In
accordance with EIA Study Brief No. ESB-198/2008,
the potential marine ecological
impacts arising from the dredging works for providing sufficient water depth in
The main objectives of this assessment are
to: examine the flora, fauna and other components of the ecological habitats
within the Study Area; evaluate the marine habitat and ecological resources
found within the Study Area; identify, predict and evaluate any direct or
indirect and on-site or offsite impacts to marine ecology in accordance with
the criteria stipulated in Annexes 8 and 16 in Technical Memorandum on
Environmental Impact Assessment Ordinance (EIAO-TM); and recommend practicable
alternatives, if any, or mitigation measures to prevent or minimise adverse
impacts on the marine ecology to an environmentally acceptable level. The
findings of the assessment are structured as follows:
Section 5.2:
Provides discussions on existing environmental legislation, standards, guidelines and criteria;
Section 5.3: Describes the assessment methodology adopted for this EIA;
Section 5.4: Provides a description on the baseline conditions & marine
ecological sensitive receivers;
Section 5.5:
Provides discussions on the ecological importance;
Section 5.6:
Describes the prediction and
evaluation of environmental
impacts due to the Projects;
Section 5.7:
Proposes mitigation measures to
address the adverse environmental
impact;
Section 5.8:
Provides discussions on the cumulative impact;
Section 5.9: Evaluates the residual impacts;
Section 5.10:
Proposes appropriate environmental monitoring and auditing programme; and
Section 5.11:
Summarises the key findings of this section.
Assessments
have been conducted in accordance with the requirements of the Study Brief and Annexes 8 and 16 of the Technical Memorandum on the Environment
Impact Assessment Process. Potential impact of loss of soft-bottom seabed
habitat, indirect disturbance impact to off-site habitat, direct collision and
indirect disturbance to the marine mammals have been assessed. It was found
that both the potential impact
of loss of soft-bottom seabed habitat due to the dredging works and indirect disturbance impacts to
off-site habitats induced by the elevation of suspended solid concentration in
the water column and the increase in sedimentation rate are expected to be minor. The potential impacts regarding the
direct collision and indirect disturbance to the marine mammals during the
dredging activities and operation are anticipated to be negligible. Details of
the assessment are further elaborated in the following subsections.
The
potential cumulative impact of the increase in suspended solids at marine
ecology sensitive receivers including coral communities at
5.2
Environmental
Legislation, Standards, Guidelines and Criteria
A number of international conventions, local legislation and guidelines provides the framework for the protection of species and habitats of ecological importance. Those related to the Project are as follows:
¡ Wild
Animals Protection Ordinance (Cap 170);
¡ Protection
of Endangered Species of Animals and Plants (Ordinance (Cap 586);
¡ Town
Planning Ordinance (Cap 131);
¡ The
Technical Memorandum on Environmental Impact Assessment Process under the
Environmental Impact Assessment Ordinance (EIAO-TM);
¡ EIAO
Guidance Note No. 11/2004 Methodologies for Marine Ecological Baseline Surveys;
¡ United
Nations Convention on Biodiversity (1992);
¡ Convention
on International Trade in Endangered Species of Wild Flora and Fauna (CITES);
¡ Convention
on the Conservation of Migratory Species of Wild Animals (the
¡ IUCN Red Data Books; and
¡ PRC
Regulations and Guidelines.
Under the Wild Animals Protection Ordinance (Cap.170), designated wild animals are protected from being hunted, whilst their nests and eggs are protected from destruction and removal. All birds and most mammals including all cetaceans are protected under this Ordinance, as well as certain reptiles, amphibians and invertebrates. The Second Schedule of the Ordinance that lists all the animals protected was last revised in June 1992.
The Protection of Endangered Species of Animals and Plants Ordinance (Cap. 586) was gazetted on 10 March 2006 to replace the previous Animals and Plants (Protection of Endangered Species) Ordinance. The new Ordinance was effective on 1 December 2006, which aims to regulate the import, introduction from the sea, export, re-export and possession or control of certain endangered species of animals and plants and parts and derivatives of those species; and to provide for incidental and connected matters.
The Town Planning Ordinance (Cap. 131) provides for the designation of areas such as “Coastal Protection Areas”, “Sites of Special Scientific Interest (SSSIs)”, “Green Belt” and "Conservation Area” to promote conservation or protection of significant habitat.
Annex 8 of the EIAO-TM recommends the criteria that can be used for evaluating ecological impacts, while Annex 16 sets out the general approach and methodology for assessment of ecological impacts arising from a project or proposal, to allow a complete and objective identification, prediction and evaluation of the potential ecological impacts.
EIAO Guidance Note No. 11/2004 Methodologies for Marine Ecological Baseline Surveys elaborates on Annex 16 of the EIAO-TM to provide information on the requirements of marine ecological baseline study. The Note provides general guidelines for conducting a marine ecological baseline survey in order to fulfil the requirements stipulated in the EIAO-TM in respect of marine ecological assessment for the proposed development.
The Peoples’ Republic of China (PRC) is a Contracting Party to the United Nations Convention on Biological Diversity of 1992. The Convention requires signatories to make active efforts to protect and manage their biodiversity resources. The Government of the Hong Kong Special Administrative Region has stated that it will be “committed to meeting the environmental objectives” of the Convention (PELB 1996).
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is an international agreement between Governments. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The
Convention on Migratory Species of Wild Animals (
The PRC in 1988 ratified the Wild Animal Protection Law of the PRC, which lays down basic principles for protecting wild animals. The Law prohibits killing of protected animals, controls hunting, and protects the habitats of wild animals, both protected and non-protected. The Law also provides for the creation of lists of animals protected at the state level, under Class I and Class II. There are 96 animal species in Class I and 156 in Class II. Class I provides a higher level of protection for animals considered to be more threatened.
The
Study Area for marine ecological
impact assessment is defined as the same assessment area for the
Water Quality Impact Assessment
and any other areas likely to be impacted by the Project in accordance with
Condition 3.4.7.2 as set in EIA Study Brief No. ESB-198/2008. It includes the Victoria Harbour Water Control Zone (WCZ), Western
Buffer WCZ, North Western WCZ and
A combination of desktop literature reviews and
ecological surveys was conducted in order to establish
an ecological profile
for impact assessment in accordance with the Condition 3.4.7.4 (iv) set
in EIA Study Brief No. ESB-198/2008. Existing wildlife uses of various habitats with special attention to
those wildlife groups and habitats, including coral communities, important
benthic communities and inter-tidal habitats and marine mammals in the context
of the Project were investigated and described. The importance of marine ecological resources
identified within the Study Area and the potential impacts due to the dredging
works were assessed in
accordance with the
criteria and guidelines for evaluating and assessing ecological impact stipulated
in Annexes 8 and 16 of
the EIAO-TM.
5.3.1
Literature
Reviews
Extensive information on the marine ecological resource within the Study Area was reported in various studies. Relevant baseline information was gathered in order to establish an ecological profile of the Study Area through reviewing the relevant literature including previously approved Environmental Impact Assessment reports, scientific publications and environmental studies.
5.3.2
Field
Surveys
In addition to the general review of marine
ecological information in the Study Area, updated site specific information was
also obtained through field surveys to secure an accurate impact assessment,
particularly in those areas that are likely to be subject to direct loss or
indirect impact. For this purpose, inter-tidal field surveys, benthic grab
sampling and sub-tidal dive surveys were conducted between September 2009 and January
2010 to fill information gaps in the baseline information, in accordance with
Condition 3.4.7.4(iii) as set in the EIA Study Brief.
5.3.2.1
Inter-tidal
community survey
Qualitative walk through and quantitative
transect methods were used to survey the inter-tidal communities of the
surveyed sites (refer to
Figure 5.2 for locations of sites)
in September and October 2009 for the wet season and January 2010 for the dry
season. Walk
through surveys were conducted for seven selected sites at Tsing Yi, Kwai Chung,
The
semi-sheltered rocky shore interspersed with cobble beach on Green Island and
the rocky shore and sandy beach on Kau Yi Chau were surveyed by the vertical
transect method. Owing to the inaccessibility of the artificial dolosse at
Stonecutters Island and southern Tsing Yi, and vertical seawalls in Kwai Chung
and Tsing Yi, the transect method was difficult to be applied on these areas;
only qualitative walk through surveys were conducted at these locations. Also, given
the compressed vertical distribution of the coastal communities on artificial
seawall, vertical transect method may not be able to fully present the
distribution of inter-tidal communities on these areas. As such, the vertical
transect method was only conducted at the hard shore on the rather gentle
gradient at
5.3.2.2
Benthic
grab sampling
Nine sites
in the
At each site, three grabs of 0.1m2 were
collected using a modified van Veen Grab. Collected samples were washed with
seawater in a 0.5mm sieve onsite and then stained in 20% buffered formalin
solution, using Rose Bengal as the staining
medium. Samples were then rinsed with freshwater over a
0.5mm mesh in the laboratory. Organisms were sorted from the sediments and
preserved in 70% ethanol solution. Subsequently, benthic organisms were
identified to the lowest practicable taxonomic level by marine benthic
specialists. Species
composition, abundance and biomass were recorded, with Diversity
index and evenness index provided for evaluating and ranking the ecological
values.
5.3.2.3
Sub-tidal
dive survey
Spot dive surveys
were conducted in
December 2009 in and around the areas that have the potential for coral
assemblage. The proposed dredging area in
Spot
Dive Survey
Characteristics of the coral communities encountered were recorded by suitably trained and qualified SCUBA divers swimming at random depths along predetermined transects. Surface parameters including temperature, time and date information were recorded before the dive began. Parameters including the estimated number of species, coral cover, partial mortality and the presence of any rare corals were then recorded during the actual dive.
In particular, any aspect which was significantly different about the coral areas encountered was noted, including non-typical reef structures, unusual coral species associations, unique or peculiar assemblages of the local Incipient Reef formations, and reefs that are almost completely dominated by one particular species.
Dives surveys were conducted in representative locations as shown in Figure 5.2. Data was recorded on water proof paper during the dive in preparation for a later consolidation in a Preliminary Survey Report. Once all of the Spot Dive Survey data was collected on an area, this information was then summarized and a subsequent Rapid Ecological Assessment (REA) survey was conducted.
CoralWatch
Survey
The
CoralWatch was also carried out to determine the current health of the coral
communities encountered. This survey technique provides a simple method of
monitoring the condition of hard corals by the use of simple graded colour
charts underwater. The
All recorded corals were surveyed using the CoralWatch Chart. A total of ten coral colonies were examined in-situ and the lightest and darkest colour match was determined. Data was recorded on prepared underwater sheets for later analysis. Care was taken to avoid recording the colour of the tips of the corals since there can be a delay in the colouration due to the required up-take time for zooxanthellae to enter the coral tissue.
CoralWatch data was collected for each transect. The numerical difference, the colour score, was calculated for each colony. The data was presented for each colony, and then grouped into the corresponding blanching categories with the percentage of corals in each category determined. The data was then averaged so that the figure for Cumulative Average could be calculated.
Rapid
Ecological Assessment (REA) Survey
The
Rapid Ecological Assessment (REA) methodology was first detailed by DeVantier et al. 1998. The survey is a two tier approach for underwater survey
to assess the sub-littoral substrata and benthic organisms in an area. This
methodology has been modified to suit
¡ Tier I assesses the relative cover of major benthic groups and substrata; and
¡ Tier II provides an inventory of sedentary / sessile benthic taxa, which are also ranked in terms of their abundance in the community at the survey site.
Data was recorded by experts who are experienced in the field identification of sedentary / sessile benthic taxa, particularly corals.
Tier I : Categorisation of benthic cover
For each transect, ecological and substratum attributes would be categorised and ranked. The required attributes are detailed as follows:
Table 5.1: Tier I Benthic Attribute Categories
Ecological Attributes |
|
Substratum Attributes |
Hard Corals |
|
Hard substrata |
Dead coral |
|
Bedrock / continuous pavement |
Octocorals (Soft corals black and gorgonians) |
|
|
Anemone beds |
|
|
Dead standing corals |
|
Rubble |
Other benthos (sponges, zoanthids, ascidians and bryozoans |
|
Other |
Macro-algae |
|
Soft substrata |
|
|
Sand |
|
|
Mud / Silt |
|
|
Mud |
Table 5.2: Tier I Ordinal Ranks of Percentage Cover of Benthic Attributes
Rank |
Percentage Cover |
0 |
None recorded |
0.5 |
1-5% |
1 |
6-10% |
2 |
11-30% |
3 |
31-50% |
4 |
51-75% |
5 |
76-100% |
Note: For substratum attributes, it is preferable to record the actual estimates of cover. The percentage of hard substrata vs soft substrata can then be provided (e.g. 80% and 20% respectively). The percentage cover of the types of hard or soft substrata could also be presented (e.g. bedrock pavement 60%, rubble 20%, sand 15%, mud/silt 5%). Similarly, recording and presenting actual estimates of, for instance, hard and soft coral cover may be more informative (e.g. <1%) and is also the approach adopted by similar recent survey reports.
Table 5.3: Taxonomic inventory Identification
Taxon Abundance Rank |
Abundance |
0 |
Absent |
1 |
Rare |
2 |
Uncommon |
3 |
Common |
4 |
Abundant |
5 |
Dominant |
The taxon categories were ranked in terms of relative abundance of individuals, rather than the contribution to benthic cover along each transect. The ranks were visual assessments of its abundance, rather than the quantitative counts of each taxon. Representative photos of organisms were also taken.
The
results of the REA Survey were presented in table form to allow an easy
comparison between the different sites investigated. The details of all the marine ecological
surveys conducted for this EIA are summarized in Table 5.4 in the next section.
5.4 Baseline Conditions & Marine Ecological Sensitive Receivers
The relevant marine ecological information collected from literature reviews and field survey studies is summarized in this section in order to provide baseline information on the inter-tidal communities, sub-tidal coral communities, soft-bottom marine benthic communities and marine mammals, in accordance with Condition 3.4.7.4 (v) set in EIA Study Brief No. ESB-198/2008. This assessment also presents the marine resources found within the four relevant WCZs (i.e. Victoria Harbour, Western Buffer, North Western and Southern WCZs), as well as summarises the physical environment and ecological resources within the Study Area, whilst details of the field survey records are presented in Appendices 5.1-5.3. Habitat maps of suitable scale showing the types and locations of the inter-tidal habitat, locations of coral, marine benthic communities and inter-tidal habitats, and distribution of marine mammals in the Study Area are presented in Figures 5.4-5.7 in accordance with Condition 3.4.7.4 (iv)(b) set in EIA Study Brief No.ESB-198/2008.
5.4.1
Water
Quality
The
proposed dredging area is situated at
the
5.4.2
Sediment
Quality
Findings of the Consultancy Study on Marine
Benthic Communities in Hong Kong (CPSL 2002) regarding sediment characteristics in the Project area
indicate that the existing seabed near the proposed
dredging areas at the KTCB comprise very poorly sorted
coarse sand. The total organic matter (TOM) content in the seabed sediment was
relatively low (3.18% in summer and 4.00% in winter, compared to an average of
6.04% in
The
seabed sediment of Victoria Harbour was described as grey, clayey, very silty
and very gravelly sand with shell fragments in the 2002 sediment testing (Mouchel 2002), which was similar to the sediment testing
results conducted for the Laying of Western Cross Harbour Main and
Associated Land Mains from West Kowloon to Sai Ying Pun in September 2006 (Mott Connell 2007). Sediments
collected close to the central and southern fairway indicated that the surface
deposit at around 1m depth from the seabed was anthropogenic, black sediment which was oxidized to
brown, slightly silty, fine to coarse sand with little sub-angular, fine to
medium gravel of rocks (Mott Connell
2007). According to the study conducted by CityU, there
were minimal seasonal changes in sediment characteristics for both summer and
winter around
5.4.3
Inter-tidal
Communities
5.4.3.1
Artificial seawalls are the dominant coastal
habitat along
Findings
from literature review indicated that
the species diversity at the inter-tidal zone of Green
Surveys of the inter-tidal communities of Green Island, Little Green Island and a reference site in Hong Kong Island conducted by Mouchel in 1998 have been reviewed by ERM (ERM 1998) (Figure 5.3). A total of 22 species of fauna was recorded. The most abundant species recorded in the inter-tidal zone around the above Study Area were grazing gastropods such as Chiton (Acanthopleura japonica) and Limpets (Cellana grata, C. toreuma, Patelloida pygmaea and P. saccharina) recorded at the lower eulittoral zone, and Periwinkles (Echinolittorina trochoides, E. radiata and E. vidua) recorded at the higher eulittoral zone. Predatory gastropods such as Dogwhelks (Thais clavigera and T. luteostoma) were also recorded in low density at the lower eulittoral zone. Sessile organisms including Stalked Barnacles and Acorn Barnacles were recorded in high abundance (ERM 1998). By comparing the three survey locations, the overall species abundance and species diversity were highest at the reference Hong Kong sites, followed by the Little Green Island and Green Island. The findings displayed the inter-tidal community to be of typical semi-exposed rocky shores. No rare species or species of conservation importance were recorded for these areas in this study.
During
the inter-tidal community
survey conducted for the Project,
18 species of invertebrates were found in the inter-tidal zone of
5.4.3.2
Western
Buffer WCZ
The
inter-tidal zone close to the proposed dredging area consists of vertical seawalls, boulder-mounted sloping seawalls and
concrete dolosse at the Tsing Yi and Kwai Chung shorelines. Inter-tidal community surveys were conducted
along the coastline close to the proposed dredging area at the
The inter-tidal communities on both northern
and southern entrance of the KTCB are of similar assemblages. From the
high to low tidal level, the eulittoral
zone is dominated by Acorn
Barnacle Tetraclita squamosa and Rock
Oyster Saccostrea cucullata whilst varied types of limpets are common.
Chiton Acanthopleura japonica was
recorded but is in low abundance compared to similar habitat type with longer
history. The results of the inter-tidal survey are listed in Tables 1a and
1b in Appendix
5.2. All of the species recorded are common and of similar type to those
found on the wharves and embankments in the
Natural
rocky shores and sandy shores were identified at
5.4.3.3
The inter-tidal zone of Kau Yi Chau near the proposed dredging area consists of rocky shores and sandy shores (Figure 5.5b). Similar habitats were recorded in the inter-tidal zone of Siu Kau Yi Chau. Inter-tidal community surveys were conducted at the coastline close to the proposed dredging area at Kau Yi Chau as indicated in Figure 5.2. The coastline is mainly composed of rocks and boulders of assorted sizes interspersed with sandy shore.
During the field survey for this Project, a
total of 17 species of invertebrates was recorded in the inter-tidal zone of Kau Yi Chau (Tables 1a, 1b, 2b and 3b
of Appendix
5.2). Periwinkles Echinolittorina trochoides and Echinolittorina
vidua were found frequently in the upper
eulittoral zone and littoral fringe while at the lower eulittoral zone, the
coastal community is dominated by Acorn Barnacle Tetraclita squamosa,
Chiton Acanthopleura
japonica, Dog Whelk Thais clavigera, False Limpet Siphonaria japonica and Limpet Cellana grata. All species found are common or very
common on natural rocky shore including a few Green Mussel Perna viridis
which usually appear in large colonies attached to hard substrate, in
particular wharf piles in Victoria Harbour.
Inter-tidal
surveys were conducted in Tai Lei, Peng Chau in 2002 to 2003 by BMT (Figure 5.3).
The coastline is made up of granite bedrock outcrop with crevices and pools, with
small boulders embedded in sand at the lower shore (BMT 2005). Surveys in both
years recorded only common species in the area. On the rocky / boulder
shore, common inter-tidal species such as Limpet Patelloida saccharina, Anemone Haliplanella luciae, Neritid Shell Nerita albicilla and hermit crab were abundant. Periwinkle Nodolittorina
trochoides,
Barnacle Capitulum mitella and Limpet Patelloida saccharina were
recorded at the upper shore while Barnacle Terraclita squamosaI, Limpets
Cellana toreuma, Patelloida
saccharina, top shell Monodonta labio, Whelk Thais clavigera and Chiton Acanathopleura japonica were
recorded in the mid-shore. Green anemone Haliplanella luciae, Barnacle Terraclita squamosaI, hermit crabs, Monodonta labio, Patelloida
saccharina, Cellana toreuma and Capitulum mitella were found abundant
in the lower shore zone. All species are common and typical of hard shore
environments (BMT 2005).
5.4.3.4
North
The North Western
WCZ is a very large WCZ covering highly diversified inter-tidal habitats. Along
the northern coastline from
Sham Tseng to Lung Kwu Tang, it is dominated by artificial shoreline.
5.4.4 Marine Soft-bottom Benthic Communities
The soft-bottom benthic communities in
In
order to update and verify the ecological value of the benthic communities within
the potentially affected area, site-specific marine soft-bottom benthic survey
was conducted in January 2010. Grab sampling was conducted at 9 selected
locations (locations refer to Figure 5.2), within and adjacent to
the dredging area. The findings of the marine soft-bottom benthic grab sampling
are detailed in Appendix
5.3. In
summary, the results indicated that the sediments at the 9 sampling stations
are mostly greyish, muddy and sandy with shell fragments. Stations D and E at
the Western Fairway (within the Project area) and Ma Wan Fairway (outside the
Project area) respectively have a higher sandy sediment content, and recorded a
relatively higher abundance of benthic fauna (dominated by polychates) amongst
the 9 stations (extracted data is presented in Table 5.5). Station G recorded the fewest benthos and number
of species. This could be due to the suspected hypoxic conditions at this
station.
Compared
to the survey findings conducted by the CPSL (2002), the current Study recorded
a relatively higher species diversity and abundance. The soft-bottom benthos
species recorded in this Study are dominated by annelids and crustaceans. No
species of conservation concern were recorded which accords with the previous
results presented by CPSL. Dominant species recorded within the Project area (Stations
B, D, F, H and I) include Annelids (Cirratulidae, Nepthyidae, Paraonidae, Paraprionospio pinnata, Spionidae,
Syllidae, Terebellidae), and Crustaceans (Callianassa
japonica, Clausidiidae), with annelids contributing the highest biomass
content (Table B3 of Appendix
5.3).
Oligochaetes (Thalassodrilides
gurwitschyi) recorded in Stations H and I indicate that a relatively
eutrophic environment exists within the
Table 5.4: Findings of Soft-bottom Marine Benthic Sampling at Selected Stations – Summer & Winter (CPSL 2002)
Station |
Season |
Species
richness |
Species
diversity |
Evenness |
Taxonomic
diversity |
Taxonomic
distinctness |
W statistic |
41 |
Summer |
6.02 |
2.78 |
0.80 |
63.49 |
71.12 |
0.145 |
42 |
7.32 |
3.16 |
0.90 |
71.1 |
74.34 |
0.462 |
|
43 |
4.82 |
2.58 |
0.88 |
76.67 |
79.5 |
0.046 |
|
45 |
5.45 |
2.51 |
0.79 |
63.64 |
75.39 |
0.226 |
|
46 |
5.21 |
2.65 |
0.85 |
65.27 |
72.28 |
0.213 |
|
48 |
4.16 |
2.19 |
0.77 |
58.11 |
70.98 |
0.099 |
|
49 |
5.16 |
2.66 |
0.85 |
61.60 |
67.26 |
-0.018 |
|
50 |
3.28 |
1.82 |
0.66 |
46.98 |
62.84 |
-0.232 |
|
51 |
3.60 |
1.39 |
0.44 |
33.25 |
56.00 |
-0.100 |
|
52 |
2.04 |
1.14 |
0.52 |
34.14 |
71.36 |
0.089 |
|
53 |
6.46 |
2.35 |
0.60 |
66.11 |
77.10 |
-0.009 |
|
41 |
Winter |
4.83 |
2.56 |
0.85 |
69.61 |
77.04 |
0.175 |
42 |
7.49 |
3.14 |
0.91 |
78.13 |
81.53 |
0.285 |
|
43 |
5.53 |
2.47 |
0.78 |
67.48 |
78.81 |
0.335 |
|
45 |
4.67 |
2.57 |
0.89 |
77.45 |
84.03 |
0.526 |
|
46 |
6.65 |
3.14 |
0.97 |
75.75 |
77.73 |
0.305 |
|
48 |
3.22 |
2.14 |
0.97 |
81.06 |
84.92 |
0.141 |
|
49 |
6.42 |
2.92 |
0.88 |
71.11 |
76.17 |
0.483 |
|
50 |
4.91 |
2.62 |
0.91 |
65.19 |
69.83 |
0.074 |
|
51 |
9.08 |
2.82 |
0.68 |
59.43 |
65.89 |
-0.014 |
|
52 |
3.55 |
1.78 |
0.67 |
56.88 |
83.3 |
0.061 |
|
53 |
5.84 |
2.36 |
0.63 |
63.16 |
76.81 |
0.039 |
Table 5.5: Summary of Soft-bottom Marine Benthic Survey Findings for this Study (January 2010)
Station |
No. of Animals |
No. of species |
Mass (g) |
Species
Diversity (H’) |
Evenness
(J) |
A |
107 |
72 |
0.954 |
4.16 |
0.97 |
B |
105 |
64 |
0.352 |
3.97 |
0.96 |
C |
94 |
53 |
0.963 |
3.77 |
0.96 |
D |
141 |
59 |
1.640 |
3.78 |
0.93 |
E |
158 |
62 |
0.842 |
3.98 |
0.96 |
F |
110 |
70 |
0.768 |
4.16 |
0.98 |
G |
69 |
50 |
0.785 |
3.82 |
0.98 |
H |
85 |
51 |
1.379 |
4.03 |
0.98 |
I |
91 |
60 |
0.902 |
3.95 |
0.97 |
5.4.5 Sub-tidal Coral Communities
The coral communities of
Most of the shallow
marine areas in
5.4.5.1
Marine dive surveys were carried out at the
sub-tidal zone around
The sub-tidal habitat is established with
sessile benthos, including 7 species of hard hermatypic coral recorded in this
area. Colony sizes vary considerably and range from small (<10cm2)
to large (>0.5m2). All
corals are patchy with some dense areas recorded. Four species of gorgonians,
one species of soft coral and one species of ahermatypic coral were recorded.
On the eastern side of Kau Yi Chau, the
seabed is dominated by sand and rubble in shallow areas with mud, silt or sand
in deeper areas. Rocks and boulders of assorted sizes are scattered throughout
the area. In addition, Debris was found to be scattered around the area
including some metal pieces which could be the remains of a shipwreck.
The area is established with sessile
benthos. Seventeen species of hard coral were recorded along the transect.
Colony sizes vary considerably and range from small (<10cm2) to
large (>0.5m2). The coral colonies were recorded to be in good
condition. Three species of gorgonians, one species of soft coral and one
species of ahermatypic coral were recorded.
5.4.5.2
The coastline on
The western coast of
In Luk Chau Wan a higher coral coverage was
recorded compared to other sites on
5.4.5.3
Southern
WCZ (Peng Chau,
The sub-tidal habitat at Peng Chau was
recorded with moderate diversity of coral communities including hard, soft and
black corals (CDM 2004). Hard (Scleractinian) coral, of common species, was
recorded in small isolated patches. Damage on the live coral was observed. A
soft coral community dominated by one genus Echinomuricea
was located at silty environment. As a result, that area did not form part of a
significant coral community.
In the
5.4.5.4
Tsing
Yi and
Marine dive surveys were conducted along the
coastline of Tsing Yi and KTCB for this project at 9 spot dive locations. The
coastal habitat consists of varied types of modified seawall including quarry
rock barrier and concrete vertical seawall. To the north of the
Within the container port, two colonies of
the gorgonian Guaiagorgia sp. and four colonies of the soft coral Dendronephthya sp. were recorded on one
pillar. The seawall dolosse at the southern entrance of the container port was
surveyed but no coral was found. The full report on the marine dive survey
together with the spot dive and REA dive raw data is presented in Appendix
5.1.
5.4.5.5
North
Hard (Scleractinian) coral community in this
WCZ is generally low in species diversity and in abundance owing to the
influence of freshwater discharges from the
5.4.6
Marine
Waters
The Assessment Area covers four WCZs
stretching from North Western to Victoria Harbour Water Control Zones. The
inshore hydrography is affected by fresh water arriving from two sources,
namely, heavy rainfalls and the
The
5.4.6.1 Marine Mammals
All
the marine mammals in
Chinese White Dolphin (CWD) is listed as
“Near Threatened” in IUCN Red Data List (IUCN 2009) on account of its
decreasing trend in population. They have limited distribution in
Finless Porpoise is listed as “Vulnerable”
in IUCN Red Data List (IUCN 2009) on account of its decreasing trend in
population. This species is rather cryptic and is therefore difficult to
survey. In Hong Kong, it generally occurs in southern waters, from
5.4.7 Habitats identified as Recognized Sites of Conservation Importance
A few locations in the Study Area have been identified as recognized sites of
conservation importance, including
the Cape D’Aguilar Marine Reserve, Sha
Chau and
With reference to the baseline
conditions discussed above, the ecological
importance of the marine habitats were evaluated and determined on the basis
of the criteria set in the EIAO-TM Annex
8 Table 2.
The marine habitat was evaluated based on
the marine ecological resources found in the inter-tidal communities, coral communities
on hard substrate, soft-bottom marine benthic communities and the marine
mammals in the marine waters. The marine habitat evaluation covers the water
control zones which are likely to be affected by the dredging activities,
including Victoria Harbour WCZ, Western Buffer WCZ, North Western WCZ and
5.5.1
Evaluation
on Habitat
The coastline of Victoria Harbour WCZ is
largely modified with varied types of artificial seawall. The inter-tidal
communities and sub-tidal communities found in this highly disturbed habitat
are mostly fouling species with low ecological value. One exception is at
The dredging areas in the
Since the ecological resource in the southern
part of the
The evaluations of inter-tidal, sub-tidal
and marine benthic habitats and marine waters are presented in Tables 5.6-5.9 respectively.
Table
5.6: Evaluation
of the Ecological Importance of the Inter-tidal Habitats
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
(Northern
Portion) |
Naturalness |
Mainly
artificial seawall along the |
Vertical artificial seawall and sloping boulder-mounted seawall at Tsing Yi and Container Basin receiving extensive disturbances including pollution load and heavy marine traffic. |
Coastline in Sha Chau and |
Rocky shore and sandy shore at Kau Yi Chau and Siu Kau Yi Chau is comparatively natural. Coastline in other outlying islands is moderately modified. |
Size |
The
natural inter-tidal shoreline at |
The
rocky shore at |
Large area of inter-tidal habitat. |
The natural inter-tidal shoreline at Kau Yi Chau, Siu Kau Yi Chau and Peng Chau is approximately 6.5km. |
Diversity |
The species diversity is low. |
The species diversity is low. |
High species diversity owing to the
presence of mangrove and seagrass bed. |
The species diversity is low. |
Rarity |
The
species recorded at |
The
species recorded at Tsing Yi and |
Four species of seagrass and two species
of horseshoe crab are rare in |
The
species recorded at the natural shorelines
in Kau Yi Chau, Siu Kau Yi Chau and other outlying islands are typical
of other rocky shores and sandy shores in |
Re-creatability |
The natural rocky shores are difficult to recreate. |
The artificial seawall is recreatable but the natural rocky shores are difficult to recreate. |
Natural shore is difficult to recreate. |
The
natural rocky shores and sandy shores are
difficult to recreate. |
Fragmentation |
Not applicable. |
Not applicable. |
Not applicable |
Not applicable. |
Ecological Linkage |
Not functionally linked to high ecological
value habitat. |
The existing habitats at artificial seawall are not functionally linked to high ecological value habitats. |
The inter-tidal community at the mudflat
sites are ecologically linked. |
The costal community at the northern part of this WCZ is not functionally linked to high ecological value habitat. |
Potential Value |
The
rocky shores have low potential to develop nature conservation
interest habitat. |
The
artificial seawall habitats at Tsing Yi and |
Sha Chau and Lung Kwu Chau are designated |
The rocky and sandy shores at Kau Yi Chau have low potential to develop into a nature conservation interest habitat. |
Nursery/Breeding Ground |
Not identified. |
Not identified. |
Mudflat at north Lantau is identified as
breeding ground for horseshoe crab. |
Not identified. |
Age |
Not applicable. |
Not applicable. |
Not applicable. |
Not applicable. |
Abundance/ Richness of Wildlife |
Low species richness found in the artificial seawall. |
The
species abundance was low at vertical smooth structures, wharf piles and
boulder-mounted seawall at Tsing Yi and |
High species richness in north and west
Lantau. |
Moderate species abundance in rocky shore. |
Summary |
The
inter-tidal assemblages along the natural rocky shores at |
The
inter-tidal assemblages along shoreline of |
The inter-tidal mudflat at north and west
Lantau and the coastline at Sha Chau and |
The inter-tidal assemblages along the natural rocky shores in the northern part of this water zone are of moderate-low ecological value. |
Table 5.7: Evaluation
of the Ecological Importance of the Hard-bottom Sub-tidal Habitats
Criteria |
Peng
Chau, |
Pak
Kok, Shek Kok Tsui, Ap Lei Chau |
|
Tsing
Yi and |
North
Western WCZ |
Naturalness |
The
sub-tidal zone is composed of natural rocky seabed with scattered boulders. |
Natural rocky shore at northern Lamma but artificially modified seashore at Ap Lei Chau. |
The |
Varied type of concrete seawall
receiving extensive disturbances
including pollution load and marine traffic.
The seashore is highly modified for marine traffic use. |
Largely natural. |
Size |
The sub-tidal habitat within Study Area is large. |
The
sub-tidal habitat within the Study Area is large in size. |
The rocky shoreline is moderate in size. |
The artificial seawall habitat is moderate
in size. |
Sub-tidal habitat in this WCZ is large |
Diversity |
The
species diversity of coral communities recorded in various locations is
moderate-low. |
The
species diversity of coral communities is moderate-low. |
Moderate-low diversity of hard corals. |
No hard coral communities. The
species diversity of soft coral communities is low. |
Low diversity of coral community. |
Rarity |
The
coral species recorded are not rare |
The
hard coral species recorded are not rare |
The
hard (hermatypic scleractinian) coral species recorded are not rare to
|
The
gorgonian coral Guaiagorgia
sp. is a localized species in |
No rare species recorded. |
Re-creatability |
The
natural rocky habitat is difficult to recreate |
The
rocky habitat is difficult to recreate |
The natural habitat is difficult to recreate. |
The highly modified sub-tidal habitat is recreatable. |
Sub-tidal hard substrate for coral colonization is recreatable. |
Fragmentation |
Not
applicable |
Not
applicable |
Not applicable. |
Not applicable. |
Not applicable. |
Ecological Linkage |
The
sub-tidal habitats are not functionally linked to high ecological value
habitats. |
The sub-tidal communities are not functionally linked to high ecological value habitats. |
The existing habitats are not functionally linked to high ecological value habitats. |
The existing habitats are not functionally linked to high ecological value habitats. |
The sub-tidal communities are functionally
linked to Sha Chau and |
Potential Value |
Low
potential to develop to high ecological value area. |
Low
potential to develop to high ecological value area. |
Low potential to develop to high
ecological value area. |
Low potential to develop to high ecological value area. |
Low potential to develop to high ecological value area. |
Nursery/ Breeding Ground |
Not
identified |
Not
identified |
Not identified. |
Not identified. |
Not identified. |
Age |
Not
applicable |
Not
applicable |
Not applicable. |
Not applicable. |
Not applicable |
Abundance/ Richness of Wildlife |
Hard
coral richness at the area is generally moderate-low. |
The
abundance of coral species is moderate-low. |
Moderate-low richness of coral species. |
No hard coral species. Low richness of
gorgonian coral and soft coral. |
Low abundance and species richness of
coral species. |
Summary |
The coral communities found in these areas are generally in low cover, moderate diversity and not rare. The sub-tidal communities are of moderate-low ecological value. |
The
sub-tidal coral communities are of moderate-low ecological value. |
The coral
communities at the natural sub-tidal
rocky shore in |
The sub-tidal assemblages in the container port and the adjoining artificial habitat are of low ecological value since only low richness of gorgonian and soft corals are present. |
The sub-tidal coral community in this water zone is low in ecological value given the low species richness and abundance. |
Table 5.8: Evaluation
of the Ecological Importance of the Soft-bottom Marine Benthic Habitats
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
|
Naturalness |
Silt-clay
bottom was highly disturbed. |
Silt-clay
bottom has been disturbed by marine traffic. |
Silt-clay
bottom have been subject to disturbance from |
Relatively
natural, but was disturbed by fishery activities. |
Size |
Large |
Large |
Large |
Large |
Diversity |
Similar
diversity to the majority of other areas in |
Similar
diversity to the majority of other areas in |
Similar
diversity to the majority of other areas in |
Varied
from low to high. Highest in southern |
Rarity |
No
rare benthic or conservation concerned organism was found. |
No rare benthic or conservation concerned organism was found. |
No
rare benthic or conservation concerned organism was found. |
One
conservation concerned species Branchiostoma
blecheri was recorded in |
Re-creatability |
Can
be recreated readily through sediment deposition. |
Can be recreated readily through sediment deposition. |
Can
be recreated readily through sediment deposition. |
Can be recreated through sediment deposition and removal of disturbance. |
Fragmentation |
Not
fragmented |
Not
fragmented |
Not
fragmented |
Not
fragmented |
Ecological Linkage |
No
significant linkage to high ecological value area. |
No significant linkage to high ecological value area. |
Ecologically
link to Sha Chau and |
Linked
to other sub-tidal habitat in high ecological value area e.g. |
Potential Value |
Low
potential to develop high conservation value site. |
Low
potential to develop high conservation value site. |
Low
potential to develop high conservation value site. |
Low
potential to develop high conservation value site. |
Nursery/Breeding Ground |
No
significant record |
No
significant record |
No
significant record |
No
significant record |
Age |
Unknown |
Unknown |
Unknown |
Unknown |
Abundance/ Richness of Wildlife |
Abundance
and species richness are comparable to the majority of other areas in |
Abundance
and species richness are comparable to the majority of other areas in |
Abundance
and species richness are comparable to the majority of other areas in |
Species
richness varied from low to high. Generally lower at northern part. |
Summary |
Low
ecological value due to highly disturbed habitat and low diversity and
abundance of benthic organism. |
Low
ecological value due to highly disturbed habitat. |
Low ecological value owing to low abundance
of common and widespread species. |
Moderate-low
ecological value owing to the relative natural benthic habitat and benthic
organism of varied richness and diversity. |
Table 5.9: Evaluation of the Ecological Importance of
the Marine Waters
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
|
Naturalness |
Disturbed
by busy shipping lanes and pollution. |
Disturbed
by busy shipping lanes and fishery operation. |
Disturbed
by busy shipping lanes and fishery operation. |
Disturbed
by busy shipping lanes and fishery operation. |
Size |
Large |
Large,
covers the Ma Wan Channel, Kap Shui Mun Channel and other major netvigation
channel and anchorages in the |
Large |
Large,
400km2 to the south of |
Diversity |
No
recent dolphin record. |
Low
densities of CWD were recorded. |
High
abundance of CWD were recorded. |
Low
density for CWD, whilst the density for Finless Porpoise is low but of
relative importance in |
Rarity |
No
rare species recorded. |
CWD
is a species of conservation concern and protected under |
CWD
is a species of conservation concern and protected under |
CWD
and Finless Porpoises are species of conservation concern and are protected
under |
Re-creatability |
This
habitat cannot be easily recreated. |
This
habitat cannot be easily recreated. |
This
habitat cannot be easily recreated. |
This
habitat cannot be easily recreated. |
Fragmentation |
Marine
waters are not fragmented. |
Marine
waters are not fragmented. |
Marine
waters are not fragmented. |
Marine
waters are not fragmented. |
Ecological Linkage |
No
ecological linkage to habitat of conservation importance. |
No
ecological linage habitat of conservation importance. |
Linkage
to the Sha Chau and |
Linkage
to coastal waters in southern Lantau, southern Lamma and southern |
Potential Value |
Low |
Low |
High
in respect of relative high abundance of CWD. |
Moderate
in respect of the presence of Finless Porpoise. |
Nursery/Breeding Ground |
Not
significant |
Not
significant |
Coastal
water along Sha Chau and |
Nursery
activity for CWD in this water zone was mainly recorded near Fan Lau. No
noticeable nursery and breeding activity for Finless Porpoise. |
Age |
Not
applicable |
Not
applicable |
Not applicable |
Not
applicable |
Abundance/ Richness of Wildlife |
Low
abundance |
Low
abundance of marine mammals. |
High
abundance of CWD. |
Moderate
abundance of marine mammals. |
Summary |
Low
ecological value |
Low
ecological value |
High-moderate
ecological value owing to the high density of CWD in this water zone. |
High-moderate
ecological value owing to the presence of Finless Porpoise. |
5.5.2
Evaluation
on Species of Conservation Importance
The
Chinese White Dolphin is the most regularly seen cetacean in
Hard
corals (Scleractinian) are protected under the Protection of Endangered Species
of Animals and Plants Ordinance (Cap. 586). All corals in Marine Parks are
protected under the Marine Park Ordinance (Cap. 476). All form of destructive
fishing practices that could also affect the corals area are prohibited under
the Fisheries Protection Ordinance (Cap. 171). The ecological importance of
marine mammals and hard coral are summarized in Table 5.10.
Table
5.10: Evaluation
on Species of Conservation Importance
Species |
Protection
Status |
Distribution |
Rarity |
Chinese
White Dolphin |
Protected
under |
Mainly
in estuarine habitat in Pearl River Delta - northwest and west Lantau waters |
Roughly
200 individuals using |
Finless
Porpoise |
Protected
under |
Mainly
distributed in waters off southern and eastern |
Estimated
at over 200 individuals in |
Hard
Corals |
Hard
coral (order Scleractinian) are protected under Hong Kong Ordinance (Cap.
586). All corals in Marine Parks are protected under Marine Park Ordinance
(Cap. 476) |
Scattered
hard coral colonies are found at the hard sub-tidal substrate along the
coastline within the Study Area. |
The
hard coral species found in the Study Area (Western Buffer WCZ and Southern
Buffer WCZ) are mostly common and tolerable to pollution. |
5.6 Prediction and Evaluation of Environmental Impacts
The proposed dredging area is
approximately 446ha and the depth of the seabed will reach a level of approximately
-17.5mC.D after dredging. The major impact on marine
ecological resources within the Assessment Area is the
direct impact of habitat loss of the seabed and
the indirect impact due to increased SS levels and changes in receiving water
quality. The water quality impacts arising from the proposed dredging
activities include perturbation of the seabed, elevation of SS and changes in
sediment transport regimes. The impact
of changes of water quality during the dredging works was simulated by water
quality modelling. Potential impacts associated with increased marine traffic
include possible collisions with marine mammals and indirect acoustic
disturbance effects.
According
to the predicted result of sediment plume dispersion as indicated in the
contours in the worst case scenario presented in Appendices A3.1 and
A3.2, the predicted SS level in North Western
WCZ are compliant with WQO requirement such that the potential impact to North Western WCZ is considered as
negligible. Therefore the impact prediction and evaluation presented in this
section would mainly focus on Western Buffer,
5.6.1.1
Impacts
on Inter-tidal Communities
The natural inter-tidal habitats at
The inter-tidal communities along Tsing
Yi and the KTCB are mostly low density and coverage due to the
newly installed artificial seawall. The species recorded are mostly
bio-fouling organism and thus the ecological value of the habitat is considered
as low. The exceedances of ambient SS levels at the Rambler Channel
and waters near Tsuen Wan as stated in Section
3.7.1.1 would pose only minor impact on
the inter-tidal communities. Evaluation of the impact on inter-tidal
habitat is summarized in Table 5.11.
Table 5.11: Impact Evaluation of Inter-tidal Habitats
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
|
Habitat Quality |
The
coastlines along the |
The
coastlines along Tsing Yi and Natural rocky shore of |
The
coastline in north and west Lantau and Sha Chau and |
The
natural rocky shore and sandy shore are identified at Kau Yi Chau and Siu Kau
Yi Chau, which are located near the proposed dredging area. Coastlines along
other outlying islands within the WCZ are mainly hard shores and artificially
modified seawall. |
Species |
Species recorded at |
Species recorded at Tsing Yi and |
Seagrass
bed and horseshoe crab breeding ground were identified in north Lantau. |
Species
recorded at the natural shorelines are typical of other semi-exposed
rocky shores and sandy shores in |
Size/ Abundance |
Low
species diversity, small area of natural shoreline at |
Low abundant of species recorded, small
area of natural shoreline at |
High
species diversity for the inter-tidal mudflat communities. |
Moderate-low
diversity of species recorded, moderate area of natural shoreline at Kau Yi
Chau, Siu Kau Yi Chau and Peng Chau |
Duration |
Construction
phase |
Construction
phase |
Construction
phase |
Construction
phase |
Reversibility |
Reversible
after the disturbance source removed. |
Reversible
after the disturbance source removed. |
Reversible
after the disturbance source removed. |
Reversible
after the disturbance source removed. |
Magnitude |
Low
magnitude – potential water quality effect |
Low
magnitude – potential water quality effect |
Negligible
owing to the far distance. |
Low
magnitude – potential water quality effect |
Summary |
The impacts to the natural rocky shore at |
The impacts to the natural rocky shore at |
The
impact to the inter-tidal communities in this WCZ is negligible. |
The impacts to the natural rocky seashore are predicted to be minor. |
5.6.1.2
Impacts
on Hard-bottom Sub-tidal Coral Communities
The
hard coral communities in
Disturbance
to hard coral communities associated with dredging activities are usually
induced by the elevation of SS in the water column. Deposition of sediment
would cause the hard coral to suffocate and die or indirectly affect the
potential of photosynthesis through blocking of sunlight reaching the sub-tidal
habitat. The coral communities closest to the dredging zone are the most
susceptible to the disturbance.
According
to the survey results, the KTCB and Western Fairway were not recorded with hard
coral species. Only the relatively natural hard substrate at
Similar
to
To
the east of the dredging area, the sub-tidal habitats in Victoria Harbour WCZ
are highly disturbed by marine traffic and pollutants. Although hard coral
species were recorded in sporadic locations, the species are mostly common and
tolerant to disturbance. Therefore, the potential impact to the hard coral
communities in this WCZ is insignificant given the low ecological value of the
hard coral communities. Further in the southern part of the Western Buffer WCZ,
coral communities were recorded along
The prediction of alternation of water quality induced by the dredging works was determined through the assessment of water quality modelling results. The modelling scenarios included representative coral sites as specific sensitive receivers (Figure 3.1). The daily sedimentation rate, which is influential to coral growth, was also included as a parameter in the analysis in order to determine the potential impact on the health of the coral sites. It is acknowledged that benthic organisms, including corals, may suffer damage to their respiratory function as a result of sediment deposition blocking the respiratory and feeding organs of those organisms. According to Hawker and Connell (1992), a sedimentation rate higher than 0.1 kg m-2 per day would introduce moderate to severe impact upon corals. This criterion was adopted as the assessment criterion for protecting the marine ecological sensitive receivers in this Study. While there are no established legislative criteria for water quality for corals, an elevation criterion of SS levels less than 30% of ambient baseline conditions (Hawker and Connell, 1992) has been adopted as the critical value above which impacts to the habitat may occur. This criterion is based on a previously approved EIA for assessing SS impacts on corals (Maunsell, 2001).
The
impact of SS elevation on the coral communities was simulated under Scenarios 1
to 6 as described in Section 3.5.2.3 for a typical spring neap tidal cycle
during dry and wet seasons in
Since
the sedimentation rate in the coral sites are relatively low, the potential for
large scale siltation on corals that cause suffocation is anticipated to be
very low. The impact on growth, recruitment and resilience of the coral
community is also considered to be minor. Although
Table 5.12: Impact Evaluation of Hard-bottom Sub-tidal Habitats
Criteria |
Peng
Chau, |
Pak
Kok, Shek Kok Tsui, Ap Lei Chau |
|
Tsing
Yi and |
Habitat Quality |
Natural
habitat but also subjected to moderate level of artificial modification. |
Natural habitat but also subjected to moderate level of artificial modification. |
Mostly
natural in |
Artificial modified |
Species |
Hard coral communities are in moderate diversity but low coverage. Species assemblage dominated by Faviidae family. |
Hard coral communities are in moderate diversity but low coverage. Species assemblage dominated by Faviidae family. |
The species recorded in the dredging area
are common and pollution tolerant. 17 species of hermatypic Scleractinian
corals were recorded in Kau Yi Chau whilst 7 species were recorded in |
No hard coral were found. |
Size/ Abundance |
Large
area but low abundance of coral communities. |
Large
area but low abundance of coral communities. |
Moderate
area and moderate-low abundance on coral communities. |
Moderate
area but no coral communities. |
Duration |
Construction
phase |
Construction
phase |
Construction
phase |
Construction
phase |
Reversibility |
Reversible |
Reversible |
Reversible |
Reversible |
Magnitude |
Low
magnitude |
Low
magnitude |
Low
magnitude |
Low
magnitude |
Summary |
The potential impact to the moderate-low
ecological valued sub-tidal habitat is
predicted to be negligible. |
The potential impact to the moderate-low ecological valued sub-tidal habitat is predicted to be negligible. |
The impacts to the
moderate-low ecological valued sub-tidal habitat are predicted to
be minor. |
Minor impact due to low
abundance of marine ecological resources. |
5.6.1.3
Impacts
on Soft-bottom Marine Benthic Communities
Direct impact on habitat loss
Temporary
habitat loss of marine benthic sediment will
occur at the dredging area in KTCB,
Northern Fairway and Western Fairway. It will lead to direct
removal of marine organism inhabiting the benthic sediment. The seabed
substrates are composed of silt, clay, fill and alluvium that receive
continuous disturbances from the heavy
marine traffic. Species recorded in this region
were common and dominated by pollution tolerant
marine benthos including polychaetes Sigambra
hanaokai and oligochaetes Thalassodrilides
gurwitschyi, recorded
both within and in the vicinity to the Project area. Benthic
fauna is expected to recolonize the seabed after the dredging
works with similar seabed substrates before dredging.
After recolonization and settlement of marine organism on the benthic sediment,
the habitat will be recovered and the loss of habitat is regarded as temporary
only. In considering the high commonness and low quality of
marine benthic organisms recorded, the low
ecological value of the highly disturbed seabed and the recovery of
seabed for recolonization of benthic fauna after construction, the
direct impact on the temporary loss of
approximately 446ha of seabed habitat
along the Container Basin, Northern Fairway and
Western Fairway are considered to be minor.
Indirect disturbance associated with
suspended solids
The
dredging activities will cause sediment transport, and high sediment deposition
on the benthic environment could cause smothering and burial of marine
organisms. Less mobile species such as bivalves are more susceptible to these
potential impacts. The evaluation of the potential impact has taken into
account the ecological value of the potentially affected marine organism and
the dispersion of sediment plume. The influence of SS concentration is
predicted by using the water quality modelling which simulated the dispersion
of sediment generated as a result of various dredging scenarios.
The
water quality modelling results indicated that high concentration of SS will be
confined to the area in close proximity to the dredging area, and to a lesser
extent to the adjacent area. The contours presented in Appendices A3.1 and 3.2 show the extent of maximum surface,
bottom and depth-averaged SS elevations over the complete simulation period
during dry and wet seasons, respectively. As shown in these figures, the extent
of SS impact appears to be confined near the dredging
areas at Rambler Channel, Northern Fairway and Western Fairway. Temporal
variations at snapshots in the tidal cycle of
surface, mid-depth, bottom and depth-averaged SS elevations at various WSRs in
close proximity to the dredging areas during dry and wet seasons are
also shown in Appendices A3.1 and
A3.2.The
benthic communities in the areas with high predicted SS level currently
experience high levels of disturbance. Since the ecological values of the
benthic organisms inhabiting these potentially affected areas are relatively
low, the potential impact is predicted to be minor.
With
regard to the benthic communities at the Southern WCZ, the predicted sediment
deposition will potentially affect the northern part of the
Table 5.13: Impact Evaluation of Soft-bottom Marine Benthic Habitats
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
|
Habitat Quality |
Highly
disturbed benthic communities. |
Highly disturbed benthic communities. |
Highly
disturbed benthic communities. |
Northern part is highly disturbed. Southern part is relatively less disturbed. |
Species |
Species
are common in similar habitat. |
Species
are common in similar habitat. |
Species
are common in similar habitat. |
Species
are common in similar habitat. One species of conservation concern was found
in |
Size/ Abundance |
Large |
Large |
Large |
Large |
Duration |
Construction
phase |
Construction phase |
Construction
phase |
Construction phase |
Reversibility |
Reversible |
Reversible.
Benthic organisms readily re-colonize the benthic habitat. |
Reversible |
Reversible |
Magnitude |
The impact to the benthic habitat is of low magnitude. |
The impact to the
benthic habitat is of low magnitude. |
The
impact to the benthic habitat is negligible. |
The impact to the benthic habitat is of low magnitude. |
Summary |
The impacts to the low ecological valued
marine benthos are predicted to be minor. |
The impacts to the benthic
communities are predicted to be minor owing to the highly disturbed
seabed, ready recolonization of benthos and low ecological importance of the
marine benthic communities. |
Impact
to the benthic communities in North Western WCZ is predicted to be negligible. |
The impacts to the benthic communities at the northern part of the WCZ are predicted to be minor since no species of conservation concern was recorded. The relative important marine resources at the southern part of the WCZ are unlikely to be affected. |
5.6.1.4
Impacts
on Marine Waters Habitat – Dolphin Habitat
The
proposed dredging activities may cause impact to the marine waters habitat
through dispersal of SS or potential release of contaminated material into the
water column. This is a potential concern for the protected dolphins inhabiting
the marine waters. The impacts on
dolphins from the coastal development projects are generally classified into
four main categories, which are land reclamation, percussive piling, dredging
of spoil and increases in vessel traffic (Jefferson 2008). Regarding the nature
of this Project, only dredging works and increases in marine traffic could
potentially affect the marine mammals.
Dredging activities will result in a loss of marine
habitat but only on a temporary basis.
There will be no residual impact on the loss of marine habitat for
marine mammals after the project is completed.
Direct Impact
Based on the results of the long-term marine
mammals surveys (AFCD 2009), it is noted that the Project site is not a major
habitat for marine mammals. In fact, there have been very few sightings of
marine mammals recorded in the Project area and its vicinity in the last 10
years (distribution maps for CWD and Finless Porpoise refer to Figures 5.6a,b and 5.7a,b respectively).
Since the Project site is situated in an existing fairway with heavy marine
traffic, the minor increase in marine traffic during construction and operation
around the project sites will not significantly increase the chance of
collision with marine mammals.
Indirect Impact associated with Change of
Water Quality
The water quality modelling results indicate that the
SS elevation will be confined to the dredging area. The water bodies near to Cheung Chau and
Indirect
Impact on Marine Mammals associated with potential bioaccumulation of toxic
contaminants
Dredging
of the seabed would potentially cause the release of toxic contaminants from
the benthic sediments. Some contaminants, such as Persistent Organic Pollutants
(POPs) and heavy metals can be bio-accumulated through diet along the food
chain and by environmental exposure, which would lead to illness of marine organisms
or even death. The potential release of contaminant from dredging of the
existing marine sediment is inferred from the results of the elutriate tests
summarised in Table 3.26 under Section
3.7.1.6 and
has been assessed in the Water Quality Impact Assessment.
During
dredging operation, toxic contaminants such as POPs and heavy metals would be potentially released from the
disturbed seabed. Suspension of exceeded
contaminated material may lead to bioaccumulation of toxic substances in
the marine mammals through the intake of polluted prey fish.
The impact of heavy metals and POPs on marine mammals including the effect on
reproductive capacity, immune system and carcinogenic, has been well documented (Jefferson 2005).
According to the Water Quality Impact Assessment
in Section 3.7.1.6, the elutriate
test results indicated that all the POPs (including PCBs, PAHs and chlorinated
pesticides) and heavy metal concentrations released from the sediment samples
at most sampling locations were below the detection limits. Given that
the predicted SS elevation is confined to the
dredging area and the predicted POPs
and heavy metal levels are within environmental acceptable standards
with the effects rapidly diluted by the large volume of marine water within the
dredging site away from the mixing zone, potential of bioaccumulation of the toxic contaminants associated
with the release of sediment due to
the dredging works of this Project is predicted to be minor. Since the
marine mammals are seldom sighted
in the Project area, the potential for
bioaccumulation of POP’s due to
this Project is further minimized, especially as prey items of the CWD
are primarily estuarine fishes in northern and western Lantau.
With reference to Figures 5.6a and b, the prime CWD habitats are to the west and
north of Lantau, and also at the Sha Chau and
Table 5.14: Impact Evaluation of Marine Water Habitats
Criteria |
|
Western
Buffer WCZ |
North
Western WCZ |
|
Habitat Quality |
Low
ecological value |
Low ecological value |
High
ecological value owing to the presence of CWD. |
Moderate ecological value owing to the presence of Finless Porpoise. |
Species |
No
recent record of dolphin. |
Low
abundance of CWD. |
High
abundance of CWD. |
Low
abundance of CWD. Low density of
Finless Porpoise population but of importance in |
Size/ Abundance |
Large |
Large |
Large |
Large |
Duration |
Construction
phase |
Construction phase |
Construction
phase |
Construction phase |
Reversibility |
Reversible after construction |
Reversible
after construction |
Reversible
after construction |
Reversible after construction |
Magnitude |
Low |
Moderate-low |
Low |
Low |
Summary |
Minor
impact owing to the low ecological value of this WCZ. |
Minor
impact owing to direct impact of dredging activities but low density of
marine mammals. |
Negligible impact owing to the far distance from dredging site and limited dispersal of the sediment plume. |
Minor
impact owing to the limited dispersal of sediment plume. |
Table 5.15: Impact Evaluation of Marine Mammals
Criteria |
Disturbance
Impact to Marine Mammals |
|
Receivers |
Chinese White Dolphin |
Finless Porpoise |
Size/Abundance |
Very Low abundance near Project area |
Very Low abundance near Project area |
Duration |
Construction phase |
Construction phase |
Reversibility |
Reversible |
Reversible |
Magnitude |
Low magnitude |
Low magnitude |
5.6.1.5
Impact
to Recognized Sites of Conservation Importance
Three locations in Southern WCZ are
identified as recognized sites of conservation importance including Cape
D’Aguilar Marine Reserve, Sham Wan SSSI and Soko Islands whilst the other two
are identified in North Western WCZ, namely Sha Chau and Lung Kwu Chau Marine
Park and San Tau Beach SSSI. With reference to the water modelling results in Appendices A3.1
and A3.2 of Chapter 3, the predicted SS elevation
will unlikely affect those five important sites (with SS elevation less than
0.1mg/l). The potential impact of the
Project on the sites of conservation importance is thus negligible.
5.6.1.6
Potential
Impacts on Marine Ecology due to Disposal of Contaminated Mud
Disposal
of Category L, M and H sediments were identified for the project. Possible
release of contaminants from the dredged materials may alter the water quality and hence, affect
the marine habitats and ecology. As
stated in Section 4.5.5 in Chapter 4 Waste
Management, maximum dredging rate is 4,000 m3 (in-situ volume) per grab dredger per
day during the dredging operations. Maximum three number of grab dredgers would
be in operation per day which would result in up to 12,000 m3 (in-situ volume) per day. In accordance with the ETWB
TCW No. 34/2002, the contaminated material must be dredged and transported with
great care, with mitigation measures strictly followed. The dredged sediment of
Category M and H must be effectively isolated from the environment upon final
disposal and shall be disposed of at designated Contaminated Mud Pits,
typically East Sha Chau which is designated for the disposal of contaminated
mud in
5.6.1.7
Potential
Impacts on Marine Ecology due to Changes in Hydrology and Hydrodynamics
Properties
The free surface hydrology of sea is a
complex of physical processes involving mainly surface runoff, subsurface flow,
evapotranspiration and hydraulics. Prediction of future behaviour of hydrologic
systems is based on calculation of various hydrodynamic properties of fluid,
such as velocity, pressure, density and temperature. Since only marine dredging
works is involved in this project, surface runoff, subsurface flow and
evapotranspiration are not considered further.
The only potential change relates to sea
water velocity and pressure. Impacts on
water velocity and pressure only occur if the construction works significantly
affect the width of channel, depth of water and nature of the substrate. Since
there will be no reclamation works or large scale seawall modification works
involved, the potential for change of channel width and substratum nature is
negligible. Owing to the depth of the seabed and free surface nature of the
Project area it is unlikely there will be any effect on the water velocity or
pressure. The environmental conditions at the dredging area for the
Contaminated Mud Pit V (CMPV) Project at Sha Chau were monitored regularly
during the dredging period and it was found that the water quality parameters
including levels of DO, depth-average Turbidity and total suspended solid
complied with the Action and Limit Levels during the dredging period (ERM
2010). The monitoring results showed no major change on the hydrology due to
the dredging activities. Since the dredging depth of this Project is shallower
than the CMPV, it is predicted that the potential impact on water quality and
hydrology is similarly insignificant. Therefore the indirect impact to the
marine ecology due to change of hydrology and hydrodynamic properties are
negligible.
5.6.1.8
Potential
Impacts on Marine Ecology due to Changes in Sedimentation Rates and Pattern
Excessive sedimentation upon seabed could
cause suffocation and smothering of marine benthic organisms in particular to
sessile animals with low mobility. Sediment released to the water column by the
dredging activities will disperse along with water current before finally
settling on the seabed. The potential impact is regarded as low as the induced
SS and sedimentation is confined to the Project area without wide dispersal to
ecologically sensitive areas such as coral sites. As indicated in the water
quality modelling results given in Appendices A3.1 to A3.3, the higher sedimentation
rates are confined to the Project area without wide dispersion. Given the
limited dispersion of sediment, the potential impact to the marine ecology is
considered to be acceptable.
5.6.1.9
Potential
Impacts on Marine Ecology due to Deterioration of Water Quality
The potential release of unionised ammonia
(UIA) and increase in ammoniacal nitrogen concentration during the dredging
activities may cause indirect disturbance to marine ecology due to toxic
effects of these substances. The toxic
effect will be increased with an increase in pH value and in warmer
temperatures. According to the water quality prediction, UIA concentration at
all the sensitive corals community indicated no exceedance of WQO during
construction phase. Thus the potential impact of increased UIA concentration on
coral communities is anticipated to be negligible.
Marginal exceedances of WQO for UIA in the
coastal waters are predicted according to the annual average water quality
modelling results, with 0.034 mg L-1 at B2 (
When comparing with the water quality
assessment guideline under the Consultancy Study on Fisheries and Marine
Ecological Criteria for Impact Assessment (City U’s CCPC 2001), it is noted
that the predicted total ammoniacal nitrogen concentrations (Table A3.12b of Appendix
3.12) at Approach Beach and Ting Kau Beach during the dry season ranged
from 0.70 to 0.86 mg L-1and are all below 0.16 mg/L during the wet season for all scenarios. The
ammoniacal nitrogen concentration were found to range from 0.06 to 0.70 mg L-1 for EMSD1 during dry season for all
scenarios (Table 3.22). It is shown
that there is a seasonal variation in terms of total ammoniacal nitrogen
prediction representing higher predicted value during the dry season compared
to the averaged value throughout the year (Table
A3.12b of Appendix 3.12).
The higher seasonal values are compared with the recommended criterion for
maximum NH3-N concentration (1.2 mg/L) for 80% protection of
fisheries and marine biota from acute effect (City U’s CCPC 2001) and are all below
the criterion.These areas are of low ecological significance and thus, the
potential toxicity effect on marine ecology at coastal waters surrounding the
proposed dredging area is anticipated to be of low impact.
5.6.1.10
Potential
Impacts on Marine Ecology due to Noise Generated by the Construction Activities
Since the construction works involve mainly
dredging and no marine piling activities, the potential impact on marine noise
affecting the marine organisms is relatively low. For the removal of hard
material within the dredging area, blasting will not be employed (cutter
suction dredger (CSD) instead), so that the potential impact is limited to SS
elevation with no significant impact relating to noise or vibration. Since the
dredging area is outside the waters identified with high density of dolphins,
the potential impact on the dolphins due to construction noise is
negligible.
5.6.1.11
Potential
Impact on Marine Ecology due to the Modification of Tsing Yi Submarine Sewage
Outfall and Demolition of the Kwai Chung Submarine Outfall
The modification of the Tsing Yi Submarine
Sewage Outfall will involve removal of the rock armour, replacement of
the existing riser pipes and non-return valves followed by re-application of
rock armour. Demolition of the Kwai Chung Submarine Outfall will involve only
the dismantling of the pipe section that is above the dredge level. The
proposed works will cause a temporary
loss of inter-tidal and sub-tidal habitats of the rock armour to be removed.
Both outfalls are located within the existing
In respect of the Kwai Chung Submarine
Sewage Outfall, the dismantling of the pipe section above the dredge level will
not require dredging of the seabed; therefore, no significant impact on the
soft-bottom sub-tidal habitat or the water quality of the surrounding waters is
expected. As such, no unacceptable
adverse impact on marine ecology is anticipated.
5.6.2
Operational
Phase
Impact on Marine
Mammals induced by Change in Marine Traffic Volume
Increased vessel
traffic can potentially increase the chance of dolphins and porpoises being
killed or injured by vessel collisions. Further, vessel traffic can also result
in acoustic disturbance to dolphins and porpoises (Jefferson et al. 2008). It may create changes in the
diving and surfacing patterns of the dolphins and porpoises to avoid collisions
with marine vessels, which in turn could displace them from their preferred
habitats. This Project will not create additional marine traffic per se;
however, a consequence of this Project is likely to be the increased port
business for the KTCP, and as a result, an increase in the ULCS berthing at
KTCP. Notwithstanding this however, the KTCP is not located within
the distribution range of either the Chinese White Dolphin and Finless Porpoise
in Hong Kong (distribution refer to Figures 5.6a,
b and 5.7a, b respectively), and
as such the potential impacts of direct collision with vessels and acoustic
disturbance is minor.
Potential Impact
from Maintenance Dredging
Although there is no significant siltation in the Project area of the KTCB, in order to account for possible increases in the sediment load in the Pearl River Estuary, a balance between capital and maintenance dredging works, has been adopted with a target dredge level of -17.5mCD to allow for 0.5m for future potential siltation.
From the findings in Section
2.7 on the need for maintenance dredging, it may be concluded that the
current trend of no appreciable siltation in the
As noted in the water quality assessment (Section
3.7.2) the future maintenance dredging will be of a much smaller scale
than capital dredging works. As the
impacts of capital works on marine ecological resources were acceptable, the
reduced scale of the works during maintenance dredging is also likely to be
acceptable. Furthermore, in view of the
fact the Project area is of low ecological value and not the prime habitat for
marine mammals, the potential impacts on marine ecology during maintenance
dredging works are considered to be negligible.
5.7 Mitigation of Adverse Environmental Impact
Environmental acceptability has already been taken into account in the planning and design of this Project to avoid and minimize any unacceptable environmental impacts through the selection of the dredger with the lowest release of SS. Grab dredgers have been selected as the preferred dredger option as it meets the technical requirements and will have limited the environmental impact compared to a trailer suction hopper dredger (TSHD), bucket ladder dredger and backhoe dredger. The number of concurrent dredgers operating at the same time is also limited to three as part of the environmental constraints. Therefore, the total daily dredging rate is restricted to 12,000m3 (in-situ volume) per day to minimize the release of SS.
To minimize any potential adverse impacts arising from the dredged marine sediment, release of dredged sediment into the surrounding water should be avoided and the distance between the barge and the dredging point should be shortened as far as possible to avoid dropping sediment from the close grab to seawater. Frame type silt curtains will also be deployed to reduce the migration of sediment plumes. As suggested in Section 4.5, the dredged sediment will be transferred to barges for subsequent disposal as allocated by Marine Fill Committee (MFC) depending on the level of contamination and disposed of at the designated disposal site according to its category.
To minimise potential impacts on water quality and marine ecology, the following measures should be taken during transportation and disposal of the dredged marine sediments for Type 1 and Type 2 disposal (ETWB TCW no. 34/2002 refers):
¡ Bottom
opening of barges shall be fitted with tight fitting seals to prevent leakage
of material. Excess material shall be cleaned from the decks and exposed
fittings of barges and dredgers before the vessel is moved.
¡ Monitoring
of the barge loading shall be conducted to ensure that loss of material does
not take place during transportation. Transport barges or vessels shall be
equipped with automatic self-monitoring devices as specified by the EPD.
¡ Barges or
hopper barges shall not be filled to a level that would cause the overflow of
materials or sediment laden water during loading or transportation.
The provision of water quality mitigation
measures would also minimize the impact on marine ecology. The general good
site practices and mitigation measures to control water quality impact proposed
in Chapter 3 Water Quality Impact
Assessment are summarised as
follows:
§
All
vessels should be sized so that clearance is maintained between vessels and the
seabed in all tide conditions, to ensure that undue turbidity is not generated
by turbulence from vessel movement or propeller wash;
§
Speed
of all vessels should be controlled within the works area to prevent propeller
wash from stirring up the seabed sediments;
§
All
barges / dredgers used should be fitted with tight fitting seals to their
bottom openings to prevent leakage of material;
§
Construction
activities should not cause foam, oil, grease, scum, litter or other
objectionable matter to be present on the water within the site or dumping
grounds; and
§
Barges
or hopper should not be filled to a level that will cause the overflow of
materials or polluted water during loading or transportation.
§
Frame
type silt curtains shall be deployed to control the migration of sediment
plumes.
With the implementation of waste management
practices and water quality control measures listed above, the potential
adverse impact on water quality would be minimized to an environmentally
acceptable level. Since no major impact on marine ecology is predicted, no
specific marine ecological mitigation measure is required.
In addition to the potential marine
ecological impacts identified in Section
5.6, other concurrent projects which involve marine works within the
Project area and vicinity will potentially impose cumulative impacts on the marine
ecological environment. The potential cumulative impacts would occur during the
construction phase – i.e. the dredging period. The marine projects which are
anticipated to be undertaken concurrently with this Project are detailed in Section 2.8.
The potential impacts of induced SS level in
the water column and associated water quality deterioration due to the dredging
and dumping activities on the soft-bottom benthos, coral communities and
inter-tidal communities arising from the concurrent projects are confined to
the North Western WCZ as reviewed in the approved EIA reports. As indicated in
the water quality modelling results presented in Section 3.7.1.2 and Appendix
3.8, the dredging works at KTCP, Northern
Fairways and Western Fairways under Scenario 3 and Scenario 7 (with concurrent
projects) indicated that no SS exceedances were found at any marine ecological
sensitive receivers. The maximum predicted sedimentation rate at all the coral
communities for Scenario 7 was less than 23 g m-2 per day (22.2 g m-2
per day at WSR CR9 Kau Yi Chau), which is well within the criterion of 100g m-2
per day. Therefore, the potential cumulative impact of the increase in
suspended solids at marine ecology sensitive receivers including coral
communities at
For the potential impact on the cetacean
species, there is negligible impact on the species from this Project and no
cumulative impact is anticipated. The potential cumulative impact on the CWD is
considered to be negligible.
5.9 Evaluation of Residual Impacts
The Project will result in the loss of
approximately 446ha of seabed. Following
completion of the dredging works the new seabed will be recolonized by benthic
organisms to develop a new benthic community. Provided that the benthic
organism can readily recolonize the dredged seabed of similar substrates in
short period of time and the existing benthic communities are of low richness
and species diversity, it is anticipated that the residual impact would be
insignificant and acceptable.
5.10 Environmental Monitoring and Audit
During construction phase, water quality
monitoring will be carried out at sensitive receivers (including some marine
ecological sensitive receivers) under an Environmental Monitoring and Auditing
(EM&A) Programme. Details of the requirement are listed in the separate
EM&A Manual. The water quality monitoring programme with action plan will
monitor any potential impact to the marine ecology induced by deteriorations in
water quality and allow quick action to be taken to alleviate the situation. No
other marine ecology-specific monitoring programme is considered necessary.
The marine ecological resources within or
around the dredging area have been studied through literature review and field
survey. Marine ecology field surveys for inter-tidal, sub-tidal hard-bottom and
soft-bottom benthic habitats were conducted between September 2009 and January
2010. The evaluation of the ecological importance of the marine habitats was
conducted through the review of the ecological resources in inter-tidal,
sub-tidal hard-bottom and soft-bottom marine benthic communities and the marine
mammals in open waters. It was found that the ecological resources in
Potential impact of loss of soft-bottom
seabed habitat due to the dredging works is considered to be minor, owing to
the high re-colonizing ability of the marine benthic communities on similar
seabed substrates after construction. According to the water quality modelling
results, the predicted sediment plume is confined to the dredging area such
that the elevation of suspended solid level around the coral sites is
considered to be within acceptable levels. Therefore the indirect disturbance
impacts to off-site habitats induced by the elevation of suspended solid
concentration in the water column and the increase in sedimentation rate is
expected to be minor. The potential impacts regarding the direct collision and
indirect disturbance to the marine mammals during the dredging activities and
operation are anticipated to be negligible since the Project area is outside
the distribution range of both the Chinese White Dolphin (Sousa chinensis) and Finless Porpoise (Neophocaena phocaenoides) in Hong Kong.
In
conclusion, the direct impacts on
marine ecology associated with the dredging works are minor owing to the
relatively low abundance and diversity of marine organism and no species of
conservation concern recorded in the highly disturbed habitats within the
Project area. The indirect impact due to change of water quality is predicted
to be negligible in view of the limited dispersion of SS, the acceptable level
of predicted sedimentation rate at coral sites and the rapid dilution effect of
the potential release of contaminants during dredging.
During the operational phase, maintenance
dredging will be of a much smaller scale than capital dredging works, and in
view of the fact that the Project area is of low ecological value and not the
prime habitat for marine mammals, the potential impacts on marine ecology are
considered to be negligible.
The potential cumulative impact of the increase
in suspended solids at marine ecology sensitive receivers including coral
communities at
With the implementation of water quality
mitigation measures and environmental monitoring and auditing programme during
the construction phase, no mitigation measures specific for marine ecology is
required. The potential marine ecological impacts of the proposed dredging,
demolition and modification of outfalls are considered to be environmentally
acceptable.
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