4                    ECOLOGY

 

Introduction

 

4.1              This Section of the report presents the results of the assessment of potential impacts from the construction and operation of the jetty on terrestrial and marine ecological resources in the Assessment Area. A review of existing information has been undertaken to identify ecological sensitive areas and field surveys covering both the wet and dry seasons were undertaken to establish the baseline ecological conditions of the Assessment Area. Measures required to mitigate identified impacts are recommended, as appropriate.

 

4.2              The objectives of the ecological assessment are as follows:

 

·                    to establish the ecological importance of habitats affected by the works associated with the construction and operation of the jetty;

 

·                    to identify ecological sensitive receivers;

 

·                    to assess the scale of possible ecological impacts from the proposed Project;

 

·                    to identify any necessary mitigation measures and evaluate residual impacts; and

 

·                    to assess the need for an ecological monitoring and audit programme.

 

Environmental Legislation, Standards and Guidelines

 

4.3              This section makes reference to the following guidelines, standards, documents and HKSAR Government ordinances and regulations when identifying habitats and species of ecological importance, and assessing potential impacts of the proposed project on the ecological resources in the assessment area:

 

·        Marine Parks Ordinance (Cap 476) and associated Subsidiary Legislation;

·        Sites of Special Scientific Interest Register;

·        Forests and Countryside Ordinance (Cap 96) and its subsidiary legislation, Forestry Regulations;

·        Wild Animals Protection Ordinance (Cap 170);

·        Town Planning Ordinance (Cap 131);

·        Hong Kong Planning Standards and Guidelines Chapter 10 (HKPSG);

·        Environmental Impact Assessment Ordinance (Cap. 499) and the associated Technical Memorandum on Environmental Impact Assessment Process (EIAO TM) Annex 8 and Annex 16.

 

4.4              The Forests and Countryside Ordinance prohibits felling, cutting, burning or destroying of trees and growing plants in forests and plantations on Government land.  Related subsidiary Regulations prohibit the selling or possession of listed rare and protected plant species.  The list of protected species in Hong Kong which comes under the Forestry Regulations was last amended on 11 June 1993 under the Forestry (Amendment) Regulation 1993 made under Section 3 of the Forests and Countryside Ordinance.

 

4.5              Under the Wild Animals Protection Ordinance, designated wild animals are protected from being hunted, whilst their nests and eggs are protected from injury, destruction and removal.  All birds and most mammals are protected under this Ordinance.  The Second Schedule of the Ordinance which lists all the animals protected was last revised in June 1992.

 

4.6              The amended Town Planning Ordinance provides for the designation of coastal protection areas, Sites of Special Scientific Interest (SSSIs), Conservation Area, Country Park, Green Belt or other specified uses that promote conservation or protection of the environment.  The authority responsible for administering the Town Planning Ordinance is the Town Planning Board.

 

4.7              Chapter 10 of the HKPSG covers planning considerations relevant to conservation.  This chapter details the principles of conservation, the conservation of natural landscape and habitats, historic buildings, archaeological sites and other antiquities.  It also addresses the issue of enforcement.  The appendices list the legislation and administrative controls for conservation, other conservation related measures in Hong Kong and government departments involved in conservation.

 

4.8              Annex 16 of the EIAO TM sets out the general approach and methodology for assessment of ecological impacts arising from a project or proposal, to allow a complete and objective identification, prediction and evaluation of the potential ecological impacts.  Annex 8 recommends the criteria that can be used for evaluating habitat and ecological impact.

 

4.9              The report also makes reference to the following international conventions where appropriate:

 

·        Convention on the Conservation of Migratory Species of Wild Animals (the “Bonn Convention”)

·        United Nations Conventions on Biodiversity (1992);

·        The PRC National Protection List of Important Wild Animals;

·        Agreement between the Government of Australia and the Government of PRC for the Protection of Migratory Birds and their Environment;

·        Agreement on the protection of Migratory Birds and Their Habitats by the Governments of Japan and the PRC; and

·        IUCN Red Data Books

·        Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES)

 

4.10          Convention on the Conservation of Migratory Species of Wild Animals (the “Bonn Convention”) has two main objectives:

 

·        To provide strict protection for species listed in Appendix I of the Convention (migratory species in danger of extinction throughout all or a significant portion of their range); and

 

·        To encourage Range States for such species to conclude agreements for the conservation and management of Appendix II species (migratory species which have an unfavourable conservation status and require international agreements for their conservation, or which have a conservation status which would significantly benefit from international co-operation).

 

4.11          Hong Kong was originally a Party to the Convention through the United Kingdom. The convention continues to apply to Hong Kong after1st July 1997 by agreement of the Sino-British Joint Liaison Group, though the PRC is not a party thereto

 

4.12          The Peoples' Republic of China (PRC) are one of the Contracting Parties to the United Nations Convention on Biological Diversity of 1992.  The Convention requires signatories to make active efforts to protect and manage their biodiversity resources.  Hong Kong Government has stated that it will be 'committed to meeting the environmental objectives' of the Convention (PELB 1996).

 

4.13          The IUCN Red List is the world’s most comprehensive inventory of the global conservation status of plants and animals. It uses a set of criteria to evaluate the extinction risk of thousands of species and subspecies. These criteria are relevant to all species and all regions of the world. There are seven Categories of Threat in the IUCN Red List system: Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, and Least Concern. A species is listed as threatened if it falls in the Critically Endangered, Endangered or Vulnerable categories.

 

Assessment Methodology

 

Baseline Information

 

4.14          Baseline information was collated via a review of previous surveys of the Assessment Area (Figure 1.1).  The review included:

 

·        A literature review of the ecological conditions within the Assessment Area, including Proposed Aviation Fuel Receiving Facility at Sha Chau: EIA (ERM 1994); Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme: Final Report May 2000 (HKIEd 2000), First Quarterly Report September 2001 (HKIEd 2001), Second Quarterly Report January 2002 (HKIEd 2002);  and Population Biology of the Indo-Pacific Hump-backed Dolphin (Sousa chinensis Osbeck, 1776) in Hong Kong Waters: Final Report (Jefferson 1998); Population Biology of the Indo-Pacific Hump-backed Dolphin in Hong Kong Waters (Jefferson 2000) and unpublished data from on-going North Lantau dolphin monitoring programme (with AFCD permission).

 

·        Habitat and ecological communities mapped with reference to the Vegetation Map prepared by World Wide Fund for Nature Hong Kong (1994).

 

4.15          Field surveys were undertaken to supplement and check the data collected through the baseline/literature review process.  The ecological surveys covered the period between February 2001 and February 2002, during which habitat/vegetation, avifauna, terrestrial mammals and herpetofauna surveys were undertaken. Intertidal, and subtidal fauna were also surveyed (the latter by underwater dive survey).  Ecological field data were collected in both the dry and wet seasons.  The methodologies used, along with details of the results, are given in Appendix 4.1.

 

4.16          Potential ecological impacts arising from the development of the Assessment Area were assessed following EIAO TM Annex 16 guidelines and the impacts evaluated based on the criteria in EIAO TM Annex 8.

 

TERRESTRIAL ECOLOGY

 

Description of Existing Ecological Baseline Conditions

 

4.17          Two main habitat types dominated the terrestrial habitats of the Assessment Area: backshore vegetation and grassland/shrubland mosaic (Figure 4.3)

 

Backshore Vegetation

 

4.18          The terrestrial flora inside the Assessment Area have previously been surveyed by Chan & Kwok (1988). These researchers described the shore vegetation of nearby Sha Chau. Over 35 plant species were observed, predominantly on the high sandy shore. In the exposed lower shore areas species showing adaptation to exposure and salt tolerance were found such as the Sea Lettuce (Scaevola sericea). Other plant species found were common and typical of HK backshore. These included Pandanus tectorius (Scew Pine), Ipomea brasiliensis (Beach Morning Glory), Ipomea hederacea, Wedelia prostrata and Clerodendrum inerme (sea-shore glorybower).

 

4.19          A similar community was found in the Assessment Area according to field survey results. Open areas close to the shore were dominated by Ipomea sp. and Clerodendrum inerme. Areas of dense shrub were dominated by Hibiscus tiliaceus, along with smaller stands of Pandanus tectorius.   This vegetation is separated from the boulder shore by a strip of disturbed ground.  This ground is covered in a deteriorating concrete/gravel mix layer, presumably used as a path during the construction of the DVOR/DME Station on the island.  This concrete has hindered the establishment of vegetation between the path to the existing jetty and the bulkhead. The backshore vegetation along this strip of concrete mix comprises patches of low grasses, exotic weed species and bare ground.

 

 

Grass/Shrub Mosaic

 

4.20          Lung Kwu Chau was previously characterised as mainly comprising grassland with scrub (WWF 1994).  During field surveys it was also observed that the hillsides in the Assessment Area were covered in typical Hong Kong hillside vegetation comprising mainly grass and bush (Figure 4.3). Adjacent to the footpath leading to the DVOR/DME Station, there are stands of the exotic trees, Acacia confusa, Casuarina equisetifolia and Leucaena leucocephala. The lack of developed old forest growth on Lung Kwu Chau is probably related to the poor soil type and possible history of hill fires.

 

Wildlife

 

4.21          There has been no published research work on mammal, herpetofauna or insect populations in the Assessment Area.  During field surveys on the island, no evidence of terrestrial mammals (such as burrows or scats), amphibians and reptiles, or dragonflies and butterflies was observed.

 

4.22          The Island group of which Lung Kwu Chau is a part was initially assigned SSSI status in recognition of its interesting avifauna, and the importance of Tree Island as a night-time roost for wintering Cormorants (Phalacrocorax carbo). During field visits made for the Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme, a variety of avifauna have been sighted feeding or roosting in the Assessment Area.  These include Egretta sacra, Egretta garzetta, Phalacrocorax carbo, Tringa glareola, Haliaeetus leucogaster, Milvus migrans, Motacilla alba, Pycnonotus jocosus, Pycnonotus sinensis, Halcyon smyrensis and Acridotheres cristatellus (HKIEd 2002).

 

4.23          Cormorants were identified among the 19 species found during the field survey in 2001. Winter visitors and common residents made up the majority of the avifauna.  The species observed were: P. carbo, Egretta garzetta, Egretta sacra, Larus vegae, Milvus migrans, Actitis hypoleucos, Halcyon smyrnensis, Alcedo atthis, Apus nipalensis, Hirundo rustica, Pycnonotus jocosus, Pycnonotus sinensis, Monticola solitarius, Phylloscopus proregulus, Orthotomus sutorius, Phylloscopus proregulus, Zosterops japonicus, Corvus macrorhynchos, Zosterops japonicus and Acridotheres cristatellus.  All these are common and widespread species.  Also observed was an individual Haliaeetus leucogaster. It was observed soaring over the southwest of the island (located approximately 800m from the proposed jetty location). According to HKIEd (2002), this area is where this eagle has its roost. From the field surveys, no breeding activity for H. leucogaster has been observed in the Assessment Area.

 

Ecological Value

 

4.24          In accordance with the EIAO TM Annex 8 criteria, the ecological importance of the recorded habitats are evaluated in the Table 4.1  below.

 

Table 4.1            Ecological Value of Terrestrial Habitat types in the Assessment Area

Criteria

Backshore Vegetation

Grass/shrub mosaic

Naturalness

Natural habitat with some human disturbance.

Natural habitat but subject to hill-fire.

Size

Small in size

Moderate in size

Diversity

The species diversity is low.

The species diversity is low.

Rarity

No rare species were recorded in the habitat

No rare species were recorded in the habitat

Re-creatability

It has a moderate re-creatability.

The vegetation type is secondary and readily re-created naturally or artificially and would recover easily from disturbance.

Fragmentation

The habitats are not fragmented but always have a linear shape forming band along the coastline.

The grassland/shrubland mosaic is not fragmented.

Ecological linkage

The present habitats are not functionally linked to any highly valued habitat in close proximity in a significant way.

The present habitats are not functionally linked to any highly valued habitat in close proximity in a significant way.

Potential value

The potential value is low.

The potential value is low.

Nursery ground

No record of significant nursery or breeding ground was found in the survey.

No record of significant nursery or breeding ground was found in the survey.

Age

Relatively mature and stable.

The habitats are secondary in nature.

Abundance/Richness of Wildlife

Low

Low

Ecological value

Low

Low

 

 

4.25          Based on the ecological conditions presented in the above sections, it is considered that the backshore vegetation and grassland/shrubland habitats within the Assessment Area have generally low value because of their poor diversity, exposure and relative isolation of the island and also because the species identified are common, widespread and typical to such habitats in Hong Kong.

 

Identification of Environmental Impacts

 

4.26          The potential terrestrial ecological impacts arising from the proposed development have been identified.  Potential impacts associated with the construction and operation phases of the project are set out below:

 

Construction Phase

 

4.27          The potential terrestrial ecological impacts arising from the construction activities may include:

 

·        Direct impacts due to habitat loss (i.e. loss of backshore vegetation),

 

·        Indirect impacts due to construction activities such as increased human activities/disturbance, uncontrolled storage or dumping of construction material, and hill fires.

 

Operation Phase

 

4.28          Indirect impact to the surrounding habitats and associated wildlife because of increased human activities/disturbance associated with the operation of the proposed jetty or increased ease of illegal access to the island.

 

 

Impact Evaluation

 

4.29          Potential impacts on terrestrial ecology evaluated according to Table 1 of Annex 8 of the EIAO TM are given in Table 4.2 and Table 4.3.

 

Table 4.2            Overall Impact Evaluation of Backshore Vegetation

Evaluation Criteria

Discussion

Habitat quality

The habitat quality of backshore vegetation is low comprising patches of low grasses, exotic weed species and bare ground and having been subject to previous disturbance.

Species

There may be potential direct or indirect impact to the wildlife inhabiting the areas, although no species of high conservation value would be affected. 

Size/Abundance

Approximately 0.008 ha (i.e. 52m x 1.6m) of habitat would be lost

Duration

The duration of impact will persist during construction and operation phases.

Reversibility

The impact of direct loss of backshore vegetation is irreversible.

Magnitude

The scale of habitat loss is small in the context of the surrounding similar habitats. The footpath can also be aligned along the strip of previously disturbed ground.

Overall impact conclusion

Low

 

 

Table 4.3 Overall Impact Evaluation of Grassland/Shrubland Mosaic and Other habitats

Evaluation Criteria

Discussion

Habitat quality

The habitat quality of grassland/shrubland mosaic is low. 

Species

There will be no potential direct impact to the wildlife inhabiting the areas, although indirect impacts may occur 

Size/Abundance

Grassland/shrubland cover approximately 90% of Lung Kwu Chau

Duration

The duration of impact will persist during construction and operation phase.

Reversibility

The impact of direct loss of grassland/shrubland mosaic is irreversible.

Magnitude

The scale of habitat loss is small in the context of the surrounding similar habitats.

Overall impact conclusion

Low

 

4.30          Overall, the potential ecological impact to terrestrial habitats is expected to be very low because most of the habitats impacted are generally of low ecological importance. The area directly affected (i.e. backshore vegetation) is very small and has already been subject to disturbance and modification in the past during construction of the DVOR/DME Station.

 

 

Mitigation of Adverse Environmental Impacts

 

4.31          The above assessment indicates that during construction, the direct loss of terrestrial habitats to the development is unavoidable but environmentally acceptable. Mitigation measures are therefore focussed on avoiding and minimising impacts on habitats in the Assessment Area which will remain intact after the Project is completed. Suggested mitigation measures are outlined below:

  

·        Reinstate temporary work sites/disturbed areas immediately after completion of the construction.

 

·        Check the work site boundaries regularly to ensure they are not exceeded and that no damage occurs to surrounding natural habitats.

 

·        Prohibit and prevent open fires within the work site boundary during construction and provide temporary fire fighting equipment in the work areas.

 

Residual Environmental Impacts

 

4.32          With the implementation of the mitigation measures recommended above, there will be residual terrestrial ecological impacts associated with the proposed project: the loss of a small area of backshore vegetation and grass/shrubland due to the construction of the catwalk and footpath is an inevitable consequence of the project. However, the impact is considered acceptable given the small area and low ecological value of the habitat to be lost.

 

Ecological Monitoring and Audit (EM&A) Requirement

 

4.33          The implementation of the recommended mitigation measures in Section 4.31 should be monitored and audited during detailed design and construction stage.

 

Conclusions

 

4.34          Based on the assessment, a very low impact on terrestrial ecological resources is anticipated. Good construction practices are recommended to minimise or avoid disturbance to surrounding habitats.

 

 

MARINE ECOLOGY

 

Description of existing ecological baseline conditions

 

4.35          Three habitat types were identified in the Assessment Area: inter-tidal habitats, sub-tidal habitats, and marine mammal habitats (Figure 4.3).

 

Intertidal habitats

 

4.36          The intertidal ecological habitats in the assessment area are comprised of a mixture of natural rocky shore and sandy shore (HKIEd 2002). 

 

Rocky Shores

4.37          Rocky shore flora and fauna have been extensively investigated at 3 locations in the Assessment area in both the wet and dry season as part of the Shau Chau and Lung Kwu Chau Marine Park Monitoring Programme (HKIEd 2000, 2001,2002). Monitoring sites include a location north of the bay on the eastern side of Lung Kwu Chau where jetty construction is proposed. The other sites are on the west side of Lung Kwu Chau and the southeast side of Sha Chau (Figure 4.5). Results from this monitoring programme indicate rocky shore fauna at the Marine Park, comprise  a variety of marine snails (Nodolittorina spp., Littoraria spp., Mododonta labio [=M. australis], Nerita spp., Thais clavigera, Planaxis sulcata), limpets (Patelloida pygmaea, Siphonaria atra), barnacles (Tetraclita squamosa, Capitellum mitella [=Pollicepes mitella], Chthamalus malayensis), bivalves (Saccostrea cucullata, Barbatia virescens, Septifer bilocularis, Perna viridis), sea anemones (Haliplanella luciae, Anthopleura pacifica ), sea slaters (Ligia exotica), slugs (Onchidium sp.) and shore crabs.  Similarly, the rocky shore flora have been found to consist macroalgae (Hildenbrandtia spp. Enteromorpha sp., Gelidium amansii, Ulva spp., brown turf, green turf), cyanobacteria (Kyrtuthrix maculans, Verrucaria sp., grey cyanobacteria), algal films/slimes and lichens (Caloplaca sp.). Seasonal succession patterns in the Marine Park are dominated by the decline of macroalgae in summer which is typical across Hong Kong (Morton & Morton 1983). The surveys have also found that the vertical zonation patterns in organism’s distribution are typical. For instance, the Littorinids and Nodolittorinids dominate the high shore and may occur in high abundance (up to 375 per m2) (HKIEd 2001).  The rocky shore biota of the Marine Park comprise species common to other rocky shores in Hong Kong with the most similar assemblages of rocky shore biota found in Deep Water Bay and along the open coastline at Tai Lam Chung near Castle Peak. (Morton & Morton 1983). Rocky shores are the most widespread intertidal habitats in Hong Kong comprising as much as 80% of its coastline.

 

4.38          Findings of surveys conducted for the Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme were similar to results from field survey work (see Figure 4.4 for location). Observations in the field indicated that the assemblages were a mix of sheltered and more exposed rocky shore assemblages typical of the moderately exposed conditions. Littorinids were observed to be most common higher up in the littoral zone, as were sea slaters (Ligia exotica). Patches of Kyrturthrix cyanobacteria were also present on the high shore.  Lower down the seashore were observed the snails Monodonta spp. and Nerita spp.. Also found on the mid shore was the crustose algae Hildenbrantia and the limpet Tetriclita squamosa which was attached to the exposed rocky surfaces, while the stalked barnacle (Capitellum mitella) was confined to the sheltered crevices.  On the lower shore several Saccostrea cucullata were observed. During site visits in late winter, macroalgae, primarily Enteromorpha and Ulva as well as Sargassum were observed to attain high coverage on the mid to low shore.   Species identified during the field survey are common and widespread on the Hong Kong rockyshores (Morton & Morton 1983).There is a functional linkage between the rocky shore and ecosystem in the Marine Park as whole, although it is known that intertidal organisms are not directly predated upon by dolphins. For instance, energy captured by primary producers (e.g. macroalgae) and contained in larvae which are released into the plankton, is transferred into the area’s marine food web.   

 

Sandy Shores

 

4.39          Several surveys of the sandy shore habitat inside the Assessment Area have previously been undertaken with results available in the Proposed Aviation Fuel Receiving Facility at Sha Chau: EIA (ERM 1994) and Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme reports (HKIEd 2000).  The consensus is that the sandy shores in the Marine Park are a poor habitat. Sandy shore macrofauna were only encountered at Sha Chau with their abundance and diversity being low (ERM 1994). At Sha Chau, only 5 species were recorded: gastropods (Nerita albicila, Nassarius sp.), bivalves (Tapes philippinarium), annelids (Nephtys sp.), and sipunculids (Phascolosoma scolops). Out of 24 individuals found (from 16 quadrat samples), 15 were Nerita albicilla. In addition,  most sand samples (54%) were devoid of macrofauna (ERM 1994). Similarly, no sandy shore macrofauna were encountered during surveys by HKIEd which were conducted on the eastern side of the sandbar at Lung Kwu Chau and at 2 locations on the western side of Sha Chau (Figure 4.5). The relative absence of macrofauna from the Assessment Area’s sand shores was attributed to the coarse grain size of the sand, which leads to rapid desiccation of the shore and hence intolerable conditions for sandy shore infauna.  

 

4.40          These findings were confirmed during field surveys (see Figure 4.4 for location). No macro-invertebrates (>500 mm in diameter) were recorded during the field survey.  It was considered that the absence of macro-invertebrate infauna was due to course sand grain size limiting interstitial water retention leading to desiccation.  Nevertheless, a close visual inspection of the sandy shore revealed a small number of burrow openings next to which was observed one large ghost grab (Ocepode certophthalmus), however broadly speaking it can be concluded that the sandy shore is largely devoid of macroscopic life.  Another notable feature of the sandy shore in the bay on Lung Kwu Chau was the large accumulation along the strandline of rubbish and flotsam washed ashore from the sea.

 

Sub-tidal habitats (Infauna and Corals)

 

4.41          According to the survey from the Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme, grab samples along two line transects were carried out at the Artificial Reef site, west of Sha Chau, prior to reef deployment (Figure 4.1). Results showed that 90% of the samples were composed of three dominant groups: polychaetes (present in 53% of grab samples), gastropods (28%) and bivalves (9%) with the remainder (10%) consisting nematodes, shrimps, crabs, ophiuroids and hemichordates. 

 

4.42          In order to investigate the benthic communities, 3 representative grab samples of the bottom mud were obtained from the bay in November 2001 during a field visit to the island (Figure 4.4). These comprised dark olive green homogenous viscous silty mud and were thoroughly sifted through in a sorting tray.  No macroscopic benthic organisms were encountered. It was also noted that that there were darker/black wisps in the sediment that were interpreted as being indicative of low oxygen conditions deeper in the mud.  However no odour was detected.  Fine grained silty mud is a common habitat in Hong Kong covering approximately two thirds of its seabed area. It is also worth noting that sediment grab samples taken closer to the shore during a later sediment quality investigation (February 2002) also comprised silty mud but also contained rubbish (plastic bags) and plant debris (twigs).  The plant debris was assumed to have been washed into the bay off the neighbouring hillside.

 

4.43          Despite grab survey not encountering benthic macro-invertebrate infauna, it can be assumed that given the similarity of the substrates and proximity of the two sites, that the benthic communities supported by the assessment area and the area surveyed west of Sha Chau are similar in terms of their structure and function.

 

4.44          Owing to their reduced salinity and high turbidity, western Hong Kong waters close to the Pearl River are a marginal area for coral growth with only a restricted number of coral species able to tolerate these conditions. As part of the EIA for the Proposed Aviation Fuel Receiving Facility at Sha Chau, both dive and trawl surveys were previously undertaken in the Assessment Area (Figure 4.6). These found scattered stone corals (Faviidae), gorgonians and seapens around Sha Chau. Seapens and gorgonians were most abundant between the islands. Seapens were identified as Pteroides esperi, P. sparmanni, Sclerobelemnon burgeri, Virgularia gustaviana. Corals (Families: Gorgonacea and Faviidae) were not identified to a higher taxonomic resolution.   For the Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme, no dive surveys have been conducted.   

 

4.45          Dive surveys in the bay (Figure 4.4) revealed that there were no corals on the soft seabed in the bay.  The reason for this was that the substrate in the subtidal areas comprised silty mud unsuitable for coral growth.  Besides, during the dive surveys it was noted that the waters in the bay are highly turbid making the area especially unsuitable for hermatypic corals.  The salinity of marine waters at Lung Kwu Chau is also heavily influenced by discharge from the Pearl River, which is one more reason why hermatypic stony corals were not observed.  Nevertheless, numerous common blue coloured gorgonian short seawhip soft coral (Euphexaura sp.), was discovered growing attached to the shipwreck structure past the north of the bay (Figure 4.1). Also attached to the shipwreck were 2 colonies of the ahermatypic coral Tubastrea sp.  These were both dead. The same blue coloured Euphexaura sp. gorgonians were also observed growing on rusting steel bars in the southern section of the bay of the existing jetty.  These colonies were small and numbered only 6 in total. No scleractinian corals were encountered within the bay. These results of the dive surveys conducted in the bay area were similar of previous surveys of neighbouring areas inside the Assessment Area.

 

Marine Mammal Habitats

 

4.46          The Chinese White Dolphin (Sousa chinensis) (also known as the Indo-Pacific Humpback Dolphin) has been extensively recorded in the eastern waters of the Pearl River Estuary with its population estimated at over 1000 individuals (Jefferson 1998, 2000).  It’s range in these waters extends to all Hong Kong western waters but it is most frequently sighted in the areas north and west of Lantau Island up to Deep Bay (Jefferson 1998, 2000). The area north of Lantau Island is considered the most important habitat for this species in Hong Kong. In Hong Kong, S. chinensis is afforded protection by the Wild Animals Protection Ordinance and the Animals and Plants (Protection of Endangered Species) Ordinance. The species is also CITES Appendix 1 listed and is catalogued in the IUCN Red Data Book. As a conservation measure the waters around Sha Chau and Lung Kwu Chau were designated a Marine Park in 1996. Dolphins are commonly sighted in these waters which are recognised as important dolphin feeding grounds (Parsons et al., 1996, Jefferson 1998, HKIEd 2000). Chinese White Dolphins typically feed in shallow coastal areas up to 10 m deep (Jefferson, 1998).

 

4.47          The most detailed knowledge of the local Chinese White Dolphin population’s distribution and abundance has been acquired through sightings data collected during line transect surveys by the Ocean Park Conservation Foundation (OPCF) from late 1995 to late 1998 and since that time by AFCD.  These vessel surveys indicate that, while dolphins occur throughout nearly the entire North Lantau area, they are most common in the western waters north of the new airport at Chek Lap Kok (Jefferson 1998, 2000, AFCD unpublished data). At any one time, there are estimated to be between 88 and 145 dolphins present within Hong Kong's waters, depending on season (Jefferson 2000). Dolphins are present in Hong Kong waters in their greatest numbers in summer, and lowest numbers in spring (Jefferson 2000). The proportion of the local population that occurs in North Lantau waters as opposed to other areas of Hong Kong waters varies from 72% in spring to 92% in the winter months when the abundance of dolphins occurring in Hong Kong waters is at its lowest.  According to the latest monitoring data, the peak abundance of dolphins in the North Lantau area during summer is estimated at 91 individuals (AFCD unpublished data). Although there are seasonal fluctuations in the number of dolphins present, nevertheless the region around Lung Kwu Chau appears to be a very high-density area throughout the entire year.

 

4.48          The importance of the Sha Chau and Lung Kwu Chau Marine Park waters to individual dolphins has also illustrated, based on the results of a study of ranging patterns using photoidentification data (Hung 2000; Hung and Jefferson in press).  Of the 28 individual dolphins analyzed, 22 (78.9%) used the area around Lung Kwu Chau as a prominent part of their home range. One female dolphin (catalog number NL11) used the area around Lung Kwu Chau, almost exclusively, during the period of time that it was pregnant and nursing a small calf (Hung 2000). Taken together, these findings clearly demonstrate the importance of this area to these animals.

 

4.49          Figure 4.2 illustrates the location of dolphin sighting in different ‘seasons’ over a six year period (1995-2001) in the vicinity of the Assessment Area incorporating the most recent unpublished sighting data from the AFCD monitoring programme.

 

4.50          Dolphin’s utlisation of the waters surrounding Lung Kwu Chau has also been demonstrated by monthly survey observations between December 1998 and November 2001 for the on-going Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme (HKIEd 2000, 2001, 2002).  Dolphin sighting rates exceed 80% and compared to observations around Sha Chau, the average number of dolphins seen from Lung Kwu Chau was considerably greater. In particular, the waters east of Lung Kwu Chau appear to be important habitat because this area was where dolphin sightings are most frequently recorded. However, in this area to the east of Lung Kwu Chau, fewer dolphins were sighted close to shore and instead the majority of dolphins (68%) were sighted outside the Marine Park boundary (HKIEd 2000). This pattern of higher dolphin activity east of Lung Kwu Chau was previously reported by Jefferson (1996). Parsons (1996) speculated that warm water discharge from Castle Peak Power Station may be a factor contributing to their preferred presence in this area.

 

4.51          Owing to their common occurrence in the Lung Kwu Chau waters, the protected Chinese White Dolphin (S. chinensis) is therefore a key marine sensitive receiver.

 

Chinese King Crabs

 

4.52          Chinese King Crabs (also called Horseshoe crabs) in Hong Kong are predominently represented by the species Tachypleus tridentatus and Carcinoscorpius rotundicauda. These species mostly occur in the western waters and have been recorded from 12 beach sites along the Deep Bay and northeast Lantau coasts as well as islands in North Lantau waters  (Chui & Morton 1999).  Tap Shek Kok and Lung Kwu Sheung Tan are the two known breeding sites of the Chinese King Crab, Tachypleus tridentatus.  Although the Chinese King Crab is not protected in Hong Kong under any statutory Ordinance, this species is of great zoological interest since it is a surviving member of Xiphosura and occurs in relatively few locations in the world. Its numbers in Hong Kong are known to be in decline (Chui & Morton 1999). According to local fishermen and marine biologists, the occurrence of Chinese King Crabs in Hong Kong coastal waters is seasonal; the species spawns in February/March and is abundant in April and May.  Since Lung Kwu Chau is near to Lung Kwu Sheung Tan and Tap Shek Kok, the Chinese King Crab may also be found in the Assessment Area. Two landings of Carcinoscorpius rotundicauda were reported in the Lung Kwu Chau and Sha Chau area in 1996, however, trawl surveys carried out for the EIA Study for the AFRF at Sha Chau reported no record.  The Chinese King Crab and their eggs were not found in the field surveys conducted at Lung Kwu Chau under this Project.

 

Ecological Value

 

4.53          In accordance with the EIAO TM Annex 8 criteria, the ecological importance of the recorded habitats are evaluated in the Tables 4.4 and 4.5  below.

 

Table 4.4            Ecological Value of Intertidal and Subtidal Benthic Habitats

Criteria

Intertidal Habitats

Sub-tidal benthic habitats

Naturalness

Natural habitat with limited human disturbance (flotsam and litter, pollution)

Natural habitat with limited human disturbance (pollution/ dumping, litter).

Size

Small in size

Large in size

Diversity

The species diversity is low.

The species diversity is low.

Rarity

No rare species found in the habitat

No rare species found in the habitat

Re-creatability

The habitat cannot be recreated on site but the jetty armour rock and blockwork will be available for colonisation by intertidal organisms

The habitat cannot be recreated on site.

Fragmentation

The habitats are not fragmented

The sub-tidal habitats are not fragmented.

Ecological linkage

The present habitats are functionally linked to the Marine Park ecosystem as a whole providing a limited source of primary production for transfer to higher trophic levels in the food web.

The present habitats are not functionally linked to any highly valued habitat in close proximity in a significant way.

Potential value

The potential value is low.

The potential value is low.

Nursery ground

No record of significant nursery or breeding ground was found in the survey.

No record of significant nursery or breeding ground was found in the survey.

Age

n/a

n/a

Abundance/Richness of Wildlife

Low

The diversity of the benthic infauna in the region is typical of similar habitats throughout Hong Kong.  Seapens and Gorgonians are widespread in similar habitats across Hong Kong.

Ecological value

Low

Low

 

 

Table 4.5            Ecological Value of Marine Mammal Habitat

Criteria

Marine Mammal Habitats

Naturalness

Disturbed to some extent by pollution. Protected from over-fishing/disruptive maritime traffic by marine conservation park status

Size

The area of the Marine Park affected by the project is relatively small.

Diversity

Habitat does not support a diverse community

Rarity

Important habitat for the rare and protected marine mammal: S.chinensis

Re-creatability

A small area of habitat will be lost permanently to the jetty.

Fragmentation

The habitat is not fragmented

Ecological linkage

Marine mammal habitats extend in all directions around the coastal waters of Lung Kwu Chau

Potential value

High because of recent assigning of Marine Park status, and the establishment of artificial reefs within the Marine Park

Nursery ground

Possible breeding ground of S. chinensis

Age

n/a

Abundance/Richness of Wildlife

Habitat supports high densities of S. chinensis throughout the year

Ecological value

Habitat of high value to S. chinensis

 

4.54          Based on the ecological conditions presented in the above sections, it is considered that the inter-tidal and sub-tidal habitats within the Assessment Area have low ecological value because of their poor diversity and most of the species identified are common, widespread and typical to such habitats in Hong Kong. Of some conservation interest was the gorgonian Euplexaura sp. coral whose distribution was clustered on the shipwreck at the north of the bay. Gorgonians are not uncommon across Hong Kong coastal waters and are often encountered in turbid western waters owing to their ability to tolerate high sedimentation and reduced salinity.

 

4.55          Marine mammal habitats are considered to be of high value in the Assessment Area. Dolphins are to be found in significant numbers in the Assessment Area throughout the year, using the area as a feeding ground, and possible breeding ground.

 

Identification of Environmental Impacts

 

4.56          Impacts to marine ecological resources may arise during the construction and operation phases of the Project.  The impacts may result from direct disturbance to the habitat and indirect disturbance through changes to key water quality parameters.

 

Construction Phase

 

4.57          The potential marine ecological impacts arising from the construction activities may include:

 

·        direct impact from loss of intertidal, subtidal and marine mammal habitats due to jetty and catwalk construction;

·        direct impact from loss of subtidal and marine mammal habitats due to dredging of approach channel and jetty foundations;

·        direct impact on dolphins from noise generated by construction activities especially dredging and rockfilling works;

·        direct impact on dolphins from noise generated by increased marine traffic; 

·        indirect impacts to the intertidal and subtidal habitats and associated fauna due to changes in water quality, which in turn could affect the fish species that dolphins feed on (such as alteration of prey resources abundance and distribution); and

·        indirect impacts to the gorgonian seawhips occurring in the subtidal habitat due to potential change in water quality and increased sedimentation rate.

 

4.58          Removal of the existing jetty may have marine ecological impacts that may include:

 

·        direct impact on dolphins from noise generated by demolition works

 

Operation Phase

 

4.59          The easier access due to the completion of jetty may increase illegal marine traffic to the Assessment Area, which would increase underwater noise pollution and the potential for physical harm to the dolphins by vessel movements in the surrounding area. Infrequent maintenance dredging may also affect dolphin behaviour.

 

Evaluation of Ecological Impacts

 

4.60          An evaluation of the above ecological impacts on each of the habitats has been conducted in accordance with the EIAO TM Annex 8 Table 1.

 

Inter-tidal habitat

 

4.61          The potential ecological impacts during construction would be the loss of intertidal rocky shore habitat, approximately 0.002ha in area.  There would also be indirect impact from any uncontrolled construction activities. Given the low ecological importance of the affected intertidal area and that good construction practices will be implemented, limited impact is expected. The rubble mounds for the jetty and catwalk foundation and the concrete blockwork will provide new habitat for recolonisation by intertidal organisms.  Furthermore, removal of the existing jetty structure will return a small part of the bay to a more natural condition.

 

Table 4.6            Overall Impact Evaluation for Intertidal Habitat

Evaluation Criteria

Discussion

Habitat quality

Habitat quality is low

Species

No species of note were recorded in the Assessment Area

Size/Abundance

The area affected is small (0.002ha)

Duration

The duration of impact will persist during construction and operation phases.

Reversibility

Habitat loss is irreversible

Magnitude

The scale of habitat loss is small in the context of the surrounding similar habitats.

Overall impact conclusion

Low

 

Subtidal habitat (Infauna and Corals)

 

4.62          Dredging for the approach channel and jetty foundation would result in the loss of approximately 0.2ha and 0.03ha, respectively, of subtidal habitat.  Surveys around Sha Chau have revealed that the soft bottom benthic species are typical of benthic communities in the coastal areas of Hong Kong while no benthic organisms were encountered in sediment grab samples taken from the immediate vicinity of the proposed jetty location.  The loss of soft bottom benthos due to the construction works is therefore not expected to be significant.

 

4.63          Corals present in the subtidal zone may be indirectly affected by water quality deterioration, particularly siltation resulting from dredging. Smothering by sediment on coral polyps may hinder coral feeding leading to stress, bleaching and tissue necrosis.  In order to safeguard corals, it is understood that the criteria that marine works should not cause sedimentation rates onto coral habitat to exceed 0.1kg/m2/day has been adopted for EIA Studies.[1] From the water quality modelling results presented and discussed in Section 3, it is evident that the effect of dredging on the sedimentation rate on the gorgonians at the shipwreck after deploying silt curtain mitigation, is negligible.  The additional sedimentation at the shipwreck site caused by dredging is predicted to be no more than 0.02 – 0.05 kg/m2/day.  This is far below the 0.1kg/m2/day criteria.  The indirect impact of dredging-induced sedimentation on gorgonians at the shipwreck site is therefore predicted to be minimal and environmentally acceptable.

 

4.64          In addition to the abundant gorgonians at the shipwreck site, several colonies were present close to the proposed jetty location.  These 6 gorgonian colonies will not be directly impacted by dredging.  However, they are in close proximity to the proposed dredged area and could be indirectly impacted by elevated sedimentation rates.  Nevertheless, water quality modelling results indicate that the sedimentation rate next to the proposed jetty location where the small number of gorgonians are present, will be less than 0.01 kg/m2/day.  This indicates that indirect impact on these small number of gorgonians near the proposed jetty location would be acceptable based on the 0.1 kg/m2/day sedimentation rate criteria.

 

4.65          In any case, gorgonians are highly tolerant of high turbidity conditions. Owing to their flexible branches and erect growth forms, it is known that gorgonians are not prone to sediment accumulation. The criteria on sedimentation rate is designed to provide protection to coral groups which are more susceptible than the gorgonians.

 

4.66          Potentially, there may also be indirect impacts on marine life establishing on artificial reefs deployed to west of Sha Chau (Figure 4.1) because of higher sedimentation rates as a consequence of dredging works. Nevertheless, water quality modelling (see Appendix 3.1) indicates that elevation of sediment concentrations in the water column at this Artificial Reef Site will be negligible.  Under mitigated conditions, sedimentation rates at the Artificial Reef Site will not exceed 0.001 kg/m2/day. In this way, the potential impact on the Artificial Reef Site is rated as negligible.

 

4.67          It is recommended that the water quality mitigation measures in Section 3 are strictly implemented to minimise the loss of suspended solids to the water column during dredging works.

 

Table 4.7            Overall Impact Evaluation for Subtidal Habitat

Evaluation Criteria

Discussion

Habitat quality

Habitat quality is low

Species

No species of note were recorded in the Assessment Area except Euplexaura sp.

Size/Abundance

The impacted area is small/ medium in size (0.03ha/0.2ha)

Duration

The duration of impact will persist during construction and operation phases.

Reversibility

Habitat loss is reversible at approach channel, dredged area may be recolonised by benthic organisms.  Habitat loss at jetty footprint is irreversible

Magnitude

The scale of habitat loss is small in the context of the surrounding similar habitats.

Overall impact conclusion

Low

 

 

Marine Mammal Habitats

 

4.68          The coastal waters east of Lung Kwu Chau form an important habitat for S. chinensis and will be affected by the project in a number of ways:

 

4.69          Habitat loss/alteration - Areas of dolphin habitat will be lost or destroyed due to the project works.  The construction of the Lung Kwu Chau jetty and dredged approach channel will eliminate a small, but very important, area of dolphin habitat off the east coast of Lung Kwu Chau.  In addition, the construction works and additional activities in the area during the operational phase of the jetty may cause additional impacts to the dolphins such as alteration of prey resources abundance and distribution.

 

4.70          Direct loss of the jetty area as dolphin habitat is unavoidable. However, together with the proposed dredging area, the area of habitat loss is small in size and extremely small in the context of surrounding available habitat. Nevertheless, steps can be taken to minimize the effects and to reduce the potential for other types of habitat alteration that may have detrimental effects on the animals.

 

4.71          Construction and demolition noise – As cetaceans are protected under the Wild Animals Protection Ordinance (Cap 170), 1980 any lethal and sublethal impacts due to underwater noise on marine mammals will be deemed unacceptable. Studies have shown that because of the efficient transfer of sound in water, dolphins can detect noises associated with vessels similar to dredgers at distances up to approximately 5 km. Noise disturbance interferes with communication and echolocation pulses which are used for navigation and feeding, leading to behavioural changes. There is evidence suggesting that some cetacean species will minimise their use of areas affected by underwater noise.

 

4.72          Dolphins in the Sha Chau area just south of the present work area showed evidence of behavioral disturbance during piling activities involved in construction of the AFRF in the late 1990s. In addition, there was a general decrease in dolphin numbers in the North Lantau area during this period of time, which is likely to be at least partially attributable to the AFRF construction (Jefferson 2000b). While the effects were largely temporary and dolphins are now showing evidence of recovery (Jefferson, unpubl.), this kind of impact in such a critical area of dolphin habitat should be avoided in the course of the present project. 

 

4.73          The potential for large-scale noise impacts is much less for this project than it was for the AFRF, because the present project is much smaller in scale and the proposed jetty design is of concrete blockwork, rather than a piled facility.  If appropriate mitigation measures are employed, the potential for significant impacts should be minimal.

 

4.74          Degradation of water quality - Introduction of environmental contaminants (especially heavy metals such as mercury and organochlorines) can have damaging effects on dolphins.  In addition, alteration of physical water characteristics may influence prey and therefore affect the animals indirectly. Because of the dynamic nature of local waters and tidal and current influences, this issue is potentially very important. 

 

4.75          Indirect impacts to marine ecological resources during the construction phase include sediment release associated with dredging work for the project.  Potential impacts to water quality from sediment release are listed below:

 

·        increased concentrations of suspended solids (SS);

·        a resulting decrease in DO concentrations; and

·        increases in contaminants.

 

Suspended Solids

 

4.76          It is recognised that high SS levels do not have a direct impact on dolphins. Chinese White Dolphins are well-adapted for hunting in turbid waters owing to their use of echolocation rather than visual information.  In addition, dolphins are air breathing and therefore SS in the water column have no effect on their respiratory surfaces. Nevertheless, impacts can occur to these mammals as an indirect result of increased SS levels through altered prey distribution.

 

4.77          Mobile animals such as marine mammals and fish have the ability to avoid areas where SS levels have increased, thus avoiding any impacts. It is also known that benthic fauna inhabiting estuarine environments, such as those in the Assessment Area, are generally not impacted by high SS levels. These benthic communities are well-adapted to tolerating periods of high turbidity conditions which occur naturally as high SS loadings are delivered by river discharge.

 

4.78          The Chinese White Dolphin, Sousa chinensis, in Hong Kong waters feed primarily on fish. Indirect impacts on dolphins may therefore occur through altered distribution of these prey. Dolphins are often seen associated with pair trawlers which are likely to provide them with increased feeding opportunities; this appears to be confirmed by the limited data available from stomach contents analyses. By examining the stomachs of 12 stranded dolphins, Jefferson (1998) found that, with the exception of one individual’s stomach content which contained some squid remains, only fish had been consumed.  At least twenty species of fish belonging to 13 families were found in the stomach of these stranded dolphins. The most abundant families were anchovies - Engraulidae, croakers - Sciaenidae, and sardines - Clupeidae accounting for more than 81% of all fish in the stomachs of the stranded dolphins.  Parsons (1997) who also analysed stranded dolphin stomach contents made the same findings but also reported small numbers of crustaceans. Information  on the fish fauna in the Assessment Area is available through the Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme. Fish surveys using handlines and baited traps indicate that fishes known to be part of the dolphin diet dominated the fish survey catch in the Marine Park. However, results from these fish surveys also appear to show that fish abundance tends to be highest around Sha Chau rather than off Lung Kwu Chau (HKIEd 2001).

 

4.79          The indirect impact of elevated SS levels associated with dredging works has been evaluated. Elevated SS levels due to dredging is not predicted to have a significant indirect impact on dolphins. Water quality modelling predictions (see Section 3) with silt curtain mitigation indicate minimal elevation of SS levels affecting only a narrow corridor close to the Lung Kwu Chau eastern coastline which is unlikely to significantly alter prey distribution.

 

Dissolved Oxygen Concentrations

 

4.80          The relationships between SS and DO are complex, with increased SS in the water column combining with a number of other effects to reduce DO concentrations in the water column. This has a particularly adverse effect on the eggs and larvae of fish, as at these stages of development, high levels of oxygen in the water are required for growth due to their high metabolic rate. Although respiratory responses and tolerance of hypoxia were studied in two marine fish, it is not possible to set critical thresholds for this parameter for other marine organisms due to lack of tolerance data for species in Hong Kong.

 

4.81          Changes in DO in the water column have been addressed using water quality modelling (see Section 3).  Based on the water quality modelling results, it is not predicted that there will be significant changes in DO levels.  For this reason, changes in DO levels are not predicted to have a significant indirect impact on the marine communities.

 

Inorganic Contaminants

 

4.82          Introduction of environmental contaminants desorbed from suspended sediment particles (especially inorganic contaminants such as mercury as well PCB and PAH) can have damaging effects on dolphins due to bioaccumulation effects. As discussed in the water quality assessment, chemical analyses indicate that the marine sediments off Lung Kwu Chau can be characterised as Category L uncontaminated mud. Consequently, unacceptable indirect impacts to marine mammals from contaminated release during dredging works are not predicted to occur.

 

4.83          To afford maximum protection to the Chinese White Dolphin, mitigation measures will be required to minimize impacts on water quality from sediment resuspension during dredging.

 

4.84          Increased vessel traffic - Dolphins in Hong Kong have been found to have been killed and injured by vessel collisions (Parsons & Jefferson, 2000).  This appears to be one of the most significant human impacts on dolphins. Additionally, vessel passes and noise can cause behavioral disturbance to these animals. A moderate increase in the number of large, slow-moving (less than 10 knots) vessels in the area should not cause a significant impact to dolphins. Smaller, faster outboard-driven boats would pose a bigger threat, because of the fast approach speeds and greater potential for high frequency noise.

 

4.85          The construction and operation of the jetty will necessarily involve increased levels of vessel traffic in the Lung Kwu Chau area.  However, the relatively small scale of the facility and the enforcement of the vessel speed restriction in the Marine Park should ensure that the potential impacts would be minimised.

 

Table 4.8            Overall Impact Evaluation for Marine Mammal Habitat

Evaluation Criteria

Discussion

Habitat quality

The overall habitat quality of coastal waters is average, but the area provides a  valuable habitat for S. chinensis 

Species

Impacts can expected to have a deleterious affect on S. chinensis 

Size

The area to be affected is small

Duration

The duration of impact will persist during construction and operation phases.

Reversibility

Habitat loss is irreversible

Magnitude

The scale of habitat loss is small in the context of the surrounding similar habitats.

Overall impact conclusion

Medium

 

Mitigation of Adverse Environmental Impacts

 

4.86          The above assessment indicates that during construction and operation phases of the Project, the direct and indirect impacts on intertidal communities and subtidal soft bottom assemblages are anticipated to be environmentally acceptable. The control of water quality to within acceptable levels during dredging works is expected to also control impacts on marine ecology.

 

4.87          The evaluation of impacts suggested that the most important ecological concerns arising from the project are direct and indirect impacts on S. chinensis. In accordance with the guidelines in the EIAO TM on marine ecology impact assessment the general policy for mitigating impacts to marine ecological resources, in order of priority, are:

 

·        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 (e.g. dredging rates) 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.

 

4.88          The following recommendations should be considered, if potential construction and operational phase impacts on dolphins are to be minimised:

 

·        The use of high-speed vessels in the construction or operation of the jetty should be avoided where possible.  If high-speed vessels must be used, they should be required to slow to under 10 knots which is the speed restriction for all marine traffic inside the Marine Park Boundary. Furthermore, marine traffic entering the Marine Park to the proposed jetty area should follow a regular and predictable route.

 

·        All vessel operators working on the project should be given a briefing, alerting them to the conservation significance of the Marine Park and the presence of dolphins in the area, and setting out guidelines for safe vessel operations around cetaceans.

 

·        A policy of no dumping of rubbish, food, oil, or chemicals should be strictly enforced.  This should also be covered in the contractor briefing.

 

·        Every attempt should be made to minimize the effects of construction and operation of the jetty on the water quality of the area.   Elevated SS levels due to dredging works for the approach channel and foundation of the jetty and catwalk are not predicted to have a significant impact on dolphins.  As a precautionary measure, however, it is considered beneficial to avoid dredging works during late spring to summer (i.e. May-August), when dolphins are at their peak abundance in North Lantau waters, as far as programming constraints allow.  It is recommended that the approach channel dredging works avoid the period of late spring to summer.

 

·        The jetty has incorporated a blockwork design with the provision of openings along the bottom of the catwalk to enhance seawater circulation. The most significant possible source of impact on dolphins would be noise damage and disturbance during piling and therefore use of piling has been avoided in the jetty design to avoid the danger posed to dolphins by the associated noise pulses. 

 

·        Before dredging the following steps must be taken:

 

-         An exclusion zone of 500m radius should be scanned around the work area for at least 30 minutes prior to the start of dredging.  If dolphins are observed in the exclusion zone, marine works should be delayed until they have left the area.  Furthermore, if dolphins enter the exclusion zone after dredging has commenced, marine works should cease until they have left the area.

-         Staff should monitor for the presence of dolphins within the exclusion zone by scanning the sea both with and without binoculars whilst positioned at vantage point near the summit of the hill behind the jetty location. The vantage point shall enable an extensive view of the 500m exclusion zone in all directions around the jetty. Staff shall communicate with the Engineer via a dedicated telecommunications device (e.g. mobile phone or ‘walkie-talkie’).

 

·        Other measures recommended to mitigate noise impact on dolphins by allowing their acclimatization to noise disturbance are to, as far as practicable:

 

-         The dredging works for the approach channel should avoid the period of peak dolphin abundance in North Lantau waters of late spring to summer (i.e. May-August).

 

-         The number of work vessels and small craft should be minimised during the construction phase.

 

-         Dredging and jetty construction activities should be continuous without short breaks or unpredictable noise outbursts at random intervals.

 

-         Events should be scheduled on a regular basis with similar activities planned for similar time period each day.

 

-         Furthermore, the Contractor should use quiet or ‘silenced’ plant equipment.  All site plant equipment should be well maintained.

 

·        Removal of the existing jetty structure should be done in a way that minimises noise impact on dolphins following the above measures. Blasting should not be permitted. Silenced breakers should be used and demolition and removal works of the submerged portion of the jetty should be carried out around low tide to minimise transmittance of noise into the water.  In addition, demolition of the jetty structure should be planned so that, as far as practicable, the structure is ‘cut’ into large manageable sections to minimise the amount of time breakers are used.

 

·        During the operational phase, vessels moored at the jetty for extended periods should, as far as practicable, turn off their engines to minimise unnecessary underwater noise.

 

·        Other mitigation measures, including measures to minimize impacts on water quality during dredging works, can be referenced from Section 3, Water Quality Impact.

 

Residual Environmental Impact

 

4.89          With the implementation of the mitigation measures recommended above, there will be residual marine ecological impacts associated with the proposed project with the loss of a small area of inter-tidal and sub-tidal habitats. This residual impact is considered acceptable because of the small area involved and low ecological value of the habitats. Additionally, colonisation of rubble mounds will partly compensate for lost habitats.  The loss of a small area of seabed on top of which the jetty and catwalk would be built will be permanent.  However, the loss of the benthic community from the dredged area beside the jetty during construction and infrequent operational maintenance would be temporary as this area would be available for recolonisation.  The residual impact on marine mammals is also considered acceptable because of the small scale of the works.  It is anticipated that the mitigation measures recommended in previous section should reduce impacts caused by increased human activity to an acceptable level.

 

Environmental Monitoring and Audit

 

4.90          The dredging operations include constraints which act as appropriate mitigation measures to control environmental impacts to within acceptable levels (see Section 3).  Actual impacts of construction activities will be monitored through impacts to water quality (see Section 3). EM&A activities designed to detect and mitigate any unacceptable impacts to water quality will serve to proactively protect against unacceptable impacts to marine ecological resources. The water quality monitoring programme will provide management actions and supplemental mitigation measures to be employed should impacts arise, thereby ensuring the environmental acceptability of the project.  In addition, site audits will be carried out to ensure strict implementation of the recommended mitigation measures.

 

Conclusions

 

4.91          Literature review of existing ecological conditions were supplemented by field surveys of marine ecological resources in the Assessment Area. This indicated that the ecological value of the intertidal sandy and rocky shore habitats and subtidal soft seabed at Lung Kwu Chau are of low ecological value. Construction of the jetty and associated dredging works will result in the loss of 0.2ha of subtidal seabed area and approximately 0.002ha rocky shore habitat.  The impact of the project works on these habitats is low.

 

4.92          The key marine sensitive receiver is Sousa chinensis with the Assessment Area being high value habitat to this dolphin species. This dolphin is commonly sighted off the north and east coast of Lung Kwu Chau and their abundance in North Lantau waters is generally greater from late spring to summer.  At this time of year, the peak abundance in these waters is estimated at 91 dolphin individuals (AFCD unpublished data).  Jefferson (2000) also reported peak dolphin abundance during summer in North Lantau waters, which was estimated at 105 dolphin individuals. Although the impact of the Project on the marine dolphin habitat is medium, by strictly observing the recommended mitigation measures set out in Section 4.88, the impact on dolphins can be minimised to an acceptable level.  These mitigation measures primarily address ways to minimise noise impacts and physical dangers posed by marine traffic and works.  The evaluation of other potential impacts such as the direct and indirect affects of changed water quality due to dredging indicates that no significant impacts are predicted. 

 

4.93          Common gorgonian corals from the genus Euplexaura sp. were also found in the Assessment Area. These soft corals were found in abundance attached to a shipwreck on the northeast side of Lung Kwu Chau, while a handful of these corals were found growing on dumped material in the bay of the existing jetty.  There would be no direct impact on these corals. In addition, plume modelling of sediments suspended into the water column by dredging indicate that increases in sedimentation rates on these corals are minor and would not cause any significant impact.

 

 

 

References

 

Chan & Kwok (1988)

 

Chiu, H.M.C. & Morton, B. (1999).  The distribution of Horseshoe Crabs (Tachypleus tridentatus and Carcinoscorpius rotundicauda) in Hong Kong.  Asian Marine Biology 16: 185-196.

 

ERM (1994). Proposed Aviation Fuel Receiving Facility: Environmental Impact Assessment

 

Hong Kong Institute of Education (2000).  Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme Final Report May 2000.

 

Hong Kong Institute of Education (2001). Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme First Quarterly Report September 2001.

 

Hong Kong Institute of Education (2002). Sha Chau and Lung Kwu Chau Marine Park Monitoring Programme Second Quarterly Report February 2002.

 

Hung, S.K (2000). Ranging patterns of Indo-Pacific hump-backed dolphins (Sousa chinensis) in the Pearl River Estuary, People’s Republic of China. Unpublished M.Sc thesis. University of San Diego, USA.

 

Hung, S.K. & Jefferson, T.A. (in press)  Ranging patterns of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary, People’s Republic of China.  Marine Mammal Science.

 

Jefferson, T.A (1998). Population Biology of the Indo-Pacific Hump-Backed Dolphin in Hong Kong Waters: Final Report. Ocean Park Conservation Foundation.

 

Jefferson, T.A (2000). Population Biology of the Indo-Pacific Hump-Backed Dolphin in Hong Kong Waters.  Wildlife Monographs No. 144.  Supplement to The Journal of Wildlife Management 64(4).

 

Jefferson (2000b)  Conservation biology of the the finless porpoise (Neophocaena phocaenoides) in Hong Kong waters: Final Report.

 

Morton B. & Morton J. (1983).  The Sea Shore Ecology of Hong Kong. Hong Kong University Press.

 

Parsons E.C.M.., Felley, M.L. & Porter, L.J. 1996.  An annotated checklist of cetaceans recorded from Hong Kong’s territorial waters.  Asian Marine Biology 12: 79-100

 

Parsons E.C.M. 1997.  Hong Kong’s cetaceans: the biology, ecology and behaviour of Sousa chinensis and Neophocaena phocaenoides.  Unpublished Ph.D thesis.  The University of Hong Kong.

 

Parsons & Jefferson 2000.  Post-mortem investigations on stranded dolphins and porpoises from Hong Kong waters.  Journal of Wildlife Diseases 36: 342-356

 

WWF (1994).  Hong Kong Vegetation Map.  Government Printer.

 

 


[1]                 Focussed Cumulative Water Quality Impact Assessment of Sand Dredging at the West Po Toi Marine Borrow Area (ERM, 2001); Green Island Reclamation Feasibility Study (Babtie and ERM, 1999); Western Harbour Submarine Gas Pipeline and Associated Stations EIA Study (Maunsell, on-going).