8. ECOLOGICAL IMPACT

8.1 Introduction

8.1.1.1 The upgrading and expansion of San Wai Sewage Treatment Works (STW) and expansion of Ha Tsuen Pumping Station (the Project) are part of the scheme recommended under the "Review of Yuen Long and Kam Tin Sewerage and Sewage Treatment requirements". The Project covers expanding and upgrading San Wai STW, constructing and operating an emergency outfall culvert to nearby drainage channel, and expanding Ha Tsuen Pumping Station. Figure 1.3 shows the locations of the key items of this project.

8.1.1.2 The "Study Area" for terrestrial ecological impact assessment is defined as the area 500m either side of and along the full length of the Project boundary. The assessment was carried out by literature review supplemented by field surveys. The objective of the ecological survey was to undertake baseline survey work to record ecological data within the Study Area and to establish the ecological profile for incorporation into the EIA. Field surveys were designed to fill data gaps which would prevent an adequate assessment of the project's impacts upon ecology and the development of appropriate mitigation measures. For marine ecology, the assessment was carried out by literature review, and the Assessment Area covered the Deep Bay Water Control Zone (WCZ), the North Western WCZ and the Western Buffer WCZ.

8.1.1.3 The ecological impact assessment fulfilled the related requirements of the EIA Study Brief No. ESB-059/2000, particularly Section 3.4.6 of the EIA Study Brief, as well as the technical requirements of the Technical Memorandum on the EIA Process (EIAO-TM).

8.2 Legislation, Policies, Plans, Standards and Criteria

8.2.1.1 Local Ordinances governing the protection of wildlife in Hong Kong include:

· Forests and Countryside Ordinance (Cap. 96), and Forestry Regulations
· Wild Animals Protection Ordinance (Cap. 170)
· Animals and Plants (Protection of Endangered Species) Ordinance (Cap.187)
· Marine Parks Ordinance (Cap. 476)
· Environmental Impact Assessment Ordinance (Cap. 499) and associated Technical Memorandum on Environmental Impact Assessment Process

8.2.1.2 This study also takes note of the following relevant international agreements:

· Convention on Wetlands of International Importance Especially as Waterfowl Habitat ("Ramsar Convention")
· Convention on the Conservation of Migratory Species of Wild Animals ("Bonn Convention")
· Convention on International Trade in Endangered Species of Wild Fauna and Flora ("CITES")
· Convention on Biological Diversity

8.3 Recognised Sites of Conservation Importance

8.3.1.1 No Conservation Area or Green Belt is zoned within the Study Area for terrestrial ecology. No recognised sites of conservation interest such as Country Parks, Sites of Special Scientific Interest (SSSIs), or Special Areas are located in the Study Area for terrestrial ecology. The Lung Kwu Chau, Tree Island & Sha Chau SSSI designated for ornithological interest is located within the Assessment Area for marine ecology, this SSSI was indeed far outside the Study Area for terrestrial ecology (over 10km). It would not be affected by the Project.

8.3.1.2 The Sha Chau Lung Kwu Chau Marine Park is located in the North Western Water Control Zone which is part of the Assessment Area for marine ecology. This marine park is the only designated site of marine conservation importance in the Assessment Area for marine ecology. Despite the Lung Kwu Chau, Tree Island & Sha Chau SSSI is located within the Assessment Area, this SSSI was designated for ornithological interest. It is therefore not considered as a recognized site of marine conservation importance.

8.4 Assessment Methodology

8.4.1 Introduction

8.4.1.1 A literature review was conducted of the ecological conditions within the Study Area. The review included government and private sector reports, as well as unpublished information, including the following:

· Agreement No. CE 66/96 - Planning and Development Study on North West New Territories Technical Paper No. 13 Environmental Impact Assessment (Binnie Black & Veatch (HK) Ltd. 2000)
· Feasibility Study for Additional Cross-border Links Stage 2: Investigations on Environment, Ecology, Land Use Planning, Land Acquisition, Economic/Financial Viability and Preliminary Project Feasibility/Preliminary Design. Final Report on Ecology Studies Technical Note TNE4 (Mouchel Asia Environmental 1999)
· Agreement No. CE 109/98. Deep Bay Link Investigation and Preliminary Design. Technical Paper No. 2 Coastal Boundary Crossing Facilities and Hung Shui Kiu Short Tunnel Feasibility Study (Ove Arup & Partners (HK) Ltd. 2001)
· Results of biodiversity surveys of Hong Kong flora carried out by University of Hong Kong (Xing et al. 2000, Siu 2000)
· Porcupine! (Newsletters of Department of Ecology and Biodiversity, University of Hong Kong) for sightings of flora and fauna
· Results of "Hong Kong Breeding Bird Survey 1993-1996" in Avifauna of Hong Kong (Carey et al. 2001)

8.4.2 Habitats and Vegetation Survey

8.4.2.1 A reconnaissance survey was performed at the outset of the study to verify habitats and to select representative habitats for vegetation surveys. Special attention was paid to areas to be directly impacted by the proposed emergency bypass culvert alignments. Detailed surveys were then performed to describe habitats and record plant species with their relative abundance by habitat. Efforts were made to find species protected under local regulations or known to be uncommon or rare on a regional or territorial basis. The terminology used for conservation status of plant species followed Xing et al. (2000). Colour photographs were taken of all terrestrial habitat types surveyed and other features or species of ecological or conversation importance. Field surveys were carried out on 21 September 2001 and 28 November 2001 and 6 February 2002.

8.4.3 Bird Survey

8.4.3.1 A reconnaissance survey was performed at the outset of the study to select representative habitats for bird surveys. Quantitative surveys were conducted monthly during the study period (29 August 2001, 17 September 2001, 19 October 2001, 20 November 2001, 21 December 2001, 18 January 2002, 19 February 2002). Birds in selected fishponds were identified and counted. Bird communities in cultivated lands, orchard, grass-shrubland were sampled using the point count method. Ten minutes were spent on each counting point. All birds seen or heard within 30m from each point were counted and identified to species where possible. Ornithological nomenclature followed Viney et al. (1996). Bird species outside survey points but within the Study Area were also searched and recorded, to supplement the findings from point count surveys and produce a complete species list of the Study Area. Signs showing breeding (e.g., nests, recently fledged juveniles) within the study area were also recorded. Commonness and distribution of bird species in Hong Kong follows Viney et al. (1996), rarity and protection status of birds follows Zheng and Wang (1998).

8.4.4 Other Land Fauna Survey

8.4.4.1 Surveys of terrestrial fauna other than birds in the Study Area were conducted once in wet season (21 September 2001) and once in dry season (3 January 2002).

8.4.4.2 Dragonflies and butterflies seen within the Study Area were identified to species level where possible and recorded. Special attention was paid to areas with higher potential to support these animals, such as ponds, marsh and streams. In this report nomenclature for butterflies follows Walthew (1997) and dragonfly nomenclature follows Wilson (1997).

8.4.4.3 Mammals were surveyed by recording direct sightings and by searching for and recording tracks, faecal remains and burrows. Nomenclature for mammals follows Reels (1996) and Wilson and Reeder (1992).

8.4.4.4 Active searches for reptiles and amphibians were conducted in representative habitats. Herpetofauna (amphibians and reptiles) seen, and anurans (frogs and toads) heard within the Study Area were recorded. Nomenclature used in this report for reptiles follows Karsen et al. (1998) while that for amphibians follows Lau and Dudgeon (1999).

8.4.5 Aquatic Fauna Survey

8.4.5.1 Aquatic surveys were conducted in wet and dry seasons. The surveys covered natural stream courses and man-made drainage channels within the Study Area. Colour photos were taken, and aquatic fauna was studied by direct observation and active searching.

8.5 Baseline Conditions

8.5.1 Habitats and Vegetation Survey

Literature Review

8.5.1.1 Two locally rare plant species, Rubus pinnatisepalus and Dioscorea pentaphylla were recorded at Ha Tsuen during the biodiversity surveys of Hong Kong flora (Xing et al., 2000) but their exact locations are not known. Rubus pinnatisepalus is a climbing shrub found in grassland and shrubland habitat, while Dioscorea pentaphylla is a climber recorded in shrubland and forest (ibid.). These two species were not recorded during the field surveys for the current study.

8.5.1.2 No plants protected under the local regulations or known to be rare were recorded in previous EIAs covering the current study area.

Survey Results

8.5.1.3 Most of the Study Area, particularly the area to be directly affected by the proposed Project is highly urbanised and degraded by existing and on-going development, including container storage areas, village housing and roads.

8.5.1.4 Habitats found within the Study Area include mixed woodland, grass-shrubland, cultivated land, fishpond (active and abandoned), cultivated land (active and abandoned), orchards, stream channel/nullah, and disturbed/urbanised areas (Figures 8.1 and 8.2). Habitat types and delineation are in general not affected by seasonality. It should be noted, however, that due to the change in human practices, the status of cultivated land and fishponds is prone to change. Active and abandoned cultivation, in particular, is typically interspersed with one another or with village houses. For this reason these two categories were mapped together as cultivated land (active and abandoned). Active and abandoned fishponds, on the other hand, were mapped separately due to their discrete boundaries, although plant species (mostly on pond bunds) for both types of ponds were recorded simultaneously due to similar vegetation composition. More habitats were converted to container storage areas during the time of surveys and therefore the habitat types changed continuously. The habitat map (Figure 8.1) reflects mapping based upon 2001 aerial photographs and results of field surveys through February 2002.

8.5.1.5 The "Important Habitats Where an Ecological Assessment Will Be Necessary" listed in Note 1, Appendix A, Annex 16 to the EIAO-TM existing in or near the Study Area are:

· woodlands larger than 1 ha in size (mixed plantation woodland)
· wetlands larger than 1 ha in size (fishponds)

8.5.1.6 A total of 179 plant species was recorded within the Study Area, 77 of which are exotic species (Appendix 8A). No plant species protected under local regulations or known to be rare was recorded. Table 8.1 lists the area of each habitat type recorded within the Study Area.

Table 8.1 Habitat types recorded within the Study Area

8.5.1.7 Mixed Woodland: Isolated mixed woodlands were scattered on hillsides and along roads within the Study Area. The woodland species composition reflected a mixture of planted and native species. The woodland habitats were young in age, and had open canopies with shrub understoreys. Canopy species reached heights of 8-12 m and included Acacia confusa, Eucalyptus citriodora, Macaranga tanarius, Celtis tetrandra subsp. sinensis, and Melia azedarach while understorey species included Psychotria rubra, Litsea glutinosa and Litsea rotundifolia. The mixed woodland habitat within the Study Area had low to moderate species diversity compared with the other identified habitats. A total of 39 plant species was recorded in the woodland habitat.

8.5.1.8 Grass-shrubland: A continuous stand of grass-shrubland was found on hillsides on the west of the Study Area. The hillsides have historically been frequently burned, and were extensively burned by fires during the winter 2001-2002. The hillsides had low plant cover and were dominated by fire tolerant grasses and ferns, including Dicranopteris linearis and Neyraudia reynaudiana. Pioneer trees such as Rhus hypoleuca and Sapium sebiferum as well as fire-tolerant shrubs such as Rhodomyrtus tomentosa and Baeckea frutescens were also found to be colonising some of the sites. Grass-shrubland was characterised by medium species diversity and simple physical structure. A total of 77 plant species was recorded in these habitats.

8.5.1.9 Fishponds: Fishponds were scattered among urbanised/disturbed habitats within the Study Area. All fishponds appeared to be unmanaged: That is, no water pumps were seen, and most grassy bunds had not been trimmed. However, one pond supported domestic ducks. The two ponds to be lost due to expansion of San Wai Sewage Treatment Works were claimed by their owner to be under management (Figure 8.3). The absence of aerators and fish food combined with presence of dense vegetation on the pond bunds suggested that management is limited, and the ponds may only be harvested for domestic use. Some of the fishpond bunds were planted with trees including Melia azedarach, Macaranga tanarius, and Dimocarpus longan. Most bunds supported grasses and weeds including Mikania micrantha and Panicum maximum. Most of the ponds had open water, except for one pond that was overgrown by Eichhornia crassipes. A total of 27 plant species was recorded in this habitat type.

8.5.1.10 Cultivated Land and Orchard: Cultivated lands within the Study Area were mostly abandoned. Remnants of crops were found in abandoned fields together with grasses, herbs and weeds that naturally colonised the land. During the study period some abandoned fields were re-cultivated especially during Chinese New Year to produce flowers and vegetables. Orchards were mainly planted with Dimocarpus longan and Litchi chinensis, while some village-associated trees including Celtis tetrandra subsp. sinensis and Macaranga tanarius were also found. The cultivated land and orchard within the Study Area represents man-made habitat and is of little floristic importance or conservation concern.

8.5.1.11 Stream / Channel & Nullah: The main stream channel within the Study Area is the upper reach of the Tin Shui Wai Channel which discharges into Deep Bay. The channel is lined with concrete and lacks vegetation. A section of a small tributary feeding the Tin Shui Wai Channel and ditches draining cultivated lands had earthen banks. Ruderal species including Bidens pilosa and Panicum maximum as well as fruit trees including Dimocarpus longan and Mangifera indica colonised the stream bank. Plant diversity was low and recorded species are of little floristic importance or conservation concern.

8.5.1.12 Disturbed/Urbanised and Wasteland: Disturbed/Urbanised habitat consists mainly of container storage areas, village houses, roads, parks, and construction sites. Most plant species recorded within this habitat type are exotic species planted for landscaping purposes. Common roadside plantation trees include Melaleuca quinquenervia, Acacia confusa, and Celtis tetrandra subsp. sinensis. Planter boxes grown with a variety of landscaping trees, shrubs and herbs were also common along main roads. Village associated plantings include fruit trees (e.g. Dimocarpus longan and Clausena lansium) and native trees (e.g. Ficus hispida, Bridelia tomentosa, Celtis tetrandra subsp. sinensis). Most of these trees were planted in rows or as isolated individuals among houses. Wasteland was similar in nature but was covered by weedy species such as Urochloa mutica and Conyza canadensis possibly upon prolonged abandonment of areas disturbed by earth work. The ecological value of these habitats is minimal.

8.5.2 Bird Survey

Literature Review

8.5.2.1 Avifauna at rural locations 1 km SE of the Study Area was sampled during the field surveys for "Planning and Development Study on North West New Territories" (Binnie Black & Veatch 2000). Bird species of conservation concern included Buzzard Buteo buteo, Kestrel Falco tinnunculus, Buff-bellied Pipit Anthus rubescens, Daurian Starling Sturnus sturninus, Red-billed Starling S. sericeus and Lanceolated Warbler Locustella lanceolata. Buzzard and Kestrel are listed in Appendix 2 of CITES and are Class 2 Protected Animals in China (Zheng and Wang 1998). Kestrels and buzzards occur in widespread locations throughout Hong Kong and use a wide variety of open habitats in both rural and urban areas (Carey et al. 2001). Buff-bellied Pipit and Lanceolated Warbler are rare winter visitors (Viney et al. 1996). Buff-bellied Pipits frequent lowlying wetlands while Lanceolated Warblers favour margins of freshwater ponds (Viney et al. 1996, Carey et al. 2001). Daurian Starlings are rare passage migrants and most records come from the Deep Bay areas (Carey et al. 2001). Red-billed Starlings are abundant but localised winter visitors, and are mainly found in lowland areas (ibid.).

8.5.2.2 A total of 30 bird species was recorded at and near the Study Area during the Hong Kong Breeding Bird Survey organised by Hong Kong Bird Watching Society between 1993 and 1996 (Carey et al. 2001). Species of conservation concern included Bonelli's Eagle Hieraaetus fasciatus and Hwamei Garrulax canorus. Both are listed in Appendix 2 of CITES, and Bonelli's Eagle is a Class 2 Protected Animal in China (Zheng and Wang 1998). Bonelli's Eagle is a localised and rare resident, and is usually recorded in sparsely vegetated habitats (Carey et al. 2001). Hwamei is mainly a shrubland species, and is common and widespread in Hong Kong (ibid.).

8.5.2.3 Crested Serpent Eagle Spilornis cheela, Crested Goshawk Accipiter trivirgatus and Peregrine Falcon Falco peregrinus were recorded in cultivated lands in Ha Tsuen in July 1998 and February 1999 during field surveys for "Feasibility Study for Additional Cross-border Links Stage 2" (Mouchel 1999). These three species are Class 2 Protected Animals in China, and all are listed in Appendix 2 of CITES (Zheng and Wang 1998). Crested Serpent Eagle and Crested Goshawk are uncommon residents. Crested Serpent Eagle and Crested Goshawk are usually recorded in well-wooded areas (Carey et al. 2001). Peregrine Falcon is a rare resident and winter visitor, and occurs at widespread locations (ibid.).

8.5.2.4 Avifauna at the valley and hillside near the Ling To Temple was sampled during field surveys for "Deep Bay Link EIA" (Ove Arup & Partners (HK) Ltd. 2001). Bird species of conservation concern included Black-eared Kite Milvus lineatus, Crested Serpent Eagle, Chinese Goshawk Accipiter soloensis, Crested Goshawk, Kestrel, Emerald Dove Chalcophaps indica, Red-winged Crested Cuckoo Clamator coromandus, Greater Coucal Centropus sinensis, Lesser Coucal C. bengalensis, Red-headed Tit Aegithalos concinnus and Scarlet-backed Flowerpecker Dicaeum cruentatum. Black-eared Kite, Crested Serpent Eagle, Chinese Goshawk, Crested Goshawk, Kestrel, Greater Coucal and Lesser Coucal are Class 2 Protected Animals in China (Zheng and Wang 1998). Black-eared Kite, Crested Serpent Eagle, Chinese Goshawk, Crested Goshawk and Kestrel are listed in Appendix 2 of CITES (ibid.). Black-eared Kite is a very widespread species in Hong Kong and can be found in a wide variety of coastal and inland habitats, including urban areas (Carey et al. 2001). Chinese Goshawk is an uncommon passage migrant that is mainly recorded on lightly wooded hillsides or marshes in widespread locations (ibid.). Greater Coucal and Lesser Coucal are common residents. Greater Coucals inhabit a wide range of habitats, while Lesser Coucals mainly in grassy and shrubby hillsides. Emerald Dove, Red-winged Crested Cuckoo, Red-headed Tit and Scarlet-backed Flowerpecker are rare/uncommon in Hong Kong, and are found in a variety of wooded habitats. Red-headed Tits recorded in Hong Kong are not considered to be of wild origin and it is not likely that a feral population has established (ibid.).

Survey Results

8.5.2.5 Nine bird species were recorded in the two ponds within the proposed area for expansion of San Wai STW (Appendix 8B). Mean bird density was 2.3 birds ha-1. All recorded species are typical of wetland habitat, and all except Yellow Bittern Ixobrychus sinensis are common and widespread in Hong Kong (Carey et al. 2001). Yellow Bittern favors reedbed and mangrove habitats (ibid.). This species is an uncommon summer visitor, but local abundance rise markedly upon late August (ibid.). During autumn migration season, this species can be seen very easily in fishponds. Only one Yellow Bittern was recorded in the two ponds during the field surveys of this EIA study (August 2001) and that bird may be a passage migrant (Appendix 8B). Yellow Bittern, Chinese Pond Heron Ardeola bacchus, Little Egret Egretta garzetta and White-breasted Kingfisher Halcyon smyrnensis are considered of local/regional concern (Fellowes et al. 2002), but these species only occurred in low abundance in the two ponds (1 or 2 birds) during field surveys (Appendix 8B). Besides fishponds, these species also utilize a variety of wetland habitats (e.g., mangroves, wet cultivated lands). Chinese Pond Heron, Little Egret, Common Kingfisher and White-breasted Kingfisher even occur in urban areas (e.g., flood control channels, urban parks).

8.5.2.6 Fishponds are manmade habitats and primarily managed for economic returns, and do not necessarily process characteristics as important habitats for wetland birds. The two fishponds near the San Wai STW site supported dense vegetation on the pond bunds, and the bund slopes were steep (> 1:1). These features offer few perches for wading birds to feed on or from the pond shores. Water depths in the two ponds are probably deep (>2 m). Both water depth and shore slope of wetland habitats are important factors affecting bird uses. Shallow water depth and gentle shore slope (1:6 to 1:4) will result in both higher bird abundance and species richness (Street 1989, Kazantidis and Goutner 1996, Dimalexis and Pyrovetsi 1997, Kushlan 2000, Bancroft et al. 2002). The two ponds are isolated from other the continuous clumps of fishponds in northwest and north New Territories. In addition, disturbance from surrounding industrial developments and human residences is high. It has been shown that bird abundance in fishponds increase with distance to open storage (Aspinwall & Company 1997a). Uses of the two fishponds by both wetland and non-wetland birds are limited by these factors. The overall ecological value of the two ponds as bird habitats is ranked as low.

8.5.2.7 Bird species recorded in cultivated lands, fishponds, orchard and grass-shrubland in the Study Area are mostly common and widespread in Hong Kong and typical of disturbed habitats (e.g., Little Egret Egretta garzetta, Chinese Bulbul Pycnonotus sinensis) (Appendices 8C, D, E & F). Bird densities in these habitats were generally low, probably due to fragmentation and high human disturbance (Table 8.2). Data of the two fishponds near San Wai STW and those of other fishponds within the Study Area were separated, as the current disturbance level and the future potential impacts form the proposed Project around these two ponds would be different from those in the other surveyed fishponds. This would affect both bird abundance and species richness. An active nest of Magpie Pica pica was located in urbanised area within the Study Area in February 2002 (Figure 8.1). Magpie is common and widespread in Hong Kong, and can be found in urban areas (Viney et al. 1996).

Table 8.2  Bird communities in each type of habitat in the Study Area

8.5.2.8 Eight bird species were recorded in the Study Area during non-systematic surveys (Appendix 8G). Non-systematic surveys also covered mixed woodlands which is not suitable for quantitative surveys due to their small size and fragmented nature. All are widespread in distribution in Hong Kong (Viney et al. 1996). Buzzard is listed in Appendix 2 of CITES and is a Class 2 Protected Animal in China (Zheng and Wang 1998), and was soaring above grass-shrubland within the Study Area. Buzzards occur in widespread locations throughout Hong Kong and use a wide variety of open habitats in both rural and urban areas (Carey et al. 2001). Appendix 8H lists all birds recorded during field surveys for the current project.

8.5.2.9 A total of 15 wetland dependent bird species was recorded within the Study Area (e.g., Yellow Bittern, White-breasted Kingfisher) during the surveys (Appendix 8H). All the wetland species recorded within the Study Area are considered disturbance tolerant (e.g., Little Egret, White-breasted Waterhen Amaurornis phoenicurus). Five wetland dependent species were recorded in the two ponds near the San Wai STW and the abundance was very low (0.9 bird ha-1) (Appendix 8B), in comparison to less isolated and less disturbed ponds in nearby areas, Tsim Bei Tsui, in northwest New Territories (6.8 birds ha-1) (August 2001 - February 2002) (Hong Kong Bird Watching Society, unpubli. data). All these five species are widespread in distribution in Hong Kong (Carey et al. 2001). The low ecological importance of the two fishponds as wetland bird habitats was discussed in Section 8.5.2.6.

8.5.2.10 A small ardeid roost was located at an abandoned fishpond in the Study Area (Figure 8.1). There were five ardeid species in the roost (Table 8.3). Night Heron Nycticorax nycticorax was the dominant species. The average peak number of Night Herons in the Deep Bay area between 1989 and 2001 was 1568 birds (Young and Cha 1995, Carey 1998, 1999, 2000, 2001). The roosting population of Night Heron was about 1.4% of that in the Deep Bay area.

Table 8.3   Ardeid species recorded at a roost at an abandoned fishpond

8.5.3 Other Land Fauna Survey

Literature Review

8.5.3.1 All amphibian species recorded at and near the Study Area in previous surveys are of low conservation concern (e.g., Gunther's Frog Rana guentheri, Brown Tree Frog Polypedates megacephalus) (Binnie Black & Veatch 2000, Ove Arup & Partners (HK) Ltd. 2001).

8.5.3.2 Reptile species recorded near the Study Area and of conservation concern included Mountain Water Snake Sinonatrix percarinata, Checkered Keelback Xenochrophis piscator (Binnie Black & Veatch 2000) and Common Rat Snake Ptyas mucosus (Ove Arup & Partners (HK) Ltd. 2001). Mountain Water Snakes are uncommon in Hong Kong and are mainly found in rapid mountain streams (Karsen et al. 1998). Checkered Keelback is considered uncommon in Hong Kong, and is mainly found in lowland streams (ibid.). Common Rat Snake is listed in Appendix 2 of CITES (Zhao 1998), and occurs in a wide range of habitats (e.g., cultivated lands, shrubland) (Karsen et al. 1998).

8.5.3.3 All mammal species recorded at and near the Study Area are of low conservation concern (e.g., Spiny-haired Rat Nivienter fulvescens, Common Rat Rattus norvegicus and Sladen's Rat R. sladeni) (Binnie Black & Veatch 2000, Ove Arup & Partners (HK) Ltd. 2001).

8.5.3.4 Two uncommon dragonfly species Mnais mneme and Orthetrum triangulare melania were recorded at the stream in near Ling To Temple (Ove Arup & Partners (HK) Ltd. 2001). These two species are mainly found in woodland streams in Hong Kong (Wilson 1995).

8.5.3.5 All butterfly species recorded near the Study Area are locally common and widespread (e.g., Angled Castor Ariadne ariadne, Common Grass Yellow Eurema hecabe) (Binnie Black & Veatch 2000, Ove Arup & Partners (HK) Ltd. 2001).

Survey Results

8.5.3.6 Two amphibian species, Asian Common Toad Bufo melanostictus and Gunther's Frog, were recorded in cultivated lands in the Study Area during the field surveys. Both are common and widespread in Hong Kong (Lau and Dudgeon 1999). No amphibian was recorded in the two fishponds near the San Wai STW. Due to the presence of predaceous fishes and close to human disturbance, the two fishponds were not considered to be important amphibian habitats.

8.5.3.7 Three reptile species, Changeable Lizard Calotes versicolor, Chinese Skink Eumeces chinensis and Long-tailed Skink Mabuya longicaudata, were recorded in cultivated lands in the Study Area during the field surveys. All are common and widespread in Hong Kong (Karsen et al. 1998).

8.5.3.8 Burrows of rodents (Rattus spp.) were recorded on grassy hillsides within the Study Area. Rattus spp. are commonly found near residential areas and the species known to occur in Hong Kong are of low conservation concern. No direct sightings, tracks or other sign of mammals of conservation concern were observed in the Study Area during the field surveys.

8.5.3.9 All dragonflies and butterflies recorded in the study area (e.g., Wandering Glider Pantala flavescens, Common White Artogeia canidia) are of low conservation concern, and typical of disturbed areas (Appendices 8I & J). Only one species of butterfly (Great Eggfly Hypolimnas bolina) and two species of dragonflies (Ischnura senegalensis and Brachythemis contaminata) were recorded in the two fishponds near the San Wai STW. No recorded species is protected or known to be rare/endangered locally or regionally.

8.5.4 Aquatic Fauna Survey

Literature Review

8.5.4.1 Literature review revealed little information on aquatic fauna within the Study Area. The Ha Tsuen area was not included in the Hong Kong-wide stream fish survey conducted by Chong & Dudgeon (1992).

8.5.4.2 An uncommon freshwater fish Rhodeus ocellatus, together with the symbiotic Swan Mussel, was found in the upper course of Kam Tin River near Tai Lam Country Park (Cheung 1998; Dudgeon 1999). However, the record was outside and some distance away from the Study Area.

8.5.4.3 The section of Kam Tin River close to Kam Hing Wai was found to have a "very poor macrobenthic community" with only 2 to 4 species, dominated by oligochaetes (Binnie 1992). Catfish was sighted in the lower reach of the stream that is under tidal influence.

8.5.4.4 Mosquito fish Gambusia affinis and the Apple snail Pomacea lineata were recorded in the Kam Tin area, and 4 individuals of terrapins of unidentified species, which were probably exotic and imported for food, were observed in the Kam Tin River (Kam Tin Bypass, Binnie 1996).

Survey Results

8.5.4.5 The main natural stream within the Study Area was located upstream of and at some distance from the San Wai STW, the Ha Tsuen Pumping Station and all 4 alternative alignments of the emergency bypass culvert, and close to the 500m Study Area boundary.

8.5.4.6 The stream water downstream of the Ling To Monastery was in fair condition and clear. The stream was devoid of domestic sewage, but had been degraded by a recent road construction project that disturbed one of the seasonal tributaries. An atyid shrimp Caridina cantonensis was found in this stream and was moderately abundant.

8.5.4.7 The atyid shrimp Caridina cantonensis is the most widespread member among the three congeneric species in Hong Kong (Cai and Ng 1999). C. cantonensis is usually found in the mid- to upper reaches of natural streams. This aquatic species is a typical component of the stream fauna in fair to good quality waters in Hong Kong. The species is of no conservation concern.

8.5.4.8 The Apple Snail Pomacea lineata was found in the lower part of the natural stream that connected to a culvert discharging to Tin Shui Wai Channel at the main access road to the San Wai STW. Apple Snails are South American in origin. The species was first introduced into China for pond culture, but like Tilapia, has become naturalised. In Hong Kong Apple Snails are not grown for use as food. Pomacea lineata are considered an agricultural pest known to damage vegetables. This animal was also recorded in nearby cultivated land. A previous study reported its abundance in Kam Tin area agricultural fields (Binnie 1996).

8.5.4.9 The dominant aquatic organism found in the drainage channels during both the wet season and dry season surveys was the widespread Tilapia Oreochromis spp. No other aquatic macrofauna was recorded. Tilapia were concentrated at the furthest downstream reach of the channel at the location of the outfall for Alternative 4 of the proposed emergency bypass culvert.

8.5.4.10 The predominance of Tilapia was expected since they were found to be abundant in several locations in the nearby Kam Tin River in previous studies.

8.5.4.11 Tilapia were first introduced to China in the early 1970s for pond culture. In Hong Kong, wild Tilapia are believed to be of pond stock origin. They are highly adaptable, which enables their success at colonising habitats that most native fish species cannot survive, such as polluted stream courses with low oxygen levels. Although they mainly feed on plant material, Tilapia can consume virtually every kind of organic material including zooplankton, phytoplankton, aquatic invertebrates, detritus and sediments. They are also capable of naturally breeding in many types of water bodies including small, stagnant ponds. In many cases, Tilapia dominates the aquatic habitats and are the only fish species found.

8.5.4.12 There was no major difference in the aquatic fauna communities observed between the wet season and dry season in the present survey. Results of the stream survey are summarised in Table 8.4.

Table 8.4   Results of the stream survey for the present study

Abundance: +++: Abundant, ++: Common, +: Occasional

8.5.5 Marine Ecology

8.5.5.1 The Chinese White Dolphin Sousa chinensis is the only cetacean likely to be found in the Assessment Area for marine ecology. The Sha Chau Lung Kwu Chau Marine Park is located in the North Western Water Control Zone which is part of the Assessment Area for marine ecology. This marine park was designated in November 1996. It covers a sea area of 1,200 hectares and is one of the most important dolphin habitats in Hong Kong. Finless Porpoises Neophocaena phocaenoides usually occurs in the southern and eastern waters of Hong Kong, outside the Assessment Area.

8.5.5.2 S. chinensis is protected by law in the Hong Kong Special Administrative Region (HKSAR). It is a CITES Appendix I species and a Class I protected species in Mainland China (Huang 1997, Parsons 1997). S. chinensis has been the subject of considerable local study in the past few years (see e.g. Jefferson 1998). Results of systematic transect surveys over several years show that the range of S. chinensis in HKSAR is centred on the waters around north and west Lantau and Urmston Road (Jefferson 1998). It appears that Lingdingyang proper is the core area for this species in the Pearl River Estuary. This supposition is supported by the fact that the dolphins are seen almost exclusively in the western waters of Hong Kong and concentrated in the most estuarine-influenced north Lantau waters.

8.5.5.3 The distribution of Chinese White Dolphin spreads eastward and southward during summer and autumn months but concentrates in the mouth of Deep Bay during winter (Jefferson 1998). Dolphin surveys conducted for the Study on Tonggu Waterway (Scott Wilson 1998) produced some sightings relatively close to Tai O in all seasons.

8.5.5.4 Land-based visual surveys were conducted to estimate dolphin use of Tai O Bay in 1999 (Scott 2000). Surveys were conducted both in the morning and in the afternoon. Survey time was approximately evenly divided between flood tides and ebb tides. A total of 7 sightings were made during the survey. Group size ranged from 1 to 3 including adults, subadults and one juvenile. Age classes of the dolphins were estimated by their colouration. 4 classes are used: 1) unspotted calf, 2) mottled juvenile, 3) spotted adult and 4) unspotted adult. Two sightings occurred near the mouth of the bay. Five sightings were made outside the bay (at least 700 m to the west or north-west of Tai O Bay).

8.5.5.5 The southeast limit of the distribution range of Chinese White Dolphin falls into the western end of Western Buffer WCZ. There were 14 sightings of dolphins inside Western Buffer WCZ between 1995 and 1998 (Jefferson 1998). Most of these sightings were recorded in the coastal waters of Lantau Island. Only one sighting was made between Lantau and Tsing Yi and another one between Kau Yee Chau and Hong Kong Island.

8.5.5.6 Established coral communities of any size are regarded as important habitat types in Hong Kong as defined in Annex 8 of EIAO-TM. Hard corals, however, are vulnerable and prefer clear oceanic water. The Deep Bay WCZ and North Western WCZ are not suitable for coral colonisation due to the lower salinity and higher turbidity. According to findings of recent studies commissioned by AFCD, corals also occur in western side of Hong Kong including areas like Peng Chau, Hei Ling Chau and Cheung Chau. They are found in shallow water along the coastline. The coverage of corals in this region is low (less than 5%, and is the lowest compared with other regions in Hong Kong. Instead of forming coral communities, they exist as sparse isolated patches, composed of extremely tolerant and hardy species. The corals here represent a small subset of those present in the east, where corals are much more diverse and abundant.

8.5.5.7 At the southeastern end of the Western Buffer WCZ, five sites were surveyed during an extensive dive survey in Hong Kong waters (Binnie, 1995). Ap Lei Chau, Magazine Island, south Telegraph Bay and north Telegraph Bay were all assigned low conservation value in terms of the abundance and diversity of hard corals and soft corals. However, rich soft corals and sea fans were found at Pak Kok. Hard corals were also recorded in median abundance. No sites were surveyed inside the Deep Bay and North Western WCZs by the Binnie's study (1995).

8.5.5.8 During a trawl survey for epibenthic community, sea pens and gorgonians were recorded at south Tsing Yi (ERM, 1995). Soft corals and gorgonians do not contain zooxanthellae and do not require light penetration for photosynthesis. They are thus more widely distributed in Hong Kong and can be found in areas of higher turbidity.

8.5.5.9 Horseshoe crabs are an ancient and taxonomically isolated group (class Merostomata, sub-class Xiphosura) related to spiders, ticks and mites. Three species occur in HKSAR waters: Tachypleus tridentatus, T. gigas and Carcinoscorpius rotundicauda (Chiu & Morton 1999). These represent all species known from the South China Sea, and three of four species known worldwide. Information on abundance of these species is limited, but Liang and Zhou (1987) note that in surveys in Beibu Bay, Guangxi/Guangdong, T. tridentatus made up 90% of the catch and the other two species together made up only 10%.

8.5.5.10 Horseshoe crabs, most commonly T. tridentatus, have been recorded in the HKSAR at Tap Shek Kok, Sha Chau, Tai Po and Peng Chau, though there are no recent records from any of these sites (Huang 1997). C. rotundicauda was recorded in 1997 from Ma Wan Chung, Lantau, at a site that would be lost to development of the Tung Chung New Town (ibid.). Horseshoe crabs have been seen in Port Shelter in recent years (Ecosystems Ltd., unpubl. data; Crow, and Molner pers. comm.), though at least some of these may have been animals released by Buddhists. The other areas where horseshoe crabs have been recorded in the HKSAR are on the shores of Outer Deep Bay and the waters around Black Point-Tap Shek Kok.

8.5.5.11 Two species of horseshoe crab, Tachypleus gigas and Tachypleus tridentatus, have been recorded from trawl surveys at Tap Shek Kok just south of Lung Kwu Tan, and the beaches at Lung Kwu Sheung Tan and Lung Kwu Tan have been identified as potential breeding sites for T. gigas (ERL 1992, ERM 1993, Planning Department 1993, SWK 1993). Juvenile horseshoe crabs are seen by fishermen in the intertidal zone from Sheung Pak Nai to Ngau Hom Shek, but adults are seldom seen.

8.5.5.12 The habitat requirements of horseshoe crabs have been poorly documented worldwide. In Deep Bay the preferred habitat was identified as sandy to muddy intertidal zones, which appear to provide habitat for juveniles. Currently, Ha Pak Nai in Deep Bay, together with San Tau near Tung Chung and Shui Hau in South Lantau, are regarded as nursery sites for horseshoe crabs (Chiu & Morton 1999). Non-systematic surveys for horseshoe crabs were conducted along the coast of Outer Deep Bay from Ngau Hom Shek to Sheung Pak Nai for the Crosslinks2 EIA (Mouchel 1999). It was found that both adults and juveniles occur in Deep Bay but are in very small numbers. Horseshoe crabs occurred in the area in large numbers some 20 years ago, but probably have been extirpated by unsustainable harvest.

8.5.5.13 All three species of horseshoe crabs appear to be in population decline and are thought to be under severe pressure in the South China Sea, including HKSAR waters, due to habitat loss and overexploitation (Huang 1997). The conservation status of the three Indo-Pacific species is listed as "Data Deficient" by IUCN, indicating that existing knowledge is insufficient to determine whether they are threatened or endangered. Horseshoe crabs have been identified as species of potential conservation concern in the HKSAR.

8.5.5.14 Other nektonic marine communities in the Assessment Area are described in the chapter on Fisheries Impact Assessment.

8.6 Evaluation of Habitats and Species

8.6.1.1 Habitats found within the Study Area were evaluated in terms of ecological importance using the criteria set forth in Annex 8, Table 2 of the EIAO-TM. Ecological importance of the Study Area as a whole is summarised in Table 8.5. Most of the Study Area, particularly the area to be directly affected by the proposed Project, is highly urbanised and degraded by existing and on-going development, and its overall ecological value is low (Table 8.5). Individual habitats within the Assessment Area are also considered to be of little biodiversity conservation concern (Tables 8.6 - 8.12).

Table 8.5  Evaluation of ecological importance of the terrestrial habitats of the Study Area as a whole

Table 8.6  Evaluation of ecological importance of mixed woodland habitat

Table 8.7  Evaluation of ecological importance of grass-shrubland habitat

Table 8.8  Evaluation of ecological importance of cultivation habitat

Table 8.9  Evaluation of ecological importance of fishpond habitat (active and abandoned)

Table 8.10  Evaluation of ecological importance of stream habitat

Table 8.11  Evaluation of ecological importance of disturbed/urbanised/wasteland habitat

Table 8.12 Evaluation of ecological importance of marine habitat

8.6.1.2 In accordance with Table 3, Annex 8 of the EIAO-TM, the ecological value of species was assessed in terms of:
· Protection status;
· Species distribution; and
· Rarity.

8.6.1.3 Flora and most fauna recorded in the Study Area are typical of disturbed areas, and are of low conservation concern.

8.6.1.4 Wetland dependent birds, Buzzard, Chinese White Dolphin, horseshoe crab, as well as the soft corals, gorgonians and sea pens in Pak Kok and south Tsing Yi, are identified during field surveys and literature review as conservation concerns (Table 8.13).

Table 8.13 Species of conservation concern recorded in the Study Area and Assessment Area

8.7 Impact Identification and Assessment

8.7.1 Introduction

8.7.1.1 The significance of ecological impacts is evaluated based primarily on the criteria set forth in Table 1, Annex 8 of the EIAO-TM:
· habitat quality;
· species affected;
· size/abundance of habitats/organisms affected;
· duration of impacts;
· reversibility of impacts; and
· magnitude of environmental changes.

8.7.1.2 Impacts are generally ranked as "minor", "moderate" or "severe", although in a few cases a ranking of "minimal" (less than "minor") may be given. The ranking of a given impact will vary based on the criteria listed above. For example, an impact might be ranked as "minor" if it affected only common species and habitats, or if it affected only small numbers of individuals or small areas, whereas it might be ranked as "severe" if it affected rare species or habitats, large numbers of individuals or large areas. The major factors giving rise to a ranking are explained in the text. As noted in Annex 16 of the EIAO-TM, a degree of professional judgement is involved in the evaluation of impacts.

8.7.2 Construction Stage

Site Formation

8.7.2.1 The proposed expanded sites of San Wai STW and Ha Tsuen Pumping Station would cause the loss of 1.75 ha of fishponds, 0.01 ha of grassland, 0.29 ha of mixed woodland, 0.43 ha of wasteland and 9.48 ha of urbanised habitats (Table 8.14).

8.7.2.2 The major concern in the impact assessment would be the loss of fishponds. As discussed earlier Section 8.5.2.9, both species richness (5 species) and abundance (0.9 birds ha-1) of wetland dependent birds recorded in the two fishponds were low. Furthermore, fishponds are manmade habitats and primarily managed for economic returns, and do not necessarily process characteristics as important habitats for wetland birds. Both water depth and shore slope of wetland habitats are important factors affecting bird uses. Shallow water depth and gentle shore slope (1:6 to 1:4) in the retained pond area will result in both higher wetland bird abundance and species richness (Street 1989, Kazantidis and Goutner 1996, Dimalexis and Pyrovetsi 1997, Kushlan 2000, Bancroft et al. 2002). The two fishponds adjacent to the existing San Wai STW, however, supported dense vegetation on the pond bunds, and the bund slopes were steep (>1:1). These features offer few perches for wading birds to feed on or from the pond shores. Water depths in fishponds are generally deep (>2 m). In addition, disturbance from surrounding industrial activities namely the container yards and the open storage areas is high. Uses of the two fishponds by both wetland and non-wetland birds are limited by these factors. Other fauna species recorded in the two fishponds were of low conservation concern. The overall ecological value of the two ponds is therefore ranked as low in Section 8.6 above. No mitigation measures would be required for the fishpond loss.

8.7.2.3 Other habitats (Grassland, Wasteland, Urbanised, Mixed Woodland) and their associated flora and fauna are also of low ecological importance. No major influence in terms of ecological resources would be caused by the loss of these habitats. No mitigation measures are required.

8.7.2.4 Given the scale of the project and the lack of water bodies of conservation importance in the vicinity of the project boundary, impacts from site runoff would not be a major concern. Site runoff associated with site formation works and other construction works could be controlled by good site practices to an acceptable level.

8.7.2.5 The overall ecological impact from site formation is ranked as minor. Mitigation measures will be detailed in Section 8.8 below.

Table 8.14  Potential loss of habitat (ha) due to the expansion of Ha Tsuen Pumping Station and San Wai STW

8.7.2.6 The four alternative alignments of the proposed emergency bypass culvert differ little in terms of habitat loss and associated ecological impacts (Table 8.15). The potential ecological impacts of the emergency bypass culvert alignments are considered minor due to the highly disturbed nature and limited size of the habitats, and the low conservation concern for the associated flora to be lost. No location/habitat of conservation concern (e.g., the ardeid roost) will be lost.

Table 8.15 Potential loss of habitat to four alternative alignments of emergency bypass culvert during construction phase

* assuming a 10m wide work area

** assuming a 3.5m wide underground emergency bypass culvert

Noise and Disturbance

8.7.2.7 Noise and visual disturbance may be generated during site formation and construction, potentially affecting the distribution and behaviour of fauna in adjacent habitats. Disturbance sensitive species will leave the site during site formation. Due to the highly urbanised nature of the surrounding areas, limited conservation potential and disturbance tolerance of the species recorded, and the temporary nature of the impact, potential impacts to fauna from this source are ranked as minor.

8.7.2.8 The locations of the San Wai STW, Ha Tsuen Pumping Station, and the four alternative alignments of emergency bypass culvert are all more than 100 m from the ardeid roost. The roosting egrets and herons will not be affected by the construction disturbance of this project.

8.7.2.9 Noise and visual disturbance arising from all four alternative alignments of the proposed emergency bypass culvert will mainly affect urbanised areas, the ecological impacts are ranked minor. However, noise and disturbance arising from construction of the Alternative 4 alignment should be the least, as the alignment will largely follow the existing Lo Uk Tsuen Channel.

8.7.2.10 As no marine or intertidal construction works will be involved during the construction stage, there will be no impact from construction on marine ecology.

8.7.3 Summary of Construction Impacts

8.7.3.1 Potential impacts of project construction on terrestrial ecology are summarised in Table 8.16. The construction of the proposed expansion and upgrading of San Wai STW, the expansion of Ha Tsuen Pumping Station and the emergency bypass culvert will cause minor ecological impacts. The four alternative alignments of emergency bypass culvert differ little in terms of ecological impacts. However, Alternative 4 will cause the least construction disturbance as this alignment will largely follow the existing Lo Uk Tsuen Channel. No impact on marine ecology is expected during construction phase.

Table 8.16  Construction Stage Impacts

8.7.4 Operation Stage

Changes in Water Quality

8.7.4.1 Organic enrichment and nutrient status play an important role in determining patterns in bird community structure and abundance in estuarine habitats through the influence on the food base (Green et al. 1993). A reduction of anthropogenic nutrient inputs can cause increases or decline in local bird abundance and the direction of change depends on the initial nutrient status of the ecosystem. Severe inputs of organic material to eutrophicated aquatic habitats will reduce the invertebrate food base, and therefore the numbers of birds they support (Steele 1996). Increases in abundance of divers, ducks, mergansers and plovers in eutrophicated coastal habitats (e.g., estuaries) have been reported in Firth of Clyde of Scotland, Rogerstown Estuary of Ireland and Scheldt Estuary of Netherlands and Potomac Estuary of USA (Fahy et al. 1975, Furness et al. 1986, Carter et al. 1993). Declines in waterbird abundance after improvement of sewage treatment have also been reported (Steele 1996). However, these are cases in which waterbirds forage and feed at sewage outlets, or feed on invertebrates associated with sewage (e.g., Campbell 1978, Pounder 1974, 1976, Guilleman et al. 2000). This poses risks of infection of birds by diseases or parasites (Frederick and McGehee 1994).

8.7.4.2 Although a certain degree of eutrophication in Deep Bay may have increased the productivity of the ecosystem and increased benthic biomass which in turn may be partially responsible for supporting the large number of waterbirds feeding on the mudflat, it is likely that the eutrophication of Deep Bay is near the sustainable limit. Further organic enrichment will lead to a rapid decline in species and benthic biomass (Aspinwall Clouston 1997b). A dramatic drop in epifauna abundance on the inter-tidal mudflat of Mai Po was reported in summer 1996 (L. Young, pers. comm.). It has been suggested that there will be a reduction in benthic biomass if water quality in Deep Bay continues to deteriorate (Melville et al. 1997).

8.7.4.3 The E. coli level in Deep Bay increased significantly in 2000 (Environmental Protection Department. 2001). The widespread increase of E. coli in Deep Bay in the last decade resulted from an increase faecal pollution. The WQO for total inorganic nitrogen (TIN) was exceeded at all EPD's marine water sampling stations in Deep Bay as in previous years (ibid.). Values of total inorganic nitrogen showed the problem of nutrient enrichment in Deep Bay (ibid.). Deep Bay faces long-term pollution problems threatening the sensitive ecosystem in Deep Bay. HKSAR Government has noticed this situation and has formulated a "Deep Bay (Shenzhen Bay) Water Pollution Control Joint Implementation Programme" with Shenzhen Government in 2000. Under the Programme which aims at substantially reduce pollution loadings in Deep Bay, the HKSAR Government will continue to implement the relevant Sewerage Master Plans, particularly the Yuen Long/Kam Tin Sewerage Master Plan and its review. Sewage networks will be provided to unsewered villages and new developments, and sewage effluents from Yuen Long and Kam Tin will be transported out of Deep Bay to the better flushed water in Urmston Road for disposal (ibid.)

8.7.4.4 Under the present proposed project, which is a component of the Yuen Long/Kam Tin Sewerage Master Plan, the treatment level at the San Wai STW will be upgraded. One of the options is upgrading from the current preliminary treatment level to Chemically Enhanced Primary Treatment (CEPT) plus disinfection. The treatment capacity will also be expanded to serve a much larger area. Domestic sewage from a population of nearly 1,000,000 at 2016 that would otherwise mostly discharge into Deep Bay with a lower level of treatment, will be collected and treated at the San Wai STW and discharge to Urmston Road. This will greatly improve water quality in Deep Bay, which in turn will enhance species richness of benthic fauna and the food base of migratory birds.

8.7.4.5 Inter-tidal habitats in Deep Bay are important feeding habitat of many migratory birds, which are wetland dependent (Carey and Young 1999). The intertidal mudflat in Ha Pak Nai is also the nursery ground of horseshoe crabs. It is predicted the operation of the sewage treatment works will cause positive impact to the ecosystems in Inner Deep Bay.

8.7.4.6 Given the higher treatment standard in the present project (the treatment level at San Wai STW will be significantly improved from primary treatment to Chemically Enhanced Primary Treatment (CEPT) plus disinfection), the water quality in Urmston Road, which is the receiving water body of the effluent, would not be deteriorated. The sewage processed by the expanded and upgraded San Wai STW is predominantly domestic sewage. Existence of heavy metals concentrations in domestic sewage above the background level in the marine environment is not likely. The water quality modelling results showed that there would be a dramatic decrease in E.coli level (from 407 count/100ml to 23 count/100ml) at NM5, the closest EPD marine water quality monitoring station to the Marine Park. This would be a significant improvement in water quality that would be expected to result in positive effects on the health of the Chinese White Dolphin and its prey.

8.7.4.7 Changes in other water quality parameters in the Sha Chau and Lung Kwu Chau Marine Park would be generally positive, except minor increase (1%) in unionised ammonia. Unionised ammonia would increase from 0.00358 mg/l to 0.00363 mg/l, which is still well below the WQO of 0.021 mg/L. The changes would be very small. Urmston Road, however, is located at the western opening of the channel formed by the landmass of the western New Territories and Lantau Island. This channel is subject to strong tidal flushing effects four times each day. The tidal currents could effectively dilute the minor increases of unionised ammonia levels in the water body. No significant negative impacts are expected from the minimal increase of unionised ammonia levels on the Chinese White Dolphin and its prey in the vicinity of the Marine Park. Another horseshoe crab nursery ground in San Tau, will also be benefited from the positive effects of the future discharge. Furthermore, given the distance from the outfall, even the tiny increase of UIA near NM5 would not affect this area.

8.7.4.8 Given the distance from the Urmston Road outfall to Tsing Yi and Lamma Island, the dilution effect on the effluent will be more pronounced. Impacts upon soft coral, sea pens and gorgonians there from the changes in water quality would be expected to be minimal.

Emergency Discharge

8.7.4.9 Emergency plans for breakdown of the system are essential elements in all sewage treatment facilities. For sewage treatment facilities of large capacity, emergency discharge is the most feasible option to avoid uncontrolled overflow of raw or treated sewage in the catchment area. There are three future emergency discharge scenarios for the present project as summarised in the last column of Table 8.17. Other than the scenario with the break down of the NWNT tunnel or the Urmston Road outfall, i.e. scenario (ii), the other emergency discharge scenarios for the existing and the future arrangements are similar.

Table 8.17  Emergency Discharge Scenarios

8.7.4.10 With reference to the discussion in Section 1.2 of this report, under the current situation, in the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation, raw sewage will be discharged directly from the Ha Tsuen Pumping Station into the Tin Shui Wai Drainage Channel and then to Deep Bay to avoid uncontrolled overflow of raw sewage in the catchment area.

8.7.4.11 In order to reduce the chance of discharging raw sewage into Tin Shui Wai Drainage Channel and hence Deep Bay, an emergency bypass culvert, in the form of box culvert, will be constructed from San Wai STW to nearby drainage channel as part of this project. Under the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation (scenario (ii)), raw sewage from the Ha Tsuen Pumping Station will still be treated at the San Wai STW and then discharged via the proposed emergency bypass culvert to nearby drainage channel and then to Tin Shui Wai Drainage Channel and Deep Bay. With this enhancement measure, the effluent discharged to Tin Shui Wai Drainage Channel and Deep Bay under the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation will be treated effluent instead of raw sewage. The associated environmental impacts would certainly be lower when compared with the current arrangement.

8.7.4.12 In scenario (ii), the emergency discharge would be treated effluent. Given the treatment level of the effluent, the influence on Deep Bay would be limited. It is anticipated that the longest emergency repairing and maintenance works would be for the NWNT tunnel which could take up to 12 days. A worst case would therefore be taken for all emergency scenarios assuming that the emergency discharge duration would be 12 days. If CEPT plus disinfection were adopted for San Wai STW, there would be no significant deviations from the baseline water quality conditions (see Figures 5.21, 5.22, 5.31 & 5.32). This indicates that the introduction of disinfection in the treatment process would significantly minimise the water quality impacts in terms of the increase in E. coli for the emergency discharge case.

8.7.4.13 The protection of Deep Bay from raw sewage is thus significantly increased as the discharge of raw sewage into Tin Shui Wai Drainage Channel and hence Deep Bay would only occur when both the NTNW effluent tunnel/Urmston Road outfall and the San Wai STW are out of operation, or the breakdown of Ha Tsuen Pumping Station (scenario (iii)). Scenario (iii) might have temporary adverse impacts on water quality in Deep Bay. The severity of the impacts would depend upon the duration of emergency discharging, which is expected to be short and the chance of discharge is also very remote. Although a very worst-case emergency discharge duration of 12 days was assumed in the assessment for scenario (iii), the actual duration of emergency discharge under scenario (iii), if happened, is expected to be much shorter. Standby pumps and back-up power in the form of dual power supply will be installed for the expanded Ha Tsuen Pumping Station, the chance of pumping station breakdown is very remote. However, if pumping station breakdown due to power supply failure ever happened, it is expected that the power supply and hence the operation of the pumping station should be able to recover in hours as normally experienced in Hong Kong. Elevation of E. coli count, TIN and UIA levels were observed immediately after the occurrence of emergency discharge (see Figures 5.19, 5.20, 5.29 & 5.30). Tsim Bei Tsui is the nearest water quality sensitive receiver to the outlet of Tin Shui Wai Drainage Channel. The highest E. coli count, UIA and TIN would be recorded there. The high parameter levels would not be expected to have adverse impacts on the mangrove ecosystem in Tsim Bei Tsui as mangroves are well-known to be tolerant to organic pollution loading and are even used as a sewage treatment method. The influence on water quality at water quality indicator points DM1, DM2, DM3 and Pak Nai declined with increasing distance. Mai Po, which is further landward than all these indicator points, was only slightly affected by the discharges. The levels of these parameters in all indicator points, however, reduced rapidly after the termination of emergency discharge. The E. coli levels decayed rapidly and restored to the baseline conditions shortly after the termination. In another 8-10 days the TIN and UIA levels also dropped to levels approximating the baseline conditions. Given the short period of discharging and quick self-recovery of the water quality parameters, no significant influence on the Deep Bay ecosystem would be expected from this scenario.

8.7.4.14 While scenarios (i) and (ii) would not result in significant changes, in scenario (iii) horseshoe crabs in Deep Bay would be subject to a period of water quality degradation lasting up to 12 days under the assumed very worst-case emergency discharge duration for increased E. coli counts, and up to 20 days for TIN and UIA concentrations. Previous records of horseshoe crabs in Deep Bay were concentrated in Pak Nai, Nim Wan or Lung Kwu Tan, while the intertidal mudflat in Ha Pak Nai is regarded as a nursery ground (Chiu & Morton 1999). The emergency discharge point of Tin Shui Wai Drainage Channel is several km away from those locations. For another marine species of conservation concern, Chinese White Dolphin, they are commonly seen outside or near the mouth of Deep Bay. There were only occasional records of sightings within Deep Bay area. The Sha Chau Lung Kwu Chau Marine Park, which was designated for the protection of Chinese White Dolphin, is located in the North Western Water Control Zone and over 18km from the emergency discharge point of Tin Shui Wai Drainage Channel. Given this distance, much less influences will be received by this species than those on horseshoe crabs. As shown in Section 5 of this report (see Figures 5.20, 5.24 & 5.26), the E. coli, TIN and UIA levels in Pak Nai indicated that the affects of emergency discharge were not significant. No impact on horseshoe crabs or Chinese White Dolphin from the emergency discharges is expected.

8.7.4.15 Nonetheless, since the commissioning of the existing San Wai STW, the Ha Tsuen Pumping Station, and the NWNT effluent tunnel and Urmston Road outfall more than 10 years ago, it has not ever happened that the NWNT effluent tunnel or Urmston Road outfall was out of operation. The chance of both elements of the system (NWNT tunnel and San Wai STW) out of operation at the same time is even more remote. Besides routine monitoring, inspection, and maintenance to ensure satisfactory working condition of the system, the following have been and will be applied to the Ha Tsuen Pumping Station to further reduce the chance of system failure:
· Standby pumps and screens to facilitate maintenance and repair of equipment;
· Back-up power in the form of dual power supply;
· 24-hour manned pumping station; and
· Hand-cleaned bar screen at overflow bypass to prevent discharge of floating solids.

With all these measures, discharging raw sewage into the Tin Shui Wai Drainage Channel is in fact very unlikely to happen.

8.7.4.16 In scenario (i), the discharge point of raw sewage is outside Deep Bay, the entire affected water body is larger than Deep Bay. The flushing effect at Urmston Road and the dilution of the sewage in this larger water body could reduce the impacts. The TIN and UIA levels in Deep Bay for the emergency discharge case and the normal discharge case (for San Wai STW upgraded to CEPT plus disinfection) were similar without significant differences. The E. coli levels, however, were remarkably higher, ranging from 10x 103 count/100mL at water quality monitoring station NM5 to 14x103 count/100mL at Urmston Road.

8.7.4.17 Though in scenario (i) the TIN and UIA levels would be similar with those before emergency discharge, Chinese White Dolphin in Sha Chau and Lung Kwu Chau Marine Park would be subject to higher levels of E. coli count. High E. coli count indicates a higher chance of occurrence of pathogens in the water. Exposure to pathogens for a long time period might increase the chance of infection and thus affect the long-term health of dolphins. In the present case, however, given that the E. coli levels would restore to the baseline conditions shortly after the termination of discharge, the time period of high E. coli levels would be expected to be less than 12 days even under the worst case. The horseshoe crab nursery sites in Ha Pak Nai and San Tau are located over 5km and 10km respectively from the outfall location. The effects would be much lower in these two locations, and the time needed for restoring to the baseline would be shorter.

8.7.4.18 As discussed above, the frequency of occurrence of emergency discharge is very low. There have not been any emergency discharges from Ha Tsuen Pumping Station and San Wai STW since their commissioning over a decade ago. All emergency discharge scenarios would be episodic and short-term. Furthermore, the proposed project could help to reduce the pollution loadings in Deep Bay. The improvement in water quality would make Deep Bay have a higher assimilation capability for organic materials, no matter in the form of treated effluent as in scenario (ii), or raw sewage as in scenario (iii). The long-term water quality improvement in the entire activity range of the dolphins would be a more significant factor for dolphin health than the episodic accidents which would be diluted and naturally decomposed. Though water quality might decline during the emergency discharge period, based upon the low potential of the emergency discharges and the rapid restoration after the termination of discharges, the ecological impact is ranked as minor to moderate.

8.7.4.19 Other than the precaution measures listed above for Ha Tsuen Pumping Station, it is recommended that a contingency plan should be developed at the detailed design stage of this project to deal with the emergency discharges that may occur during the operational stage of the project. It is recommended to include the following items in the contingency plan:
· Locations of the sensitive receivers in the vicinity of the emergency discharges at Deep Bay and Urmston Road and the potential impacts on them;
· A list of relevant government bodies to be informed and to provide assistance in the event of emergency discharges. Information on key contact persons and telephone numbers should be included;
· Reporting procedures required in the event of emergency discharges; and
· Procedures listing the most effective means in rectifying the breakdown of San Wai STW, NWNT Tunnel or Ha Tsuen Pumping Station in order to minimise the discharge duration.

Noise and Disturbance

8.7.4.20 Machinery noise and odour of sewage from the San Wai STW and Ha Tsuen Pumping Station may cause changes in distribution pattern of some fauna (e.g., birds, dragonflies). However, the impact is minor as the remaining fauna in the Study Area is disturbance tolerant.

8.7.5 Summary of Operation Impacts

8.7.5.1 Potential ecological impacts of project operation are summarised in Table 8.18. The four alternative alignments of emergency bypass culvert differ little in terms of operation ecological impacts.

Table 8.18  Operation Stage Impacts

8.8 Mitigation Measures

8.8.1 Introduction

8.8.1.1 The EIAO-TM (Annex 16) requires that mitigation of ecological impacts be sought in the following order of priority: (1) avoid, (2) minimise, (3) compensate on-site and (4) compensate off-site. At each stage, residual impacts should be re-assessed to determine whether there is a need to proceed to the next stage of mitigation. The following measures are proposed to mitigate the impacts discussed in the preceding section.

8.8.2 Construction Stage

8.8.2.1 Site formation within the site boundary will cause the major impact during the construction phase. Direct and permanent loss of habitats including mixed woodland (0.29 ha) and their associated flora will be resulted. The overall ecological impact from the loss of habitats is considered minor due to their low to moderate ecological importance and small size in area.

8.8.2.2 Site practices for site runoff and noise control should be strictly enforced.

8.8.2.3 Site formation within the development boundary will also cause direct and permanent loss of 1.75 ha of fishponds and their associated flora. Mitigation for this loss of fishponds due to this project is not considered necessary. Nevertheless, every opportunity has been explored to provide a better implementation strategy in terms of ecology. As a result of phasing expansion of San Wai STW, a management plan for remnant fishponds left by the phase 1 expansion works for wildlife is thus recommended as an additional enhancement which is detailed in Section 8.11 below.

8.8.3 Operation Stage

8.8.3.1 The positive ecological impacts resulting from improved water quality in Deep Bay and the North Western WCZ, mainly in E. coli count, will overwhelm any potential impact, including the small increases of UIA near the outfall location, resulting from the operation of San Wai STW.
8.8.3.2 An emergency bypass culvert is proposed under this project as an enhancement measure to the existing system to reduce the chance of discharging raw sewage to Deep Bay under certain emergency situation.

8.9 Cumulative Impacts

Hung Shui Kiu New Development Area (HSKNDA)

8.9.1.1 The present proposed project is aimed at catering for the projected increase of population in NWNT and other planned developments in Yuen Long and Kam Tin areas and potential developments for Hung Shiu Kiu whereas HSKNDA is a proposed scheme. The proposed HSKNDA is planned to accommodate residential developments and ancillary G/IC facilities, commercial developments, container backup area, and other regional infrastructures. The tentative programme of HSKNDA development is to commence construction in 2004.

Waste-to-Energy Facilities (WEF)

8.9.1.2 EPD is considering a Waste-to-Energy Facility (WEF) on the existing ash lagoons to the east of the WENT Landfill. The proposed site for WEF, however, is an existing ash lagoon encircled by existing artificial seawalls. No additional reclamation would be required for the site formation of WEF. Marine transportation for that project would also utilise the existing WENT Landfill pier. Although an increase of marine traffic would result during the operation stage of WEF, the disturbance caused would be very localised and short-term. There should be no significant water quality implications in seawater caused by the proposed WEF.

Deep Bay Link and Shenzhen Western Corridor

8.9.1.3 Deep Bay Link is a land-based project. Uncontrolled release of construction site runoff into Deep Bay could cause cumulative impacts with the San Wai STW project. Construction site runoff could be effectively controlled through the implementation of suitable mitigation measures including provision of site drainage systems and sedimentation facilities, routine monitoring of the effluent discharge quality and environmental audit. Generation of wastewater and sewage, and accidental spillage of toxic substances during the construction period could also be controlled by providing chemical toilets and/or wastewater treatment facilities, off-site disposal of wastewater/sewage and establishment of a spill response plan. The potential cumulative water quality impacts due to the Deep Bay Link project are expected to be low.

8.9.1.4 Another planned project in Deep Bay is a proposed bridge across Deep Bay as part of the Shenzhen Western Corridor project. The water quality assessment results indicate that there would be limited change in water quality and hydrodynamics.

8.9.1.5 The upgrading of San Wai STW project is expected to cause positive effect on water quality in Deep Bay and also in Urmston Road in which Sha Chau and Lung Kwi Chau Marine Park is located and Chinese White Dolphin inhabits. Cumulative impacts are expected to be low from these projects.

8.10 Residual Impacts

8.10.1.1 Net loss of small areas of wasteland and urbanised areas of little ecological importance will constitute the residual impact. This is not predicted to be significant to biodiversity or habitat conservation in HKSAR. Improved sewage treatment for a larger populace will have positive effects on the Deep Bay ecosystem. The main impact of this project will be the permanent loss of small areas of terrestrial habitats and wetland habitats of limited ecological importance. The impact is considered minor.

8.10.1.2 Operation phase impacts on marine ecology are generally positive. An emergency bypass culvert is proposed under this project as an enhancement measure to the existing system to reduce the chance of discharging raw sewage to Deep Bay under certain emergency situation.

8.11 Additional Enhancement Measure

8.11.1.1 In view of the low ecological importance of the two fishponds, the fishpond loss due to the proposed expansion and upgrading of San Wai STW alone is considered minor and no mitigation is recommended under this project.
8.11.1.2 It is noted that the programme of HSKNDA development is currently subject to review and unlikely to be concurrent with the programme of this project as previously planned.

8.11.1.3 Delay of the HSKNDA development would have a knock-on effect to the full implementation of this project. About 15% of the treatment capacity of the expanded San Wai STW is catered for the strategic population growth arising from HSKNDA. Thus there is a possibility to phase part of the San Wai STW expansion to match with the future population increase. Tentatively, the programme of the works is from 2004 to 2007. The completion of phase 1 works would be 2 years after the commencement date of the works. The programme for the phase 2 works would be 3 years (at the earliest) after the commencement date of the works but subject to a future review so as to line in with the population build-up rate in the northwest New Territories. In doing so, the footprint required for the first phase of the San Wai STW expansion would be smaller and the loss of fishponds in the first phase of the expansion works would also be minimised (loss of 1 ha rather than 1.75 ha of fishpond) until the commencement of the second phase of expansion work.

8.11.1.4 Previous assessment has demonstrated that the wetland loss from the present project is tiny in area, and the habitat is low in ecological value. There would be minor impact from the habitat loss caused by site formation and no mitigation measure on the wetland loss would be required. Based upon the two-phase schedule of the project, however, an opportunity to enhance an area of wetland to promote the ecological resources in the area after the phase 1 expansion of STW is identified to achieve a more environmentally friendly implementation strategy for the whole expansion scheme.

8.11.1.5 In the first phase of the project, only 1 ha out of the 1.75 ha of the two fishponds would be reclaimed. The remnant portion of the two ponds will be retained as one pond that will be contoured to maximise the ecological value as wetland habitat during the first phase expansion of San Wai STW.

8.11.1.6 Wildlife found in areas around the San Wai STW is disturbance tolerant, and will not be much disturbed by the operation of the complete expansion, nor by the first phase expansion of San Wai STW. Ardeids were the major bird group recorded in the two ponds. The activity breeding/nesting is probably more sensitive to disturbance than feeding, yet a number of local big ardeid nesting colonies are found within or near sources of disturbance, e.g., Ho Sheung Heung egretry (in storage backyard of village houses), former Tai Po Market egretry (adjacent to Tai Po KCRC Railway Station), Mai Po Loong egretry (next to vehicle maintenance workshop) and Mai Po Village SSSI egretry (along Castle Peak Road). This showed that unless being directly disturbed by human (e.g., egg stealing), ardeids are to certain degree disturbance tolerant.

8.11.1.7 Potential disturbance from the expanded San Wai STW to wildlife in the new pond will be screened off by both screening planting and having emergent aquatic plants at the interface of the treatment plant and the new pond. Emergent vegetation will also provide foraging habitat for some waterbirds (e.g., Chinese Pond Heron, Yellow Bittern) and passerines (e.g., reed warblers, prinias, munias). In addition, emergent vegetation will provide habitat for dragonflies, butterflies and amphibians.

8.11.1.8 Previous ecological monitoring of restored fishponds showed that gravel/rock-filled pond bunds and shores supported fewer birds and species than ponds with earthen bunds and shorelines (Ecosystems Ltd. 2000). Gravel/rock-filled pond bunds probably have lower food abundance. Bunds of the new pond should be earthen. Planting of trees on the pond bund or pond area will not be necessary as this will deprive birds of feeding habitat.

8.11.1.9 Wetland dependent birds recorded in the two ponds can be classified into two groups: ardeids and kingfishers. Posts will be installed on the pond shore to provide foraging perches for kingfishers.

8.11.1.10 Pond slope is an important factor affecting the use of pond bunds as foraging and roosting habitats by waterbirds (e.g., Street 1989, Colwell and Taft 2000). Slopes of 1:4 to 1:6 are recommended (Street 1989). This will require re-contouring of the existing pond bunds.

8.11.1.11 Water level is considered to be an important factor affecting the uses of wetlands by waterbirds (e.g., Velasquez 1992, Kazantidis and Goutner 1996, Dimalexis and Pyrovetsi 1997, Colwell and Taft 2000, Bancroft et al. 2002). Foraging water depth of waterbird species is correlated to their tarsus lengths (Ntiamoa-Baidu et al. 1998). The new pond will include a range of water depth to provide the diverse microhabitats for waterbirds.

8.11.1.12 Currently there is a stream feeding the two fishponds at the Northeast corner. This stream will provide water source for the enhancement pond before the commencement of the proposed HSKNDA.

8.11.1.13 Re-contour of the remnant portion of the two ponds will precede the filling of fishponds for first phase expansion of San Wai STW. The role of this enhancement pond would remain until the time of the phase 2 expansion of San Wai STW to match with the future population increase.

8.12 Conclusion

8.12.1.1 Deep Bay is facing long-term pollution problems which threaten the sensitive ecosystem in Deep Bay. HKSAR Government is planning to substantially reduce pollution loadings in Deep Bay. Under the Yuen Long/Kam Tin Sewerage Master Plan, sewage networks will be provided to unsewered villages and new developments, and sewage effluents from Yuen Long and Kam Tin will be transported out of Deep Bay to the better flushed water in Urmston Road for disposal (EPD 2001). The proposed project is an important component of the Plan.

8.12.1.2 Flora and fauna recorded in the Study Area during field surveys covering wet and dry seasons are generally of low conservation importance and disturbance tolerant. Habitats within the Study Area are mostly man-made, highly fragmented and disturbed. The project will mainly cause permanent loss of habitats of low ecological importance, hence ecological impact is considered minor. The project will greatly improve water quality in Deep Bay, a site of recognised international importance. Tiny increases of UIA (1%) would be expected near the outfall location and in the Sha Chau and Lung Kwu Chau Marine Park. The changes, however, would be very small and would be outweighed by the significant drop of E. coli count there. Therefore, the overall impact of the project will be positive.

8.12.1.3 An emergency bypass culvert, in the form of box culvert, will be constructed from San Wai STW to nearby drainage channel as part of this project. This culvert will largely reduce the chance of discharging raw sewage into Deep Bay. Under the current emergency situation, raw sewage will be discharged directly from the Ha Tsuen Pumping Station into the Tin Shui Wai Drainage Channel and then to Deep Bay when the NWNT effluent tunnel or the Urmston Road outfall is out of operation. The proposed project will provide an alternative pathway for San Wai STW to dispose treated effluent. With this enhancement measure, the effluent discharged to Tin Shui Wai Drainage Channel and Deep Bay under the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation will be treated effluent instead of raw sewage. The associated environmental impacts would certainly be lower when compared with the current arrangement.

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