4.1 There will be small loss of backshore vegetation and grass/shrubland due to the construction of footpath to the catwalk. Based on the assessment, a very low impact on terrestrial ecological resources is anticipated. Nevertheless, good construction practices are recommended to minimise or avoid disturbance to surrounding habitats and these should be strictly observed. Specific mitigation measures to protect surrounding terrestrial ecological resources are set out below.
4.2 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 coast of Lung Kwu Chau and their abundance in North Lantau waters is generally greater in late spring to summer (May to August). At this time of peak abundance there are estimated to be approximately 91 dolphin individuals in these waters. Although the impact of the Project on the marine dolphin habitat is medium, by strictly observing the recommended mitigation measures set out below, 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 on dolphins such as the direct and indirect affects of changed water quality due to dredging indicates that no significant impacts are predicted.
4.3 Soft corals have also been identified as marine sensitive receivers in the vicinity of the jetty location. Provided that mitigation measures recommended to safeguard water quality during dredging works are implemented, it is not anticipated that these corals will be adversely impacted.
4.4 The implementation schedule of the recommended ecological mitigation measures is presented in Appendix A. Implementation of theses recommended mitigation measures will be monitored and audited during the construction stage.
4.5 Mitigation measures to prevent or avoid disturbance to terrestrial ecological resources are:
· Reinstate temporary work sites/disturbed areas immediately after completion of the construction.
· Check the work site boundaries regularly to ensure they are not exceeded and that no damage occurs to surrounding natural habitats.
· Prohibit and prevent open fires within the work site boundary during construction and provide temporary fire fighting equipment in the work areas.
4.6 To ensure impacts on dolphins are minimised, the following mitigation measures must be observed.
· The use of high-speed vessels in the construction or operation of the jetty should be avoided where possible. If high-speed vessels must be used, they should be required to slow to under 10 knots which is the speed restriction for all marine traffic inside the Marine Park Boundary. Furthermore, marine traffic entering the Marine Park to the proposed jetty area should follow a regular and predictable route.
· All vessel operators working on the project should be given a briefing, alerting them to the conservation significance of the Marine Park and the presence of dolphins in the area, and setting out guidelines for safe vessel operations around cetaceans.
· A policy of no dumping of rubbish, food, oil, or chemicals should be strictly enforced. This should also be covered in the contractor briefing.
· Every attempt should be made to minimize the effects of construction and operation of the jetty on the water quality of the area. Elevated SS levels due to dredging works for the approach channel and foundation of the jetty and catwalk are not predicted to have a significant impact on dolphins. As a precautionary measure, however, it is considered beneficial to avoid dredging works during late spring to summer (i.e. May-August), when dolphins are at their peak abundance in North Lantau waters, as far as programming constraints allow. It is recommended that the approach channel dredging works avoid the period of late spring to summer.
· The jetty has incorporated a blockwork design with the provision of openings along the bottom of the catwalk to enhance seawater circulation. The most significant possible source of impact on dolphins would be noise damage and disturbance during piling and therefore use of piling has been avoided in the jetty design to avoid the danger posed to dolphins by the associated noise pulses.
· Before dredging the following steps must be taken:
- An exclusion zone of 500m radius should be scanned around the work area for at least 30 minutes prior to the start of dredging. If dolphins are observed in the exclusion zone, marine works should be delayed until they have left the area. Furthermore, if dolphins enter the exclusion zone after dredging has commenced, marine works should cease until they have left the area.
- Staff should monitor for the presence of dolphins within the exclusion zone by scanning the sea both with and without binoculars whilst positioned at vantage point near the summit of the hill behind the jetty location. The vantage point shall enable an extensive view of the 500m exlusion zone in all directions around the jetty. Staff shall communicate with the Engineer via a dedicated telecommunications device (e.g. mobile phone or ‘walkie-talkie’).
· Other measures recommended to mitigate noise impact on dolphins by allowing their acclimatization to noise disturbance are to, as far as practicable:
- The dredging works for the approach channel should avoid the period of peak dolphin abundance in North Lantau waters of late spring to summer (i.e. May-August).
- The number of work vessels and small craft should be minimised during the construction phase.
- Dredging and jetty construction activities should be continuous without short breaks or unpredictable noise outbursts at random intervals.
- Events should be scheduled on a regular basis with similar activities planned for similar time period each day.
- Furthermore, the Contractor should use quiet or ‘silenced’ plant equipment. All site plant equipment should be well maintained.
· Removal of the existing jetty structure should be done in a way that minimises noise impact on dolphins following the above measures. Blasting should not be permitted. Silenced breakers should be used and demolition and removal works of the submerged portion of the jetty should be carried out around low tide to minimise transmittance of noise into the water. In addition, demolition of the jetty structure should be planned so that, as far as practicable, the structure is ‘cut’ into large manageable sections to minimise the amount of time breakers are used.
· During the operational phase, vessels moored at the jetty for extended periods should, as far as practicable, turn off their engines to minimise unnecessary underwater noise.
· Other mitigation measures, including measures to minimize impacts on water quality during dredging works, can be referenced from Section 2, Water Quality.