8
Introduction
8.1.1
This
section identifies and evaluates the nature and extent of potential impacts on
marine ecological resources in the assessment area resulting from the proposed
dredging and other marine works of the Project. Several relevant baseline studies and
assessment reports were reviewed and both direct and indirect impacts on marine
ecology were included in the assessment.
8.1.2
Where
necessary, field surveys were undertaken to check current ecological baseline
conditions. Ecological importance
of habitats and species potentially affected by the proposed works was
identified and assessed. The scale
and significance of potential ecological impacts resulting from the Project was
evaluated, and necessary mitigation measures are recommended. Residual and cumulative ecological
impacts were also identified and evaluated, and ecological monitoring and audit
requirements were discussed.
8.2
Environmental Legislation, Policies, Plans, Standards and Criteria
8.2.1
This
assessment made reference to the following HKSAR Government ordinances,
regulations, standards, guidelines and documents when identifying ecological
importance of habitats and species, evaluating and assessing potential impacts
of the Project on the ecological resources:
l Environmental
Impact Assessment Ordinance (EIAO) (Cap. 499) - aims to avoid, minimise and
control the adverse effects on the environment by designated projects through
the application of the environmental impact assessment process and the environmental
permit system.
l EIAO
Technical Memorandum on EIA Process (EIAO-TM) Annex 8 – provides guidelines for
the evaluation of the ecological impact caused by the designated project. A list of criteria is provided for
assessing the importance of habitat / species and the ecological impact.
l EIAO-TM
Annex 16 – describes 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.
l EIAO
Guidance Note No. 3/2002 - provides guiding principles on the approach to
assess the recommended environmental mitigation measures in EIA reports.
l EIAO
Guidance Note No. 6/2002 - provides some guidance on conducting ecological
assessment.
l EIAO
Guidance Note No. 11/2004 - introduces some general methodologies for marine
ecological baseline surveys.
l Wild
Animals Protection Ordinance (Cap. 170) - designated wild animals are protected
from being hunted, whilst their nests and eggs are protected from injury,
destruction and removal. All birds
and most mammals, including marine cetaceans, are protected under this
Ordinance. The Second Schedule of
the Ordinance, which lists all the animals protected, was last revised in June
1997.
l Protection
of Endangered Species of Animals and Plants Ordinance (Cap. 586) – to give
effect to the Convention on International Trade in Endangered Species of Wild
Fauna and Flora (CITES), the Ordinance strictly regulates the import,
introduction from the sea, export, re-export and possession or control of
certain endangered species of animals and plants and derivatives of those
species scheduled in Appendices I, II and III. The Ordinance came into effect on 1
December 2006.
l Town
Planning Ordinance (Cap.131) - provides for the designation of coastal
protection areas, Sites of Special Scientific Interest (SSSIs), Conservation
Area,
l The
Marine Parks Ordinance (Cap.476) and Subsidiary Legislation - allows for
designation, control and management of marine parks and marine reserves through
regulation of activities therein to protect, conserve and enhance the marine
environment for the purpose of nature conservation, education, scientific
research and recreation. The
Ordinance came into effect on 1 June 1995.
l The
Marine Fish Culture Ordinance (Cap.353) - regulates and protects marine fish
culture by designating areas of fish culture zone, granting license,
prohibiting unauthorized vessels and any deposition of chemicals or other
substance which are likely to cause injury to fish in a fish culture zone. The list of designated fish culture
zones was last revised in January 2000.
l The
Protection of the Harbour Ordinance (Cap.531) – bases on a presumption against
reclamation, the harbour is to be protected and preserved as a special public
asset and a natural heritage of
l The Water
Pollution Control Ordinance (Cap.358) – aims to control water pollution in
waters of
8.2.2
This
assessment also made reference to the following international conventions and
nearby national regulation:
l
International Union for Conservation of Nature
and Natural Resources (IUCN) 2006 Red Data Books - provides taxonomic,
conservation status and distribution information on threatened species that
have been evaluated using the IUCN Red List Categories and Criteria. This system is designed to determine the
relative risk of extinction, and the main purpose of the IUCN Red List is to
catalogue and highlight those taxa that are facing a higher risk of global
extinction.
l
The PRC National Protection Lists of Important
Wild Animals and Plants - lists detailed Category I and Category II key
protected animal and plant species under Mainland Chinese Legislation. The list was last updated in November
2002.
8.3.1
The
proposed dredging area would affect part of the existing seawall and seabed in
the
Literature
Review
8.3.2
The
assessment of ecological impact on marine habitats was undertaken with reference
to the previous baseline surveys and EIA studies for other proposed projects in
the assessment area. These include
the following:
l Agreement
No. CE 32/99, Comprehensive Feasibility Study for the Revised Scheme of South
l Agreement
No. CE 42/2001, Environmental and Engineering Feasibility Assessment Studies in
Relation to the Way Forward of the Harbour Area Treatment Scheme – Water
Quality, Ecological and Fisheries Impact Assessment (HATS EEFS Report)
l Agreement
No. CE 87/2001, Further Development of Tseung Kwan O – Feasibility Study (TKOFS
EIA)
l Agreement
No. 54/2001, Wanchai Development Phase II and Central-Wanchai Bypass
Environmental Impact Assessment (WDII & CWB EIA)
l Central
Reclamation Phase III Studies - Site Investigation, Design and Construction.
Comprehensive Feasibility Study for Minimum Option: Final Key Issues and
Initial Environmental Impact Assessment Report (CRIII EIA Report)
l Agreement
No. CE 25/2002, Drainage Improvement in Northern
l Agreement
No. CE 52/95, Strategic Sewage Disposal Scheme Environmental Impact Assessment
Study (SSDS EIA study)
l Agreement
No. CE 74/98, Wanchai Development Phase II Comprehensive Feasibility Study
(WDII EIA Report)
l CityU
Professional Services (2002) Consultancy Study on Marine Benthic Communities in
l AFCD
(2005) Monitoring of Finless Porpoises (Neophocaena
phocaenoides) in Hong Kong Waters 2003-2005
l AFCD
(2006) Monitoring of Chinese White Dolphins (Sousa chinensis) in Hong Kong Waters – Data Collection
l
l EPD
Marine Water Quality in Hong Kong 1986-2005.
Ecological
Surveys
8.3.3
Field
surveys are considered necessary to supplement and check the validity of data
collected through the literature review process. The field surveys undertaken under this
assessment include:
l Ecological
surveys on intertidal and subtidal habitats in and within the vicinity of
proposed dredging area was conducted in April 2007 (Appendix 8.5). The
survey included spot-check reconnaissance dives on selected representative line
transects and Rapid Ecological Assessment (REA) at selected transects for more
detailed survey. During the spot-check reconnaissance dives, 20 proposed
transects (Site 1 – 20) were surveyed by experienced divers and information on
GPS location, transect distance, visibility, substrate type, presence of coral
colony and other invertebrates, and estimated size, percent cover and condition
of coral were recorded. Eight transects with signs of coral colonies observed
in the spot-check dives were further surveyed by REA. A
l
Benthos survey on seabed within the proposed
dredging area was carried out in March 2007 by grab sampling method (Appendix
8.2). Five replicates of
grab samples over a
H’= -å ( Ni / N ) ln ( Ni / N ); and
J = H’ / ln S
where S is the total
number of species in the sample, N is the total number of individuals, and Ni
is the number of individuals of the ith species.
l
Intertidal communities surveys on artificial
intertidal habitats that would be directly impacted were conducted in both dry
and wet seasons using line transects where possible, with one transect deployed
on the seawall, starting from the high water mark down to low water mark. Along each transect, standard ecological
sampling quadrat was laid at
Impact Assessment
Methodology
8.3.4
Evaluation
and assessment of potential impact on ecological resources was conducted in
accordance with the criteria and guidelines specified in Annex 8 and Annex 16,
respectively, of the EIAO-TM.
8.3.5
The
significance of impacts was ranked as “low”, “moderate” or “high”. The description of the ranking is as
below:
l Low -
Impacts to species or groups are assessed as “low” if the predicted impact
would result in a slight, and / or short-term reduction in the local population
numbers or geographic distribution of a species or group, but the species or
group is predicted to recover from the perturbation with no-long term adverse
impacts. Impacts to habitat are
assessed as “low” when the habitat is widely distributed locally and that no
rare or restricted species are found in the habitat.
l Moderate
– Impacts to species or groups are considered “moderate” if the predicted
impact probably would result in non-recoverable and / or long-term reduction in
population numbers. However, the
species in question should be considered widely distributed or common, and
abundant on a local, regional or global scale. Impacts to habitat are assessed as
‘moderate” if the habitat is of limited local or regional distribution or
declining in extent and that the habitat has a potential of supporting rare and
restricted flora and / or fauna species.
l High –
Impacts to species or groups are judged to be “high” if the predicted impact
has an adverse effect on species or groups which are rare, protected or of
conservation importance locally, regionally, or globally. Impacts to habitat are considered to be
“high” if the habitat in question is of limited local or regional distribution
or declining in extent and it is generally considered by the scientific
community to be of local, regional or global importance to support rare or
restricted flora and /or fauna species.
8.3.6
If
ecological impacts on important habitat or species of conservation interest are
identified, mitigation measures would be recommended in accordance with the
EIAO-TM Annex 16 and EIAO Guidance Note No. 3/2002. Impact mitigation would be sought in the
following priority: avoidance, minimization, on-site compensation and off-site
compensation.
8.3.7
Impact
avoidance generally consists of modifications to the preferred development
options, but may in some extreme cases require abandonment of the project.
8.3.8
Impact
minimization includes any means of reducing the scope or severity of a given
impact, for example, through timing of construction programme, modification in
the design or ecological restoration of disturbed areas following the
completion of works.
8.3.9
Impact
compensation will be recommended if the effect on a given species or habitat is
irreversible and attempts will be made to compensate it elsewhere, for example,
enhancement, creation of suitable habitats or recreation of the habitat. Compensation can be on-site or off-site.
8.4
Description of the Environment
8.4.1
The
marine environment in the Project area is composed of the marine water of
Area of
Conservation Interest
8.4.2
There
are no ecological sensitive receivers, such as SSSIs, Fish Culture Zones,
Abiotic
Water
8.4.3
Under
the Water Pollution Control Ordinance (Cap. 358), the marine water within the
Project area is within the gazetted Victoria Harbour Water Control Zone. Due to the direct discharge of wastewater
after simple screening into the harbour area in the 1980s and 1990s, water
quality in the
8.4.4
However,
after the commissioning of the Stonecutters Island Sewage Treatment Works
(SCISTW) in 2002 under Stage 1 of the Harbour Area Treatment Scheme (HATS),
water quality has improved significantly, especially in the
8.4.5
However,
the levels of faecal contamination were generally high in the Harbour area,
though the
8.4.6
According
to EPD’s water quality monitoring results, water quality within the To Kwa Wan
Typhoon Shelter (TKWTS) (VT11) was similar to the Harbour area in term of water
clearance (suspended solid 1.3-7.3 mg/L), oxygenation (dissolved oxygen 3.7-8.0
mg/L), nutrient level (total nitrogen 0.51-0.58 mg/L and total phosphrous
0.04-0.09 mg/L) and faecal contamination (E. coli 150-2800 cfu per 100
ml and faecal coliforms 880-7200 cpu per 100ml).
8.4.7
In
contrast, water quality within the Kwun Tong Typhoon Shelter (KTTS) (VT4) was
more eutrophic (total nitrogen 0.84-1.73 mg/L and total phosphorus 0.13-0.37
mg/L) and less oxygenated (dissolved oxygen 2.9-6.7 mg/L), though water turbidity
(suspended solid 1.3-3.9 mg/L) and level of faecal contamination (E. coli
1500-26000 cfu per 100 ml and faecal coliforms 3200-50000 cpu per 100ml) were
more or less the same as the Harbour area (EPD, 2006).
8.4.8
As
KTTS is located at the immediate downstream of Kai Tak Approach Channel (KTAC),
the poor water quality at KTTS was mainly due to the poor water circulation and
pollution discharges from the upstream Kai Tak Nullah and other storm culverts.
8.4.9
In
general, water quality in the Harbour area has been improved recently but the
Sediment
8.4.10
The
seabed in the Harbour area is mainly composed of soft bottom sediment with
coarse particle size. The marine
sediment in Victoria Harbour (VS3), according to EPD sediment monitoring
results, is highly anaerobic (electrochemical potential -421mV to -213 mV) due
to high organic loading from sewage discharges over the years. The sediment is toxic with high level of
total sulphide (200-590 mg/kg). The
sediment is classified as Category M or H, as defined in the ETWB Technical
Circular (Works) No. 34/2002, as it is also highly contaminated with copper
(27-190 mg/kg) and silver (1.0-5.6 mg/kg) which exceed the Lower Chemical
Exceedance Level (LCEL) or Upper Chemical Exceedance Level (UCEL) (EPD, 2006).
8.4.11
Numerous
sediment toxicity studies have been conducted in the Victoria Harbour and the
sediment within the Harbour area was usually determined as polluted in nature
by ecotoxicity testing using single species or indicator groups (e.g.
barnacles, Chan et al., 1990; Rainbow and Smith, 1992; Blackmore, 1999; fish,
Kwan, 1999 and mussel, Nicholson, 1999).
8.4.12
A
recent sediment toxicity test was carried out under the HATS EEFS Study and
sediments collected from Victoria Harbour (Station XN4 and VM7) were highly
toxic to benthic amphipod Leptocheirus plumulosus, resulting in very low
survivalship of 9-31% only (CDM, 2004).
8.4.13
Sediment
contamination within TKWTS, KTTS and KTAC was one of the most serious in
Biotic
8.4.14
The
Project area comprises several broad marine habitats including:
l
Benthic habitat on soft bottom substratum at
l
Intertidal habitats on artificial seawall along
ex-airport runway and at the coastlines of TKWTS, KTTS and KTAC
l
Subtidal habitat at
l
Feeding ground of waterbirds in TKWTS, KTTS and
KTAC
8.4.15
Locations
and types of habitats are given in the above section. Habitats map is therefore
not included in this EIA.
Soft bottom benthos
8.4.16
There
have been numerous studies on benthic fauna assemblage conducted within the
8.4.17
Thompson
and Shin (1983) reported that benthic assemblages in the Harbour area were
typically of low diversity and abundance, and community structure was largely
dictated by organic pollution from sewage discharges in the past. As only a limited number of hypoxia
tolerant species can survive the bottom conditions within the study area
region, fauna was dominated by opportunists such as bivalves and polychaetes.
8.4.18
Dominant
polychaetes include Minuspio cirrifera and the best-known marine organic
enrichment indicator Capitella capitata. These polychaetes may be indicators of
moderate and severe organic pollution, respectively. The moderately pollution tolerant
bivalve Ruditapes philippinarum (stated as Tapes philippinarum)
was also found dominant in the benthic infaunal population in the same study
(Thompson and Shin, 1983).
8.4.19
Another
field survey of soft bottom benthic organisms at the seabed in the
8.4.20
The
field survey carried out for the SSDS EIA Study also confirmed a very low
species diversity and evenness for benthic assemblages in
8.4.21
A
recent study on marine benthic communities in Hong Kong showed that a coarser
sediment benthic group was found in Eastern Victoria Harbour (Station 53 &
54) as compared to eastern and southern waters, with lower species diversity
and evenness resulted (CityU, 2002).
This study showed that the benthic communities in
8.4.22
Other
recent survey for HATS EEFS Study on benthic assemblages in
8.4.23
Previous
SEKDCFS EIA Study has undertaken benthos samplings at the TKWTS, KTTS and
KTAC. Only two species of benthic
fauna were found at the TKWTS, including the dominant (>99% of all collected
specimens) polychaete (Capitella capitata) and a juvenile ocypodid carb
(Macrophthalmus sp.). The
species diversity and evenness were low (both equal to 0.049). No living organism was collected from
the sampling locations at the KTAC and KTTS, indicating the very poor habitat
quality at these areas (Arup, 2001).
8.4.24
To
fill in the information gap, recent benthos survey was carried out at the
8.4.25
A
total of 1,367 specimens were collected in the present survey. Collected taxa included annelids (36
polychaete species and an oligochaete), crustaceans (12 species), mollusks
(three species), nemertean (one species) and fish (one species). In term of individual number, 61%, 36%,
3% of specimens were polychaeta, crustacean and other taxa respectively. Polychaeta was the most abundant taxon
and Eunice indica was the most dominant species, followed by Mediomastus
sp., Cirriformia sp., Glycinde gurjanovae, Glycera chirori
and other species. The other common
taxon was crustacea which included mostly the amphipods. Table 3.1 of Appendix 8.2 showed the twenty
most abundant species found in this survey. All the species recorded in the present
survey are common and widespread in
8.4.26
Recent survey revealed similar benthos assemblages on soft bottom
seabed in the Kai Tak area and the benthic composition found in the present
survey was generally consistent with the past recorded results (see Table
3.3 of Appendix 8.2). Owing to the
long-term sewage discharge in the
Intertidal
communities (artificial)
8.4.27
The
existing artificial coastline in the Project area is made of both artificial
vertical seawalls at the area of both typhoon shelters and man-made sloping
seawalls as well as rockfills along the former
8.4.28
A
number of literatures indicated that fauna presented in seawalls and rockfills
in the other Harbour area were largely restricted to encrusting sessile
organisms such as bivalves, molluscs and barnacles (Morton and Morton, 1983;
Lee, 1985; Lee and Morton, 1985).
Fauna commonly encountered included molluscs such as the common
neogastropod (Thais clavigera) and the pollution-tolerant bivalve (Perna
viridis), as well as encrusting crustaceans such as barnacles (Balanus
spp., Tetraclita squamosa and Capitulum mitella) and the
ubiquitous mobile isopod (Ligia exotica) (Morton and Morton, 1983; Lee,
1985; Lee and Morton, 1985). Flora
is mostly restricted to algae that are either organic or nutrient enrichment
indicators such as Ulva spp. and Cladophora (Morton and Morton, 1983;
Ho, 1987; Moore, 1990).
8.4.29
A
recent intertidal fauna survey on artificial seawalls and rockfills in central
Harbour area at Wanchai, conducted under Wanchai Development Phase II (WDII)
and Central-Wanchai Bypass (CWB) EIA Study, reported that artificial seawalls
along the coastline were found to be generally inhabited densely by few species
of sessile encrusting fauna, including chiton (Acanthopleura japonica),
barnacle (Tetraclita squamosa) and bivalve (Saccostrea cucullata). The only mobile species found on the
artificial seawalls were the common Sea Slater (Ligia exotica) and
topshell (Monodonta labio).
Encrusting algae (Pseudulvella applanata and Hildenbrandia
sp.) were recorded on the surface of artificial vertical seawalls but no erect
algae or higher flowering plant was found during the survey. All of the fauna and flora are common
local intertidal species with low conservation interest. Compared with the homogenous nature of
the concrete seawalls, artificial rockfills provided a more diverse and
abundant intertidal community (Maunsell, on-going).
8.4.30
Recent
intertidal surveys within the Kai Tak area were carried out in March and May
2007 to confirm the validity of the literature results. A total of five locations were surveyed
on the intertidal assemblages, including two sites (Sites 1 & 2) at KTAC
and three sites (Sites 3, 4 & 5) on the runway along the coast of the
8.4.31
Compared
to other relevant findings within the
8.4.32
There
was no intertidal fauna recorded for all quadrats at survey locations along the
KTAC (Sites 1 and 2) in both dry and wet seasons, only algae Hincksia
mitchelliae was recorded. The habitat quality is considered as very poor
due to the poor water quality there and has very limited ecological value.
8.4.33
On
the other hand, artificial seawalls along the former runway (Sites 3, 4 &
5) were found to be generally inhabited densely by several species of sessile
encrusting fauna, such as periwinkle (Echinolittorina radiate), topshell
(Monodonta labio), limpet (Cellana grata, C. toreuma and Patelloida
saccharina), bivalve (Saccostrea cucullata) and barnacle (Balanus
Amphitrite, Tetraclita japonica and T. squamosa). The mobile species found on the
artificial seawalls included the common Sea Slater (Ligia exotica) and
crab.
8.4.34
Encrusting algae (Pseudulvella applanata and Hildenbrandia
rubra) were commonly recorded on the surface of artificial seawalls at
Sites 3, 4 & 5 while erect algae (Hincksia mitchelliae) was also
found during the recent survey. In
general, the artificial intertidal habitats within the Kai Tak area were very
common in
Subtidal
fauna
Coral
8.4.35
In
Hong Kong, the richest coral communities are found in the eastern part where
water is free from the influence of estuarine water from the
8.4.36
However,
recent dive surveys in the central
8.4.37
The
EIA study for Tseung Kwan O Further Development also identified the presence of
small colonies of hard corals with sparse cover of soft corals and gorgonians
found in Chiu Keng Wan located at the northwestern
8.4.38
Recent dive survey for HATS EEFS Study also indicated
that the shallow water of Joss House Bay and north-west Tung Lung Chau (
8.4.39
Literature review also indicated far-field soft corals
and gorgonians presented at
8.4.40
In order to provide sufficient and updated baseline
information on marine ecology in the vicinity of the Project area, recent dive
surveys included spot-check reconnaissance dives and Rapid Ecological
Assessment (REA) were carried out in April 2007. Spot-check reconnaissance
dives were first conducted to identify the extent of hard substrate with an
emphasis on gaining an overview of coral occurrence within and adjacent to the
proposed dredging area. Areas with
signs of coral colonies observed in spot-check dives were then further surveyed
using REA technique along
8.4.41
Twenty
transects (Site 1 – 20) in and within the vicinity of the proposed dredging
area were surveyed during the spot-check surveys and information on GPS
location, transect distance, visibility, substrate type, presence of coral
colony and other invertebrates, and estimated size, percent cover and condition
of coral were recorded. Eight transects with signs of coral colonies observed
in the spot-check dives were further surveyed by REA. A
8.4.42
As illustrated in Table 2 of Appendix 8.5, 20 representative
line transects of totally
Photo 1 Bottom Substrata of Kai Tak area
Boulders
Rocks
Muddy substrata
8.4.43
In all of the surveyed sites, only isolated colonies
of a species of hard coral (Oulastrea crispata) were found at Sites 9, 11, 12, 13, 14, 16, 19
and 20, with extremely low coverage of less than 1% at each survey site. Neither soft coral nor black coral was
identified during the current spot-check dives.
8.4.44
More
detailed REA surveys were then carried out at Sites 9, 11, 12, 13, 14, 16, 19
and 20. Substrata at Sites 9, 11, 12, 13, 14 and 16 were mainly medium-sized
boulders and rocks while Sites 19 and 20 comprised big boulders with fewer
rocks. In general,
8.4.45
Very
limited marine life was observed within all REA surveyed sites. Only sparse
coverage (1-5%) of single hard coral species (Oulastrea crispata) was
recorded during the REA survey.
Most of the isolated colonies were attached on the surface of the
boulders and rocks. All the
colonies found were in fair health condition and ranged from less than
Photo 2 Colonies of Oulastrea crispata with single or few polyps.
Photo 3 Layer of
sediment covering on colonies of Oulastrea
crispata
8.4.46
In general, the Project area is mainly composed of
muddy and sandy sea bottom with limited marine life, and is only sparsely
covered by scattered colonies of single coral species (Oulastrea crispata). Oulastrea crispata has a
wide range of adaptations to different environmental conditions (including
those unfavourable to corals) as well as geographic locations, which is a
result of its stress-tolerant ability (Chen, et al. 2003). With an
opportunistic life history trait, a wide range of reproductive strategies and
surface-orientation independent growth, O. crispata is able to colonise
a variety of substrata and to flourish as a pioneer coloniser of newly immersed
structures (Lam,
Marine Mammal
8.4.47
Literature
review has shown that there were no sighting or significant record of marine
mammals within the Project area. One
of the most important marine mammals in Hong Kong waters is the Chinese White
Dolphin (Sousa chinensis) which was only seen in the western estuarine
waters in Hong Kong including outer Deep Bay, north, south, east Lantau and
west Lamma (Hung, 2006). The other
common marine mammal Finless porpoise (Neophocaena phocaenoides) was
also never reported in the
Feeding ground of
waterbirds
8.4.48
Avifaunal
surveys conducted under previous SEKDCFS EIA Study (Arup, 2001) identified a
number of waterbird species, including some of conservation interest roosting
and foraging on the artificial coastline and coastal structures (e.g.
breakwater) in KTAC and KTTS.
Little Egret (Egretta garzetta) was the most abundant species
while other ardeids such as Great Egret (Ardea alba), Intermediate Egret
(Egretta intermedia), Cattle Egret (Bubulcus ibis), Grey Heron (Ardea
cinerea) and Chinese Pond Heron (Ardeola bacchus) were also found in
these areas. All wild birds
(including nest) are protected under the Wild Animals Protection Ordinance
(Cap. 170) and the ecological significance of the recorded species of
conservation interest is discussed in details below.
8.4.49
Although
Little Egret is a common ardeid which is widely distributed in the coastal
waters throughout
8.4.50
Although
Great Egret is a common resident and winter visitor in
Ecological
Importance
8.4.51
Based
on the available literature and discussion presented above, the ecological
values of marine resources present within the Project area have been assessed
and evaluated. This has been
determined in accordance with the EIAO-TM Annex 8 Table 2 criteria and is shown
in Table 8.1.
8.4.52
Soft
bottom seabed and artificial intertidal seawall are considered as very low
ecological importance based on the considerations of their highly disturbed and
man-made nature, commonness of recorded species and low in species diversity
and abundance.
8.4.53
Although
hard coral (Oulastrea crispata) was found in the subtidal
habitat, this species is common in
8.4.54
Although
coastlines along the Kai Tak area, especially areas at TKWTS, KTTS and KTAC
were found to serve as the roosting and foraging area for some waterbirds of
conservation interest, this habitat is not the sole feeding ground for these
waterbirds in the vicinity of the Project area where a number of similar
feeding areas such as the Victoria Harbour and the Causeway Bay Typhoon Shelter
can be identified. Also, given the
poor water quality and high level of human disturbance, this habitat is not
considered as an important foraging area for these waterbirds and is therefore
ranked as of low ecological significance.
Table 8.1 Criteria and Evaluation of Ecological Importance of Marine Habitats in the Project Area
|
Criteria |
Soft bottom habitat |
Intertidal habitat (artificial) |
Subtidal habitat |
Feeding ground of waterbirds |
|
Naturalness |
Subjected
to extensive anthropogenic disturbance |
Man-made habitat |
Highly disturbed by marine traffic, subjected to extensive water
pollution |
Disturbed by marine traffic and human activities |
|
Size |
Large |
Large |
Large |
Moderate |
|
Diversity |
Low,
mainly dominant by pollution-tolerant fauna |
Low, mainly composed of few intertidal fauna |
Low, species confined to those resistant to polluted water |
Low |
|
Rarity |
No
rare species found |
No rare species found |
No rare species found but only a single species of a common hard coral
(Oulastrea crispata) was recorded |
No rare species recorded but species of conservation interest
including Little Egret and Great Egret were recorded |
|
Re-creatability |
High |
Very High |
High |
High |
|
Fragmentation |
The
habitat is fragmented by the ex-airport runway |
The habitat is not fragmented |
The habitat is fragmented by the former airport runway |
Feeding grounds in the KTTS and KTAC are physically separated from the
TKWTS by the former airport runway |
|
Ecological linkage |
Not
functionally linked to any highly valued habitat in close proximity |
Not
functionally linked to any highly valued habitat in close proximity |
Not
functionally linked to any highly valued habitat in close proximity |
Not
functionally linked to any highly valued habitat in close proximity |
|
Potential value |
Very
low |
Very low |
Very Low |
Very Low |
|
Nursery ground |
No
significant record |
No significant record |
No significant record |
No significant record |
|
Age |
NA |
NA |
NA |
NA |
|
Abundance / Richness of wildlife |
Low
for abundance and species richness |
Low for abundance and species richness |
Low for abundance and species richness |
Low for abundance and species richness |
|
Ecological importance |
Very low |
Very low |
Low |
Low |
8.5
Identification of Environmental Impacts
8.5.1
Impacts
to marine ecological resources may occur during and after the proposed capital dredging
works and the regular maintenance dredging. The impacts may be derived from direct
loss of the habitats or indirect disturbance through changes to key water
quality parameters.
Direct
Impact
8.5.2
Potential
direct impacts on marine ecology arising from the Project would include loss of
habitats and the associated marine species due to dredging activities. This would include:
l Temporary
loss of approximately 57 hectares (namely the dredging area) of soft bottom
seabed and subtidal habitat at Kowloon Bay of Victoria Harbour near the
southern tip of former
l Temporary
loss of approximately
Indirect
Impact
Changes in water
quality
8.5.3
Possible
indirect impact on intertidal and subtidal habitats may include water quality
deterioration due to siltation effects during the marine works. Marine fauna especially sessile filter
feeders are susceptible to deleterious impacts from sedimentation through smothering
and clogging of their respiratory and feeding apparatus. Similarly, more turbid water may reduce
the amount of light reaching beneath the water surface, which may also be
detrimental to marine flora and fauna. This may result in both direct (e.g.
mortality) and indirect (e.g. slow growth rate, low in reproductive success
rate) impacts on marine life and may eventually cause the reduction of
population size of marine assemblage. Potential secondary impact on the
waterbird population may be resulted due to the reduced food availability
caused from the dredging works of this Project.
8.5.4
To
assess the impacts associated with elevated SS, the assessment was based on
compliance with the statutory Water Quality Objectives (WQOs) for concerned
Water Control Zones, which is set for among other reasons, to offer protection
for marine ecological resources. Water quality modelling predictions were
analysed for compliance with the WQOs through comparison of worst case
scenario’s SS level against baseline levels. Using this criterion, if the elevation
in SS levels exceeds 30% above ambient baseline conditions, adverse impacts
would be expected and suitable mitigation should be pursued.
8.5.5
There
are no WQOs regarding sedimentation rates.
To assess impacts due to sediment deposition on far-field ecological
sensitive receivers, the sedimentation rate of not exceeding 100 mg cm-2
per day (or
8.5.6
As
bottom sediment is disturbed during dredging activities and particles released
into the water column, organic and inorganic substances contained in the
sediment may be released to the water column. Released substances may cause toxic
effects to marine fauna.
8.5.7
In
addition, the release of inorganic substances may cause eutrophication and algal
bloom. Oxidation of dead algae may
use up some of the oxygen in the water.
If oxygen levels are depleted to low levels, benthic organisms unable to
tolerate such conditions may suffer hypoxia-induced mortality and / or stress
including reduced feeding and growth rate.
The WQO standard that the average-depth and bottom water DO should
remain above 4 mg/L and 2 mg/L respectively for 90% of the time was adopted.
Disturbance impact
8.5.8
Marine
works and dredging activities within the proposed dredging area may cause
disturbance impacts on the associated wildlife due to increase of background
noise and human activities.
8.6
Prediction and Evaluation of Environmental Impacts
Direct
impact
8.6.1
Direct
impacts to the marine ecological resources would include habitat loss due to
the dredging activities in the proposed dredging area. The marine works will lead to the
temporary loss of approximately 57 hectares of soft bottom and subtidal habitat
and approximately
8.6.2
Temporary
loss of these habitats would only cause minor impact on the marine ecological
system in and within the vicinity of the Project area, considering the
generally very low ecological values of the soft bottom seabed, subtidal and
intertidal (artificial) habitats as well as the associated flora and fauna
species as discussed in Section 8.4.
The only species of conservation interest identified in these affected
habitats is the small and isolated hard coral colonies (Oulastrea crispata) which
would unavoidably be affected by the dredging works of this Project. To avoid
and minimise direct loss or damage of this species of conservation interest, it
is recommended to translocate those existing coral colonies attached on rocks /
boulders located in the
hard substrata sea area within dredging site (Figure 8.3) to the other suitable
locations as far as possible. As Oulastrea crispata is not a competing
and aggressive species
(Lam,
8.6.3
Nevertheless,
based on their opportunistic nature, rapid recruitment and settlement of Oulastrea crispata is expected to occur on the available substrates of
the newly-formed seawalls after the
construction work.
Other similar benthos, subtidal and intertidal communities are also expected to
naturally re-colonise in the Project area after dredging activities and this
would recover such minor impact identified in this assessment.
8.6.4
Taking
into account of all the mitigation measures proposed including coral
translocation and provision of newly constructed seawalls, all the marine
habitats and associated flora and fauna including some small and isolated coral
colonies that would be directly affected due to this Project are all of low
ecological values and therefore such impact is considered as minor.
Indirect impact
Changes in water
quality
8.6.5
Indirect
impacts on coral and marine ecology would be associated with changes of water
quality due to dredging activities.
8.6.6
Dredging
activities would temporarily elevate the suspended sediment level and create
sediment plumes. Benthic epifauna could
be susceptible to the effects of increased sediment loads. Effects could be lethal or sublethal
through reduction in survivalship, growth rate and reproductive potential due
to stress incurred by the need to constantly flush out deposited material. The effects of sedimentation on organisms
depend on several factors, such as species tolerance to suspended solids, life
modes of organisms (sessile or free-swimming) and water movement. Potential
secondary impact of reduced food availability on waterbirds population recorded
in the Kai Tak area may be resulted if reduction of population size of marine
assemblage occurs. However, considering there are a number of similar feeding
areas within the Harbour area, the affected waterbirds are expected to displace
to the nearby alternative feeding grounds for foraging and such impact on
waterbirds is considered as minor.
8.6.7
Based
on the prediction of the sediment plume modelling for the unmitigated scenarios
under the water quality impact assessment (see Section 5), potential water
quality impact due to elevation of SS would occur at coastal waters of the
Kowloon Bay and TKWTS. A number of
mitigation measures to control water quality is therefore recommended to
confine sediment plume within the proposed dredging area and to minimize
indirect impact to the nearby intertidal and subtidal flora and fauna during
dredging operations. With the
implementation of the proposed mitigation measures as suggested in the water
quality impact assessment, the water quality modelling results indicate that
the SS elevation arising from this Project could be effectively reduced. The recorded coral
colonies found within the Project area are species with high tolerance to more
turbid water and high sedimentation (Chen, et al. 2003), potential
indirect impact on those coral colonies is expected to be minor and acceptable.
Considering that the intertidal and subtidal communities identified in the Kai
Tak area are of generally very low ecological value and in view of the impact
of SS elevation is temporary, only minor impact is anticipated.
8.6.8
Impact
is not expected to occur at the far field ecological sensitive receivers
including the coral areas located in the vicinity of
8.6.9
As
sediment in the Project area is contaminated with heavy metals and organic pollutants,
turbulence caused by dredging activities could release these substances to the
water column. Increase of toxic
substances in water could cause lethal or sublethal effects to subtidal fauna. Degree of toxic level depends on a
number of factors e.g. species tolerance, contaminant levels, water flow rate,
etc.
8.6.10
In-vitro
laboratory assessment of sediment samples indicated that the concentrations of
cadmium, copper, nickel, mercury, unionised ammonia and total inorganic
nitrogen contaminants exceeded the assessment criteria. However the laboratory tests do not take
into account the dilution factor after the contaminants are released into the
water column. Water quality modelling results predict that levels of
contaminants would be much lower than the relevant standards at monitoring
sites nearby the source. This is because any contaminants released during
dredging are immediately diluted by the large volume of marine water within the
dredging site. Thus, it is
considered that long-term off-site marine water quality impact will not occur
and any local water quality impact will be transient. (See Water Quality
Section 5 par
8.6.11
As
subtidal fauna like fish and crab are mobile, it is likely that they would
avoid the dredging area and recolonise after the marine works. Furthermore, similar refuge habitat was
available in the nearby coastal waters for the affected fauna. Thus, major impact due to release of
contaminant on subtidal organisms is not expected.
8.6.12
Nutrient
level (inorganic nitrogen and phosphorous) may also increase during dredging
activities. High levels of
nutrients in seawater can cause rapid increases in phytoplankton often to the
point where an algal bloom occurs.
An intense bloom of algae can lead to sharp decreases in the levels of
DO in the water as dead algae fall through the water column and decompose on
the bottom. Anoxic conditions may
result if DO concentration is already low or is not replenished. This may result in mortality to marine
organisms due to oxygen deprivation.
8.6.13
Based
on results of the water quality modelling (refer to Table 5.24 to Table
5.26), the concurrent dredging activities would cause a maximum DO
depletion of less than 0.02 mg/l in the Victoria Harbour as compared to the WQO
of 4 mg/l and 2mg/l for depth-averaged and bottom DO respectively. The water quality impact assessment also
predicted that the maximum elevation of total inorganic nitrogen and unionized
ammonia caused by the proposed dredging works for cruise terminal would fully
comply with the WQO of 0.4mg/l and 0.021mg/l respectively at the receiving
water near to the Project site. . Therefore,
the Project would not contribute any off-site DO and nutrient impacts.
8.6.14
As
discussed in Section 8.4, the soft bottom benthic habitats and the associated
benthic and subtidal communities in the Project area are of relatively low
ecological significance (very low to low value), so impact due to elevation of
nutrients level and DO depletion on the associated marine fauna is not expected
to be significant.
Maintenance Dredging
8.6.15
Maintenance
dredging will be required during operation of the proposed cruise terminal at a
frequency of about once every 5 to 10 years. The frequency of maintenance dredging and
the volume of dredged material would be much lower than during capital
dredging. As only minor adverse
impacts are predicted during capital dredging, maintenance dredging is not
expected to have any adverse effect on marine ecological resources with the
implementation of the water quality mitigation measures recommended for capital
dredging.
Disturbance
impact
8.6.16
During
the construction works, increased marine traffic and noise generated from
construction plant could cause disturbance impacts to the associated wildlife
including the waterbirds of conservation interest. Considering that the subtidal habitat is
highly disturbed and ranked as low ecological importance, such impact is
considered as minimal. In addition,
set against the background of intense human activities in the Project area, the
associated waterbirds are considered already well adapted to human
disturbance. It is expected that
displacement to the nearby waters for roosting and feeding area may occur
temporarily but adverse impact is not anticipated.
Overall
impact
8.6.17
Based
upon the foregoing discussion, the marine ecological impacts associated with
the Project are considered to be minor.
A summary of impact evaluation is presented in Table 8.2.
Table 8.2 Evaluation of Ecological Impacts on Marine Resources
|
Criteria |
Construction phase |
||
|
Habitat loss |
Change in water quality |
Disturbance impact |
|
|
Impacted habitat |
Benthic, subtidal
and intertidal (artificial) habitats |
Subtidal and
intertidal habitats |
Feeding ground of
waterbirds |
|
Habitat quality |
Very low to low |
Very low to low |
Low |
|
Species |
Only small and
isolated colonies of single hard coral species would be affected |
Only small and isolated
colonies of single hard coral species would be affected |
Waterbirds of
conservation interest such as Little Egret and Great Egret would be affected |
|
Size / Abundance |
Temporary loss of |
Moderate in size |
Small in size |
|
Duration |
Temporary |
Temporary |
Temporary |
|
Reversibility |
Would recover
after construction phase |
Would recover
after construction phase |
Would recover
after construction phase |
|
Magnitude |
The magnitude of
impact is considered as minor |
The magnitude of
impact is considered as minor after implementation of appropriate mitigation
measures |
The magnitude of
impact is considered as minor |
|
Overall impact |
Low (with mitigation measures) |
Low (with mitigation measures) |
Low |
8.7
Mitigation of Environmental Impacts
8.7.1
According
to EIAO-TM Annex 16, ecological impacts on habitats and the associated wildlife,
especially on those important habitat and species of conservation importance,
caused by the proposed works should be mitigated to the maximum practical
extent. Following EIAO-TM Annex 16 and EIAO Guidance Note No. 3/2002,
mitigation measures are discussed in this section to avoid, minimize, and
compensate for the identified ecological impacts, in the order of priority.
Avoidance
8.7.2
The
dredging area on seabed and seawalls is proposed to be as minimum as possible in
order to avoid extensive direct impact on existing benthic and intertidal
resources within the Project area (see Section
Minimization
8.7.3
Recent dive surveys revealed
that coral colonies that would be directly affected by the proposed dredging
works was low in species diversity (only one species) and coverage (1 – 5%),
with generally small-sized colonies and common species recorded. The subtidal
habitat was therefore considered as low ecological value. Nevertheless, to
avoid and minimize any direct loss or damage to this fauna of conservation
interest, it is recommended to translocate the potential directly affected
coral colonies attached on small rocks and boulders that are manually movable
by a diver underwater (possibly longest dimension less than
8.7.4
During
dredging operations, a number of mitigation measures to control water quality
would be adopted to confine sediment plume within the proposed dredging area
and to minimize indirect impact to the nearby intertidal and subtidal flora and
fauna. Recommended mitigation
measures include the following:
l Installation
of silt curtains around the dredgers, where appropriate, during dredging
activities; and
l Use of
closed grab dredger.
8.7.5
These
proposed water quality control measures are expected to prevent substantial
changes in water quality, and only minimal ecological impacts on marine
environment and associated wildlife would be result. As the recorded coral
species found within the Project area are in very low coverage and abundance,
and it can tolerant to more turbid water and high sedimentation, indirect
impact on existing coral colonies due to change of water quality during the
dredging activities would be considered as minor and insignificant.
8.7.6
As
recommended under the water quality impact assessment provided in Section5, the
maintenance dredging should not be programmed in wet seasons (April to
September) to minimize the potential water quality impacts. .
8.7.7
To
minimize potential disturbance impacts on the foraging ardeid population in the
Project area, appropriate good site practices on noise control shall be adopted
during the dredging works to reduce noise generated from the Project as
suggested in the noise impact assessment (Section 4).
Other Measures
8.7.8
As
described previously, impact of loss of artificial seawall habitats within the
proposed dredging area would largely be recovered since the re-construction of
new seawalls for the berth structure of the cruise terminals would provide
large area of hard substrata for settlement and recruitment of intertidal and
subtidal assemblages similar to those previously recorded from existing
habitats. As Oulastrea crispata is regarded as pioneer species and opportunistic in nature, it is very likely that coral recruitment
and settlement of this species would be established rapidly within the Project
area after the proposed marine works.
8.8
Evaluation of Residual Environmental Impacts
8.8.1
With the effective implementation of mitigation
measures proposed in Section 8.7, residual impacts to marine ecology are
expected to be relatively minor.
The loss of artificial intertidal habitats would be largely recovered
through the provision of the new seawall, which would provide suitable
conditions for recolonisation by intertidal and subtidal flora and fauna. The translocation of those directly
affected corals that are attached on movable boulders would minimise impacts to
this species of conservation interest potentially affected by the proposed
works. The most substantial residual impact would therefore be the loss of soft
bottom benthic habitat, which is unavoidable. However, this habitat and the
associated fauna are not considered of particular important in ecological
value. Therefore, residual impacts resulting from the proposed works are
considered as minimal and acceptable.
8.9
Evaluation of Cumulative Environmental Impacts
8.9.1
There
is a number of construction activities planned for other projects that would be
conducted in the vicinity of the Project area such as construction of
8.9.2
As
dredging and filling activities may be also included in the above projects, the
most important cumulative impact would be the cumulative effect on the
deterioration of water quality in the
8.9.3
The
other potential cumulative impact would be the cumulative disturbance impact to
the marine habitat and the associate wildlife arising from the increased level
of human activities and noise during the construction phase. Taking into account the existing high
level of disturbance in the Project area, no unacceptable cumulative impact would
be anticipated.
8.10
Environmental Monitoring and Audit
8.10.1
To avoid and minimise potential loss of small and
sparsely distributed coral colonies found in the Project area, it is
recommended to translocate the directly affected corals within the Project
area, as far as practicable, to the nearby suitable habitat such as
8.10.2
It
is recommended to implement monitoring of the transplanted corals after
translocation. The presence, survival and health status of each
transplanted coral colony should be carefully recorded and compared with the
baseline results collected from the pre-translocation survey. Details of the coral post-translocation
monitoring are discussed in the EM&A Manual.
8.11.1
Literature
reviews of existing information with supplement findings from recent field
surveys indicated that identified marine habitats within the Project area are
of generally very low ecological value.
There are no ecological sensitive receivers, such as SSSIs, Fish Culture
Zones and
8.11.2
Marine
habitats within the Kai Tak area include soft bottom seabed, artificial
seawalls, subtidal habitats and feeding ground of waterbirds. All the identified habitats are
considered as generally very low of ecological value due to their highly
artificial and disturbed nature. Species diversity and abundance in these
habitats were low and no rare or restricted species was recorded. The species of conservation interest
recorded within the Project area only include a single species of common hard
coral (Oulastrea crispata) (but all colonies found are small in size,
sparsely distributed and in very low coverage) and few species of waterbirds
such as Little Egret and Great Egret.
All these species of conservation interest recorded within the Project
area are common and widespread in other
8.11.3
Direct
and indirect ecological impacts arising from the Project were identified and
evaluated. The Project will result in the temporary loss of approximately 57
hectares of soft bottom benthic and subtidal habitats and about
8.11.4
Other
indirect impacts arsing from the Project would be temporary and minimised with
implementation of proper mitigation measures. Overall, no significant and unacceptable
ecological impact on marine resource is anticipated in this assessment.
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