterfly Beach	SR5c	NM5	Depth-averaged	8	-4	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
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR5a	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
	Lung Kwu Tan	SR5b	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
Secondary Contact Recreation Subzone	Deep Bay WCZ	SR4	DM5	Depth-averaged	7.4	-3.4	7.7	-3.7	6.6	-2.6
	NW WCZ	SR5b	NM5	Depth-averaged	8	-4	7.9	-3.9	6.8	-2.8
Seawater Intakes	Tuen Mun Area 38	SR7b	NM5	Bottom	8	-6	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
	Tuen Mun WSD ⁷	SR7h	NM3	Bottom	6.1	-4.1	6.5	-4.5	5.8	-3.8
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, with the exception for the Fish Culture Zone.
3. For Fish Culture Zone, the WQO criterion of not less than 5 mg L^-1 was adopted.
4. For bottom layer, allowable change is calculated as WQO criterion of 2 mg L^-1 minus the ambient level.
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.
6. There is no DO criterion for Black Point Power Station, Castle Peak Power Station intakes.
7. Tuen Mun WSD intake has a DO criterion of more than 2 mg L^-1.

Fisheries Resources

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

· Commercial Fisheries Spawning Grounds/Nursery Areas;

· Artificial Reef Deployment Sites; and,

· Fish Culture Zones.

Brief descriptions of these sensitive receivers are presented below.

Commercial Fisheries Spawning Grounds/Nursery Areas

The waters of Northwest Lantau have been identified as important fisheries spawning/nursery grounds for commercial fisheries in Hong Kong ([19]).

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 ([20]), Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment. The AFCD study recommends a maximum SS concentration of 50 mg L^-1 (based on half of the No Observable Effect Concentration). Although a maximum concentration is recommended, the study acknowledges that site-specific data should be considered on a case-by-case basis.

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 (Section 10, Part 3).

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);

· 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 6 km and over 10 km from proposed terminal, 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 Section 9, Part 3: Marine Ecological Impact Assessment).

There is no specific water quality criterion for the AR sites, thus the WQOs criteria have been adopted. AR sites will be treated as discrete assessment points in the model.

Fish Culture Zones

There is one fish culture zone (FCZ) in the North Western waters, the Ma Wan North and East. This FCZ is over 10 km from the proposed terminal. 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 ([21]). The guideline requires the SS levels remain below 50 mg L^-1. This maximum concentration value has been used in an endorsed EIA Report ([22]) under the EIAO and has, therefore, been taken as the assessment criterion.

In the water quality modelling works, the FCZ was included as two discrete points for evaluation in the assessment against the above criteria 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 the oyster production area, thus the WQOs have been adopted.

The area nearest to the works site was included as a point in the model. If no non-compliances are found at the point, it was assumed that there will be no impacts to the area beyond it.

Marine Ecological Resources

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

· Marine Park; and

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

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). There are no specific legislative water quality criteria for Marine Parks and the water quality at this sensitive receiver is typically compared with the WQO. For the water quality assessment, discrete points have been plotted at a number of locations along the boundaries of the Marine Park.

Seagrass Beds, Mangroves, Intertidal Mudlfats & Horseshoe Crabs

Seagrass beds, mangroves 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 water quality impacts are assessed against compliance with the WQO. These habitats have been plotted as discrete points for evaluation.

Other Water Quality Sensitive Receivers

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

· Bathing Beaches;

· 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 Tuen Mun. Non-gazetted beaches are located at Lung Kwu Sheung Tan and Lung Kwu Tan. The closest non-gazetted beach to the proposed terminal is Lung Kwu Sheung Tan, at a distance of approximately 1.5 km. The closest gazetted bathing beach is Butterfly Beach at a distance of approximately 6.6 km from the proposed terminal. 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 6.8).

Seawater Intakes

There are eight seawater intakes identified as potential sensitive receivers, namely those at Black Point Power Station, Castle Peak Power Station, Tuen Mun Area 38, the Airport and Tuen Mun WSD.

Both power station intakes have specific requirements for intake water quality. The applicable criteria for temperature and SS for the Black Point Power Station and Castle Peak Power Station seawater intakes are between 17 and 32°C and between 30 and 764 mg L^-1, respectively. These values have, therefore, been taken as the assessment criteria. There are no particular criteria specified for the Tuen Mun Area 38 and the Airport intakes and hence WQOs have been adopted (Table 6.8). For theTuen Mun WSD, there WSD intake specific water quality criteria have been applied (Table 6.2).

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. Each is discussed in turn below.

6.4.1 Construction Phase

The major construction activities associated with the proposed project that may cause impacts to water quality involve the following:

· Dredging and filling for reclamation and seawall formation for the LNG terminal at Black Point;

· Dredging for the approach channel, turning basin and jetty box near the terminal for LNG carriers;

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

· Sewage discharges due to the on-site workforce;

· Site runoff 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 proposed facility have been identified as follows:

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

· Maintenance dredging of the navigation areas 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;

· Surface run-off from the terminal site;

· Sewage discharges due to the operational workforce;

· Vessel discharges;

· LNG Spillage due to accidental events; and,

· Oil Spills 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, Part 3) and has been based on the information presented in the Project Description (Section 3, Part 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 studied 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 water quality modelling output points in the vicinity of the proposed LNG terminal at Black Point are presented in Figure 6.4.

6.5.2 Uncertainties in 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, the worst 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 period 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 conservative assumptions presented above allow a prudent approach to be applied to the water quality assessment.

The following uncertainties have not been included in the modelling assessment.

· Ad hoc navigation of marine traffic;

· Near shore scouring of bottom sediment; and

· Access of marine barges back and forth the site.

It is noted that the above present mechanisms through which minor localised and short term elevations 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 Solids

The potential main impacts to water quality arising from this project during the construction phase relate to disturbances to the seabed, re-suspension of some marine sediment, and potential physico-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. In order to assess the cumulative potential impacts to water quality as a result of activities running concurrently, a total of two scenarios have been developed (Table 6.10). It should be noted that of these two scenarios, one is simply an alternative to assess the impact of using alternative dredging plant (i.e., trailing suction hopper dredger versus grab dredger).

The selected scenarios represent periods during the construction programme when the maximum number of activities may take place at any given time.

The results of these scenarios have been presented in Annex 6C. 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 the relevant depth for the respective sensitive receivers are presented under each scenario. The 90^th percentile elevations of SS are also presented as the WQO is measured as the 90^th percentile of background conditions.

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 relevant 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).

Each scenario shown in Table 6.10 will be discussed in the subsequent paragraphs. The tentative construction programme and indicative construction sequence are enclosed in Annex 6A. Figure 6.5 shows the dredging areas at seawall and approach channel and basin and Figure 6.6 shows a cross-section of the sloping seawall.

It should be noted that these scenarios are highly conservative for the following reasons.

· The sandfilling for the reclamation will primarily be carried out behind a partially constructed seawall (an opening at the seawall will be allowed for marine access), which can serve to shelter the works area from tidal currents and hence reduce the transport of fine sediment in suspension away from the works area.

· Nine emission points have been defined with sediment loss occurring simultaneously. It will be, however, unlikely to have dredgers/pelican barge operating at the same time on the site (see Annex 6A).

· The grab dredgers at the approach channel and turning basin are defined as stationary points close to the coast, which is considered to conservatively assess the impacts to the inshore ecological sensitive receivers. In reality, the grab dredgers will move farther off shore and will have less impact to the coastal sensitive receivers.

· The sandfilling works for the seawall trench are assumed to be continuous within a whole spring-neap cycle. In fact, the sandfilling works will be completed within a shorter period (about a week).

Scenario ID (report)	Tasks	Details of Construction Activities	No. of Plant and Plant Type	Code
Scenario 1a	Seawall	Dredging underneath seawall (Area A and B)	1 no. Grab Dredger	BP	01
	Seawall	Dredging underneath seawall (Area C)	1 no. Grab Dredger	BP	02
	Seawall	Sand fill for seawall trench (Area A and B)	1 no. Pelican Barge	BP	15
	Reclamation	Sand fill for reclamation area	1 no. Pelican Barge	BP	17
	Jetty Box	Grab Dredging at Jetty Box	1 no. Grab Dredger	BP	07
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area D	1 no. Grab Dredger	BP	08a
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area E	1 no. Grab Dredger	BP	09a
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area F	1 no. Grab Dredger	BP	10a
	Cooled Water Outfall	Grab Dredging under outfall	1 no. Grab Dredger	BP	12
Scenario 1b	Seawall	Dredging underneath seawall (Area A)	1 no. Grab Dredger	BP	01
	Seawall	Dredging underneath seawall (Area C)	1 no. Grab Dredger	BP	02
	Seawall	Sand fill for seawall trench (Area A and B)	1 no. Pelican Barge	BP	15
	Reclamation	Sand fill for reclamation area	1 no. Pelican Barge	BP	17
	Jetty Box	Grab Dredging at Jetty Box	1 no. Grab Dredger	BP	07
	Approach Channel and Turning Basin	TSHD Dredging at Approach Channel & TB at Area D	1 no. TSHD	BP	08b
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area E	1 no. Grab Dredger	BP	09b
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area F	1 no. Grab Dredger	BP	10b
	Approach Channel and Turning Basin	Grab Dredging at Approach Channel & TB at Area G	1 no. Grab Dredger	BP	11
	Cooled Water Outfall	Grab Dredging under outfall	1 no. Grab Dredger	BP	12

Table 6.11 Predicted SS Elevation (mg L^-1) in Scenario 1a

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 ^(c)	Max ^(c)	Max ^(d)	Max ^(d)	90%-tile	90%-tile
Intertidal Mudflats	Pak Nai	SR01	s	7.1	3.6	0.75	0.5	0.02	0.02	0.04	0.03
Horseshoe Crab Nursery Grounds	Pak Nai	SR01	a	9.7	6	3.4	4.52	0.29	0.15	1.18	0.24
Seagrass Beds/Mangroves/Oyster Farm	Pak Nai	SR02	s	7.1	3.6	0	0.03	0	0	0	0
Seawater Intakes	Black Point Power Station	SR04	b	700 ^(b)	700 ^(b)	198.56	187.81	12.51	10.76	33.41	27.48
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR05a	a	8.2	5.6	12.04 ^{(e) (f)}	2.36	0.49	0.11	1.19	0.29
Non-gazetted Beaches	Lung Kwu Tan	SR05b	a	8.2	5.6	6.79	3.08	0.26	0.26	0.55	0.74
Gazetted Beaches	Butterfly Beach	SR05c	a	8.2	5.6	0.06	0	0	0	0	0
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06a	a	8.2	5.6	0.52	0.31	0.08	0.04	0.23	0.12
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06b	a	8.2	5.6	0.28	0.35	0.03	0.03	0.1	0.11
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06c	a	8.2	5.6	1.29	1.43	0.23	0.17	0.6	0.41
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06d	a	8.2	5.6	0.79	0.75	0.09	0.08	0.3	0.22
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	SR06e	a	8.2	5.6	0.27	0.25	0.04	0.03	0.12	0.09
Seawater Intakes	Castle Peak Power Station	SR07a	b	700 ^(b)	700 ^(b)	14.77	12.94	1.11	1.04	3.23	2.72
Seawater Intakes	Tuen Mun Area 38	SR07b	b	14.2	9.8	4.43	3.77	0.38	0.29	1.61	0.88
Seawater Intakes	Airport	SR07c	b	8.9	8.8	0.35	0.16	0.02	0.02	0.07	0.04
Seawater Intakes	Airport	SR07d	b	8.9	8.8	0.04	0.13	0	0	0.01	0
Artificial Reef Deployment Area	Northeast Airport	SR07d	a	8.9	8.8	0.03	0.11	0	0	0	0
Seawater Intakes	Airport	SR07e	b	8.9	8.8	0	0.06	0	0	0	0
Seawater Intakes	Airport	SR07f	b	8.9	8.8	0	0	0	0	0	0
Spawning/Nursery Grounds	Fisheries Spawning Ground in North Lantau	SR08	a	8.2	5.6	1.51	1.58	0.27	0.26	0.71	0.71
Horseshoe Crab Nursery Grounds	Sham Wat Wan	SR10	a	8.9	6.5	0.33	0.2	0.03	0.02	0.09	0.05
Notes: a. s = surface, m = middle, b = bottom, a = depth-averaged b. The tolerance assessment criterion of 700 mg L^-1 was adopted for these seawater intakes. c. “Max” denotes maximum values recorded at a relevant water depth at the sensitive receiver over a complete spring-neap cycle simulation d. “Mean” denotes arithmetic mean values recorded at a relevant water depth at the sensitive receiver over a complete spring-neap cycle simulation e. Shaded cells mean non-compliance with the WQO. f. Contribution of each individual activities are 10.4% from grab dredging for seawall, 7.7% from sandfilling for seawall trench, 9.8% from grab dredging for approach channel and turning basin, 4.5% from grab dredging for outfall and 67.6% from sandfilling for reclamation.

Table 6.12 Predicted SS Elevation (mg L^-1) in Scenario 1b

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 ^(c)	Max ^(c)	Max ^(d)	Max ^(d)	90%-tile	90%-tile
Intertidal Mudflats	Pak Nai	SR01	s	7.1	3.6	0.75	0.58	0.02	0.02	0.04	0.04
Horseshoe Crab Nursery Grounds	Pak Nai	SR01	a	9.7	6	3.65	4.97	0.32	0.17	1.26	0.32
Seagrass Beds/Mangroves/Oyster Farm	Pak Nai	SR02	s	7.1	3.6	0	0.03	0	0	0	0
Seawater Intakes	Black Point Power Station	SR04	b	700 ^(b)	700 ^(b)	201.21	187.33	12.44	10.6	32.66	27.46
Non-gazetted Beaches	Lung Kwu Sheung Tan	SR05a	a	8.2	5.6	12.91 ^{(e) (f)}	2.4	0.49	0.11	1.2	0.29
Non-gazetted Beaches	Lung Kwu Tan	SR05b	a	8.2	5.6	7.37	3.07	0.27	0.26	0.55	0.72
Gazetted Beaches	Butterfly Beach	SR05c	a	8.2	5.6	0.07	0	0	0	0	0
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06a	a	8.2	5.6	0.54	0.32	0.08	0.04	0.24	0.12
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06b	a	8.2	5.6	0.29	0.35	0.03	0.03	0.11	0.11
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06c	a	8.2	5.6	1.06	1.18	0.24	0.17	0.63	0.43
Marine Park	Designated Sha Chau and Lung Kwu Chau	SR06d	a	8.2	5.6	0.84	0.74	0.1	0.08	0.31	0.22
Artificial Reef Deployment Area	Sha Chau and Lung Kwu Chau	SR06e	a	8.2	5.6	0.28	0.26	0.04	0.03	0.13	0.09
Seawater Intakes	Castle Peak Power Station	SR07a	b	700 ^(b)	700 ^(b)	15.51	14.78	1.16	1.11	3.45	2.9
Seawater Intakes	Tuen Mun Area 38	SR07b	b	14.2	9.8	4.7	3.97	0.41	0.31	1.7	0.91
Seawater Intakes	Airport	SR07c	b	8.9	8.8	0.35	0.16	0.02	0.02	0.07	0.04
Seawater Intakes	Airport	SR07d	b	8.9	8.8	0.04	0.13	0	0	0.01	0
Artificial Reef Deployment Area	Northeast Airport	SR07d	a	8.9	8.8	0.03	0.11	0	0	0	0
Seawater Intakes	Airport	SR07e	b	8.9	8.8	0	0.06	0	0	0	0
Seawater Intakes	Airport	SR07f	b	8.9	8.8	0	0	0	0	0	0
Spawning/Nursery Grounds	Fisheries Spawning Ground in North Lantau	SR08	a	8.2	5.6	1.47	1.58	0.27	0.27	0.72	0.73
Horseshoe Crab Nursery Grounds	Sham Wat Wan	SR10	a	8.9	6.5	0.33	0.2	0.03	0.02	0.08	0.05
Notes: a. s = surface, m = middle, b = bottom, a = depth-averaged b. The tolerance assessment criterion of 700 mg L^-1 was adopted for these seawater intakes. c. “Max” denotes maximum values recorded at a relevant water depth at the sensitive receiver over a complete spring-neap cycle simulation. d. “Mean” denotes arithmetic mean values recorded at a relevant water depth at the sensitive receiver over a complete spring-neap cycle simulation. e. Shaded cells mean non-compliance with the WQO. f. Contribution of each individual activities are 11.0% from grab dredging for seawall, 8.1% from sandfilling for seawall trench, 4.8% from grab and TSHD dredging for approach channel and turning basin, 4.8% from grab dredging for outfall and 71.4% from sandfilling for reclamation.

6.6.2 Sediment Deposition

The majority of SS elevations in water have been predicted to remain within relatively close proximity to the dredging works and, as such, the majority of sediment has been predicted to settle within relatively close proximity to the works areas. The simulated deposition rates at the artificial reefs (ARs), i.e., SR6e and SR7d during the dry and wet seasons have been assessed. The predicted deposition levels at the sensitive receivers are negligible at < 1.1 g m^-2 day^-1 which is well below the assessment criterion of 200 g m^-2 day^-1 and will not cause any adverse impacts.

6.6.3 Dissolved Oxygen Depletion

The dispersion of sediment due to dredging operations is not expected to impact the general water quality of the receiving waters. Due to the low nutrient content of sediments (see Section 7, Part 3: Waste Management), the elevation in SS levels is not expected to cause a pronounced increase in oxygen demand and, therefore, the effect on dissolved oxygen (DO) is anticipated to be minor. The effects of increased SS concentrations as a result of the proposed works on levels of dissolved oxygen, biochemical oxygen demand and nutrients (as unionised ammonia) are predicted to be minimal. Effects will be transient, localised in extent and of a small magnitude. As such, no adverse impacts to water quality through sediment release are expected to occur.

In order to verify the above assessment, the depletion of dissolved oxygen has been calculated. The degree of oxygen depletion exerted by a sediment plume is a function of the sediment oxygen demand of the sediment, its concentration in the water column and the rate of oxygen replenishment. The impact of the sediment oxygen demand (SOD) on dissolved oxygen concentrations has been calculated based on the following equation ([23]):

DO_Dep = C * SOD * K * 10^-6

where DO_Dep = Dissolved oxygen depletion (mg L^-1)

C = Suspended solids concentration (mg L^-1)

SOD = Sediment oxygen demand (mg kg^-1)

K = Daily oxygen uptake factor (set as 1 ([24]))

By reviewing the EPD sediment quality monitoring data and a recently approved EIA Report ([25]) which used 15,000 mg kg^-1 for the North Western WCZ, the sediment oxygen demand used in this study is 20,000 mg kg^-1 for the Deep Bay WCZ and the North Western WCZ.

In the abovementioned EIA Report, K was set to be 1, which means instantaneous oxidation of the sediment oxygen demand. This was a conservative prediction of DO depletion since oxygen depletion is not instantaneous and will depend on tidally averaged suspended sediment concentrations.

It is worth noting that the above equation does not account for re-aeration which would tend to reduce impacts of the SS on the DO concentrations in the water column. The proposed analysis, which is on the conservative side, will not, therefore, underestimate the DO depletion. Further, it should be noted that, for sediment in suspension to exert any oxygen demand in the water column will take time and, in the meantime, the sediment will be transported and mixed or dispersed with oxygenated water. As a result, the oxygen demand and the impact on DO concentrations will diminish as the suspended sediment concentrations decrease.

The most sensitive receivers to DO depletion are likely to be the ecological and fisheries aquatic species. The calculated results showed that the predicted oxygen depletion at these WSRs is predicted to be compliant with the WQO criterion as they would be < 0.1 mg L^-1. The sediment plumes predicted in the model are thus unlikely to deteriorate dissolved oxygen conditions in the receiving waters and will not affect the WSRs.

Contour plots of maximum DO depletion are shown in Annex 6C. It shows that the DO is depleted by less than 1 mg L^-1 for most of construction works with exception for the sandfilling works and those non-stationary works, i.e. TSHD dredging for approach channel and turning basin (code BP 08b). Interpreting the maximum plots for the moving sources should be in caution. The maximum SS level plots for those moving sources are gestalt image and may not be representative of any given moment in time. The time in which each grid cell’s maximum occurred is independent of the other grid cells. For the sandfilling works, the impacts would be substantially reduced when the seawall in reality is to be in place, as aforementioned in Section 6.6.1, to minimise the spread of sediment and hence DO depletion.

The contour plots also show that the DO depletion plume will not extend to the fisheries spawning ground in northwest Lantau and ecological resources in inner Deep Bay and hence no adverse water quality impacts on these sensitive receivers are expected.

6.6.4 Nutrients

An assessment of nutrient release during dredging has been carried out based on the SS modelling results for the unmitigated worst case works scenario and the sediment testing results for the dredging area. In the calculation it has assumed that all TIN and unionised ammonia (NH₃-N) concentrations in the sediments are released to the water. This is a highly conservative assumption and will result in the overestimation of the potential impacts.

The increase in TIN concentrations at all sensitive receivers would be less than 0.03 mg L^-1, which is considered to be a minimal effect on the water quality. The dredging works will not result in a non-compliance with the WQO.

The maximum predicted SS concentration at each SR is multiplied by the maximum concentration of TIN in sediment (mg kg^-1) in the corresponding WCZ to give the maximum increase in TIN (mg L^-1). The calculations of TIN are shown below.

Deep Bay WCZ	NW WCZ
Max SS * 142 * 10^-6	Max SS * 100 * 10^-6

Ammoniacal Nitrogen (NH₄-N) is the sum of ionised ammoniacal nitrogen and unionised nitrogen (NH₃-N). Under normal conditions of Hong Kong waters, more than 90% of the ammoniacal nitrogen would be in the ionised form. For the purpose of assessment, a correction (as a function of temperature, pH, and salinity) has been applied based on the EPD monitoring data, i.e. temperature of 24 degrees Celsius, salinity of 28 ppt and pH of 8 which represent the typical conditions of Hong Kong waters. From this it derived that NH₃-N constitutes 5% of ammoniacal nitrogen. In view that the mineralisation of the organic nitrogen will also contribute to ammonia, the calculations of NH₃-N are based on maximum TKN concentrations (mg kg^-1) in the sediment in each WCZ. Note that it is a highly conservative approach since it is assumed that 100% of organic nitrogen will be mineralised to ammonium but this is unlikely to occur in reality.

The maximum SS concentration at each SR is multiplied by the following factors to predict the maximum NH₃-N elevations.

Deep Bay WCZ	NW WCZ
Max SS * 2,600 * 10^-6 * 5%	Max SS * 2,100 * 10^-6 * 5%

The results (see Annex 6D) indicate that the increase in NH₃-N elevations due to the dredging works would be negligible comparing with the ambient concentrations. The total concentrations of NH₃-N at the water quality sensitive receivers are predicted to be well below the WQO criterion of 0.021 mg L^-1 with marginal exceedance at seawater intake of Black Point Power Station. Since it is neither an ecological sensitive receiver nor a bathing beach, the marginal exceedance will not cause significant adverse impact on the intake. In overall it is anticipated that the impacts of the SS elevations due to the dredging works on the nutrient levels are minimal and acceptable.

6.6.5 Heavy Metals and Micro-Organic Pollutants

Elutriate tests were carried out to assess the potential for a release of heavy metals and micro-organic pollutants from the dredged marine mud. The test results have been assessed and compared to the relevant water quality standards shown in Annex 6D, Part 3. The results show that most dissolved metal concentrations for all samples are below the reporting limits, with the exception of copper. In addition, all dissolved metal concentrations are found to be well below the water quality standards. The results also show that all PAHs, PCBs, TBT and chlorinated pesticides are all below the reporting limits. This indicates that the leaching of these pollutants is unlikely to occur. Unacceptable water quality impacts due to the potential release of heavy metals and micro-organic pollutants from the dredged sediment are not expected to occur.

6.6.6 Piling Works

The LNG jetty will be located to the north of Black Point. There will be two installation methods for the piling works (see Part 3 – Section 3: Project Description), namely bored piles and percussive piles.

Bored Piles

For the bored piles, a permanent casing will be driven into the seabed and the excavation of the marine soil will then take place inside. After the removal of marine soil, an I-beam will be put inside the casing, followed by concreting. Since the excavation of mud will be carried out inside the casing, it is anticipated that any release of the sediment will be trapped within the casing. In addition, the quantity of the excavated marine mud is expected to be minimal and the mud will be disposed of by a barge and is unlikely to cause unacceptable impacts to the surrounding water.

Percussive Piles

The percussive piles will comprise steel piles below seabed level and cast in situ reinforced concrete piles above seabed level. This is achieved by driving steel tubes down to required design soil resistances then filling the tubes from just below seabed level. No soil or sediment excavation will be carried out. It is expected that the piling works will cause limited disturbance to the sediments and are unlikely to cause unacceptable impacts to the receiving water.

6.6.7 Wastewater Discharges

Wastewater from temporary on-site facilities will be controlled to prevent direct discharges to marine waters adjacent to the reclamation. Wastewater may include sewage effluent from toilets and discharges from on-site kitchen facilities.

The options for dealing with sewage generated from a construction site work force are as follows.

· Option 1, Septic Tank Soakaway: This is considered acceptable for small quantities of sewage and where the ground conditions are suitable with appropriate soakaway capacity. It is considered that a septic tank is unlikely to be accepted for a flow rate of approximately 240m³ day^-1. This option is therefore discounted for a centrally located treatment facility for the entire site although it may be considered for a small number of workers at an isolated location.

· Option 2, Collect and Convey to a Public STW: This is a commonly adopted approach by contractors, in the more urbanised areas of Hong Kong, where there is no public sewer and a septic tank soakaway is not viable. Black Point is fairly remote and therefore if the anticipated sewage volume is actually realised the contractor may not consider this option to be cost effective. However, in reality the actual sewage flow generated from the construction work force is likely to be much less than 150 L head^-1 day^-1. Furthermore, the number of workers is considered a conservative and may be less than 1,600. In these cases the contractor may find disposal to a public STW cost effective. This would be seen as a secure means of sewage disposal without the risk of the contractor failing to operate a temporary STW appropriately.

· Option 3, Provision of Temporary STW to Serve the Work Force: Due to the remoteness of the site and the relatively large sewage volume the contractor may choose to construct a temporary STW. The sewage will be discharged from a seabed outfall to the north of Black Point (Figure 6.7). For the purpose of the EIA, it is recommended that plans should be made for the most onerous scenario and the assumption that the anticipated larger sewage flow may be generated and that the contractor adopts this option.

From a water quality point of view, the worst case scenario is the discharge of the treated water into the sea and hence for the assessment purpose Option 3 has been assessed. Modelling has been conducted to determine the dispersion of treated wastewater discharges during the construction phase, as described in the Water Quality Method Statement (Annex 6A, Part 3). The results (Annex 6E, Part 3) indicate that the impacts are negligible. No non-compliances with the WQO are predicted to occur in either the dry or wet seasons.

During the early stages of construction, i.e. site formation, it will be necessary to remove the sewage from site to a Public STW as the reclamation will not be in place. However, during the construction of the process facility which requires the maximum workforce and the longest site duration, it is recommended that an on-site plant be established at the location shown in Figure 6.7. The discharge will be transferred to the outfall location on the north side during operation.

6.6.8 Land Based Construction Activities

During land based construction activities for the LNG terminal and for the access roads, the primary sources of potential impacts to water quality will be from pollutants in site run-off which may enter marine waters.

Due to limited space at the Black Point site, all excavated soil will be transported off-site initially. It is intended that this material will be reused as fill within the reclamation at a level above +2.5mPD. The excavated soil therefore needs to be stored temporarily off-site (see details in Part 3 – Section 7: Waste Management).

A drainage system will be constructed around the land based working sites for the tanks. However, such drainage system can only be constructed after slope cutting works which are required for site formation. The drainage system will collect the site runoff and prevent it from running into the surrounding water.

With the proper implementation of mitigation measures, described in (Section 6.8.2), it is anticipated that no adverse water quality impacts would arise from the land based works.

6.6.9 Vessel Discharges

Construction vessels have the potential for the following liquid discharges:

· Uncontaminated deck drainage;

· Potentially contaminated drainage from machinery spaces; and

· Sewage/grey water.

Deck drainage is likely to be uncontaminated and is not likely to impact water quality. Other sources of possible impacts to water quality may arise from discharges of hydrocarbons (oil and grease) from machinery space drainage and Biochemical Oxygen Demand (BOD) and microbiological constituents associated with sewage/grey water. These waste streams are all readily amenable to control as part of appropriate practice on vessels. Possible impacts associated with construction vessel discharges are therefore considered to be minor.

No solid wastes will be permitted to be disposed of overboard by vessels during construction works, thus impacts from such sources will be eliminated.

6.6.10 Hydrotest Water

Before installation of the tank wall insulation, raw freshwater will be needed to hydrotest the LNG tanks. Approximately 28 million gallons (~ 106,000 m³) for a LNG tank with a net capacity of 160,000 m³ with about 0.25 million gallons of additional water would be required for each successive tank tested. The discharge flow rate will be approximately 1,800,000 gallons per day (~ 6,814 m³ day^-1) for the bulk pumping operation, with substantially lower rates being achieved when removing the final amounts of water from the tank bottom via a settlement pond. There are two tanks in total and hence with the abovementioned flow rate it takes about 1 mouth to discharge all the hydrotest water.

The potential additive to this water will be low concentrations of chlorine (approximately 0.05 mg L^-1). It is expected that the water will be discharged into the existing BPPS cooling water outfall, which will comply with the WQO/discharge licence requirements. Given the relatively small volume of water from the tanks relative to the volume and flow rate in the cooling water outfall system, the hydrotest tank water will dilute and disperse rapidly without causing notable changes to water quality.

6.7 Operation Phase Water Quality Impact Assessment

6.7.1 Hydrodynamics

Changes to water quality, sedimentation and erosion processes would arise if there was a significant change to the hydrodynamic regime of the Black Point coastline due to the reclamation works and seawall construction at the headland.

Figures BP_B01-B08 in Annex 6B, Part 3 show the current velocity under the baseline conditions and Figures BP_F01-08 in Annex 6F, Part 3 show the current velocity under the post-project conditions.

Modelling results show that the presence of the reclamation is likely to alter tidal currents and introduce a localised sheltering effect in the vicinity of the existing intake of the Black Point Power Station.

The approach channel and the turning basin will be located to the north of Black Point and will be dredged to approximately -15.0mPD. The results of modelling current velocities (Figures BP_F01-08 in Annex 6F) indicated that hydrodynamic changes due to the deepened seabed level are negligible.

Mathematical modelling has been carried out to examine the flushing capacity of Deep Bay. The methodology and model results are presented in Section 4 of Appendix 6A in Annex 6A. The model results show that the relative change of flushing capacity in inner Deep Bay due to the presence of the reclamation with respect to the baseline ranges from -2.4% (decrease) to +1.1% (increase). The results also indicate that for Deep Bay as a whole there is a marginal increase of the flushing in the dry season and a marginal decrease of the flushing in the wet season. In conclusion, the change in flushing capacity, and hence in water quality, due to the reclamation at Deep Bay is minimal. No adverse impacts to water quality as a result of these minor changes in hydrodynamics are expected to occur.

6.7.2 Suspended Solids

Maintenance Dredging

To the extent practical, the selection of the approach channel for the LNG carrier was based on the availability of the required charted water depth. The intent is to reduce the dredging quantities and hence potential impacts to water quality. Sedimentation associated with the approach channel and turning basin is predicted to be approximately 50 to 100 kiloton year^-1, which is equivalent to approximately 10 to 20 cm year^-1. According to these estimates, maintenance dredging is expected to be required once every four to five years and will be restricted to specific small areas.

Apart from the low frequency of the maintenance dredging, the scale of the maintenance dredging would be much less than the initial dredging works for the approach channel and turning basin which has been assessed in the previous section. Hence, it can be expected that no unacceptable adverse impacts would arise from maintenance dredging. Although increases in suspended solids in the water column may occur, these would be expected to be compliant with applicable standards and any associated impacts are expected to be of a relatively low magnitude, temporary and localised to the works area.

6.7.3 Temperature

Cooled Water Discharge

During the operation of the LNG terminal, there will be cooled water discharges from the terminal outfall as seawater will be used in the Open Rack Vaporizers. Cooled water with a temperature of approximately 12.5°C below ambient will be discharged at the seawater outfall, which is located close to the seabed in the vicinity of the LNG carrier jetty. There are no water quality sensitive receivers in the immediate vicinity of the proposed discharge point.

The maximum flow rate of the discharge is expected to be equivalent to 18,000 m³ hr^-1. Compliance with the WQO (D ± 2 °C from ambient) must be achieved at sensitive receivers.

The results from the cooled water discharge modelling are included in Annex 6G, Part 3 and have been presented as contour plots showing impacts of cooled water discharges in the vicinity of the outfall. Figures BP_G01-G02 show the maximum temperature (reduction) differences between the maximum operational discharges and the baseline, representing the most conservative case.

It can be seen from the contour plots that the maximum temperature reduction of < -2 °C will extend 3 km to the north-east in the wet season where no obvious temperature differential is predicted in the dry season. In the wet season, it is anticipated that the temperature differences are confined to the middle or bottom layer, with little impact to the surface layer of the water column. This is expected as the discharge of cooled water is close to the bottom and the relatively higher density of the cooled water results in weak vertical mixing. The contour plots also show that the maximum flow will mainly occur offshore with little extent to artificial shore to the north of the outfall. No sensitive receivers, especially ecological sensitive receivers, are expected to be affected as the plume does not impinge on any natural coastlines. No non-compliance with the WQO (± 2 °C) has been predicted at the sensitive receivers in either the dry or wet seasons. The results indicate that the dispersion of cooled water is rapid and not expected to cause an unacceptable impact.

To reduce the influence of cooled water discharge on the surrounding waters, the relatively large plume could be reduced by decreasing the temperature delta from -12.5 °C to -8.5 °C. Based on initial model results, a temperature delta of -8.5 °C could reduce the size of the plume of D < -2 °C by up to 80% in certain areas. This provides an indication that decreasing the D of the temperature of the discharge could reduce the spatial WQO exceedances.

6.7.4 Residual Chlorine Dispersion

To counteract settling and actively growing fouling organisms, the LNG cooled water circuits will be dosed with antifoulants. An efficient anti-biofouling system will be designed to prevent the growth of micro and macrofouling organisms on surfaces that are immersed in or in contact with seawater. Antifoulant control in the once through seawater is critical since marine growth in the piping and equipment must be controlled. This includes the Open Rack Vaporizers (ORVs) which will become fouled and lose heat transfer efficiency if algae or marine animals are allowed to build up on the heat transfer panels within these units. More importantly, marine growth will promote pitting corrosion. Biological control must not only render the incoming biological material incapable of growth, but it must carry a residual concentration through the system to protect it from new growth caused by airborne biological agents or prior contamination that could possibly cause growth in the system.

Sodium Hypochlorite

Chlorine, typically in the form of sodium hypochlorite, is commonly used as an antifouling agent in plants worldwide where seawater is used for cooling/warming. Sodium hypochlorite is an antifoulant that has been researched intensively. In once-through systems sodium hypochlorite is the most important antifoulant that is applied. Sodium hypochlorite is generated in a sodium hypochlorite generator by passing electrical current through seawater causing it to form sodium hypochlorite and small amounts of hydrogen. The hydrogen is vented to a safe location which is 2 to 3 meters above any personnel or adjacent equipment which should not be a problem since hydrogen is lighter than air and will readily disperse upward in a dilute form that is below the Lower Explosive Limit (LEL) for hydrogen. Hydrogen readily disperses since it is lighter than air. The sodium hypochlorite generators can be controlled to only generate as much sodium hypochlorite as required. Sodium hypochlorite will provide free residual chlorine in the seawater that can be adjusted to carry over to the ORVs providing them with protection from air borne algae that could cause algae growth on the ORVs.

The ORV residual chlorine discharge will comply with a limit of 0.3 mg L^-1 maximum. This limit will be maintained by controlling sodium hypochlorite feed automatically using residual chlorine monitors in the discharge. When chlorine (or hypochlorite) is added to seawater a series of chemical reactions occurs. The end product of these reactions includes a wide range of halogenated organic compounds. Using a low level of chlorine to prevent settlement of marine organism, rather than killing them, reduces the likelihood of halogenated organics being formed.

According to the Integrated Pollution Prevention and Control (IPPC), Reference Document on the application of Best Available Techniques to Industrial Cooling Systems (BREF) (2001), “Sodium hypochlorite is the most commonly oxidising antifoulant used in large once-through systems. It can be produced on marine sites by electrolysis of seawater. This process, called electrochlorination, avoids the transport and storage of dangerous chlorine gas or solution. The consumption of sodium hypochlorite as active chlorine demand is generally lower in and around saltwater systems than on freshwater systems, because of a higher level of dissolved and particulate organic matter in fresh water. Due to its higher bromide content, the formation of halogenated organics in seawater is reported to be lower than in freshwater (rivers), but no publications could confirm this.”

Other Alternatives

There are a number of alternatives to sodium hypochlorite for controlling biological growth that have been considered, including:

· Ultra Violet (UV) Light;

· Ozone;

· Chlorine Dioxide;

· Copper Systems; and

· Commercial antifoulants.

Ultra Violet (UV) Light

A non-chemical alternative to sodium hypochlorite is the use of UV light to control biological growth in the seawater cooling system. UV light serves as an antifoulant by damaging a microorganism’s DNA structure, inhibiting its ability to reproduce or killing the organism outright. UV treatment does not require chemicals nor does it produce harmful reaction products.

According to the Integrated Pollution Prevention and Control (IPPC), Reference Document on the application of Best Available Techniques to Industrial Cooling Systems (BREF) (2001), “UV-light may also offer possibilities in recirculating systems as a supplementary technique. UV-light alone however, cannot attack the biofouling that has settled on the surfaces of the Cooling Water System. In order to be effective, relatively clear cooling water is needed, since the light must be able to penetrate into the water column.”

While UV light has been a useful technique for treating certain cooling water systems, there are several issues that limit its applicability to the treatment of the Project’s ORV system. There is a notable lack of operational experience with UV treatment in subsurface marine applications. Monitoring the operation and changing the UV lights once every 5,000 hours would be difficult when the system is located at 15 - 25 m below sea level. Silt and other materials present in the seawater would foul the lights, requiring frequent cleaning for it to remain effective at these depths. Expensive additional pre-treatment of the water might even be necessary to ensure that the UV light penetrates the water column. As a direct, non-chemical process, UV light does not provide residual biological control which is necessary to protect the ORVs.

While the environmental effects of UV light are expected to be less harmful then halogenated antifoulants, the technique requires special care, is expensive, is unproven in subsurface marine applications, does not provide residual fouling protection and is not applicable in all situations. UV-light alone cannot attack the biofouling that has settled on the surfaces of the ORV since it does not provide residual biological control. Thus, UV light is not considered technically acceptable for this application.

Ozone

In recent years, ozone has been employed as an alternative to chlorine disinfection in potable water and wastewater applications. Ozone kills microorganisms by damaging or destroying the cell wall. Ozone can be generated onsite with electricity using commercially available ozone generators which use either a Pressure Swing Absorption (PSA) unit or liquid oxygen tank to provide a pure or enriched source of oxygen.

According to the Integrated Pollution Prevention and Control (IPPC), Reference Document on the application of Best Available Techniques to Industrial Cooling Systems (BREF) (2001), “With the relatively smaller volumes of recirculating wet systems alternative treatments are successfully applied, such as ozone, but they require specific process conditions and can be quite costly.”

There are several notable environmental and safety issues that limit the applicability of ozone for the proposed use. Corrosion is a particularly complex problem with ozone treatment. As a strong oxidant, ozone accelerates the corrosion of metals in water, damaging any pipes and equipment not made of corrosion-resistant materials. Without corrosion protection measures, ozone could accelerate the corrosion of the vaporizers causing them to have a shortened lifespan and possible failure. Correcting this problem would necessitate the use of exotic metallurgy, introducing the risk of putting metallic ions to the seawater which could also damage the ORVs.

Ozone production requires a considerable amount of energy and is relatively expensive due to the fact that the efficiency of the ozone generators is very low. The ozone generators would require an ozone destruction unit (fired unit) to destroy any excess ozone production which would be harmful to the atmosphere. This destruction unit is also expensive and would represent an additional source of NOX emissions. Additionally, ozone, like UV, does not provide residual biological control since it is very reactive and will be consumed in the first few seconds after application.

In terms of safety, ozone is a noxious gas which can damage lung function. Any uncontrolled ozone release from a generator or destruction unit would represent a potential hazard to site workers.

Ozone is preferably used in very clean recirculating cooling systems, and it is noted that its high reactivity makes ozone unsuitable for application in once-through system or long line systems. Ozone is not practical in this application due to the lack of experience of this size unit, corrosion concerns, lack of residual biological control, high costs, increased NOx emissions and potential environmental hazard from ozone releases.

Chlorine Dioxide

Chlorine dioxide is an effective biological control agent normally used in applications onshore where ammonia or other agents make the use of free chlorine ineffective. Unlike UV light or ozone, chlorine dioxide does provide a residual that would protect the ORVs. Chlorine dioxide must be generated onsite using special equipment.

According to the Integrated Pollution Prevention and Control (IPPC), Reference Document on the application of Best Available Techniques to Industrial Cooling Systems (BREF) (2001), “Chlorine dioxide (ClO2) has been considered as an alternative to hypochlorite (HOCl) for seawater conditions and as a freshwater biocide due to its effectiveness as a disinfectant and to its strong reduction in the formation of organohalogenated by-products in the effluent. It has been reported as an effective and economical application in cooling water systems for control of micro-organisms at relatively low dosages.”

There are several notable environmental and safety issues that limit the applicability of chlorine dioxide for the proposed use. The generation of chlorine dioxide would depend on the delivery of hazardous chemicals to the site. The generation equipment would consume a large area of space along with chemical storage. As a consequence, capital and operating costs for a chlorine dioxide system would be considerably higher than those for a conventional sodium hypochlorite system.

While some residual antifouling capacity is beneficial, chlorine dioxide can leave undesirable residuals that are much more persistent in the environment than free chlorine. Since chlorine dioxide is resistant to oxidation and reaction with ammonia, it will persist in the seawater much longer than the other options. Chlorine dioxide can react with other compounds to form undesirable by-products such as aldehydes, ketones and quinones or epoxydes under certain circumstances. Some aldehyde and eopxydes are known to be carcinogens or mutagens which may persist past the mixing zone upon discharge into the open sea. Since chlorine dioxide is not widely used for this purpose, the impacts of undesirable side reactions with organic compounds that form undesirable disinfection by-products are not as well studied.

The environmental and safety risks of using chlorine dioxide prevent this option from being further considered for this application.

Copper Systems

Copper systems use copper ions to control biological growth by inhibiting the attachment of fouling organisms to process piping and equipment surfaces. The copper ions are supplied by the electrolysis of seawater which eliminates the need to transport and store hazardous chemicals.

According to notes on copper ion treatment provided in the Integrated Pollution Prevention and Control (IPPC), Reference Document on the application of Best Available Techniques to Industrial Cooling Systems (BREF) (2001), “…the residual concentration of the lethal copper compounds need further examination as the discharge to the receiving water could cause harmful effects.”

There are several notable operational and environmental issues that limit the applicability of copper ions for the proposed use. One basic concern is that copper ion treatment is not a common technique and that to our knowledge none of the LNG terminal operators have experience operating this unconventional control system. Another concern is that existing copper ion treatment has not yet been attempted in a system that contains aluminium. As such, there is the potential that an undesirable reduction-oxidation reaction may take place between the copper ions and the aluminium in the ORVs, accelerating the corrosion of the vaporizers.

While copper is commonly used as a protective coating for vessels, the proposed application would introduce considerable amounts of the metal directly into the marine environment. The concentrations of copper at the seawater outfall could potentially reach toxic levels of concern given the high volume of ORV throughput and the duration of the project.

Given the uncertainty of ORV corrosion and the introduction of a non-biodegradable metal to the marine environment, copper ion treatment is not considered technically acceptable for this application.

Commercial Antifoulants

One chemical company produces an antifoulant that is a catatonic surfactant that is short-lived in plant systems and the environment because of rapid absorption onto anionic substrates and sediments in natural aquatic ecosystems.

Mussels do not detect this chemical as a noxious compound, and they do not close their shells. This allows the mussels to be killed quickly, with significant mortality in 4 to 24 hours. The agent causes detachment of adults and is effective on molluscs at all life stages. It also effectively controls microfouling organisms, barnacles, hydrozoa, bryozoa, bacteria, fungi, algae, Asiatic clams, and bacterial, fungal, and algal slime. The agent is compatible with stainless steel, copper alloys, most plastics and rubbers, chrome alloys, aluminium, and FRP piping.

There are several notable operational and environmental issues that limit the applicability of this antifouling agent for the proposed use. The chemical is corrosive to skin and is flammable, making it a hazard to handle. The high residual levels after discharge along with the extremely high cost of this material make it operationally and environmentally unsuitable for this application. As such, the chemical is not considered suitable for this application due to its potential negative effects on sea life and excessive cost.

Summary

To conclude, UV and ozone generator options are not recommended because they do not provide the required residual biological control for the ORVs along with other operational difficulties. Although chlorine dioxide provides residual control, it uses hazardous chemicals and will consume considerable space for producing the chlorine dioxide and chemical storage and unloading in addition to operator safety issues. The proposed commercial antifoulant is not considered suitable for this application due to its potential negative effects on sea life and excessive cost.

Copper ion treatment is currently not in wide use and there is limited operating experience for this unconventional system. Additionally, the potential corrosion problems with the copper-aluminium interaction on the Open Rack Vaporizers (ORV’s) are unknown and are therefore currently not viewed as a viable option.

The one viable option remaining is sodium hypochlorite. It is a safe, proven option that has been used successfully for many years on many once through seawater applications with ORVs. For most applications, a carefully designed sodium hypochlorite system offers the most complete and comprehensive technique for the reduction of both macrofouling and microfouling.

Careful design can also dramatically reduce the environmental impact of modern sodium hypochlorite systems. This includes a properly designed chlorine monitor to control the residual chlorine levels in the system with care being taken to choose an instrument that has the proper operating range to provide maximum sensitivity throughout all foreseeable operational scenarios.

Residual chlorine in the marine environment can be harmful to marine organisms only if concentrations exceed tolerance levels. It has been found that harmful effects begin to occur at concentrations above 0.02 mg L^-1in water ([26]). The discharge limit for residual chlorine is 1.0 mg L^-1 according to EPD’s Technical Memorandum for Effluents issued under Section 21 Water Pollution Control Ordinance, Cap 358. There is no value specified in the WQOs for the Deep Bay WCZ, nor for any other WCZ. 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, which is also the criterion adopted in the previously approved EIA Report for the 1,800 MW Gas-fired Power Station at Lamma Extension ([27]).

The water quality impacts due to chlorine discharges have been assessed using computational modelling (see Water Quality Method Statement in Annex 6A, Part 3). The results from the chlorine simulations are presented as contour plots of mean and depth averaged chlorine concentrations for the spring and neap tidal periods in the wet and dry seasons. The contour plots are provided in Annex 6H, Part 3. Figures BP_H01-08 present the maximum operational discharges while Figures BP_H09-16 show the fluctuating flow operational discharges. Both discharge rates appear to result in a similar pattern of residual chlorine dispersion.

The model used the assumption that the terminal would discharge total residual chlorine at a maximum concentration of 0.3 mg L^-1. This concentration is similar to that for most power stations in Hong Kong and is below the EPD’s limit of 1.0 mg L^-1([28]) but it is not optimal for long term functioning of the ORV system at the LNG terminal.

The model results for the 0.3 mg L^-1 discharge concentration have shown that the dispersion of the residual chlorine was confined to the immediate vicinity of the outfall point.

The dispersion results obtained for the dry season have shown that the residual chlorine is well-mixed in the whole water column. In the wet season, the majority of the residual chlorine is likely to be contained within the bottom layer and the middle layers, with no chlorine in the surface layer. This indicates that the release of the chlorine near to the seabed with the presence of freshwater from the Pearl River Delta in the wet season and the relatively higher density of the cooled water in which the chlorine is discharged, results in weak vertical mixing.

Based on the predictions, the maximum extent of the > 0.01 mg L^-1 contour is < 50 m (bottom layer) from the discharge point during the dry season and < 70 m (bottom layer) during the wet season, resulting from the 0.3 mg L^-1chlorine discharge (Figure BP_H01 and Figure BP_H05). These areas were defined as the “mixing zones”. Due to their small extent, and the fact that no sensitive receivers would be affected, no unacceptable impacts from residual chlorine discharge to water quality are expected to occur.

Due to the small extent of the mixing zones, and the fact that no sensitive receivers would be affected, no unacceptable impacts from residual chlorine discharge to water quality are expected to occur.

6.7.5 On-site Wastewater Discharges

During the operation of the LNG receiving terminal, it is expected that there will be a workforce of about 100 people. It has been conservatively estimated that an average of approximately 35 m³ of sewage would be produced by this workforce per day (Annex 6A, Part 3).

A sewage treatment system will be provided for the treatment of wastewater. A sanitary waste system consisting of a collection system will be provided. Due to the low number of operational staff in the terminal, the volume of the sewage generated would be limited and would be treated on-site before being discharged in accordance with the EPD’s required standards under the Water Pollution Control Ordinance.

Modelling has been conducted to assess the dispersion of treated wastewater discharges during the operation phase. Modelling methods are discussed in the Water Quality Method Statement (Annex 6A). The location of the sewage discharge is shown in Figure 6.7. The results (see Annex 6I) indicate that the impacts of the wastewater discharges are negligible. No non-compliance with the WQO is predicted to occur in either the dry or wet seasons throughout the operation phase.

6.7.6 Vessel Discharges

No adverse impacts are expected to occur from vessel discharges during the operation phase, as with the construction phase (Section 6.6.9).

No ballast water from the LNG carrier will be discharged in Hong Kong waters. The LNG carrier will arrive at the Hong Kong terminal loaded with LNG and with empty ballast water tanks. Ballast water will be taken into the LNG carrier ballast tanks at the terminal simultaneously during the LNG discharge.

The handling of ballast water by the LNG carrier will always be in accordance with IMO resolution A.868(20) adopted by the IMO assembly in November 1997. This requires the LNG carrier to have the ability to change all ballast water at sea between discharge port and load port. In addition, the provisions of the Convention for the Control and Management of Ship's Ballast Water and Sediments adopted 13 February 2004 (which entered into force at a later date) will also be fully complied with.

6.7.7 Accidental Spill of LNG

An LNG release would be vaporized quickly into the atmosphere and would not be expected to impact water or sediment quality. If spilled onto the LNG Terminal jetty deck or into the ocean (LNG is less dense than water), LNG would boil rapidly (due to exposure to higher ambient temperatures). Due to the material’s density and turbulence created by the rapid boiling, an LNG spill would vaporize rapidly, leaving no environmental residue.

It is worth noting that there is a sump at the berth large enough to capture and manage a major spill from the unloading lines and contain it on the site. Other leaks at the terminal are designed to be routed to containment basins for evaporation and treatment and would not reach the sea. Therefore an LNG spill would be only associated with the unloading arms, which are hanging over the sea, outside of the spill containment area. It should also be noted that the LNG terminal has an emergency shutdown system (PERC) that continuously monitors the mooring system and motions of the unloading arms. Upon sensing any irregularities in either of these systems, the unloading operation is automatically shutdown. This system has quick operating shutoff valves that among other places are located at the unloading arm connection to minimize the possibility of a LNG spill. The system can also be actuated manually by the terminal operator who is always present at the dock during unloading or the ship’s cargo master who is also present. Thus, if the ship were to break from its mooring, the LNG transfer would shutdown instantly without loss of cargo.

A leak from the unloading arms has a frequency of 4 x10^-3 per year, while a full rupture has a frequency of 4 x10^-5 per year (for details refer to Part 2 - Section 13.5). Other elements of the LNG Receiving Terminal have an even lower frequency of leakage and hence the leak from the unloading arms is examined. To investigate the effects of a spill on water quality, a full bore rupture scenario was modelled. It was assumed that unloading arms part when an extremely high atypical wave due to a passing ship causes the LNG Carrier to break free from its moorings.

The pumping rate during carrier unloading is 601 kg s^-1 (equivalent to 1.3 m³ s^-1) per unloading arm. For the purpose of modelling, if a rupture occurs, a 30s release of LNG is assumed. This is based on the closing time of the emergency shutdown valves (ESV) and the reaction time of personnel to activate the emergency shutdown device (ESD). However, the inventory of LNG between ESVs is about 80m³. A release would therefore consist of the inventory plus 30s of pumping, a total of about 120 m³. The modelling assumes this is released at a constant rate of 1.3 m³ s^-1 for 92s. In reality, once the ESVs close, the discharge rate will decrease beyond 30s and be caused by gravity draining only. The modelling approach is therefore conservative.

The spill is further assumed to take place on water and is allowed to spread isotropically without confinement. Modelling was performed using PHAST for four weather conditions covering a range of atmospheric stability classes of B through to F, and a range of wind speeds from 2m s^-1 to 7m s^-1. The model includes the effects of gravitational spreading, surface tension forces and vaporisation rate in calculating the pool size. The PHAST model was adopted as it is used in the Quantitative Risk Assessments (QRAs) for the terminal and marine transit of the LNG Carrier.

The results (Figure 6.8) show transient pool behaviour, growing to maximum size after about 1 minute and completely vaporising after 2 minutes. The liquid rainout fraction is about 20% whereas 80% of LNG would be vaporised (conservatively a release height of 1 m was specified in the modelling) but the extent depends on weather conditions. This factor explains the difference in the four curves. The results show that the pool size is likely to be affected by atmospheric stability and less so by wind speed. The pool size radius is in a range of 23 m and 31 m, which is considered to be small. It is hence anticipated that substantial vaporisation, which is caused by turbulent mixing and heat transfer from the air to vaporise the LNG, will take place before the LNG reaches the water.

Similarly, results of the QRA of the LNG Carrier transit have indicated that in the highly unlikely event of a breach of containment of the double hull of the LNG Carrier the spill would have a maximum radius of 85 m in the worse case event. This has been determined through mathematical modelling, again using the PHAST model for consistency.

In summary, should an accidental spill of LNG occur on the sea surface the LNG will not mix with water or dissolve in water but will stay on the surface and evaporate rapidly leaving no residue. The LNG spill will cause immediate cooling of the surface water which will rapidly return to normal temperature due to the buffering effect of the ocean. Hence no impacts to water quality would be expected in the unlikely event of an accidental spill of LNG on the water.

Figure 6.8 LNG Pool Size for a Spill from the Unloading Arm

Notes:

“2F” denotes a wind speed of 2 m s^-1 under stable air-turbulence conditions.

“3D” denotes a wind speed of 3 m s^-1 under neutral air-turbulence conditions.

“7D” denotes a wind speed of 7 m s^-1 under neutral air-turbulence conditions.

“2.5B” denotes a wind speed of 2.5 m s^-1 under unstable air-turbulence conditions.

6.7.8 Accidental Spill of Fuel from LNG Carrier

In the unlikely event of an accident, the special design of the storage tanks well prevents the fuel from leaking into the sea. Fuel for propulsion and ship services is carried in storage tanks installed inside double hulls at the forward end and the aft end of the vessel. The forward storage tanks are located aft of the fore peak tank and forward ballast tank or bow thruster room at a distance about 10 to 20 m from the bow to afford protection against collision. The outboard sides and bottoms of all fuel tanks are separated from the hull sides and bottom with abutting ballast tanks or void spaces so that any potential oil tank boundary leakage will not reach the sea. In addition, hull bottom or side damage will not impair the tank boundary thus preventing pollution of the sea. This feature constitutes double hull protection and hence minimises the likelihood of failure as far as reasonably practicable.

It is considered that a spillage of fuel is highly unlikely given the above; however, the Study Brief requires that a potential scenario is examined.

Uncertainty of Fuel Spill

There is uncertainty as to how much fuel will actually be contained within the ship’s fuel storage system for every voyage; however, the following factors have to be taken into account:

· LNG tanks not filled to capacity;

· Protective location of fuel tanks; and

· Geometric factor of fuel tanks.

Therefore, although the worst case analysis of the largest single tank being breached was modelled, the frequency of such an event is very small and hence in the unlikely event of such an event arising the quantity of fuel released will be lower than that modelled. In the model, it is assumed that all oil is released from a fulfilled tank and the protection features of the tank are not considered in the model despite it is unlikely to occur.

Impact Assessment

Should any rupture of the tank occur it is essential to implement emergency contingency plans to effectively control and clean up accidental spillages at short notice and to minimise the quantities of fuel reaching water sensitive receivers. This is the purpose of carrying out a mathematical modelling assessment of the behaviour of a hypothetical fuel spill. The modelling assumptions are presented in Annex 6A.

It is important to note that the modelling is based on a multiplicity of conservative parameter inputs to identify the extreme range of plume movement that might be credibly predicted. The output is intended to facilitate implementation of an effective contingency plan to ensure best practices in controlling accidental oil spillages, notwithstanding the very low likelihood of such an event ever occurring in practice.

The most conservative case considered is the holing of the largest single tank containing fuel on board a 215,000 m³ class LNG Carrier, which is a carrier class considered in the MQRA. This worst case scenario considers only the consequence on water quality and as it does not consider the low frequency it is extremely conservative in nature.

In the model, it is assumed that a spill occursalong the Urmston Road prior to reaching the Black Point site. This scenario was chosen due to the proximity of the spill to the CPPS and the Marine Park at Lung Kwu Chau and Sha Chau.

In order to examine the dispersion pattern and movement of an oil plume, it is assumed that no evaporation and emulsification is allowed and consequently a highly conservative case has been simulated. The modelling has been conducted using the Oil module of the particle tracking (PART) model of the Delft 3D suite of models.

It is assumed that necessary contingency actions will be implemented within 24 hours after the release and hence a summary of the fuel spill travel route over the 24 hour period is shown in Tables 6.13 and 6.14.

Table 6.13 Movement of Fuel Spill (Dry Season)

Location	The n^th hour after Release
Urmston Road near Castle Peak (release point)	0 – 3
North coast of the Brothers	4 – 8
Urmston Road and Northeast of the Airport	9 – 13
Open water to the north of the Brothers	14
Northeast of Lantau	15
Ma Wan	16
North of Tsing Yi	17 – 24

Table 6.14 Movement of Fuel Spill (Wet Season)

Location	The n^th hour after Release
Urmston Road near Castle Peak (release point)	0 – 4
Open water to the north of the Brothers	5
North coast of the Brothers	6
Northeast of Lantau	7 – 8
Between northeast of Lantau and Ma Wan	9 – 11
Between northeast of Lantau and the Brothers	12 – 19
Between northeast of Lantau and Ma Wan	20 – 23
Northeast of Lantau	24

For the dry season, it is evident that the contingency actions should be implemented to control and contain the fuel plume within 16 hours, before it disperses to the Ma Wan fish culture zone.

For the wet season, the plume is likely to move much faster but not farther than Ma Wan. In order to control and contain the plume, it is recommended that the contingency actions should be implemented within 10 hours.

6.7.9 Contaminated Site Run-off

Measures have been put in place to ensure the management and control of day-to-day activities at the terminal that involve the use of potentially contaminating materials, such as fuel and lube oils etc. These measures are presented and discussed in Section 14. The measures will ensure that surrounding marine waters are not affected by contaminants in run-off from the site.

6.8 Water Quality Mitigation Measures – Construction Phase

The water quality modelling works have indicated that for both the dry and wet seasons, the works can proceed at the recommended working rates without causing unacceptable impacts to water quality sensitive receivers. In instances where there are exceedances of the applicable standards, they have been predicted to be transient and therefore not of concern.

Unacceptable impacts to water quality sensitive receivers have been avoided through the adoption of the following measures.

· Siting: A number of locations were studied for the LNG terminal, with the principal aim of avoiding direct impacts to sensitive receivers.

· Reduction in Indirect Impacts: The LNG terminal is located at a sufficient distance from water quality sensitive receivers so that the dispersion of sediments from the construction works does not affect the receivers at levels of concern (as defined by the WQO and tolerance criterion).

· Adoption of Acceptable Working Rates: The modelling work has demonstrated that the selected working rates for the dredging operations will not cause unacceptable impacts to the receiving water quality. Details regarding the working rates for different scenarios are presented in Section 3.3 of Annex 6A, Part 3.

In addition to these pro-active measures that have been adopted for the proposed Project, the following operational constraints and good site practice measures for dredging and construction run-off are also recommended. It should be noted that there is no requirement for constraints on the timing or sequencing of the works, as all concurrent scenarios have been demonstrated not to cause adverse water quality impacts.

6.8.1 Dredging and Filling

The impacts to water quality from the loss of sediment to suspension was assessed in terms of the maximum rates of dredging and/or filling during the construction of the seawall, reclamation and approach channel and turning basin. The assessment was carried out based on the predicted loss rates of fine sediment to suspension from the different types of plant working on the site during the times of maximum dredging and/or filling. The highest loss rate was predicted to occur during the time at which the maximum rate of dredging was occurring. The maximum loss rate should then be limited to the values adopted in the Study and it was predicted that this rate of loss would not give rise to adverse impacts. It is therefore recommended that the maximum loss rate during the dredging works be kept at these limits.

The following measures shall apply at all times:

· No overflow is permitted from the trailer suction hopper dredger but the Lean Mixture Overboard (LMOB) system will be in operation at the beginning and end of the dredging cycle when the drag head is being lowered and raised.

· Dredged marine mud will be disposed of in a gazetted marine disposal area in accordance with the Dumping at Sea Ordinance (DASO) permit conditions.

· Disposal vessels will be fitted with tight bottom seals in order to prevent leakage of material during transport.

· Barges will be filled to a level, which ensures that material does not spill over during transport to the disposal site and that adequate freeboard is maintained to ensure that the decks are not washed by wave action.

· After dredging, any excess materials will be cleaned from decks and exposed fittings before the vessel is moved from the dredging area.

· The contractor(s) will ensure that the works cause no visible foam, oil, grease, litter or other objectionable matter to be present in the water within and adjacent to the dredging site.

· If installed, degassing systems will be used to avoid irregular cavitations within the pump.

· Monitoring and automation systems will be used to improve the crew’s information regarding the various dredging parameters to improve dredging accuracy and efficiency.

· Control and monitoring systems will be used to alert the crew to leaks or any other potential risks.

· When the dredged material has been unloaded at the disposal areas, any material that has accumulated on the deck or other exposed parts of the vessel will be removed and placed in the hold or a hopper. Under no circumstances will decks be washed clean in a way that permits material to be released overboard.

· Dredgers will maintain adequate clearance between vessels and the seabed at all states of the tide and reduce operations speed to ensure that excessive turbidity is not generated by turbulence from vessel movement or propeller wash.

· Deploy silt curtain to minimise the elevation of suspended solids to nearby sensitive receivers ([29]). Details of silt curtain installation should be proposed by the contractor prior to the commencement of dredging/sandfilling works and submitted to the IEC for approval.

· During dredging operations, cage type silt curtains will be installed to enclose the dredging areas next to the grab dredgers.

· A constructed seawall will be in place before the commencement of the sandfilling works for reclamation. The seawall will be above the high water level and will have an opening of 50 - 100 m for barge access.

· In case the seawall trench is filled by sand, the dispersion of the sediment plume will be restrained by installation of silt curtain around the sandfilling area.

As discussed in Section 6.6, it is expected that the construction works are generally environmentally acceptable for most sensitive receivers. They will give rise to short-term exceedances at one sensitive receiver, i.e., non-gazetted beach at Lung Kwu Sheung Tan (SR5a). Table 6.15 presents the predicted SS values at SR5a after applying the above mitigation measures including construction a seawall, installation of stand type silt curtains around the sandfilling areas, and deployment of cage type silt curtains around the dredging areas next to the grab dredgers.

As seen from Table 6.15, no WQO exceedance is predicted if the deployment of the proposed mitigation measures is in place during dredging and filling works.

Sensitive Receiver	Name	ID	Scenario	WQO Allowable Elevation	Without Mitigation Measures	Proposed Mitigation Measures	Reduction Factor of Cage Type Curtain and Seawall^(c)	With Cage Type Curtain and Seawall	Reduction Factor of Stand Type Curtain	With Stand Type Curtain
Non-gazetted Beach	Lung Kwu Sheung Tan	SR5a	1a	8.2	5.6	12.04 ^(a)	2.36	· Seawall (with a 50-100 m opening) in place prior to the sandfilling works; · stand type silt curtain around the sandfilling area; and · cage type silt curtain next to grab dredger	75%	3.7	-	60%	3.1	-
Non-gazetted Beach	Lung Kwu Sheung Tan	SR5a	1b	8.2	5.6	12.91 ^(b)	2.4	· Seawall (with a 50-100 m opening) in place prior to the sandfilling works; · stand type silt curtain around the sandfilling area; and · cage type silt curtain next to grab dredger	75%	4.0	-	60%	3.4	-

6.8.2 Land Based Construction Activities

Appropriate on-site measures are defined to reduce potential impacts, which will be sufficient to prevent adverse impacts to water quality from land based construction activities. These measures are appropriate for general land based construction activities.

Construction Run-off

· Prior to the commencement of the site formation earthworks, surface water flowing into the site from uphill will be intercepted through perimeter channels at site boundaries and safely discharged from the site via adequately designed sand/silt removal facilities such as sand traps.

· Channels, earth bunds or sand bag barriers will be provided on site to direct stormwater to silt removal facilities. The design of silt removal facilities will make reference to the guidelines in Appendix A1 of ProPECC PN 1/94.

· The surface runoff or extracted ground water contaminated by silt and suspended solids will be collected by the on-site drainage system and discharged into storm drains after the removal of silt in silt removal facilities.

· Unprotected partially formed soil slopes will be temporarily protected by plastic sheetings, suitably secured against the wind, at the end of each working day.

· Earthworks to form the final surfaces will be followed up immediately with surface protection and drainage works to prevent erosion caused by rainstorms.

· Appropriate surface drainage will be designed and provided where necessary. All slope drainage will be designed to the Geotechnical Manual for Slopes published by the Geotechnical Engineering Office of The Civil Engineering and Development Department.

· Temporary trafficked areas and access roads formed during construction will be protected by coarse stone ballast or equivalent. These measures shall prevent soil erosion caused by rainstorms.

· Drainage systems, erosion control and silt removal facilities will be regularly inspected and maintained to ensure proper and efficient operation at all times and particularly following rainstorms. Deposited silt and grit will be removed regularly.

· Measures will be taken to reduce the ingress of site drainage into excavations. If trenches have to be excavated during the wet season, they will be excavated and backfilled in short sections wherever practicable. Water pumped out from trenches or foundation excavations will be discharged into storm drains via silt removal facilities.

· Open stockpiles of construction materials (for example, aggregates, sand and fill material) of more than 50 m³ will have measures in place to prevent the washing away of construction materials, soil, silt or debris into any drainage system.

· Manholes (including newly constructed ones) will be adequately covered and temporarily sealed so as to prevent silt, construction materials or debris being washed into the drainage system.

· The precautions to be taken at any time of year when rainstorms are likely together with the actions to be taken when a rainstorm is imminent or forecasted and actions to be taken during or after rainstorms are summarised in Appendix A2 of ProPECC PN 1/94.

· Oil interceptors will be provided in the drainage system where necessary and regularly emptied to prevent the release of oil and grease into the storm water drainage system after accidental spillages.

· Temporary and permanent drainage pipes and culverts provided to facilitate runoff discharge will be adequately designed for the controlled release of storm flows.

· The temporary diverted drainage will be reinstated to the original condition when the construction work has finished or when the temporary diversion is no longer required.

Boring and Drilling Water

· Water used in ground boring and drilling for preparation of blasting or rock / soil slope stabilization works will be re-circulated to the extent practicable after sedimentation. When there is a need for final disposal, the wastewater will be discharged into storm drains via silt removal facilities.

Wastewater from Building Construction

· Wastewater generated from concreting, plastering, internal decoration, cleaning work and other similar activities, will undergo large object removal by installing bar traps at the drain inlets. It is not considered necessary to carry out silt removal due to the small quantities of water involved. Similarly, pH adjustment of such water is not considered necessary due to the small quantities and the fact that the water is only likely to be mildly alkaline.

Wastewater from Site Facilities

· During the early stages of work, portable chemical toilets will be used and the effluent will be shipped offsite until the temporary sewage treatment work (STW) plant is operational.

· Sewage from toilets, kitchens and similar facilities will be discharged into a foul sewer. Wastewater collected from canteen kitchens, including that from basins, sinks and floor drains, will be discharged into foul sewers via grease traps. The foul sewer will then lead to the temporary STW plant prior to effluent discharge to the ocean.

· Vehicle and plant servicing areas, vehicle wash bays and lubrication bays will, as far as practical, be located within roofed areas. The drainage in these covered areas will be connected to foul sewers via an oil/water interceptor.

· Oil leakage or spillage will be contained and cleaned up immediately. Waste oil will be collected and stored for recycling or disposal, in accordance with the Waste Disposal Ordinance.

Storage and Handling of Oil, Other Petroleum Products and Chemicals

· Fuel tanks and chemical storage areas will be provided with locks and be sited on sealed areas.

· The storage areas of oil, fuel and chemicals will be surrounded by bunds or other containment device to prevent spilled oil, fuel and chemicals from reaching the receiving waters.

· The Contractors will prepare guidelines and procedures for immediate clean-up actions following any spillages of oil, fuel or chemicals.

· Surface run-off from bunded areas will pass through oil/water separators prior to discharge to the stormwater system.

Wastewater from Concrete Batching Plant

· Wastewater generated from the washing down of mixer trucks and drum mixers and similar equipment should be recycled wherever practicable. To prevent pollution from wastewater overflow, the pump sump of any wastewater recycling system will be provided with a standby pump of adequate capacity.

· Under normal circumstances, surplus wastewater from the concrete batching will be treated in silt removal and pH adjustment facilities before it is discharged into foul sewers. Discharge of this wastewater into storm drains will require more elaborate treatment and regular testing checks. Surface run-off will be separated from the concrete batching plant as much as possible and diverted to the stormwater drainage system. Surface run-off contaminated by materials in the concrete batching plant will be adequately treated before disposal into stormwater drains.

6.9 Water Quality Mitigation Measures – Operation Phase

6.9.1 Hydrodynamics

The hydrodynamic modelling has predicted that the reclamations of the marine works and structures will have minimal effects on hydrodynamics and water quality. Mitigation measures are not considered to be necessary.

6.9.2 Cooled Water and Residual Chlorine Discharge

For the cooled water discharge, it is proposed that the cooled water with a temperature of approximately 8.5 °C, instead of 12.5 °C, below ambient should be discharged at the seawater outfall.

Regarding the residual chlorine discharge, the relatively low concentration of antifoulant combined with the high degree of mixing inherent in the coastal margin will result in rapid dilution of the effluent to non-significant concentrations and hence mitigation measures are considered unnecessary.

6.9.3 Storage and Handling of Oil, Other Petroleum Products and Chemicals

· Fuel tanks and chemical storage areas should be provided with locks and be sited on sealed areas.

· The storage areas of oil, fuel and chemicals should be surrounded by bunds or other containment device to prevent spilled oil, fuel and chemicals from reaching the receiving waters.

· Guidelines and procedures will be established for immediate clean-up actions following any spillages of oil, fuel or chemicals.

· Surface run-off from bunded areas should pass through oil/grease traps prior to discharge to the stormwater system.

Other measures are detailed in Section 14 to prevent groundwater contamination.

6.9.4 Wastewater

· Sewage from toilets, kitchens and similar facilities should be discharged into a foul sewer. Wastewater collected from canteen kitchens, including that from basins, sinks and floor drains, should be discharged into foul sewers via grease traps. The foul sewer will then lead to the sewage treatment plant prior to effluent discharge to the ocean.

· Vehicle and plant servicing areas, vehicle wash bays and lubrication bays should, as far as possible, be located within roofed areas. The drainage in these covered areas should be connected to foul sewers via a petrol interceptor.

· Oil leakage or spillage should be contained and cleaned up immediately. Waste oil should be collected and stored for recycling or disposal, in accordance with the Waste Disposal Ordinance.

6.10 Environmental Monitoring and Audit (EM&A)

6.10.1 Construction Phase

Water quality monitoring and auditing is recommended for the construction phase. The specific monitoring requirements are detailed in the Environmental Monitoring and Audit Manual (EM&A) associated with this EIA Report.

6.10.2 Operation Phase

As no unacceptable impacts have been predicted to occur during the operation of the LNG terminal at Black Point, monitoring of marine water quality during the operational phase is not considered necessary. It is noted that the operational discharges from the terminal will require a license under the WPCO which stipulates regular effluent monitoring as part of the license conditions.

6.11 Residual Environmental Impacts

It is predicted that there would be WQO exceedance at the non-gazetted beach at Lung Kwu Sheung Tan without applying any mitigation measures. However, no exceedance will occur if the deployment of the proposed mitigation measures is in place during dredging and filling works (see Table 6.15). Therefore, it is expected that no residual environmental impacts will result from the construction works.

Given the immediate dilution of the cooled water discharges from the terminal outfall and that the limited volume of sewage generated would be treated on site before being discharged in accordance with the EPD’s required standards, residual environmental impacts during the operation phase are not expected.

6.12 Cumulative Impacts

At present there are no committed projects that could have cumulative impacts with the construction of the terminal at Black Point.

6.13 Conclusions

This Section of the EIA has described the impacts on water quality arising from the construction and operation of the proposed LNG terminal. The purpose of the assessment was to evaluate the acceptability of predicted impacts to water quality.

Computer modelling has been used to simulate the loss of sediment to suspension during the construction phase and the impacts due to cooled water discharges during the operation phase. The results and findings of the computer modelling have been provided and summarized.

Potential impacts arising from the proposed dredging works are predicted to be largely confined to the specific works areas. The predicted elevations of suspended sediment concentrations are transient in nature and not predicted to cause adverse impacts to water quality at the sensitive receivers.

During the operation phase, adverse impacts to water quality are not expected to occur as the area affected by the cooled water discharge is extremely small and in the immediate vicinity of the discharge point.

([1]) It was confirmed with the Airport Authority that the WQOs were suitable to be used as the criterion for the intakes at the Airport.

([2]) City University of Hong Kong (2001) Agreement No. CE 62/98, Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment, Final Report, for the Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government.

([3]) ERM – Hong Kong, Ltd (2002) EIA for the Proposed Submarine Gas Pipeline from Cheng Tou Jiao Liquefied Natural Gas Receiving Terminal, Shenzhen to Tai Po Gas Production Plank, Hong Kong. Final EIA Report. For the Hong Kong and China Gas Co., Ltd.

([4]) Maunsell (2001) EIA for Tai Po Sewage Treatment Works - Stage V. Final EIA Report. For Drainage Services Department, Hong Kong SAR Government.

([5]) ERM – Hong Kong, Ltd (2000) EIA for Construction of an International Theme Park in Penny's Bay of North Lantau together with its Essential Associated Infrastructures - Environmental Impact Assessment. Final EIA Report. For Civil Engineering Department, Hong Kong SAR Government.

([6]) Her Majesty's Inspectorate of Pollution (HMIP) (1994). Environmental Economic and BPEO Assessment Principals for Integrated Pollution Control.

([7]) Maunsell (2002). EIA for Decommissioning of Cheoy Lee Shipyard at Penny's Bay. For Civil Engineering Department, Hong Kong SAR Government.

([8]) ERM – Hong Kong (1997). EIA for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit. For Civil Engineering Department, Hong Kong SAR Government.

([9]) Maunsell (2001). EIA for Wanchai Development Phase II - Comprehensive Feasibility Study. For Territory Development Department, Hong Kong SAR Government.

([10]) United States Environmental Protection Agency (2006). National Recommended Water Quality Criteria.

([11]) Australian and New Zealand Environment and Conservation Council (1992). Australian Water Quality Guidelines for Fresh and Marine Waters.

([12]) Salazar, M.H. and Salazar, S.M. (1996). "Mussels as Bioindicators: Effects of TBT on Survival, Bioaccumulation, and Growth under Natural Conditions" in Organotin, edited by M.A. Champ and P.F. Seligman. Chapman & Hall, London.

([13]) ERM - Hong Kong Ltd (1999). EIA for 1,800 MW Gas-fired Power Station at Lamma Extension. Final EIA Report. For the Hongkong Electric Co., Ltd.

([14]) ERM-Hong Kong, Ltd (2004) Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/East of Sha Chau Area. Agreement No. CE 12/2002 (EP). Environmental Impact Assessment and Final Site Section Report, for Civil Engineering and Development Department, Hong Kong SAR Government.

([15]) Scott Wilson (2003). Extension of Existing Landfills and Identification of Potential New Waste Disposal Sites. For the Environmental Protection Department, Hong Kong SAR Government.

([16]) ERM-Hong Kong, Ltd (1993). EIA of the Proposed 6000MW Thermal Power Station at Black Point: Key Issue Assessment-Marine Water Quality, Final Report, prepared for Castle Peak Power Company Limited.

([17]) AFCD (2005). Marine Park Water Quality Report. Web site: www.afcd.gov.hk.

([18]) LCEL and UCEL are Dredged/Excavated Sediment Quality Criteria for the Classification prescribed under ETWBTC No 34/2002 and are presented in Table 7.3.

([19]) ERM-Hong Kong, Ltd (1998). Fisheries Resources and Fishing Operations in Hong Kong Waters. Final Report. For the Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government.

([20]) City University of Hong Kong (2001) Agreement No. CE 62/98, Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment, Final Report, for the Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government.

([21]) City University of Hong Kong (2001) Op Cit.

([22]) ERM – Hong Kong, Ltd (2002) EIA for the Proposed Submarine Gas Pipeline from Cheng Tou Jiao Liquefied Natural Gas Receiving Terminal, Shenzhen to Tai Po Gas Production Plank, Hong Kong. Final EIA Report. For the Hong Kong and China Gas Co., Ltd.

([23]) ERM - HK Ltd (1997). EIA for Disposal of Contaminated Mud in the East of Sha Chau Marine Borrow Pit. For Civil Engineering Department of the SAR Government.

([24]) Mouchel (2002). EIA for Permanent Aviation Fuel Facility. For Hong Kong Airport Authority.

([26]) Langford, TE (1983) Electricity Generation and the Ecology of Natural Waters. Liverpool University Press, Liverpool.

([27]) ERM - Hong Kong, Ltd (1999) EIA for a 1,88MW Gas-fired Power Station at Lamma Extension. Final EIA Report. For The Hongkong Electric Co., Ltd.

([28]) Technical Memorandum for Effluents, Section 21 Water Pollution Control Ordinance, Cap 358.

([29]) It should be noted that the Black Point site is not the preferred option (see Part 4 of the EIA Report) and hence the details of silt curtain will not be provided at this stage. Should the site be further pursued, details of silt curtain will be provided to EPD for approval prior to the commencement of works.

6 Water Quality Assessment