3.1 The nature and extent of the environmental impacts associated with the construction and operation phases of the proposed jetty are summarized below. Specific mitigation measure requirements for the Project, as well as environmental monitoring and auditing procedures, have been developed during the assessment of the preferred jetty location and design option. The Implementation Schedules of the recommendations are presented in the EIA Report.
3.2 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. During mitigated dredging, the sediment plume is shown to be very narrow and localized. The calculated maximum concentrations in the sediment plume 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.
3.3 An assessment of the impact of the proposed jetty on the hydrodynamic regime has been made using a local model. 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. The morphological impact assessment concluded that construction of the jetty and dredging of the approach channel would not impact negatively on the morphology of the nearby beach.
3.4 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 of rocky shore habitat. The impact of the project works on these habitats is concluded to be low.
3.5 The key marine sensitive receiver is the Indo-Pacific Humpback dolphin with the assessment area being high value habitat to this dolphin species. This dolphin is commonly sighted off the north and east coasts of Lung Kwu Chau and their abundance in North Lantau waters is generally greater from late spring to summer. Although the impact of the Project on the marine dolphin habitat is medium, by strictly observing the recommended mitigation measures, 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. As a precautionary measure, dredging of approach channel will be scheduled outside late spring to summer.
3.6 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 north-east 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, sediment plume modelling indicates that increases in sedimentation rates on these corals are minor and would not cause any significant impact.
3.7 The findings of the literature review indicate that the fisheries resources at Lung Kwu Chau 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.
3.8 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.
3.9 The results of the desktop review and archaeological test pits indicate that the distribution of archaeological deposits 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 has no archaeological remains and deposits and hence, no adverse impact to cultural heritage is expected.
3.10 The marine geophysical survey for the marine archaeological investigation (MAI) did not reveal any seabed features with archaeological potential within the assessment area. The MAI concluded that there is no need for any further archaeological investigation nor mitigation measures.
3.11 The sediment quality characterisation survey indicates that the sediments to be dredged are classified as Category L and therefore the sediments are suitable for open sea disposal. Other wastes 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.
3.12 Given that the proposed jetty location is on a small area of shore already subjected to previous disturbance, and the scale of the works 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
3.13 Environmental monitoring and audit are recommended for marine 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 monitoring procedures and locations are presented in a stand-alone Environmental Monitoring and Audit Manual.