15. ENVIRONMENTAL OUTCOMES

15.1 Air Quality Impact

15.1.1 Major air quality impact during the operational phase of the project would arise from the tailpipe emissions of the vehicles travelling on the proposed SWC. There might also be cumulative air quality impacts at some sensitive receivers due to traffic emissions from the proposed Deep Bay Link as well as other planned and existing roads in the area.

15.1.2 Computer dispersion modelling was undertaken to assess the potential operational phase cumulative air quality impacts due to traffic emissions from the proposed SWC and the future road network in the area. The modelling results showed no exceedance of the respective Air Quality Objectives (AQO) for nitrogen dioxide, respirable suspended particulates, carbon monoxide, and sulphur dioxide at all the identified existing and future air sensitive receivers in the vicinity of the proposed SWC. The highest 1-hour average and 24-hour average nitrogen dioxide level are 82% and 95% of the corresponding AQO predicted at an existing village house in Ngau Hom Shek. The predicted highest 24-hour average respirable suspended particulates level are 54% of the corresponding AQO. Whereas the highest predicted 1-hour average carbon monoxide level, and the 1-hour average and 24-hour average sulphur dioxide levels at the air sensitive receivers are all below 28% of the corresponding AQO.

15.2 Noise Impact

15.2.1 During the construction phase of the Project, the predicted noise levels at some of the existing noise sensitive receivers (NSRs) in the close proximity of the construction sites would be exceeded. Implementation of different forms of mitigation measures including the use of quiet plant and working methods, the use of movable and temporary noise barriers, provision of noise screening structures and purpose-built noise barriers, and percentage on-time usage of equipment would reduce the noise impacts. The construction phase assessment results showed that all NSRs could be adequately protected by the proposed mitigation schemes and there would be no residual noise impacts after applying the proposed mitigation schemes.

15.2.2 The operational noise impacts would be from the traffic. Low noise surfacing would be adopted as a standard provision under current policy for high speed road and would reduce road traffic noise impacts. Barriers which would introduce extra visual impact are avoided. The operational phase assessment results showed that all predicted noise levels at NSRs were found to be within acceptable standards. There would be no residual impacts for the operational phase of the SWC project.

15.3 Hydrodynamics, Water Quality And Sediment Quality Impacts

15.3.1 Environmentally friendly design to minimise the hydrodynamic and water quality impacts due to the proposed Project include:

· adopting a longer span of a 75m spacing;
· adopting submerged pile cap in the design;
· reducing the numbers of piles in the water column; and
· desiging the bridge pier in a suitable form (streamline shape) to reduce friction.

15.3.2 The identified water quality impacts during the construction phase of the Project include construction site runoff and wastewater generated from construction activities, sewage from workforce, accidental spillage of chemicals on site, sediment dredging and disposal, and changes in hydrodynamic conditions during bridge pier construction. All these identified impacts could be mitigated to acceptable levels through the implementation of mitigation measures. No residual impacts were anticipated.

15.3.3 Category L, M and H materials were found in the Site Investigation. The sediment volumes for open sea disposal and confined marine disposal were estimated to be approximately 34,500m3 and 22,500m3 respectively.

15.3.4 The proposed enhancement measure would involve sediment dredging in the inlet channel and access route at Mai Po. Category M and H materials were found in the Site Investigation and the estimated volume of sediment to be disposed of at confined marine disposal sites was about 8,800 m3.

15.3.5 During the operational phase, the identified water quality impacts include the changes in hydrodynamic and water quality conditions and changes in sedimentation and erosion patterns in Deep Bay, road runoff from SWC bridge and accidental spillage of chemicals/oils during accidents. The model predictions showed that the changes in hydrodynamic (-3.7%), water quality (<2.5%) and sedimentation/erosion conditions (0.3-0.5mm/yr at Mai Po and Ramsar Site) in Deep Bay were small after the completion of the SWC project and the reclamation at Dongjiaotou. The changes due to the SWC bridge alone were much smaller. Frequent cleaning of road sludge would be implemented to minimise the potential impacts from the SWC bridge runoff. FSD, Police Force, HyD and EPD are responsible for responding to accidental spillage from general vehicle accidents on the SWC bridge. Control and clean up of spill would minimise the impacts to the Deep Bay environment. Residual impacts during the operational phase would be low.

15.4 Waste Management

15.4.1 The types of wastes that would be generated during the construction phase of the Project include C&D material, excavated material, marine dredged sediment, chemical waste and general refuse. The estimated waste quantities were 700 m3 of C&D material (20% would be recycled and reused), 57,000 m3 of marine dredged sediment (uncontaminated: 34,500 m3 and contaminated: 22,500 m3) and 151 tonnes of general refuse. For the enhancement measure of sediment dredging at Mia Po, the estimated volume of sediment (Category M and H material) to be disposed of at confined marine disposal sites was about 8,800 m3. The amount of excavated material and chemical waste was minimal. The C&D material and excavated material would be reused and recycled as far as practicable and the remaining wastes would be disposed of at public fills and landfills. Chemical wastes would be transferred to chemical waste treatment facility at Tsing Yi. General refuse would be reused and recycled wherever possible and the final disposal would be made at landfills. The operational phase is not expected to generate any amount of wastes.

15.5 Ecological Impact

15.5.1 The main potential ecological impacts resulting from the project were identified as:

· During construction, the cumulative temporary direct habitat loss will be 2.7 ha in subtidal zone, and 0.75 ha in intertidal zone, plus removal of about 0.25ha mangrove trees. Only less than 0.001 ha of Seagrass might be potentially influenced.
· In operation phase, the resulted permanent habitat loss will be only less than 0.2 ha in subtidal zone and 0.024 ha in intertidal zone.
· The indirect impact on the feeding habitats of birds due to disturbance were found to be insignificant as most birds including Black-faced spoonbill (BFS) are more disturbance-tolerant than previously though.
· Even in the worst case scenario, the affected BFS feeding ground is estimated to be only 0.24 ha in area. This 0.24 ha represents a small fraction (1.6%) of the 15 ha intertidal feeding habitat for BFS along the south shore of outer Deep Bay, and is much less important to the BFS than the inner Deep Bay. The temporary loss is predicted to be an undetectable impact.

15.5.2 The percentage losses in habitats would be small compared to the overall resources in HKSAR. Therefore they were considered to be of minor significance to the ecology.

15.5.3 All other construction impacts would be either insignificant , or minor in severity.

15.5.4 Measures to mitigate impacts upon ecological sensitive receivers are detailed in Chapters 7 and 9. With the successful implementation of mitigation measures, for water quality including cofferdams, closed grab dredgers, silt curtains and standard site practices, and for ecology including clearance of oyster beds, restoration of mudflats after construction, mangrove replanting, and seagrass relocation, no significant adverse residual impacts were predicted on any habitats, and species of conservation concern.

15.5.5 All long-term impacts from operation of the bridge were predicted to be insignificant or minor and could be mitigated with no unacceptable residual impact.

15.5.6 Additional enhancement measures are, however, proposed to contribute to the long-termed goodness of the Deep Bay ecosystem, including a programme to locate and removal of exotic mangrove species and weeds (such as Sonneratia spp. & Spartina sp.) and a plan to restore the function of 24.3ha of Gei Wais in Mai Po as bird feeding ground by improving their water change capacity through dredging in the inlet water channel.

15.5.7 Cumulative impacts with other concurrent projects would not result in greater adverse impacts to ecological resources than impacts arising from the concurrent projects alone, and are acceptable.

15.6 Fisheries Impact

15.6.1 The main potential fisheries impacts resulting from the project were identified as:

15.6.2 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.

· The temporary loss of fishing ground and oyster culture area in construction phase will be 27 ha and 16 ha respectively. About 23 oyster rafts will be relocated to suitable locations before the commencement of the construction works.
· The 0.22 ha of permanent 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).
· The 16 ha inside works area would not be available for oyster farming again, and would constitute a permanent loss of potential oyster farming sites. The permanent loss of 16 ha would constitute a 2.1 percent reduction in the potential area for oyster beds within Deep Bay (747 ha).
· Sediment deposition could be caused by dredging for bridge piers or by site runoff during construction phase. If site management practices were strictly enforced, runoff and contamination would be minimal and was not anticipated to impact fisheries resources.
· Changes in water quality would be minimal, therefore adverse impacts to fisheries resources were not predicted.

15.6.3 The potential percentage losses in capture fisheries would be small compared to the overall resources in HKSAR. Therefore any loss of fisheries resources were considered to be of minor significance to the fishing industry.

15.6.4 Measures to mitigate impacts upon fisheries sensitive receivers are detailed in Section 7 and 10. With the successful implementation of mitigation measures, for water quality, including cofferdams, closed grab dredgers, silt curtains and standard site practices, no significant adverse residual impacts were predicted on any fishing grounds, species or practices of importance to the local or HKSAR fishery.

15.6.5 Cumulative impacts with other concurrent projects would not result in greater adverse impacts to fisheries resources than impacts arising from the concurrent projects alone, and are acceptable.

15.7 Hazard to Life

15.7.1 The s-curve alignment was selected as the preferable alignment option based on the sensitivity test results and the advantages over the straight type alignment. The engineering study of the s-curve bridge option determined that explosives would not be required for the construction of the SWC bridge. There would be no risk due to storage or use of explosives. Quantitative assessment on the potential risk due to storage, handling and on-site treatment of explosives is not required.

15.8 Cultural Heritage Impact

15.8.1 Previous archaeological works had identified that the works area situated within the Ngau Hom Shek (NHS) Archaeological Beach Site is rich with archaeological remains dated Neolithic period and late Bronze Age. The same findings were also discovered to the west and south of this area. Previous investigation also indicated that western Yuen Long coast is an area of high archaeological potential and archaeological deposits are originally distributed along the beach and hill foot which has now been extended farther into the landside due to the change in topography.

15.8.2 The land archaeological survey to the west of NHS Archaeological Beach Site has identified the presence of deposits with relics of different periods mixed together, that include Bronze Age, Song, Ming and Qing periods. Archaeological land survey to the east of NHS Archaeological Beach Site has identified lithic remains belong to jue-ring making workshop. The stone and pottery remains are dated to the late Bronze Age, or the Late Western Zhou and the Spring-and-Autumn period. The survey of landform of the piggery that is almost entirely covered by cement revealed that this area contains deposits from Song Dynasty and also late Bronze Age.

15.8.3 The previous marine archaeological survey discovery was of later Song/early Ming Dynasty boat exposed during the construction of the High Island Reservoir. No previous record on shipwrecks are available.

15.8.4 Part of the study area is shallow in water depth (0-2m) and significantly covered with oyster beds, therefore has prevented archaeological survey. The side scan sonar data revealed that the seabed within the study area has been extensively trawled. The trawling activities may have destroy or redistribute archaeological materials and hence reducing the archaeological potential. Five unidentified targets within the southern section of the study area were discovered, no further diver inspection was carried to these 5 targets as they were outside the EIA study limit and no physical disturbance of marine works from this project is expected.

15.8.5 The visual inspection of the archaeological investigation area found no visible features or objects of archaeological interest. This may be result of the high sedimentation rates in the area and the extensive disturbance to the seabed from fishing and oyster cultivation or the absence of archaeological features. Due to the proximity of the archaeological investigation area to the coastal archaeological site, Ngau Hom Shek, the potential for such resources cannot be ruled out. However, based on the visual inspection and review of ht site conditions, the archaeological potential is classified, as very low and further investigation is not recommended.

15.9 Landscape and Visual Impact

15.9.1 The landscape and visual impacts and mitigation measures for the SWC are based on the current design and information available. The potentially most significant impacts during the construction and operation phases and the expected residual impacts are described below.

Landscape Impacts

15.9.2 The SWC will have a slight residual landscape impact on the landscape resources of Grassland / Eroded Slopes associated with the Greenbelt (LR1) and Mangrove (LR4) while the Mudflats and Oyster Beds (LR5) will experience a slight to moderate Impact. The resources of Agricultural Areas (LR2), Village Type Development (LR3), Wetlands/Marshes (LR7) will experience a moderate residual landscape impact while the Stream Channel (LR8) will experience a moderate to substantial impact. The resource of Ponds (LR6) will experience a negligible impact.

15.9.3 Areas affected for each Landscape Resource are provided in the table below.

Landscape Character Impacts

15.9.4 Residual Landscape Character impacts to the Agricultural Coastal Lowland Character (LC1) is expected to be moderate. The Greenbelt Foothills (LC2) will experience a slight to moderate residual impact as a result of the SWC, while both the Village Coastal Lowland (LC3) and the Sea Edge (LC4) Landscape Character Zones will experience a moderate to substantial impact.

Tree Impacts

15.9.5 Vegetation at the edges to the Agricultural and Green Belt areas will be affected. The vegetation within the alignment is generally of poor quality. From the most update to Tree Survey Report, 96 trees will be affected by the works of which 17 will be retained. Approximately 45 will be transplanted in the area as part of the tree compensation plan. The unmitigated magnitude of the impacts on this vegetation is considered moderate.

15.9.6 Landscape impacts along Fung Kong Tsuen Road will be limited to the felling of some existing trees for road widening works. 60 trees will be affected including 9 different species. Generally the trees affected are between 4-6m in height. There are 4-5 significant trees adjacent to the road but on the current alignment these trees should not be affected. These significant trees included Celtis sinensis, Delonix regia, Aleurites moluccana, Eucalyptus citriodora and Litchi chinensis.

Visual Impacts

15.9.7 A negligible residual visual impact will be experienced by Military personnel at Castle Peak Firing Range (VSR8), Workers at facilities such as Black Point Power Station and WENT Landfill (VSR9).
15.9.8 A slight residual visual impact will be experienced by Residents of the coastal villages to the west of the SWC (VSR2) and the high-rise residents at Tin Shui Wai (VSR4) and on the Castle Peak upland areas hiking trails (VSR7).

15.9.9 The SWC will result in a slight to moderate residual visual impact for Residents of the coastal villages to the east of the alignment (VSR3), Future CDA adjacent to Lau Fau Shan Road (VSR13), Walkers along the coastal protection area and agricultural areas along the coastline (VSR5) Travellers within Marine Craft on Deep Bay (VSR10) and Travellers on Deep Bay Road (VSR11).

15.9.10 The residents of the village area of Ngau Hom Shek (VSR1) and walkers through the Greenbelt adjacent to Ngau Hom Shek (VSR6) will experience a moderate residual impact as a result of the SWC.

15.9.11 The residual visual impacts upon travellers on the SWC (VSR12) are identified as slight positive. The route over Deep Bay will offer outstanding views to motorists of Deep Bay and the coastlines of North West New Territories and Shenzhen. The bridge design can generally be viewed as a positive aesthetic feature for these travellers.

Overall

15.9.12 All impacts must be considered in relation to the proposed Deep Bay Link Road. The study area overlaps with the study area for the DBL by 350 metres and many of the potential landscape and visual impacts (particularly landscape impacts) are reflected in both studies.