10. FISHERIES IMPACT

10.1 Introduction

Scope

10.1.1 This chapter reports the fisheries impact assessment study (FIA) of the SWC assignment. The objectives of the fisheries impact assessment study include:

· to establish a fisheries baseline for the assessment area, focusing on identified key areas and key resources;
· to assess the implications of the project components, individually and collectively, with reference to the baseline;
· to develop feasible and effective mitigation measures for significant impacts; and
· to determine whether residual, post-mitigation impacts are acceptable, and thus whether the project as a whole is acceptable.

10.1.2 The Assessment Area for fisheries impact assessment, as stipulated in the Study Brief, is the same as that for water quality impact assessment, i.e. Deep Bay Water Control Zone. A terrestrial area covering 500m either side of the proposed bridge alignment or the area likely to be impacted by the project was surveyed for ecological impact assessment. Fishponds within this Study Area for terrestrial ecology were also assessed for fisheries impacts.

10.1.3 This chapter summarises findings of literature review, field surveys, aerial photographic surveys and side-scan sonar surveys. Based upon these sources this chapter identifies and assesses potential impacts to commercial fisheries from the components of the proposed project, outlines potential mitigation measures; and assesses the acceptability of residual impacts.

10.1.4 This chapter is based upon the preferred alignment option selected and recommended during the present EIA study (i.e. S-curve bridge) (Figure 10.1). Details of the alignment option selection please refer to Chapter 4 of this EIA Report. .

10.2 Environmental Legislation, Policies, Plans, Standards and Criteria

10.2.1 HKSAR Government ordinances and regulations relevant to this fisheries assessment include the following:

· the Fisheries Protection Ordinance (Cap. 171) and its subsidiary legislation, the Fisheries Protection Regulations
· Marine Fish Culture Ordinance (Cap. 353) and associated subsidiary legislation;
· The Environmental Impact Assessment Ordinance (Cap. 499) and the associated Technical Memorandum on Environmental Impact Assessment Process ("the TM")

10.3 Existing Environment and Fisheries Sensitive Receivers

Study Methodology

Literature Review

10.3.1 A literature review was undertaken to determine the existing conditions of fisheries in the Assessment Area, and to identify practices, areas and species of potential fisheries importance which may be affected by the project. This review included Government and private sector reports, as well as unpublished information, as follows:

· Port Survey 96/97 conducted for AFD (AFD 1998)
· AFCD annual reports (AFD 1991 - 2000)
· Feasibility study for additional cross-border links Stage 2: Investigations on environment, ecology, land use planning land acquisition, economic/financial viability and preliminary project feasibility/preliminary design (Mouchel 1997, 1998, 1999) (hereafter referred to as "Crosslinks2")

10.3.2 The commercial marine fishery in Hong Kong is composed of capture fisheries and culture fisheries. Port Survey 96/97 (AFD 1998) which provided the most updated data and statistics on inshore capture fisheries in Hong Kong, was consulted to assess capture fisheries impacts, while the AFCD annual reports from 1991/1992 to 1999/2000 were consulted to assess culture fisheries impacts..

10.3.3 The results of the Crosslinks2 study (Mouchel 1997, 1998, 1999) also provided valuable baseline information on fisheries conditions in the SWC Assessment Area.

Field verification surveys

10.3.4 Field verification surveys were conducted between Lau Fau Shan and Sheung Pak Nai in the Study Area for terrestrial ecology to provide information on two issues relevant to fisheries:

· Fishponds from Ngau Hom Shek to Sheung Pak Nai
· Oyster culture beds and rafts near Lau Fau Shan

10.3.5 The status of fishponds (active versus inactive) was evaluated based upon management conditions of the ponds, the presence of fish farming materials and/or equipment, and fish farming activities.

10.3.6 Estimation of the extent of oyster beds, counting of oyster rafts and plotting of their locations were initially conducted from high-elevation points within the assessment area. Later, aerial photographs were used because they were found to be a more reliable tool for mapping oyster beds and counting oyster rafts, and updated aerial photographs were readily available. Field verification surveys were then focused on fishponds rather than oyster beds.

Aerial photographs

10.3.7 Aerial photographs of the Hong Kong coast of Deep Bay were taken on 2 and 3 Jan. 2002 during low tides in the morning (0.1 mCD at 8:04 a.m. on 2 Jan. 2002 & 0.1 mCD on 3 Jan. 2002). Photographs were taken from an altitude of 1500 ft. The surveyed area covered the coastal area, the intertidal area and the subtidal area from Tsim Bei Tsui to Ha Pak Nai.

10.3.8 These aerial photographs were used for counting and mapping of:

· Oyster culture beds and rafts from Tsim Bei Tsui to Ha Pak Nai that represent the oyster farming industry within the assessment area
· Fishponds from Ngau Hom Shek to Sheung Pak Nai

10.3.9 Orthophotos based upon the above aerial photographs were prepared for the area within 500m of either side of the alignment. Orthophotos rectify the radial distortion error inherent in aerial photographs and thus enable more accurate measurement and mapping.

Side-scan sonar surveys

10.3.10 A side-scan sonar survey was conducted in February 2002, which was planned to cover the seabed within 500 m from each side of the preferred alignment within HKSAR waters (500m boundary in Figure 10.4).

10.3.11 Previous studies had demonstrated the accuracy of side-scan sonar by correlating with aerial photos and confirmation by divers (Binnie 1984). They proved that an indication of the density of oyster cultches could be derived from the side-scan sonar traces. This technique, however, could not distinguish between live and dead oysters, or between cultches occupied versus unoccupied by oysters (EGS 1987a).

10.3.12 The objectives of the side-scan surveys for the SWC project were to determine the extent of oyster beds and oyster rafts, especially in the subtidal zone and the part of the intertidal zone reachable by an out-board. Co-ordinates of floating oyster rafts were also recorded during the surveys.

10.3.13 Due to the limitation of the vessel, the side-scan sonar surveys did not cover the entire intertidal zone within the planned surveyed area (the out-board could not enter the shallows near the shore line) (Appendix 10A).

10.3.14 Eight categories of seabed features were defined with reference to previous side-scan sonar surveys for other projects such as Tin Shui Wai Development (EGS 1987b) (Appendix 10A):

· Large Well-Organised Oyster Farms (New)
· Organised Oyster Farm (Old)
· Disorganised Oyster Farms or Scattered Targets
· Well-organised Artificial Objects-Cluster
· Well-organised Oyster Cluster
· Ditch on seabed
· Featureless areas with trawl mark
· Seabed with high reflection

Results

Recognised/Designated sites of fisheries importance

10.3.15 The Deep Bay Water Quality Control Zone covers five Fishing Areas, i.e. Fishing Area 45, 46, 47, 48, and 49 (Figure 10.2). Although Fishing Area 50 is within mainland waters, it is also described here to provide a more complete view on capture fisheries in Deep Bay. Thus the assessment area for fisheries impacts includes Fishing Areas 45-50 (Figure 10.2).

10.3.16 There are no Fish Culture Zones within the assessment area.

10.3.17 There is no gazetted oyster farming site in Hong Kong. However, this practice has long existed on the mudflat in Deep Bay. Floating oyster rafts were also found in this area. In Marine Water Quality (EPD 2001b), this area is indicated as a Shellfish Culture Ground.

10.3.18 Other recognised or designated sites of importance to capture or culture fisheries in the vicinity of the alignment include:

· Oyster culture beds and rafts from Lau Fau Shan to Pak Nai(Figure 10.3)
· Fishponds from Ngau Hom Shek to Sheung Pak Nai (Figure 10.7)

Existing Conditions

10.3.19 The alignment is located in the western estuarine zone of Hong Kong waters, to the west of the transitional central and oceanic eastern waters (Morton 1990). The seabed of Deep Bay is shallow, nowhere deeper than -6m CD. The waters near the alignment are very sheltered and protected from wave and current action.

10.3.20 The fisheries assessment area, i.e. Deep Bay Water Control Zone, can be broken down into two parts, Deep Bay Inner and Outer Subzones. The assessment area is characterised by shallow, muddy-bottomed, tidally-influenced estuarine waters with marked seasonal variations in temperature, salinity, and volume of flow.

Water quality

10.3.21 Deep Bay lies on the east side of the Pearl River Estuary, and its administration is shared by HKSAR and Mainland governments. It is a long (approx. 17 km), shallow bay fed by the Shenzhen River, Yuen Long River and Dasha River, and is also heavily influenced by the Pearl River (HKGEPLG 1992, CGEDC 1996b). The area of Deep Bay is 115 km2, with an average water depth of 2.9 metres (CGEDC 1996b). The bay slopes downward from east to west, and water depth in Outer Deep Bay is greater than Inner Deep Bay (HKGEPLG 1992). Outer Deep Bay has a predominantly sandy substrate, while the substrate in Inner Deep Bay is almost exclusively mud (Mott, Hay and Anderson 1987). One main channel runs from the mouth of the Shenzhen River across the mudflats roughly westward toward Outer Deep Bay. Other shallower channels also cross the mudflats of Inner Deep Bay.

10.3.22 Deep Bay is a brackish estuary. Salinity levels fluctuate seasonally, with highest levels (26-32 ppt) between November and February and lowest levels (5-15 ppt) during the wet season when freshwater influx from the Shenzhen River and other catchments increases (Peking University undated). The shallowness of the bay prevents stratification of water layers during the wet season (HKGEPLG 1992). There is a marked salinity gradient from the head to the mouth of Deep Bay (Binnie 1984).

10.3.23 Deep Bay is heavily polluted with domestic, industrial and agricultural waste, and also subject to heavy sedimentation from both its own catchment and the Pearl River. Wastewater discharge and runoff from Shenzhen into the Bay averages 169 million m-3 per year, of which half is industrial wastewater and almost one third domestic sewage (CGEDC 1996b). Most of this discharge enters via the Shenzhen River and other watercourses at the top end of Inner Deep Bay. The HKSAR's two landward water quality sampling stations in Deep Bay have regularly failed to meet the HKSAR Government's Water Quality Objective (WQO) for dissolved oxygen since monitoring began in 1986 (Mouchel 1997). The three landward Deep Bay stations have failed to meet the WQO for unionised ammonia since 1986 (ibid.). All Deep Bay stations have failed to meet the WQO for total inorganic nitrogen since 1986, though levels are higher in Outer Deep Bay than Inner Deep Bay (ibid.). Sampling stations in the Inner Bay also failed to meet Mainland standards for dissolved oxygen and chemical oxygen demand (CGEDC 1996b). Water quality in Outer Deep Bay is generally better, presumably due to the greater distance from pollution sources in the Inner Bay and the influence of marine waters.

10.3.24 Deep Bay is sheltered and relatively slow-flushing. It has been estimated that a pollutant input takes an average of 15 days to leave the bay. An increase in pollution from the Shenzhen River and other local feeders has been documented in recent decades (Leung et al. 1975, Anon. 1988a, Young and Melville 1995). While livestock waste discharges from the HKSAR are believed to be declining due to the Government's livestock waste collection and treatment initiatives, other sources, notably industrial discharges from the Mainland, have been increasing. Human population levels are also increasing on both sides of the border, though both the HKSAR and Shenzhen governments are making efforts to keep pace by installing or upgrading sewage treatment systems (HKGEPLG 1992).

10.3.25 The Deep Bay Water Control Zone (WCZ) had the poorest water quality among all WCZs in Hong Kong, and the highest faecal coliform counts (EPD 2001b). These pollution levels are most likely due to increasing urbanisation in the Deep Bay catchment in Hong Kong and Shenzhen, and associated discharge of untreated sewage.

10.3.26 Inner Deep Bay had the poorest water quality in the territory in 1998 (EPD 2001b), with high E. coli, total inorganic nitrogen (TIN) and low dissolved oxygen (DO). Of all WCZs, it was the only one which failed to achieve full compliance with the unionised ammonia objective in 1998 (ibid). Deep Bay WCZ also ranked lowest among the four major areas of WQO non-compliance, based upon the statistics of recent years. The decrease in DO observed at the water quality sampling stations inside Deep Bay in 1998 revealed that hypoxia had become more severe in inner Deep Bay. Such pronounced water quality deterioration may pose a threat to the sensitive marine organisms in Deep Bay.

10.3.27 Deep Bay was one of two areas with worsening faecal pollution in the territory in 1998. Deep Bay is receiving between 10 - 100 times (depending on the type of pollutant) more pollution than it can assimilate each day (EPD 2001a). The bay is unable to assimulate these pollutants naturally. This is especially threatening for a semi-enclosed water body where circulation is slow. The water in the outer bay was less affected by pollution inputs from the catchment than the water in the inner bay.
Capture fisheries

10.3.28 Recent detailed data on HKSAR capture fisheries in the assessment area were taken from the Port Survey 96/97 (AFD 1998). The assessment area covers six Fishing Areas, i.e. Fishing Areas 45 (Black Point), 46 (Nim Wan), 47 (Pak Nai), 48 (Lau Fau Shan), 49 (Tsim Bei Tsui) and 50 (Shum Chun Wan) (Figure 10.2). The bridge alignment falls within Fishing Area 48 (Lau Fau Shan), while the HKSAR landing point is located on the boundary between Fishing Area 48 and Fishing Area 47 (Pak Nai).

10.3.29 Fishing Area 48 is compared here with Fishing Areas 45 (Black Point), 46 (Nim Wan), 47 (Pak Nai), 49 (Tsim Bei Tsui), and 50 (Shum Chun Wan), thereby covering all of Deep Bay. For Fishing Area 47 (Pak Nai), fishing grounds inside would not be affected since only the landing point of the bridge contacts its boundary. Data on capture fisheries include fish production and economic values as reported in the Port Survey 96/97. These statistics are shown in Table 10.1.

10.3.30 The major capture fishery grounds within Deep Bay extend from Lau Fau Shan to Nim Wan. On the HKSAR side, over 60 small (<15 m) boats fished the Bay in the late 1980s, producing an estimated 71 tonnes of adult fish and 2,000 tails of fry (Mott, Hay and Anderson 1987). Fishermen primarily used gill nets, while hand lines/long lines were used to a lesser extent (ibid., HKGEPLG 1992). Catches in the Bay were described by a Mainland source as very small in quantity (CGEDC 1996a).

10.3.31 The most important fisheries species in terms of weight of catch in Deep Bay were Mangrove Crab Scylla serrata, Lionhead Collichthys lucidus, Flathead Platycephalus indicus, the prawn Parapenaeopsis hungerfordi, Jinga Shrimp Metapenaeus affinis, tongue sole Cynoglossus semilaevis and the croakers Argyrosomus spp. and Johnius belengeri. Species of secondary importance included Japanese Prawn Penaeus japonicus, White Herring Ilisha elongata, Mantis Shrimp Oratosquilla oratoria and tongue sole Cynoglossus macrolepidotus (AFD 1998). Other species reported to be caught in Deep Bay are Hilsa Herring Hilsa reevesii, Grey Mullet Mugil cephalus, Mackerel Scomberomorus sp., croakers Sciaenidae spp., Yellow-finned Seabream Mylio latus, sea perch and snapper, and the shrimps Penaeus penicillatus and Penaeus monodon (MHA 1987, HKGEPLG 1992). All areas in Deep Bay reported zero fry production in the 96/97 Port Survey, indicating that if Deep Bay serves as a nursery ground, it harbours either species of little commercial value or fry in concentrations too low to make fry collection economically viable.

10.3.32 Small-vessel fisheries on the HKSAR side of Deep Bay produced an estimated annual catch of 71 tonnes of adult fish and 2,000 tails of fry in the late 1980s (MHA 1987). The corresponding numbers for all types of vessels in 1996/97 were 73 tonnes of adult fish and 0 tails of fry (AFD 1998). Overall, the 96/97 Port Survey ranked Deep Bay 12th of 12 HKSAR fishing sectors in terms of production of adult fish and value of catch. Deep Bay was not ranked for fry production because no fry production was reported (AFD 1998). This accords with a Mainland source which described catches in the Bay as very small in quantity (CGEDC 1996a).

10.3.33 Deep Bay is recognised by the Mainland as an important nursery ground. The Mainland part of Deep Bay, which is also covered by the six Fishing Areas listed above, falls within a Juvenile Fish and Shrimp Protection Area declared in Lingdingyang. The closed fishing season for this area extends from March 1 to May 31 each year (SCSFRA 1985). Only lift nets may be used for fishing in the Mainland part of the Bay (Young and Melville 1990).

10.3.34 Although the catch of adult fish in Fishing Area 48 was the second highest among the 6 Fishing Areas, its ranking among all fishing areas in Hong Kong was very low (161th). Fishing Area 48 was also the most productive Fishing Area in the Assessment Area on the basis of adult fish caught per hectare. In terms of value of catch Fishing Area 48 ranked second among the six Fishing Areas. However, the average value of catch per ha in Area 48 (and Fishing Area 49) was less than 50% the Hong Kong average. Catches of adult fish (tonnes per ha) for Fishing Area 47 were about 10% the Hong Kong average. Thus these fishing areas were not productive in terms of quantity or value of fish caught. No fry capture operations have been reported from any of the six Fishing Areas.

10.3.35 The combined area of these six Fishing Areas is 13,348.83 hectares, or 7.3 % of the total fishing area in Hong Kong. The average value of catch per ha for the whole assessment area was less than one third the Hong Kong average (510.89 vs 1,892.12), while catches of adult fish (tonnes per ha) were only 7% the Hong Kong average (6.59 vs 97.26). This indicates that the assessment area was a poor fishing ground both in terms of quantity and value of catch.

10.3.36 As shown in Table 10. 1, the area of Fishing Area 48 accounts for 1.16% of the total fishing area of Hong Kong, however, the adult fish catches recorded from these waters only account for 0.12% of the catch of the Hong Kong fishery. This demonstrates that Fishing Area 48 is not productive. The catches account for only 0.54% of the value of the Hong Kong fishery, demonstrating that the catches from Fishing Area 48 are not of high value.

10.3.37 Out of 189 fishing areas in Hong Kong waters, Fishing Area 48 was ranked by the 96/97 Port Survey as 142th in terms of production value per ha, 161th in terms of adult fish production per ha. All six Fishing Areas in the assessment area were ranked higher than 100th in Hong Kong in both production value per ha and adult fish production per ha.

10.3.38 The nearest fishing port to the site is at Lau Fau Shan, about 1.7 km northeast of the proposed bridge landing point. The second nearest fishing port is at Castle Peak Bay, which is about 8 km to the south and sheltered by the land mass. Fishing grounds cover most of the open waters around the Project Area, except for shipping fairways. The Port Survey 96/97 reported that Fishing Area 48 was fished by about 42 vessels of up to 15 m, and by about 9 vessels over 15 m in length. The Lau Fau Shan Home Port is very small and is the base for 15 vessels that are mainly involved in oyster culture and green crab (Scylla serrata) catching.

10.3.39 Within HKSAR waters, the highest yields for local fisheries were mainly derived from the eastern and northeastern coasts as indicated in the AFD Port Survey 96/97. While the western waters were comparatively less productive.

10.3.40 As reported in the Port Survey 96/97 (AFD 1998), the catches from the Deep Bay sector were ranked the lowest of the 12 fishing sectors in Hong Kong. These figures demonstrate that the Deep Bay sector which covers Fishing Areas 45, 46, 47, 48, 49 and 50 is of low importance to capture fishing operations in Hong Kong.

10.3.41 In summary, on the basis of their ranking, and records of fisheries operations in the waters surrounding the Project Area and also within the whole Deep Bay, indicate that the area is of low importance to the Hong Kong fishery.

Table 10.1 Data on HKSAR Capture Fisheries in the Study Area (Source: AFD 1998)

Oyster farming

10.3.42 The oyster beds and rafts near Tsim Bei Tsui and Ha Pak Nai are the only marine culture fisheries sites near the Project Area.

10.3.43 Two species of oyster are cultured in Deep Bay: Crassostrea gigas and C. rivularis. Most of the oysters are cultivated from spat collected in Deep Bay itself or imported from other parts of the Pearl River Estuary. Oysters are grown to market size on cultch (or "culch"), a fixed substrate embedded in the mud. A cultch may be a concrete post, concrete tile, concrete block or a stone. Recently the most common type of cultch is a bamboo stick coated with concrete. Cultches are inserted into the tidal mudflats or suspended from oyster rafts near the middle of the Bay.

10.3.44 Though they have no direct relation with the settlement and growth of oysters, the mudflats provide a substrate for the deployment of oyster cultches. Cultches on mudflats are rearranged 2 to 3 times a year to maintain the angle favouring oyster growth. The average diameter of each oyster cultch with oysters is about 0.2m. The spacing between rows of cultch in oyster beds is about 1m, and the spacing between two oyster cultches is about 0.3m. Normally it takes about three years for the oysters to mature to a marketable size.

10.3.45 In the subtidal zone, rafts are used for oyster cultivation. Most oyster rafts measure about 80 - 96 m2, while some are smaller in size (about 24m2). Binnie (1984) reported a much larger size range, i.e. 84 to 110 m2, for the rafts in mainland waters. The rafts are constructed of bamboo or wood poles with floats attached. Oysters are suspended from the rafts such that the oysters are above the seabed even during low tide. This system enhances the contact time period of oysters with the water and thus reduces the growth time in comparison with oysters on cultches in the intertidal zone.

10.3.46 The oyster industry in Deep Bay has been seriously threatened by the poor water quality in inner Deep Bay. Oyster production has declined considerably in Deep Bay due to high pollution loads and disputes over land rights (HKGEPLG 1992; CGEDC 1996a; Mouchel 1997, 1998, 1999.).

10.3.47 Of over 3,000 ha on the HKSAR side of the Bay, only 600 ha were reported in active cultivation in a 1992 report (Anon. 1988b, HKGEPLG 1992).

Table 10.2 Hong Kong local oyster production and value (source: AFCD annual reports)

10.3.48 The 1997 oyster harvest from HKSAR oyster beds was estimated at 60 tonnes, compared to 120 tonnes in 1992 (AFD 1992 - 1998). Local oyster farmers produced fresh oyster meat valued at $3.7 million in 1997. These figures represent a 14 percent decrease by weight and a decrease of 16 per cent by value compared with the preceding year (AFD 1992 - 1998). The local oyster production for 1997 and -1998 are 66 and 64 tonnes respectively, while that for 2000 is 76 tonnes.

10.3.49 Local production of oysters represents only a small proportion of the total oysters consumed in Hong Kong. The remainder are imported, mainly from China. Hong Kong local oyster production has been exceeded by imports from mainland and other countries since the 1970s, and a large proportion of the output from the mainland oyster industry is exported to Hong Kong (Binnie 1984).

Oyster beds

10.3.50 Information on the current extent of mudflats occupied by oyster beds within Deep Bay was provided by three sources, i.e. aerial photos, field visits and side-scan sonar survey. Among these, the aerial photos provided the most direct and detailed information, and thus were the core source of information. Aerial photo results were supplemented by results from field visits and side-scan sonar survey.

10.3.51 The tidal level during the aerial surveys was very low (0.1 mCD on both 2 Jan. and 3 Jan. 2002). This level represents the second lowest tidal level expected in Deep Bay in 2002 (27 and 28 Feb. 2002 were predicted to be lower; i.e. 0.0 mCD). Based upon the location of the tideline as shown on the January 2002 aerial photographs, the mudflat in the area extends about 600 m to 1000m from the coastline, varying according to location. Distribution of oyster beds on the intertidal mudflats from Tsim Bei Tsui to Ha Pak Nai covered by the aerial photographic surveys dated 2 and 3 Jan. 2002 is shown in Figure 10.3. The size of intertidal mudflats within this area was estimated to be about 747 ha, of which about 176 ha (approximately 24%) were occupied by oyster cultches.

10.3.52 Figure 10.4 shows the distribution of oyster beds within 500m of the proposed bridge alignment, also based upon the aerial photographs dated 2 and 3 Jan. 2002, but with rectification of orthophotos (Figure 10.5) and confirmation from side-scan sonar surveys. About 128 ha of mudflats lie within 500m of the alignment. About one third of that area (48 ha) is currently occupied by oyster beds. Since most oyster beds were concentrated towards the eastern edge of the 500m boundary, only about 5.37 ha of oyster beds were located within the 50m works boundary on each side of the alignment.

10.3.53 In early January 2002 there were several oyster beds just outside the proposed landing location at Ngau Hom Shek and directly in the path of the bridge alignment. The oyster beds at Ngau Hom Shek were not present on the site in August 2001 (Figure 10.6a), but appeared on the site beginning in September 2001. Figure 10.6b shows a photo taken in November 2001, in which the area of mudflats still clear in August 2001 was occupied by oyster cultches. The expansion of oyster beds continued as shown in Figure 10.6c which was taken in March 2002. Some oyster beds were found further southeast along the coastline including Ngau Hom Sha and Ha Pak Nai from aerial photos. Since September 2001 the oyster beds also expanded towards Lau Fau Shan.

10.3.54 The side-scan sonar survey was conducted in early February 2002. This chapter mainly utilises the results from the side-scan sonar survey which covered the entire area within 500m of the alignment. The surveyed area is shown in Figure 10.4.

10.3.55 The survey covered 500 m on each side of the alignment from the intertidal zone up to the boundary of Mainland and HKSAR waters. Since the surveys were conducted during high tide, they also covered the maximum extent of the intertidal zone reachable by a shallow-draft out-board. In the surveyed section of intertidal zone, three types of side-scan sonar images were recorded: "Large well-organised oyster farms (new)", "Organised oyster farms (old)", and "Disorganised oyster farms or scattered targets" (Appendix 10A). The side-scan sonar information was compared with the mapping result from aerial photos. It was found that the locations of those "Large well-organised oyster farms (new)" matched with the most seaward oyster beds identified on aerial photos. Since most oyster beds were located landward of the area covered by the side-scan sonar survey, the extent and distribution of oyster beds could only be mapped based upon the results from aerial photos.

10.3.56 In the subtidal zone, a number of small "Well-organised Artificial Objects-Cluster" and "Well-organised Oyster Cluster" were identified in the side-scan sonar survey (Appendix 10A and Appendix 10B). Given the similarity in the sizes, locations, and distribution patterns of the above two sonar-mapped categories with those of the oyster rafts recorded during the sonar surveys (Appendix 10B), we suspected that these two categories were probably the locading stones under the floating jerricans of the oyster rafts and the oyster clusters suspended with string from the oyster rafts. Further seaward from these small subtidal oyster beds to the boundary of mainland and HKSAR waters, no other oyster beds were found. Although it was reported in previous studies that mainland oyster farmers dumped stones, concrete blocks or old oyster shells in the middle of Deep Bay, and, without any subsequent management harvested any oysters that naturally colonised, no such unorganised oyster beds were found during the side-scan survey within Hong Kong waters.

Table 10.3 Summary of data on mudflats, oyster beds and oyster rafts.

Oyster rafts

10.3.57 Distribution of oyster rafts within Deep Bay was mapped using aerial photographs dated 2 and 3 January 2002 (Figure 10.3). There are two major groups of rafts with respect to the locations. A smaller group was concentrated to the northeast of Lau Fau Shan, while a larger group was just outside the coastline of Ngau Hom Shek.

10.3.58 Figure 10.4 shows the distribution of oyster rafts within 500m of the alignment, based upon aerial photographs dated 2 and 3 January 2002. The oyster rafts are the only marine culture fisheries in the subtidal zone near the alignment.

10.3.59 There were 258 oyster rafts anchored in the subtidal zone from Tsim Bei Tsui to Ha Pak Nai. Of these, 149 rafts were within 500 m of the proposed bridge alignment.

10.3.60 The two sets of aerial photos showed different numbers of rafts within the proposed 50 m marine works area: There were 19 oyster rafts located within the 50m marine works area in the 2 Jan. 2002 photos, while there were 22 in the 3 Jan. 2002 photos. According to the co-ordinates recorded during the side-scan surveys, there were 23 oyster rafts located within the 50m marine works area. This number was considered to be the most updated and most accurate, due to the accuracy of the digital global positioning systems (DGPS).

Fishponds

10.3.61 Fishponds were located in the lower elevations of the terrestrial part of the assessment area, in a nearly continuous band along the coast of Deep Bay.

10.3.62 Historically, Inner Deep Bay was most likely dominated by mangrove wetlands. With the advent and spread of human populations, mangroves were converted to man-made wetlands (paddies, shrimp ponds and fish ponds) or to dry land (Irving and Morton 1988). Fish ponds in the HKSAR's Deep Bay catchment, very limited in extent before World War II, began to replace paddies, shrimp ponds and other less profitable types of agriculture around the middle of the 20th century (ibid.). Fish ponds probably now account for the largest wetland area in the North-west New Territories, excluding Deep Bay itself. Deep Bay fish ponds probably peaked in area during the 1970s or 1980s. In recent years, these ponds have been increasingly subject to conversion for other, more lucrative landuses, including open storage. Development projects including roads, railways, flood control schemes and housing developments have also accounted for a certain amount of pond loss.

10.3.63 Fish ponds and agricultural land at Pak Nai are ranked as Grade A by the Agriculture, Fisheries & Conservation Department (AFCD) Categorization of Agricultural Land. The AFCD ranking recorded 31 ha of fish ponds at Sheung Pak Nai and Ha Pak Nai (AFD 1995). The AFCD categorization delineates a continuous coastal band of Grade A or B agricultural land along the south shore of Deep Bay, from Mai Po to Nim Wan (ibid.).

10.3.64 Figure 10.7 shows the distribution and status of the fishponds between Ngau Hom Shek and Ha Pak Nai. Within this area, there are 18 ha of fishponds, with 12 ha active and 6 ha abandoned.
10.3.65 All active fishponds within the terrestrial assessment area for the present project were located close to Ha Pak Nai and Ngau Hom Sha. No active or abandoned fishponds would be directly affected by the proposed alignment or works areas.

Discussion

10.3.66 Aerial photos and side-scan sonar are two common methods that were used in studying the oyster industry in previous studies including the "Tin Shui Wai Development"(Binnie 1984).

10.3.67 There are over 1000 ha of mudflats within Deep Bay. About 75% of them extend from Tsim Bei Tsui to Ha Pak Nai (747 ha) and are suitable for oyster farming. About 176 ha are currently occupied by oyster cultches, scattered throughout the area but concentrated near Lau Fau Shan.

10.3.68 Of the 48 ha of existing oyster beds within the assessment area (extending 500m from each side of the alignment), only 5.4 ha fell within the 50m marine works area.

10.3.69 Side-scan sonar surveys identified no subtidal oyster beds within the 500m boundary, nor within the 50 m marine works area.

10.3.70 Of the 258 oyster rafts in Deep Bay, 149 were located within the 500m boundary. Different numbers of oyster rafts within the 50m marine works area were derived from the 2 Jan. 2002 aerial photos, 3 Jan. 2002 aerial photos and results of side-scan sonar surveys. The number from the side-scan sonar survey, i.e. 23 oyster rafts, was considered to be the most updated. The variation in counts demonstrated that the locations of oyster rafts are not fixed.

Sensitive Receivers

10.3.71 Based upon the above review of baseline fisheries conditions in the study area, the sensitive fisheries receivers which may be affected by the proposed project have been identified as Fishing Areas 45-50, and the oyster beds and rafts near Lau Fau Shan.

Fisheries Importance

Capture fisheries

10.3.72 Previous studies characterised the fisheries resources within the assessment area as being of low importance relative to other areas of Hong Kong. Catches from the assessment area were composed of mixed species, which are mainly used as fish feed in mariculture.

10.3.73 Fishing Area 48, and other Fishing Areas inside Deep Bay, ranked low relative to other areas in Hong Kong in terms of the catch of adult fish by weight and value, and there are no records of fry collection.

10.3.74 The EIAO TM (Annex 8) states that nursery areas can be regarded as an important habitat types as they are critical to the regeneration and long term survival of many organisms and their population (Annex 8). Although there is no record of fish fry collection in the assessment area, Deep Bay is designated by the Mainland as a Juvenile Fish and Shrimp Protection Area.

Oyster farming

10.3.75 The production of oysters from the Deep Bay area is declining in recent years as shown in Table 10.2 and Section 10.3.48. The annual production has been less than 100 tonnes since 1994. Oyster farming within the assessment area contributes a small proportion of total oyster consumption in Hong Kong since the 1970s (Binnie 1984).

Fishponds

10.3.76 About two thirds of the fishpond area within the Study Area for ecology, i.e. about 12 ha, were active. This represents ±0.8% of the 1,480 ha of fishpond area in Hong Kong. No fishponds would be resumed for the project, and no direct impacts upon fishponds are anticipated. One abandoned fishpond might be affected by the DBL project, but this is outside the demarcation mark of the present project and has ecological rather than economic or industrial implications.

10.3.77 Based upon reviewed literature and the discussion presented above, the current fisheries assessment shows that the fishery resources of the assessment area and adjacent waters are considered of minor and declining importance to the Hong Kong fishery.

10.4 Assessment Methodology

10.4.1 The approach to the fisheries impact assessment process for Shenzhen Western Corridor study is outlined in Section 3.4.6.3 of the Study Brief, which states: "The Study shall review and collate existing information to provide adequate and accurate data for prediction and evaluation of impacts of the Project on fisheries".

10.4.2 Impact assessment methodology follows the guidelines laid down in the TM and the TC. The assessment area was defined as the same as that for water quality impact assessment, i.e. the Deep Bay Water Control Zones as designated under the Water Pollution Control Ordinance (WPCO). Field surveys to verify the operation status of fishponds were designed and agreed with relevant HKSAR Government authorities. The importance of the fisheries resources within the study area was assessed in accordance with the TM.

10.4.3 The fisheries impacts of the project components were assessed individually, then cumulatively with other past, ongoing and proposed projects. Efforts were made to identify feasible mitigation measures which might be developed to reduce the severity of any negative impacts identified. These measures would be described in terms of their scope, programme, feasibility and financial implications during the construction and operation of the project.

10.4.4 Finally, the consultants concluded whether the mitigation measures envisioned could bring the negative impacts of the project and its components within acceptable bounds.

10.4.5 Existing data are adequate to enable assessment of potential impacts upon local fisheries. It was assumed that water quality and sediment flux would be the key issues contributing to fisheries impacts inside Deep Bay. Fisheries impact assessment for the assessment area would therefore rely to a high degree on the findings of water quality and sediment transport modelling.

10.5 Identification of Environmental Impacts

Major Concerns

10.5.1 The major concerns associated with the Project are as follows:

· Temporary and permanent loss of fishing ground, nursery ground, mudflats available for oyster beds, and sea area available for oyster raft anchorage;
· Effects of water quality and sediment transport changes in Deep Bay during construction and operation phases; and
· Disturbance during construction and operation.

10.5.2 Readers are referred to Section 2 of this report for details of the proposed bridge design and construction.

Construction stage

10.5.3 Predominant impacts to fishing operations and resources usually occur through the loss, temporary or permanent, of area which supports fisheries resources and oyster farming operations, and the water quality change in Deep Bay.

10.5.4 During the construction stage, about 43 ha (16 ha in mudflat zone and 27 ha in sea area) will be occupied within HKSAR waters as marine works areas (Figure 10.4). Within the marine works area, no type of fisheries activity including oyster farming by beds and rafts would be possible during the estimated 28 months bridge construction phase. This would constitute a temporary loss of fishing grounds. The 43 ha of work area would constitute a temporary loss of about 2 % of the total fishing ground in Fishing Area 48 (Lau Fau Shan; 2,107.43 ha in area). Given the small percentage of area affected and the typically low production in Deep Bay, this represents a minor impact to the capture fisheries in Deep Bay and in Hong Kong.

10.5.5 This would also constitute a temporary loss of mudflats available for oyster bed deployment and sea areas available for oyster raft anchoring. The subtidal part of the marine works area (Figure 10.4) would not be available for the anchoring of oyster rafts during the construction stage. The 23 oyster rafts currently anchored within the proposed works area would need to be relocated. Because the rafts are anchored, and because unoccupied sea surface area is available within Deep Bay but outside the marine works area, relocation of the affected oyster rafts is practicable. Therefore this impact is considered minor.

10.5.6 The area of mudflat along the south shore of Deep Bay from Tsim Bei Tsui to Ha Pak Nai was estimated to be 747 ha. This estimate was based upon the tideline location on the aerial photographs of 2 & 3 Jan. 2002. This figure represents the total area of HKSAR mudflat available for oyster bed farming. Of the 43 ha marine works area, 16 ha are mudflat (Figure 4, the section of 50m works limit between the tideline and the coastline). This 16 ha mudflat area would not be available for oyster farming during the bridge construction phase (about 28 months), and operation phase. This would constitute a temporary loss of about 2.1 % of potential oyster beds within Deep Bay. Given the fact that approximately 75% of potential oyster beds (mudflats) have not been exploited in the area, the loss of the 16 ha of mudflat, even for a time period longer than the construction phase, would not constitute a severe impact on oyster farming practice. This impact is thus ranked as minor.

10.5.7 The construction of the bridge would not require temporary or permanent occupation of fishponds. The impact upon pond fish culture is thus ranked as insignificant.
10.5.8 Marine water quality - Suspended Solid: Construction of SWC bridge piers would involve dredging in Deep Bay, the bed of which is covered by a deep layer of mud. It could locally affect water quality in the vicinity of the dredging sites. Resuspended sediments could contain contaminants which could enter the water column, while resettled sediments could smother benthic fauna. These water quality impacts could have negative consequences, mostly indirect, for both benthic and pelagic organisms. For the case of unconfined dredging, the potential impacts to the surrounding water may be significant.

10.5.9 Oysters, as estuarine organisms, differ from other sensitive marine organisms (such as corals, for example) in that oysters are well-adapted to high suspended solid levels. Estuaries are the most dynamic among aquatic ecosystems, with considerable fluctuations in salinity and turbidity. Estuarine organisms, including oysters, are particularly resilient and adaptable to these changing environments.

10.5.10 In most cases, suspended sediment associated with dredging and reclamation is the major source of indirect impact to fisheries. The baseline suspended solid conditions in Deep Bay are quite variable, being influenced strongly by seasonal variations, tidal flows, storms, and fishing vessels. Deep Bay organisms are thus adapted to periods of high suspended sediments. The effect of suspended solids is difficult to quantify. In a recent study on marine ecological impact assessment criteria, the standard on suspended solid was selected based upon the no harm dosage for diatoms, rather than upon the actual effect dosage on marine organisms (City University of Hong Kong 2001). The rate, season and duration of SS elevations will determine the type and extent of impacts upon marine organisms.

10.5.11 Impacts of pier excavation and construction would most likely continue for up to 28 months. The severity of impacts will depend upon factors including the number of piers, the number of pier sites being excavated simultaneously, and the depth of the silt layer on the seabed. Works would require approximately 7.5 weeks at each pier site, and for noise control reasons no more than three pier sites would be under construction in the intertidal zone at a given time. The critical period for the construction of bridge piers would be from June 2004 to Sep. 2004. Two pairs of bridge piers would be constructed simultaneously within 600 m from coastline, while 3 pairs would be constructed simultaneously beyond the distance of 600m from the coastline at Ngau Hom Shek, and 3 pairs in subtidal area.

10.5.12 The potential for sediment resuspension in the present project was predicted to be very low, since only limited dredging would be required for pier construction, enclosed rotary piling would be used, and piles would be bored inside casings that are in turn contained within cofferdams surrounded by silt curtains. These measures could effectively prevent any significant increase of suspended solid levels. No release of sediment is normally expected according to the proposed construction method. Impacts will be mitigated to acceptable level. Even in the case of failure of those mitigation measures, effects would be localised in nature due to the slow speeds of water movement in Deep Bay, on the order of 0.2-0.4 m/s.

10.5.13 Sediment plume modelling was conducted to predict the increase in suspended solids in the water column due to the release of sediment from bridge construction. To take a more conservative approach, the potential water quality impacts arising from bridge pier construction within the Hong Kong waters were assessed based on 8 pairs of pier sites (see Section 7 of this report, Water Quality Impact Assessment). Results indicated that no significant elevations of suspended solid due to dredging were found in all modelling cases. None of the elevation in indicator points exceeds 10 mg/L, which was reported in the Mainland EIA that no significant impacts on aquaculture would be resulted. There would be no exceedance of WQO for SS (<30% increase of the background value).

10.5.14 Even during the critical period, water quality modelling indicates that the changes would be minor and there would be no significant adverse impacts to water quality. Impacts on water quality during the entire construction phase would be even lower and therefore acceptable. This in turn indicates the impacts on fisheries during the construction phase would be acceptable. These impacts will be mitigated to acceptable level by the formation of cofferdams to enclose the pier construction sites, the use of enclosed rotary piling during construction, and deployment of silt curtains as needed.

10.5.15 Marine water quality - Contaminants including TBT: Potential releases of contaminants from dredged sediments into the water column during the dredging operations could affect the water quality and aquatic environment near the dredging sites. Besides the major water quality parameters of concern such as suspended solids (SS) levels, resuspended sediments could contain contaminants which could enter the water column. These water quality impacts could have negative consequences, mostly indirect, for both benthic and pelagic organisms.

10.5.16 Elutriate tests were also conducted to estimate the amount of contaminants that would release from the marine sediment during the dredging activities. The tested parameters included heavy metals and organic micro-pollutants (PCBs, PAHs, and TBT).

10.5.17 PAHs and total PCBs were below the detection limits. Other contaminants were of low concentration. Release of copper, zinc, and arsenic from marine sediment was not likely to cause adverse water quality impacts to Deep Bay. The release of these compounds during dredging would be insignificant, except TBT. For TBT, the highest amount released was found at D2 (Figure 7.19), with a value of 1.816 mgTBT/L. The release of TBT from the sediment samples collected at D1, D3 and D4 (Figure 7.19) were also relatively high.

10.5.18 The high release potential of TBT detected at a number of sampling stations is a concern. TBT is highly toxic to various aquatic organisms and may cause skeletal deformities in fish. The effects of TBT on oysters include the reduction in growth rate and reproduction of oysters. His and Robert (1983) reported the effects of TBT on the Pacific oyster (Crassostrea gigas). Abnormal and malformation of Pacific oysters were found at TBT concentrations of 1 mg/L. At TBT concentrations of 0.5 mg/L, there would be numerous larval anomalies. Perturbation in larval food assimilation was at 0.2 mg/L. Exposure to TBT concentrations of 0.1 might result in slow growth and high mortality of larvae. Chagot et al (1990) reported the histopathological changes in digestive gland and gill of Pacific oysters at TBT concentrations of 0.06 mg/L.

10.5.19 The locations of the sediment samples with high release potential of TBT were found near the shoreline at Ngau Hom Shek. Some of the bridge piers are located in these areas. There would be a possibility of release of TBT into the surrounding water if sediment dredging in these areas were not properly controlled.

10.5.20 In the elutriate tests, sediment samples were vigorously agitated in the seawater. This might increase the release of TBT into the seawater resulting in high TBT levels. The real situation at the dredging sites in the present project would be different. Based on the preliminary engineering design, the piles for supporting the bridge sections would be constructed in the form of bored piles. A casing will be driven into the marine sediment layer prior to the excavation of marine sediment inside the casing. The seawater inside the casting will also pumped put to barges before dredging. The casing provides a confined and dry environment to avoid releasing of sediment into the surrounding water. In addition, cofferdams, which are larger than the pile caps of the bridge piers, would be installed at all pile sites prior to carrying out of any dredging works for construction of pile caps. Sediment dredging would then be carried out within the cofferdams. This construction method could minimise the release of TBT into the water column. By adopting these preventive measures, it is considered that dredging even at the locations with high TBT release potential would not cause adverse impact to the aquatic life and acceptable.

10.5.21 Marine water quality - Flushing Rate: Reduction in flushing rate is another concern related to water quality. As described above, a cofferdam larger in size than the bridge pier and pile cap would be constructed at each pier site to mitigate the suspended solid impact and to prevent the release of contaminants in the sediment. The cofferdams themselves, however, would restrict water discharge capacity more than a bridge pier. At the initial stage of the construction works, only some of the bridge piers would be under construction, and thus the overall effect on tidal flow is likely to be lower than the operation phase of SWC, i.e. when all bridge piers are in place. During the critical period of the construction phase (from June 2004 to Sep. 2004), in which eight pairs of piers would be under construction simultaneously, and the rest of the piers have already been completed, the reduction in tidal flow across the bridge alignment is expected to be higher than during the operation phase.

10.5.22 On the other hand, the presence of oyster cultches creates friction to the tidal flow due to the highly irregular surfaces of the oyster cultches and oysters.

10.5.23 During the construction stage, about 43 ha (39m of the alignment and 50m either side of the alignment) will be occupied within HKSAR waters as marine works areas. Within the marine works area, existing oyster beds will be cleared during the bridge construction phase. The area will not be available for oyster farming even after the construction phase.

10.5.24 Though considered as a loss of aquaculture area, the removal of oyster beds within the works area, however, would have positive effect on the water quality during construction phase, i.e. could partially compensate the reduction in discharge capacity caused by the cofferdams, especially during the critical construction period of May 2004 to Sep. 2004, during which eight pairs of piers will be under construction simultaneously.

10.5.25 Even during this period, hydrodynamics modelling results showed that with the clearance of oyster beds, the obstruction to the tidal flow would be reduced. This could counterbalance the reduction in discharge capacity caused by the concurrent construction of bridge piers during the critical period. With the clearance of oyster beds within the works area, it is expected that the hydrodynamic conditions in Deep Bay during the critical period for construction would be improved and would not be much different from the rest of the construction phase. There would be no significant adverse impacts to the tidal flow and water quality during this period. Therefore, impacts on water quality during the entire construction phase would be even lower and would be acceptable. This in turn indicates flushing rate impacts on fisheries during construction phase would be acceptable.

10.5.26 Submarine noise and disturbance: Below the tideline, impacts could be significant during the construction phase if percussive piling methods were used. However, impacts of piling upon benthic and pelagic invertebrates and fish would be temporary, intermittent, and minimised through the use of rotary rather than percussive piling. Noise would result mainly from sheetpiling at each pier location to construct a cofferdam within which rotary piling would take place. Sheetpiling would not be continuous, and would take less than 4 days at each pier site.

10.5.27 Given that the large mass of marine water and the continuing circulation, the construction dust from the construction of the proposed project would not constitute any significant impact on both capture and culture fisheries.

Operation stage

10.5.28 The 40 pairs of bridge piers in HKSAR waters will permanently occupy about 0.22 hectares of seabed, 0.196 ha of which would be in subtidal zone, and 0.024 ha of which would be in the mudflat zone.

10.5.29 Fishing ground loss: The 0.22 ha of seabed loss would constitute a loss of about 0.01 % of the total fishing ground in Fishing Area 48 (Lau Fau Shan, 2,107.43 ha in area). This impact is ranked as minor.

10.5.30 The sea area beneath the bridge will not be available for the anchoring of oyster rafts. Since unoccupied sea area is still available in Deep Bay, this impact is considered minor to the oyster farming industry.

10.5.31 16 ha of mudflat available for oyster farming would be cleared for the construction works, including areas where oyster beds have been sited since August 2001. Oyster farming would not be resumed within this area even the construction has finished. An estimation, based upon the aerial photographs dated 2 & 3 January 2002, showed that the area of mudflat along the south shore of Deep Bay from Tsim Bei Tsui to Ha Pak Nai is 747 ha. This figure represents the total area of HKSAR mudflat available for oyster bed farming. The permanent loss of 16 ha would constitute a 2.1 percent reduction in the potential area for oyster beds within Deep Bay. Due to the small area permanently affected by the bridge, the fact that approximately 75% of potential oyster beds (mudflats) from Tsim Bei Tsui to Ha Pak Nai have not been exploited for oyster farming, and the progressive decline of the oyster culture industry in HKSAR (Table 10.2), the loss would not constitute a severe impact on oyster farming practice. The potential project impacts upon oyster culture are considered minor.

10.5.32 Marine water quality - General water quality: Based on the predicted results in Section 7, the changes in water quality resulting from the construction of bridge piers and reclamation at Dongjiaotou were small. The differences in model predictions between Scenario 1 (the current Deep Bay) and Scenario 3 (Deep Bay with the bridge and the landing point reclamation) are almost indistinguishable at DM1, DM2 and DM3 (EPD's marine water monitoring stations) in all the time series plots. As can be seen in Figure 7.119, the absolute differences of the presented parameters (E. coli, SS, BOD, DO, UIA, TIN and salinity) between the two scenarios were much lower than the ranges of natural fluctuations of them.

10.5.33 Comparing the model predictions for Scenario 1 and Scenario 3 at DM1 which is the station closest to Mai Po and has the highest pollution level, the highest differences in BOD (0.294 mg/L), DO (0.173 mg/L), SS (2.74 mg/L), E. coli (1,870 count/100mL), UIA (0.0041 mg/L), TIN (0.157 mg/L) and salinity (0.046 ppt) were well within the natural fluctuations.

10.5.34 During the operation of the SWC bridge, there would be no discharge of effluent into Deep Bay from the bridge. The large amount of pollution loads entering Deep Bay as a result of increases in population and urbanisation in Shenzhen and Hong Kong is the most critical factor affecting the water quality in Deep Bay. Some parameters of the current water quality have exceeded the WQO standard. Based on the model predictions in Section 7, the SWC bridge and the reclamation at Dongjiaotou would only cause small changes in water quality conditions (<2.4%) in Deep Bay. For the SWC bridge alone, the changes were insignificant (<0.9%). Overall, the water quality changes would be within the ranges of natural fluctuations in the bay. It is therefore anticipated that the changes are not likely to cause adverse impacts to the marine ecosystem in Deep Bay. The impact is ranked as insignificant.

10.5.35 Marine water quality - Flushing rate: Water quality impacts of the SWC on nature conservation areas in Inner Deep Bay were identified as a concern. To address this concern, hydrodynamic and water quality modelling were undertaken. Results indicate that the alignment, once built, would have little impact on instantaneous tidal flows (<0.5% change) and salinity patterns in Deep Bay, and no discernible impact on longer term residual flows and salinity fluxes. Similarly, Crosslinks2 modelling predicted few or no far-field effects on water quality (Mouchel 1998). It was predicted that water movements and water quality in Deep Bay with the SWC in place would be similar to the baseline situation. Operational-phase effects of the bridge upon water quality were predicted to be insignificant at the large scale, particularly in terms of identified areas of conservation importance. It should be noted that due to the grid size used in the model, potential near-field effects such as scour near bridge piers could not be assessed. Very localised scour could occur in the immediate vicinity of the bridge piers, but water speeds would generally remain too low to erode existing sediment deposits. Any changes in bed level would take place at a very low rate and should not affect the survival of benthic fauna.

10.5.36 Deep Bay water quality (operation phase): Obstruction of water movements could alter the tidal exchange rate of Deep Bay and could produce knock-on effects in sedimentation rates and water quality. Bridge piers by themselves would reduce tidal exchange by less than 1 percent, suggesting that potential operational impacts due to obstructed tidal exchange would be undetectable or mitigable. The permanent clearance of oyster beds within the 50m marine works area could offset part of the reduction in flushing rate. Water quality modelling results support this contention by showing minor water quality changes in the operation stage of the project. The changes, however, would be minor. There would be a 0.01 mg/L decline in DO concentration and a 0.14 mg/L SS increase during the operation phase. Reclamation at the Shekou-side landfall has been included in the hydrodynamic and water quality modeling for Deep Bay.

10.5.37 Marine water quality - Sedimentation: The presence of the SWC bridge piers to some extent may change the tidal flow patterns in the bay especially in the locations near the bridge alignment and the region landward from the bridge alignment (Inner deep Bay). Siltation and resuspension rates of sediment particles in Deep Bay may be altered as a result of the changes in hydrodynamic conditions leading to the changes in sedimentation and erosion patterns. The major concern of this impact is the sediment deposition on Mai Po mudflat.

10.5.38 It, however, should be noted that the baseline sediment deposition rate in the region near Shenzhen River outlet is rather high. Most of the sediment particles discharged from the river would be carried by the tidal flows and would deposit in Mai Po and Ramsar Site increasing the sediment thickness in this region during the dry season. Mai Po located near the Shenzhen River outlet is currently being affected by this natural sediment deposition phenomenon (the average sedimentation rate up to about 28 mm/yr in Ramsar Site/Mai Po region, see Table 7.38 in Section 7).

10.5.39 The increased sedimentation rates due to the SWC bridge alone (Scenario3 vs Scenario 2) were very low. At all the indicator points, the bridge contributed to the increases in sedimentation rates of = 0.6 mm/yr. At Mai Po and Ramsar Site, the increased sedimentation rates due to effect from the bridge alone were very low, only about 0.1 mm/yr (see Table 7.38 in Section 7).

10.5.40 If both the bridge and the mainland landing point reclamation were considered (Scenario 3 vs Scenario 1), there would be some changes in velocity patterns and the exchange of flow in the inner region of the bay, mainly due to the reclamation. At Mai Po and Ramsar Site, sediment deposition rate may slightly increase (+0.3 to 0.5 mm/yr) (see Table 7.38 in Section 7) after the completion of the SWC. The cumulative impacts due to the present project and the Mainland landing point reclamation are low when compared to the natural conditions.

10.5.41 The existing sedimentation rates in Deep Bay were much higher than the small increases due to the SWC project. The natural processes would be the dominant factors in controlling the sedimentation and erosion in Deep Bay. The increase of sedimentation rate would be undetectable for the bridge alone (1 mm in 10 years), or for both the bridge and the landing point reclamation (3-5 mm in 10 years). The impact is thus ranked as insignificant.

10.5.42 Marine water quality - Road Runoff: Operation of the SWC would generate hard surface runoff containing oil, metals and other contaminants. This could affect water quality in Deep Bay and in any local watercourses affected by road drainage, with implications for freshwater and estuarine flora and fauna. The primary concern is Deep Bay marine ecology and fisheries: persistent pollutants such as metals entering the bay could enter the food web and indirectly affect fauna of conservation concern such as waterbirds and dolphins. Impacts would be dispersed along the length of the bridge and would be long-term. Given the background levels of contamination in Deep Bay and the fact that vehicles using the crossing would remain within the Deep Bay catchment whether using the SWC bridge or one of the other 3 crossings. Increased traffic flows due to potential future economic growth would increase the volume of traffic crossing the bridge. However, this would also affect the 3 existing crossings as well, all of which are in the Deep Bay catchment. Impacts are ranked as minor to moderate and requiring mitigation.
Cumulative Impacts

10.5.43 Cumulative impacts to Deep Bay capture fisheries and oyster culture would be mainly resulted from the water quality and sedimentation impacts of projects in the Deep Bay marine areas, including the present project, the Mainland section of the SWC, and the landing point reclamation of the SWC. Cumulative impacts of the SWC project could be divided into short-term or temporary impacts, and long-term or permanent impacts.

Cumulative Construction Impacts with Other Projects

10.5.44 Short-term impacts would be resulted from construction works: e.g. construction site runoff. The potential of temporary cumulative impacts will be depended upon the construction programmes of related projects in the Deep Bay catchment.

10.5.45 SWC Mainland section: The SWC Mainland section (Figure 10.8) would be constructed concurrently with the present project. It is anticipated that the construction impacts from the SWC Mainland section would be at a smaller magnitude, due to the shorter length. Impacts from this would be mainly the temporary sedimentation and pollution of Deep Bay water due to construction of piers.

10.5.46 The Mainland EIA (Shenzhen Bay Bridge) indicated that the bridge foundation would be construction using bored piles. Bored pile casing would be driven into the seabed and would confine the sediment within the casing. Release of sediment and pollutants during sediment dredging was expected to be not significant. The wastewater generated from the bored pile construction would be treated for sediment removal. The treated effluent would be reused in the piling process. Based on the construction method presented in the Mainland EIA, it is considered that the construction of bridge foundation would not cause significant cumulative water quality impacts and marine ecological impacts with the SWC project.

10.5.47 SWC landing point: Reclamation on the Hong Kong side would not be required for the SWC project. The only required reclamation is the 1.5 km2 landing point at Dongjiaotou on the Shenzhen side (Figure 10.8). A review of the Mainland EIA Report on the SWC Reclamation and Foundation Treatment Engineering (Reference 2) was conducted. The report presented that the potential water quality impacts would be mainly associated with the reclamation activities. The Mainland authorities confirmed that the reclamation at Dongjiaotou would be conducted behind seawalls and would commence in 2002. The overall construction period was expected to be approximately 22 months. External seawall would be constructed along the perimeter at the early stage of the reclamation and be completed within the first 6 months of the overall construction programme. The seawall strengthening and construction to enclose reclamation works at Dongjiaotou for the Shenzhen reclamation would be completed prior to commencement of construction of the SWC bridge in August 2003. All the reclamation activities would be carried out behind the seawall and there would be no overflow of water from the enclosed reclamation site to Deep Bay when carrying out the filling activities. Filling behind the seawall would continue for the remaining 16 months thereafter, but sediments would be confined to the area within the seawall. The whole reclamation site would be divided into a number of cells. Discharges of seawater would be from an active cell to the adjacent inactive cells. The inactive cells provide a quiescent environment for settling of sediment particles. The seawater at the last cell would be pumped out from the confined reclamation site to the sea. After settling of sediment particles, the seawater pumped out from the site is not likely to contain high concentrations of suspended solids. Thus there would be no potential for sedimentation of Deep Bay waters during the filling process.

10.5.48 As the proposed SWC project would commence in August 2003, there would be no overlap of the bridge construction project with the seawall construction project. The completion of external seawall at the landing point before the SWC project would minimise the accumulation of water quality impacts from the filling process of Shenzhen reclamation and the SWC project. Therefore, no significant cumulative impacts would be resulted from these two projects.

10.5.49 It was also confirmed with the Mainland authorities that there would be no sand dredging from Deep Bay for reclamation. The source of the fill materials for reclamation would be mainly from land and import of marine sand fill for reclamation might be required. It is expected that the water content for these types of fill materials would be low and discharge of sediment-laden flow from the reclamation site can be avoided.

10.5.50 The potential water quality impacts from concurrent construction of SWC bridge piers of the Hong Kong and Mainland sections and reclamation at Dongjiaotou have been presented in Section 7.7.63 to Section 7.7.68. There were no exceedances of WQO and Mainland Category 1 standard for SS at all the identified water sensitive receivers. Mitigation measures of the Hong Kong section of the SWC, mitigation measures in the Mainland EIA, and the Environmental Management and Audit Plan in the Mainland EIA, to minimise the water quality impacts arising from the Hong Kong section, Mainland section and landing reclamation have also been detailed in Section 7 of this report. It is anticipated that the potential water quality impacts would not be significant provided that the above-mentioned conditions could be met. There would not be cumulative impacts from the three items of works.

10.5.51 Deep Bay Link: The construction programme for the Deep Bay Link project will be implemented concurrently with the SWC project. All the construction works for the Deep Bay Link project would be carried out from a land-based operation and impacts would mainly come from site runoff due to construction. Release of construction site runoff into Deep Bay from terrestrial works areas of DBL could also contribute to water quality degradation and might cause cumulative impacts with the SWC project. Pollutants that might be discharged include fuels, solvents, lubricants, and sewage. Construction site runoff can be effectively controlled through the implementation of suitable mitigation measures, e.g. provision of site drainage systems and sedimentation facilities, routine monitoring of the effluent discharge quality and environmental audit. The other issues including generation of wastewater and sewage, and accidental spillage of toxic substances during the construction period can also be minimised or controlled by providing chemical toilets and/or wastewater treatment facilities, off-site disposal of wastewater/sewage and establishment of a spill response plan. The potential to have cumulative water quality impacts due to the Deep Bay Link project would be low.

10.5.52 Construction of the proposed DBL would also require resuming 0.73 ha of fishponds, representing less than 0.1% of the total fishponds in Hong Kong. Of these only one will be lost permanently. This impact was identified as insignificant and would not cause cumulative impact as no fishpond loss would be resulted from the SWC project.

10.5.53 Water Supply to Hung Shui Kiu, Kwu Tung North, Fanling North and Ping Che/Ta Kwu Ling New Development Areas: This WSD project is tentatively scheduled to commence in around late 2005 or early 2006, and to complete by 2009. The construction programme for this WSD project would overlap with the SWC construction programme.

10.5.54 The proposed pipe section for the project includes a 900mm diameter salt water main, which would be laid along the Deep Bay Road passing through Fung Kong Tsuen Road to Hung Shui Kiu NDA. Part of the section would fall within the SWC site boundary.

10.5.55 Excavation of trenches would be required during the construction of the salt water main. The potential water quality impacts that may arise from this WSD project would mainly be construction site runoff. A rainstorm may wash away the excavated materials to Deep Bay. The impact could be minimised if suitable mitigation measures are implemented when carrying out the excavation activities. Guidelines for the handling and disposal of construction discharges provided in ProPECC Note PN1/94 on Construction Site Drainage should be adopted to avoid water quality pollution. Digging of trenches should be carried out in short sections. After finishing a section of works, trenches and holes should be immediately back-filled to minimise the inflow of rainwater during rainstorms.

10.5.56 A salt water service reservoir is also proposed under this WSD project. The tentative location would be near the Fung Kong Tsuen Road at hillside of Fung Kong Tsuen. This proposed salt water service reservoir is located outside of the works limits of SWC.

10.5.57 The scale of this WSD project is expected to be small. It is anticipated that there would be no additional impact induced by this WSD project after the implementation of suitable mitigation measures.

10.5.58 Water supply to Sludge Treatment Facility at Tuen Mun: A fresh water main is proposed to provide water supply to the proposed sludge treatment facility near WENT landfill site. This fresh water main would pass through Nim Wan Road, Lau Fau Shan Road, Tin Wah Road and Tin Ying Road and would connect to an existing fresh water main in Tin Shui Wai. The tentative commencement date of this project would be in 2005 and the completion date would be in 2008.

10.5.59 The key issue that may cause cumulative impacts with the SWC project is construction site runoff. Digging of trenches would generate exposed soils, which may be a potential pollution source to the Deep Bay waters. The ProPECC Note PN1/94 on Construction Site Drainage should be adopted to minimise the potential impact. In addition, good management practices could ensure that the potential impact to the nearby water body is minimal. It is likely that the overlapping of this WSD project with the SWC project would not cause unacceptable cumulative impacts in Deep Bay.

10.5.60 Yuen Long and Kam Tin Sewerage and Sewage Disposal - PWP Item No. 4215DS: The boundary of this project covered an extensive area from Pat Heung to Kam Tin River. The tentative programme for commencement of the project is scheduled in May 2005 and for completion in August 2007. This DSD project involves the provision of rising mains and gravity sewers at Tin Ying Road, Tin Wah Road and Lau Fau Shan Road. Similar to the projects proposed by WSD, construction site runoff would be the key issue that may cause cumulative impacts with the SWC project. Implementation of the guidelines recommended in the ProPECC Note PN1/94 on Construction Site Drainage could control the release of construction site runoff and minimise the other potential water pollution issues associated with the construction works.

10.5.61 Upgrading & Expansion of San Wai Sewage Treatment Works (STW) and the Expansion of Ha Tsuen Pumping Station: The construction works for this project would commence in around 2004. The project is planned to expand the existing facilities at San Wan STW and Ha Tsuen Pumping Station. The treated effluent would be discharged via the NWNT effluent tunnel. An emergency discharge culvert from San Wai STW to nearby drainage channel would be constructed to provide an alternative discharge route for the treatment works.

10.5.62 An EIA study is being conducted for this project. All the construction and operational phase impacts would be addressed in that EIA. The construction works would be carried out from a land-based operation. The locations of the construction sites for this project are away from Deep Bay. Runoff from the construction sites may enter the local stream courses and/or Tin Shui Wai Drainage Channel before entering Deep Bay. With all the mitigation measures in place to control water quality pollution from the construction sites, the potential cumulative impacts with the SWC project would be low.

10.5.63 Hung Shui Kiu New Development Areas (HSK NDA): The construction works for this development project would be in 2004 and the expected completion date is in 2008. The site limit of SWC is far away from the HSK NDA and there would be no conflict between the two projects. Environmental monitoring and audit would be implemented for the HSK NDA project. It is not expected that there would be adverse cumulative impacts generated from these two projects.

10.5.64 Construction site runoff from all other concurrent terrestrial projects including Deep Bay Link can be controlled through standard site management practices that prohibit runoff entering water bodies. No cumulative impacts would be expected from those land-based projects.

Cumulative Operation Impacts with Other Projects

10.5.65 The long-term impacts would result from changes in hydrodynamic conditions and pollution loading. Their potential will depend upon the nature of those projects.

10.5.66 SWC Mainland section and landing point: Scenario 3 in the water quality modelling had taken into account the Mainland section and the landing point of SWC. The cumulative operation impacts on water quality had been addressed in the sections of operation phase impacts above. No significant effect from cumulative impacts on water quality has been identified.

10.5.67 Deep Bay Link: The Deep Bay Link project impacts would include permanent potential for increased long-term pollution of lowland streams and Deep Bay waters due to road runoff. The drainage system in Deep Bay Link could effectively address the road runoff issue and no cumulative impacts would be expected.

10.5.68 "Yuen Long and Kam Tin Sewerage and Sewage Disposal" and "Upgrading & Expansion of San Wai Sewage Treatment Works (STW) and the Expansion of Ha Tsuen Pumping Station" would have positive effects on the water quality in Deep Bay. Sewage would be more effectively collected and treated in the STW in Yuen Long and San Wai, and then dispose the effluent in Urmston Road. These two projects could reduce non-point pollution input within the Deep Bay catchment.

10.5.69 The majority of the area for Hung Shui Kiu New Development Areas (HSK NDA) is currently wasteland or abandoned agricultural lands. Given the highly disturbed nature of the area, it is a potential source of sediment in the flow in Tin Shui Wai Drainage Channel and also Deep Bay during wet season. After the completion of this project, the surface runoff from the area would be expected to increase in quantity, but decrease in the sediment carried. There would be no cumulative impacts resulted from this project.

Summary

10.5.70 For cumulative impacts, Section 4.3.3 in EIAO-TM has listed out three circumstances for cumulative impacts:

· the impacts arising from the project are predicted to extend beyond the boundaries of the project or over a long period of time;
· there may be interactions between the environmental impacts of the project, affecting the sum total of its environmental impacts; or
· there may be interactions between the environmental impacts of the project and the environmental impacts of other developments, resulting in accumulation of impacts and affecting the sum total of their environmental impacts.

10.5.71 In the SWC project, the majority of fisheries impacts, including temporary and permanent fishing ground loss or loss of mudflats available for oyster farming, would be localised in nature and would not extend beyond the project boundary. The only impacts might have influences beyond the project boundary would be those related to marine water quality such as flushing rate and sedimentation rate. Since the assessment area of water quality covered the entire Deep Bay WCZ, the influences from marine water quality changes on areas outside the project boundary have been addressed in Water Quality Assessment.

10.5.72 No interaction between the environmental impacts of the present project, which might affect the sum total of the impacts, was found.

10.5.73 For the interactions with impacts from other developments, the majority of other projects in Deep Bay area would be land-based, including Deep Bay Link. Moreover, the construction of the majority of other projects would not overlap, or would only overlap in a short period of time with the SWC construction. Only Deep Bay Link, the Mainland section, and the landing point reclamation of the SWC would be constructed concurrently with the present project.

10.5.74 Other than site runoff, Deep Bay Link and other land-based projects would have little potential to produce cumulative impacts with the present project in terms of marine water quality. Mitigation measures to control site runoff would be provided in those land-based projects and thus no cumulative impacts on water quality would be expected.

10.5.75 For the Mainland section of the SWC, bored pile method would be used for the bridge pile construction, while the seawall construction of the landing point reclamation would be finished prior to the filling and the commencement of the present project. No cumulative impacts on water quality during construction would be expected.

10.5.76 During operation phase. The potential for cumulative impacts resulted from land-based projects would be very limited. There would be no accumulation of impacts and no influence on the sum total of habitat loss.

10.5.77 Scenario 3 in the water quality modelling had taken into account the Mainland section and the landing point of SWC. The cumulative operation impacts on water quality had been addressed in the sections of operation phase water quality impacts. So there would be no additional cumulative operation impacts with the SWC.

10.5.78 To conclude, cumulative impacts predicted to arise from the proposed project in conjunction with other concurrent projects in Deep Bay area are not expected to result in greater adverse impacts to fisheries resources than impacts arising from the concurrent projects independently.

10.6 Prediction and Evaluation of Environmental Impacts

10.6.1 Only 5.4 ha of existing oyster beds and about 23 floating oyster rafts are subject to direct impacts from the proposed project. The fisheries impact associated with the proposed project is considered minor. An evaluation of the impact in accordance with the EIAO TM Annex 9 is presented in Table 10.4.

Table 10.4 Evaluation of Fisheries Impacts in Accordance with EIAO-TM Annex 9.

10.7 Mitigation of Adverse Environmental Impacts

10.7.1 In accordance with the guidelines in the EIAO-TM on fisheries impact assessment the approaches to mitigating impacts to fisheries, in order of priority, are avoidance, minimizing, and compensation.

Design Phase Considerations

10.7.2 Several design features of the bridge could effectively minimise impacts. Details are discussed below.

10.7.3 Increase pier spacing: Mouchel (1999) evaluated a bridge built on piers at 50 m intervals, and requiring some 106 piers. In the initial design phase of this project the SWC project team recommended increasing the spacing of piers to 75 m to reduce the number of piers, and thereby create more open space beneath the bridge, which was found acceptable by Hong Kong and Mainland on engineering grounds. This reduced pier numbers from 106 pairs to 70 pairs, thereby avoiding impacts of 36 pairs of piers.

10.7.4 This reduced pier numbers from 106 pairs to 70 pairs, thereby avoiding impacts of 36 pairs of piers on subtidal and intertidal habitat. Both the area of permanent loss and temporary loss are reduced by 50%.

10.7.5 Submerged pile caps: The pile caps for typical piers measure 8.5 x 8.5 m. Pile caps can be located either within the seabed mud or at the seabed surface. To avoid subtidal and intertidal seabed losses of 144.5 m2 at each pair of piers the project team recommended constructing pile caps beneath the seabed surface. The resulting net loss at typical piers would be <15 m2 (cross-sectional area of pier column), resulting in conservation of >130 m2 of seabed at each of 70 pairs of piers (>0.9 ha total).

10.7.6 Temporary and permanent impacts of the SWC bridge to capture fisheries resources in Deep Bay and surrounding waters would be minor in the present project. No mitigation measure would be required.

10.7.7 Temporary and permanent impacts of the SWC bridge to the existing oyster rafts in Deep Bay and surrounding waters would be minor in the present project. Relocation of about 23 oyster rafts would be needed. The results from the aerial photos and side-scan sonar surveys demonstrated that the locations of the oyster rafts were not fixed and relocation is thus possible. One of the feasible relocation areas would be the sea area at the southwest end of this group of oyster rafts, i.e. the area seaward of Sheung Pak Nai. The density of oyster rafts in this area was relatively low throughout the course of the current study. This area is also outside the 500m assessment area boundary for SWC, and is located more seaward in Deep Bay. Water quality in this area is normally better than that within the current locations of the 23 affected oyster rafts. Consultation with the oyster farmers on the details of relocation procedures should be conducted before the commencement of the project.

10.7.8 Temporary and permanent impacts of the SWC bridge to the area of mudflat available for oyster farming near Lau Fau Shan and in Deep Bay would be minor. No mitigation measure would be required.
10.7.9 There would be no temporary or permanent impacts of the SWC bridge to fish culture in fishponds. Therefore no mitigation measures are required.

10.7.10 Sediment and pollutant resuspension would be avoided through construction methods including use of sheet-piling to surround pier works areas and use of bored pilings within casings for bridge piers. Details are provided in Section 7 of this report. These measures are considered adequate to avoid sedimentation and pollution during pier construction. Closed-grab dredges should be employed where dredging is required. For works on land-based sites, standard site runoff control measures should be established and strictly enforced to ensure that contaminated or silt-laden runoff does not enter Deep Bay. Earth-moving should be scheduled as far as possible outside the rainy season.

10.7.11 Temporary impacts caused by water quality degradation including site runoff during construction phase would be mitigated by the measures proposed for water quality impact avoidance and mitigation, including the use of cofferdams and enclosed rotary piling during pier construction, and terrestrial site management measures designed to prevent runoff to water bodies. According to the Water Quality Assessment for the present project, the bridge piers would be constructed on bored piles and dredging would be confined within the bored pile casing. Cofferdams would also be built to surround the pile cap construction sites. Release of sediment may only occur during the transfer of dredged sediments to barges. The potential release of sediment, however, could be further controlled through the use of closed grab dredgers and installation of silt curtains surrounding the works areas. As a result, there would be no significant disturbance to the seabed sediments, and the construction impacts in terms of sediment loss would be localised and are therefore not expected to be significant. Implementation of such measures would reduce impacts to acceptable levels on both water quality and fisheries.

10.7.12 Operation phase water quality, as shown in the water quality assessment would be acceptable, thus there would be no impact upon fisheries. No mitigation measure would be required.

10.7.13 This is a water quality mitigation measure intended to minimise degradation of Deep Bay waters from road surface runoff. Details are provided in Section 7 of this report. The road surface and drains are to be cleaned twice a week. Adherence to this schedule should be monitored through periodic on-site inspection and review of logs maintained by cleaning crews. Bridge surface runoff throughout Hong Kong and most of the rest of the world is not managed other than by provision of silt and/or grease traps in the bridge deck. For the SWC bridge potential for pollution of Deep Bay waters will be avoided in part by provision of silt-grease traps. A second level of surface runoff management would be the cleaning of the bridge deck and all silt-grease traps twice a week. The twice-a-week interval was selected because contaminants on road surfaces reach peak concentrations after 10-day periods, after which they are dispersed by wind or gusts caused by passing vehicles. Cleaning at twice-a-week intervals would remove contaminants before they accumulate to levels at which they would be dispersed by wind.

10.7.14 Collected materials would be disposed at a designated landfill site, probably WENT Landfill. In light of global experience with bridges over waterbird and marine resource conservation areas this level of runoff treatment was considered adequate to avoid unacceptable levels of contamination of Deep Bay waters.

10.7.15 There is also contingency plan, as detailed in Section 7 of this report, to prevent and minimise the damages from accidental chemical spillage from the traffic on the bridge. Data inidcated that the chance of chemical spillage is remote and the plans would be sufficient to address this potential impact.

10.7.16 Cumulative impacts predicted to arise from the proposed project in conjunction with concurrent projects are not expected to result in greater adverse impacts to fisheries sensitive receivers than would impacts arising from the concurrent projects independently.

10.8 Residual Environmental Impacts

10.8.1 Residual direct impacts on fisheries, especially on oyster farming, from the SWC would be insignificant. Large areas of mudflats and open sea remain available for oyster farming in Deep Bay. Oyster beds can be removed and oyster rafts can be relocated prior to the commencement of SWC construction.

10.8.2 Based upon the water quality assessment results, the residual indirect impacts from water quality changes would be insignificant relative to fisheries after the water quality mitigation measures are implemented.

10.9 Environmental Monitoring and Audit

10.9.1 Impacts during construction and operation of the project may be monitored through an environmental monitoring and audit (EM&A) programme to be specified in an EM&A Manual.

10.9.2 As permanent impacts to the fishery are initially predicted to be minor, the development of a monitoring and audit programme to assess the effects of the SWC project on commercial fisheries is not considered necessary.

10.9.3 Construction and operation of the project would include constraints which act as appropriate mitigation measures to control environmental impacts to within acceptable levels. Monitoring and audit activities designed to detect and mitigate any unacceptable impacts to water quality will also serve to protect against temporary unacceptable impacts to fisheries resources.

10.10 Conclusions

10.10.1 This chapter provides an outline of the fisheries baseline for the area, an assessment of likely fisheries impacts from project construction and operation, and preliminary options for impact mitigation.

10.10.2 A review of existing information, supplemented by the results of recently undertaken field surveys, on commercial fisheries resources located within and around the study area has confirmed that Deep Bay supports fisheries resources that are neither abundant nor of high value in comparison to resources in other fishing areas of Hong Kong.

10.10.3 Potential impacts to fisheries resources and operations may arise from permanent or temporary loss of capture fisheries area or oyster culture area, and/or changes in water quality.

10.10.4 The 40 pairs of bridge piers in HKSAR waters will permanently occupy about 0.22 hectares of seabed, 0.196 ha of which would be in subtidal zone, and 0.024 ha of which would be in the mudflat zone. The 0.22ha of seabed loss would constitute a loss of about 0.01 % of the total fishing ground in Fishing Area 48 (Lau Fau Shan, 2,107.43 ha in area). This impact is ranked as minor.

10.10.5 Since the area of mudflat cleared for the construction works (139m in width) would not be available for oyster farming again, the 16 ha inside works area would constitute a permanent loss of potential oyster farming sites. An estimate showed that the area of mudflat along the south shore of Deep Bay from Tsim Bei Tsui to Ha Pak Nai is 747 ha. This figure represents the total area of HKSAR mudflat available for oyster bed farming. The permanent loss of 16 ha would constitute a 2.1 percent reduction in the potential area for oyster beds within Deep Bay. Due to the small area permanently affected by the bridge, and the progressive decline of the oyster culture industry in HKSAR, the potential project impacts upon oyster culture are considered minor.

10.10.6 The potential percentage losses in capture fisheries would be small compared to the overall resources in HKSAR. Therefore any loss of fisheries resources, e.g. 16 ha of mudflats and 0.196 ha of sea areas, were considered to be of minor significance to the fishing industry.

10.10.7 Sediment deposition could be caused by dredging for bridge piers or by site runoff. If site management practices are strictly enforced, runoff and contamination would be minimal and is not anticipated to impact fisheries resources.

10.10.8 Changes in water quality would be minimal, therefore adverse impacts to fisheries resources are not predicted.

10.10.9 After mitigation measures for water quality are implemented, including cofferdams, closed grab dredgers, silt curtains and standard site practices, no significant adverse impacts are predicted on any fishing grounds, species or practices of importance to the local or HKSAR fishery. About 23 oyster rafts will be relocated to suitable locations before the commencement of the construction works. Oyster raft operators are required to be consulted on the relocation operation before commencement of any works.

10.10.10 While no special mitigation measures are required for fisheries, standard site practices to control impacts to water quality to within acceptable levels are expected to mitigate impacts to fisheries resources.

10.10.11 Cumulative impacts predicted to arise from the proposed project in conjunction with concurrent projects are not expected to result in greater adverse impacts to fisheries resources than impacts arising from the concurrent projects independently.

10.11 References

Agriculture & Fisheries Department (AFD). 1992-2000. Departmental Annual Report. Agriculture & Fisheries Department, Hong Kong Government.

Agriculture & Fisheries Department (AFD). 1995. Categorization of Agricultural Land. (Revised 1995.) Agriculture & Fisheries Department, Hong Kong Government.

Agriculture & Fisheries Department (AFD). 1998. Port Survey 96/97. Summary Table. Prepared by Capture Fisheries Division.

Anon. 1988a. Deep Bay Integrated Environmental Management. Key Issues. Hong Kong: Environmental Resources Ltd.

Anon. 1988b. Environment Review: Deep Bay Management. Executive Summary. Hong Kong: Environmental Resources Ltd.

Binnie & Partners (Hong Kong) and Shankland Cox (Binnie). 1984. Tin Shui Wai Development. Environmental Impact Assessment of Land Preparation Aspects. Draft Evaluation Report October 1984.

China Green Environment and Development Center (CGEDC). 1996b. Shenzhen-Hong Kong Western Corridor (Shenzhen Bay Bridge): Studies on Shenzhen Bay Water Quality and Ecological Impact. Prepared by National Environmental Protection Agency, China Green Environment and Development Center. Dated Dec. 1996. (In Chinese.)

City University of Hong Kong. 2001. Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment. Prepared by Center for Coastal Pollution and Conservation. Dated July. 2001.

Electronic and Geophysical Services Ltd. 1987a. Nim Wan Controlled Land Fill. Phase I Gazettae Area. Survey of Oyster Beds. Volume I: Phase I Gazettae Area. Side Scan Sonar Survey. Mapping of Farm Boundaries. Correlation diving survey. Final Report. Job number HK26686. June1987.

Electronic and Geophysical Services Ltd. 1987b. Tin Shui Wai Development. Second (1987) survey of oyster beds in Deep Bay. Final Report. Job number HK29987. August 1987.

Environmental Protection Department (EPD). 2001a. River Water Quality in Hong Kong for 2000. Results for 2000 from the River Water Quality Monitoring Programme of the Environmental Protection Department. Printing Department, Hong Kong.

Environmental Protection Department (EPD). 2001b. Marine Water Quality in Hong Kong for 2000. Results for 2000 from the Marine Monitoring Programme of the Environmental Protection Department. Printing Department, Hong Kong.

ERL (Asia) Ltd 1989. Deep Bay Guidelines

Hong Kong - Guangdong Environmental Protection Liaison Group (HKGEPLG). 1992. Technical Report on the Environmental Protection of Deep Bay and its Catchments. Report of the HKGEPLG Technical Sub-Group. Dated Dec. 1992.

Irving, R. and B. Morton. 1988. A Geography of the Mai Po Marshes. Hong Kong University Press, Hong Kong.

Leung, C., Shortridge, K.F., Morton, B. and Wong, P.S. 1975. The incidence of faecal bacteria in the tissues of the tissues of the commercial oyster Crassostrea gigas Thunberg correlated with the hydrology of Deep Bay, Hong Kong. pp. 114-27: in: B. Morton (ed.): Proceedings of the Pacific Science Association Special Symposium on Marine Sciences, Hong Kong 1973. Government Printer, Hong Kong.

MHA. 1987. West New Territories (WENT) Landfill EIA. Report prepared by Mott, Hay and Anderson Hong Kong Ltd. for Environmental Protection Department, HKSAR.

Mouchel Asia Ltd. 1997. Feasibility Study for Additional Cross-Border Links Stage 2: Investigations on Environment, Ecology, Land Use Planning, Land Acquisition, Economic/Financial Viability and Preliminary Project Feasibility/Preliminary Design. Water Quality Impact Assessment Review Paper. Prepared for Planning Department, HK SAR Govt. Report dated Dec. 1997.

Mouchel Asia Ltd. 1998. Water Quality Impact Assessment. Working Paper 2. (Deep Bay Crossing and Lingdingyang Bridge) Feasibility Study for the Additional Cross Border Links: Stage 2 Investigations on Environment, Ecology, Land Use Planning, Land Acquisition, Economic/Financial Viability and Preliminary Project Feasibility/Preliminary Design. Prepared for Planning Department, HKSAR Govt. Dated Dec. 1998.

Mouchel. 1999. Final Ecololigcal Impact Assessment, Working Paper WP3. Feasibility Study for Additional Cross-Border Links Stage 2: Investigations on Environment, Ecology, Land Use Planning, Land Acquisition, Economic/Financial Viability and Preliminary Project Feasibility/Preliminary Design. W. Prepared for Planning Department, HK SAR Govt. Report dated Dec. 1999.

South China Sea Fisheries Regulation Agency (SCSFRA). 1985. Map of Fisheries Resource Protection Zones in the South China Sea. Dated August 1985.

Young, L. and D. S. Melville. 1990. Conservation of the Deep Bay Environment. pp. 211-231 in: B. Morton, ed.: The Marine Biology of the South China Sea. Proceedings of the First International Conference on the Marine Biology of Hong Kong and the South China Sea, Hong Kong, 28 Oct.-3 Nov. 1990. Volume 1. Hong Kong University Press, Hong Kong.

Young, L. and D. S. Melville. 1995. Environmental Research at the WWF Hong Kong Mai Po Marshes Nature Reserve. pp 58-68 in: Environmental Research in Pearl River and Coastal Areas. Guangdong Higher Education Press, Guangzhou.