Introduction
10.1 This EIA Report has provided an assessment of the potential environmental impacts associated with the construction and operation phases of the proposed Project, “Construction of Lung Kwu Chau Jetty”.
10.2 Alternative transportation modes for servicing and maintaining the DVOR/DME station at Lung Kwu Chau and alternative sitings and design of the proposed jetty have been assessed with regard to their environmental benefits and disbenefits. Construction of the proposed jetty is considered necessary as there are no other modes of transportation available other than by sea to transport the required equipment and personnel to the island and to provide access to facilitate emergency repair work of the DVOR/DME Station. Alternative design options have been addressed for consideration of a preferred option, including refinement of the jetty location, structure and construction methods. A preferred option for the location of the jetty has been selected at the south of the bay at the bulkhead (Option 3, refer to Figure 2.2). Support from the Marine Parks Committee and Lung Kwu Tan villagers for the preferred option for the jetty location has been obtained.
10.3 The environmental issues below have been assessed in the EIA Study, based on the preferred jetty location and design option :
(i)
Marine ecological impact.
(ii) Impact
on capture fisheries.
(iii) Water quality impact associated with dredging works.
(iv) Landscape
and visual impact.
(v) Archaeological
impact to the Lung Kwu Chau Archaeological Site.
(vi)
Waste management implications.
10.4 Specific mitigation measure requirements for the Project, as well as environmental monitoring and auditing procedures, have been developed during the assessments of the preferred jetty option. The Implementation Schedules of the recommendations are presented in Section 11. The principal findings of this Report are summarized below.
Water Quality Impact
10.5 During the construction phase of the proposed jetty, suspended sediment is identified as the most significant water quality parameter. The water quality impact as a result of dredging has been quantitatively assessed using a Particle Dispersion Model to simulate spreading, sedimentation and re-supension of particulate matter. The sediment plume is shown to be very narrow and localized. The calculated maximum concentrations in the sediment plume for the mitigated dredging scenario are predicted to remain very close to the source and are well within the range of natural fluctuations of suspended solids concentrations measured in the assessment area. The implementation of the proposed mitigation measures will be required during the marine works to effectively minimize the sediment loss from dredging activities given the presence of ecological resources in the assessment area. It is concluded that with the adoption of the recommended mitigation measures, the construction works for the jetty are not anticipated to result in unacceptable impacts on water quality. An environmental monitoring and audit programme will be required to monitor and audit the implementation and efficiency of the proposed mitigation measures.
10.6 An assessment of the impact from the proposed jetty on the hydrodynamic regime has been made using a local model. With this quantitative modelling tool, impacts have been assessed for the dry and wet seasons, and for both seasons, the baseline and operation simulations have been compared. It is predicted that the jetty and catwalk structure has a limited effect on the flow regime and on the flushing of water in the nearby bay to the north of the jetty. A morphological impact assessment has also been undertaken to address any potential impacts on the beach located to the immediate north of the jetty. It is concluded that the construction of the jetty and dredging of the approach channel would not impact negatively on the morphology of the nearby beach.
Ecological Impact
10.7 Literature review of existing ecological conditions were supplemented by field surveys of marine ecological resources in the assessment area. This indicated that the ecological value of the intertidal sandy and rocky shore habitats and subtidal soft seabed at Lung Kwu Chau are of low ecological value. Construction of the jetty and associated dredging works will result in the loss of 0.2ha of subtidal seabed area and approximately 0.002ha rocky shore habitat. The impact of the project works on these habitats is low.
10.8 The key marine sensitive receiver is Sousa chinensis with the assessment area being high value habitat to this dolphin species. This dolphin is commonly sighted off the north and east coast of Lung Kwu Chau and their abundance in North Lantau waters is generally greater from late spring to summer (i.e. May to August). At this time of year, the peak abundance in these waters is estimated at 91 dolphin individuals (AFCD unpublished data). Jefferson (2000) also reported peak dolphin abundance during summer in North Lantau waters, which was estimated at 105 dolphin individuals. Although the impact of the Project on the marine dolphin habitat is medium, by strictly observing the recommended mitigation measures set out in Section 4, the impact on dolphins can be minimised to an acceptable level. These mitigation measures primarily address ways to minimise noise impacts and physical dangers posed by marine traffic and works. The evaluation of other potential impacts such as the direct and indirect affects of changed water quality due to dredging indicates that no significant impacts are predicted.
10.9 Common gorgonian corals from the genus Euplexaura sp. were also found in the assessment area. These soft corals were found in abundance attached to a shipwreck on the northeast side of Lung Kwu Chau, while a handful of these corals were found growing on dumped material in the bay of the existing jetty. There would be no direct impact on these corals. In addition, plume modelling of sediments suspended into the water column by dredging indicate that increases in sedimentation rates on these corals are minor and would not cause any significant impact.
Fisheries Impact
10.10 A literature review has been conducted to establish the baseline conditions of the physical environment and the fisheries resources in the assessment area. The findings indicate that the fishing resources at LKC would be considered as low to moderate. Direct impacts to fisheries resources and fishing operations from habitat loss due to the jetty construction and dredging works for the approach channel are regarded as low.
10.11 The sediment plume modelling results indicate that sedimentation rates or turbidity levels in the assessment area’s waters are not elevated to levels that would impact fisheries. Provided that the mitigation measures recommended to protect water quality are fully implemented, specific mitigation measures to protect fisheries resources are not considered necessary.
Cultural Heritage Impact
10.12 The desktop review and archaeological test pits survey indicate that the distribution of archaeological deposits on the Island is confined on the sandy tombolo and along the western beach in the middle part of the Island. The on-shore works area of the proposed jetty construction, however, has no archaeological remains and deposits and hence, no adverse impact to cultural heritage is expected.
10.13 The marine geophysical survey for the marine archaeological investigation did not reveal any seabed features with archaeological potential. Since there are no underwater archaeological resources present within the seabed of the assessment area, there are no related constraints associated with the construction of the proposed jetty. The MAI concluded that there is no need for any further archaeological investigation nor mitigation measures.
Waste Management Impact
10.14 A review of the sediment quality data from the sediment characterisation survey indicates that the sediments to be dredged at the project area are classified as Category L and therefore the sediments are suitable for open sea disposal. With the implementation of the recommended mitigation measures and management procedures in accordance with the requirements of WBTC No. 3/2000, no residual impact is predicted.
10.15 Other wastes generated by the construction works are likely to include C&D material from demolition of the existing jetty and the footpath extension. Provided that these waste arisings are handled, transported and disposed of using approved methods and that the recommended good site practices are strictly followed, adverse environmental impacts are not anticipated during the construction phase. High standards of waste management should be observed to ensure that no waste arisings enter the marine waters of the Sha Chau and LKC Marine Park.
Landscape and Visual Impact
10.16 Given that the proposed jetty is selected to be located on a small area of shore already subjected to previous disturbance, and the scale of the work has been minimised, the landscape and visual impact assessment concluded that the impact is acceptable with implementation of mitigation measures, including sympathetic design with rounded jetty cope line and irregular armour rocks on catwalk, compatible construction materials and finishes e.g. granite stone facing, visually recessive colours, and avoidance of lighting glare to Lung Kwu Tan villagers. Project works would result in small losses of landscape character/resource areas confining to 0.008ha of backshore area, 0.002ha of rocky boulder shore area and 0.03ha of water area.
Environmental Monitoring and Audit
10.17 Environmental monitoring and audit are recommended for construction water quality. Site inspection/audit is also recommended to check the strict implementation of the recommended water quality, ecological and waste management mitigation measures during the construction phase. Details of the recommended mitigation measures, monitoring procedures and locations will be presented in a stand-alone Environmental Monitoring and Audit (EM&A) Manual. This will enable the Contractor to have early warning and provide necessary action to reduce impacts at specific areas if the assessment criteria are approached. All the recommended mitigation measures should be incorporated into the EM&A programme for implementation.
Overall Conclusion
10.18 The findings of this EIA have provided information on the nature and extent of environmental impacts arising from the Project, “Construction of Lung Kwu Chau Jetty”. The EIA has, where appropriate, identified mitigation measures to ensure compliance with environmental legislation and standards.
10.19 Overall, the EIA Report for the Lung Kwu Chau Jetty has predicted that the Project will comply with all environmental standards and legislation after the proposed construction and operational stage mitigation measures are implemented. This EIA has also demonstrated the acceptability of the residual impacts from the Project and the protection of the identified environmentally sensitive resources. Environmental monitoring and audit mechanisms have been recommended before and during construction, where necessary, to verify the accuracy of the EIA predictions and the effectiveness of recommended mitigation measures.