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.
Ecological Mitigation Measures
Terrestrial Ecology
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.
Marine Ecology
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.