7
Terrestrial and marine ECOLOGY
Introduction
7.1
This section of the EIA report
presents an assessment of the potential impacts on the terrestrial and marine
ecological resources associated with the improvement work at Castle Peak Road
between Ka Loon Tsuen and Siu Lam. The
project will include road widening between Ka Loon Tsuen and Tai Lam Kok, minor
dredging (14,348 m2 of area), reclamation of seabed (8,034 m2
of area) and construction of a viaduct between Tai Lam Kok and Siu Lam
section. Based on field surveys
undertaken and the relevant literatures reviewed, this section provides a
description of the physical environmental background and ecological baseline
information, predicts and evaluates the significance of impacts and recommends
mitigation measures where appropriate.
Environmental Legislation, Standard and Guidelines
7.2
This section makes reference to the
following guidelines, standards, documents and HKSAR Government ordinances and
regulations when identifying habitats and species of ecological importance,
evaluating and assessing potential impacts of the proposed development on the
ecological resources in and around the study area:
·
Forests and Countryside Ordinance
(Cap. 96) and its subsidiary legislation, Forestry Regulations;
·
Wild Animals Protection Ordinance
(Cap. 170);
·
Town Planning Ordinance (Cap 131);
·
Country Parks Ordinance (Cap 208) and
associated subsidiary legislation;
·
Marine Parks Ordinance (Cap 476) and
associated subsidiary legislation;
·
Waterworks Ordinance (Cap 102);
·
Site of Special Scientific Interest
Register;
·
Hong Kong Planning Standards and
Guidelines (HKPSG) Chapter 10, “Conservation”
·
Works Branch Technical Circular 24/94
(Planning, Environmental and Lands Branch Circular 3/94) on Tree Preservation;
·
Works Branch Technical Circular No.
4/97 (Planning, Environment & Lands Branch Technical Circular No. 1/97)
Guidelines for Implementing the policy on Off-site Ecological Mitigation
Measures;
·
Environmental Impact Assessment
Ordinance (Cap 499) and the associated Technical Memorandum on the
Environmental Impact Assessment Process (EIAO-TM), Annex 8 and Annex 16.
7.3
The report also makes reference to the
following international conventions:
·
Convention on the Conservation of
Migratory Species of Wild Animals (the “Bonn Convention”), which requires
parties to protect listed threatened or endangered migratory species occurring
within their boundaries;
·
United Nations Conventions on
Biodiversity (1992);
·
The PRC National Protection List of
Important Wild Animals;
·
Agreement between the Government of
Australia and the Government of PRC for the Protection of Migratory Birds and
their Environment;
·
Agreement on the protection of
Migratory Birds and Their Habitats by the Governments of Japan and the PRC; and
·
IUCN Red Data Books
Terrestrial Ecology
Assessment Methodology
7.4
The establishment of the baseline
terrestrial ecological profile of the study area was based on recent field
surveys as well as a review of the existing terrestrial ecological
information. Two Environmental Impact Assessment
reports and the Preliminary Project Feasibility Study for the proposed project
were mainly referenced:
·
Route 10 – North Lantau to Yuen Long
Highway Investigation and Preliminary Design as Agreement No. CE 82/97
·
Feasibility Study for Castle Peak Road
Improvements between Ka Loon Tsuen and Yau Kom Tau
·
Preliminary Project Feasibility Study
– Improvement to Castle Peak Road Between Ka Loon Tsuen and Siu Lam
7.5
The terrestrial ecological study area
covered 500 m from either side of the proposed alignment and particular focus
was given to areas that may be directly affected by the project.
7.6
Broad ecological field surveys were
then undertaken to supplement and field check the data collected through the
baseline/literature review process, covering the representative habitats of the
study area. Vegetation/habitat surveys
were conducted by a botanist to identify different habitats and vegetation
species. Wildlife such as mammals,
reptiles and amphibians, insects (butterflies and dragonflies) was searched by
an ecologist on foot in different representative habitats. An avian specialist recorded bird audibly
and visually by visiting different suitable habitats. The areas within 100m from the construction work were surveyed
intensively by walking through different habitats randomly. Other remaining areas were selectively
surveyed. Freshwater habitats i.e., Tai
Lam Chung River and fishpond were also visited and the field sampling points
were shown in Figure 7.1. All the field
data was collected between April and July 2000 covering the wet season (survey
schedule refers to Appendix 7.1). The
surveys were carried out for whole day.
7.7
Based on the literature review and the
information gathered from the field surveys, the habitat types within the
project limit were classified as woodland, tall shrubland, grassland /
shrubland mosaic, backshore vegetation, mudflat village / orchard, developed
area, active / abandoned farmland, wasteland, plantation and fishpond
vegetation. Habitat map showing the
locations of various habitat types in the study area is shown in Figure
7.2. Species list of flora and fauna is
given in Appendix 7.2. Representative
photographs of flora with conservation interests are shown in Appendix 7.4.
Description of the Environment
Habitat / Vegetation
Woodland
7.8
Woodlands within the study area were
found in scattered patches at Tai Lam with an average height of more than 6
m. The majority of the woodlands found
were recorded next to villages and orchards.
Due to their proximity to villages and orchards, introduced tree species
such as Dimocarpus longan, was
occasionally found. A total of 91 plant
species were recorded. Plant species
recorded were typical of woodlands in Hong Kong. No single dominant plant species was recorded in the study
area. Frequent tree species recorded
included common species, such as, Acronychia
pedunculata, Adiantum flabellulatum,
Albizia lebbeck, Bytteria aspera, Celtis sinensis, Gnetum montanum, Microcos
paniculata and Schefflera octophylla. The plant species recorded suggested that
these habitats were typical of secondary woodlands in Hong Kong. Five restricted plant species , Adiantum philippense (Wu &
Lee 2000), Celtis philippinensis,
Dimocarpus longan, Ipomoea stolonifera and Vitis balanseana (Xing et al.
2000), were recorded in the woodlands.
Tall Shrubland
7.9
Tall shrubland is a transitional stage
in ecological succession between shrubland and woodland. The tall shrubland recorded comprised of
woody vegetation with average heights ranging from 2 – 3 m. Tall shrublands occurred in scattered
patches at Tai Lam but were continuous at Siu Lam, and a total of 52 species
were recorded in the study area. Plant
species such as, Acronychia pedunculata,
Dalbergia benthamii, Eurya nitida, Gahnia tristis, Gordonia axillaris and Litsea
rotundifolia, were frequently found.
Two restricted plant species, Cansjera
rheedii and Celtis philippinensis (Xing
et al. 2000), were found but no rare
or protected species were recorded during the field surveys.
Grassland / Shrubland Mosaic
7.10
The grassland / shrubland mosaic was
the dominant habitat type at the Tam Lam (Figure 7.2). The species composition of this habitat was
mainly herbaceous or woody plant species with an average height of less than
1.5 m. A total of 49 plant species
including 3 rare or protected species, Alloteropsis
semialatus, Platycodon grandiflorus and Thysanotus
chinensis, were recorded (see Figure
7.2). Major plant species including the
common shrub Baeckea frutescens,
Arundinella setosa, and Eulalia
quadrinervis were recorded. The
plant species present indicated that such habitat had been frequently disturbed
by hill fires.
Backshore vegetation
7.11
A total of 43 plant species were
recorded in the backshore vegetation habitats.
Vegetation found at the backshore of sandy beaches included dominant
plant species of Clerodendrum inerme
and Vitex rotundifolia. No rare or protected species were recorded
during the field surveys.
Mudflat
7.12
A narrow strip of coastal mudflat was
located along the Tai Lam Chung River.
The coastal mudflat was dominated by Sesuvium
portulacastrum, Suaeda australis and Zoysia
sinica. A total of 10 plant species
including a restricted plant species, Thespesia
populnea (Xing et al. 2000), were
recorded and neither rare nor protected species were found.
Village / Orchard
7.13
A total of 41 tree species including
two restricted plants, Dimocarpus longan
and Manilkara achras, were recorded
in the villages and orchards. Common
fruit trees such as Clausena lansium
and Dimocarpus longan were frequently
recorded. Tree species associated with
human activity such as Macaranga tanarius
were commonly observed, while typical secondary woodland tree species such as Bridelia tomentosa were also found. No rare or protected species were found.
Developed area
7.14
Developed areas were found along the
Tai Lam Chung River. Three restricted
plant, Celtis philippinensis, Plumbago
zeylanica and Ricinus communis (Xing
et al. 2000), were
recorded. Landscape trees such as Acacia confusa and Albizia lebbeck were frequently encountered. Neither rare nor protected plants were
recorded among the 57 recorded species.
Active / Abandoned Farmland
7.15
There were three patches of farmland
within the study area (Figure 7.2).
Plant species including Dimocarpus
longan, Litchi chinensis, Conyza canadensis, Mikania micrantha and Panicum maximun were frequently
encountered. Twenty-five species
including four restricted plants, Litchi
chinensis, Celtis philippinensis, Dimocarpus longan and Vitis balanseana (Xing et al. 2000), were recorded and neither
rare nor protected species were found.
Wasteland
7.16
This habitat is defined as man-made
habitat free of development which has suffered severe human disturbance. Small patches of wasteland were found in the
study area. A total of 32 plant species
including a restricted plant, Thespesia
populnea (Xing et al. 2000), were
recorded and neither rare nor protected species were recorded.
Plantation
7.17
Plantations were generally found along
the Castle Peak Road. Ornamental
species, Acacia confusa, was commonly
recorded. A total of 49 plant species
including a restricted plant, Vitis
balanseana (Xing et al. 2000),
were recorded and no rare or protected species were found.
Fishpond vegetation
7.18
There was a small area of fishpond
adjacent to the Tai Lam Chung River.
Dominant plant species, Paspalum
distichum, was recorded and no rare or protected plant species were found
among the 18 recorded species.
Tai Lam Chung River
7.19
The stream is largely natural in the
upper portions but the end connecting to the sea had been channelised.
Wildlife and Fauna
Mammals
7.20
No mammal was recorded during the
field survey.
Avifauna
7.21
A total of 27 species of birds were
recorded within the study area. All species were common and typical to rural
Hong Kong. During the first field survey, a total of 24 species were seen and
the Crested Bulbul, Pycnonotus jocosus
was the dominant species recorded.
During the second survey, 22 species were recorded and House Swift, Apus affinis, was the dominant species.
The findings of these field surveys are presented in Appendix 7.2. Potential breeding activities including
begging food juveniles of the White Wagtail at Tai Lam River and a
food-carrying adult of the White-breasted Kingfisher was recorded, but no nest
was observed (see Figure 7.3 for locations).
Amphibian / Reptile
7.22
One small Smooth Skink, Leiolopisma reevsi, was recorded during
the field survey.
Invertebrates
7.23
Thirteen butterflies species were
recorded during the field survey. Only
one uncommon species, Graphium sarpedon,
was found. No other invertebrates of
conservation interest were recorded during the current field surveys.
Fish
7.24
No rare, endangered, nor endemic
stream fish species were found at Tai Lam Chung River. Because of the influence of the marine
water, marine fish species including Rockfish, Sebasticus marmoratus, Chicken Grunt, Parapristipoma trilineatum, Cardinal fish, Apogon quadrifasciatus, and Yellow-finned Sea-bream, Mylio Latius were occasionally found at
the lower reaches of the Tai Lam Chung River.
7.25
Marine species including Spotted Scat,
Scatophagus argus, and Yellow-finned
Sea-bream, Mylio Latius, were found
in the man-made fishpond.
Ecological Sensitive Receivers
7.26
Based on literature review, the Tai
Lam Country Park is of conservation interest in and within the vicinity of the
study area. The Country Park within the
studying boundary is dominated by shrublands and grasslands. As the proposed development may include potential
new reclamation and massive construction, far field ecological sensitive
receivers may need to be identified.
These potential off-site ecological sensitive receivers include the Tai
Lam Chung Reservoir and feng shui
woods at So Kwun Wat.
7.27
Evaluation and assessment of potential
impact on ecological resources will be conducted in accordance with Annexes 8
and 16 of the EIAO-TM. The criteria
used for evaluating the significance of an ecological impact will include:
Habitat quality;
Species;
Size / Abundance;
Duration;
Reversibility; and
Magnitude
7.28
The criteria used for evaluating a
site / habitat will include:
Naturalness and age of habitats;
Size;
Rarity of habitats and species;
Diversity;
Re-creatability;
Fragmentation;
Ecological Linkage;
Potential value;
Abundance/species richness; and
Presence or absence of breeding/nursery ground
7.29
The criteria used for evaluating
species found within a site / habitat will include:
Protection status;
Distribution; and
Rarity
7.30
The significance of impacts will be
ranked as “minor”, “moderate” or “severe” based on the criteria listed above.
The description of the ranking are as below:
7.31
Minor - Impacts to species or groups are
assessed as “minor” 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 “minor” when the habitat is
widely distributed locally and that no rare, protected or conservation
importance species are found in the habitat.
7.32
Moderate – Impacts to species or groups
are considered “moderate” if the predicted impact would result in probably
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 fauna
and/or flora of conservation or regulatory importance.
7.33
Severe – Impacts to species or groups
are judged to be “severe” 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
“severe” if the habitat in question is of limited local or regional
distribution or declining in extent and that it contains rare, protected or
conservation importance species or generally considered by the scientific
community to be of local, regional or global importance to the support of wild
fauna.
7.34
If impacts on ecological resources are
found to be significant (i.e. moderate or severe), mitigation measures will be
recommended in accordance with the Technical Memorandum. Impact mitigation will be sought in the
following priority: avoidance, minimisation, on-site compensation and off-site
compensation. Impact avoidance generally consists of modifications to the
preferred development options, but may in some extreme cases require
abandonment of the project. Impact minimisation 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. 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 e.g. enhancement, creation of
suitable habitats or recreation of the habitat. Compensation can be on site or
off site. Off-site compensation will only be recommended if the residual
ecological impacts require mitigation and all practicable on-site ecological
mitigation measures have been exhausted. The off-site mitigation measures shall
be on a “like for like” basis and will be conducted in accordance with the
Works Branch Technical Circular No. 4/97.
Ecological Importance
7.35
An evaluation of the ecological
importance of the recorded habitats in the study area has been determined in
accordance with the EIAO-TM Annex 8 criteria.
Woodland and Tall Shrubland
·
Naturalness: Natural habitats but
subjected to moderate human disturbance.
·
Size: The woodlands are approximately
8 ha, and the tall shrublands are approximately 20 ha in the study area.
·
Diversity: The diversity of the
woodlands and tall shrublands is moderate.
·
Rarity: No rare or protected species
were found in the habitats. Five
restricted plant species, Adiantum
philippense, Celtis philippinensis, Dimocarpus longan, Ipomoea stolonifera
and Vitis balanseana, were recorded
in the woodlands and two restricted plant, Cansjera
rheedii and Celtis philippinensis were
recorded in the tall shrublands.
·
Re-creatability: It will take approximately 10 to 20 years
for the woodland to be recreated. The
vegetation type of the tall shrublands is secondary and readily recreated naturally
and would recover easily from disturbance.
·
Fragmentation: The woodlands are
generally not fragmented except a small part at Ka Loon Tsuen. The tall shrublands are fragmented into
small areas.
·
Ecological Linkage: Some of the
woodlands and tall shrublands are linked to the Tai Lam Country Park.
·
Potential value: The potential value
of the woodlands and tall shrublands is considered moderate.
·
Nursery/Breeding Ground: The woodlands
and tall shrublands located east of the Tai Lam Chung River are suspected to be
a potential breeding area of White-breasted Kingfishers.
·
Age: The woodlands and tall shrublands
are relatively mature.
·
Abundance/Richness of Wildlife: Low to
moderate wildlife richness and abundance according to the survey results.
·
Ecological value: Moderate
Grassland / Shrubland Mosaic
·
Naturalness: Natural habitat but subjected
to human disturbance and hill-fire frequently.
·
Size: The grassland / shrubland mosaic
are approximately 34 ha in the study area.
·
Diversity: The diversity of grassland
/ shrubland mosaic is low.
·
Rarity: Three rare or protected
species, Alloteropsis semialatus,
Platycodon grandiflorus and Thysanotus
chinensis were found.
·
Re-creatability: The vegetation type
is secondary and readily recreated naturally and would recover easily from
disturbance. However, recolonisation by
the same rare or protected plant species is not guaranteed.
·
Fragmentation: The grassland /
shrubland Mosaic are generally not fragmented.
·
Ecological Linkage: Some grassland /
shrubland mosaic are linked to the Tai Lam Country Park.
·
Potential value: The potential value
of the grassland / shrubland mosaic is considered moderate.
·
Nursery / Breeding Ground: No record
of breeding ground was found.
·
Age: The habitats are frequently
disturbed and therefore are secondary in nature.
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey results.
·
Ecological value: Moderate.
Backshore vegetation and Mudflat
·
Naturalness: Natural habitat with
moderate human disturbance.
·
Size: The backshore vegetation is
approximately 2 ha and the mudflat is approximately 0.1 ha in the study area.
·
Diversity: The diversity of the
backshore vegetation and mudflat is low.
·
Rarity: No rare species found. A restricted plant species, Thespesia populnea, was recorded in the
mudflat.
·
Re-creatability: The habitats can be
easily re-created.
·
Fragmentation: The backshore
vegetation and the mudflat are generally not fragmented but always have a
linear shape.
·
Ecological Linkage: The present
habitats are not functionally linked to any highly valued habitat in close
proximity in a significant way.
·
Potential value: The potential value
of the backshore vegetation and mudflat is considered low.
·
Nursery / Breeding Ground: No record
of breeding ground was found.
·
Age: Not applicable.
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey results.
·
Ecological value: Low.
Village / Orchard, Developed area and Active / Abandoned
Farmland
·
Naturalness: All are man-created
habitats.
·
Size: The villages / orchards are
approximately 12 ha, the developed areas are approximately 10 ha and the active
/ abandoned farmlands are approximately 1.7 ha in the study area.
·
Diversity: The diversity of these
habitats are low
·
Rarity: No rare or protected species
were found. Three restricted species, Celtis philippinensis, Plumbago zeylanica
and Ricinus communis were recorded in
developed area, and four restricted plant species, Litchi chinensis, Celtis philippinensis, Dimocarpus longan and Vitis balanseana were recorded in active
/ abandoned farmland.
·
Re-creatability: These man-made habitat
types can be re-created easily.
·
Fragmentation: These habitats are
generally fragmented into small areas.
·
Ecological Linkage: The present
habitats are not functionally linked to any highly valued habitat in close
proximity in a significant way.
·
Potential value: The potential value
of these man-made habitats is considered low.
·
Nursery / Breeding Ground: No record
of breeding ground was found.
·
Age: Not applicable.
·
Abundance / Richness of Wildlife: Low
to moderate wildlife richness and abundance according to the survey results.
·
Ecological value: Low.
Wasteland and Plantation
·
Naturalness: All are man-made
habitats.
·
Size: The wastelands are approximately
1 ha and the plantations are approximately 2.9 ha in the study area.
·
Diversity: The diversity of these habitats
is low.
·
Rarity: No rare or protected species
were found. A restricted plant species,
Thespesia populnea, was recorded in
wasteland, and a restricted plant species, Vitis
balanseana, was recorded in plantation.
·
Re-creatability: These habitats are
secondary and readily re-created artificially and would recover easily from
disturbance.
·
Fragmentation: These habitats are
generally fragmented into small areas.
·
Ecological Linkage: The present
habitats are not functionally linked to any highly valued habitat in close
proximity in a significant way.
·
Potential value: Low value for
artificial habitats.
·
Nursery / Breeding Ground: No record
of nursery or breeding ground.
·
Age: Not applicable
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey results.
·
Ecological value: Low.
Fishpond
·
Naturalness: The fish pond is
man-created habitats
·
Size: The size is approximately 2040 m2.
·
Diversity: The species diversity of
the man-made habitats is low.
·
Rarity: No rare / protected plant species
were recorded.
·
Re-creatability: This man-made habitat
can be re-created easily.
·
Fragmentation: Not applicable.
·
Ecological Linkage: The present
habitat is not functionally linked to any highly valued habitat in close
proximity in a significant way.
·
Potential value: Low value for
man-made habitats
·
Nursery / Breeding Ground: No record
of nursery or breeding ground was found.
·
Age: Not applicable
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey result.
·
Ecological value: Low.
Tai Lam Chung River
·
Naturalness: The stream is largely
natural with the stream end had been channelised but subjected to
frequent human disturbance such as fishing activities.
·
Size: Not applicable
·
Diversity: The species diversity is
low.
·
Rarity: No rare or protected species
were found.
·
Re-creatability: The stream habitat can be re-created
artificially. However, recolonisation
by the similar stream fauna and flora are not guaranteed.
·
Fragmentation: Not applicable
·
Ecological Linkage: The present
habitat is not functionally linked to any highly valued habitat in close
proximity in a significant way.
·
Potential value: The potential value is moderate to low
·
Nursery / Breeding Ground: The
brackish habitat is not a fishery nursery ground. Breeding activities of White Wagtail was recorded but is not a
suitable breeding ground for white wagtail.
·
Age: Not applicable.
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey result.
·
Ecological value: Low.
7.36
Based on the ecological conditions
presented in the above sections, it is considered that the backshore vegetation
and mudflat within the study area have generally low value because of their low
species diversity and most of the species identified are common in Hong Kong.
7.37
The ecological value of the village /
orchard, developed area, active / abandoned farmland, wasteland and plantation
is limited given that frequent human disturbance and low species diversity in
these habitat types.
7.38
The grassland / shrubland mosaic is
considered to have a moderate ecological value because three rare / protected
plant species were identified in these areas.
7.39
The woodland and tall shrubland have
low to moderate wildlife richness and abundance and are suspected to be a
potential breeding ground of White-breasted Kingfishers. The ecological value is moderate.
7.40
The fishpond and the Tai Lam Chung
River are considered to have low ecological value as the fishpond is man-made
habitat and limited to wildlife, and the Tai Lam Chung River mouth has already
been channelised and its natural habitat has been disturbed.
7.41
Flora of ecological interest
identified within the study area (refer to Figure 7.2 for location) comprised
of three rare / protected plant species of conservation interest including Alloteropsis semialatus, Platycodon
grandiflorus and Thysanotus chinensis.
7.42
An evaluation of identified species of
ecological interest recorded in the study area has been determined in
accordance with the EIAO-TM Annex 8 criteria and is shown in Table 7.1.
Table 7.1 Evaluation
of Floral Species with Ecological Interest within Study Area
|
Species
|
Growth Form
|
Abundance
|
Protection Status
|
Distribution
|
Rarity
|
|
Alloteropsis semialatus
|
Herb
|
Occasional
|
Not Protected
|
Kau Keng Shan
|
Rare
|
|
Platycodon grandiflorus
|
Herb
|
Scarce
|
Protected
|
Grassland in Pokfulam, Sai Kung and Tuen Mun
|
Restricted
|
|
Thysanotus chinensis
|
Herb
|
Scarce
|
Not Protected
|
Nine Pin Island and Eastern Pat Sin Lang.
|
Rare
|
Identification of Environmental Impacts
Construction Phase
7.43
The potential terrestrial ecological
impacts arising from the project construction activities may include:
·
Direct impacts to the terrestrial
habitat and the associated wildlife community as a result of road construction.
·
Indirect impact to the surrounding
habitats and the associated wildlife due to increased human activities and
background noise.
Operational Phase
7.44
The potential terrestrial ecological
impacts arising from the project operational activities may include:
·
Indirect impact to the surrounding
habitats and associated wildlife due to increased human activities and
background noise.
Impact Evaluation
Construction Phase
Cumulative impact
7.45
It is known Route 10 NLYLH’s Siu Lam
Link Road and Castle Peak Road Improvement from Sham Tseng to Ka Loon Tsuen
will be undertaken in or immediately in the vicinity of the Study Area of the
project. However, it is not anticipated
that there would be any significant cumulative impact on ecological resources
because the ecological impacts of respective projects would be localised and
there is a general absence of high ecologically value areas in the vicinity.
Direct impact
7.46
It has been estimated that the natural
terrestrial habitats within the study area that are likely to be lost due to
the road improvement works include approximately 2 ha of backshore vegetation,
0.2 ha of wasteland, 0.4 ha of plantation and 0.1 ha of tall shrubland. All these habitats are of low ecological
value and therefore adverse impact to the terrestrial ecology is not
anticipated.
7.47
The potential impact on wildlife
associated with these habitats that will be directly loss is considered to be
minor given that no species of ecological importance were recorded during the
survey within these areas. In addition,
wildlife from habitat lost would be displaced to similar habitats available in
the surrounding area. The uncommon
butterfly would also find its fruit plant in the surrounding area.
7.48
The rare / protected plant species
identified is approximately 200m away from the vicinity of the construction
site, therefore adverse impacts due to construction activities is not
anticipated.
7.49
Because of the remoteness of the far
field ecological sensitive receivers, Tai Lam Chung Reservoir (approximately 2
km from the nearest construction site) and feng
shui woods at So Kwun Wat (approximately 2 km from the nearest construction
site), adverse impact due to construction activities is not anticipated.
Indirect impact
7.50
Indirect impacts to terrestrial
ecology may arise from increased human activities associated with construction
work, such as material storage and construction site runoff, if
uncontrolled. These potential impacts
to the surrounding habitats and associated wildlife are not expected to be high
because of the temporary nature of the construction work given that regular
checks on good construction practice is recommended.
7.51
Indirect impacts, such as elevation of
suspended sediment, to Tai Lam Chung River may arise from construction
activities due to construction site runoff.
These potential impacts to the Tai Lam River are not expected to be high
because of the temporary nature of the construction work given that good
construction practice is anticipated.
7.52
The bird community associated with the
terrestrial ecological resource in the study area may be temporary disturbed or
displaced due to increase human activities and background noise. The birds may be displaced to similar
habitats available in the surrounding area and recolonisation of the area after
the construction activity has completed is anticipated.
7.53
Breeding activities of bird species
recorded in the study area may be temporary disturbed due to increased human
activities and background noise.
However, all bird species recorded are commonly found in Hong Kong and therefore
adverse impact is not anticipated.
Operational phase
7.54
During the operational phase, given
that the low abundance and richness of the animal wildlife recorded as
presented, the impact due to increased human activity and background noise is
expected to be minor.
7.55
The bird community associated with the
study area may be displaced to similar habitats available in the surrounding
area due to increased background noise.
In view of the
fact that majority of the birds recorded in the study area are commonly found
in Hong Kong and that the terrestrial habitats are located in close vicinity to
major highway, it is anticipated that displacement may be temporary and the
bird community will recover from the perturbation with no long-term adverse
impact.
Overall Impact
7.56
Based upon the discussion in Section
7.45 to 7.55, the terrestrial ecological impact associated with Improvement to
Castle Peak Road development is considered low as evaluated in accordance with
Annex 8 of the EIAO-TM in the following section.
Woodland
·
Habitat quality: The habitat quality
is moderate.
·
Species: No woodland will be directly
impacted due to construction activities.
There may be potential indirect impact to the wildlife inhabiting the
area.
·
Size / Abundance: No direct habitat
loss to the woodland.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The indirect impact to
the wildlife inhabiting the secondary woodland is reversible.
·
Magnitude: Minor.
Tall shrubland, Grassland and Shrubland
Mosaic
·
Habitat quality: The habitat quality
is moderate.
·
Species: No rare or protected plant
species including the Alloteropsis
semialatus, Platycodon grandiflorus
and Thysanotus chinensis will be
directly impacted. There may be
potential indirect impact due to increased human access or uncontrolled
construction activities as they are approximately 200m away from the
construction sites.
·
Size / Abundance: Loss of area of the
tall shrubland will be approximately 0.1 ha.
No direct habitat loss to the grassland and shrubland mosaic.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The impact of loss of
habitat due to construction work is irreversible.
·
Magnitude: Minor.
Backshore vegetation and Mudflat
·
Habitat quality: The habitat quality
is low
·
Species: No rare or protected plant
species will be directly impacted.
However, there may be potential direct or indirect impact to the
wildlife inhabiting the areas.
·
Size / Abundance: Loss of backshore
vegetation will be approximately 2 ha.
No direct habitat loss to the mudflat.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The impact of loss of
habitat due to construction work is irreversible.
·
Magnitude: Minor.
Village, Orchard, Developed area, Active /
Abandoned farmland, Wasteland and Plantation
·
Habitat quality: The habitat quality
is low
·
Species: No rare or protected plant
species will be directly impacted.
However, there may be potential direct or indirect impact to the wildlife
inhabiting the areas.
·
Size / Abundance: Approximately 0.2 ha
of wasteland and 0.4 ha of plantation will be lost. No direct habitat loss to the village/orchard, developed area and
active/abandoned farmland habitats.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The impact of loss of
habitat due to construction work is irreversible.
·
Magnitude: Minor.
Fishpond
·
Habitat quality: The habitat quality
is low
·
Species: No freshwater habitat will be
directly loss due to construction activities.
However, there may be potential indirect impact to the wildlife
inhabiting the area.
·
Size / Abundance: No direct habitat
loss to the freshwater habitat.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The indirect impact to
the wildlife inhabiting the fishpond is reversible.
·
Magnitude: Minor.
Tai Lam Chung River
·
Habitat quality: The habitat quality
is low
·
Species: No brackish water habitat
will be directly loss due to construction activities. However, there may be potential indirect or indirect impact to
the wildlife inhabiting the area
·
Size / Abundance: No direct habitat
loss to the brackish water habitat.
·
Duration: The duration of impacts will
persist during construction and operation phases.
·
Reversibility: The indirect impact to
the wildlife inhabiting the area is reversible.
·
Magnitude: Minor.
Mitigation of Adverse Environmental Impacts
Habitat / Vegetation loss
7.57
On-site planting should be provided to
compensate for loss of vegetation due to construction activities. Table 7.2 shows the locations and areas
proposed for the on-site planting.
Species used for planting should take reference from the species
identified in the present tree survey and be native to the Hong Kong. Reference should also make to the landscape
mitigation measures mentioned in Sections 9.
Table 7.2 Summary
of Compensatory Woodland and Amenity Planting
Construction Practice
7.58
Erect fences where practical along the
boundary of construction sites before the commencement of works to prevent
tipping, vehicle movements, and encroachment of personnel into adjacent areas,
particularly where the rare/protected species are located.
7.59
Reinstate temporary work sites /
disturbed areas to its original condition immediately after completion of the
construction.
7.60
Check the work site boundaries
regularly to ensure that they are not exceeded and that no damage has been
caused to surrounding natural habitats.
7.61
Prohibit and prevent open fires within
the site boundary during construction and provide temporary fire fighting
equipment in the work areas.
7.62
Other good construction practices
should be implemented to minimise any disturbance to ecological resources, as
recommended in the other sections of this report, including dust suppression
measures in Section 3 and noise control measures in Section 4, surface runoff
control in Section 5, and marine sediments management measures in Section 6.
Evaluation of Residual Environmental Impacts
7.63
With the implementation of the above
recommended mitigation measures, it is considered that there would be no
adverse residual ecological impacts.
Environmental Monitoring and Audit
7.64
No Environmental monitoring and audit
is required.
Conclusion
7.65
The ecological resources within the
study area comprises a variety of habitat types including woodland, tall
shrubland, grassland/shrubland mosaic, backshore vegetation, mudflat,
village/orchard, developed area, active/abandoned farmland, wasteland, plantation
and fishpond and Tai Lam Chung River.
The terrestrial ecological impact associated with Improvement to Castle
Peak Road Development is considered low.
Grassland/shrubland mosaic were found to support three rare/protected
plant species, Alloteropsis semialatus,
Platycodon grandiflorus and Thysanotus
chinensis. No direct impact to the rare/protected plant species due to
construction is anticipated.
7.66
The road improvement works will result
in the permanent loss of approximately 2 ha of backshore vegetation, 0.2 ha of
wasteland, 0.4 ha of plantation and 0.1 ha of tall shrubland. All these habitats are of low ecological
value and therefore adverse impact to the terrestrial ecology is not
anticipated.
7.67
Mitigation measures for the
construction are recommended to minimise or avoid the potential impacts on the
terrestrial ecology. No adverse
residual impact is expected.
Marine Ecology
Assessment Methodology
7.68
The establishment of the baseline
marine ecological profile of the study area was based on recent field surveys
as well as a review of the existing marine ecological information. Two Environmental Impact Assessment reports
and the Preliminary Project Feasibility Study for the proposed project were
mainly referenced:
·
Route 10 – North Lantau to Yuen Long
Highway Investigation and Preliminary Design as Agreement No. CE 82/97
·
Feasibility Study for Castle Peak Road
Improvements between Ka Loon Tsuen and Yau Kom Tau
·
Preliminary Project Feasibility Study
– Improvement to Castle Peak Road Between Ka Loon Tsuen and Siu Lam
7.69
Field surveys were undertaken to
supplement and field check the data collected through the literature review
process. Areas of ecological interest
that would be directly or indirectly affected by the proposed project were
surveyed by a marine ecology team. All
the field data was collected between April and July 2000 (Appendix 7.1).
7.70
Based on the literature review and the
information gathered from field surveys, the marine ecological habitats in the
study area are mainly categorised into subtidal and intertidal. A habitat map showing the natural boulder
coast, artificial seawall, and beach is presented in Figure 7.4. Representative photographs of coastal habitats
is shown in Appendix 7.5.
Description of the environment
7.71
The study area falls mainly within the
North Western Water Control Zone. The Environmental Protection Department (EPD)
conducts regular marine water quality monitoring in the area and the most
relevant monitoring stations to the study area are NM2 and NM1. According to the
1998 EPD water quality monitoring results, the water quality of the nearby
waters was generally turbid (annual means, 6.5 – 7.3 NTU), moderate surface
dissolved oxygen level (annual means, 5.5 – 6.2 mg/L), moderate in inorganic
nutrients (annual means total nitrogen in the nearby areas 1.14 –1.22 mg/L and
annual means total phosphorus of the nearby areas 0.05 – 0.06 mg/L), and low in
both E. coli (annual geometric means,
110 – 300 cfu/100ml) and faecal coliforms (annual geometric means, 600 – 1300
cfu/100ml).
7.72
The following review of
habitats/species is separated into subsections: soft bottom benthos, intertidal
and marine mammals.
Soft Bottom Benthos
7.73
The benthos was studied by using
bottom grab within the proposed area of the Lantau Port and Western Harbour
Development study (APHC, 1992). The
sampling points were in the northern area of Lantau waters nearby to the
Brothers. The bottom sediment was
fairly homogeneous, with a silt content of 66%. As in the Shin & Thompson (1982) study, polychaetes were the
most abundant group of organisms found at the study sites. The species composition was similar to the
previous study with polychaete species most abundant. Notomastus latericeus,
was the most abundant of all species, composing 47% of the samples. The study’s main findings was that the
assemblages were typified by high abundance with low numbers of species and low
individual biomass.
Intertidal
7.74
The coastal waters near Tai Lam Chung
is low in salinity with moderately wave exposure (Morton and Morton,
1983). The marine ecological habitats
in the study area are categorized into natural boulder coast, artificial
seawall and beach. The artificial
seawall is mainly located between Siu Lam and area near Ka Loon Tsuen, while
the natural boulder coastline and sandy beach are located in Ka Loon Tsuen.
7.75
Quantitative field surveys were
conducted on the natural boulder coastline and the artificial seawall at Ka
Loon Tsuen in May 2000 to identify the species composition. The survey design involved sampling throughout
the intertidal zones so that the vertical range of all species was
represented. In total five transects
were laid in the coastal habitats. At
each sampling point (except beach sampling location), one 30 m horizontal
transects were set up at high and low shore, respectively. Only one transect was set up at low shore of
Ka Loon Tsuen sampling point. The
locations of field sampling points were shown in Figure 7.4. On each transect, 5 quadrats (1 ´ 1 m) were placed randomly to assess the abundance and distribution
of flora and fauna. All animals found
in each quadrat were identified to species level (or to genus level, at
minimum) (see Appendix 7.3).
Natural Boulder Coastline
7.76
The natural boulder coastline is a
typical sheltered rocky shore with little exposure to strong-waves. A field survey was conducted to identify the
species composition at the natural boulder coastline. The field survey indicated that the assemblages were of sheltered
shore communities with high quantities of winkles, Nodilittorina radiata, dominating the lower shore. Other intertidal species including common
whelk, Thais spp., limpet, Cellana toreuma, smooth limpet, Notoacmoae spp., false limpet, Siphonaria spp. and barnacles Tetraclita japonica were recorded. No rare species was recorded in the present
field survey.
Artificial Seawall
7.77
The artificial seawall has been
constructed over 20 years and small marine organisms have colonized along this
old reclaimed sea-edge (Maunsell Consultants Asia Ltd, 1996). A recent
intertidal marine ecological study between Angler’s Bay and Butterfly Beach
showed that some typical intertidal mollusks, including Nodilittorina spp, Cellana
toreuma and Thais spp. were found
(Chan, 1999). These organisms are expected to be present in the study area
since the rocky shore along Castle Peak Road is quite homogenous, in terms of
the hydrology and wave exposure (Chan, personal communication). Other marine
organisms include the common neogastropod, Thais
clavigera (Morton & Morton, 1983) and the pollution-tolerant bivalve, Perna viridis (Lee & Morton, 1983).
Barnacles Tetraclita aquamosa with Pollicipes mitella were found in the
exposed shore. On the high shore, gastropods included Nerita undata, Littorina
scabra, and periwinkles Nodilittorina
millegrana and N. pyramidalis were
found. In the winter, a turf-like
assemblage of green alga including Rhizoclonium
and Chaetomorpha spattered the middle
shore (Morton & Morton, 1983).
7.78
A field survey was conducted to
identify the species composition at the artificial seawall in Ka Loon
Tsuen. The field survey indicated that
the assemblages were of moderate exposed rocky shore communities with high
quantities of Littoriaria articulata
dominating the higher shore and Monodonta
spp. dominating the lower shore.
Other intertidal species including Nodilittorina radiata, Cellana toreuma,
Notoacmaea spp., Nerita albicilla and Thais spp.
Beach
7.79
A field survey was conducted to
identify the species composition at the beach in Ka Loon Tsuen. Five cores (diameter about 10cm, length
about 40cm) were sampled at high and low shores. The samples were sieved with 500 mm sieve and stained with rose bengal. No macro-invertebrate (>500 mm in diameter) was recorded in the present field survey.
Marine Mammal
7.80
The Chinese White Dolphin (Sousa chinensis) occurs mainly in the
western waters around Lantau Island (Jefferson, 1998). Comparatively, the area
north of Lantau Island is considered the most important habitat in Hong
Kong. Chinese White Dolphin is
protected under the Protection of the Wild Animals Protection Ordinance and the
Animals and Plants (Protection of Endangered Species) Ordinance. In a study (September 1995 to March 1998) to
investigate the population dynamics of the dolphin, dolphins were sighted in
the waters off Tai Lam Chung but close to the North Lantau coast. Chinese White
Dolphins typically feed in shallow coastal areas up to 10 m deep (Jefferson,
1998). In a weekly survey conducted for a PhD study, between 1996 and 1999, the
dolphin was only sighted once in the waters immediately off Tai Lam (Lai,
personal communication).
Ecological Sensitive Receivers
7.81
No rare or key marine organisms were
recorded (see Sections 7.71 to 7.80).
Apart from a small stretch of natural coastline at Ka Loon Tsuen, the
coastline is rather homogenous due to the artificial seawall. In view of the
lack of variety of natural intertidal habitat and the absence of rare or key
marine organisms, it is believed that the coastline may be considered to have
low ecological value. Potential marine
sensitive receivers will be the protected Chinese White Dolphin (Sousa Chinensis).
7.82
The road improvement works would
involve dredging and reclamation. Potential far-field marine sensitive
receivers may be impacted by sediment plume and potential deterioration of
water quality. The nearest marine sensitive receivers include the Ma Wan Fish
Culture Zone and nursery ground off the north coast of Lantau. Assessment of impacts will be addressed in
Chapter 8 regarding impacts on fisheries.
Assessment Criteria
7.83
The assessment criteria are the same
as described in Section 7.27 to 7.34.
Ecological Importance
7.84
According to the Technical Memorandum
of the EIAO (EIAO-TM) Annex 8 the ecological value / importance of a habitat
can be evaluated using the following criteria:
·
naturalness;
·
size;
·
diversity;
·
rarity;
·
re-creatability;
·
ecological linkage;
·
potential value;
·
nursery ground;
·
age; and
·
abundance.
7.85
Based on the available literatures and
discussion presented above, the current ecological assessment shows that the
marine ecological resources present within the study area are considered to be
of low ecological value. This has been
determined on the basis of the considerations in accordance with the EIAO-TM
Annex 8 Table 2 criteria.
Soft bottom benthic habitat
·
Naturalness: The soft bottom benthic
habitat is in its natural state.
·
Size: The area to be dredged is
approximately 14,348 m2, and the area to be reclaimed is
approximately 8,034 m2.
·
Diversity: Reviewed literatures
indicated that the subtidal habitat supports low diversity assemblages.
·
Rarity: No rare / protected species
were recorded.
·
Re-creatability: The subtidal habitats
cannot be recreated on site.
·
Fragmentation: Not applicable.
·
Ecological Linkage: The present
habitat is not functionally linked to any highly valued habitat in close
proximity.
·
Potential value: The potential value
is low. It is unlikely that the site
can develop conservation interest as the water quality is unlikely to improve
significantly in the near future.
Predicted long-term water quality showed an increasing nutrient
enrichment in the coastal waters in the study area. Long-term trend in E. coli
also showed significant increase between 1989 and 1998 related to increased
sewage input from nearby area.
·
Nursery / Breeding Ground: No record
of significant nursery or breeding ground was found.
·
Age: Not applicable
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the reviewed literatures.
·
Ecological value: Low.
Artificial Seawall
·
Naturalness: The habitat is man-made.
·
Size: The artificial seawall that will
be directly impact is approximately 1.1 km.
·
Diversity: The species diversity of
the man-made habitats is low.
·
Rarity: No rare / protected species
were recorded.
·
Re-creatability: This man-made habitat
can be re-created easily.
·
Fragmentation: Not applicable.
·
Ecological Linkage: The present
habitat is not functionally linked to any highly valued habitat in close
proximity.
·
Potential value: Low value for
man-made habitats
·
Nursery / Breeding Ground: No record
of significant nursery or breeding ground was found.
·
Age: Not applicable
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey result.
·
Ecological value: Low.
Natural Rocky Shore
·
Naturalness: The natural shore at Ka
Loon Tsuen is disturbed by human activities through development of artificial
seawall.
·
Size: The natural rocky shore that may
be indirectly impacted is approximately 300m.
·
Diversity: The species diversity is
low. The intertidal communities are
typical of sheltered rock shores in Hong Kong.
·
Rarity: No rare / protected species
were recorded.
·
Re-creatability: If destroyed, the
natural rocky shore can be recreated by artificial seawall construction. However, re-colonisation by the same marine
communities is not guaranteed.
·
Fragmentation: Not applicable.
·
Ecological Linkage: The present
habitat is not functionally linked to any highly valued habitat in close
proximity.
·
Potential value: The potential value
is low since no rare species nor species of conservation interest were found.
·
Nursery / Breeding Ground: No record
of significant nursery or breeding ground was found.
·
Age: Not applicable
·
Abundance / Richness of Wildlife: Low
wildlife richness and abundance according to the survey result.
·
Ecological value: Low.
Marine Waters off Construction Sites
·
Naturalness: Disturbed through
residential discharges. Close proximity
to one of the busiest shipping lanes in Hong Kong.
·
Size: Not applicable
·
Diversity: Not applicable.
·
Rarity: The Chinese White Dolphin (Sousa chinensis) has been recorded in
these water.
·
Re-creatability: The habitat cannot be
recreated.
·
Fragmentation: Not applicable.
·
Ecological Linkage: Preferred marine
mammal habitats occur to the west of this area (around the Sha Chau, Lung Kwu
Chau Marine Park and the new airport).
·
Potential value: Limited value due to
heavy navigational use of the area.
·
Nursery / Breeding Ground: No record
of significant nursery or breeding ground was found.
·
Age: Not applicable
·
Abundance / Richness of Wildlife:
Seasonal changes in the distribution patterns of dolphins were observed, with
comparatively higher abundance in autumn and winter. However, these abundances are low when compared with preferred
habitats to the west.
·
Ecological value: Low as sighting of
Chinese White Dolphin (Sousa chinensis)
is not common in this area and this area is heavily used by marine traffic at
present.
Identification of Environmental Impacts
7.86
Impacts to marine ecological resources
may arise during the construction and operational phase. Sea-based construction activities include
construction of seawall, dredging and reclamation, bored piling for viaduct
foundation. The impacts may be derived
from direct disturbance to the habitat and indirect disturbance through changes
to key water quality parameters.
Construction Phase
7.87
The potential marine ecological
impacts arising from the construction activities may include:
·
direct impacts from habitat loss and
the associated marine species due to reclamation and the road improvement works
conducted to the artificial seawall; and
·
indirect impacts to the habitat and
the associated fauna due to dredging.
Operational Phase
7.88
Marine ecological impacts during the
operation phase also include site runoff to adjacent waters. Toxic chemicals/oil spilt from vehicles may
enter the marine waters via the drainage system
7.89
The foundation of the viaduct may
affect the water flow between Tai Lam Chung River mouth and the marine
environment.
Prediction of Environmental Impacts
Construction Phase
Direct Impacts
Subtidal habitat
7.90
Dredging and reclamation in the study
area will lead to the permanent loss of approximately 14,348 m2 of
soft bottom benthic habitats of low ecological value.
Intertidal habitat
7.91
The artificial seawall of
approximately 1.1 km will be temporarily removed due to the reclamation and the
road improvement works. However, the
existing natural boulder coastline and the beach at Ka Loon Tsuen will remain
intact during construction.
Marine Mammal
7.92
As cetacean are protected under the
Wild Animals Protection Ordinance (Cap 170), any lethal and sub-lethal impacts
due to underwater noise on marine mammals will be deemed unacceptable. Cetaceans are animals that rely heavily on
acoustic information to communicate and to explore their environment. Therefore, any noise that disrupts
communication or echolocation channels would be potentially harmful. High explosives produce pulses with a very
rapid onset (shock waves), which change to conventional acoustic pulses as they
propagate. The reactions from impacted
cetaceans can range from brief interruption of normal activities to short- or
long-term displacement from noisy areas.
Strong sound may cause temporary or permanent reductions in hearing
sensitivity. No underwater blasting or
percussive piling will be used in this road improvement works, therefore,
adverse impact to the marine mammals, such as Chinese White Dolphin (Sousa chinensis), is not anticipated.
Indirect Impacts
7.93
The present construction adopts an
approach where permanent and temporary seawalls will first be formed to enclose
each phase of the reclamation and filling materials will be pumped ashore
behind the seawalls. The sediment plume
is effectively contained within the reclamation area, minimising the loss of
fine sediments to the adjacent water bodies.
7.94
Indirect impacts to marine ecology
during construction include sediment release associated with the above
construction works. Potential impacts
to water quality from sediment release are listed below:
Elevation of Suspended
Solids:
7.95
Sessile organisms within the benthos
will be susceptible to the effects of increased sediment loads. Effects can be lethal or sublethal through
reduction in reproductive potential due to stress incurred by constantly having
to flush out the depositing material. The
effects of sedimentation on organisms will also depend on other factors, such
as an organism’s tolerance, growth orientation of sessile organisms and water
movement.
7.96
Based on the prediction that the
potential water quality impact due to elevation of suspended solids
(approximately 37 mg/L) would confines to waters at Tai Lam Kok (see Section
5). As the soft bottom benthic habitat
in this area is of low ecological value and the intertidal communities are
expected to recolonised this area after the construction activities, adverse
impact due to elevation of SS is not anticipated.
Reduction of Dissolved
Oxygen:
7.97
The relationships between SS
originated from construction works and DO are complex, with increased SS in the
water column combining with a number of other effects to reduce DO
concentrations in water. Elevated SS
(and turbidity) reduces light penetration, lowers the rate of photosynthesis of
phytoplankton (primary productivity) and thus lowers the rate of oxygen
production in the water column. This
has a particularly adverse effect on the eggs and larvae of fish, as at these
stages of development high levels of oxygen in the water are required for
growth due to high metabolic rates. DO
depletions are most likely to affect sessile organisms as they cannot move away
from affected areas. As the soft bottom
benthic habitats and the associated communities in the study area of low
ecological value, adverse impact due to reduction of dissolved oxygen is not
anticipated.
Elevation of Nutrients
7.98
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 dissolved oxygen in the water as
dead algae fall through the water column and decompose on the bottom. Anoxic conditions may result if DO
concentrations are already low or are not replenished. This may result in mortality to marine organisms
due to oxygen deprivation. As the soft
bottom benthic habitats and the associated communities in the study area of low
ecological value, adverse impact due to elevation of nutrients is not
anticipated.
Operational Impacts
7.99
During the operational phase, toxic
chemicals contained in gasoline oil spilled from vehicles can enter the marine
waters via the drainage system and may impact ecological resources. However, the design of the project and its
safety management are expect to prevent such oil spillage from vehicles and
adverse impact is not anticipated.
Impact Evaluation
Construction Phase
7.100
The dredging, reclamation and the
associated road improvement works will result in the permanent loss of
approximately 14,348 m2 of soft bottom benthic habitat and
temporarily loss of approximately 1.1 km of artificial seawall. Since the benthic community and intertidal
community in the study area are of low ecological value, minor impact is
envisaged. Moreover, armour stone
random placed seawall designs are proposed as this seawall designs will increase
the surface area for recolonisation of marine organisms. Therefore, it is envisaged that such seawall
would not cause adverse impact to the recolonisation of intertidal marine
organisms. Similar intertidal flora and
fauna existing at present are expected to recolonise at the new seawall.
7.101
Based on the prediction of
construction phase water quality modeling, impacts to benthic and intertidal
assemblages immediately outside of the reclamation site are expected to occur
during the construction phase. However,
since the seabed community and intertidal community in the vicinity of the
study area in Tai Lam Kok are of low ecological value and in view of the impact
of suspended solids elevation is temporary, only minor impact is envisaged.
Operational Phase
7.102
Marine ecological impacts during the
operational phase include site runoff to adjacent waters. Toxic chemicals / oil spilt from vehicles
may enter the marine waters via the drainage system. However, the design of the road and its safety management are
expected to prevent such oil spillage from vehicles, therefore, adverse impact
to marine ecology due to oil spillage is not anticipated.
7.103
The foundation of viaduct involved
four piles only and they are located far from the mouth of Tai Lam Chung
River. The alternation of water flow is
not anticipated.
Overall Impact
7.104
Based upon the discussion described in
Sections 7.100 – 7.103, the marine ecological impact associated with proposed
road improvement works is considered to be low. An evaluation of the impact in accordance with the EIAO-TM Annex
8 Table 1 is presented as follows:
·
Habitat Quality: Artificial intertidal
habitat of low ecological value will be lost and replaced with artificial
seawalls. Low quality soft bottom
benthic habitats will be lost. Soft
bottom benthic habitats in the vicinity of the construction area will be
perturbed by SS elevation but they are of low ecological value.
·
Species: No rare species nor species
of conservation value were found in the study area for each type of habitat
identified.
·
Size: Artificial seawall of low
ecological value (approximately 1.1 km) and soft bottom benthic habitat of low
ecological value (approximately 14,348 m2) will be directly impacted
in the vicinity of the construction sites.
Based on the water quality assessment, the impact of SS elevation is
expected to be localized in a small area, therefore, the size of the indirectly
impacted area is expected to be small.
·
Duration: Increases in SS levels are
expected to be low and temporary (approximately 90 day dredging at Tai Lam Kok,
approximately 120 days dredging for road widening) and within environmentally
acceptable level (see Section 5).
·
Reversibility: Except for the habitat loss of the
intertidal hard bottom assemblages covering approximately 1.1 km artificial
seawall and subtidal soft benthos covering an area of approximately 14,348 m2,
impact to the marine ecological resources within the study area are expected to
be temporary and recolonisation of seawalls at the construction sites is
expected to occur after the construction works.
·
Magnitude: The impacts to the habitats identified will be of minor
magnitude.
Mitigation of Adverse Environmental Impacts
7.105
Apart from the proposed use of armour
stone random placed seawall construction, no mitigation measure is required
since no unacceptable ecological impact is envisaged.
Environmental Monitoring & Audit
7.106
No environmental monitoring and audit
is required since no unacceptable ecological impact is anticipated.
Conclusion
7.107
Literature reviews of existing
information supplemented with the results of recently undertaken field surveys
on marine ecological resources indicate that the intertidal habitats and soft
benthic habitats within the study area are of low ecological value. There is a sensitive receiver, Chinese White
Dolphin, in the vicinity of the study area.
But their presence are unusual in or around the proposed project areas
and hence impact is not envisaged.
7.108
The dredging / reclamation and the
road improvement works will result in the permanent loss of approximately
14,348 m2 of soft bottom benthic habitat and temporary loss of
approximately 1.1 km of artificial intertidal habitat. Since the benthic community and intertidal
community in the study area are of low ecological value, minor impact is
envisaged.
7.109
Based on the prediction of
construction phase water quality assessment, impacts to benthic and intertidal
assemblages immediately outside the reclamation site are expected to occur
during the construction phase. However,
since the seabed community and intertidal community in the vicinity of the
study area are of low ecological value and in view of the impact of suspended
solids elevation is temporary, minor impact is envisaged.
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Personal
Communication
1.
Chan, K. K. PhD. The University
of Hong Kong
2.
Lai, H. Y. PhD. Candidate. The
University of Hong Kong