This section of the EIA report presents the findings
of the marine ecological impact assessment associated with the construction and
operation of the proposed offshore wind farm.
It summarises baseline information on the potentially affected marine
ecological resources and also presents the findings of a field survey
programme. Detailed information on the
baseline conditions and results of the field surveys are presented in Annex
9A.
9.2
Legislative Requirements
and Evaluation Criteria
The criteria for evaluating marine ecological impacts
are laid out in the EIAO-TM and Study
Brief (no. ESB-151/2006). Annex
16 of the EIAO-TM sets out the
general approach and methodology for assessment of marine ecological impacts
arising from a project or proposal. This
assessment allows a complete and objective identification, prediction and
evaluation of the potential marine ecological impacts. Annex 8
of the EIAO-TM recommends the
criteria that can be used for evaluating marine ecological impacts.
Legislative requirements and evaluation criteria
relevant to the study for the protection of species and habitats of marine
ecological importance are summarised below.
The details on each are presented in Annex 9A.
1.
Marine Parks Ordinance (Cap 476);
2.
Wild Animals Protection Ordinance (Cap
170);
3.
Protection of Endangered Species of
Animals and Plants Ordinance (Cap 586);
4.
Town Planning Ordinance (Cap 131);
5.
6.
The Technical Memorandum on Environmental
Impact Assessment Process under the Environmental Impact Assessment Ordinance
(EIAOTM);
7.
United Nations Convention on Biodiversity
(1992);
8.
Convention on Wetlands of International
Importance Especially as Waterfowl Habitat (the Ramsar
Convention); and,
9.
PRC Regulations and Guidelines.
9.3
Summary of
Baseline Conditions
The wind farm and cable route
are located in the waters between
The findings of the literature review and
field surveys and, an evaluation of the ecological importance of marine
resources within the Study Area are summarised in the following section. The details are presented in full in Annex
9A. The ecological resources and importance of
marine habitats have been characterised with reference to the available
literature, comprehensive seasonal field surveys, comparisons with other
similar habitats in
Detailed and comprehensive seasonal
surveys were conducted examining the major habitats and species in the marine
environment surrounding the wind farm site and cable route. The baseline surveys have included both the
dry and wet seasons. The findings of the
field surveys are presented in Annex
9A.
The marine ecological habitats in the
immediate vicinity of the wind farm site and cable route off
The key finding of the literature review
was the recorded presence of finless porpoise Neophocaena phocaenoides in the waters of the Study
Area and inter-nesting green turtles Chelonia
mydas in waters south and southeast of
Due to the limited literature available
for some components of the marine environment, field surveys were necessary to
fill the information gaps identified for the baseline conditions of the
habitats. The baseline surveys commenced
in October 2008 and have included both the dry and wet seasons. These focussed seasonal surveys were
conducted to characterise major marine assemblages and species within and
surrounding the wind farm site and cable route.
Details of the baseline surveys conducted for this EIA are summarised in
Annex
9A.
Table 9.1 Marine Ecology Baseline Surveys
|
Survey Type |
Methodology |
Date |
|
Intertidal Assemblages |
Quantitative (belt transects) survey,
three |
28 October 2008 and 27 February 2009 |
|
Subtidal
Benthic Assemblages |
Quantitative grab sampling survey; covered
both wet and dry seasons. 10 stations sampled to represent the wind farm
site, cable route and reference sites, covering both wet and dry seasons. Drop camera survey |
19 October 2008 and 19 March 2009. 19 March 2009 |
|
Nearshore
dive surveys |
Quantitative (Rapid Ecological
Assessment (REA) technique) and qualitative (recorded within Study Area and
areas in the vicinity) |
4 and 5 May 2009 |
|
Marine Mammal* |
Quantitative vessel based survey using
line transect methods spanning Hong Kong southern waters 1 day a month for 6
months. |
24 December 2008, 16 January 2009, 13
February 2009, 13 March 2009, 15 April 2009 and 11 May 2009. |
|
Qualitative vessel-based survey around |
July to October 2008, and in June 2009,
in the following dates: 24, 26, 28 July 2008, 15, 21, 25 August
2008, 4, 11, 26 September 2008, 6, 17, 20 October 2008, and 10, 11, 17 June
2009 |
*Remarks:
Due to the extensive data available
through the AFCD’s long-term marine mammal monitoring
programme, a six month quantitative survey programme was recommended to
supplement the existing dataset during the peak seasons (winter/spring) of
Finless Porpoise (December to May). In
addition, qualitative vessel-based survey programme was also conducted to cover
the non-peak seasons (July to October).
This proposed survey period covered all seasons, as per the Study Brief
requirement, and was considered sufficient to characterise existing and
historical marine mammal use of the waters of the Study Area.
9.3.1
Ecological Importance
The ecological importance of the habitats
was determined through reference to the following:
·
Literature
review;
·
Findings
of the field surveys;
·
Comparison
with other areas in
·
Annexes 8 and 16 of the EIAO TM.
Key findings and outcomes of the
evaluation of ecological importance are summarised below.
Intertidal Hard Bottom Assemblages
Seasonal quantitative transect surveys
were conducted on the artificial seawall of the Lamma
Power Station Extension. Rocky shore
species at all survey transects were common and widespread and no protected
species or those of conservation interest were recorded. The assemblages recorded are considered to be
of low diversity and low ecological importance.
Subtidal
Soft Bottom Assemblages – Benthos
Seasonal systematic grab sampling was
conducted within and in proximity to the footprint of the wind farm site and
cable route. In both seasons, infaunal assemblages at the surveyed sites were dominated
by polychaete worms, and the species recorded are
common and widespread species with no particular conservation concern. The abundance, biomass and taxonomic richness
of infauna at these sites are considered as very low
in comparison with the
Subtidal
Hard Bottom Assemblages – Coral
Qualitative and semi-quantitative REA
surveys were conducted on the artificial seawall of the Lamma
Power Station Extension and on hard substrate identified along the proposed
cable route. Only three hard coral
species were recorded on the artificial seawall, and a total of four octocoral species and one black coral species were recorded
on the dumped material in vicinity of the cable route. These locally common and widerspread
coral species with little conservation interest occurred as very scarce
colonies with extremely low coverage.
Given such low coral abundance and diversity at the surveyed sites the
ecological importance of the associated assemblages is considered as low.
Sea Turtles
A small number of green turtles are known
to nest on the Sham Wan beach in southern Lamma. Satellite tracking data suggested that these
turtles may use the southern and southeastern waters
of Lamma as inter-nesting habitats during June to
October. It is noted however, that these
data are initial and hence turtles may be present in other marine areas around Lamma and the nearby islands. Nevertheless the tracking data imply that
turtles stay relatively close to inshore coastal areas and hence the ecological
importance of waters within the wind farm footprint to sea turtles
(particularly green turtles) is considered to be low.
Finless Porpoise
Quantitative grid analysis on porpoise
habitat use revealed that during 2004-08, standardised porpoise sighting
densities (SPSE values) were higher at the waters just south of Soko Islands, the offshore waters in Southeast Lantau, at southwest corner of Shek
Kwu Chau and Cheung Chau, near Stanley Peninsula and around Po Toi Islands than in other areas of Hong Kong waters ([1]). Vessel-based standard line transect surveys
were undertaken in the Lamma Survey Area over a
6-month period from December 2008 to May 2009 (Winter / Spring). A total of five groups of porpoises (total
abundance = 13 individuals) were sighted on-effort during the surveys. Additional data was also collected during
Summer and Autumn months during the qualitative surveys. During this period one group of porpoises was
recorded (total abundance = 2 individuals).
Quantitative survey data were combined
with AFCD’s long-term porpoise monitoring data from
December 1999 for quantitative grid analysis, and the results showed that the
porpoise densities (SPSE values) were considered as moderate to high and low to
moderate for the proposed wind farm site and along cable route
respectively. The ecological importance
of these areas is considered as medium-high and low-medium respectively (Table 9.2).
Table 9.2 Ecological Importance of the Marine
Habitats
9.3.2
Marine Ecological Sensitive Receivers
Based on the results of the marine
ecological surveys and a review of the available information on existing
conditions in the Study Area, the key sensitive receivers that may be affected
by the proposed works associated with the Project are identified as follows:
·
Finless
Porpoise habitat within and around the wind farm site; and,
·
The
·
Sea
Turtles.
The locations of the sensitive receivers
identified are shown in Figure
6.4
(see Section 6).
A desktop literature review and supporting
field surveys (summarised in Section 9.3
and detailed in full in Annex
9A)
were conducted in order to establish the ecological profile of the Study
Area. The Study Area for the ecological
assessment covers a large area of open water to provide information on the
distribution on local habitats that could be affected by development proposals
and also to ensure that linkages to wider habitats that could be affected by
water quality impacts are considered.
This relatively wide Study Area, the same as adopted for the water
quality impact assessment (Section 6)
also ensures that consideration is given to mobile species that are present in
the area. The importance of potentially
impacted ecological resources identified within the Study Area was assessed
using the methodology defined in the EIAO-TM. The potential impacts due to the construction
and operation of the wind farm and associated infrastructure were then assessed
(following the EIAO-TM Annex 16 guidelines) and the impacts
evaluated (based on the criteria in EIAO-TM
Annex 8).
9.5
Potential Sources
of Impact on Marine Intertidal and Subtidal Resources
9.5.1
Construction Phase
Potential impacts to marine ecological
resources arising from the construction works may be divided into those due to direct
disturbances to the habitat, and those due to perturbations to key water
quality parameters. Potential impacts to
marine mammals and sea turtles are discussed separately.
As discussed in Section 5, the construction of the proposed offshore wind farm will
involve removal of the seawall at Lamma Power Station
Extension, dredging and jetting for cable installation and the construction of
foundations for the wind turbines, offshore wind monitoring mast and offshore
substation. Impacts associated with the
proposed wind farm are thus divided into those occurring during:
·
Removal
of the existing Lamma Power Station Extension sea
wall;
·
Dredging
and jetting for cable installation and construction of foundations for wind turbines,
the wind monitoring mast and the offshore substation.
Removal of the existing
In order to connect the submarine cable to
land, the existing rubble mound seawall at the west shore of the Lamma Power Station Extension will be exposed for
installation of a steel cable slipway.
Approximately
Impacts to the marine ecological resources
potentially arising from sea wall removal and reinstatement are as follows and
summarised in Table 9.3.
Table 9.3 Summary
of Potential Construction Phase Impacts associated with Seawall Removal and
Reinstatement
|
Nature of Impact |
Marine Habitat Affected |
Potential Impact |
|
Habitat Loss |
Intertidal
Artificial Shore |
Temporary
loss of approximately |
|
Subtidal Hard Bottom Habitat |
Temporary
loss of approximately |
|
|
Short term Changes in Water Quality |
Subtidal Hard Bottom Habitat |
Potential
water quality impacts on subtidal organisms |
|
|
Intertidal
Artificial Shore |
Potential
water quality impacts on intertidal organisms |
Habitat Loss
Subtidal Hard Surface Habitats (including Corals)
The removal of the seawall will lead to a
temporary loss of low ecological value subtidal hard surface
habitats. Although isolated colonies of
corals have been recorded in this area, they are composed of common species
with very low abundance and diversity.
The reinstatement of the seawall with
existing materials once the steel cable slipway has been constructed will mean
that there will be no long term change in the amount of available hard
substrate habitat. It is anticipated
that assemblages of subtidal organisms, including
corals, will settle on and recolonise the newly
constructed seawall, as environmental conditions of that area would be similar
to existing conditions that have allowed the colonisation and growth of subtidal organisms.
Intertidal Artificial Shore Habitat
A length of approximately
Changes in Water Quality
The area that will be disturbed by
construction works consists of boulders that form the seawall structure. Removal of the seawall is therefore unlikely
to release significant quantities of fine sediments into the water column. Therefore water quality impacts associated
with sea wall removal are expected to be negligible.
Dredging and Jetting for Cable
Installation and the Construction of Foundations
There will be a requirement to undertake
grab dredging within approximately
Impacts to the marine ecological resources
potentially arising from dredging and jetting activities are as follows and
summarised in Table 9.4.
Table 9.4 Summary of Potential Construction Phase
Impacts associated with Dredging and Jetting Activities
|
Nature of Impact |
Marine Habitat Affected |
Potential Impact |
|
Habitat Loss |
Subtidal Soft Bottom Habitat |
Temporary
loss of a maximum of Permanent
loss of a maximum of |
|
|
Subtidal Hard Bottom Habitat |
Permanent
loss of very small patches of hard substrate formed by dumped material in
vicinity of the cable route. |
|
Short term Changes in Water Quality |
Subtidal Soft Bottom Habitat |
Potential
deposition of sediment on benthic organisms during dredging/jetting |
|
|
Subtidal Hard Bottom Habitat |
Potential
water quality impacts on subtidal organisms |
|
|
Intertidal
Artificial Shore |
Potential
water quality impacts on intertidal organisms |
Habitat Loss
Subtidal Soft Bottom Habitats
Primary impacts will be associated with the
temporary disturbance of sediments during grab dredging and jetting, potential
removal of organisms during dredging and permanent loss of habitats associated
with the construction of wind farm foundations.
It is important, therefore, to determine
whether the areas of disturbance contain unique or otherwise noteworthy benthic
assemblages, which will be lost.
Findings from the literature review, supplemented by focussed field
surveys, indicate that the benthic assemblage within and in the vicinity of the
working areas were dominated by polychaetes and
characterised by low species diversity and biomass as found elsewhere in Hong
Kong. All of the species recorded occur
frequently in
It is expected that the disturbed areas
within the footprint of dredging or jetting works will naturally be reinstated
through sediment infill. This will occur
very rapidly for jetting activities during the works as disturbed sediments
will subsequently settle over the cables.
For grab dredging, the reinstatement may take longer, but it is likely
that the seabed will return to its existing state in the short term due to the
highly mobile nature of sediments in the area.
It is expected that the direct impacts to subtidal
soft bottom habitats include the permanent loss of
The soft bottom habitat will be replaced
by hard rock bottom habitat, which has potential for colonisation, generation
of new biomass and increased productivity in the area (see Section
Subtidal Hard Surface Habitats (including Corals)
Small patches of dumped material ([2]) were
recorded in vicinity to the cable route in the area where jetting is proposed
(see Annex
9A). Dive surveys carried out at these points
confirmed that these areas appeared to have been disturbed by trawling
activity. The survey also confirmed that
although hard substrate was recorded in these areas, the seabed is
predominantly composed of soft muddy habitat.
Abundance and species diversity of epibenthic
fauna in these areas was low and largely composed of sparse records of
gorgonians. All of the species recorded
occur frequently in
Changes
in Water Quality
Suspended
Sediments
The modelling works have analysed
suspended sediment (SS) dispersion from dredging, jetting and foundation
construction activities (see Section 6). The following presents a discussion of the
effects of predicted changes in water quality on marine ecological resources.
Subtidal Soft Benthos: The subtidal soft
benthos in and around the proposed wind farm and cable route is considered to
be of low ecological value (see Annex
9A);
however, these sessile organisms will be susceptible to the effects of
increased sediment loads in the water column.
Sediment may also be deposited on the seabed as a result of settling of
sediments disturbed during dredging/jetting.
Impacts to benthic assemblages are expected
to occur over a short duration. The area
is expected to be small as sediment will be deposited within a short distance
of the dredging, jetting and foundation construction works. With reference to the water quality modelling
results, elevations in suspended sediment levels would be localised and
confined to the works area. The largest
impacts are expected in the immediate vicinity of the marine construction works
(in the mixing zone) with impacts on the wider marine environment (in terms of
con-compliance with the expected to be negligible (see Section 6).
As the area is often disturbed by demersal trawling, the organisms present are thus assumed
to be adapted to seabed disturbances.
The affected areas will be recolonised by
fauna typical of the area and hence the temporary loss of these low ecological
value assemblages is deemed acceptable.
Subtidal Hard Surface Habitats (including Corals): As discussed above, small patches of hard
substrate associated with dumped material were recorded in vicinity to the
cable route. A dive survey of these
areas identified coral assemblages of low conservation value (including soft
corals, gorgonians and black corals).
The dive survey also noted that these areas were subject to a large
amount of fine sediment deposition with hard substrate areas covered by fine
sediments. In addition, trawling
activity was evident in these areas. The
drop camera survey indicated that the majority of the seabed in the wind farm
site and along the cable route was composed of soft sediments. The modelling study determined that
relatively high levels of suspended sediment will occur in the mixing zone at
the seabed adjacent to the cable route will be short term and acceptable.
The dive survey carried out at the Lamma Power Station seawall identified the presence of
isolated colonies of hard corals of low ecological value on the artificial rock
substrate. Modelling work has determined
that grab dredging and jetting works would lead to increased suspended
sediments in this area. However, impacts
were seen to be very localised and transient.
The main species noted from the surveys was Oulastrea crispata. This coral species is known to have high
tolerance limits to fluctuations in salinity, sea surface temperature (daily
and seasonal), sedimentation loading, total suspended sediment and light
attenuation levels (see Annex
9A)
and is most often recorded in the most marginal conditions for corals, i.e.,
areas of high sediment loading, and represented by scattered, small colonies in
shallow, subtidal areas with few other coral species ([3]).
The deposition rates during the dry and wet seasons
have been determined through modelling (see Section
Intertidal
Habitats: Intertidal
habitats within the Study Area, which may be affected by the dredging and
jetting activities, are associated with the artificial Lamma
Power Station Extension seawall. With
reference to the water quality modelling results (Section 6), elevations in SS levels are predicted to be localised
and short term. Furthermore, the adoption
of appropriate mitigation, such as the use of silt curtains during dredging at
the seawall area, is expected to significantly reduce the amount of sediments
released in the areas where intertidal habitats are present. Due to the low quality of the intertidal
habitats identified within the Study Area and transient nature of any increase
in suspended sediment, adverse impacts to the intertidal assemblages are not
anticipated.
Dissolved
Oxygen
The
results of the water quality assessment (see Section 6) has indicated that predicted changes in DO levels would
comply with the WQO at all sensitive receivers for all construction scenarios
(see Section 6). It is expected, therefore, that unacceptable
impacts to marine ecological habitats and populations present in the vicinity
of the wind farm site and cable route, including marine mammals and sea turtle
habitats, as a result of changes in DO levels are unlikely to occur.
Nutrients
High levels of nutrients (total inorganic
nitrogen - TIN and ammonia) in seawater can cause rapid increases in
phytoplankton to the point where an algal bloom may occur. An intense bloom of algae can lead to sharp
increases in DO levels in surface water.
However, at night and when these algae die there is usually a sharp
decrease in the levels of dissolved oxygen in the water, as dead algae fall
through the water column and decompose on the bottom. Anoxic conditions may result if DO
concentrations are already low or are not replenished. This may result in mortality to marine
organisms due to oxygen deprivation.
The assessment of potential increases in
nutrient levels resulting from construction activities is discussed in Section 6. The results show that increases are predicted
to be very small and compliant with the WQO.
The increased level of nutrients in the water column as a result of
works is considered to be of negligible significance to marine ecological
resources.
Contaminant
Release
Another potential impact to marine
ecological resources associated with disturbance of bottom sediment is the
release of potential toxic contaminants.
The potential for release of contaminants from dredged sediments has
been assessed in Section 6, whereas,
a comprehensive set of data on the quality of marine sediment is provided in Section 7. Elutriate tests that have been carried out in
the area of grab dredging show that dissolved metal concentrations for all
samples are below the reporting limits.
The results also show that all PAHs and PCBs
and chlorinated pesticides are all below the reporting limits. This indicates that the leaching of these
pollutants is unlikely to occur. Impacts
to marine ecological resources due to released contaminants from dredged
sediments are therefore not expected to occur.
9.5.2
Operation Phase
Hydrodynamic Regime
The presence of offshore structures may
lead to changes in hydrodynamic processes.
If these changes are significant there could be potential for increased
current velocities and direction, which may cause scour of seabed sediments or
changes to existing hydrodynamics and hence local and far-field erosion and
sedimentation patterns.
The change to current velocities has been
determined (see Section 6) and has
through modelling that has indicated that the new structures will have little
effect on existing hydrodynamics and hence local erosion and sedimentation
patterns. There is potential for scour
around the base of turbines and offshore substation. However, if significant scour is expected to
occur during further assessment in the Detailed Design Phase then it is likely
that scour protection will be installed to prevent such affects from occurring
(see Section 5). In addition, scour would be short term and
stop once an equilibrium condition forms (see Section 5).
Water Quality
Section
6
has assessed the potential for water quality impacts during the operational
phase. The impacts that have been
considered include:
·
Increase
in suspended sediment levels due to scour of seabed sediments around the base
of foundations of wind turbines and offshore substation;
·
Potential
for vessel discharges; and,
·
Discharge
of other materials (oils, hydraulic fluids etc) contained within the
structures.
The consideration of these impacts has
determined that with the adoption of appropriate operational management
procedures and other mitigation measures the potential for release would be
very low. The use of scour protection at
the base of foundations would reduce the potential for the release of sediments
into suspension. It is therefore
anticipated that negligible impacts should occur to marine ecological resources
associated with water quality impacts during the operational phase.
Increased Subtidal
Hard Bottom Habitat
The new offshore structures and scour
protection (if used) will provide hard substrate habitat in the wind farm
area. These structures could be
colonised by a variety of marine organisms, including corals. There is considerable knowledge in
It is expected that rock scour would give
higher surface complexity than monopiles providing
nooks and crannies between individual rocks, which would increase the
attractiveness to colonising organisms.
Indeed, since 1996, AFCD have been implementing an artificial reef
programme in
Colonisation of these structures could
provide long term benefits associated with the attraction of fish and marine
invertebrates (including shrimp) into the area.
This could go some way towards offsetting the loss of habitat discussed
above.
9.6
Evaluation of The
Marine Ecological Impacts on Intertidal and Subtidal Resources
The following section discusses and
evaluates the impacts to marine ecological resources as a result of the
resources identified in the previous sections.
Based upon the information presented above, the significance of the
marine ecological impact associated with the construction and operation of the
offshore wind farm has been evaluated in accordance with the EIAO-TM (Annex 8, Table 1) as follows.
·
Habitat Quality: Impacts are predicted to occur only to
habitats of low ecological value (inter-tidal and subtidal). The selection of the wind farm site has
avoided direct impacts to habitats of high ecological value. Operational phase impacts are not expected to
impact any habitats of high ecological value.
·
Species: Based on literature and field surveys, no
organisms of ecological interest were identified in proximity to wind farm site
and cable route. Marine ecological
sensitive receivers were situated at distant locations from the proposed
works. Although some isolated coral
colonies are present, no significant construction or operational phase impacts
are expected to these sensitive receivers.
·
Size: The maximum size of the temporary loss of
artificial intertidal habitats at the Lamma Power
Station Extension is
·
Duration: The construction works are predicted to last
for 9 months. However, individual works
will only require a relatively short period of time to complete and
construction phase impacts are predicted to be transient in nature as the
location of the works will be changing over time. The operational phase of the wind farm will
be long term (25 years) and therefore discharges and hydrodynamic impacts will
continue during the life of the wind farm, but are predicted to be very minor
and hence are not expected to cause adverse impacts to marine ecological
resources.
·
Reversibility: Impacts
to the benthic assemblages inhabiting the soft bottom habitats within the
dredged/jetting areas are expected to be relatively short term and recolonisation of the disturbed sediments is expected to
occur. Similarly the low ecological
value assemblages present on the artificial seawall can be expected to recolonise once the seawall is reinstated.
·
Magnitude:
No
unacceptable impacts to ecologically sensitive habitats have been predicted to
occur. Operational phase impacts are not
expected to cause adverse impacts and are considered to be of low magnitude.
The impact assessment presented above
indicates that no unacceptable impacts to marine ecological resources
considered in the above sections are expected to occur. Although soft bottom habitat will be
temporarily lost, it has been demonstrated through long-term monitoring of
previously dredged areas and existing Contaminated Mud Pits in the East of Sha Chau area that marine
organisms have recolonised the areas following the
completion of the works ([7]). As such, it is anticipated that subtidal assemblages influenced by dredging and jetting
will settle on and recolonise the seabed returning it
to the former conditions.
Impacts to marine ecological resources
during operation of the wind farm are predicted to be minor.
9.7
Potential Sources
of Impact on Marine Mammals
In this section of the report, the
potential for impacts associated with various proposed marine works and
activities are examined in detail to provide an assessment of the significance
of the effects on the finless porpoise.
The significance of a potential impact from works or activities on
marine mammals can be determined by examining the consequences of the impact on
the affected animals. This is related to
the source, nature, magnitude and duration of the impact, the level of exposure
to the impact in terms of the number (and life-stage) of affected animals and
their response to an impact.
The consequences of an impact on these
marine mammals have the potential to range from behavioural changes of
individual animals through to population level effects ([8]) ([9]) ([10]). The potential consequences of impacts on
marine mammals are as follows:
·
Behavioural changes: Affected
individual animals may change travelling speed, dive times, avoid areas, change
travel direction to evade vessels, change vocalisation due to acoustic
interference, reduce resting, socialising and mother-calf nursing. Provided that disturbances leading to
behavioural changes are temporary, localised and outside areas of ecological
importance to marine mammals, disturbances causing behavioural changes would
generally not be considered significant (i.e. effects would be of short
duration, normal activities will resume with no appreciable effect on fitness
or vital rates).
·
Life function immediately affected: Avoidance
of affected areas may diminish individual animals’ feeding activity. Loss of a marine area to reclamation will
permanently eliminate a foraging area.
Similarly, disturbance/loss of prey resources due to water quality
impacts may diminish available feeding opportunities in the vicinity of works.
Interference with echolocation through underwater sound generation could also
affect feeding. Provided that
disturbances are temporary, localised and outside areas of ecological
importance to marine mammals, or permanent losses of habitat represent a small
portion of available habitat, impacts would generally not be considered to have
a significant effect on marine mammals (i.e. effect would be short term and
therefore have no appreciable effect on fitness or vital rates).
·
Fitness and Vital Rates: If
works cause widespread and prolonged adverse impacts, with limited or no
alternative habitat available for animals to use, fitness and vital rates will
be affected including growth rates, reproduction rates and survival rates
(life-stage specific). In the same way,
any works or activity likely to result in injury or mortality of marine mammals
would self-evidently affect survival rates.
Activities causing impacts on fitness and vital rates would be
considered significant (i.e. if effects are long-term or inescapable, they will
diminish the health and survival of individuals).
·
Population effect: Impacts
on the fitness and survival of individuals have the potential to, for instance,
affect population growth rates and population structure. Impacts resulting in population effects would
be considered significant (i.e. if effects are long term and detrimental to the
population as a whole).
9.7.1
Construction Phase
The impacts associated with the proposed
wind farm development that could affect marine mammals will include:
·
Dredging
and jetting for cable installation; and
·
The
construction of foundations for wind turbines and associated infrastructure (ie monitoring mast and offshore substation).
Dredging
and jetting for cable installation
There
will be a temporary disturbance
It
is noted that the area within the wind farm layout has been considered to be of
medium to high ecological value. The
installation works for the intra-array cables is also expected to cause minor
and short term impacts to marine sediments.
Information from the fisheries impact assessment (see Section 10) indicates that the
disturbance of marine habitat due to the cable installation works is not predicted to adversely impact the fisheries resources that would be
available in the waters within and surrounding the wind farm site and cable
route (the fisheries resources in the marine habitat serve as marine mammal’s
food prey). Consequently,
adverse impacts associated with the loss of food resources to finless porpoise
are not expected.
Water
Quality Impacts
High
SS levels do not appear to have a direct impact on porpoises. Porpoises are air breathing and therefore SS
in the water column has no effect on their respiratory surfaces. Impacts may occur to these mammals as an
indirect result of increased SS levels.
The construction of the wind farm and installation of the cable route
may cause perturbations to water quality, which have the potential to impact
the fisheries resources. However, information from the fisheries impact assessment (Section 10) indicates that indirect impacts are not predicted to
adversely impact fisheries resources as the SS elevation are localized to the
works areas. The consequences of this
are that impacts to marine mammals through loss of food supply (fisheries
resources) are not predicted to occur.
It is thus expected that unacceptable impacts to marine mammals arising
from elevated SS levels will not occur.
Contaminant
Release
Another
potential impact on marine mammals associated with disturbance of bottom
sediment that requires assessment is the potential for release contaminants
affecting the food chain. The potential
for release of contaminants from disturbed seabed sediments has been assessed
in Section 6.
The
results of EPD sediment monitoring at relevant stations has been presented in Section 7. The data show that the sediments in the local
area of the wind farm site are relatively unpolluted. The levels of heavy metals, Polycyclic
Aromatic Hydrocarbons (PAHs) and Polychlorinated
Biphenyls (PCBs) are such that the sediments can be considered as
uncontaminated.
A
nearshore sediment survey in the area where grab
dredging is proposed determined that the sediments in this area are
uncontaminated (see Section 7). Elutriate tests that have also been carried
out for sediments collected in the area of grab dredging and the data show that
dissolved metal concentrations for all samples are below the reporting
limits. The results also show that all PAHs and PCBs and chlorinated pesticides are all below the
reporting limits.
As
unacceptable water quality impacts due to the potential release of heavy metals
and micro-organic pollutants from dredging, jetting and foundation construction
works are not expected to occur, impacts to marine mammals are not expected to
occur.
Potential
Impacts from Works Vessels (all marine works)
Increased marine traffic: The construction of the wind farm and cable
route will require the use of marine vessels, including a jack-up barge, tug,
safety vessel and personnel transfer vessel.
This will increase traffic flow in the area with the potential to result
in an increase in marine traffic which may affect the finless porpoise.
In
Hong Kong, there have been instances when dolphins in
The
effect of the physical presence of work vessels and other vessels on porpoise
would be limited to temporary behavioural disturbance of a number of animals,
if and when encounters with vessels occur.
It would be expected that these animals may avoid the operating vessels
in the vicinity of the works areas.
The
animals have a relatively large range and therefore any works areas avoided
would constitute a very small portion of the waters they inhabit. In addition, through specific mitigation
measures, marine percussive piling works related to the turbine installation
will not be undertaken during December to May during the peak season of finless
porpoise based on the historical sightings data (see Annex
9A). As such, impacts associated with the
increased marine traffic are not considered to be significant.
Underwater sound: Construction of the wind farm structures
(e.g. turbines, wind monitoring mast and offshore substation) and cable
installation has the potential to result in a short term increase in underwater
sound from marine vessels, which may temporarily disturb the finless
porpoise. Mitigation measures applied to
control marine traffic would also help to reduce adverse impacts through vessel
sound.
Foundation
Construction - Potential Impacts from Piling Works
One
of the primary potential impacts of piling construction is the effect of noise
from the pile driving on marine mammals.
Underwater sound may potentially affect marine mammals by causing the
following hazards ([13]):
·
Potential for injury or fatality of marine
mammals from exposure to significant levels of underwater sound or any
associated pressure effects;
·
Disturbance, leading to behavioural changes
or displacement;
·
Interference with communication; and
·
Interference with echolocation pulses used
by certain marine mammals for the location of prey and other objects.
Little systematic information is however
available about the impacts caused by underwater sound generated during
offshore windfarm construction ([14]).
As discussed in Section 4, percussive piling has been selected as the preferred
construction method for the installation of the proposed offshore structures
(i.e. wind turbines, wind monitoring mast and offshore substation). Sound produced during percussive piling
propagates through the air into water, through the water column, and to a
lesser degree, through the sediment and from there successively back into the
water column. Underwater sound
generation from percussive piling is however transient in nature and the
overall timeframe for the piling of a foundation will be short term.
Recent studies undertaken by the UK
Government’s body on Wind Farm Research (COWRIE - Collaborative Offshore Wind
Research Into The Environment) collected measurements of sound levels created
during percussive piling for wind turbines on five wind farms throughout the
North Sea ([15]). Source levels during the measured pile
driving operations varied between 243 and 257 dB re 1 Pa at 1 metre, having an
average value of 250 dB re 1 Pa at 1 metre.
The study reported that measurements of > 130dB level (from which
marine mammals may suffer physical injury or permanent damage to hearing ([16]))
were found not to exceed a few hundred metres and hence stated that a static
harbour porpoise at a typical range of 250 metres could be exposed to the sound
during the entire pile driving operation without harm. In addition, impacts to marine mammals from
percussive piling operations associated with wind turbine installations in
offshore waters can be significantly reduced by avoidance of marine percussive
piling works for turbine installation during peak season of finless porpoise,
adopting soft-starts procedures and strictly controlled marine mammal exclusion
zones ([17]). As such, impacts on the behavioural
disturbance and habitat displacement of marine mammals are not considered to be
significant.
Other mitigation measures such as ensuring
that porpoise activity is monitored during works so to avoid works when animals
are present, will mean that piling works are only likely to lead to behavioural
changes close the working area and that animals will move to areas less
affected during the short term piling activity.
The adoption of mitigation to ensure that marine mammals are outside of
the area of works will ensure that impacts on behavioural changes will not be
unacceptable (see Section 9.11).
Provided effective mitigation measures, no
unacceptable residual impacts regarding underwater sound on marine mammals
would therefore be expected if percussive piling is undertaken for the
construction of foundations for the proposed marine structures (i.e. wind
turbines, wind monitoring mast and offshore substation).
9.7.2
Operation Phase
Vessel Traffic
Similarly to the discussion of underwater
sound impacts associated with increased vessel traffic during the construction
phase, no unacceptable impacts are expected during the operational phase. Indeed, impacts should be much smaller and
more transient during the operational phase.
Habitat Loss
There will be a permanent loss of a
maximum of
Increased Food Resource
Information from the
fisheries impact assessment (see Section
10) indicates that the
permanent loss of marine habitat is not predicted to adversely impact the fisheries resources that would be
available in the waters within and surrounding the wind farm site and cable
route. Section 10 also discussed potential impacts associated with the
creation of hard substrate as a result of the construction of support
structures and scour protection (if used) (see Section 5). It is
anticipated that these structures could be colonised by a variety of marine
organisms supported by similar effects in
Underwater Sound
The operation of the wind farm will have the
potential to generate low levels of underwater sound. As the wind farm development is located in an
area with existing marine traffic and near to areas with high marine traffic,
it is likely that most porpoise are habituated to these sound levels and the
low levels of marine traffic associated with the operation of the wind farm
would be negligible in comparison ([18]). Consequently, no unacceptable impacts
associated with underwater sound generation during the operation of the wind
farm are therefore expected.
9.8
Evaluation of The
Impacts to Marine Mammals
The following section discusses and
evaluates the impacts to marine mammals identified in the previous
section. Based upon the information presented
above, the significance of the marine ecological impact associated with the
construction and operation of the offshore wind farm has been evaluated in
accordance with the EIAO-TM (Annex 8,
Table 1) as follows.
·
Habitat Quality:
The development of the proposed offshore structures including wind turbines,
wind monitoring mast and offshore substation will lead to a maximum loss of
approximately
·
Species: Organisms of ecological interest reported from
the literature and field surveys include the finless porpoise. This area is not considered to be important
for Indo-pacific Humpback dolphins with very few sightings recorded (see Annex
9A). Significant impacts are not predicted to
occur associated with water quality perturbations as these are predicted to be
transient and compliant with the water quality objectives. Only indirect, temporary disturbance to
marine mammals are expected during marine piling works, as construction
methodologies have been designed to reduce underwater sound transmission. Operational phase marine vessel movements or
underwater sound generation are not expected to impact marine mammals present
in the area.
·
Size: Jetting and dredging works will lead to the
disturbance of approximately
·
Duration: The marine construction works will occur over
a period of 9 months. However,
individual activities will be much shorter in duration with piling of each
foundation being undertaken in the order of hours/days and the cable
installation occurring over a few weeks.
Increases in SS levels in the vicinity of sensitive receivers are
expected to be low and temporary, and within environmentally acceptable limits. Operational impacts are considered minor and
will occur over the lifetime of the wind farm (estimated to be 25 years).
·
Reversibility: The
only permanent impacts to porpoise are likely to be from loss of seabed
(maximum of
·
Magnitude:
As
changes in water quality are localised and transient, no unacceptable impacts
to porpoises have been predicted to occur during the construction or
operational phase.
The impact assessment presented above
indicates that with the adoption of appropriate mitigation measures, no
biologically significant impacts to individual marine mammals whose home ranges
overlap with the proposed project area are expected to occur. Impacts to marine mammals during operation of
the offshore wind farm are predicted to be negligible.
9.9
Potential Sources
of Impact to the
In this section of the report, the
potential for impacts associated with various marine works and activities
involved in the proposed project are examined in detail to provide an
assessment of the significance of the potential impacts to the potential Southwest
Lamma Marine Park which is at least
9.9.1
Habitat Disturbance and Alternation
Since the proposed marine park is at least
9.9.2
Secondary Impacts
Secondary impacts to the associated
species may arise from the potential of increased noise impact, water quality impact,
marine traffic, human activities and disturbance. Section
6 has considered the potential impacts of the construction works on water
quality within the
9.10
Potential Sources
of Impact to Sea Turtles
In this section of the report, the
potential for impacts associated with various marine works and activities
involved in the proposed project are examined in detail to provide an assessment
of the significance of the potential impacts to sea turtles that nest at Sham
Wan beach approximately
9.10.1
Construction Phase
Habitat Disturbance and Alteration
As discussed in Annex
9A
the area where works are proposed does not provide suitable feeding habitat for
sea turtles (particularly green turtles) although the adjacent algal-covered
rocky reefs surrounding
The wind farm site encompassing the wind
turbines, wind monitoring mast and offshore substation is located some distance
from the green turtle nesting site at Sham Wan and no direct impacts in terms
of habitat loss to this nesting site will occur. Recent satellite tracking data has determined
that the inter-nesting movements of a green turtle in 2008 are over a large
area with areas to south and southeast of
Satellite tracking data and international
studies indicate some plasticity in the areas used by green turtles during the
inter-nesting season, which would suggest that alternative locations could be
used if disruption to a specific area within the inter-nesting habitat were to
occur ([22])([23])([24])([25])([26]) . Furthermore, sea turtles are agile
swimmers ([27]) and
able to carry out long distance offshore migration by the use of visual, wave,
and magnetic cues ([28]). Satellite tracking studies ([29]) ([30]) indicated
that green turtles often utilise coastal areas during migration between nesting
and foraging grounds. Given that the
wind farm site is located away from the shore and Sham Wan beach, sea turtles
are therefore unlikely to be affected.
The disturbance of habitats during the
construction phase is therefore anticipated to be of negligible significance to
sea turtles.
Water Quality Impacts
Suspended sediment associated with
construction activities may also temporarily reduce the visibility for sea
turtles. Section 6 has considered the potential impacts of the construction
works on water quality. The results show
that impacts are localised and transient and elevations of SS would not reach
the Sham Wan area where turtle nesting occurs.
Impacts on sea turtles associated with the change in water quality are
therefore not expected.
Potential Impacts from Works Vessels (all
marine works)
Increased
marine traffic: As discussed for marine mammals, the
construction of the wind farm and cable route will require the use of marine
vessels. This will increase traffic flow
in the area with the potential to result in an increase in marine traffic which
may affect sea turtles.
In terms of potential impacts arising due
to increased vessel traffic, the risk of vessel collision is considered to be
very small as work vessels would be slow moving and sea turtles are agile
swimmers. It would be expected that sea
turtles may not be affected whilst works vessels are in operation. In addition, there are relatively high of
marine traffic moving in the areas where sea turtles inhabit (see Section 10) and it is highly likely that
they are habituated to these movements.
The increase in vessel traffic in comparison to baseline movements is
also very low. Negligible impacts to sea
turtles associated with the presence of the construction related vessels are
predicted.
Underwater
sound: The construction of the wind farm structures
including wind turbines, wind monitoring mast and offshore substation, and
cable installation has the potential to result in a minor and short term
increase in underwater sound from marine vessels and dredging, which may affect
the sea turtle to navigate during inter-nesting or migration periods. Sea turtles are noted in areas where there
are existing levels of marine traffic and it is likely that individuals are
habituated to these sound levels passing overhead or nearby. It is noted that during both construction and
operation only a limited number of vessels will be used with appropriate
measures applied to control movements (see Section
9.12.4). A small increase in vessel
activity compared to those vessels that currently pass through these waters and
thus a slight increase in underwater sound generation from dredging activities
are expected to have negligible impacts on any sea turtles passing through the
area.
Foundation Construction - Potential
Impacts from Piling Works
As with the discussion of impacts on
marine mammals, piling activities have the potential to have impacts on sea
turtles navigation through underwater sound generation.
There has been limited study on the
effects of underwater noise on sea turtles through piling operations, however,
studies related to offshore oil and gas seismic exploration using airguns found
that sea turtles exhibit some indication of avoidance from source levels above
175 dB re 1 μPa ([31]). As noted in Section
There does not appear to be evidence from
the literature that construction of offshore wind farms are resulting in
adverse behavioural impacts to sea turtles.
As discussed above, the wind farm site is located some distance from the
shore and recorded nesting site at
Overall, there will be no adverse and
unacceptable impacts to sea turtle during the construction of wind farm,
mitigation measures specifically designed to minimise the potential impact are
not considered necessary. However, it is
considered that the soft-start/ramp-up procedures and enforcement of an
exclusion zone recommended to mitigate against impacts to marine mammals would
also allow sea turtles sufficient time to avoid close proximity to construction
works. With the adoption of these
mitigation measures, it is concluded that impacts on sea turtles from
underwater sound through piling works are only expected to be of negligible
significance.
9.10.2
Operation Phase
Vessel Traffic
Similarly to the discussion of underwater
sound impacts associated with increased vessel traffic during the construction
phase, no unacceptable impacts are expected during the operational phase. Indeed, impacts should be much smaller and
more transient during the operational phase.
Habitat Loss
There will be a permanent loss of a
maximum of
Underwater Sound
Similar to the consideration of underwater
sound generation from piling activities for marine mammals, the operation of
the wind farm has potential to disturb sea turtles. The sound levels are also expected to be less
than that generated by marine vessels at a similar distance. No unacceptable impacts associated with
underwater sound generation during the operation of the wind farm are therefore
expected.
Light Pollution
As discussed in Section 5, lighting of offshore structures is proposed for aviation
and navigation safety. Lighting will
include steady low intensity red lights (aviation) and flashing yellow lights
(navigation) the navigational lights at corner of the wind farm will be visible
for 5 nautical miles (
There is evidence that artificial lighting
on nesting beaches can disturb the nesting process of sea turtles ([32]). However, as the sites for the proposed
project are
Lights
on the turbines also have the potential to disturb the offshore dispersal of
hatchlings at night. Upon emergence, sea
turtle hatchlings use a number of visual cues to orient themselves to the
ocean. In particular, they use light
cues to orient themselves towards the brightest direction, usually the
reflective surface of the ocean ([33]) ([34]). Lighting adjacent to nesting beaches can
therefore disorient hatchlings and compromise their dispersal. However, disturbance from light is dependent
on the intensity and wavelength of the emitting source. Long wavelength light (eg.
red light) has minimal effect on hatchlings and hatchlings are most attracted
to short wavelength light (1) ([35]) ([36]). The lowest intensity light reported to
attract sea turtle hatchlings was 0.12 x 1014 quanta/sec/cm2
(at a wavelength of 375 nm). The low
intensity continuous red aviation lights on the proposed project are not
expected to affect hatchling dispersal due to the minimal effect of this
wavelength on hatchlings and the long distance from the nesting beach of the
proposed sites. Furthermore, the intermediate
yellow flashing navigation lights will not affect hatchling dispersal as their
range is only 2 nautical miles, which is shorter than the distance between the
proposed sites and the Sham Wan nesting beach.
Only the corner navigation lights (visible for 5 nautical miles) would
potentially be visible from the Sham Wan nesting area. There is also a small hill (
9.11
Evaluation of The
Impacts to the
The following section discusses and
evaluates the impacts to the
·
Habitat Quality:
The development of the proposed offshore structures including wind turbines,
wind monitoring mast and offshore substation will lead to a maximum loss of
approximately
·
Species: Significant impacts on sea turtles are not predicted
to occur associated with water quality perturbations as these are predicted to
be transient and compliant with the WQO.
There will be no unacceptable elevations of SS within the
·
Size: Jetting and dredging works will lead to the
disturbance of approximately
·
Duration: The marine construction works will occur over
a period of 9 months. However,
individual activities will be much shorter in duration with piling of each
foundation being undertaken in the order of hours and the cable installation
occurring over a few days. Increases in
SS levels in the vicinity of sensitive receivers are expected to be low and
temporary, and within environmentally acceptable limits. Operational impacts will be negligible
occurring over the lifetime of the wind farm (estimated to be 25 years).
·
Reversibility: The
only permanent impacts to turtles are likely to be from loss of seabed (maximum
of
·
Magnitude:
No
unacceptable impacts to affected individual sea turtles have been predicted to
occur during the construction or operational phase – particularly with the
adoption of appropriated mitigation for percussive piling if this approach will
be taken forward for foundation construction.
Secondary impacts to the potential
The impact assessment presented above
indicates that with appropriate mitigation and precautionary measures, no
biologically significant impacts to individual sea turtles whose home ranges
overlap with the proposed project area are expected to occur. Impacts to sea turtles during operation of
the terminal are predicted to be negligible.
9.12.1
General
In accordance with the guidelines in the EIAO-TM on marine ecology impact
assessment, the general policy for mitigating impacts to marine ecological
resources, in order of priority, are:
·
Avoidance: Potential impacts should be avoided to the
maximum extent practicable by adopting suitable alternatives;
·
Minimisation: Unavoidable impacts should be minimised by
taking appropriate and practicable measures such as constraints on the
intensity of works operations (eg dredging rates) or
timing of works operations; and
·
Compensation: The loss of important species and habitats
may be provided for elsewhere as compensation.
Enhancement and other conservation measures should always be considered
whenever possible.
To summarise, this initial assessment of
impacts demonstrates that impacts have largely been avoided during the construction and operation of the offshore wind
farm and cable route, particularly to the key ecological sensitive receivers
(marine mammals and sea turtles), through the following measures:
·
Avoid Direct Impacts to Ecologically
Sensitive Habitats: The wind farm site has been selected based on
a review of alternative locations (Section
3) and avoided the key habitats for porpoise being, which includes the
waters just south of Soko Islands, the offshore
waters in Southeast Lantau, at southwest corner of Shek Kwu Chau
and Cheung Chau, near Stanley Peninsula and around Po
Toi Islands (2004 – 2008 sightings data – see Annex
9A). The nearshore area
immediately to the southwest of
·
Avoid Indirect Impacts to Ecologically
Sensitive Habitats: The wind farm site has been selected so
dispersion of sediment from dredging and sand filling does not affect the
receivers at levels of concern.
·
Adoption of Acceptable Working Rates: The modelling work has demonstrated that the
selected working rates for the dredging will not cause unacceptable impacts to
the receiving water quality.
Consequently, unacceptable indirect impacts to marine ecological
resources have been avoided.
9.12.2
General Measures for Marine Ecological
Resources
The following measures to mitigate the
impact of the construction and operation on marine ecological resources are
recommended:
·
The vessel operators will
be required to control and manage all effluent from vessels;
·
A policy of no dumping of rubbish, food, oil, or chemicals will be
strictly enforced. This will also be
covered in the contractor briefings; and
·
The effects of construction of the Project on the water quality of the
area will be reduced as described in the Water
Quality section (Section 6).
9.12.3
Specific Measures for Corals
As a total of four octocoral
species and one black coral species were recorded during the baseline surveys
on the dumped material in the vicinity of the cable route, prior to the
commencement of jetting works for the cable route, a pre-construction survey
will be undertaken at these sites to confirm the coral existence. Should these corals be found present,
mitigation will be applied to be agreed with the AFCD at that time. Potential mitigation may include relocation
of these corals to a location away from the proposed area of works.
9.12.4
Specific Measures for Marine Mammals
Measures to mitigate the impact of the construction and
operation of the terminal have been developed in consultation with
internationally recognised marine mammal experts. The following recommendations may be considered to
reduce potential construction and operation impacts on marine mammals.
·
All vessel operators working on the Project construction or operation
will be given a briefing, alerting them to the possible presence of marine
mammals in the area, and the guidelines for safe vessel operation in the
presence of cetaceans. If high speed
vessels are used, they will be required to slow to 10 knots when passing
through a high density porpoise area (southwest of Lamma
Island and around the edges of the wind farm site). With implementation of this measure, the
chance of boat strike resulting in physical injury or mortality of marine
mammals will be extremely unlikely.
Similarly, by observing the guidelines, vessels will be operated in an
appropriate manner so that marine mammals will not be subjected to undue
disturbance or harassed;
·
The
vessel operators will be required to use predefined and regular routes, as
these will become known to porpoise using these waters. This measure will further serve to minimise
disturbance to marine mammals due to vessel movements; and,
During piling works, the following additional measures will be adopted:
·
Using
good engineering practice, including the use of appropriately sized piles (smaller
piles generate lower levels of underwater sound) and piling equipment. This includes:
-
Quieter hydraulic hammers
should be used instead of the noisier diesel hammers; and,
-
Acoustic decoupling of
noisy equipment on work barges should be undertaken.
·
Using ramp-up piling procedures. This comprises of low energy driving for a
period of time prior to commencement of full piling. This will promote avoidance of the area by
fish when sounds levels are not injurious.
Blow frequency during this ramping up period should replicate the
intensity that would be undertaken during full piling (e.g. one blow every two
seconds) to provide cues for marine mammals to localize the sound source. Pile blow energy should be ramped up
gradually over the ‘soft start’ period. Activities will be continuous without short-breaks and avoiding sudden
random loud sound emissions.
·
An
exclusion zone of
·
When
a marine mammal is spotted by qualified personnel within the exclusion zone,
construction works will cease and will not resume until the observer confirms that
the zone has been continuously clear of the marine mammal for a period of 30
minutes. This measure will ensure the
area in the vicinity of the piling is clear of the marine mammal during works
and will serve to reduce any disturbance to marine mammals;
·
Consistent
with standard Hong Kong practice, the percussive pile driving will be conducted
during the day time for a maximum of 12 hours, avoiding generation of
underwater sounds at night time; and
·
Piling
works for the wind turbines shall not be carried out from December to May to
avoid the peak season of finless porpoise.
During dredging works, the following additional measure will be adopted:
·
A
marine mammal exclusion zone within a radius of
Periodic re-assessment of mitigation
measures for marine mammals and their effectiveness will be undertaken through
pre-, during and post-installation monitoring programmes during construction
phase (see Section
9.12.5
Precautionary Measures for Sea Turtles
As discussed in Section
9.10, mitigation measures specifically designed to minimise potential
impacts to sea turtles are not considered necessary as there will be no
significant adverse impacts to sea turtles during the construction and
operation of wind farm. However, it is
noted that a marine mammal exclusion zone will be implemented during piling
works for the wind turbines and dredging works for the cable. It is considered prudent to conservatively
also apply this exclusion zone to sea turtles.
As such the same measures used during the enforcement of the exclusion
zone should be applied to observations of sea turtles as with marine
mammals.
9.13
Residual
Environmental Impacts
Taking into consideration the ecological
value of the habitats discussed in the previous sections and the resultant
mitigation and precautionary measures, residual impacts occurring as a result
of the proposed offshore wind farm have been determined and are as follows:
·
The
maximum loss of approximately
·
The
loss of approximately
·
Long
term beneficial impacts associated with the creation of an ‘artificial reef’
system within the wind farm site, supported by reduced fishing in the area,
which could be of importance in terms of improving the abundance and diversity
of marine fauna in the area and providing improved food resource for marine
mammals.
9.14.1
Project Specific Cumulative Impacts
The cumulative impacts of the various
project specific construction activities have been demonstrated in Section 6 – Water Quality as not causing
unacceptable impacts to water quality.
Consequently, unacceptable cumulative impacts to marine ecological resources
are not predicted to occur. The only
operation cumulative impacts are associated with marine traffic movements
during the construction phase. However,
the impacts associated with the development of the offshore wind farm are not
considered to be significant with respect to the low numbers of vessels
involved and heavy levels of marine traffic already in the area.
9.14.2
Cumulative Impacts with Other Development
As for the cumulative impacts with other
developments in southern and southeastern
·
Open
Sea Disposal of Mud at South Cheung Chau, which is at
least
·
Marine
Burrow Area at West Po Toi, which is at least
·
Exhausted
Sand Burrow Pit for Disposal of Uncontaminated Mud at East Tung Lung Chau (currently not in use), which are at least
·
Open
Sea Disposal of Mud at Ninepin Islands and, which is at least
·
Proposed
Hong Kong Offshore Windfarm in Southeastern
Water, which is at least
Results of water quality modelling
undertaken as part of this EIA Study (see Section
6 for details) showed that sediment plumes from the construction of wind
farm were limited to within about
Since the water quality mixing zone of
this Project is unlikely to overlap with those of other concurrent projects in
this part of
Project-specific adverse operation phase
impacts on marine ecological resources are not expected to occur (Sections
9.15
Environmental
Monitoring and Audit
The following presents a summary of the
Environmental Monitoring and Audit (EM&A) measures focussed on ecology
during the construction and operation phases of the offshore wind farm. Full details are presented in the separate
EM&A Manual.
9.15.1
Construction Phase
During the construction phase, the
following EM&A measures will be undertaken to verify the predictions in the
EIA and ensure the environmental acceptability of the construction works:
·
Water
quality impacts will be monitored and checked through the implementation of a
Water Quality EM&A programme (refer Section
6 for details). The monitoring and
control of water quality impacts will also serve to avoid unacceptable impacts
to marine ecological resources.
·
Marine
piling works will be undertaken using hydraulic hammers, which typically have
lower sound output than traditional diesel hammers;
·
Marine
piling works will take place in daylight hours, sunrise to sunset;
·
Marine
piling works will avoid peak seasons of marine mammals (December to May);
·
Marine
piling works will employ ‘soft-starts’ using ramp-up piling procedures;
·
Pre-,
during and post-installation monitoring of marine mammal abundance, behaviour
and distribution will be undertaken.
Prior to the commencement of
monitoring, methods may include the following to be agreed with the AFCD:
·
Vessel
based surveys
·
Passive
acoustic monitoring
·
Land-based
theodolite tracking
Details of the methods for the above
monitoring works will be elaborated in the EM&A Manual.
·
A
marine mammal / sea turtle exclusion zone will also be implemented and
monitored by qualified observers for the presence of marine mammals / sea
turtles in waters surrounding any marine percussive piling works and dredging
works during construction of the wind farm structures and cable route; and,
·
As a
total of four octocoral species and one black coral species
were recorded during the baseline surveys on the dumped material in the
vicinity of the cable route, prior to the commencement of jetting works for the
cable route, a pre-construction survey will be undertaken at these sites to
confirm the coral existence. Should
these corals be found present, mitigation will be applied to be agreed with the
AFCD at that time. Potential mitigation
may include relocation of these corals to a location away from the proposed
area of works.
Details of the marine mammal exclusion
zone monitoring components are presented in full in the EM&A Manual.
9.15.2
Operation Phase
The assessment presented above as
indicated that operational phase impacts are not expected to occur to marine
ecological resources. No marine ecology
specific operational phase monitoring is considered necessary.
The proposed offshore wind farm
development and cable route area was studied in detail through a site selection
study in order to select a preferred site that avoided to the extent practical,
adverse impacts to habitats or species of high ecological value.
Potential construction phase impacts to
marine ecological resources, as well as impacts to marine mammals and sea
turtles, may arise from the permanent loss of habitat in the footprint of
marine structures, disturbances to benthic habitats as a result of jetting and
dredging and impacts on intertidal and subtidal
habitats during seawall removal.
As impacts arising from the proposed
dredging works are predicted to be largely confined to the specific works areas
and the predicted elevations of suspended sediment due to the Project are not
predicted to cause exceedances of the water quality
objectives outside of the mixing zones, adverse impacts to water quality, and
hence marine ecological resources or marine mammals and sea turtles, are not
anticipated.
Although the loss of
The
loss of
The removal of low ecological value
artificial rocky shore as a result of seawall removal activities for cable
landing (see Section 5) will not lead
to unacceptable impacts for subtidal or intertidal
ecology. The reinstatement of the
seawall with materials that have been removed will mean that there will be no
long term change in the amount of available artificial intertidal and subtidal hard bottom habitat.
Percussive piling has the potential to
cause impacts to marine mammals, and to a lesser extent, sea turtles through
underwater sound generation. With the
adoption of mitigation that has been identified, such as marine mammal/sea
turtle exclusion zones and closed periods for piling works during peak season
of finless porpoise, no unacceptable impacts on these species are
expected.
Operational phase adverse impacts to
marine ecological resources are not expected to occur. In particular, unacceptable impacts to marine
mammals and sea turtles from the generation of underwater sound levels are not
predicted to be of concern. In addition,
the wind farm structures, and in particular rock scour material, may have the
potential to create an artificial reef, which could have beneficial impacts
related to food supply for marine mammals.
No unacceptable residual impacts are
predicted to marine ecological resources.
During construction phase of wind
turbines, pre-, during and post-installation monitoring of marine mammal
abundance, behaviour and distribution will be undertaken.