16.1.1 This EIA Report assessed the potential environmental impacts associated with the construction and operation of the SWC project. Based on the Score Table and Sensitivity test results in Section 4, bridge option landing at Ngau Hom Shek would be selected. S-curve bridge is a preferred option over the straight bridge because it improves the angles between the bridge alignment and the navigation channels that would reduce ship impact risks. Also, the varying and interesting views afforded to the drivers and passengers travelling on the bridge is another advantage of the S-curve bridge. This EIA report therefore focuses on the preferred option of s-curve bridge alignment. This chapter concludes the key findings of the assessment.
16.2.1 The major potential air quality impacts during the construction phase of the project would result from dust arising from site clearance and preparation, excavation and filling, open site erosion, concrete batching, precasting of road segments, and handling and transportation of construction and demolition material. Practicable and effective dust suppression measures should be implemented to minimise the dust nuisance arising from the construction activities. In particular, the relevant dust control requirements set out in Parts I, III and IV of Schedule 1 of the Air Pollution Control (Construction Dust) Regulation should be adopted by the site agent while carrying out construction works. The specific measures recommended in the EIA include dust suppression by twice daily watering with complete coverage of all active construction areas and limiting the construction vehicle travel speed on unpaved site areas to not more than 10 km per hour. With the implementation of effective dust control measures, adverse dust impacts from the construction works of the project would not be expected.
16.2.2 The modelling results showed that the worst-case unmitigated construction dust impacts at the existing village houses at Ngau Hom Shek could reach 1012 µgm-3 of 1-hour average TSP level and 375 µgm-3 of 24-hour average TSP level. With the implementation of the proposed dust suppression measures, the dust impacts at the existing village houses at Ngau Hom Shek could be on average reduced by about 60% and 53%, respectively, for the 1-hour average TSP level and the 24-hour average TSP level. The highest residual 1-hour average and 24-hour average TSP level at the village houses at Ngau Hom Shek are predicted to be 435 µgm-3 and 214 µgm-3 respectively and exceedance of the respective AQO and guideline level for TSP criteria is not expected.
16.2.3 Major air quality impacts during the operational phase of the project would arise from the tailpipe emissions of 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 DBL, as well as other planned and existing roads in the area and the stack emissions from major existing and planned sources in the area.
16.2.4 Computer dispersion modelling was undertaken to assess the potential operational phase cumulative air quality impacts due to traffic emissions from the proposed SWC, the future road network in the area and stack emissions from major emission sources. The assessment was based on a conservative assumption that all vehicles travelling on the road network within the assessment area would use fuel with a higher sulphur content and thus with higher emission factors. Another conservative assumption is the use of year 2011 emission factors for design traffic flow at year 2021, given the emission factors would be further improved beyond 2011 due to technology advancement. 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 within the assessment area of the proposed SWC. Mitigation measures for operational phase air quality impacts would therefore not be required.
16.2.5 The predicted highest 1-hour average and 24-hour average nitrogen dioxide level at the worst-affected air sensitive receivers, namely the existing village houses at Ngau Hom Shek, are 82% and 95%, respectively, of the corresponding AQO. The predicted highest 24-hour average respirable suspended particulates level at the air sensitive receivers is 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.
Review of Existing Condition
16.3.1 Parts of the SWC would be constructed on existing rural land lots at Ngau Hom Shek. Existing noise sensitive receivers there would be located close to the SWC alignment and affected by the construction noise and operational noise to a different extent.
Construction Phase
16.3.2 Construction noise assessments were conducted based on the conservative preliminary construction schedule in this preliminary design stage. Due to the close proximity of some of the existing NSRs, noise levels exceeding EIAO-TM criteria were predicted.
16.3.3 To reduce the likely impacts, different forms of mitigation measures were examined 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. All NSRs could be adequately protected by the proposed mitigation schemes and the construction noise levels were predicted to be around Leq 68-75 dB(A) during normal daytime. Residual noise impacts would not be expected after applying the proposed mitigation schemes. The Project Proponent also planned for construction work during restricted hours. This would be under stringent control and the future contractor has to apply for a construction noise permit under the Noise Control Ordinance.
Operational Phase
16.3.4 Traffic noise impacts would be from SWC during its operation. Noise from road traffic was assessed based on the traffic forecast for year 2021 i.e. the worst within 15 years after the completion of SWC and its linking with DBL. Existing NSRs were included in the assessment. With traffic noise mitigation in mind in the planning process, low noise surfacing was adopted as a standard provision under current policy for the SWC and DBL to reduce the road traffic noise impacts. All predicted noise levels at NSRs were found to be within acceptable standard and were around L10 65-70dB(A) during peak hour traffic. All of the dwellings would be protected from adverse impacts.
16.3.5 No residual impacts were identified for the operational phase of the SWC project.
16.4 Hydrodynamics, Water and Sediment Quality Impacts
16.4.1 Both the construction and operational phase impacts arising from the SWC project were assessed. The construction phase impacts would be temporary but the operational phase impacts may have a long-term effect on Deep Bay.
16.4.2 Reclamation on the Shenzhen side and the presence of bridge piers would reduce the discharge capacity across the proposed SWC bridge alignment in Deep Bay. Based on the model results, there was, however, no significant deviation of water quality conditions from the baseline conditions in Deep Bay after the completion of the SWC bridge. The ranges of water quality changes for the case with the Project were rather narrow and were insignificant when compared to the natural fluctuations of water quality conditions in Deep Bay. The changes in sedimentation rates in Deep Bay were also found to be not significant.
16.4.3 Mitigation measures to minimise and control water quality pollution during the construction and operational phases of the SWC project were recommended. With the implementation of mitigation measures, the SWC project would not cause unacceptable water quality impacts to the Deep Bay waters. Construction and operational phase water quality monitoring was recommended to ensure that the Project would not cause unacceptable water quality conditions in Deep Bay.
16.4.4 Vibrocoring and grab sampling were carried out to provide data for determination of the sediment chemical quality and sediment classification for the SWC project. Category L, M and H materials were identified in the SI. Contaminated and uncontaminated sediments were classified based on WBTC No. 3/2000. The estimated contaminated sediment volume for confined marine disposal was 22,500 m3 and uncontaminated sediment volume for open sea disposal was 34,500 m3.
16.4.5 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.
16.5 Waste Management Implications
16.5.1 Potential environmental impacts from wastes of the SWC project were assessed. Effective waste management planning during the construction phase would be the key issue. The operational phase was not expected to generate any amount of wastes.
16.5.2 Waste management methods and practices and other environmental control measures for the construction phase were recommended to ensure that potential impacts would be avoided or mitigated to acceptable levels. Potential environmental impacts associated with wastes from the Project would be insignificant with the proper implementation of all the suggested mitigation measures. The Contractor would be required to formulate an overall Waste Management Plan, and to submit this for the Engineer's approval. The Engineer would ensure that the day-to-day operations on site comply with the approved Waste Management Plans.
16.6.1 The field survey programme of the present project was planned to be an extension of the field surveys for Crosslinks2 EIA study. A 12-month ecological field survey was conducted for Crosslinks2 between 1998-1999. Fieldwork for the present project began in August 2001 and continued through June 2002 to provide another 11 months of survey data covering seasonal variation and the breeding season and autumn and spring migrations of birds.
16.6.2 Among the four topographic zones in outer Deep Bay area (upland, lowland, coastal/intertidal, and marine), the initial phase of the present field studies identified habitats and species in lowland and coastal zones as key issues for ecology within the assessment area.
16.6.3 Due to the clarification of the demarcation mark between the SWC project and the adjacent Deep Bay Link project, the Assessment Area for the SWC was re-defined as the area below the high water mark. The terrestrial part of the area covered by the field surveys of the SWC project is re-named as Study Area, and the information collected in which is used primarily for supplementary purposes.
16.6.4 The ecological baseline study has covered all items highlighted in the Study Brief of SWC EIA, i.e. intertidal mudflat; mangrove; seagrass bed; inter-tidal and sub-tidal benthic faunal communities; egretries; Horseshoe crabs; avifauna, in particular, Black-faced Spoonbill (Platalea minor); and Chinese White Dolphin (Sousa chinensis).
16.6.5 During the field surveys for the present project, two plant species, including Thespesia populnea and the seagrass Halophila beccarii, one marine invertebrate (horseshoe crab Tachypleus tridentatus), one reptile, 25 species of birds, two species of mammals, including Chinese White Dolphin, were recorded within the assessment area and are of conservation concern.
16.6.6 Among those species of conservation concern recorded, however, only the seagrass Halophila beccarii, horseshoe crab Tachypleus tridentatus, and 10 waterbird species including Black-faced Spoonbill are considered that their presence in the assessment area is relevant to the SWC project.
16.6.7 In terms of avoidance, based upon information from literature review and field surveys, it was found in the assessment that the current location of the Shenzhen Western Corridor would cause the least impact to Deep Bay. The current location is 6km from Mai Po Marsh Nature Reserve, 7 km from the mouth of Deep Bay, and 3.5km from Ha Pak Nai. The potential impacts on recognised sites of conservation importance would be higher if the corridor location was further northward (potential impacts on Mai Po), or further southward (potential impacts on Chinese White Dolphin). The current location of SWC is thus considered the most ecologically acceptable if a non land-based western corridor is needed.
16.6.8 The most important form of mitigation, avoidance, has already been pursued through consideration of three alternative sites for the bridge landing. The Ngau Hom Shek was determined to be the least damaging ecologically and the most preferred all round
16.6.9 Tunnel option was found to be less ecologically acceptable due to the need of large scale dredging during construction and the higher reduction o flushing rate during operation.
16.6.10 Several design features of the bridge could effectively minimise ecological impacts, including increasing pier spacing, adopting submerged pile caps, locating cable -stayed structure outside intertidal zone, bridge deck height, and no power line suspended on the bridge.
16.6.11 During construction, the cumulative temporary direct habitat loss will be about 2.7 ha in subtidal zone, and 0.75 ha in intertidal zone, due to construction and use of the temporary bridge, plus 0.25 ha removal of mangrove trees. Only less than 0.001 ha of seagrass might be potentially influenced. Temporary direct BFS feeding ground loss would be 0.139ha. 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. Permanent BFS feeding ground direct loss would be 0.039ha.
16.6.12 The indirect impacts on habitats due to disturbance were investigated through additional filed surveys in other bridge structures in HK and Macau, and analyses of data in other projects. The finding indicates that most birds are disturbance-tolerant. Even Black-faced spoonbill (BFS), which is previously considered much sensitive to disturbance, was observed feeding close to disturbance sources. Precautionary approach is however adopted. In the worst case scenario, in which unforeseeable incidence occurs at the SWC construction sites during winter, the affected BFS feeding ground is estimated to be 0.24 ha in area, which has included the 0.139ha of direct temporary loss. Previous studies indicated that mudflat is only one of the feeding ground types of BFS (the other two are drained fishponds and drained gei wai), and the outer deep Bay (including the mudflat near the SWC alignment) is not the core feeding area of BFS. This 0.24 ha represents a small fraction (1.6%) of the intertidal feeding habitat for BFS along the south shore of outer Deep Bay (some 15 km in length x 10 m in width = 15 ha) which is less important to the BFS than the inner Deep Bay. The temporary loss is predicted to be an undetectable impact. During the operation phase, though there is no evidence to prove that BFS would avoid the mudflat in the vicinity of a bridge, based upon a precautionary approach, and additional 30m on both side of the SWC deck width was included to address this potential impact. The total permanent loss of BFS potential feeding ground, including both direct and indirect, would then be 0.039ha + 0.06ha = 0.099ha. Since a 8.34 ha of mudflat would be restored in operation phase, a 0.139ha tideline (=(39m + 50m + 50m) x 10m) will be provided. After reduction of the 0.099 ha potential loss, there still would be 0.04ha tideline feeding ground for BFS restored.
16.6.13 During construction, dredging, intertidal habitat loss, damage due to construction and use of the temporary bridge may result in minor impacts on mudflats, mangroves, seagrass, and pelagic species.
16.6.14 All other construction impacts would be insignificant in severity.
16.6.15 There would be no cumulative impacts in terms of disturbance. The only cumulative impact identified was an additional ~150ha seabed loss. The loss was insignificant to Deep Bay. Even including the seabed loss from the SWC project, the cumulative seabed loss would be only about 1.3% of Deep Bay. The cumulative impacts from the present project would be acceptable.
16.6.16 Implementation of the recommended mitigation measures would result in no unacceptable residual impacts.
16.6.17 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.
16.6.18 Additional enhancement measures are, however, proposed on a precautionary approach to provide alternative and superior feeding sites for birds 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 Gei Wais in Mai Po as bird feeding ground.
16.6.19 By recovering the level of the bottoms of water channels connecting Gei Wais and Deep Bay, the function of 24.3 ha Gei Wai in Mai Po, which is the core feeding ground of BFS, will be restored. This area would be over 20 times the temporary peripheral feeding ground loss for all birds in the SWC construction phase. This plan will be conducted before the commencement of SWC construction works and the function restoration achieved could last for over a decade.
16.7.1 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.
16.7.2 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.
16.7.3 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.
16.7.4 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.
16.7.5 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.
16.7.6 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 0.196ha of sea areas, were considered to be of minor significance to the fishing industry.
16.7.7 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.
16.7.8 Changes in water quality would be minimal, therefore adverse impacts to fisheries resources are not predicted.
16.7.9 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.
16.7.10 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.
16.7.11 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.
16.8.1 Comparison of different alignment options concluded that the s-curve bridge alignment was the preferred option. Under the requirement specified in the EIA Study Brief, hazard assessment would only be required if there is overnight storage of explosives and the storage location is in close vicinity of populated areas or PHI site. The construction of the s-curve bridge would not involve the use of explosives. Therefore, quantitative assessment on the potential risk due to storage, handling and on-site treatment was not required and hazard to life due to overnight storage of explosives would not be an issue in this Study.
16.9.1 Archaeological survey identified the Ngau Hom Shek Beach Site. A piggery was found to cover almost the entire site. No further archaeological work could be conducted unless the piggery could be moved. The western part of the Ngau Hom Shek Beach Site was found to be located within the impact zone of SWC, and the impact of the proposed landing point Option AB to this site would depend on the specific location of the design. A rescue excavation must be carried out on this site before any earthworks or building works could commence.
16.9.2 For the area west of the NHS-Beach Site, additional archaeological investigation would be carried out once the site is available. If archaeological features are identified in this area, rescue excavation would be required prior to the proposed excavation works in this area.
16.9.3 A Marine Archaeological Investigation (MAI) was carried out for the seabed that would be affected by the Project. The investigated only covered the section of the route in HK territorial waters. There were five Unidentified Targets within the southern section of the study area. However, as these five unidentified targets are outside the 100m EIA Study zone. The proposed works limit is at 50m from both edges of the SWC footpath and therefore there will be no physical disturbance due to the proposed marine works of the project to the seabed of the 5 sites. Therefore, diving inspection for these five unidentified points is not recommended.
16.9.4 Diver inspection is required to cover the area with no data due to extremely shallow water or oyster beds within the strip of land directly beneath SWC footprint. 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 the site conditions, the archaeological potential is classified, as very low and further investigation is not recommended.
16.10 Landscape and Visual Impact
16.10.1 Landscape impact to the rural village character of Ngau Hom Shek (LR3) will be moderate and permanent. Impacts upon mangroves and mudflats (LR4 and 5) will be mitigated in conjunction with ecological mitigation measures and residual impact is expected to be slight and slight / moderate respectively. Residual impacts to wetlands / marshes (LR7) will be moderate and stream channel (LR8) will be moderate to substantial.
16.10.2 Mitigated impact upon the overall landscape quality (inclusive of character areas LC1 - LC4) will vary from slight/moderate to moderate / substantial. Much of the SWC is elevated and physical impacts in the area, whilst being moderate to substantial during construction, are expected to be mitigated for operation. This will involve extensive landscape treatment to the area within Ngau Hom Shek, specifically adjacent to the proposed roadway.
16.10.3 The residual visual impact to Ngau Hom Shek village (VSR1) is expected to be moderate. Views from most other VSRs will be negligible, slight or slight/moderate. Views from most VSRs will see the bridge and associated structures within a backdrop of the development of Shenzhen. When viewed in this context, negative visual impacts are alleviated. In addition, the perception of the bridge as a 'landmark' structure with positive visual attributes should also be considered.
16.10.4 Given the elevated, linear nature of the SWC combined with its scale, it is unlikely the mitigation measures will ever totally visually mitigate the proposal. Planting and the overall design will have an effect on reducing the overall impact on VSRs in comparison to if no mitigation measure were proposed. These mitigation measures include planting to screen the structures as well as designing the structures to an acceptable quality of aesthetics. After 10 years, it is reasonable to expect the planting to grow and therefore enhance the screening measures but it is also envisaged that mature growth will still not screen all the structures.
16.10.5 Overall, it is considered that, in terms of Annexe 10 of the EIAO TM, the landscape and visual impacts are acceptable with mitigation measures.
16.11 Environmental Monitoring and Audit
16.11.1 The environmental monitoring and audit requirements were outlined in this Report. Details of the monitoring procedures and technical requirements are presented in the EM&A Manual.
16.12.1 Based on the assessment results of all the key environmental issues in this Study, no insurmountable environmental impacts were anticipated from the construction and operation of the SWC project. The potential impacts would be minimised to acceptable levels through implementation of mitigation measures. Residual impacts due to the Project were identified to be low.