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Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-1 B&V / ERM
5. ECOLOGICAL IMPACT ASSESSMENT
5.1 Introduction
This Section presents the findings of an assessment of the potential ecological impacts
associated with the construction and operation of the proposed Project in South Lantau. It
summarises the baseline information gathered from a literature review and baseline
ecological surveys on the terrestrial and marine ecological resources in South Lantau, and
describes the ecological importance of this area.
5.2 Legislation Requirement & Assessment Criteria
5.2.1 Technical Memorandum
The criteria for evaluating ecological impacts are laid out in the EIAO-TM. Annex 16 of
the EIAO-TM sets out the general approach and methodology for the assessment of impacts
to ecological resources arising from a project or proposal. Annex 8 of the EIAO-TM
recommends the criteria that can be used for evaluating such impacts.
5.2.2 Other Legislation
Legislative requirements and evaluation criteria relevant to this Study for the protection of
species and habitats of ecological importance include:
Country Parks Ordinance (Cap 208);
Forests and Countryside Ordinance (Cap 96);
Marine Parks Ordinance (Cap 476);
Wild Animals Protection Ordinance (Cap 170);
Protection of Endangered Species of Animals and Plants Ordinance (Cap 586);
Town Planning Ordinance (Cap 131);
Hong Kong Planning Standards and Guidelines Chapter 10 (HKPSG);
EIAO Guidance Note No. 6/2010, 7/2010, 10/2010 and 11/2010
United Nations Convention on Biodiversity (1992);
IUCN Red List of Threatened Species;
Convention on Wetlands of International Importance Especially as Waterfowl
Habitat (the Ramsar Convention); and
PRC Regulations and Guidelines.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-2 B&V / ERM
5.3 Baseline Condition
This section details the baseline conditions of both terrestrial and marine ecological
resources of the habitats at South Lantau.
5.3.1 Terrestrial Ecology
In accordance with the requirements given in Clause 3.4.2.2 of the EIA Study Brief, the
Study Area for terrestrial ecology is defined by a distance of 500 m from the Project
Boundary (Figure 5.1). The Study Area covers a total area of approximately 1,215 ha in
southern Lantau Island including Lantau South Country Park and the areas zoned under the
Outline Zoning Plan as Coastal Protection Area and Green Belt.
Baseline conditions for each ecological component of the terrestrial environment of the
Study Area were evaluated based on information from the literature and focused field
studies conducted for the purposes of this EIA. Findings of the literature review and
baseline field surveys of the Study Area are summarised in the following sections.
5.3.2 Literature Review
A review of literature and recent aerial photographs was conducted to determine the
existing terrestrial ecological conditions within the Study Area, identify habitat resources
and species of potential conservation importance, and identify potential information gaps
in the baseline conditions of the habitats. The literature reviewed includes:
Porcupine! (1)
;
Hong Kong Biodiversity (2)
;
Revised Concept Plan for Lantau (3)
;
Field guides for terrestrial wildlife of Hong Kong (4)
;
EIA Report for Integrated Waste Management Facilities Phase 1 (5)
;
EIA Report for Liquefied Natural Gas (LNG) Receiving Terminal and Associated
Facilities (6)
;
EIA Report for Drainage Improvements in Southern Lantau (7)
;
EIA Report for Improvement to Tung Chung Road Between Lung Tseng Tau and
Cheung Sha (8)
;
(1) Newsletter of Department of Ecology & Biodiversity, The University of Hong Kong. Issues 1 to 33
(2) AFCD Biodiversity Newsletters. Available at: https://www.afcd.gov.hk/english/publications/publications_con/pub_con_hkbio.html
(3) Lantau Development Task Force (2005) Revised Concept Plan for Lantau
(4) Relevant field guides for terrestrial wildlife of Hong Kong available at:
https://www.afcd.gov.hk/english/conservation/hkbiodiversity/leaflets/leaflets_oth.html
(5) AECOM (2011) Integrated Waste Management Facilities Phase 1 – Feasibility Study: EIA Report Register No. AEIAR-123/2012
(6) ERM (2006) Liquefied Natural Gas (LNG) Receiving Terminal and Associated Facilities: EIA Report. EIA Register No. AEIAR-106/2007
(7) Maunsell (2005) Drainage Improvements in Southern Lantau: EIA Report. EIA Register No. AEIAR-093/2005
(8) Mouchel Asia Ltd (2002) Improvement to Tung Chung Road from Lung Tseng Tau to Cheung Sha: EIA Report. EIA Register No. AEIAR-
061/2002
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
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EIA Report for 132 kV Supply Circuit from Pui O via Chi Ma Wan Peninsula via
Sea Crossing towards Cheung Chau (9)
; and
Project Profile for Telecommunication Installation at Lot 591SA in DD328, Tong
Fuk, South Lantau Coast and the Associated Cable Landing Work in Tong Fuk,
South Lantau for the North Asia Cable (NAC) Fibre Optic Submarine Cable
System (10)
.
Project Profile for Asia-America Gateway (AAG) Cable Network, South Lantau
Lantau South Country Park
Over 50% of the Study Area (approximately 597 ha) is located within the Lantau South
Country Park (CP) designated under the Country Parks Ordinance in 1978. The Park
comprises an extensive area inhabiting many flora and wildlife such as, snakes, birds,
freshwater fish and protected plant species. Species of ecological interest include Hong
Kong Magnolia, orchids, Ferret Badger, Chinese Muntjac, Wild Boar and Romer’s Tree
Frog (11) (12) (13)
.
Green Belt
About 25% of the Study Area (approximately 295 ha) is located within the Green Belt (GB)
designated in the Outline Zoning Plan (OZP). The planning intention of GB is primarily to
define the limits of development areas, to preserve existing well-wooded hillslopes and
other natural features, as well as to provide passive recreational outlets for the local
population and visitors. GB mainly covers the extensive well-vegetated uplands and
hillsides, spurs and stream valleys, coastal pockets of land and isolated knolls adjoining the
Lantau South Country Park.
Coastal Protection Area
A long strip of land (approximately 162 ha) along the South Lantau Coast is zoned as
“Coastal Protection Area” (CPA) which covers backshore coastal habitats and the sandy
shore of the gazetted bathing beaches at Pui O, Cheung Sha and Tong Fuk. The purpose of
CPA is to protect the landscape and ecological value of these areas and/or to serve as a
buffer against encroachment of urban development into Country Parks, Special Areas and
Sites of Special Scientific Interest (SSSIs) (14)
.
Areas of Ecological Importance / Interest
Within the Study Area, a number of ecologically important / sensitive sites and habitats,
including Fung Shui woodlands in Tong Fuk and Shui Hau, the mangroves in Pui O and
(9) Mott Connell Limited (2001) 132 kV Supply Circuit from Pui O via Chi Ma Wan Peninsula via Sea Crossing towards Cheung Chau: EIA Report.
EIA Register No. AEIAR-051/2002
(10) ERM (2000) Telecommunication Installation at Lot 591SA in DD328, Tong Fuk, South Lantau Coast and the Associated Cable Landing Work in
Tong Fuk, South Lantau for the North Asia Cable (NAC) Fibre Optic Submarine Cable System: Project Profile. DIR-031/2000
(11) AFCD website. Lantau South Country Park.
http://www.afcd.gov.hk/english/country/cou_vis/cou_vis_cou/cou_vis_cou_ls/cou_vis_cou_ls.html
(12) Mouchel Asia Ltd (2002) Op Cit
(13) Mott Connell Limited (2001) Op Cit
(14) Planning Department (2001) Southwest New Territories Development Strategy Review. Final Report.
http://www.pland.gov.hk/pland_en/p_study/comp_s/swnt/final-report/final-report.htm
Outlying Islands Sewerage Stage 2 –
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horseshoe crab nursery ground in Shui Hau, are identified under the Revised Concept Plan
for Lantau, of which the mangroves in Pui O and horseshoe crab nursery ground in Shui
Hau fall within either the Lantau South CP or CPA.
In addition, to facilitate better planning for government construction projects and to
enhance protection on natural streams/rivers, Pui O and Tong Fuk streams are identified by
the AFCD as Ecologically Important Streams (EIS) with important ecological functions
such as providing habitats for diverse or rare animal or plant communities (15)
.
Terrestrial Habitats, Vegetation & Wildlife
Focused field surveys have been conducted at Chi Ma Wan (Ha Keng), Pui O Wan,
Cheung Sha and Shek Pik as part of the environmental impact assessments (EIA)
mentioned above (Figure 5.2). The most recent surveys completed were, however,
undertaken in April 2006 around Shek Pik and January 2010 around Cheung Sha, and no
recent field surveys have been conducted around the proposed project sites at Shui Hau,
Tong Fuk, San Shek Wan, Pui O and Ham Tin (Table 5.1).
Table 5.1 – Survey Periods for Previous Relevant Projects Project Major Survey Location Field Survey Period
Improvement to Tung Chung Road from Lung
Tseng Tau to Cheung Sha
Cheung Sha and Tung
Chung road
April 2001 – January 2002
132 kV Supply Circuit from Pui O via Chi
Ma Wan Peninsula via Sea Crossing towards
Cheung Chau
Pui O October 2000 – September 2001
Liquefied Natural Gas (LNG) Receiving
Terminal and Associated Facilities
Shek Pik February 2004 – April 2006
Drainage Improvements in Southern Lantau
Mui Wo July 2003 – March 2004
Integrated Waste Management Facilities Phase 1 Cheung Sha August - January 2010
Table 5.2 presents the major terrestrial habitats and associated wildlife identified within the
Study Area based on the above previous field surveys.
Table 5.2 – Major Terrestrial Habitats Identified within the Study Area (Information Based
on Literature Review) Habitat Description
Fung Shui
Woodland
Found at isolated locations near Shui Hau and Tong Fuk. Fung Shui Woodland are relatively old
growth with a height ranging from 6 m to 15 m and have not been disturbed for 20 to 50 years, and
are considered to be of high ecological value (1) (6)
Secondary
Woodland
Small area of secondary woodland located at Ngau Kwu Wan and Wang Tong.
Mainly located at the east of Pui O Wan, and around San Shek Wan and Cheung Sha.
Ecological value is generally expected to be moderate to high (1).
Two plant species of conservation importance were recorded in this habitat type near Pui O,
including Uvaria calamistrata and Malaisia scandens
Six plant species of conservation importance were previously recorded in Pui O in other EIA
study (1) including five rare to very rare species, Ailanthus fordii, Malaisia scandens, Uncaria
hirsuta, Uvaria calamistrata, and Xenostegia tridentata and one locally common but protected
species in China and Guangdong (Aquilaria sinensis).
(15) Environment, Transport and Works Bureau Technical Circular (Works) No. 5/2005 - Protection of natural streams/rivers from adverse impacts arising
from construction works
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Habitat Description
Mixed Shrubland Mainly located on the Chi Ma Wan Peninsula.
Shrubland is the dominant habitat and mainly located at Tong Fuk and Shui Hau as a continuous
area.
Ecological value is generally expected to be low to moderate (1).
Four species of conservation importance identified around Pui O, including Artocarpus
hypargyreus (found at southeast Pui O Wan), Epiphyte Cleisostoma simondii (found at southeast
Pui O Wan), Pitcher Plant Nepenthes mirabilis (found at southeast Pui O Wan) and Common
Rat Snake Ptyas mucosus (found near Shap Long Kau Tsuen) (1). These are either protected in
HK or listed as PRC Class II protected species.
Two species of conservation importance have been identified around Chi Ma Wan. Black Kite
Milvus migrans (found flying over the shrubland at Tai Long Wan) and, Pitcher Plant Nepenthes
mirabilis (found near Ha Keng) (1). Both are protected in Hong Kong and Black Kite is listed as
PRC Class II protected species.
Plantation
(Cheung Sha &
West Pui O Wan)
Exotic plantation is found along the Lantau Trail and South Lantau Road.
Ecological value of this habitat is generally considered to be moderate to high (4).
Two species of conservation importance identified which is the endemic Romer’s Tree Frog
Liuixalus romeri (found near Cheung Sha) and the Hong Kong Newt Paramesotriton
hongkongensis (found near Pak Kung Au) (2), which are protected species in HK. The toads
Leptolalax pelodytoides and Megophrys brachykolos were also reported previously near Cheung
Sha.
Shrubland/
Grassland Mixture
Grassland is mainly located at Tong Fuk and Cheung Sha, uphill of the South Lantau Road.
One locally protected species, Aquilaria sinensis, recorded in shrubland of Cheung Sha
(5)
Urban/ Village
Area
Consists of residential villages, cultivated land, roads, paths, parks, and wasteland in Shui Hau,
Tong Fuk, Cheung Sha, San Shek Wan and Pui O Wan, and artificial slopes at Cheung Sha and
part of the Shek Pik Reservoir.
Ecological value of this habitat is generally considered to be low (4).
Streams Five major stream systems are found, including Shui Hau Stream, Tong Fuk Stream, Cheung
Sha Stream, San Shek Wan Stream and Pui O Stream. Tong Fuk and Pui O Streams are
identified as Ecological Important Streams by the AFCD.
One rare plant species, Ceratopteris thalictroides, identified near a seasonal streams in
Cheung Sha (5)
Other natural streams can be found near San Shek Wan and Cheung Sha. Five species of
conservation importance identified which is the endemic Romer’s Tree Frog Liuixalus romeri
(found near Cheung Sha), Short-legged Toad Xenophrys brachykolos (found near Cheung Sha),
Chinese Cobra Naja atra (found near Cheung Sha), Lesser Spiny Frog Paa exilispinosa and
the Hong Kong Newt Paramesotriton hongkongensis (found near Pak Kung Au) (3) (5),. The
toads Leptolalax pelodytoides and Megophrys brachykolos were also reported previously near
Cheung Sha.
Four fish species of conservation importance within stream habitat of Pui O Stream, including
Predaceous chub (listed as Vulnerable in China Red Data Book), Beijiang Thick-lipped Barb,
the Philippine Neon Goby and Black-headed Thick-lipped Goby (3)
Marsh Found mainly in the vicinity of villages at Pui O. This habitat was mostly originated by the
abandoned agriculture land and usually located near streams (1). This habitat was invaded with
grasses and weed plants.
Four plant species of conservation importance were recorded at Pui O Marsh, including the
water fern Azolla imbricata, Ceratopteris thalictroides, Marsilea quadrifolia and Salvinia
natans (1).
Notes:
(1) Mott Connell Limited (2001) Op cit
(2) Advisory Council on the Environment Committee Paper NCSC 9/06. Available at:
http://www.epd.gov.hk/epd/english/boards/advisory_council/files/ncsc-paper-06-09.pdf
(3) Mouchel Asia Ltd (2002) Op cit
(4) ERM (2006) Op cit
(5) AECOM (2011) Op cit
(6) AFCD (2005) Biodiversity News Letter Issue 8
Available at: https://www.afcd.gov.hk/tc_chI/publications/publications_con/files/hkbonewsletter8.pdf
Outlying Islands Sewerage Stage 2 –
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The literature review indicates that Mixed Shrubland and Plantation are the dominant
habitat types within the Study Area. Whilst some vegetation and wildlife species of
conservation importance have been documented in the literature (16)
, only very limited
information on general terrestrial wildlife was available within the Study Area.
5.3.3 Baseline Terrestrial Ecological Survey
Findings of the literature review suggest that only limited up-to-date baseline information
on the terrestrial ecological characters of the Study Area is available. Terrestrial ecological
surveys were conducted to provide up-to-date baseline information for establishing an
updated general ecological profile of the Study Area and describing the characteristics of
each habitat found.
The methodology of the ecological surveys makes reference to the technical guidelines of
ecological assessment in Annex 16 of EIAO-TM, and the related Guidance Notes (GN
7/2010 and GN 10/2010).
As per the requirements of the EIA Study Brief, the recommended terrestrial ecological
field surveys were undertaken with a duration of six months covering the wet season
(Table 5.3).
Table 5.3 – Baseline Survey Dates Ecological Survey 2010 2013 2014
(1) 2016
(2)
May Jun Jul Aug Sep Oct Nov July Sep Sep Jul Aug
Habitat Mapping and
Vegetation
Avifauna (Day)
Avifauna (Night)
Terrestrial Mammal (Day)
Terrestrial Mammal (Night)
Bat survey (Dusk)
Herpetofauna (Day)
Herpetofauna (Night)
Dragonflies & Butterflies
Aquatic fauna
Intertidal Fauna
Subtidal Fauna
Notes:
(1) Design changes n the sewerage scheme was made in year 2014, subsequently a site-specific ecological survey was carried
out during September 2014 to provide up-to-date ecological information of the project elements with design changes,
including Tong Fuk SPS, Cheung Sha SPS, San Shek Wan SPS (Proposed & Alternative Sites), San Shek Wan STW and
Pui O SPS.
(2) A verification survey was also conducted in 2016 to provide supplementary information on the existing condition of marine
ecological habitats and freshwater aquatic assemblages. Detailed survey findings of verification survey are presented in
Annex 5C.
The duration for the survey was well covered to ensure that the field data obtained are
representative. The terrestrial ecological surveys included:
(16) Mouchel Asia Ltd (2002) Op cit
Outlying Islands Sewerage Stage 2 –
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5-7 B&V / ERM
Habitat and Vegetation Surveys; and
Wildlife Surveys (including terrestrial mammal, avifauna, herpetofauna, butterflies
and odonates and freshwater aquatic assemblages).
Figure 5.3 shows the terrestrial ecology sampling points and survey transects within the
Study Area. Methodology of the baseline ecological surveys is presented in Annex 5A.
Results of the terrestrial ecological surveys are summarized below.
Habitat & Vegetation Survey
Habitats recorded within the Study Area include Fung Shui woodland, mixed woodland,
plantation, shrubland-grassland, cultivated land, marsh, stream/channel,
urbanised/disturbed area and coastal habitats including mangrove, sandflat, rocky shore
and sandy shore which are discussed in detail under Marine Ecology (Figures 5.4 and 5.5).
Table 5.4 summarized the number of plant species recorded in, and total area occupied by
each habitat in the Study Area, and full list of recorded plant species is presented in Annex-
5B-1. A total of 376 plant species were recorded within the Study Area, 261 of which are
natives while 110 are exotics (Table A1 of Annex 5B-1). Most species recorded are
common species and six are restricted. Four plant species, Araucaria heterophylla, Dypsis
lutescens, Dimocarpus longan, and Gnetum luofuense, are categorized as near threatened
or vulnerable under IUCN Red List; however Araucaria heterophylla, Dypsis lutescens,
Dimocarpus longan are common species in cultivation horticulture, thus the recorded
individuals are considered to be cultivated by local villagers or for landscape purpose.
Gnetum luofuense is commonly found entangling large trees in woodlands and is
considered fairly common in Hong Kong. Two recorded species, Aquilaria sinensis and
Artocarpus hypargyreus, are common/ very common and three species (Aquilaria sinensis,
Pavetta hongkongensis, Artocarpus hypargyreus) protected under local or mainland
regulations were recorded (Figures 5.4a-m). Recorded in the marsh, Water Shamrock
Marsilea quadrifolia are considered very rare and Salvinia natans are considered rare in
Hong Kong. Although Lagerstroemia speciosa is protected under Cap. 96, it is widely
planted in Hong Kong’s countryside as ornamental trees and thus not considered as species
of conservation importance.
Within the Project Site, a total of 206 plant species were recorded; all of which are
common species, except for one protected species recorded at San Shek Wan STW and
San Shek Wan SPS Alternative Site (Table A2 of Annex 5B). The proposed sewers and
rising mains would mainly be laid under existing roads and paths which are void of
vegetation. Habitat descriptions of each proposed pumping station/sewage treatment
works are summarised in Table 5.5.
Table 5.4 – Plant Species Number Recorded within Each Habitat of the Study Area Habitat Number of Plant Species Total Area within the Study Area (ha)
Terrestrial
Mixed Woodland 146 305.5
Fung Shui Woodland 97 2.9
Plantation 110 163.9
Shrubland-grassland 94 609.4
Cultivated Land 48 5.8
Marsh 61 18.4
Stream/Channel 32 20.4
Urbanised/Disturbed Area 112 105.1
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-8 B&V / ERM
Habitat Number of Plant Species Total Area within the Study Area (ha)
Coastal
Mangrove 10 2.9
Rocky Shore 19 3.6
Sandy Shore 18 9.6
Sandflat - 24.0
Table 5.5 – Habitats Recorded within Each Sewage Pumping Station (SPS)/ Sewage
Treatment Works (STW)
SPS/STW Habitats
Proposed Site
Pui O Urbanised/ disturbed area, shrubland/grassland and plantation
San Shek Wan STW Urbanised/ disturbed area and mixed woodland
San Shek Wan Mixed Woodland
Cheung Sha Cultivated Land
Cheung Fu Street Plantation
Tong Fuk Shrubland-grassland,drainage,urbanised/ disturbed Area
Shui Hau Plantation
Alternative Site
San Shek Wan Mixed woodland
Mixed Woodland and Fung Shui Woodland
Mixed woodland was mainly found along stream ravines, at sheltered foothills and behind
sandy or rocky shores (Figure 5.4). The mixed woodlands were mostly young in nature
with a canopy height of 5-12m and dominated by a mixture of native pioneer species
including Schefflera heptaphylla, Sapium sebiferum, Claoxylon indicum, Zanthoxylum
avicennae, Alangium chinense and Celtis sinensis, backshore species including Hibiscus
tiliaceus and Pandanus tectorius and planted species including Acacia confusa and
Dimocarpus longan. The understorey was densely vegetated and dominated by a variety
of tree, shrub and herb species including Litsea glutinosa, Psychotria asiatica, Litsea
rotundifolia, and Liriope spicata.
The oldest woodlands were the Fung Shui woodlands located behind Shui Hau and Tong
Fuk. These woodlands were dominated by native tree species such as Aquilaria sinensis,
Schefflera heptaphylla, Ficus variegata, Cinnamomum camphora and Aporusa dioica.
Mature fruit trees including Dimocarpus longan, Litchi chinensis, and Clausena lansium
were not uncommon in these Fung Shui woodlands. Canopy species reached a height of 8-
14m and some trees of considerable sizes were found. The understorey was densely
vegetated and dominated by woody species including Litsea rotundifolia, Psychotria
asiatica, Ardisia quinquegona and seedlings of canopy species such as Schefflera
heptaphylla and Dimocarpus longan.
There were a total of 146 plant species recorded within the mixed woodland and 97 plant
species recorded within the Fung Shui woodland (Table A1 of Annex 5B). Two plant
species of conservation importance, Incense Tree Aquilaria sinensis and Hong Kong
Pavetta Pavetta hongkongensis were recorded.
Incense Tree is a common tree in Hong Kong but is listed in Protection of Endangered
Species of Animals and Plants Ordinance (Cap 586). It is also listed as a Category II
protected plant in China, in the List of Wild Plants under State Protection and is listed as
‘vulnerable’ by both the China Plant Red Data Book and by IUCN (2015). It is frequently
found in the Study Area and within the footprint of San Shek Wan SPS Alternative Site.
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Hong Kong Pavetta is a common understory species found in woodland habitat in Hong
Kong, but it is protected under Forests and Countryside Ordinance Cap. 96.
Plantation
Plantation was located mainly along roadsides, near developed areas and above catchwater
(Figure 5.4). Most trees were exotic species, including Acacia confusa, Casuarina
equisetifolia and Pinus elliotii. A number of native tree, shrub and herb species had
colonized the understorey, but at a lower density and diversity than in the understory of the
mixed woodland. Understorey of some plantation patches were also cleared regularly as a
maintenance practice and therefore with few species established. Despite its tall canopy
and rapid growth, the plantation remained relatively simple in structure, was immature and
lacked diversity. A total of 110 species was recorded in plantation habitat, in which one
plant species of conservation importance, Silver-back Artocarpus Artocarpus hypargyreus,
was recorded. The locally common Silver-back Artocarpus is not listed under any local or
mainland legislation, but is classified as vulnerable in the IUCN Red Data List since 1998 (17)
. Silver-back Artocarpus is Near Threatened (NT) in China and is also recorded in
China Plant Red Data Book and Illustration of Rare and Endangered Plants in Guangdong
Province (18)
.
Shrubland-grassland
Shrubland-grassland dominated most of the exposed hillsides within the Study Area
(Figure 5.4). Vegetation cover of this habitat was fairly shrubby, some reaching a height
of 3-5 m, although in a few places it was formed by prolonged abandonment of cultivated
land or maintained by hill fires during the grave sweeping festivals, which interrupt the
natural succession of vegetation. Shrubland-grassland was dominated by a variety of tree
and shrub species including Sapium sebiferum, Aporusa dioica, Claoxylon indicum,
Rhodomyrtus tomentosa and the fern species Dicranopteris pedata. Exotic tree species
were also planted along some trails on Shrubland-grassland habitats to speed up succession.
In total 94 plant species were found during the surveys within Shrubland-grassland.
Cultivated Land
Patches of cultivated land were scattered near marshes, villages and on hillsides throughout
the Study Area (Figure 5.4). It was composed of tree nursery, orchard, and vegetable
fields. Most of the cultivated lands are semi-active or abandoned during the survey period.
A total of 48 plant species were recorded.
Marsh
Marshes were mostly recorded at the lowland area of Pui O and Shui Hau near the estuary
(Figure 5.4l). It was formed after abandonment of cultivated land and permanently fed by
brackish water. Some marshes were degraded due to development which disturbed or
encroached the marshes. Plant species recorded include remnants of crops such as
Colocasia esculenta, wetland dependent species including Cyclosorus interruptus,
Marsilea quadrifolia, Salvinia natans, pioneer native tree species including Sapium
sebiferum, Ficus hispida, grass species including Panicum repens, Paspalum paspaloides,
and backshore vegetation including Clerodendrum inerme and Excoecaria agallocha. A
(17) IUCN Red List (2014). Available from: http://www.iucnredlist.org/details/32383/0
(18) Hu QM, Wu TL, Xia NH, Xing FW, Lai CCP & Yip KL (2003) Rare and Precious Plants of Hong Kong. AFCD.
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total of 61 plant species were recorded. Among these, Water Shamrock Marsilea
quadrifolia are considered very rare and Salvinia natans are considered rare in Hong Kong
(Xing et al. 2000).
Stream/Channel
Five major streams, referred to as Pui O Stream, San Shek Wan Stream, Cheung Sha
Stream, Tong Fuk Stream and Shui Hau Stream, were recorded within the Study Area
(Figure 5.4). Two streams, Pui O Stream and Tong Fuk Stream, were considered as
Ecologically Important Stream (EIS). The flows at the upper courses of these streams are
intercepted by the catchwater (which is labelled as “channel” due to its concrete nature).
The middle courses are fairly natural and embraced mainly by mixed woodland and
shrubland-grassland. The lower courses are subject to different levels of modification as
they pass under roads and through villages and cultivated land before reaching the sea. A
total of 32 plant species were recorded, including riparian species (e.g. Cleistocalyx
nervosum, Sterculia lanceolata) and typical vegetation found in other habitats which lie
along the streams (e.g. mangrove species at the estuary and woodland species at the ravine).
Urbanised/Disturbed Area
Road, villages, residential areas, recreational facilities, prison and other built-up area
mainly constitute urbanised/disturbed habitats. Species recorded are mainly exotic species
planted for landscaping purposes. A total of 112 plant species were recorded.
Habitats in Coastal Area
Habitats in coastal area include mangrove, sandflat, rocky shore and sandy shore. Their
locations within the Study Area are shown on Figure 5.4 and detailed description of the
coastal habitats is provided in Section 5.3.2 ‘Habitats in Coastal Area’.
Wildlife Survey
Avifauna
A total of 44 species of birds were recorded within the Study Area (Table B1 of Annex 5B).
Most are common in Hong Kong.
Bird abundance and species richness were low in stream/channel, shrubland/grassland and
cultivated land and Fung Shui woodland, low to moderate in marsh, mixed woodland,
plantation and urbanised/ disturbed area.
Five species were considered of conservation importance. These included Reef Egret
Egretta sacra, Black Kite Milvus migrans, Collared Scops Owl Otus lettia, Greater Coucal
Centropus sinensis and Hwamei Garrulax canorus. All except Hwamei are Class 2
Protected Animal of PRC. Black Kite, Collared Scops Owl and Hwamei are listed in
Appendix 2 of CITES.
Reef Egrets were recorded from sandy/ rocky shore within the Study Area. This species is
common and widespread in Hong Kong and mainly occurs in rocky shores (Viney et al.
2005).
Black Kites were soaring above mixed woodland, shrubland/grassland within the Study
Area. This is a common resident in Hong Kong and occurs in many types of habitats.
Outlying Islands Sewerage Stage 2 –
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Collared Scops Owls were recorded from plantations within the Study Area. This species
is a common resident in Hong Kong and widely found in woodlands.
Greater Coucal was recorded from plantation, urbanised/disturbed, shrubland/grassland
within the Study Area. This is a common resident in Hong Kong and occurs in many types
of habitats.
Hwamei were recorded from shrubland/grassland within the Study Area. This species is a
common resident in Hong Kong and mainly found in hillsides covered by thick shrublands.
Terrestrial Mammals
A total of eight species of mammals were recorded within the Study Area (Table C1 of
Annex 5B)). All are common in Hong Kong. Japanese Pipistrelle Pipistrellus abramus is
considered of conservation importance.
Japanese Pipistrelle was recorded from urbanised/disturbed area, mixed woodland,
cultivated land and plantation. This species is protected under Cap. 170 Wild Animals
Protection Ordinance (WAPO). Japanese Pipistrelle is the commonest bat species of
Hong Kong. This species forages in many types of habitats, including urban areas.
Herpetofauna
A total of seven species of amphibians were recorded within the Study Area (Table C1 of
Annex 5B). All are common in Hong Kong. Romer’s Tree Frog Liuixalus romeri, which
was previously found in a plantation area near Cheung Sha (2)
, was not recorded during the
baseline surveys and it was not found within the Project Site.
Chinese Bullfrog Hoplobatrachus chinensis (Figure 5.6) is considered to be of
conservation importance. This species is Class 2 Protected Animal of PRC. Chinese
Bullfrog was recorded from Pui O Marsh. The observed individuals were mostly froglets.
This species is fairly common in Hong Kong and mainly inhabits cultivated lands, ponds,
rivers and marshes.
A total of nine species of reptiles were recorded within the Study Area. All are common in
Hong Kong.
Copperhead Racer Elaphe radiata (Figure 5.6) is considered to be of conservation
importance. This species is classified as “endangered” by China Red Data Book.
Copperhead Racer was recorded from mixed woodland, plantation, shrubland/grassland
within the Study Area. This species is common in Hong Kong and occurs in many types of
habitats, including woodland edge, grassland, shrubland.
Butterflies & Odonates
A total of 27 species of dragonfly were recorded within the Study Area (Table D1 of Annex
5B). All are common in Hong Kong. No recorded species was considered to be of
conservation importance.
Abundance and species richness of dragonfly were very low in shrubland/grassland,
stream/channel and urbanised/disturbed area, low in Fung Shui Woodland and cultivated
land, and low to moderate in plantation, mixed woodland, and marsh.
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A total of 40 species of butterfly were recorded within the Study Area (Table E1 of Annex
5B). Most are common in Hong Kong. Indian Fritillary Argyreus hyperbius and Blue
Pansy Junonia orithya are uncommon in Hong Kong. No recorded species was considered
to be of conservation importance.
Abundance and species richness of butterfly were low in cultivated land, marsh,
stream/channel and Fung Shui woodland, and low to moderate in shrubland/grassland,
mixed woodland, plantation and urbanised/disturbed.
Freshwater Aquatic Assemblages Survey
A total of 54 species of freshwater aquatic fauna were recorded within the Study Area,
including 43 species of fish, six species of crustaceans, three species of insects and two
species of snails (Table F of Annex 5B). Among them, one fish species was considered
“Endangered” by IUCN (Japanese eel Anguilla japonica), one species was considered
‘Vulnerable’ in China Red Data Book (Predaceous Chub Parazacco spilurus), one species
was considered rare in Hong Kong and was classified as “Near Threatened” by IUCN
(Eye-spotted puffer Takifugu ocellatus). Two species were considered uncommon in Hong
Kong and evaluated as “Lower Risk/Near Threatened” by IUCN (Sleepy goby
Psammogobius biocellatus and Indo-Pacific tropical sand goby Favonigobius reichei).
One species was considered uncommon and evaluated as “Least Concern” by IUCN (Small
snakehead Channa asiatica). Another two species of fish have been evaluated by IUCN
but not considered under threats (Mullet Mugil cephalus – Least Concern (LC), and Grass
puffer Takifugu niphobles – Data Deficient (DD)). For aquatic invertebrates, all are
common in Hong Kong, and no recorded invertebrate species was considered to be of
conservation importance.
A verification survey was also conducted in 2016 to provide supplementary information on
the existing condition of freshwater aquatic assemblages. The freshwater aquatic
assemblages in 2016 reported similar results as the baseline survey conducted in 2010, of
which four species are of conservation importance. Spotty band goby Glossogobius
olivaceus (uncommon species in Hong Kong and classified in IUCN – Least Concern) and
sesarma crab Pseudosesarma patshuni (endemic species to Hong Kong) were the
additional species of conservation importance recorded in the verification survey. Detailed
findings of the verification survey are presented in Annex 5C.
Generally, the flow in these streams was not high even during wet season. The flows in
Pui O Stream and Shui Hau Stream were relatively higher than those in other streams. The
diversity and abundance of aquatic fauna were higher in Pui O Stream, Tong Fuk Stream
and Shui Hau Stream, lower in Cheung Sha Stream, and the lowest in San Shek Wan
Stream. This might be attributed to the lack of lowland estuarine section in San Shek Wan
Stream (its outlet is located at a boulder shore). Pui O Stream has all the five fish species
of conservation concern, and two fish species of conservation concern were recorded in
Tong Fuk Stream.
5.3.4 Marine Ecology
In accordance with the requirements in Clause 3.4.2.2 of the EIA Study Brief, the Study
Area for marine ecology lies within the Southern Water Control Zone (SWCZ) as
designated under the Water Pollution Control Ordinance (Cap 358). The Study Area
covers the entire southern coastline of the Lantau Island and includes the waters off
southern Lantau.
Outlying Islands Sewerage Stage 2 –
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Whilst various marine habitats and species can be found within the broad Study Area, the
immediate vicinity of the marine footprint of the proposed project (i.e. the submarine
outfall extending from San Shek Wan) consists of natural sandy and rocky boulder shores
with relatively shallow water depths (< 5 m). Anthropogenic disturbance is expected to be
minimal at this area, while the further offshore areas experience a higher level of
disturbance through marine traffic and fishing activities.
Baseline conditions for each ecological component of the marine environment of the Study
Area were evaluated based on information from the literature and focused field studies
conducted for the purposes of this EIA. Findings of the literature review and baseline field
surveys of the Study Area is summarised in the following sections.
Literature Review
A literature and recent aerial photograph review were conducted to determine the existing
marine ecological conditions within the Study Area, identify habitat resources and species
of potential conservation importance, and identify potential information gaps in the
baseline conditions of the habitats. The literature reviewed includes:
Porcupine! (19)
;
Hong Kong Biodiversity (20)
;
Revised Concept Plan for Lantau (21)
;
Field guides and published academic literature for marine habitats and fauna of
Hong Kong;
Consultancy Study on Marine Benthic Communities in Hong Kong (Agreement
No. CE 69/2000) (22)
;
A Study of Soft Shore Habitats in Hong Kong for Conservation and Education
Purposes (23)
;
AFCD marine mammal monitoring report (24)
;
EIA Report for Liquefied Natural Gas (LNG) Receiving Terminal and
Associated Facilities (25)
;
EIA Report for Drainage Improvements in Southern Lantau (26)
;
(19) Newsletter of Department of Ecology & Biodiversity, The University of Hong Kong. Issues 1 to 33
(20) AFCD (2010 – 2015) Biodiversity Newsletters. Issues 1 to 23
(21) Lantau Development Task Force (2005) Revised Concept Plan for Lantau
(22) CityU Professional Services Limited (2002) Consultancy Study on Marine Benthic Communities in Hong Kong (Agreement No. CE 69/2000).
Prepared for the Agriculture, Fisheries and Conservation Department (AFCD)
(23) Shin PKS, Cheung SG (2005) A Study of Soft Shore Habitats in Hong Kong for Conservation and Education Purposes: Final Report 2005. ECF
Project 23/99
(24) Hong Kong Cetacean Research Project (2015) Monitoring of Marine Mammals in Hong Kong Waters – Data Collection (2014-2015). Available at
https://www.afcd.gov.hk/english/conservation/con_mar/con_mar_chi/con_mar_chi_chi/files/Final_Report_201415.pdf. Prepared for AFCD
(25) ERM (2006) Op cit
(26) Maunsell (2005) Op cit
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
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EIA Report for Improvement to Tung Chung Road Between Lung Tseng Tau
and Cheung Sha (27)
;
EIA Report for 132 kV Supply Circuit from Pui O via Chi Ma Wan Peninsula
via Sea Crossing towards Cheung Chau (28)
;
EIA Report for Engineering Investigation and Environmental Studies for
Integrated Waste Management Facilities Phase 1 – Feasibility Study (29)
;
Project Profile for Asia-America Gateway (AAG) Cable Network, South
Lantau (30)
; and
Project Profile for Telecommunication Installation at Lot 591SA in DD328,
Tong Fuk, South Lantau Coast and the Associated Cable Landing Work in Tong
Fuk, South Lantau for the North Asia Cable (NAC) Fibre Optic Submarine
Cable System (31)
.
Findings of the literature review of the Study Area is summarised in the following sections.
Areas of Ecological Importance / Interest
Within the Study Area, a number of ecologically important / sensitive sites and habitats,
including natural mudflats and mangroves in Shui Hau Wan and Pui O, and horseshoe crab
nursery ground in Shui Hau Wan, are identified under the Revised Concept Plan for Lantau.
These habitats fall within the CPA.
Proposed Shui Hau Wan SSSI
Shui Hau Wan is a large natural sand/ mudflat (>10 ha) in Hong Kong, and is identified as
an Extremely Important soft shore habitat for conservation and education purposes in Hong
Kong (32)
. It is also one of the confirmed nursery sites for horseshoe crabs in recent
years (33) (34)
, and based on the abundance of juveniles, Shui Hau Wan is identified as the
key nursery ground for Tachypleus tridentatus (35) (36)
. The horseshoe crab nursery ground
at Shui Hau Wan is also a proposed Site of Special Scientific Interest (SSSI).
Marine Mammals
Two resident marine mammals are found in Hong Kong: the Indo-Pacific humpback
dolphin (Sousa chinensis, locally called Chinese White Dolphin) and the finless porpoise
(27) Mouchel Asia Ltd (2002) Op cit
(28) Mott Connell Limited (2001) Op cit
(29) AECOM (2011) Engineering Investigation and Environmental Studies for Integrated Waste Management Facilities Phase 1 – Feasibility Study.
EIA Report. EIA Registered No. 201/2011.
(30) Atkins & EGS (2007) Asia-America Gateway (AAG) Cable Network, South Lantau: Project Profile. DIR-160/2007
(31) ERM (2000) Op cit
(32) Shin PKS, Cheung SG (2005) Op cit
(33) Chiu HMC, Morton B (1999) The Biology, Distribution and Status of Horseshoe Crabs, Tachypleus tridentatus and Carcinoscorpius
rotundicauda (Arthropoda: Chelicerata) in Hong Kong: Recommendations for Conservation and Management. Final Report. The Swire Institute
of Marine Science, The University of Hong Kong
(34) Li HY (2008) The Conservation of Horseshoe Crabs in Hong Kong. MPhil Thesis. The City University of Hong Kong
(35) Li HY (2008) Op cit
(36) Carcinoscorpius rotundicauda has not been recorded in Shui Hau Wan (Li 2008)
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
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(Neophocaena phocaenoides) ( 37 )
. Whilst the distribution of Indo-Pacific humpback
dolphins is limited to the western waters of Hong Kong, which are influenced by
freshwater input from the Pearl River (38) (39)
, finless porpoises are common in the waters of
southern and eastern Hong Kong (40)
. Both species have previously been sighted in the
Study Area.
Baseline condition of marine mammal distribution and abundance within the Study Area
has been determined primarily from a review of findings from recent AFCD long-term
marine mammal monitoring (41) (42) (43) (44) (45)
, supplemented by findings from previous
relevant EIAs (46) (47) (48)
. Locations of marine mammal sightings reported in these literature
resources are presented in Figure 5.7. The data presented are collected between 2000 and
2015.
The key finding of the literature review is that, in recent years, Chinese White Dolphins
were frequently sighted in to the west and south of Lantau Island where the west coast of
Lantau was identified as the most important dolphin habitat (49)
. Fewer dolphin sightings
were observed in Shek Pik, north of Siu A Chau and southeast of Tai A Chau (Figure 5.7).
During the 12-month survey period between 2014 and 2015, only three sightings were
recorded at Southeast Lantau with the lowest mean group size of 1.0. Southeast Lantau
waters (i.e. across Shui Hau Wan and the Chi Ma Wan Peninsula and near Shek Kwu
Chau), therefore, represent only marginal habitat for Chinese White Dolphins. On the
contrary, the usage at West and Southwest Lantau of Chinese White Dolphins were
increased in the AFCD long term monitoring during April 2014 to March 2015 (50)
. The
West Lantau and Southwest Lantau were still the frequent occurrence waters of Chinese
White Dolphins, particularly near Tai O Peninsula, Kai Kung Shan, Peaked Hill, around
Fan Lau and Kau Ling Chung.
Important porpoise habitats were located to the south of Tai A Chau, southwest of Shek
Kwu Chau, south of Cheung Chau, and the waters between Shek Kwu Chau and the Soko
Islands
Finless porpoises were frequently sighted in Southeast Lantau, particularly south of Tai A
Chau, and between Shek Kwu Chau and Soko Islands. Between 2014 and 2015, the
porpoise groups were mainly sighted at south of Tai A Chau, southwest of Shek Kwu Chau,
south of Cheung Chau, and the waters between Shek Kwu Chau and the Soko Islands as
(37) Jefferson TA, Hung SK (2007) An updated, annotated checklist of the marine mammals of Hong Kong. Mammalia 2007: 105–114
(38) Parsons ECM (1998) The behaviour of Hong Kong’s resident cetaceans: the Indo-Pacific humpbacked dolphin and the finless porpoise. Aquatic
Mammals 24: 91–110
(39) Jefferson TA (2000) Population biology of the Indo-Pacific hump-backed dolphin in Hong Kong waters. Wildlife Monographs 144: 1-65
(40) Jefferson TA, Hung SK (2007) Op cit
(41) Chinese White Dolphin data from 2003-2008, finless porpoise data from 2004-2008. Hong Kong Cetacean Research Project (2009) Op cit
(42) Monitoring of marine mammals in Hong Kong water - Data collection (2009-10). Hong Kong Cetacean Research Project (2010).
(43) Monitoring of marine mammals in Hong Kong waters - Data collection (2010-11). Hong Kong Cetacean Project. (2011).
(44) Finless porpoise conservation. http://www.afcd.gov.hk/english/conservation/con_mar/con_mar_fin/con_mar_fin_fin/con_mar_fin_fin.html
(last visited on 3 Ocotber 2011). Agricultural, Fisheries and Conservation Department, Hong Kong.
(45) Hung SK (2015) Monitoring on Marine Mammals in Hong Kong Waters (2014 – 2015)
(46) ERM (2006) Op cit
(47) Mott Connell Limited (2001) Op cit
(48) AECOM (2011) Op cit
(49) Hung SK (2015) Op cit
(50) Hung SK (2015) Op cit
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per the monitoring results between 2014 and 2015 (51)
(Figure 5.7). From survey between
2014 and 2015, the mean group size (2.7±2.57) was similar to the ones in previous
monitoring periods, but was slightly higher than the one in 2013 – 2014. Recent
monitoring results showed that inshore waters (i.e. Pui O Wan) is no longer utilized by
finless porpoises which was an area once known to be an important habitat for porpoises.
Specifically, the number of sightings and abundance of the two marine mammals in waters
near the proposed outfall location, i.e. off San Shek Wan around Cheung Sha and Pui O,
are low in comparison to other marine mammal habitats of Hong Kong. These waters are,
therefore, not considered to represent key habitats for both species, and the ecological
value of the waters within the immediate area of the proposed outfall is predicted to be low (52)
.
Intertidal & Subtidal Assemblages
Focused field surveys have been conducted at Shek Pik, Shui Hau Wan and Pui O Wan as
part of the EIA and projects mentioned above (Figure 5.8). The most recent surveys
completed were, however, undertaken in March 2006 around Shek Pik and January 2010
around Cheung Sha, and no recent field surveys have been conducted near the proposed
project site at San Shek Wan and Pui O (Table 5.6).
Table 5.6 – Survey Efforts for Previous Relevant Projects Project Major Survey
Location
Habitats Field Survey Period
Consultancy Study on Marine Benthic Communities in
Hong Kong
Off Lo Kei Wan,
Cheung Sha and Yi
Long Wan
Subtidal soft-bottom June – December 2001
(wet and dry seasons)
A Study of Soft Shore Habitats in Hong Kong for
Conservation and Education Purposes
Shui Hau Wan Intertidal soft-bottom June – December 2002
(wet and dry seasons)
Liquefied Natural Gas (LNG) Receiving Terminal and
Associated Facilities
Shek Pik Intertidal hard-and soft-
bottom
August 2005 and March
2006 (wet and dry
seasons)
Improvement to Tung Chung Road from Lung Tseng
Tau to Cheung Sha
Pui O Wan Intertidal hard- and
soft-bottom
March 2002
132 kV Supply Circuit from Pui O via Chi Ma Wan
Peninsula via Sea Crossing towards Cheung Chau
Pui O and Chi Ma Wan Intertidal hard- and
soft-bottom, subtidal
hard-bottom
October – December
2000
Engineering Investigation and Environmental Studies
for Integrated Waste Management Facilities Phase 1 –
Feasibility Study
Cheung Sha Intertidal hard- and
soft-bottom, subtidal
hard- and soft-bottom
August 2009 – January
2010
Telecommunication Installation at Lot 591SA in
DD328, Tong Fuk, South Lantau Coast and the
Associated Cable Landing Work in Tong Fuk, South
Lantau for the North Asia Cable (NAC) Fibre Optic
Submarine Cable System
Tong Fuk Intertidal hard- and
soft-bottom, subtidal
hard-bottom
February 2000
Asia-America Gateway (AAG) Cable Network, South
Lantau
Tong Fuk Subtidal hard-bottom September 2007
Table 5.7 present the major intertidal and subtidal habitats and associated assemblages
identified within the Study Area based on the above previous field surveys.
(51) Hung SK (2015) Op cit
(52) Mott Connell Limited (2001) Op cit
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Table 5.7 – Major Marine Habitats identified within the Study Area (Information based on
Literature Review) Habitat Description
Intertidal hard-
bottom
Expected to support assemblages typical of similar shores in Hong Kong.
Species associated with this habitat are usually common and widespread with no notable species of
conservation importance.
Generally considered to be of low to moderate ecological value, dependent on size and naturalness.
Intertidal soft-
bottom
Natural intertidal mudflats and mangroves in Shui Hau Wan and Pui O, and horseshoe crab nursery ground in
Shui Hau Wan, are identified as habitats with high ecological and conservation value.
Bathing beaches at Tong Fuk, Cheung Sha and Pui O are generally devoid of assemblages due to
anthropogenic and natural disturbances and are thus considered as of low ecological value.
Other natural sandy/ boulder shores of south Lantau, e.g. at Shek Pik and Pui O Wan, are generally
considered to be of low ecological value (1) (2) (3)
Subtidal hard-
bottom
The SWCZ is influenced by the Pearl River Estuary and represents sub-optimal conditions for coral
recruitment and survival. It is thus anticipated that corals are much less abundant and diverse in this area
than in other parts of Hong Kong, and only scattered, isolated individuals/ colonies are expected to occur.
Previous surveys reported typical assemblages of sponges, bryozoan, mussels/ oysters, barnacles and urchins
at Chi Ma Wan (Tai Long Wan) (1), with a few isolated colonies of octocoral and ahermatypic corals
(gorgonian Euplexaura spp., soft coral Dendronephthya sp. and ahermatypic coral Tubastrea sp.) and small,
scattered and encrusting colonies of the hard corals Psammocora superficialis, Cyphastrea serailia, Porites
lobata, Goniopora stutchburyi and Oulastrea crispata recorded. One gorgonian species (5) and one hard coral
species (O. crispata) (6) were recorded in Tong Fuk previously.
Habitats in this part of Hong Kong are generally considered to be of low ecological value (1) (7).
Subtidal soft-
bottom
Generally dominated by small, short-lived polychaete and crustacean species which are common and
widespread benthos of Hong Kong seabed.
Species of conservation importance, e.g. amphioxus species, have not been reported in this part of Lantau.
Benthos assemblages off Cheung Sha was considered to be of low diversity and low ecological value (7)
Benthos assemblages off Lo Kei Wan, Cheung Sha and Yi Long Wan were considered to be of moderate to
high species diversity (4)
Generally considered to be of low to moderate ecological value, dependent on species diversity and rarity.
Notes:
(1) Mott Connell Limited (2001) Op cit
(2) Mouchel Asia Ltd (2002) Op cit
(3) ERM (2006) Op cit
(4) CityU Professional Services Limited (2002) Op cit
(5) ERM (2000) Op cit
(6) Atkins & EGS (2007) Op cit
(7) AECOM (2011) Op cit
The literature review indicates that species of conservation importance are generally not
anticipated in the Study Area, with exceptions at the mangroves and intertidal mudflats at
Shui Hau Wan and Pui O which are regarded as habitats with high ecological and
conservation value. Intertidal and subtidal assemblages of the Study Area are expected to be
typical of similar habitats in this part of Hong Kong.
Baseline Marine Ecological Survey
Findings of the literature review suggest that some baseline information on the marine
ecological characters of the Study Area is available. Taking into account the marine footprint
of this Project (i.e. the submarine outfall extending from San Shek Wan) and the marine
ecological sensitive receivers along the South Lantau coastline (i.e. Subtidal Hard Bottom
Habitats with corals, Sandflat, Horseshoe Crabs), the marine baseline ecological surveys were
focused around intertidal and subtidal habitats off the South Lantau coast to provide up-to-
date baseline information for establishing an updated general ecological profile of the Study
Area and describing the characteristics of each habitat found.
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The methodology of the ecological surveys makes reference to the technical guidelines of
ecological assessment in Annex 16 of EIAO-TM, and the related Guidance Notes (GN 7/2010
and GN 10/2010).
As per the requirements of the EIA Study Brief, the recommended marine ecological field
surveys were undertaken with a duration of six months covering the wet season (May to
November 2010) (Table 5.3). A verification survey was also conducted in 2016 to provide
supplementary information on the existing condition of marine ecological habitats. In general,
the survey findings in 2016 reported similar results as the baseline survey conducted in 2010.
Detailed survey findings of verification survey are presented in Annex 5C.
The duration for the survey was well covered to ensure that the field data obtained are
representative. The marine ecological surveys included:
Intertidal Survey;
Subtidal Coral Survey; and
Subtidal Benthos Survey.
Sufficient up-to-date baseline information on marine mammal of the Study Area is present in
the literature. Marine mammal baseline surveys are thus not considered necessary.
Figure 5.3 shows the marine survey transects and subtidal benthos survey points within the
Study Area. Methodology of the baseline ecological surveys is presented in Annex 5A.
Results of the marine ecological surveys are summarized below.
Habitats in Coastal Area
Habitats in coastal area include mangrove, sandflat, rocky shore and sandy shore. Their
locations within the Study Area are shown in Figures 5.4a-m and detailed description of the
coastal habitats is provided below.
Mangrove
Patches of mangrove were recorded at the estuary of Pui O Stream and Shui Hau Stream. A
total of 10 plant species were recorded in mangrove habitat including true mangrove species,
mangrove associates and backshore species, ie Avicennia marina, Aegiceras corniculatum,
Kandelia obovata, Zoysia sinica, Clerodendrum inerme and Pandanus tectorius. Among the
recorded species, Zoysia sinica is listed as a Category II protected plant in China and under
the List of Wild Plants under State Protection (Part 1). However, this species is considered
fairly common in Hong Kong.
Sandflat
Sandflat within the Study Area is located at the estuary of Shui Hau Stream which is a
proposed SSSI and considered to be a possible spawning and nursery ground for horseshoe
crabs. Three Horseshoe crabs juveniles (i.e. Tachypleus tridentatus) were recorded during
intertidal qualitative spot-checks. A total of 16 intertidal epifauna and infauna species were
recorded.
Sandy Shore
Outlying Islands Sewerage Stage 2 –
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Sandy shores within the Study Area include gazetted beaches at Cheung Sha and Tong Fuk.
Backshore species including Vitex rotundifolia, Ipomoea pes-caprae, Pandanus tectorius and
Hibiscus tiliaceus formed a narrow belt at the rear side of sandy shores. A total of 18 plant
species were recorded at the backshore vegetated areas.
Rocky shore
Rocky shores within the Study Area are generally present between the gazetted beached at
Tong Fuk, Cheung Sha and Pui O. Species recorded at rock shore are common and typical
fauna of this type of habitat along the coast, namely Mollusca, Arthopoda and Echinodermata.
Intertidal Survey
Intertidal surveys consisted of qualitative walk-through surveys and quantitative transect
surveys along four selected survey locations within the project site (Figure 5.3). A total of 41
intertidal fauna were recorded during intertidal surveys in the surveyed area, from both walk
through surveys and transect surveys (Table 5.8). The majority of the intertidal fauna was
species from Mollusca and Crustacea.
Qualitative walk-through surveys include the accessible shorelines along Shui Hau Wan, San
Shek Wan and Pui O Wan. Active search of horseshoe crabs were conducted in particular
from July to October during the active period of juveniles. Three Horseshoe crab juveniles
(i.e. Tachypleus tridentatus) were recorded in Shui Hau Wan Sandflat but not in other
surveyed area. Except Horseshoe crab juveniles, there was no other intertidal species of
conservation concern found.
Four intertidal habitats were located within the surveyed area. Locations I-1, I-2 and I-3 are
rocky shores / boulder shores, while Location I-4 is a sandflat. Results of line transect
surveys are summarized in Annex 5B.
Table 5.8 – Intertidal fauna recorded in the Study Area
Phylum/Class Species
Platyhelminthes Flatworm (Class Tubellaria)
Bivalvia Anomalocardia flexuosa
Barbatia virescens
Circe scripta
Meretrix meretrix
Saccostrea cucullata
Solen strictus
Tapes sp.
Gastropoda Batillaria sp.
Cellana sp.
Cerithidea sp.
Chlorostoma argyrostoma
Clithon sp.
Echinolittorina radiata
Echinolittorina trochoides
Lunella coronata
Monodonta labio
Nassarius festivus
Nerita sp.
Siphonaria sp.
Thais clavigera
Arthropoda Tachypleus tridnetatus
Crustacea Ligia exotica
Capitulum mitella
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Phylum/Class Species
Alpheus lobidens
Metapenaeus sp.
Petrolishthes japonicus
Hermit crab (Order Anomura)
Macrophthalmus sp.
Ocypode creatophthalmus
Scopimera sp.
Uca lactea
Uca arcuata
Gaetice depressus
Perisesarma bidens
Epixanthus frontalis
Philyra carinata
Scylla paramamosain
Mictyris sp.
Echinodermata Holothuria leucospilota
Choradata Gobies (Family Gobiidae)
A total of 18 intertidal faunal species were found in Locations I-1, I-2 and I-3. Species
composition of Locations I-1, I-2 and I-3 were almost the same except Gobies (Chordata) was
absent in Location I-3. 11 species from Mollusca (Cellana sp., Siphonaria sp., Monodonta
labio, Lunella coronata, Echinolittorina radiata, Echinolittorina malaccana, Thais clavigera,
Saccostrea cucullata, Barbatia virescens, Nerita sp., Chlorostoma argyrostoma), five species
from Arthropoda (Ligia exotica, Capitulum mitella, Petrolishthes japonicus, Epixanthus
frontalis, Gaetice depressus), and one species from Echinodermata (Holothuria leucospilota)
were found in the rocky / boulder shores. All of these species are common and typical fauna
of this type of habitat (Lai et al. 2006). No recorded species was considered to be of
conservation importance.
A total of 16 species including both epifauna and infauna were found in Location I-4. 10
species from Mollusca (Anomalocardia flexuosa, Batillaria sp., Cerithidea sp., Circe scripta,
Clithon sp., Lunella coronata, Meretrix meretrix, Nassarius festivus, Nerita sp. and Tapes sp.),
five species from Arthropoda (Hermit crab, Macrophthalmus sp., Metapenaeus sp., Alpheus
lobidens and Scopimera sp.) and one from Annelida (i.e. flatworm) were found in the sandflat.
All of these species are common or typical fauna of this type of habitat (Fong et al. 2005). No
recorded species was considered to be of conservation importance.
In general, there were more benthos present in middle and lower intertidal shores in Locations
I-1, I-2 and I-3, but there were fewer benthos in lower intertidal shore for both epifauna and
infauna in Location I-4. Echinolittorina radiata and Saccostrea cucullata were the dominant
species in the rocky / boulder shores, while Batillaria sp. and Cerithidea sp. were the
dominant species in the sandflat. Zonations of benthos were also observed in the Study Area.
For example, the abundance of Cellana sp. increased from higher intertidal zone to lower
intertidal zone, while that of Echinolittorina malaccana decreased from higher to lower
intertidal zone in the rocky / boulder shores. On the other hand, abundance of Batillaria sp.
was the highest in the middle intertidal shore in the sandflat.
Shannon diversity index (H’) and evenness (J) within the Study Area are shown in Table 5.9.
Although the abundance of benthos was the highest in Location I-4, its H’ and J were lower
than Locations I-1, I-2 and I-3. The low H’ and J in Location I-4 were due to the dominant
species Batillaria sp. and Cerithidea sp. with a significantly higher abundance than other
species. On the other hand, evenness of benthos was higher in Locations I-1, I-2 and I-3,
hence the H’ was also higher. Zonation patterns were also observed in the intertidal shore.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-21 B&V / ERM
There were higher H’ in the middle and lower intertidal shores than the higher shores in
Locations I-1, I-2 and I-3, while the H’ of lower intertidal shore was lower in Location I-4.
Horseshoe crab was not recorded during the quantitative transect surveys, but three horseshoe
crab juveniles (Tachypleus tridentatus) were found on the sandflat of Location I-4 during the
qualitative spot checks. During a recent horseshoe crab study (Shin et al. 2007), juveniles
were also recorded in Shui Hau. This suggested that the area is a possible spawning and
nursery ground for horseshoe crabs.
Subtidal Hard-Bottom Habitat
The Study Area is influenced by the Pearl River Estuary which represents sub-optimal
conditions for coral survival and recruitment. It is thus expected that the abundance and
diversity of corals in this area to be less than that in the eastern part of Hong Kong waters
where the water is more oceanic. Only small, isolated and scattered coral colonies which are
more tolerant to sedimentation are expected to occur within the Study Area. Subtidal coral
survey was conducted within the project site and details are presented below:
Subtidal Coral Survey
Dive surveys were performed on 18 and 30 September 2011 in locations near the proposed
outfall alignment and the nearby shorelines. A total of five sites were investigated (Figure
5.3).
Regarding the weather conditions, it was sunny with mild wind, and the underwater visibility
was very low (~ 0.5 m). The water depth in the survey area was shallow, most areas less than
mostly less than 3m, and the maximum depth less than 5m.
D-1, D-2 and D-3 were close to the outfall alignment and D-4 and D-5 were located in the
vicinity. D-1, D-4 and D-5 were natural coastlines while D-2 and D-3 were shallow coastal
waters.
Spot check dives revealed that the seabed at D-2 and D-3 was covered by sandy substrate only.
No subtidal fauna including corals was found in D-2 and D-3. There was no hard substrate in
these two transects available for corals or other epibenthos to colonise.
D-1, D-4 and D-5 were natural rock shores. Common sessile shallow subtidal fauna were
found on the natural rocks including the Rock oyster Saccostrea cucullata and the Green
mussel Perna viridis (Table 5.10). Very low coverage (< 1%) of hard coral Oulastera
crispata was recorded in these three transects, and the colonies of Oulastrea crispata were
small and scattered.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-22 B&V / ERM
Table 5.9 – Shannon diversity index (H’) and evenness (J) of the intertidal benthos survey at different locations
Parameters Intertidal zone
Location I-1 Location I-2 Location I-3 Location I-4
September October September October September October September October
Abundance / m2 High 56 61 53 53 45 45 364 384
No. of species 3 3 3 3 2 2 4 4
H' 0.89 0.75 0.88 0.88 0.69 0.69 0.73 0.73
J 0.81 0.68 0.80 0.80 1.00 1.00 0.53 0.52
Abundance / m2 Middle 97 94 72 99 82 97 444 449
No. of species 11 12 11 11 11 12 8 12
H' 2.21 2.22 2.21 2.25 2.20 2.27 0.76 0.83
J 0.92 0.89 0.92 0.94 0.92 0.91 0.36 0.33
Abundance / m2 Lower 95 118 93 124 94 117 197 196
No. of species 15 12 12 12 12 11 4 5
H' 2.18 1.99 2.02 2.06 2.01 1.93 0.41 0.46
J 0.81 0.80 0.81 0.83 0.81 0.80 0.29 0.29
Abundance / m2 Overall 87 82 80 339
No. of species 18 18 17 16
H' 2.38 2.43 2.35 0.97
J 0.82 0.84 0.85 0.37
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-23 B&V / ERM
In accordance with the findings from spot dive, REA surveys were conducted at the three
transects with hard corals on the natural coastlines, i.e. D-1, D-4 and D-5. The REA transects
were parallel with the shore. The coastlines were mainly covered by large-sized boulders.
Table 5.10 – Subtidal fauna recorded during the Dive survey Common Name Species Commonness
Hard coral Oulastrea crispata Common
Rock oyster Saccostrea cucullata Very common
Green mussel Perna viridis Very common
The ecological attributes and substratum attributes of the REA transects were summarised in
Table 5.11. The areas were considered to be of low ecological value due to the low
percentage cover of a single species of common hard corals, and a lack of species of
conservation value.
Table 5.11 – Ecological Attributes and Substratum Attributes of the Transects Rank D-1 D-4 D-5
Ecological attributes
Hard coral 0.5 0.5 0.5
Octocoral (soft corals and gorgonians) 0 0 0
Black Corals 0 0 0
Dead standing corals 0 0 0
Substratum Attributes
Bedrock/continuous pavement 0 0 0
Boulder Blocks (diam.>50cm) 2 1 4
Boulder Blocks (diam.<50cm) 4 4 2
Rubble 1 2 1
Other 0 0 0
Soft Substrata
Sand 2 2 1
Mud/Silt 0 0 0
* Rank of percentage cover: 0 = None recorded; 0.5 = 1-5%; 1 = 6-10%; 2 = 11-30 %; 3 = 31-50%; 4= 51-75 %; 5
= 76-100%.
While only very low percentage cover of the common hard coral Oulastrea crispata was
found on the shorelines, dive survey confirmed that there was no coral on the majority of the
outfall alignment and the surrounding seabed. A very low percentage cover of hard corals
was found along the nearby natural coastlines, but these scattered coral colonies were a
common species in Hong Kong.
No other soft coral, gorgonian, or black coral was found during the survey. Other marine
lives in the area were of low diversity and were common species in Hong Kong.
Subtidal Soft-Bottom Habitat
Benthos assemblages within the Study Area are generally considered to be of low to moderate
ecological value. Small and short-lived polychaete and crustacean species which are common
and widespread benthos of Hong Kong seabed are the dominant benthic species within the
Study Area. Species of conservation importance, ie Amphioxus species, have not been
recorded in this part of Lantau. Subtidal benthos survey was conducted within the project site
and details are presented below:
Subtidal Benthos Survey
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-24 B&V / ERM
Abundance, number of species, Shannon diversity index (H’), evenness (J) and biomass of
benthos recorded from the four subtidal benthos sampling sites are shown in Table 5.12. A
total of 6,110 individuals from 70 species of benthic organisms were recorded at the four sites
(24 sampling stations, three replicates in each sampling station) within the Study Area (Annex
5B). There were 10 major taxa (Phylum) recorded in the benthic samples. Polychaeta was
the dominant Class across the study sites (over 13 Classes), with 36 species out of 70 in the
benthic samples. No rare species were recorded in the samples. The polychaete
Paraprionospio pinnata was the dominant species and comprised over 67% of the total
abundance. The total abundance was the highest at Location B-4 (total abundance was 2,100),
and its total number of species was also the highest among the four sites but with the lowest
biomass. On the other hand, total abundance was the lowest in Location B-1 (total abundance
was 1,034), which is the closest to the Pui O Wan, but its H’ and biomass were the highest
among the four sites. Species list and corresponding abundance are presented in Annex 5B –
Table L.
Table 5.12 – Abundance, number of species, Shannon diversity index (H’) and evenness (J) of
Benthos Recorded from Location A to D Location A Location B Location C Location D
Abundance 1,034 1,249 1,738 2,100
Number of species 44 50 41 52
H’ 2.51 1.68 1.09 1.41
J 0.66 0.43 0.29 0.36
Biomass (g) 129 38 63 35
The overall species diversity (H’) was moderate to high, and the mean value ranged from 1.09
to 2.51, in which the highest H’ was recorded at Location B-1 which is located nearest to the
Pui O Beach. The lowest H’ was recorded in Location B-3 which is located away from the
Pui O Beach, near Cheung Sha and with deep waters. For the Shannon diversity index (H’), a
value of < 1 indicates low diversity, 1-2 indicates moderate diversity and a value of > 2
indicates higher diversity.
The mean value of the evenness (J) recorded in the four sites ranged from 0.29 to 0.66. The
evenness index reflects how similar the abundance values for each species are within an
assemblage. For example, a value of 1 indicates that all species occur in equal abundance
whereas a value close to zero indicates that one species has very high abundance and the other
species are recorded at very low abundance. The indices indicated that there were limited
number of species of benthic organisms recorded across the sites and these were patchily
distributed.
Evaluation of Ecological Importance
The ecological importance of the habitats and wildlife identified within the Study Area are
evaluated in accordance with the EIAO-TM Annex 8 criteria, and presented in Table 5.13 to
5.24.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-25 B&V / ERM
Table 5.13 – Evaluation of Mixed Woodland and Fung Shui Woodland Criteria Mixed Woodland Fung Shui Woodland
Naturalness Semi-natural dominated by native plants. Semi-natural composed of a mixture of mature exotic and
native plants. Size
Overall size of approximately 305.5 ha. Overall size of approximately 2.9 ha.
Diversity
Moderate diversity of plants (146 species) and
structural complexity, Low to moderate
diversity for bird, butterfly and dragonfly
Moderate diversity of plants (97 species) and structural
complexity.
Low to moderate diversity for bird and butterfly, low
diversity for dragonfly
Rarity
Plant species of conservation importance
included Incense Tree Aquilaria sinensis,
Gnetum luofuense and Hong Kong Pavetta
Pavetta hongkongensis.
Protected fauna species included Japanese
Pipistrelle, Black Kite and Copperhead Racer
Plant species of conservation importance included Incense
Tree Aquilaria sinensis.
No fauna of conservation importance
Re-creatability
It would take more than 20 years for the mixed
woodland to be re-created.
It would take more than 30-40 years for the fung shui
woods to be re-created.
Fragmentation Formed a belt along foothill and ravines. Fairly fragmented
Ecological Linkage Functionally linked to stream in close
proximity.
Functionally linked to mixed woodland in close
proximity.
Potential Value High, becoming mature woodland if given time
and protection from disturbance.
High, becoming mature woodland if given time and
protection from disturbance.
Nursery/ Breeding
Ground
No significant observation, but can provide
breeding habitats for mammals, birds, reptiles
and butterflies
No significant observation, but can provide breeding
habitats for mammals, birds, reptiles and butterflies
Age Moderate (around 20-30 years) based on tree
size, woodland structure and species
composition.
Mature (more than 50 years) based on tree size, woodland
structure and species composition.
Abundance/ Richness of
Wildlife
Low to moderate abundance for bird, butterfly
and dragonfly.
Low to moderate abundance for bird and butterfly, low
abundance for dragonfly.
Overall Ecological
Value
Moderate Moderate to High
Table 5.14 – Evaluation of Plantation Criteria Plantation
Naturalness Semi-natural, canopy dominated by exotic plants but undertorey of some patches colonised by
native species. Size Overall size of approximately 163.9 ha.
Diversity Moderate diversity of plants (110 species)
Low to moderate for bird and butterfly, very low for dragonfly
Rarity Plant species of conservation importance included Silver-back Artocarpus Artocarpus
hypargyreus.
Protected fauna species included Japanese Pipistrelle, Collared Scops Owl, Greater Coucal
and Copperhead Racer.
Re-creatability Habitat characteristics and species composition are easy to recreate. It will take about 10
years for the plantation to be re-created.
Fragmentation Not applicable.
Ecological Linkage Not functionally linked to any highly valued habitat in close proximity.
Potential Value Low to moderate, becoming mature woodland if given time and protection from disturbance.
Nursery/ Breeding Ground No significant observation, but can provide breeding habitats for birds and reptiles
Age Young (10 - 20 years) based on tree size, woodland structure and species composition.
Abundance/ Richness of Wildlife Low to moderate abundance for bird and butterfly, very low abundance for dragonfly.
Overall Ecological Value Low to moderate
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-26 B&V / ERM
Table 5.15 – Evaluation of Shrubland-grassland Criteria Shrubland-grassland
Naturalness Semi-natural habitats and disturbed by human activities such as fires.
Size Overall size of approximately 609.4 ha.
Diversity Moderate diversity of plants (94 species), low structural complexity. Low diversity for bird,
low to moderate for butterfly, very low diversity for dragonfly
Rarity None for plant species
Protected fauna species included Black Kite, Greater Coucal, Hwamei and Copperhead Racer
Re-creatability Habitat characteristics are easy to recreate but species composition may be different.
Fragmentation Not applicable.
Ecological Linkage Not functionally linked to any highly valued habitat in close proximity.
Potential Value Low to moderate, becoming mixed woodland if given time and protection from disturbance.
Nursery/ Breeding Ground No significant observation, but can provide breeding habitats for mammals, birds, reptiles and
butterflies
Age Not applicable.
Abundance/ Richness of Wildlife Low abundance for bird, low to moderate for butterfly, very low abundance for dragonfly
Overall Ecological Value Low to moderate
Table 5.16 – Evaluation of Cultivated Land Criteria Cultivated Land
Naturalness Man-made habitat mostly abandoned.
Size Small patches of active agricultural land were recorded within the Study Area with an overall
size of approximately 5.8 ha.
Diversity Low diversity of plants (48 species).
Low diversity for bird, butterfly and dragonfly
Rarity None for plant species.
Protected fauna species included Japanese Pipistrelle.
Re-creatability Habitat characteristics and species composition are easy to recreate.
Fragmentation Not applicable.
Ecological Linkage Not functionally linked to any highly valued habitat in close proximity.
Potential Value Low to moderate, some orchard and tree nursery may become mixed woodland if given time
and protection from disturbance.
Nursery/ Breeding Ground No significant observation, limited due to high level of human disturbance
Age N/A
Abundance/ Richness of Wildlife Low abundance for bird, butterfly and dragonfly
Overall Ecological Value Low
Table 5.17 – Evaluation of Marsh Criteria Marsh
Naturalness Semi-natural (cultivated land abandoned and subject to natural succession).
Size 18.4 ha
Diversity Low to moderate diversity of plants (61 species)
Low to moderate diversity for bird and dragonfly, low diversity for butterfly Rarity Plant species of conservation importance included Water Shamrock Marsilea quadrifolia and
Water Spangles Salvinia natans
Protected fauna species included Chinese Bullfrog
Re-creatability Moderate difficult to recreate due to hydrological conditions
Fragmentation Isolated stands but fairly intact
Ecological Linkage Hydrologically linked to streams.
Potential Value Moderate if protected from disturbance and conversion to other land use.
Nursery/ Breeding Ground No significant observation, but can provide breeding habitat for amphibian
Age N/A
Abundance/ Richness of Wildlife Low to moderate abundance for bird and dragonfly, low abundance for butterfly
Overall Ecological Value Moderate to high
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-27 B&V / ERM
Table 5.18 – Evaluation of Stream/Channel
Criteria Stream/Channel
Naturalness Semi-natural habitat, upper course intercepted by catchwater, middle course fairly natural and lower course
moderately modified Size Overall area approximately 20.4 ha, with its total length approximately 8.1 km.
Diversity High diversity of aquatic fauna
Low diversity of plants (32 plant species)
Low to moderate diversity for dragonfly, low diversity for bird and very low for butterfly
Rarity Common habitat type in Hong Kong.
One fish species was considered “Endangered” by IUCN (Japanese eel Anguilla japonica),
one fish species was considered Vulnerable in China Red Data Book (Predaceous Chub Parazacco spilurus),
three fish species were considered rare/ uncommon in Hong Kong and classified as “Lower Risk/Near
Threatened” by IUCN (Eye-spotted puffer Takifugu ocellatus, Sleepy goby Psammogobius biocellatus, and
Indo-pacific tropical sand goby Favonigobius reichei),
two uncommon species and classified as ‘Least Concern” by IUCN (Small snakehead Channa asiatica and
Spotty band goby Glossogobius olivaceus),
one endemic crustacean species (Sesarmind crab Pseudosesarma patshuni)
Re-creatability Habitat characteristics are difficult to recreate
Fragmentation Not applicable.
Ecological Linkage Functionally linked to the intertidal habitats.
Potential Value Moderate if given time and protection from disturbance.
Nursery/ Breeding
Ground
Estuarine sections could act as nursery ground for marine/intertidal fauna. Also can provide breeding habitat
for dragonfly and amphibian
Age N/A
Abundance/ Richness
of Wildlife
Moderate for aquatic fauna; low to moderate abundance for dragonfly, low abundance for bird, and butterfly
Overall Ecological
Value
Moderate to high
Table 5.19 – Ecological Evaluation of Mangrove Criteria Mangrove
Naturalness Natural habitat
Size Approximately 2.9 ha
Diversity Very low diversity of plants (10 species).
Low to moderate diversity of bird, very low diversity for butterfly and no record of dragonfly
Rarity No terrestrial or intertidal flora or fauna of conservation importance found
Re-creatability Mangrove is moderately easy to recreate
Fragmentation Isolated small stands of mangroves
Ecological Linkage Linked to stream and subtidal habitats in close proximity.
Potential Value N/A
Nursery/ Breeding Ground No significant observation.
Age Not applicable.
Abundance/ Richness of Wildlife Low to moderate for bird, very low abundance for butterfly and dragonfly
Overall Ecological Value Moderate to high
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-28 B&V / ERM
Table 5.20 – Ecological Evaluation of Urbanised/ Disturbed Area Criteria Urbanised/ Disturbed Area
Naturalness Man-made habitat dominated by landscape plants and weed plants.
Size Major patches were recorded within the Study Area with an overall size of approximately 105.1 ha.
Diversity Moderate diversity of plants (112 species),
Low to moderate for bird and butterfly, very low diversity for dragonfly
Rarity No flora of conservation importance.
Protected fauna species included Japanese Pipistrelle and Greater Coucal
Re-creatability Habitat characteristics and species composition are easy to recreate.
Fragmentation Not applicable.
Ecological Linkage Not functionally linked to any highly valued habitat in close proximity.
Potential Value Low
Nursery/ Breeding Ground No significant observation. Limited due to high level of disturbance and low vegetation cover.
Age N/A
Abundance/ Richness of Wildlife Low to moderate for bird and butterfly, very low abundance for dragonfly
Overall Ecological Value Low
Table 5.21 – Evaluation of Rocky Shore and Sandy Shore
Criteria Rocky Shore Sandy Shore
Naturalness Natural habitat Largely natural, although some are modified due to
designation as public beaches Size Total area is approximately 3.6 ha. Total area is approximately 9.6 ha.
Diversity Low diversity for intertidal fauna (18 species) Low diversity for intertidal fauna (16 species)
Rarity No species of conservation importance were found No species of conservation importance were found
Re-creatability Habitat characteristics and species composition are
difficult to recreate.
Habitat characteristics and species composition are
difficult to recreate.
Fragmentation N/A N/A
Ecological Linkage Not functionally linked to any highly valued habitat in
close proximity
Not functionally linked to any highly valued habitat
in close proximity.
Potential Value Low Low
Nursery/ Breeding
Ground
No significant observation No significant observation
Age N/A N/A
Abundance/ Richness
of Wildlife
Low abundance for intertidal fauna Low abundance for intertidal fauna
Overall Ecological
Value
Low to moderate Low
Table 5.22 – Ecological Evaluation of Sandflat Criteria Sandflat
Naturalness Natural habitat along intertidal zone
Size Total area of sandflat is approximately 24.0 ha
Diversity Low diversity for intertidal fauna (16 species)
Rarity Horseshoe crab juveniles were recorded during survey
Re-creatability Habitat characteristics and species composition on sandflat are difficult to recreate
Fragmentation Sandflat is fairly intact
Ecological Linkage Linked to stream and subtidal habitats in close proximity.
Potential Value Low
Nursery/ Breeding
Ground
Horseshoe crab breeding site
Age N/A
Abundance/ Richness
of Wildlife
Low to moderate abundance for intertidal fauna
Overall Ecological
Value
Moderate to high
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-29 B&V / ERM
Table 5.23 – Evaluation of Shallow Subtidal Hard Substrate Seabed and Subtidal Soft Substrate
Seabed Criteria Shallow Subtidal Hard Bottom Seabed Subtidal Soft Bottom Seabed
Naturalness Natural habitat Natural habitat
Size Total area within Study Area is approximately 72.4 ha Total area within Study Area is approximately 292.8 ha
Diversity Very low diversity of epibenthos and corals (1 species
of common hard coral Oulastrea crispata at very low
coverage)
Moderate to high diversity of benthic infauna (70
species)
Rarity No rare species was recorded No rare species was recorded
Re-creatability Habitat characteristics and species composition are
difficult to recreate.
Habitat characteristics and species composition are
difficult to recreate.
Fragmentation N/A N/A
Ecological Linkage Not functionally linked to any highly valued habitat in
close proximity
Not functionally linked to any highly valued habitat in
close proximity.
Potential Value Low Low
Nursery/ Breeding
Ground
No significant observation. No significant observation.
Age N/A N/A
Abundance/ Richness
of Wildlife
Low abundance for corals Relatively high abundance for benthic infauna
Overall Ecological
Value
Low Low to moderate
Table 5.24 – Evaluation of Coastal/Marine Waters Criteria Coastal/ Marine Waters
Naturalness Natural habitat and close proximity to the marine traffic lanes
Size N/A
Diversity The area is within the habitat range for both Chinese White Dolphin and Finless Porpoise
Rarity The South Lantau waters (extending from Fan Lau to south of Cheung Chau) is the only area in Hong Kong where
there is a major spatial overlap in the distribution of Indo-Pacific Humpback dolphin and Finless Porpoises.
Marked seasonal differences of these two species in terms of the use of South Lantau waters are observed.
Re-creatability N/A
Fragmentation N/A
Ecological Linkage Preferred marine mammal habitat occurs to the northwestern Lantau for Chinese White Dolphins and South
Lamma for finless porpoises
Potential Value South of Soko Islands has been considered as a potential marine park as included in the Proposed Southwest
Lantau Marine Park
Nursery/ Breeding
Ground
No key nursery areas
Age N/A
Abundance/
Richness of
Wildlife
Seasonal difference in dolphin distribution was observed in South and North Lantau waters. Abundance of
Chinese White Dolphins in South Lantau was low when compared to the preferred habitat in West and Northwest
Lantau. High concentrations of Finless Porpoise sightings can be found to the south of Tai A Chau and between
Shek Kwu Chau and Soko Islands.
Overall Ecological
Value
Low to Moderate
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-30 B&V / ERM
Table 5.25 – Evaluation of Floral and Faunal Species of Conservation Importance Recorded within the
Study Area Species Location and Activities (if
any)
Protection Status Distribution Commonness in
Hong Kong
Flora
Incense Tree
Aquilaria sinensis
In mixed woodland and
fung shui woodland. Found
in within the footprint of
San Shek Wan alternative
pumping station F(Option
2) and San Shek Wan
Sewage Treatment Works
Protected under the Protection of
Endangered Species of Animals and
Plants Ordinance (Cap 586). Category II
protected plant in the List of Wild Plants
under State Protection in PRC. Near
Threatened in PRC. Listed as
“Vulnerable” in the China Plant Red
Data Book and by IUCN (2009).
Lowland forests
and Fung shui
woodland
Common
Hong Kong
Pavetta
Pavetta
hongkongensis
In mixed woodland near Pui
O Village
Protected under Forestry and
Countryside Ordinance (Cap 96)
Fung shui
woodland and
lowland forest
Common
Silver-back
Artocarpus
Artocarpus
hypargyreus
In plantation along South
Lantau Road
Category II protected plant in the List of
Wild Plants under State Protection in
PRC. Near Threatened in PRC.
Fung shui
woodland and
lowland forest
Common
Water Shamrock
Marsilea
quadrifolia
In marsh - Ponds and ditches,
marshes
This species
listed as common
in the past but is
recently ranked as
very rare locally
due to loss of
paddy habitats.
Water Spangles
Salvinia natans
In marsh - Ponds, paddy
fields and ditches
This species
listed as very
common in the
past but is
recently ranked as
very rare locally
due to loss of
paddy habitats.
Zoysia sinica In mangrove, marsh and
sandflat, but outside of
Project Area
Category II protected plant in China and
under the List of Wild Plants under State
Protection (Part 1)
On sandy beaches,
river-bank
This species is
considered fairly
common in Hong
Kong
Luofushan Joint-
fir
Gnetum
luofuense
In woodland outside of
Project Area
Near threatened by IUCN Red list Commonly found
entangling large
trees
This species is
considered fairly
common in Hong
Kong
Fauna
Reef Egret
Egretta sacra
In sandy shore and rocky
shore
Protected under Cap. 170 – Wild
Animals Protection Ordinance;
Class 2 Protected Animal of PRC
Mainly found in
rocky shore
Uncommon
Black Kite
Milvus migrans
Soaring above mixed
woodland,
shrubland/grassland
Protected under Cap. 170 – Wild
Animals Protection Ordinance;
Class 2 Protected Animal of PRC;
Appendix 2 of CITES
Occurs in many
types of habitats
Common
Collared Scops
Owl Otus lettia
In plantations Protected under Cap. 170 – Wild
Animals Protection Ordinance;
Class 2 Protected Animal of PRC
Woodland Common
Greater Coucal
Centropus
sinensis
In plantation,
urbanised/disturbed,
shrubland/grassland
Protected under Cap. 170 – Wild
Animals Protection Ordinance;
Class 2 Protected Animal of PRC;
Classified as “vulnerable” by China Red
Data Book
Occurs in many
types of habitats
Common
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Species Location and Activities (if
any)
Protection Status Distribution Commonness in
Hong Kong
Hwamei
Garrulax canorus
In shrubland/grassland Protected under Cap. 170 – Wild
Animals Protection Ordinance;
Appendix 2 of CITES
Hillsides covered
by thick
shrublands
Common
Japanese
Pipistrelle
Pipistrellus
abramus
In urbanised/disturbed,
mixed woodland, cultivated
land and plantation
Protected under Cap. 170 – Wild
Animals Protection Ordinance
Occurs in many
types of habitats
Very Common
Chinese Bullfrog
Hoplobatrachus
chinensis
In marsh Class 2 Protected Animal of PRC Occurs in
cultivated lands,
ponds, rivers and
marshes
Fairly Common
Copperhead
Racer Elaphe
radiata
In mixed woodland,
plantation,
shrubland/grassland
Classified as “endangered” by China Red
Data Book
Occurs in many
types of habitats
Common
Predaceous Chub
Parazacco
spilurus
Pui O Stream
Tong Fuk Stream
“Vulnerable” in China Red List A widespread
species occurring
in most unpolluted
hill streams in
both upper and
lower courses.
Common
Sleepy goby
Psammogobius
biocellatus
Pui O Stream "Lower Risk/Near Threatened” by IUCN Streams in Sai
Kung and
northeastern New
Territories.
Uncommon
Indo-pacific
tropical sand
goby
Favonigobius
reichei
Pui O Stream
Tong Fuk Stream
Shui Hau Stream
"Lower Risk/Near Threatened” by IUCN Found in intertidal
waters throughout
Hong Kong.
Common
Japanese eel
Anguilla japonica
Pui O Stream
Shui Hau Stream
“Endangered” by IUCN Streams in Sai
Kung, Lantau
Island and Hong
Kong Island
Common
Eye-spotted
puffer
Takifugu
ocellatus
Pui O Stream
Shui Hau Stream
IUCN - Near Threatened Coastal areas and
large estuaries
Rare
Small snakehead
Channa asiatica
Pui O Stream “Least Concern” by IUCN Found in few
streams in North
district and on
Lantau Island. The
fish is also
cultivated in some
fish farms and are
available from fish
market.
Uncommon
Spotty band goby
Glossogobius
olivaceus
Pui O Stream “Least Concern” by IUCN Restricted
distribution in
Hong Kong, only
recorded in a few
reservoirs and
estuarines
Uncommon
Sesarmid crab
Pseudosesarma
patshuni
Shui Hau Stream - Found along river
banks of
mangroves
Endemic to Hong
Kong,
Uncommon
Hard coral
Oulastrea
crispata
San Shek Wan and to the
west of San Shek Wan
Cap 586 Shallow subtidal
hard substrate
seabed
Common
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Species Location and Activities (if
any)
Protection Status Distribution Commonness in
Hong Kong
Horseshoe crab
Tachypleus
tridentatus
Shui Hau Wan Sandflat - Intertidal sandflats Uncommon
Indo-Pacific
humpback
dolphin
Sousa chinensis,
Southeast Lantau near Shek
Kwu Chau
Cap. 170;
Cap. 586;
"Near Threatened" by IUCN;
Appendix 1 of (CITES);
Class 1 Protected Animal of PRC
Coastal / Marine
water
Restricted
Finless Porpoise
Neophocaena
phocaenoides
South of Tai A Chau, and
between Shek Kwu Chau
and Soko Islands, Pui O
Wan
Cap. 170;
Cap. 586;
"Vulnerable" by IUCN;
Appendix 1 of CITES;
Class 2 Protected Animal of PRC
Coastal / Marine
water
Restricted
5.4 Ecological Evaluation for the Project Site
The Project compromises the following elements:
A village sewerage system, which consists of gravity sewers and is connected to the trunk
sewerage system described below,
A trunk sewerage system, which consists of trunk sewers, sewage pumping stations
(SPSs) and twin rising mains along South Lantau Road for conveyance of sewage
collected from the village sewerage described above to the proposed sewage treatment
works described below. The proposed trunk sewerage system has six trunk sewage
pumping stations in Shui Hau, Tong Fuk, Cheung Fu Street, Cheung Sha, San Shek Wan
and Pui O areas.
A sewage treatment works (STW) located at San Shek Wan. The STW also involves its
associated submarine outfall for treatment and disposal of treated sewage.
Given the limited space required by the gravity sewers and rising mains and the fact that these
facilities will overlap with existing roads and alleyways, the main part of the Project Site lies
in areas where San Shek Wan STW and the six SPSs are located. Table 5.26 presents the
habitat composition of each proposed/ alternative SPS and STW, which also includes their
associated access roads leading to the existing South Lantau Road and Chi Ma Wan Road.
The proposed Shui Hau SPS, Cheung Fu Street SPS, as well as their associated access roads
are mainly located within plantation habitat. Trees were dominated by the species that are
commonly used for plantation purpose such as Acacia confusa, Bauhinia x blakeana,
Chrysalidocarpus lutescens and Archontophoenix alexandrae. The Tong Fuk SPS is located
on shrubland-grassland while its access road largely lies along urbanlised area. Plants
recorded within this SPS and its vicinity included shrubs Ricinus communis, herbs Ananas
comosus, Alocasia odora, grass Cynodon dactylon and some scattered trees such as Microcos
nervosa. The Cheung Sha SPS overlaps with a patch of cultivated land, on which fruit trees
such as Annona squamosa and Musa paradisiaca and common crops including Ipomoea
batatas were the dominant plant species. Both of the proposed and the alternative San Shek
Wan SPSs and their associated access roads fall within the habitat of mixed woodland that
were dominated by a mixture of native pioneer species including Mallotus paniculatus and
Microcos nervosa and planted species including Acacia confusa and Dimocarpus longan.
The Pui O SPS and its associated access road is largely located within shrubland/grassland
habitat, where the dominant plant species included Alocasia odora, Axonopus compressus,
Cyrtococcum patens, Desmodium triflorum, Hedyotis corymbosa, Senna occidentalis, Sida
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rhombifolia. San Shek Wan STW and its associated access road are located within urbanized
area and mixed woodland habitat where Acacia confusa, Alangium chinense, Elephantopus
scaber, Liriope spicata, Lygodium japonicum, Paederia scandens were commonly found.
The plant species recorded within the Project Site during the baseline surveys are provided in
Table 5.25 and Table A2 of Annex 5B. Apart from Aquilaria sinensis, all the species are
common in Hong Kong, with no restricted, rare or protected species found within the direct
footprint of the STW and SPSs (Table 5.25).
In terms of wildlife, mammal such as Japanese Pipistrelle (Pipistrellus abramus), birds
including Chinese Bulbul (Pycnonotus sinensis), Oriental Magpie Robin (Copsychus saularis)
and Spotted Dove (Streptopelia chinensis) etc, reptile Chinese Gecko (Gekko chinensis),
butterflies including Angled Castor (Ariadne ariadne), Indian Cabbage White (Pieris canidia)
and Common Grass Yellow (Eurema hecabe) etc and dragonflies such as Red-faced
Skimmer (Orthetrum chrysis) and Common Blue Skimmer (Orthetrum glaucum) were
recorded within the Study Area during the baseline surveys (Tables B2, C2, D2 and E2 of
Annex 5B refer). All of the wildlife species recorded are common or very common in Hong
Kong, with no rare or protected species found. No species of conservation importance were
recorded within the direct footprint of the STW and SPSs (Table 5.25).
Based on the habitat composition as well as the vegetation and wildlife species recorded
within each SPSs and STW, the ecological values of habitats found at Shui Hau SPS, Tong
Fuk SPS, Cheung Sha SPS, Pui O SPS and San Shek Wan STW are considered to be low or
low to moderate, whilst part of the proposed and alternative San Shek Wan SPSs comprise
habitats with moderate ecological value (e.g. the mixed woodland are considered to have
moderate ecological values) (Table 5.26).
In terms of marine ecology, the Project site (where the submarine outfall diffuser will be
located) is of low ecological value due to its small size, low faunal diversity and absence of
key sensitivities from its inshore location.
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Table 5.26 – Habitat Composition of Each Proposed/Alternative SPS and STW in hectares (ha) Habitat Ecological
Value of
Habitat
Within
Study Area
Shui Hau
SPS
Tong Fuk
SPS
Cheung Fu
Street SPS
Cheung Sha
SPS
San Shek
Wan SPS
(Proposed)
Pui O Trunk
SPS
San Shek
Wan STW
San Shek
Wan SPS
(Alternative)
Total
Habitat Loss
(1)*
Total
Habitat Loss
(2)*
Mixed Woodland Moderate 305.5 0 0 0 0 0.14 0 0.38 0.17 0.52 0.55
Plantation Low to
moderate
163.9 0.11 0 0.08 0 0 0 0.01 0 0.20 0.20
Shrubland-
grassland
Low to
moderate
609.4 0 0.04 0 0 0 0.15 0 0 0.19 0.19
Cultivated Land
Low 5.8 0 0 0 0.04 0 0 0 0 0.04 0.04
Urbanised/
Disturbed Area
Low 105.1 0 0.02 0 0 0 0.03 0.17 0 0.22 0.22
Total: 0.11 0.06 0.08 0.04 0.14 0.18 0.56 0.17 1.17 1.20
* ‘Total Habitat Loss (1)’ is calculated with the assumption that the Proposed San Shek Wan SPS will be adopted, while ‘Total Habitat Loss (2)’ is with the assumption that the Alternative San
Shek Wan SPS will be adopted
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5.5 Potential Sources of Impact
Potential sources of impacts to ecological resources can arise from both the construction and
operation phases. Each is discussed in turn below.
5.5.1 Construction Phase
Land-based construction activities and minor marine dredging works of this Project have the
potential to affect ecological resources by:
Direct loss of habitats and vegetation removal within the footprints of the sewers, sewage
pumping stations and San Shek Wan STW;
Direct loss/ disturbances to benthic habitat within the marine works area;
Potential impact on recognized sites of conservation importance;
Habitat fragmentation and isolation, including restriction of wildlife utilisation of the area
(i.e. transit, feeding and roosting) especially for those inactive/ less mobile/ habitat-
specific wildlife nesting/inhabiting the habitats, and degradation of habitat quality/
ecological function;
Physical disturbance to the surrounding habitats and associated wildlife due to noise and
increased human activities (including construction vessels), etc.; and
Potential indirect impact on water quality, hydrodynamics properties, sedimentation rates
and pattern, as well as hydrology.
5.5.2 Operation Phase
The potential impacts of the operational phase of the Project on the ecology of the Study Area
are mainly due to perturbations to key water quality parameters due to discharge of treated
effluent from the STW and emergency overflow of untreated sewage from the trunk sewerage
and STW.
The operation of this Project would involve disinfection facilities within the STW but the use
of chemical disinfection which may be of concern to ecology (e.g. chlorine disinfection) is not
present.
Terrestrial ecological resources are not expected to be impacted by the Project’s operational
activities.
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5.6 Impact Assessment
5.6.1 Terrestrial Ecology
Habitat Loss
The major impact on terrestrial ecological resources will be direct habitat loss. While the
gravity sewers/rising mains will be installed underneath existing roads / accesses, the
proposed and alternative SPSs as well as San Shek Wan STW will be constructed in the
habitats including mixed woodland, plantation, shrubland-grassland, cultivated land and
urbanised/disturbed area. The habitat composition and their areas at each SPS and STW (i.e.
habitat loss) are summarized in Table 5.26, ecological values and the total areas of the
habitats within the Study Area are provided as well.
A total of 0.52 ha of mixed woodland, 0.20 ha of plantation, 0.19 ha of shrubland-grassland,
0.04 ha of cultivated land and 0.22 ha of urbanised/disturbed area would be lost due to site
formation works for the SPSs and the STW. If the alternative San Shek Wan SPS is adopted
instead of the proposed one, total habitat loss caused by this Project would be 0.55 ha of
mixed woodland, 0.20 ha of plantation, 0.19 ha of shrubland-grassland, 0.04 ha of cultivated
land and 0.22 ha of urbanised/disturbed area. Except for the proposed and alternative San
Shek Wan SPSs and STW, the habitats to be lost are of low or low to moderate ecological
values for all the other SPSs and STW. Approximately 0.52 – 0.55 ha of mixed woodland of
moderate ecological value will be lost due to the construction of the proposed/ alternative San
Shek Wan SPS, San Shek Wan STW and their associated access roads.
Site clearance will be undertaken prior to site formation works and all vegetation existing
within the affected habitats will be removed. According to the findings of the baseline
surveys, all the plants found within the Project Site are common species, with no flora species
of conservation importance recorded except at the San Shek Wan Alternative SPS location
and San Shek Wan STW where protected plant species Aquilaria sinensis in fair condition
were found in the footprint of the SPS (Table A1 of Annex 5B).
The mixed woodland to be lost will be compensated at suitable areas within the site boundary
of the San Shek Wan STW. For the plant species of conservation importance Aquilaria
sinensis found in the San Shek Wan SPS Alternative Site and San Shek Wan STW,
transplantation plan will be prepared prior to construction. The impact significance of habitat
loss arising from the construction is hence considered to be low to moderate, and impact of
vegetation removal associated with the Project construction would be low and managed to
acceptable level.
Impact on Recognized Sites of Conservation Importance
Within the Study Area, recognized sites of conservation importance include mangroves in Pui
O, Fung Shui woodlands in Tong Fuk and Shui Hau, Lantau South Country Park (CP)and
Ecologically Important Steams (EIS) at Tong Fuk and Pui O (Figure 5.1). The Project Site
does not encroach onto any mangroves, Fung Shui woodlands and Lantau South Country Park,
on which potential ecological impact is consequently not expected.
When the proposed pipe mains passes the EIS at Tong Fuk, pipe laying will adopt a bridge-
mounted type without disturbing the stream bottom and riparian vegetation along stream bank.
Also since there is sufficient headroom under the bridge, the pipe would be suspended above
the stream water. By using such construction method as well as the implementation of good
practice to control site run-off (see Section 4.9.1 for detailed mitigation measures to control
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construction site runoff and drainage), the potential impact of land based construction
activities on the ecology of the EISs is predicted to be minor.
For the proposed gravity sewer across the EIS at Pui O, the pipe will be laid by pipe-jacking
method in which a jacking pit and a receiving pit will be constructed on the land adjacent to
the stream and about 0.5 m diameter of pipe will be jacked from the jacking pit to the
receiving pit without disturbing the stream and riparian vegetation as the pits are located at
sufficient distance (at least 5 m) from the stream banks and the surrounding areas are free
from riparian vegetation. The pipe will be constructed underground below the Pui O EIS and
kept clear distance at least 2 m below the stream bed. The implementation of pipe laying
works by using pipe-jacking method will be scheduled to dry season. The construction and
operation of the pipe will not cause change in water level as the substratum above the tunnel
and the tunnel will be impervious to gravitational flows of stream water. As the scale of
works (i.e. the pipe is at 0.5 m in diameter and 5 m long) is small and there will be sufficient
distance below the stream bed, the vibration arisen from the pipe-jacking is minor. By using
such construction method as well as the implementation of good practice to control site run-
off (see Section 4.9.1 for detailed mitigation measures to control construction site runoff and
drainage), the potential impact on the water table and ecology of the EIS is predicted to be
minor.
Habitat Fragmentation and Isolation
The effect of habitat fragmentation and isolation arising from the Project is expected to be
minor. This is because firstly the large continuous and undisturbed habitats such as mixed
woodland and shrubland-grassland in the north of the Study Area will remain untouched
throughout the construction of the Project. Secondly most of the proposed sewers and rising
mains will be laid along existing roads / accesses. For the SPSs and STW whose footprints
extend to mixed woodland, plantation, shrubland-grassland or cultivated land, the affected
habitats are either in close proximity to disturbed area or are already fragmented in nature.
Hence, the reduction of wildlife utilisation of the areas (i.e. transit, feeding and roosting)
especially for those less mobile / habitat-specific species as a result of habitat fragmentation
would not be significant.
Noises, Human Activities and Other Disturbances
Secondary impacts to the surrounding habitats and associated wildlife may arise from the
potential of increased noise, human activities and other physical disturbances. Feeding or
breeding activities may be disturbed if noise levels are significant over a long term. The
impacts are expected to be low owing to the existing human presence in nearby areas, the
temporary nature and relatively small scale of the construction works. Given the
implementation of environmental mitigation measures and regular checks on construction
practices, the impacts are not expected to be unacceptable.
Impacts from Emergency Discharge during Operation Phase
Should the breakdown of pumping stations occur, raw sewage would be discharged into
adjacent streams when the emergency storage capacities are exceeded. However, the
possibility of emergency discharge of raw sewage is extremely low and it is expected to
happen for a very short period of time (i.e. 2 hours) because repair operations will be arranged
promptly. In addition, as the pumping stations are located at the lower section of these
streams and any discharges would flow downstream, it is expected that no impacts would
occur to the upstream regions of the streams and any potentially sensitive freshwater species
or ecosystems that may be present within those waters.
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Based on the above, no unacceptable adverse impacts to stream/channel would be expected to
occur due to an emergency discharge from the breakdown of the pumping stations. It is also
important to note that although this event has been assessed for acceptability, the possibility
of its occurrence is extremely low because of sufficient preventive measures, including
standby pumps, dual power supplies and emergency storage, have been proposed for the
sewage pumping stations.
5.6.2 Marine Ecology
As indicated by the findings of the water quality impact assessment and water quality
modeling results (Section 4.8 refers), the predicted zone of influence of the Project is limited
to the immediate vicinity of the marine development footprint. In this context, the marine
ecological impact assessment in this section focuses on the area around the development
footprint.
Construction Phase
Potential impacts of the construction activities on marine ecological resources are presented in
Table 5.27.
Table 5.27 – Summary of Potential Construction Phase Impacts associated with Marine Dredging
Works for the Submarine Outfall Nature of Impact Marine Habitat Affected Potential Impact
Habitat Loss Subtidal Soft Bottom Habitat Loss/ Disturbance of approximately 0.13 ha of seabed
Changes in Water Quality
(i.e. Suspended Solids,
Dissolved Oxygen &
Contaminant Release)
Subtidal Soft Bottom Habitat Potential burial of benthic organisms
Subtidal Hard Bottom Habitat (including
corals)
Potential water quality impacts on isolated hard coral
colonies
Intertidal Habitats Potential water quality impacts on intertidal organisms
Coastal / Marine Water Habitat Potential water quality impacts on marine mammals
Vessel Disturbance Coastal / Marine Water Habitat Potential physical disturbance to marine mammals
Habitat Loss
The direct impacts of the minor marine dredging activities will be the loss of subtidal soft
bottom habitats and the potential removal of organisms associated with the installation of the
submarine outfall diffuser at the end of the submarine pipeline. The marine dredging area
would be very small, i.e. approximately 0.13 ha.
It is important to determine whether the area of disturbance contain species of interest or
noteworthy benthic assemblages, which will be lost during the marine works. Findings from
the literature reviews and the baseline subtidal benthos survey indicated that the benthic
assemblages within and in the vicinity of the working areas were dominated by polychaetes.
All species recorded are found to be common in Hong Kong and no rare species were
observed. As a result, the assemblages were regarded as low ecological value. No
unacceptable impacts are expected to be associated with the loss of subtidal soft bottom
habitat of low value.
Changes in Water Quality
Suspended Sediments
Subtidal Soft Bottom Habitat
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The subtidal soft benthos in and around the proposed submarine outfall is considered to be of
low to moderate ecological value. Sessile organisms will be susceptible to the effects of
increased sediment loads through smothering and burial. Sediment may be deposited on the
seabed outside the reclamation sites during dredging and backfilling due to the dispersion of
sediments. Temporary impacts are expected to be the largest in the immediate vicinity of the
dredging works (i.e. in the mixing zone) when the works are underway, while impacts on the
wider marine environment (>1 km away from the works area) expected to be very low due to
gradual deposition of SS over a short distance.
Owing to the small scale and the low severity of sedimentation associated with the marine
dredging works (see Section 9.4.1.1 for details), the indirect disturbance on benthic
assemblages in the vicinity if the works area are expected to be of low severity and localized.
With the assumption that the temporarily affected subtidal soft bottom habitats due to marine
dredging works could be recolonised by fauna which is typical to that area, the temporary
disturbance to these low to moderate ecological value assemblages is not considered to be
unacceptable.
Subtidal Hard Bottom Habitat (including Corals)
Since no rare species was found in the subtidal hard bottom habitat in the vicinity of the
submarine outfall, shallow subtidal hard bottom habitat is regarded as low ecological value.
The transient nature of any increase in suspended sediment arising from marine dredging
works will have no unacceptable adverse impacts on this habitat of low ecological value.
Intertidal Habitats
Intertidal habitats within the Study Area which can be affected by the marine dredging works
include natural rocky shore, sandy shore and Shui Hau Wan Sandflat. Sediment dispersion
modeling results predicts that the SS elevations due to marine dredging will be transient and
will be confined to the proposed works area. Thus, it is expected that unacceptable impacts
from elevated SS levels to the intertidal assemblages, including the possible Horseshoe crab
breeding ground at Shui Hau Wan sandflat, within the Study Area will not occur.
Coastal / Marine Water Habitats
High suspended sediments do not have adverse impacts on marine mammals (i.e. Finless
Porpoises and Chinese White Dolphins) as they are well-adapted to hunt in turbid waters by
means of echolocation rather than merely depending on visual information. Moreover,
Finless Porpoises and Chinese White Dolphins are air-breathing, so elevated levels of
suspended sediments in waters would not cause any adverse effects on their respiratory
surfaces. However, the impact on these marine mammals may occur as an indirect result of
elevated SS levels. The minor marine dredging works may cause deterioration to water
quality, which may potentially impact the fisheries resources. Information from the fisheries
impact assessment (Section 6) indicates that indirect impacts are not predicted to impact
fisheries resources adversely as the elevation of suspended sediments due to sediment plume
will be transient and localized to the works area. Thus, impacts on marine mammals due to
reduced food supply are not predicted to occur. As a result, unacceptable impacts to marine
mammal habitats due to increased suspended sediment levels will not occur.
Dissolved Oxygen
The assessment examining potential impacts of elevated SS levels associated with the
proposed marine dredging works showed that the impacts are likely to be minor, localised to
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the mixing zone and transient. Consequently, DO depletion as a result of dispersion of
sediment plumes associated with marine works of the Project is expected to be within
acceptable levels and its effect on marine ecological resources is also likely to be very limited.
Contaminant Release
Owing to the unpolluted nature of the seabed sediment within the dredging area (see Section 9
of this EIA Report), unacceptable water quality impacts due to the potential leaching of
metals and micro-organic pollutants from the disturbed sediments into the water column are
not expected to occur.
Vessel Operational Discharges
As discussed in Section 4.7.1, construction vessels have the potential for the liquid discharges
of uncontaminated deck drainage, potentially contaminated drainage from machinery spaces,
and sewage/grey water. These waste streams are all readily amenable to control as part of
appropriate practice on vessels. Possible impacts associated with construction vessel
discharges are therefore considered to be negligible.
Site Runoff from Land-based Construction Activities
Discharges and runoff from the land-based sites during the construction phase, particularly
during the site formation, excavation and backfilling works, will contain suspended solids
which could be a source of water pollution, causing short-term degradation of habitat quality.
However, considering that the scale of the construction works and with effective
implementation of good site management practices as well as mitigation measures mentioned
in Section 4.8, site run-off is not predicted to have an adverse impact on the natural coastline,
including Shui Hau Wan which is considered to be of moderate to high ecological value.
In summary, unacceptable impacts (elevated SS, nutrient and contaminant levels and DO
depletion) on sensitive receivers from sediment release associated with dredging works are
not expected to occur. Potential impacts arising from vessel operational discharges and land-
based site runoff during construction stage are also considered to be negligible.
Vessel Disturbance
Increased marine traffic during construction phase may result in physical disturbance to
marine mammals. In general, marine mammals have higher chance to be injured by high-
speed vessels, but the working vessels are not expected travelling in high speed. Underwater
noise from noisy equipment on working vessels may be a potential disturbance as marine
mammals are sensitive to sound and rely on sound to communicate and prey. The disturbance
from increased marine traffic may result in behavioral changes in marine mammals. Since the
duration of marine works is temporary in nature with a very low number of vessels to be
involved, and the marine works area is of very low usage of marine mammals, with the
implementation of marine traffic control, potential disturbances are expected to be minimized
and thus unacceptable impact during construction will be unlikely occurred.
Operation Phase
Impacts due to operational effluent discharge from the STW on marine ecological resources
are not expected as the discharge should satisfy the relevant requirements of WPCO-TM
effluent discharge standards (details refer to Sections 3 and 4). No unacceptable impacts are
thus anticipated.
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To prevent sewage overflow from the sewage pumping stations due to plant failure, standby
pumps, dual power supply and emergency storage will be provided to the sewage pumping
stations. The standby pumps and dual power supply will maintain continuous operation of the
sewage pumping stations when the duty pumps or main power supply are down. In extreme
situation when both the duty and standby pumps are down or the dual power supply are failed,
the sewage entering the sewage pumping stations will be bypassed to the emergency storage
to prevent sewage overflow.
The SPSs and STW are all designed to have one standby unit (e.g. standby pumps and
standby treatment units) in case of equipment failure. Dual power supply will be in place in
case of power breakdown. In case of failure of dual power supply, emergency storage for
SPSs and STW would be in place to prevent emergency discharge. A 6-hour (ADWF)
emergency storage will be provided for each SPS. In addition to the sewage from their local
catchments, some sewage pumping stations (i.e. Tong Fuk SPS, Cheung Fu Street SPS and
San Shek Wan SPS) will also receive sewage from their upstream sewage pumping stations.
When one of these sewage pumping stations is down, sewage entering this sewage pumping
station from its local catchment will be bypassed to its emergency storage and all of its
upstream sewage pumping stations will stop operation and the sewage entering the upstream
sewage pumping stations from their local catchments will be bypassed to their emergency
storages. It will then provide the required minimum 6 hours of emergency storage to prevent
sewage overflow, which has accounted for the required time for travelling to and repairing of
all the sewage pumping stations as confirmed by DSD. Regular inspection and maintenance
will be carried out by DSD’s maintenance crew which will station in the San Shek Wan STW.
During non-office hours, existing mobile team from Ma Wan STW will be responsible to
back up the maintenance crew in San Shek Wan STW. With the implementation of above
preventive measures, the possibility of sewage overflow from the sewage pumping stations
will be extreme low. However, for safety purpose, a safety outlet will be provided to each
emergency storage to prevent flooding of the sewage pumping station.
The following precautionary measures will also be implemented to further minimize the
occurrence of the emergency discharges:
Regular maintenance and checking of plant equipment to prevent equipment failure;
Use standby pump in case of pump failure or maintenance required; and
Use dual power supply to keep the pump in operation in case of main power failure. A
contingency plan is recommended to be developed at the detailed design stage.
As discussed in Section 4, in the case of emergency discharge, untreated sewage would be
discharged into the lower course of nearby streams, including the ecological important
streams at Pui O and Tong Fuk, and this would change the water quality of the streams.
During the emergency discharge, the raw sewerage is supposed to directly drain into the
streams whilst such discharge will last for very short period. In addition, based on the
observation in the ecological surveys, the flows in the ecological important streams at Pui O
and Tong Fuk are relatively higher with the lower courses of the streams have subject to
different levels of modification. Given the relatively higher flow, the potential impact due to
untreated sewage discharge under emergency scenario would be temporary in nature and
quickly recovered. It is also important to note that discharge of untreated sewage in the event
of emergency is of very low likelihood given the control measures (e.g. standby units, dual
power supplies and emergency storages) will be in place.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
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With the emergency overflow of untreated sewage, it is predicted that the increase in E. coli,
Total Inorganic Nitrogen and Unionised Ammonia would cause a short-term deterioration of
the water quality conditions near the proposed outlet location, i.e. off San Shek Wan around
Cheung Sha and Pui O in case of the emergency discharge period. However, it is considered
that the water quality conditions would quickly recover once after the dilution effect with
seawater and after the termination of emergency discharge for both wet and dry seasons. If
the emergency discharge points are controlled at Pui O stream, soil and plants of nearby
habitats may be affected. According to the assessment result in Section 4.8.2, the emergency
discharge will not cause long-term or unacceptable impact on the nearby streams. The overall
ecological impact on adjacent habitats is considered to be temporary and minor after
implementation of preventive measures.
5.7 Impact Evaluation
5.7.1 Terrestrial Ecology
Habitat Loss
From the information presented in Section 5.6.1, overall ecological impact associated with
habitat loss is considered to be low to moderate. An evaluation of habitat loss for each
affected habitat is provided in Table 5.28 – 5.32.
Mixed Woodland
Approximately 0.52 ha of mixed woodland will be lost due to the construction works of the
proposed site of San Shek Wan SPS. If the alternative site of San Shek Wan SPS is used, the
loss of mixed woodland will be slightly higher, which is 0.55 ha. In either option, the overall
unmitigated impact of habitat loss on mixed woodland is considered to be low to moderate
due to the small size of the affected area of moderate ecological value. For the protected plant
species Aquilaria sinensis recorded at San Shek Wan SPS (Alternative Option) and San Shek
Wan STW, transplantation plan will be developed accordingly (Figures 5.4j & 5.4l) (see
Table 5.28).
Table 5.28 – Impact of Habitat Loss on Mixed Woodland during Construction Phase Evaluation Criteria Mixed Woodland (Using the Proposed
San Shek Wan Trunk SPS)
Mixed Woodland (Using the Alternative
San Shek Wan Trunk SPS)
Habitat Quality The habitat quality is moderate.
Species of Conservation
importance
Plant species of conservation importance included Aquilaria sinensis at San
Shek Wan SPS Alternative Site and San Shek Wan STW (Refer to Table 5.12
for the flora and fauna species of conservation importance recorded within the
habitat of mixed woodland but outside the Project Site.)
Size/Abundance Permanent loss approximately 0.52
ha.
Permanent loss approximately 0.55 ha.
Duration The impact will persist during construction and operation phases.
Reversibility The loss is permanent and not reversible.
Magnitude The scale of the habitat loss and impact is small in the context of the
surrounding similar habitat, flora and fauna.
Overall Impact Before
Mitigation
Low to moderate Low to moderate
Plantation
Approximately 0.20 ha of plantation will be lost due to the construction works. The overall
unmitigated impact of habitat loss on plantation is considered to be low due to the small size
Outlying Islands Sewerage Stage 2 –
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of the affected area, low to moderate ecological value and high recreatibility of the habitat,
and the fact that no flora and fauna species of conservation importance was recorded during
the surveys (see Table 5.29).
Table 5.29 – Impact of Habitat Loss on Plantation during Construction Phase Evaluation Criteria Plantation
Habitat Quality The habitat quality is low to moderate.
Species of Conservation
importance
No species of conservation importance was recorded within the affected area.
Hence no species of conservation importance is likely to be impacted. (Refer to
Table 5.13 for the flora and fauna species of conservation importance recorded
within the habitat of plantation but outside the Project Site. The affected areas
and species of conservation importance are illustrated in Figures 5.4a to 5.4m.)
Size/Abundance Loss of approximately 0.20 ha.
Duration The impact will persist during construction and operation phases.
Reversibility Permanent loss is not reversible; temporarily affected area is reversible through
landscaping works within the SPS/STW
Magnitude The scale of the habitat loss and impact is small in the context of the
surrounding similar habitat, flora and fauna.
Overall Impact Before
Mitigation
Low
Shrubland-grassland
Approximately 0.19 ha of shrubland-grassland will be lost due to the construction works.
Shrubland-grassland is a habitat of low to moderate ecological value and relatively high re-
creatability. No flora or fauna species of conservation importance was recorded within the
affected area. Also because of the small size of the area affected, the impact of habitat loss on
shrubland-grass is considered to be low (see Table 5.30).
Table 5.30 – Impact of Habitat Loss on Shrubland-grassland during Construction Phase Evaluation Criteria Shrubland-grassland
Habitat Quality The habitat quality is low to moderate.
Species of Conservation
importance
No species of conservation importance was recorded within the affected area.
Hence no species of conservation importance is likely to be impacted. (Refer
to Table 5.14 for the flora and fauna species of conservation importance
recorded within the habitat of shrubland-grassland but outside the Project Site.
The affected areas and species of conservation importance are illustrated in
Figures 5.4a to 5.4m.)
Size/Abundance Permanent loss approximately 0.19 ha.
Duration The impact will persist during construction and operation phases.
Reversibility The loss is permanent and not reversible.
Magnitude The scale of the habitat loss and impact is small in the context of the
surrounding similar habitat, flora and fauna.
Overall Impact Before
Mitigation
Low
Cultivated Land
The habitat loss of cultivated land amounts to only 0.04 ha no matter which site of San Shek
Wan Trunk SPS is selected. No species of conservation importance was recorded within the
affected cultivated land. In view of its low ecological value and artificial nature that results in
a high recreatability, it is considered that the habitat loss of cultivated land would be of low
impact significance (see Table 5.31).
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
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Table 5.31 – Impact of Habitat Loss on Cultivated Land during Construction Phase Evaluation Criteria Cultivated Land
Habitat Quality The habitat quality is low.
Species of Conservation
importance
No species of conservation importance was recorded within the affected area.
Hence no species of conservation importance is likely to be impacted. (Refer
to Table 5.15 for the flora and fauna species of conservation importance
recorded within the habitat of cultivated land but outside the Project Site. The
affected areas and species of conservation importance are illustrated in
Figures 5.4a to 5.4m.)
Size/Abundance Permanent loss approximately 0.04 ha.
Duration The impact will persist during construction and operation phases.
Reversibility The loss is permanent and not reversible.
Magnitude The scale of the habitat loss and impact is very small in the context of the
surrounding similar habitat, flora and fauna.
Overall Impact Before Mitigation Low
Urbanised/ Disturbed Area
The habitat loss of urbanised/ disturbed area amounts to 0.22 ha no matter which site of San
Shek Wan Trunk SPS is selected. No species of conservation importance was recorded within
the affected area. In view of its low ecological value and artificial nature that results in a high
recreatability, it is considered that the habitat loss of urbanised/ disturbed area would be of
low impact significance (see Table 5.32).
Table 5.32 – Impact of Habitat Loss on Urbanised/Disturbed Area during Construction Phase Evaluation Criteria Urbanised/ Disturbed Area
Habitat Quality The habitat quality is negligible.
Species of Conservation
importance
No species of conservation importance was recorded within the affected area.
Hence no species of conservation importance is likely to be impacted. (Refer
to Table 5.20 for the flora and fauna species of conservation importance
recorded within the habitat of urbanised/ disturbed area but outside the Project
Site. The affected areas and species of conservation importance are
illustrated in Figures 5.4a to 5.4m.)
Size/Abundance Loss of approximately 0.22 ha.
Duration The impact will persist during construction and operation phases.
Reversibility The loss of this habitat is considered reversible since the new SPSs and STW
are also part of urbansed/disturbed area.
Magnitude The scale of the habitat loss and impact is small in the context of the
surrounding similar habitat, flora and fauna.
Overall Impact Before Mitigation Low
In view of the evaluation in Tables 5.28 – 5.32, apart from the Aquilaria sinensis to be
affected by the San Shek Wan SPS (Alternative site) and San Shek Wan STW, potential
impact on the other species of conservation importance listed in Table 5.25 is not anticipated.
Potential impact on species of conservation importance found in streams is considered to be
low.
Other Impacts
Impact on Recognized Sites of Conservation Importance – The construction works of the
Project will not encroach onto any mangrove and Fung Shui woodland habitats, Lantau South
Country Park or any Ecological Important Streams occurring within the Study Area. Given
the relatively low ecological value of most of the affected area, the small scale of the Project
Outlying Islands Sewerage Stage 2 –
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and no flora or fauna species recorded within the Project Site, potential impact on the Sites of
Conservation Importance is considered to be low.
Habitat Fragmentation and Isolation – The construction works will mainly be conducted
along existing roads and within residential area except some habitats such as mixed woodland,
plantation, shrubland-grassland or cultivated land. In the view of the small scale of the
Project and the availability of surrounding similar habitats, the potential impact of habitat
fragmentation and isolation on associated wildlife utilising the affected habitats is considered
to be minimal.
Noise, Human Activities and Other Disturbances – Increased human activities and
disturbances due to the Project construction have the potential to affect the surrounding
natural habitats and the associated wildlife. These potential impacts are expected to be low
given that regular checks on construction practices and boundaries will be conducted. As
there has been low level of human activities, wildlife is considered able to habituate slight
increase of disturbance. On the other hand, several mitigation measures for noise reduction
are recommended in Section 8.8 and the measures will also reduce the disturbance to wildlife.
Impacts from Emergency Discharge during Operation Phase – Emergency discharge of
raw sewage has the potential to affect the water and habitat quality nearby the safety outlet
location at mangroves of Pui O and Shui Hau, stream/channel at Tong Fuk, Cheung Fu Street,
lower Cheung Sha and San Shek Wan. These potential impacts are expected to be low given
that the emergency discharge, if occurs, would last for a very short period (2 hours) and the
possibility of its occurrence is extremely low because of sufficient preventive measures,
including standby pumps, dual power supplies and emergency storages have been proposed
for the sewage pumping stations.
5.7.2 Marine Ecology
The following section evaluates the impacts on marine ecological resources as a result of the
potential impacts identified in previous sections. Based upon the information presented above,
the significance of the marine ecological impact associated with the construction and
operation of the submarine outfall has been evaluated in accordance with the EIAO-TM
(Annex 8, Table 1) as follows. The outcomes of this evaluation are summarised in Table 5.33.
Outlying Islands Sewerage Stage 2 –
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Table 5.33 – Marine Ecological Impacts associated with Submarine Outfall during Construction and Operation Phases
Potential
Impact Receiver
Nature of Impact Habitat
Quality Species Affected Size /Abundance Duration Reversibility Magnitude Overall
Impact
Before
Mitigation Construction Phase Habitat Loss
&
Disturbance
Subtidal Soft
Bottom Habitat
within the
dredged area
The habitat
quality is low
to moderate.
No species of
conservation
importance was
recorded within the
Study Area. Hence
no species of
conservation
importance is likely
to be impacted.
Loss of approximately
0.13 ha of seabed. Permanent due to
installation of
outfall diffuser.
Not reversible No unacceptable
impacts to benthic
assemblage are
predicted to occur.
Low
Change in
Water Quality Subtidal Soft
Bottom Habitat,
Subtidal Hard
bottom
Habitats;
Intertidal
Habitats;
Coastal/ Marine
Water habitats
in close vicinity
of the dredged
area
The habitat
quality is
generally low
to moderate,
except it is
moderate to
high for
sandflat.
All affected habitats
are of low ecological
value. Horseshoe
crab juveniles were
recorded in sandflat
while Indo-Pacific
Humpback dolphin
and Finless
Porpoises were
recorded in coastal
water
Temporary increase in
SS is expected to be
localized. Impacts on
the wider marine
environment (>1 km
away from the works
area) expected to be very
low due to gradual
deposition of SS over a
short distance.
The marine
dredging works will
approximately
continue for a
period of one
month.
Reversible No unacceptable
impacts to benthic
assemblage are
predicted to occur.
Low
Vessel
Disturbance Coastal/ Marine
Water habitats
in close vicinity
of the dredged
area
The habitat
quality is
generally low
to moderate.
Indo-Pacific
Humpback dolphin
and Finless
Porpoises were
recorded in coastal
water.
- The marine
dredging works will
approximately
continue for a
period of one
month.
Reversible With the
implementation of
marine traffic control,
potential disturbances
are expected to be
minimized
Low
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-47 B&V / ERM
Potential
Impact Receiver
Nature of Impact Habitat
Quality Species Affected Size /Abundance Duration Reversibility Magnitude Overall
Impact
Before
Mitigation Operation Phase
Operational
effluent
discharge
Subtidal Soft
Bottom Habitat,
Subtidal Hard
bottom
Habitats;
Intertidal
Habitats;
Coastal/ Marine
Water habitats
in close vicinity
of the effluent
discharge
The habitat
quality is
generally low
to moderate,
except it is
moderate to
high for
sandflat.
All affected habitats
are of low ecological
value. Horseshoe
crab juveniles were
recorded in sandflat
while Indo-Pacific
Humpback dolphin
and Finless
Porpoises were
recorded in coastal
water
Impacts due to effluent
discharge to marine
ecological resources are
not expected as the
discharge should satisfy
the relevant requirements
of WPCO-TM effluent
discharge standards.
Long-term over the
operation of STW
Not reversible No unacceptable
impacts are thus
anticipated.
Low
Emergency
Discharge
Subtidal Soft
Bottom Habitat,
Subtidal Hard
bottom
Habitats;
Intertidal
Habitats;
Coastal/ Marine
Water habitats
in close vicinity
of the effluent
discharge
The habitat
quality is
generally low
to moderate,
except it is
moderate to
high for
sandflat.
All affected habitats
are of low ecological
value. Horseshoe
crab juveniles were
recorded in sandflat
while Indo-Pacific
Humpback dolphin
and Finless
Porpoises were
recorded in coastal
water
A short-term
deterioration of the water
quality conditions near
the proposed outlet
location is expected, but
the water quality
conditions would quickly
recover once after the
dilution effect with
seawater and after the
termination of
emergency discharge for
both wet and dry
seasons.
The occurrence of
emergency overflow
of untreated sewage
is expected to be
highly unlikely in
place with
safeguards and
controls.
Reversible Overall ecological
impact on adjacent
habitats is considered
to be temporary and
minor after
implementation of
preventive measures.
Low
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-48 B&V / ERM
The impact assessment presented above indicates that no unacceptable impacts to various
marine ecological resources mentioned in the above sections would be expected. Although
subtidal soft bottom habitats will be disturbed due to dredging, it is expected that the seabed
will be recolonised by benthic assemblages and return to the former existing state after the
completion of the marine dredging works. As such, potential impact on the hydrodynamic
properties and hydrology is not anticipated, and impacts to marine ecological resources during
operation phase are expected to be negligible.
5.8 Mitigation Measures
General
In accordance with the guidelines in the EIAO-TM Annex 16 on ecological impact assessment,
the policy adopted in this EIA for mitigating significant impacts to ecology, in order of
priority, is:
Avoidance: Potential impacts should be avoided to the maximum extent practicable by
adopting suitable alternatives;
Minimisation: Unavoidable impacts should be minimised by taking appropriate and
practicable measures such as constraints on intensity of works operations or timing of
works operations; and
Compensation: The loss of important species and habitats may be provided for
elsewhere as compensation. Enhancement and other conservation measures should
always be considered whenever possible.
Avoidance
The above impact assessment demonstrates that the Project will avoid encroachment into any
habitat of high ecological value during its construction, particularly to those key ecological
sensitive receivers such as Lantau South Country Park and EISs at Tong Fuk and Pui O.
Direct impacts on plant and wildlife species of conservation importance will also be avoided
as far as practicable during the detailed design. Permanent building structures, works and
storage areas have avoided in the habitat of high ecological value, as well as the proximity of
species of conversation importance (e.g. Aquilaria sinenis).
Construction impacts to marine ecological resources (i.e. natural rocky shore and subtidal
hard bottom habitats) and marine sensitive receivers (i.e. Shui Hau sandflat) have largely been
avoided by applying the HDD method for installing submarine outfall pipeline and through
proper planning design and execution of the works (i.e. optimisation of project construction
schedule/ sequence, using good engineering/ industry practice, timely completion of
construction works to reduce impact duration, etc.).
Indirect impacts on marine sensitive receivers due to the dispersion of sediment plume can be
avoided as the dredging works will be designed to confirm compliance with the assessment
criteria at sensitive receivers and control water quality impacts to within acceptable levels, an
water quality mitigation measures will be developed and implemented when required to
further avoid/ reduce potential impacts (See Section 4).
To summarise, this initial assessment of impacts demonstrates that impacts will largely be
avoided during the construction and operation of the proposed Project, particularly to the key
terrestrial and marine ecological sensitive receivers through the avoidance of direct and
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indirect impacts to ecological sensitive habitats and wildlife/ species of conservation
importance.
Minimisation
As part of the site selection process, three sewage pumping stations at Sha Tsui, Ham Tin and
Pui O Beach and a separate effluent pumping station initially at the coastal area of San Shek
Wan were deleted from the proposed sewerage scheme to minimise the overall footprint and
hence habitat loss and vegetation removal associated with the Project.
Trenchless construction method will be considered wherever necessary for laying the
proposed sewers. When the proposed pipepasses the EIS at Tong Fuk, the pipe laying will
adopt a bridge-mounted method without disturbing the stream bottom and riparian vegetation
along stream banks. Since there is sufficient headroom under the bridges, the pipes would not
touch the stream water. For the proposed gravity sewer across the EIS at Pui O, the pipe will
be laid by pipe-jacking method in which a jacking pit and a receiving pit will be constructed
on the land adjacent to the stream and about 0.5 m diameter of pipe will be jacked from the
jacking pit to the receiving pit without disturbing the stream and riparian vegetation as the pits
are located at sufficient distance (at least 5 m) from the stream banks and the surrounding
areas are free from riparian vegetation. The pipe will be constructed underground below the
Pui O EIS and kept clear distance at least 2 m below the stream bed. The implementation of
pipe laying works by using pipe-jacking method will be scheduled to dry season. The
construction and operation of the pipe will not cause change in water level as the substratum
above the tunnel and the tunnel will be impervious to gravitational flows of stream water. As
the scale of works (i.e. the pipe is at 0.5 m in diameter and 5 m long) is small and there will be
sufficient distance below the stream bed, the vibration arisen from the pipe-jacking is minor.
By using such construction method as well as the implementation of good practice to control
site run-off (see Section 4.9.1 for detailed mitigation measures to control construction site
runoff and drainage), the potential impact on the water table and ecology of the EIS is
predicted to be minor. By using such construction method as well as the implementation of
good construction practices, the potential impact on these EISs and other sites of conservation
importance will be minimised.
The present alignment of trunk sewers and rising mains overlaps with the main roads and
accesses of South Lantau. The sites of the proposed and alternative SPSs and STW will be
located within disturbed area as much as practicable. If habitats such as plantation,
shrubland-grassland and cultivated land are unavoidably affected, only the lands in close
vicinity to developed area will be taken to minimise the habitat fragmentation and isolation
arising from the construction of Project.
The above impact assessment demonstrates that the present alignment of the submarine
outfall is representing the shortest length (straight line of approximately 1,100 m long) to
avoid direct impacts on marine ecological resources. By having such alignment, the potential
impacts onto the subtidal hard and soft bottom habitats will be minimised.
Moreover, the use of HDD method is particular suitable for the construction of the proposed
submarine outfall from the STW because marine dredging and excavation would be minimal
(dredging area is estimated to be 39m x 33m around the diffuser) compared with conventional
submarine outfall pipeline installation methods (dredging area is about 16m wide x 1100m
long along the outfall), during which a trench in seabed is needed to be formed along the
entire alignment and backfilling is required after pipe laying. This HDD method will
minimise the potential impacts on water quality and marine ecological resources.
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To minimize the other disturbances of the construction works to the surrounding habitats and
associated wildlife, the following appropriate construction practices should be implemented as
far as practicable.
Erect fences along the boundary of the works area before the commencement of works to
prevent vehicle movements and encroachment of personnel onto adjacent areas;
Regularly check the work site boundaries to ensure that they are not breached and that
damage does not occur to surrounding areas;
Avoid any damage and disturbance, particularly those caused by filling and illegal
dumping, to the surrounding habitats through proper management of waste disposal;
Reinstate temporarily affected areas, particularly the habitats of plantation and shrubland-
grassland immediately after completion of construction works, through on-site tree/shrub
planting. The tree/shrub species will be chosen with reference to those in the surrounding
area (See Annex 5B – Table A2); and
A closed grab dredger will be used to dredge down about -11mPD which is approximately
6m below the current seabed and there will be no excessive dredging.
For emergency discharge in operation phase, an Emergency Response Plan shall be prepared
and implemented to cope with emergency discharge of untreated sewage. In brief, standby
facilities (i.e. main treatment units and accessories/ equipment parts) and dual power supply
(if dual power supply is available) would be provided to secure electrical power supply. In
addition, adequate emergency storage for SPSs and STW (see Sections 3.4.1 – 3.4.2) will be
provided. Regular inspection and maintenance should be carried out to prevent equipment
failure by a maintenance crew organized by DSD/ST2 - regular inspection team which will
station in San Shek Wan STW. Existing mobile team (except regular inspection team of
DSD) from Ma Wan STW will be responsible to backup the regular team in non-office hours.
Emergency team (except regular inspection team and existing mobile team of DSD) will assist
the existing mobile team to handle the situation in order to reduce the maintenance time in
non-office hour. Relevant government departments including EPD, LCSD and DSD shall be
informed by the STW operator as soon as possible of any emergency discharge of untreated
sewage. DSD is committed to repair the STW and SPSs as soon as practicable usually within
6 hours including time of travelling and repairing.
Compensation
Approximately of 0.52 to 0.55 ha of mixed woodland with moderate ecological value will be
lost due to construction of the San Shek Wan STW, San Shek Wan SPS (Proposed and
Alternative Sites) and their associated access roads. The loss of mixed woodland will be
compensated at suitable areas within the site boundary of the San Shek Wan STW and its
close proximity (Figure 5.9a & Figure 5.9i). Approximately, a total of 1.11 ha will be
compensated through compensatory woodland (Table 5.34).
Table 5.34 – Approximate Area of Compensatory Woodland Location Loss of Mixed Woodland (ha) Compensatory Woodland (ha)
San Shek Wan STW 0.38 0.11
Shui Hau Trunk SPS - -
Tong Fuk Trunk SPS - -
Cheung Fu Street Trunk SPS - -
Outlying Islands Sewerage Stage 2 –
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5-51 B&V / ERM
Location Loss of Mixed Woodland (ha) Compensatory Woodland (ha)
Cheung Sha Trunk SPS - -
San Shek Wan (Proposed) 0.14 -
San Shek Wan (Alternative)* 0.17 -
Pui O SPS - -
Proposed area for woodland compensation –
hillside to the southwest of San Shek Wan
STW
- 1
Total Area (ha) 0.52 to 0.55* 1.11
*Note:
Area of Woodland Loss at Proposed San Shek Wan SPS = 0.52 ha
Area of Woodland Loss at Alternative Site of San Shek Wan SPS = 0.55 ha
Within the site boundary of the San Shek Wan STW about 0.11 ha of land will be reserved for
planting as a compensatory woodland. An area of approximately 1 ha of hillside to the
southwest of the San Shek Wan STW will be established by the project proponent (i.e. DSD)
or its engaged consultant/ contractor as a compensatory woodland. This area is on a gently
sloping hillside (approx. 12 – 14 in degree) and is identified as shrubland-grassland habitat. It
is considered that this area is suitable for woodland compensation, providing connectivity to
existing mixed woodland in the area. Also this hillside area in general does not require
clearance of existing woodland and exotic species can be selectively removed if
needed. During tree planting for woodland compensation, existing native trees and shrubs in
the planting area will be preserved as far as possible. Planting near roadside and within the
nearby woodland area will be avoided. The project proponent (i.e. DSD) will be responsible
for the establishment and maintenance of approximately 1.11 ha compensatory woodland area
during the first 10 years of its establishment. It is expected that after 10 years, with proper
maintenance the woodland would be self-sustained and will be passed to relevant government
department (e.g. Lands Department) for maintenance per existing arrangement for
government land. Overall, the loss of up to 0.55 ha of mixed woodland from the Project is
proposed to be compensated in areas of about two times of the areas affected (about 0.11 ha
around the San Shek Wan STW and 1 ha in the hillside to the southwest of San Shek Wan
STW). Details for the compensatory woodland planting will be developed in a woodland
compensation proposal as part of the EM&A programme, in which the boundary of the
proposed woodland compensation area will be further refined.
Species proposed for planting are pioneer native tree and shrub species often present in
natural woodlands in the Study Area, including a number of shrub species know to be of value
in providing food for native fauna. Location for the proposed compensatory woodland is
illustrated in Figure 5.9a and Figure 5.9i. Proposed native species for woodland
compensation include:
Native trees:
Alangium chinense
Celtis sinensis
Mallotus paniculatus
Native shrubs:
Ilex asprella
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-52 B&V / ERM
Melastoma candidum
Psychotria asiatica
For the trees of Aquilaria sinensis found in the San Shek Wan SPS (Alternative site) and San
Shek Wan STW, transplantation plan will be developed accordingly. Trees shall be retained
and transplanted where practical, prime location would be at the compensatory woodland at
San Shek Wan STW.
Since habitat loss due to other land-based construction and marine dredging works for laying
the submarine outfall of the Project only occurs on the habitats of low or low to moderate
ecological value, where no species of conservation importance were recorded. Given that the
scale of marine works has been significantly reduced by adopting the HDD construction
method and the impact severity is evaluated to be low, other specific mitigation measure
including ecological compensation is not required from the marine ecology point of view.
5.9 Cumulative Ecological Impact
A number of interfacing projects in southern Lantau area is summarized as follows.
PWP No. 257WC – Siu Ho Wan Water Treatment Works Extension – Pui O Raw Water
Pumping Stations and Associated Mainlaying (WSD/Design)
Agreement No. CE 38/2007 (CE) – Planning and Engineering Study of Private Housing
Development at Cheung Sha, Lantau – Feasibility Study (CEDD/HKI&I)
Agreement No. CE 11/2008 (WS) – Replacement and Rehabilitation of Water Mains
Stage 4 (WSD/CM)
CE 29/2008 (EP) – Engineering Investigation and Environmental Studies for Integrated
Waste Management Facilities Phase 1 – Feasibility Study (EPD/IP)
Agreement No. 4600003274 – Cable Route Consultancy Services along Chi Ma Wan Road
(CLP)
RPIS IS009 – Construction of Vehicular Access at Pui O San Wai Tsuen, Lantau Island
(HyD/Works)
RPIS IS005 – Construction of Car Park at Pui O, Lantau Island (HyD/Works)
Agreement No. CE 15/2010 (DS) – Upgrading of Cheung Chau and Tai O Sewage
Collection, Treatment and Disposal Facilities (DSD/CM)
Agreement No. 4600003274 – Cable Route Consultancy Services along Chi Ma Wan Road
(CLP)
However, due to unavailable/ non-overlapping project programme or sufficient distance away
from the current Project Site, none of these projects is considered as concurrent projects of
this Project (Section 3.7). Moreover, all these projects will implement necessary mitigation
measures to minimise potential ecological impacts. Therefore associated cumulative
ecological impact is not considered to be significant.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-53 B&V / ERM
5.10 Residual Impact
As a result of land-based construction activities, up to 0.52 to 0.55 ha mixed woodland, 0.20
ha of plantation, 0.19 ha of shrubland-grassland, 0.04 ha of cultivated land and 0.22 ha of
urbanised/disturbed area would be permanently lost due to the Project. The affected habitats
are considered to be of low or low to moderate or moderate ecological values. With the
implementation of the recommended mitigation measures discussed in Section 5.8, the loss of
mixed woodland and trees of the protected plant species Aquilaria sinensis will be
compensated and transplanted, respectively. It is anticipated that all
potential ecological impacts will be reduced to an acceptable level. Therefore, no adverse
residual impact due to the construction of proposed sewers, rising mains, SPSs and STW is
expected from the aspect of terrestrial ecology.
In terms of marine-based construction works, approximately 0.13 ha of subtidal soft bottom
habitats of low to moderate ecological value will be lost due to the marine dredging activity.
No unacceptable residual impacts are anticipated as these habitats.
5.11 Environmental Monitoring & Audit (EM&A)
Terrestrial Ecology
Woodland compensation to mitigate for the loss of mixed woodland due to the construction of
the San Shek Wan STW, San Shek Wan SPS (Proposed and Alternative Sites) and their
associated access roads is recommended to fully compensate the loss of mixed woodland.
Establishment and after-establishment caring measures of the compensatory mixed woodland
are proposed for this Project. Details for the woodland compensation, including planting
species, will be developed in a woodland compensation proposal as part of the EM&A
programme.
For the affected individuals of Aquilaria sinensis at San Shek Wan SPS Alternative Site and
STW, transplantation plan will be developed, including an EM&A programme for monitoring
the transplantation of the tree individuals.
Marine Ecology
Construction Phase
During the construction phase, the following EM&A measures will be undertaken to verify
the predictions in the EIA and ensure the environmental acceptability of the construction
works. Water quality impacts will be monitored and checked through the implementation of a
Water Quality EM&A programme (refer to Section 4 for details). The monitoring and control
of water quality impacts will also serve to avoid unacceptable impacts to marine ecological
resources.
Operation Phase
The assessment presented above indicates that unacceptable operation phase impacts are not
expected to occur to marine ecological resources. No marine ecology specific operational
phase monitoring is considered necessary. The monitoring and control of water quality will
also serve to avoid unacceptable impacts to marine ecological resources.
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-54 B&V / ERM
5.12 Conclusions
This Section of the EIA has described the potential terrestrial and marine ecological impacts
associated with the construction and operation of the Project in South Lantau. The purpose of
the assessment is to evaluate the acceptability of predicted impacts to terrestrial and marine
ecological resources and sensitive receivers. Findings of literature review and dedicated
baseline field surveys have provided information for the evaluation of species of conservation
importance and ecological importance of various habitats within the Study Area as well as in
the Project Site.
A total of 15 habitat types were identified within the Study Area. They are terrestrial habitats
(i.e. Fung Shui woodland, mixed woodland, plantation, shrubland-grassland, cultivated land,
marsh, stream/channel and urbanised/disturbed area) and coastal habitats (i.e. sandflat,
mangrove, rocky shore, sandy shore, subtidal hard bottom and soft bottom habitats and
coastal/ marine waters), among which Fung Shui woodland, marsh, stream/ channel,
mangrove and sandflat are of moderate to high ecological value; mixed woodland is of
moderate ecological value, plantation, shrubland-grassland, rocky shore, subtidal soft bottom
and coastal/ marine waters are of low to moderate ecological value; cultivated land,
urbanized/ disturbed area, sandy shore and subtidal hard bottom are of low ecological value.
Apart from this, a number of recognized ecologically important / sensitive sites are located
within the Study Area. These include Lantau South Country Park, Coastal Protection Area,
Green Belt, the mangroves in Pui O, Fung Shui woodlands in Tong Fuk and Shui Hau,
proposed SSSI in Shui Hau Wan, Ecologically Important Streams (EIS) in Pui O and Tong
Fuk and horseshoe crab nursery ground in Shui Hau.
Regarding to species of conservation importance, seven flora species (i.e. Incense Tree
Aquilaria sinensis, Hong Kong Pavetta Pavetta hongkongensis, Silver-back Artocarpus
Artocarpus hypargyreus, Water Shamrock Marsilea quadrifolia, Water Spangles Salvinia
natans, Luofushan Joint-fir Gnetum luofuense and Zoysia sinica), one mammal species (i.e.
Japanese Pipistrelle Pipistrellus abramus), five bird species (i.e. Reef Egret Egretta sacra,
Black Kite Milvus migrans, Collared Scops Owl Otus lettia, Greater Coucal Centropus
sinensis and Hwamei Garrulax canorus), one amphibian species (i.e. Chinese Bullfrog
Hoplobatrachus chinensis), one reptile species (i.e. Copperhead Racer Elaphe radiata), seven
fish species (i.e. Japanese eel Anguilla japonica, Predaceous Chub Parazacco spilurus, Eye-
spotted puffer Takifugu ocellatus, Sleepy goby Psammogobius biocellatus, Indo-pacific
tropical sand goby Favonigobius reichei, Small snakehead Channa asiatica and Spotty band
goby Glossogobius olivaceus), one crustacean species (Pseudosesarma patshuni), one hard
coral species (i.e. Oulastrea crispata) and one Horseshoe Crab species (i.e. Tachypleus
tridnetatus) were recorded during the field baseline surveys. But none of these species were
found within the Project Site, except for the Incense Tree Aquilaria sinensis which was
recorded at San Shek Wan SPS Alternative Site and San Shek Wan STW. During the
construction phase, construction activities may cause direct ecological impacts including
habitat loss and vegetation removal, whereas indirect impacts on wildlife include the changes
in water quality. Potential impacts of increased human activities and other disturbances due
to the Project construction would not be significant provided that regular checks on
construction site practices and boundaries will be conducted. In addition, in the view of the
availability of surrounding similar habitats, the potential impact on wildlife especially on the
species of conservation importance as a result of habitat fragmentation and isolation is
considered to be minimal.
Habitat loss, which is the main terrestrial ecological impact arising from the Project, will
primarily occur in habitats of low and low to moderate ecological values, and approximately
Outlying Islands Sewerage Stage 2 –
South Lantau Sewerage Works
5-55 B&V / ERM
0.52 – 0.55 ha of mixed woodland of moderate ecological value will be lost due to the
construction of the Proposed/ Alternative Site of San Shek Wan SPS and San Shek Wan STW
including their associated access roads. Impact to mixed woodland and associated flora of
conservation importance (the Incense Tree Aquilaria sinensis) will be compensated by
woodland compensation and transplantation. For marine ecological impact, habitat loss/
disturbance of subtidal soft bottom habitat which is of low ecological value (within the
Project footprint) will also arise from minor marine dredging activity for installing the
submarine diffuser and there will be potential burial of benthic organisms. Potential impacts
on subtidal hard bottom habitat (including corals) will be impacted temporarily due to the
deterioration of water quality arisen from minor marine dredging works. And for the sites of
conservation importance, most of these sites within the Study Area will not be affected by the
Project.
With the implementation of the proposed mitigation measures, no adverse residual impact due
to the land-based and marine-based construction of proposed sewers, rising mains, SPSs and
STW and submarine outfall is expected.