7.1.1
International
legislation relevant to this study includes:
¨ the UN Biodiversity Treaty which includes the Indo-Pacific humpback dolphin (Chinese white dolphin; Sousa chinensis Osbeck, 1765) as a protected species; and
¨ the Convention on the International Trade in Endangered Species of Flora and Fauna (CITES) which lists Sousa chinensis in Appendix One.
7.1.2
Relevant
¨ the Wild Animals Protection Ordinance (Cap. 170) 1980 which protects cetaceans;
¨ the Animals and Plants (Protection of Endangered Species) Ordinance (Cap. 187) 1988 which includes the protection of all stony corals, cetaceans and sea turtles;
¨ the Marine Parks Ordinance (Cap. 476) 1995 which applies to the marine park at Sha Chau and Lung Kwu Chau and limits certain activities in this area; and
¨ reference has also been made to Annexes 8 and 16 of the Technical Memorandum EIAO (Cap. 499) 1997 which sets out general criteria for evaluating the ecological importance of and hence the significance of potential ecological impacts and guidance for ecological assessment, respectively.
7.2 Key Sensitive Ecological Receivers
7.2.1 The proposed pipeline route passes through habitat utilised by Indo-Pacific Humpback dolphin. In addition, percussive piling for the jetty may have resulted in submarine noise that can be harmful to these marine mammals. Liu and Hills (1997) have stressed that in situations where an endangered species such as the Indo-Pacific Humpback dolphin is subjected to aggregated impacts, there is a strong case for a species-based ecological assessment which would seek an integrated and coordinated solution to predicting and mitigating potential impacts. For this reason, owing to the status and conservation importance of the dolphin, a species-based ecological assessment is required for the Indo-Pacific humpback dolphin. A location map showing the distribution of the key species of conservation concern and important ecological features in the study area is presented in Figure 6.2.
7.2.2 Construction of the pipeline and PAFF berthing jetty will not be approved unless it can be demonstrated that no unacceptable environmental impacts will result to the dolphins and other sensitive ecological receivers identified under this study. The ecological receivers potentially impacted by the PAFF (predominantly during the construction phase) comprise the following:
¨
benthic macro-invertebrate epifauna and infauna;
¨
corals;
¨
horseshoe crabs (Tachypleus
gigas, T. tridentatus and Carcinoscorpius
rotundicauda);
¨
Indo-Pacific Humpback dolphin (Sousa chinensis);
¨
artificial reefs (ARs) at Sha Chau; and
¨
Sha Chau and
7.3 Objectives of the Ecological Impact Assessment
7.3.1
The
ecological assessment examines the faunal, floral and ecological attributes of
the study area with an aim to protect, maintain or rehabilitate the existing
condition and particular emphasis was placed on avoiding impacts to recognised
sites of conservation importance such as the Sha Chau and Lung Kwu Chau Marine
Park, the Artificial Reefs placed in the Marine Park and species of
conservation interest such as the Indo-Pacific Humpback dolphin (Sousa chinensis), the three Horseshoe
crab species present in Hong Kong waters (Tachypleus
gigas, T. tridentatus and Carcinoscorpius
rotundicauda), benthic communities and corals. In order to achieve the
aforementioned measures relating to aquatic ecological impacts the following
key issues were addressed:
¨ reference was made to Annexes 8 and 16 of the Technical Memorandum EIAO (Cap. 499) 1997 which sets out general criteria for evaluating the ecological importance of and hence the significance of potential impacts and guidance for ecological assessment, respectively;
¨ the assessment area included the Sha Chau and Lung Kwu Chau Marine Park and all areas within at least 500m from the project area including the pipeline alignment, areas with frequent vessel movement during the operational phase and any other areas further afield (i.e., at distances greater than the 500m required by the TMEIAO) potentially impacted by the project; and
¨
sites of conservation
importance and other ecological sensitive areas including the Sha Chau and
7.3.2
The
assessment also had the following major objectives:
¨ review and collate the findings of other studies in the study area and other available information regarding the ecological characteristics;
¨ evaluation of the information collected and identification of any information gaps relating to the assessment of potential ecological impacts to the marine environment;
¨ establish the general ecological profile and describe the characteristics of each habitat found and major information shall include:
- description of the physical environment;
- ecological characteristics of each habitat type such as size, type, species present, dominant species found, species diversity and abundance, community structure, seasonality and inter-dependence of the habitats and species, and presence of any features of ecological importance;
- representative colour photographs of each habitat type and any important ecological features identified;
- investigate and describe the existing wildlife uses of various habitats with special attention to those habitats with conservation interest; and
- species found that are rare, endangered and/ or listed under local legislation, international conventions for conservation of wildlife or habitats or red data books.
¨ describe all recognised sites of conservation importance in the assessment area and describe how these sites will be affected by the proposed development;
¨ using suitable methodology, identify and quantify as far as possible, any direct, indirect, on-site, off-site, primary, secondary and cumulative ecological impacts such as destruction of habitats, reduction of species abundance or diversity, loss of feeding and breeding grounds, reduction of ecological carrying capacity and habitat fragmentation; with particular emphasis on the following:
- impact of habitat disturbance associated with dredging and backfilling of the pipeline route;
-
impact of habitat loss and
disturbance to wildlife arising from any works carried out in the Sha Chau and
- impact on hard and soft bottom assemblages as well as other marine organisms; and
- impacts upon resources of conservation importance during operations including spillage, maintenance as well as hazard risks (risk assessment of a fuel spill is presented in Section 11).
¨ assess the impact on the Indo-Pacific Humpback dolphin (Sousa chinensis) with particular emphasis on the following:
- review and incorporate the findings of relevant studies including the previous dolphin studies and collate the available information regarding the ecological characters of the assessment area;
- evaluate the information collected and identify any information gaps relating to the assessment of potential impacts on the dolphins;
- assess the impacts on the dolphin due to disturbance, loss of habitat and food supply;
- assess the cumulative impacts on the dolphins due to this project and any nearby dredging or reclamation works together with other existing or planned projects during construction;
- assess the disturbance of the dolphins habitat and the risk of the individuals being hit by vessel traffic in the vicinity of the facility during operation;
- identify precautionary and mitigation measures for protection of the dolphins. The proposed measures shall include those recommended in previous EIA and dolphin studies, such as ecological monitoring of the dolphins during the construction phase.
¨ evaluate the significance and acceptability of the ecological impacts identified using well defined criteria;
¨ recommend all possible alternatives and practicable mitigation measures to avoid, minimise and/ or compensate for the adverse ecological impacts identified with particular emphasis on the following:
- construction of the project at times that minimise impacts on the Indo-Pacific Humpback dolphin shall be considered, with the relative impacts of alternative schedules included; and
-
reinstatement of any habitats
in the Sha Cha and
¨ evaluate the feasibility and effectiveness of the recommended mitigation measures and define the scope, type, location, implementation arrangement, subsequent management and maintenance of such measures;
¨ determine and quantify the residual ecological impacts after implementation of the proposed mitigation measures;
¨
evaluate the severity and
acceptability of the residual ecological impacts using well-defined criteria;
and
¨
review the need for and
recommend any ecological monitoring programme, in particular on the
Indo-Pacific Humpback dolphin during the construction and operational phase.
7.4 Description of Existing Conditions
7.4.1.1 A review of relevant scientific literature, reports and EIA’s has been conducted in order to assist the assessment of baseline ecological conditions. The study area comprising the Northwestern waters is arguably one of the most extensively surveyed marine locations in Hong Kong and reports from the ongoing environmental monitoring and audit conducted at the contaminated mud pits (CMP’s) at East of Sha Chau (Mouchel, 1996; 2001a; Meinhardt, 2006a) provided a large amount of the marine ecological information. As monitoring at the CMP’s is on-going, the data also represents relevant and recent ecological information for the study area.
7.4.1.2 For the purposes of the ecological baseline assessment, owing to the higher mobility of certain faunal groups (such as dolphins and horseshoe crabs), the relative homogenous nature of the sediments (and hence benthos) and hard rock substrata present, the study area described in the following sections encompasses records of marine species that have been observed throughout the Northwestern waters roughly covering an area from Sham Tseng in the east to Lung Kwu Chau in the west. These extensive data facilitate an improved description of the existing ecological conditions in the waters of the wider study area than is possible by focussing to only within 500m of the PAFF study area as stipulated in the TMEIAO. Such reasoning would appear to be appropriate for the evaluation of the marine environment as marine species are often relatively mobile (for example, their larval stages are dispersed over wide spatial areas) and are potentially capable of colonising suitable substrata over wide areas. It should be noted, however, that the available data for the Indo-Pacific Humpback dolphin is highly location-specific (owing to intensive survey effort) and it is possible to describe the species’ distribution in the Northwestern waters to a greater level of accuracy.
7.4.1.3 Relevant scientific reports and papers have also been reviewed and a full list of studies cited is provided in the References section of this chapter. The major scientific studies and reports include the following:
¨ New Airport Master Plan (Greiner-Maunsell, 1991);
¨ Proposed Aviation Fuel Receiving Facility at Sha Chau: Environmental Impact Assessment (ERM, 1995);
¨ Feasibility Study & Environmental Impact Assessment for Aviation Fuel Pipeline (Montgomery Watson, 1996);
¨
EIA Study for Disposal of
Contaminated Mud in the
¨ Feasibility Study for Additional Cross-border Links Stage 2 (Mouchel, 1998);
¨ EIA for the Proposed Sand Extraction from The Brothers’ Marine Borrow Area (Hyder Consulting, 1998);
¨ Population Biology of the Indo-Pacific Hump-backed Dolphin (Sousa chinensis Osbeck 1765) in Hong Kong Waters. AFCD-funded study conducted by Ocean Park Conservation Foundation (Jefferson, 1998; 2000a , 2005; Hung, 2005).
¨ Environmental Monitoring and Audit for Contaminated Mud Pit IV at East of Sha Chau (ERM, 1999; Mouchel, 2001a; Meinhardt, 2006a); and
¨
EA Study for Backfilling of
Marine Borrow Pits at North of the Brothers (Mouchel, 2002a).
7.4.1.4
The study area is located in
the Northwestern waters of
7.4.1.5 The study area is located within the Pearl River Estuary and is strongly influenced by freshwater discharges especially during the wet season when the summer monsoon brings high levels of precipitation (peak wet season discharge of 1,800 M m3 day-1; Broom and Ng, 1996). The western waters are, therefore, predominantly low in salinity and high in turbidity and show a marked seasonality.
7.4.2
Present Eco-Physical
Characteristics of the Study Area
7.4.2.1 There have been numerous assessments of the physical, chemical and biological environment conducted in the study area (Greiner-Maunsell, 1991; Binnie Consultants, 1995; Mouchel, 1996; ERM, 1997, 2005; Hyder Consultants, 1998; Meinhardt, 2006a). There have also been several past and ongoing studies conducted and notable are those involving investigations of Marine Borrow Areas and the ongoing monitoring at the Contaminated Mud Pits at East of Sha Chau conducted for the Civil Engineering and Development Department (CEDD). Several of these studies provide pertinent marine ecological baseline information for the current study and field visits have also been conducted to confirm that no natural intertidal habitat will be affected by the project. Then field survey data that form the basis of the assessment are presented in subsequent sections below and cover a duration of greater than the six months (wet season) required by the Study Brief. The PAFF tank farm is located on reclaimed land at Tuen Mun Area 38 and there is no natural coastal habitat that will be affected by the construction or operation of the project. The berthing jetty used by the tankers for fuel delivery is located 200m off-shore from Tuen Mun Area 38. The vertical seawall interfacing with the sea is shown in Plate 7.1.
7.4.2.2 The major conclusion from the previous work conducted in the study area is that the marine benthic environment in the western waters of Hong Kong are generally characterised by soft-bottom material composed of silts and clay as a homogenous layer or in loosely packed mud clasts bound in a puzzle fabric (Binnie Consultants, 1995; ERM, 1999; Mouchel, 2001a) although coarser material under the influence of strong tidal currents has been reported from the area to the Northeast of The Brothers (Greiner-Maunsell, 1991). There are also some hard substrates present although the soft-bottom sediments are characteristic of the study area. The upper sediment layers are reported to be well oxygenated (EVS, 1996) and typical images of the composition of the benthic sediments (and ecological characteristics present in both soft-bottom and hard substrate) are presented in Figure 7.1. The heterogeneity of sediments present in the study area provides a wide variety of niches although owing to the prevailing estuarine conditions that lead to fluctuations in physico-chemical parameters, it is nevertheless a ‘naturally stressed’ environment and this is reflected in the relatively low to moderate diversity of burrowing in-fauna present compared to other locations in Hong Kong (Shannon-Weiner index H’ typically < 2; Mouchel, 2001a; Meinhardt, 2006c).
7.4.2.3 Comprehensive ecological surveys were conducted at the North of The Brothers MBA and around Chek Lap Kok in 1990 as part of the new airport core construction EIA (Greiner-Maunsell, 1991). These data together with the past ten years of extensive monitoring data obtained during the contaminated mud pit (CMP) monitoring at East of Sha Chau collected from various stations in Northwestern waters (ERM, 2001; Mouchel, 2001a; Meinhardt, 2006c) are the most relevant to the current study. The findings from the two aforementioned studies have, therefore, formed the basis for much of the following discussion.
7.4.3
Present Pollution Status
7.4.3.1
The sediments in the
Northwestern waters have recently been assessed using a suite of measurements
to calculate a Pollution Index. The index is derived through chemical
contaminant analysis, assessment of the benthic macro-infauna present and
toxicity testing with a marine amphipod. Results indicated that the sediment
Pollution Index for Northwestern waters was average and similar to the majority
of other locations in Hong Kong with the exception of
7.4.3.2 Recently, further assessment of the pollution status of the marine sediments in the study area has been evaluated at stations located to the south of Sha Chau (between the airport and Sha Chau) using key biological indicator organisms (to facilitate the calculation of biotic indices) present in the benthic communities. Biotic indices are considered to be sensitive, easily-understood measures of pollution and provide a synoptic evaluation of both the prevailing sediment quality and overlying water chemistry thus adding further information on the benthic communities present in the study area. Biotic indices calculated for benthic macroinvertebrates collected at locations to the south of Sha Chau in May 2001 were indicative of slight pollution and an unbalanced benthic community (Mouchel, 2001a; Meinhardt, 2006c). A low biotic index is, however, often typical of estuaries owing to their highly dynamic physical and chemical nature and the benthic community diversity is also typically lower at these locations (Mouchel, 2001a; Meinhardt, 2006c).
7.4.4.1 The macro-infauna consist of the organisms larger than 1mm living within the sediment (predominantly in the upper well-oxygenated layers). The foregoing discussion on the benthic macro-infauna present throughout the study area comprises data reviewed from several benthic community studies (review mostly based on Greiner-Maunsell, 1991; Binnie Consultants, 1995; ERM, 2001; Mouchel, 2001a, 2002b; CCPC, 2002; Meinhardt, 2006c) and species present are relatively similar throughout the North-western waters (and other areas in Hong Kong) and are representative of the general study area. As indicated below in Section 7.4.4.2, the major difference in the faunal groups/species recorded both in different studies and between locations in Northwestern waters is the occasional absence of echinoderms although this is more likely to be a reflection of freshwater inputs from the Pearl River (the larvae of these organisms are stenohaline) driving the distribution pattern. The benthic community results presented are, therefore, considered to be representative of the study area.
7.4.4.2
The monitoring results in the
study area have tended to indicate that the benthic community recorded over
approximately the past ten years has remained of similar composition and as
with most benthic communities polychaetes are numerically abundant comprising
between 44-71% of individuals present and molluscs, crustaceans and echinoderms
are well represented components of the soft-bottom community (Binnie
Consultants, 1995). Echinoderms are, however, not always recorded in the study
area (Greiner-Maunsell, 1991) as the larvae of these organisms are often
stenohaline (Nicholson, 2001) and unlikely to tolerate the wide salinity
fluctuations associated with freshwater exposures from the
7.4.4.3 Results of benthic sampling (collected with a Van Veen grab) conducted in the study area in the late wet season in August 2000 resulted in the collection of 72 sediment samples containing 6,512 macro-infaunal specimens belonging to 84 families comprising 9 different phyla (ERM, 2001). In terms of dominant families present in the soft sediments, the annelids, arthropods and molluscs were dominant and the latter group also constituted most of the biomass present (see Table 7.1a). Recent results of sampling conducted in May 2001 resulted in the collection of 72 sediment samples containing 9,283 macro-infaunal specimens belonging to 67 families comprising 9 different phyla (Mouchel, 2001a; see Table 7.1b). The total recorded biomass in May 2001 was 188.85 g and was largely due to the high mass of annelids and molluscs collected (see Table 7.1b). The benthic survey data collected in the late wet season in August 2001 ((Mouchel 2002b)) showed that in terms of families present, the annelids, arthropods and molluscs were again the most dominant. These families also comprised the majority of individuals present. Compared to the monitoring conducted in August 2000, there were fewer families recorded in both May and August 2001 although the annelids, arthropods and molluscs were consistently the most dominant families recorded. Comparing data within the early and late wet season of the same year, there were both more families and individuals recorded during the late wet season in August compared with May 2001. There was also higher biomass recorded in August compared to the previous monitoring in May 2001. In May 2001 a total biomass (wet weight) of 188.85g was recorded whereas 662.07g was recorded in August 2001. The precise reasons for the recorded differences between the data collected in May and August 2001 are difficult to ascertain although they may represent differences in recruitment variation between the late dry/early wet (May) and late wet (August) season months (Table 7.1b).
Table 7.1a Summary of the Macro-infauna Collected in August 2000
|
Phylum |
Number
of Identified Families |
Total
Number of Individuals |
Total
Biomass (g) |
|
Annelida |
34 |
4,914 |
27.88 |
|
Arthropoda |
20 |
1,131 |
39.25 |
|
Chordata |
3 |
5 |
3.24 |
|
Coelenterata |
7 |
35 |
3.05 |
|
Echinodermata |
4 |
80 |
53.75 |
|
Echiura |
1 |
1 |
0.45 |
|
Mollusca |
14 |
301 |
847.72 |
|
Nemertinea |
0 |
19 |
1.51 |
|
Sipuncula |
1 |
26 |
0.11 |
|
Total |
84 |
6,512 |
976.97 |
Source: ERM (2001)
Table 7.1b Summary of the Macro-infauna Collected in May 2001
|
Phylum |
Number
of Identified Families |
Total
Number of Individuals |
Total
Biomass (g) |
|
Annelida |
30 |
2,204 |
45.609 |
|
Arthropoda |
13 |
405 |
26.526 |
|
Chordata |
2 |
2 |
2.352 |
|
Coelenterata |
4 |
13 |
1.329 |
|
Echinodermata |
2 |
15 |
0.723 |
|
Echinodetmata |
0 |
1 |
0.194 |
|
Mollusca |
11 |
6,600 |
95.562 |
|
Nemertea |
1 |
1 |
0.261 |
|
Sipuncula |
4 |
42 |
16.301 |
|
Total |
67 |
9,283 |
188.85 |
Table 7.1c Summary of the Macro-infauna Collected in August 2001
|
Phylum |
Number of Identified Families |
Total Number of Individuals |
Total Biomass (g) |
|
Annelida |
35 |
2,928 |
17.935 |
|
Arthropoda |
17 |
902 |
42.259 |
|
Chordata |
2 |
6 |
35.121 |
|
Coelenterata |
4 |
10 |
6.330 |
|
Echinodermata |
2 |
12 |
39.746 |
|
Mollusca |
10 |
9,4601 |
515.4731 |
|
Sipuncula |
2 |
18 |
5.208 |
|
Total |
72 |
13,336 |
662.07 |
Note: 1=
including Potamocorbula sp.
comprising 9390 individuals and biomass of 509.906 g.
Source: Mouchel (2002b)
7.4.4.4 The 2000/2001 data available for the study area comprising data collected over 12 months (wet season data only) showed that in terms of families present, the annelids, arthropods and molluscs were dominant. The annelids, molluscs and arthropods usually comprised the majority of individuals present. Although the number of families and biomass were lower than previously recorded in August 2000 there were a higher number of total individuals recorded in both May and August 2001 (Mouchel, 2001a, 2002b). During the sampling conducted in August 2000, 84 families and a total of 6,512 individuals were recorded for a total biomass of 976.9 g (ERM, 2001). The recorded differences between the data collected in August 2000 and the recent data collected in May and August 2001 may, however, represent seasonal variation between the late dry/ early wet and late wet season months inducing subtle changes to the benthic macro-infauna assemblages present.
7.4.4.5 However, the most recent data available are the surveys conducted in January and October 2005 (Mouchel, 2005a; Meinhardt, 2006b) covering both the dry and late wet seasons and the results are summarised in Table 7.1d below. The results were consistent with earlier surveys conducted under the EM&A programme. The annelids, molluscs and arthropods comprised the majority of individuals present and subtle seasonal variations, slightly higher abundance during the wet season, were frequently recorded.
Table 7.1d Summary of the Macro-infauna Collected in 2005
|
Phylum |
Number of
Identified Families |
Total Number of
Individuals |
Total Biomass
(g) |
|||
|
|
January |
October |
January |
October |
January |
October |
|
Annelida |
40 |
39 |
4,365 |
3,051 |
25.48 |
19.39 |
|
Arthropoda |
17 |
11 |
617 |
264 |
25.35 |
16.66 |
|
Chordata |
1 |
1 |
5 |
2 |
27.12 |
1.29 |
|
Coelenterata |
7 |
7 |
28 |
33 |
64.17 |
59.86 |
|
Echinodermata |
4 |
2 |
108 |
124 |
5.31 |
5.43 |
|
Echiura |
1 |
1 |
1 |
1 |
0.00 |
0.06 |
|
Mollusca |
10 |
12 |
164 |
70 |
171.92 |
81.75 |
|
Nemertinea |
- |
- |
- |
- |
0.57 |
0.03 |
|
Sipuncula |
1 |
2 |
43 |
67 |
0.31 |
23.01 |
|
Unidentified |
- |
- |
- |
- |
1.04 |
- |
|
Total |
81 |
75 |
5,331 |
3,612 |
321.26 |
207.48 |
Source: Mouchel (2005a) and Meinhardt (2006b).
7.4.4.6
High numbers of
macroinvertebrate infauna (67-81 families; Mouchel, 2001a; (Mouchel 2002b);
(Mouchel 2005a)) have been recorded in the study area. Abundance patterns in the Northwestern waters
appear to be reasonably similar to the macro-infauna recorded in the eastern
waters of
7.4.4.7 AFCD commenced a terrestrial-wide study on the marine benthic communities in Hong Kong in 2001 (CCPC, 2002) and concluded that in Hong Kong waters polychaetes, crustaceans and bivalves were the most abundant benthic fauna comprising over 70% of the total species. In terms of spatial pattern, it noted that the western waters, together with the north-eastern waters and Victoria Harbour showed distinct benthic composition as compared with the rest of the locations and the benthic species diversity and ecological importance of these three strata was generally lower. The estuarine conditions in the western waters largely accounted for the lower species diversity in the western waters.
7.4.4.8 Infauna diversity in the study area is relatively low (H’ < 2) compared to other areas in Hong Kong which is likely due to the proximity of Pearl River Estuary (estuarine areas are often less diverse owing to their highly dynamic physical and chemical nature) and possibly due to the predominantly silt-clay composition of the seabed that tends not to support high diversity (Shin, 1998; Mouchel, 2001a, 2002b).
7.4.5
Benthic Macro-Epifauna
Invertebrates
7.4.5.1
The macro-epifauna comprise the
larger organisms (typically > 1mm) that tend to live on or in close
association with the sediment surface. Trawl surveys were conducted within the
study area (at locations around
Table 7.2 Summary of Invertebrate Trawl Catch in the
Vicinity of Sha Chau (Jan-Dec 1995)
|
Phylum |
Class |
Common Name |
Number of Species |
|
Arthropoda |
Crustacea |
Crab |
19 |
|
|
|
Mantis shrimp |
1 |
|
|
|
Shrimp/ Prawn |
13 |
|
Cnidaria |
Anthozoa |
Gorgonian coral |
1 |
|
|
|
Sea anemone |
1 |
|
|
|
Sea pen |
4 |
|
Cnidaria |
Hydrozoa |
Hydroid |
1 |
|
Echinodermata |
Asteroidea |
Starfish |
1 |
|
|
Echinoidea |
Sea urchin |
1 |
|
|
Holothuroidea |
Sea cucumber |
1 |
|
|
Ophiuroidea |
Brittle star |
1 |
|
Mollusca |
Bivalvia |
Bivalve |
8 |
|
|
Cephalopoda |
Cuttlefish |
2 |
|
|
|
Octopus |
1 |
|
|
|
Squid |
1 |
|
|
Gastropoda |
Snail and sea slug |
10 |
|
Platyhelminthes |
Turbellaria |
Flatworm |
1 |
|
Total No. of Species |
|
|
67 |
Source: ERM (1997)
7.4.5.2 Data on the benthic macro-invertebrate epifaunal communities present are also available from demersal trawls conducted in the study area during May 2001 (early wet season) for the EM&A for the CMPs (Mouchel, 2001a). Six trawling stations were sampled, two of these located to the north and east of Lung Kwu Chau, two around the CMPs and two were also surveyed to the west of the airport. The trawling gear and methods were similar to those described above although five tows are conducted at each station and the cod end mesh was 2 cm in diameter. Trawling revealed that there were 113 invertebrate species present, see Table 7.3. As recorded previously, there were numerous mollusc and crustacean species present and fewer echinoderms. Thirty-five species of crab were recorded and these represented the most numerous group of epifaunal macro-invertebrates present. The epifaunal (demersal fish, crustaceans and gastropods) diversity recorded in the study area is low (H’< 2; Mouchel, 2001a) which may reflect both the naturally-occurring stressors such as periodic fluctuations in the physico-chemical environment associated with Pearl River run-off and anthropogenic impacts such as high trawling pressures.
Table 7.3 Summary of Invertebrate Trawl Catch in the Vicinity of Sha Chau Collected in May 2001
|
Phylum |
Class |
Common Name |
No. of Species |
|
Arthropoda |
Crustacea |
Crab |
35 |
|
|
|
Mantis shrimp |
6 |
|
|
|
Prawn or Shrimp |
23 |
|
Cnidaria |
Anthozoa |
Sea anemone |
1 |
|
|
|
Sea pen |
2 |
|
|
Scyphozoa |
Jellyfish |
1 |
|
Echinodermata |
Asteroidea |
Sea star |
1 |
|
|
Echinoidea |
Sea urchin |
1 |
|
|
Holothuroidea |
Sea cucumber |
3 |
|
Mollusca |
Bivalvia |
Bivalve |
12 |
|
|
Cephalopoda |
1 |
|
|
|
|
Octopus |
1 |
|
|
|
Squid |
2 |
|
|
Gastropoda |
Snails and sea slugs |
24 |
|
Total No. of Species |
|
|
113 |
Source: (Mouchel, 2001a)
7.4.5.3 However, more recent data on the benthic macro-invertebrate epifaunal communities present are also available from demersal trawls conducted in the study area during both the dry (January 2005) and late wet season (October 2005) in 2005 for the EM&A for the CMPs (Mouchel, 2005b; Meinhardt, 2006d). The results of the recent trawling, as presented in Table 7.4, were similar to those recorded in 2000/2001. As recorded previously, there were numerous mollusc and crustacean species present and fewer echinoderms. Thirty to thirty-two species of crab were recorded and these represented the most numerous group of epifaunal macro-invertebrates present. The epifaunal diversity recorded in the study area is low (H’< 2; Mouchel, 2005b; Meinhardt, 2006d).
Table 7.4 Summary of Invertebrate Trawl Catch in the Vicinity of Sha Chau Collected in 2005
|
Phylum |
Class |
Common Name |
No. of Species |
|
|
January |
October |
|||
|
Annelida |
Polychaete |
Polychaetes |
- |
1 |
|
Arthropoda |
Crustacea |
Crab |
30 |
32 |
|
|
|
Mantis shrimp |
5 |
6 |
|
|
|
Prawn or Shrimp |
17 |
14 |
|
Cnidaria |
Anthozoa |
Gorgonian coral |
1 |
1 |
|
|
|
Sea anemone |
1 |
1 |
|
|
|
Sea pen |
3 |
3 |
|
|
Scyphozoa |
Jellyfish |
1 |
1 |
|
Echinodermata |
Echinoidea |
Sea urchin |
2 |
1 |
|
|
Holothuroidea |
Sea cucumber |
3 |
3 |
|
Echiurid |
Echiuridae |
Echiurids |
1 |
- |
|
Mollusca |
Bivalvia |
Bivalve |
11 |
13 |
|
|
Cephalopoda |
Cuttlefish |
2 |
1 |
|
|
|
Octopus |
1 |
1 |
|
|
|
Squid |
1 |
1 |
|
|
Gastropoda |
Snails and sea slugs |
29 |
17 |
|
Total No. of Species |
108 |
96 |
||
Source: (Mouchel, 2005b; Meinhardt, 2006d)
7.4.6.1
There have been three species
of horseshoe crab recorded in Hong Kong coastal waters and although these
species are distributed throughout
7.4.6.2
Most of the horseshoe crabs
recorded in the Tuen Mun area have been previously identified as Tachypleus gigas (ERM, 1997; Chiu and
Morton, 1999). In an extensive study of the distribution of horseshoe crabs in
7.4.6.3
It has been suggested that the
horseshoe crabs show a seasonal trend in
7.4.6.4 Specimens of horseshoe crabs collected in the vicinity of the study area during March to September 1996 (ERM, 1997), records mostly from March 1995 to June 1998 (Chiu and Morton, 1999), September 2003 to May 2004 (Mouchel, 2004) and May 2001 to January 2005 (Mouchel, 2005b) are presented below in Table 7.5. The spatial distribution of horseshoe crabs in Northwestern waters is presented in Figure 6.2.
Table 7.5 Horseshoe Crab Sightings and Landings in the Study Area between June 1987 and January 2005
|
Location |
Species/ Remarks |
Date |
Number of
Individuals |
Biomass (g) |
|
Lung Kwu Chau |
Tachypleus gigas |
Jun, 1996 |
1 |
380 |
|
|
Tachypleus gigas |
Aug, 1996 |
1 |
325 |
|
|
Tachypleus sp. |
May, 2001 |
1 |
Not recorded |
|
|
Tachypleus tridentatus adult female |
Aug, 2001 |
1 |
Not recorded |
|
East of Sha Chau |
Carcinoscorpius rotundicauda adult |
Jul, 1995 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juvenile |
Jan, 2004 |
1 |
Not recorded |
|
Lung Kwu |
Tachypleus tridentatus mating pair |
Jun, 1987 |
2 |
Not recorded |
|
Sheung Tan |
Tachypleus tridentatus adult |
Jun, 1905 |
1 |
Not recorded |
|
|
Tachypleus tridentatus mating pair |
May, 1995 |
2 |
Not recorded |
|
|
Unknown juvenile |
Mar, 1998 |
1 |
Not recorded |
|
Sha Lo Wan |
Unknown juvenile |
Apr, 1995 |
1 |
Not recorded |
|
Nim Wan |
Unknown juveniles |
May, 1995 |
8 |
Not recorded |
|
Tuen Mun |
Tachypleus tridentatus adult (dead) |
Jun, 1995 |
1 |
Not recorded |
|
The Brothers |
Unknown juvenile |
Apr, 1995 |
1 |
Not recorded |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
1667 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
1667 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
3636 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
3030 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
227 |
|
|
Tachypleus sp. |
May, 2001 |
1 |
Not recorded |
|
San Tau |
Unknown |
May, 1995 |
~ 13 |
Not recorded |
|
|
Tachypleus tridentatus and |
Oct, 1997- |
~ 15 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Jun, 1998 |
|
|
|
|
Tachypleus tridentatus 5 males, 6 females |
Apr, 1997 |
11 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Jun, 2002 |
57 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juvenile |
Nov, 2003 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Nov, 2003 |
10 |
Not recorded |
|
|
Tachypleus tridentatus |
May, 2004 |
11 |
Not recorded |
|
Tung Chung Wan |
Tachypleus tridentatus 5 males, 6 females |
Apr, 1997 |
11 |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
Apr, 1997 |
1 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Jun, 2002 |
2 |
Not recorded |
|
|
Tachypleus tridentatus |
May, 2004 |
15 |
Not recorded |
|
|
Tachypleus tridentatus 13 males, 8 females |
Oct, 1997 |
21 |
Not recorded |
|
Hau Hok Wan |
Carcinoscorpius rotundicauda juvenile |
Nov, 2003 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Nov, 2003 |
2 |
Not recorded |
|
Sham Wat |
Unknown juvenile |
Oct, 2003 |
> 10 |
Not recorded |
|
|
Tachypleus tridentatus |
Apr, 2004 |
1 and 3 molts |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
Jan, 2005 |
1 |
189.4 |
|
Tai Ho Wan |
Unknown juvenile |
Sep, 1998 |
1 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juvenile |
Jun, 1999 |
8 |
Not recorded |
|
|
Carcinoscorpius rotundicauda mating pair |
Jun, 1999 |
2 |
Not recorded |
|
|
Tachypleus tridentatus |
Jun, 1999 |
2 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Dec, 2003 |
20 |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
May, 2004 |
14 and 3 molts |
Not recorded |
Note: Although Tachypleus gigas has
been reported in the wider study area, it may have been misidentified as Chiu
and Morton (1999) only recorded the similar Tachypleus tridentatus during
extensive surveys of the Northwestern waters. Adapted from AFCD (pers. comm.);
ERM (1997), Chiu and Morton (1999); Fong (1999); Huang (1997); Mott Connell Ltd
(2003); Mouchel (2004; 2005b).
7.4.7.1
Solitary corals have been
reported from the study area in the region around East Sha Chau and further to
the east at Sham Tseng and Tsing Lung Tau adjacent to
7.4.7.2
Corals are usually adversely
affected by reduced salinity (hyposalinity) and coupled to the high levels of
suspended solids discharged by the Pearl River (and hence low light
penetration) the absence of many hermatypic corals from the study area is not
unexpected. The coral communities of the study area are sparse compared to
rocky reefs of similar depth and exposure in the higher saline oceanic eastern
and southern waters of Hong Kong although a number of ahermatypic cup corals
(thought to be Balanophyllia or Phyllangia sp.), pale-blue gorgonian (Euplexaura sp.), Dendronephthya sp. colonies, isolated sea pens (Virgularia or Pteroides sp.) and one hermatypic coral Oulastrea crispata were recorded in June 2001 the far eastern
Northwest waters (at Sham Tseng and Tsing Lung Tau; Mouchel, 2001b; Figure
7.1). Similar results were also recorded
in dive surveys at Lung Kwu Chau in November 2001 (Maunsell, 2002). Coral dives survey conducted in Ocotber 2003
around along the tentative alignment for the HKZM Bridge recorded low abundance
(<5% cover) of one hard ahermatypic coral, Balanophyllia sp. on hard
substrate to the west of HKIA at Sham Wat/San Shek Wan, but not the eastern or
southern side (Mouchel, 2004). Low abundance (<5% cover) soft coral Echinomuricea
sp. was also recorded in the October 2003 survey at the eastern and
southern sides of the HKIA, but not the western side (Mouchel, 2004). It is
notable that the ahermatypic cup coral (Balanophyllia
or Phyllangia sp.) and the
pale-blue gorgonian (Euplexaura sp.)
have only rarely been recorded in the oceanic eastern and southern waters of
7.4.8
Cetaceans (Dolphins and
Porpoises)
7.4.8.1 There are sixteen recorded cetacean species from Hong Kong waters although only two of these species, the Indo-Pacific Humpback dolphin (Sousa chinensis) and Finless porpoise (Neophocaena phocaenoides) are resident (Parsons et al., 1995). Until the early 1990s there were few records of Sousa chinensis in Hong Kong waters (Jefferson and Leatherwood, 1997) although construction of the international airport at Chek Lap Kok drew attention to the presence of the Indo-Pacific Humpback dolphin in local waters and intensive research into the distribution and conservation requirements of the species have been ongoing since about the mid 1990s.
7.4.8.2 Although other cetaceans (Finless porpoise and False killer whale) have been found in the Northwestern waters, these are probably extralimmital records and only the Indo-Pacific Humpback dolphin has so far been consistently reported from the study area (comprising the area from Tuen Mun to the Southwest of the airport) where it is widely distributed (Parsons et al., 1995; Jefferson and Leatherwood, 1997; Jefferson, 2000a, 2005; Hung, 2005). There appears to be only limited overlap in distribution of the Indo-Pacific Humpback dolphin and Finless porpoise in local waters as the dolphin tends to be predominantly distributed in the western waters whereas the porpoise is usually recorded from areas further to the east of Hong Kong (the southern coast of Lantau around Fan Lau and the Soko Islands predominantly marks the western edge for the distribution of Neophocaena phocaenoides; Parsons et al., 1995; Jefferson, 2000a; Hung, 2005).
7.4.8.3
Globally, the Indo-Pacific
Humpback dolphin is widely distributed throughout shallow (< 20 m) coastal
waters of the Indian and
7.4.8.4
Groups of Indo-Pacific Humpback
dolphin are consistently recorded from waters near Tuen Mun and off Lung Kwu
Chau, Sha Chau and around HKIA although the distribution in Hong Kong may be
presently more restricted than when the population was assumed to contain more
individuals in the past (Parsons et al.,
1995). It should be noted, however, that no reliable census data are available
prior to the construction of the HKIA and the hypothesis that the population
was larger in the past is only an assumption.
The distribution of the dolphin tends to show a slight seasonal response
(possibly related to feeding opportunities, as the species is known to feed
predominantly on estuarine fish) as individuals tend to move further to the
east of the study area during the summer monsoon when ambient seawater is lower
in salinity (Jefferson, 2000a). In the dry season (winter and spring) the
population tends to be concentrated in the waters around the Sha Chau and
7.4.8.5 In addition, a six day baseline monitoring survey of Indo-Pacific Humpback dolphins in and around the project area was conducted in late 2005 using transects (Figure 7.3a) as part of the pre-construction dolphin abundance monitoring required by the previous Environmental Permit (EP-139/2002/A). Over the six days survey, the number of sightings per survey day varied between 3 to 11 and the group sizes ranged between 1 to 8, although 1 to 2 individuals were observed in the majority of the cases. The locations of the sightings recorded during the baseline survey are presented in Figure 7.3b and the original report is presented in Appendix F3.
7.4.9.1
The ecological value of each
habitat present in the study area is largely based on the species present. For
example, habitat that contains species of conservation interest or serve as a
nursery or breeding grounds are considered to have high ecological value. The
marine waters present in the study area are the media used by the species of
highest ecological importance, the Indo-Pacific Humpback dolphin. The waters within
the
7.4.9.2 Criteria for evaluating ecological impacts to habitats in the study area were determined in accordance with criteria stipulated in Table 2 (Annex 8) of the TM. The ecological value of both the soft and hard substrates present within the study area are discussed below in Sections 7.4.9.3-7.4.9.7.
Soft-Bottom Benthic and Littoral Habitat
7.4.9.3
The benthic habitats in the
western waters of Hong Kong are generally characterised by soft-bottom material
composed of silts and clay as a homogenous layer or in loosely packed mud
clasts bound in a puzzle fabric (Binnie Consultants, 1995; ERM, 1999) although
coarser material under the influence of strong tidal currents has been reported
from the area to the Northeast of The Brothers (Greiner-Maunsell, 1991). The
species present in the benthos are common and have been recorded in similar habitats
throughout
7.4.9.4 There is also the occasional sandy shore present in the study area, notably at Sha Chau. Previous surveys of the sandy shore at Sha Chau have however revealed that it is biologically depauperate. Similar findings were also recorded in the more recent field surveys conducted at Lung Kwu Chau (Maunsell, 2002). Extremely low species numbers and biological diversity are, however, typical of exposed sandy shores in the study area where the substrate is unstable (Morton and Morton, 1983; ERM, 1995).
Hard-bottom Benthic and Littoral Habitat
7.4.9.5 Based on trawl surveys that have collected organisms that are exclusively found on hard substrate (such as mytilid mussels and certain corals) there is evidence of some hard bottom habitat within the study area. The hard substrates present would, however, appear to only form a small proportion of the overall study area. Hard substrate benthic habitat is not typical of the study area to be affected, although trawl surveys occasionally reveal the presence of exclusively hard substrate fauna such as mytilid mussels (e.g., Perna viridis; Mouchel, 2001a) indicating the presence of some small patches of hard benthic substrate (i.e., occasional rocks and small boulders). Closer to shore, there is also hard subtidal substrate present and although this habitat is not directly impacted by the project, there is the possibility that any significant alteration of water quality due to the release of suspended solids during dredging for example, may impact communities such hard corals that are present further afield; isolated hard corals have for example been recorded at Sha Chau (ERM, 1995) and further afield at Sham Tseng (Mouchel, 2001b). Although some hard and soft corals have been recorded on the hard subtidal substrates within the study area, they are mostly comprised of isolated colonies, have low percentage cover and many individuals are in poor condition as these waters probably represent the western most limit for many of the coral species present (Mouchel, 2001b, 2004). The influence of the Pearl River in the Northwest leads to a low salinity, sediment-laden water body that is known to inhibit coral growth and the absence of a well develop coral community is largely due to the prevailing estuarine waters present (Morton, 1994).
7.4.9.6
The littoral communities
present on the rocky and boulder shores in study area are mostly comprised of
common intertidal species that are found on these habitat types elsewhere in
7.4.9.7 An evaluation of the ecological quality of the benthic soft-bottom habitat and hard substrate habitat is presented below in Tables 7.6 and 7.7, respectively.
Table 7.6 Ecological Evaluation of Soft-bottom Benthic Habitat Within the Study Area
|
Criteria |
Soft-bottom
Benthic Habitat |
|
Naturalness |
Natural habitat (although note that this habitat is disturbed both
naturally and due to activities such as demersal trawling) |
|
Size |
Relatively large as majority of study area composed of soft-bottom
silt-clay material. Temporary loss of 360,000 m3 benthic habitat
predicted due to pipeline installation |
|
Diversity |
Infauna diversity is relatively low (H’ < 2) compared to other areas in Hong Kong due to the
proximity of the Pearl River Estuary and possibly due to the predominantly
silt-clay composition of the seabed that tends not to support high diversity
(Shin, 1998; Mouchel, 2001a, 2005a; CCPC, 2002) Epifauna (demersal fish, crustaceans and gastropods) diversity is
also low (H’ < 2; Mouchel,
2001a, 2005a) |
|
Rarity |
No rare species present |
|
Re-creatability |
Easily recreated as disturbed soft-bottom sediments readily
recolonised |
|
Fragmentation |
Highly connected to adjacent homogeneous habitat |
|
Ecological linkage |
Functionally linked to overlying water column |
|
Potential value |
Low |
|
Nursery/ breeding ground |
No species of conservation interest known to use soft-bottom
sediments in the study area as a nursery or breeding ground1 |
|
Age |
The majority of deposits are considered to be derived locally
although some are transported into the study area by the |
|
Abundance/ Richness of wildlife |
High number of macroinvertebrate infauna (67-81 families)2
and epifauna (113 species)2 present. Abundance is similar to the eastern waters
where 79 species of macroinvertebrate infauna have been recorded at |
|
Overall
Ecological value |
Low |
Notes: 1Horseshoe crab nursery areas are outside of the study area; 2Based on the most recent infauna and epifauna (trawl) data available from the study area collected in May and August 2001 and January and October 2005 (Mouchel, 2001a; 2002b; 2005a; Meinhardt, 2006d).
Table 7.7 Ecological Evaluation of Hard Substrate Benthic Habitat Within the Study Area
|
Criteria |
Hard
Substrate Benthic Habitat |
|
Naturalness |
Natural habitat |
|
Size |
Hard substrate intertidal habitats are not directly affected by this
project. There is, however, potential for indirect impacts related to
alterations in water quality. The only hard-substrates, relatively small in
area compared to soft bottom sediment, likely to be directly impacted are the
rocks and boulders occasionally found in the soft-bottom seabed. |
|
Diversity |
Low |
|
Rarity |
No rare species recorded although protected hard corals reported on
substrate at Sha Chau (and likely on other hard substrates in the study area
based on dive studies in Northwestern waters; Mouchel, 2001b, 2004) |
|
Re-creatability |
Readily re-creatable |
|
Fragmentation |
Naturally fragmented from adjacent homogeneous soft-bottom seabed |
|
Ecological linkage |
Connected to overlying water column and soft-bottom seabed |
|
Potential value |
Moderate given the potential for presence of some corals |
|
Nursery/ breeding ground |
No species of conservation interest known to use hard-substrates in
the study area as a nursery or breeding ground |
|
Age |
Hard substrate in study area largely composed of Jurassic/ Cretaceous
granitoids |
|
Abundance/ Richness of wildlife |
The only species of conservation interest present are isolated
colonies of hard corals many of which often appear in poor condition |
|
Overall
Ecological value |
Low |
7.5 Ecological Impact Assessment Methodology
7.5.1 The objective of the ecological assessment is to predict the direct, indirect, primary and secondary, on‑site and off‑site impacts of the PAFF. The significance of ecological impacts have been evaluated based on the criteria stipulated in Table 1, Annex 8 of the TM using the following criteria:
¨ habitat quality;
¨ species affected;
¨ size/ abundance of habitats affected;
¨ duration of impacts;
¨ reversibility of impacts; and
¨ magnitude of environmental changes.
7.5.2 Impacts are ranked as “minor”, “moderate” or “severe”, although in a few cases, “insignificant” (less than “minor”) or “extremely severe” may also 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 of “moderate” or “severe” are spelled out in the text as far as possible. As noted in Annex 16 of the TM, a degree of professional judgement is involved in the evaluation of impacts.
7.5.3 Impacts to species or groups assessed as ‘minor’ are predicted to cause a slight, and/or short term reduction in the local population numbers or geographic distribution of a species or group, but the species or groups are predicted to recover from the perturbation with no long-term adverse impacts. Habitat impacts are considered ‘minor’ when no species of conservation or regulatory concern are found, and when the habitat in question was widely distributed locally.
7.5.4 Impacts to species or groups assessed as ‘moderate’ are predicted to cause local reduction of species or group population numbers. The reductions would be long-term, and probably not recoverable, but the species or groups in question are considered widely distributed or common, and abundant on a local, regional, or global scale. Habitat impacts are judged ‘moderate’ when the habitat in question was of limited local or regional distribution or declining in extent, and when the potential for the habitat to support fauna and flora was considered of conservation or regulatory importance.
7.5.5 Impacts to species or groups are assessed as ‘severe’ when they are judged to adversely affect species or groups which are of conservation or regulatory concern locally, regionally, or globally due to scarcity or declining population or distribution trends. Impacts to habitats are considered ‘severe’ when the habitats are found to be limited or declining in geographic distribution, contain plant species of regulatory or conservation concern, or are generally considered by the scientific community to be of local, regional or global importance to the support of wild fauna.
7.5.6 If ecological impacts are found to be significant (i.e., minor to severe) mitigation needs to be carried out in accordance with the TM. Mitigation measures are not required for insignificant impacts. The policy for mitigating significant impacts on habitats and wildlife is to seek to achieve impact avoidance, impact minimisation and impact compensation in that order of priority. Impact avoidance typically consists of modifications to the project design, but may in extreme cases require abandonment of the project (the “no-go” alternative). Impact minimisation includes any means of reducing the scope or severity of a given impact, e.g., through timing of construction works, modification in design, or ecological restoration of disturbed areas following the completion of works. Impact compensation assumes that an irreversible impact will occur upon a given habitat or species and attempts to compensate for it elsewhere, for example, by enhancement or creation of suitable habitat. Compensation may take place on-site or off-site.
Cumulative Impacts
7.5.7 In order to assess the potential ecological impacts from other activities in the study area, cumulative impacts were also examined with respect to the pipe installation and berthing jetty construction. There are numerous other operations in the overall study area that could potentially lead to cumulative impacts and these include disposal of contaminated dredged material in the East Sha Chau CMPs and The Brothers MBA and neighbouring works that may result in cumulative ecological impacts. There is also the potential for impacts due to dredging of a new contaminated mud pit facility at Airport East or East of Sha Chau although it should be noted that this project is only tentatively scheduled for commencement in early 2008 and overlappling with the PAFF construction (due for completion in 2009) will be minimal. Impacts from marine pollution, fishing and shipping activity also require consideration. The cumulative impacts are, therefore, wider in scope than the potential impacts attributable to the aviation fuel facility.
7.6 Prediction and Evaluation of Construction Phase Impacts
7.6.1 Potential Ecological Impacts
7.6.1.1
Many of the ecological issues
also overlap with the sections of this EIA relating to water quality and risk
assessment. Consequently, many of the key ecological issues referred to in
previous sections are most likely to be influenced by water quality impacts.
The major activities likely to impact on the marine ecology of the study area
are anticipated to be predominantly related to the construction phase of the
project. Construction related impacts may arise from the installation of a
submarine pipeline which will require dredging and backfilling (estimated to
last for a duration of about 62 days for a grab dredger, based upon the most
recent volume of material to be dredged and the
need to restrict the dredging to 12 hours a day outside the
7.6.1.2 It should be noted that while percussive piling works, as were required for the jetty, have the potential to cause impacts to the Indo-Pacific Humpback dolphin, the piling works for PAFF have been completed under the previous Environmental Permit EP-139/2002/A. Details of the mitigation measures applied at that time are summarised in Section 7.8.2.
7.6.2
Alteration of Water Quality
7.6.2.1
The pipe installation and jetty
construction will lead to localised increase (patches) in suspended solid
concentrations in the water column. Suspended solids also contain organic
matter and consequently also have an oxygen demand. Elevated suspended solids,
therefore, have the potential to cause limited oxygen depletion of the water
column although it should be noted that no reduction in ambient dissolved
oxygen in Northwestern waters has been recorded even at high suspended solids
concentrations (100 mg l-1; Mouchel, 2001c). Suspended
solids can also smother the benthos when they settle-out. Impacts related to elevated suspended solids
are mostly observed in benthic sessile organisms that are unable to migrate
from the affected habitat. Increased suspended solids can clog the gills of
filter-feeding sessile organisms such as bivalves and fish leading to
suffocation. High suspended solids also
reduce incident solar radiation from reaching the benthos which can impair
photosynthesis. It should be noted,
however, that owing to seasonal inputs from the Pearl River, suspended solids
in the Northwestern region of
7.6.2.2 Reference to the water quality predictions for the Northwestern waters indicated that the potential for impacts from suspended solids concentrations on sensitive receivers (such as corals) were insignificant. Where predictions have indicated that suspended solid concentrations may prove unsuitable to sensitive receivers, appropriate mitigation measures were recommended for incorporation during the pipeline and berth construction.
7.6.3
Disturbance to the Benthic Habitat and Habitat Loss
7.6.3.1 There will be a temporary loss of sublittoral habitat and associated benthic communities resulting from the pipeline installation due to disturbance of the seabed. There is potential for localised resuspension of sediment particles due to the pipeline construction leading to impacts associated with suspended solids as described in the preceding section on alterations to water quality. The twin submarine pipelines are each about 500mm in diameter and will be placed in a trench in the seabed that is dredged using either a grab or trailer dredger.
7.6.3.2 It is likely that dredging will cause localised suspension of sediments in the vicinity of the area undergoing dredging activity. It should be noted that for much of its length the pipeline passes through soft-bottom sediment that is already subjected to dredging (for example, dredging activity associated with maintaining access channels to the existing AFRF at Sha Chau and Castle Peak Power Station) and intense trawling pressures (which also disturbs the seabed) and species present are either tolerant of these activities and/or have rapid recolonisation potential. Re-suspension of bottom sediments is unlikely to lead to elevated suspended solids further afield and only those fauna directly adjacent to the dredging activity are likely to be affected.
7.6.3.3 The benthic areas temporarily disturbed during pipeline installation will likely return to their pre-dredged state rapidly as uncontaminated sediments are colonised in Hong Kong rapidly (Meinhardt Mouchel, 2004; Meinhardt, 2006a). For example, recolonisation of defaunated sediment has been shown to be rapid and peaks in macroinvertebrate abundance are reached after only three months (Lu and Wu, 1998). Similarly, recolonisation of the clean material used to cap the exhausted borrow pits at East Sha Chau has also been shown to be rapid (Mouchel, 2001a). The survey data available for the study area showed that the macro-infaunal and epifaunal species composition is mostly comprised of filter-feeding and deposit-feeding representatives including polychaetes, molluscs, crustaceans and echinoderms and these representatives typically account for 95% of the benthic assemblage present (ERM, 1997) and are characteristic of soft-bottom benthic communities throughout Hong Kong (Shin and Thompson, 1982; Shin, 1989; CCPC, 2002). Both historical and recent data have indicated that no rare infaunal or epifaunal macroinvertebrate species are present in the study area.
7.6.3.4 The pipeline will be installed by dredging to a depth of approximately 2.2m below the existing seabed surface and placed within a submarine trench protected by rock armour, as shown in Figure 3.3. The total length of the pipeline is approximately 4.8km long and it is estimated that the total area of benthic habitat temporarily lost will amount to 124,975m2 and 340,000m3 but this is considered insignificant. As the pipeline is located below the seabed surface it will likely be backfilled by dredger using rock armour. Pipe installation will result in a temporary change in the composition of the habitat and also dislodge and smother the benthic fauna present. Furthermore, following completion of the installation operations, faunal colonisation will take place and a soft-bottom community should recolonise the material deposited on the rock armour and soft-bottom areas disturbed through construction activity should return to a pre-ploughed condition rapidly. Prolonged benthic habitat fragmentation is, therefore, highly unlikely. The ecological impacts, disturbance and temporary loss of benthic habitat during the construction phase are considered to represent an insignificant ecological impact to the soft-bottom benthos of the study area.
7.6.4.1
The Northwestern waters of Hong
Kong are strongly influenced by the
7.6.4.2
The faviid corals recorded
previously at Sha Chau (ERM, 1995) are approximately over 1.2km to the
southwest from the pipeline construction (at the nearest point). The isolated
hard corals present along the
7.6.4.3 Dredging is required for this project for twin submarine pipelines (each 20 inches in diameter) that will be placed in a trench in the seabed that is dredged through either grab or trailer dredger. As discussed in Section 6.4, the major water quality issues in the construction period are those associated with elevated suspended solids as a result of dredging and backfilling for the submarine fuel pipeline. For the impacts to sensitive receivers it was assumed that the pipeline trench could either be dredged mechanically using a barge mounted grab or hydraulically by means of a trailer suction hopper dredger. From the environmental perspective, the instantaneous sediment loss rates associated with grab dredging are likely to be less than that for trailer dredging. Thus, the intensity and extent of a sediment plume emanating downstream of a working dredge is likely to be less for a grab than a trailer and thus trailer suction dredgers are generally regarded as being more environmentally damaging than grab dredgers. The plume from a trailer dredger will, however, predominantly be formed at depth close to the drag head whereas grab-dredging plumes, though less concentrated, are likely to disperse throughout the water column as the grab is pulled to the surface. In order to determine whether water quality alterations with respect to suspended solids would have an impact on hard corals that are known to be relatively intolerant to deposited sediments (e.g., Brown and Howard, 1985; Rogers, 1990), water quality modelling was conducted as described in detail in Section 6 of this report.
7.6.4.4
Certain coral species appear
particularly susceptible to suspended solids through direct impacts such as
smothering and clogging of filter-feeding polyps and also indirect secondary
impacts such as reduction in light penetration leading to impaired
photosynthetic capacity of the symbiotic zooxanthellae (e.g.,
7.6.4.5
The water quality modelling (based
on suspensions of sediment attributable to worst-case trailer suction hopper
dredging) described in Section 6 predicted that the elevations in suspended
solids would be highly localised and mostly confined to the bed layer and well
within the range of natural variability for Northwestern waters and hence do
not represent any ecological concern. The model also predicted that there would
not be any substantial accumulation of re-deposited sediments likely to
adversely affect either benthic organisms or particularly susceptible species
such as hard corals (see Section 6). No locations beyond the immediate vicinity
of the worked area would experience settlement rates greater than 200 g m-2
day-1 that represents a value that has been used by previous
workers as an indicator level above which sustained deposition could harm
sediment-sensitive hermatypic corals (
7.6.4.6 In summary, sedimentation impacts on hard corals are well documented and toxicity and mortality are dependent on whether the deposited material is toxic (sediments in the study area are considered to be comparatively non-contaminated see Section 6), the duration of smothering (likely to be of short duration owing to the rapid currents present in part of the study area such as along the Urmston Road) and the species of coral present as platelike forms appear more sensitive although they have not been recorded in the study area. Sea pens such as Pteroides esperi are widespread throughout the soft-bottom seabed of study area and were previously recorded by ERM (1996) and Mouchel (2001a; 2001b; 2005b). The soft gorgonian coral Ellisella gracilis has also been recorded from the northeast of Sha Chau (ERM, 1996). These soft corals are not particularly susceptible to high suspended solid loadings as they do not possess symbiotic zooxanthellae. Gorgonians are typically branching corals that are probably less susceptible than other forms to sedimentation (Brown and Howard, 1985) and it is unlikely that localised suspension of the seabed through dredging will have an impact on corals such as Ellisella gracilis. There are also records of protected stony corals (faviids) from near Sha Chau (ERM, 1995) although they are distant (approximately 1.2km to the southwest) and in any case suspended solids settlement rates greater than 200 g m-2 day-1 that represents a value above which sustained deposition could harm sediment-sensitive hermatypic corals (Rogers, 1990) are not predicted. Construction-phase impacts to hard and soft corals are, therefore, considered to be insignificant.
7.6.5 Disturbance to Indo-Pacific Humpback Dolphins
Background
7.6.5.1
There is increasing pressure
being placed on the Northwestern waters due to numerous infrastructural
developments in this location. As the
area also holds the majority of
Noise
7.6.5.2
Cetaceans use two functional
classes of sound, these are echolocation and communication. Echolocation is
used for orientation, navigation, prey detection and learning about the
surrounding environment, whilst communication is used for intraspecies
signalling (
7.6.5.3 High levels of noise potentially will be emitted from construction work activity such as crane barges. Research has indicated that dolphins have acute hearing above 500 Hz and echolocate and communicate well into ultrasound above 20 kHz (Wursig et al., 2000). Owing to the propagation of sound in water, frequencies below 10 kHz tend to travel longer distances than those reaching into ultrasound and consequently these lower frequencies can be more disruptive to cetaceans (Wursig et al., 2000). Activities such as pile driving have their highest energy at lower frequencies from about 20 Hz to 1 kHz and whilst smaller cetaceans (~ 3-4 m) are not known to be highly sensitive to sounds below 1 kHz they can hear in much of this range and sounds in their vicinity could induce changes in behaviour, interfere with communication and even cause physiological and morphological damage (Greene and Moore, 1995; Wursig et al., 2000).
7.6.5.4 A piled jetty is required for creation of the PAFF berthing facility at Tuen Mun. Piled structures are preferable to blockwork or closed structure designs as they have less impacts to marine ecology, including dolphins, owing to a smaller footprint, and colonisation of piles being more rapid than with blockwork structures. Piled structures also have less marine ecological impacts, as invertebrates and fish assemblages are attracted to these structures, which may also attract dolphins (Wursig, 1995b). It should be noted, however, that the piled foundation has been already constructed (see Section 1) and no further piling is required. The piling was undertaken in accordance with the previous EP-139/2002/A and the mitigation measures applied at that time to avoid impacts to the Indo-Pacific Humpback dolphin are summarised in Section 7.8 for information.
Dredging and Impacts from Suspended Solids
7.6.5.5
There is no reason to assume
that suspended solid releases during pipeline construction will have an impact
on dolphins. Indo-Pacific humpback dolphins are naturally exposed to high
levels of suspended solids in the Pearl River Estuary; the sediments to be
dredged in the study area are generally not contaminated, and water quality
modelling has predicted that suspended solid elevations during pipeline
construction are highly localised (Section 6). Release of suspended solids to
the water column are not predicted to have any impact on dolphins (Section
6). There is also some evidence to
suggest that dredging activities attract dolphins, regardless of ambient
suspended solid concentrations (Hyder, 1998; Jefferson pers. comm.). It is
probable that dredging disturbs invertebrates inhabiting the sediment which
provides feeding opportunities for fish and subsequently dolphins. There appears
to be no documented evidence to suggest dredging has adverse impacts on
dolphins although potential disturbance impacts should be carefully considered
when dredging in areas that are important to the dolphin population (
7.6.6
Sha Chau and
7.6.6.1
The study area associated with
the pipeline is located within the Sha Chau and
7.6.6.2
Construction phase impacts
described in the sections on impacts to the benthos and corals detailed above,
are also applicable to the Sha Chau and
7.6.6.3
The species-based ecological
impact assessment to the Indo-Pacific Humpback dolphin should be consulted as
the predicted impacts also apply to individuals inhabiting the Marine Park
although it should be noted that the majority of individuals within the Marine
Park are found to the north at Lung Kwu Chau (Jefferson, 2000a, 2005; ERM, 2006
also refer to Figures 7.2a and 7.2b for relative density of Indo-Pacific
Humpback dolphin). There will be a temporary (unavoidable) loss of a small
amount (400m long) of benthic habitat in the Marine Park due to pipeline
construction which may affect the feeding opportunities of fish and dolphins
(although it should be noted that dislodged infauna are in fact likely to
attract fish and prove beneficial to dolphins). As described above, the
temporary loss of benthic habitat is considered insignificant owing to the
likelihood of rapid recolonisation by benthic fauna once the trench supporting
the pipeline has been covered in sand and sediments. In addition, the dredging
of the access channel for the AFRF that is required to maintain the facility
for emergency backup will disturb the seabed in this area approximately once
every 3-4 years and no ecological impacts are evident in the
Artificial Reefs
7.6.6.4
Artificial Reefs (ARs) were
placed in the Sha Chau and
7.6.6.5
The proposed pipeline from the
PAFF to Sha Chau is distant to the ARs (approximately 1 km away at the nearest
point) and suspended solids lost to the water column during construction of the
pipeline are not expected to have any water quality impacts on the ARs (see
Section 6). It is interesting to note that the ARs and fishing exclusion zone
in-place near the airport are close to the East of Sha Chau contaminated mud
disposal facility. Effects from contaminated mud disposal (and other activities
such as major dredging and maintenance capping that is required for the backfilled
pits) would have a higher impact than the localised suspension of
uncontaminated seabed sediments predicted by the water quality modelling
described earlier in Section 6 for the PAFF pipeline construction. The area
close to the airport nevertheless has been found to contain abundant fisheries
resources that are probably related to the ARs (Mouchel, 2001a; Meinhadt,
2006a) aggregating fisheries resources in the area. The proposed pipeline
construction is not, therefore, considered likely to have an ecological impact
on the ARs located within the Sha Chau and
7.6.7
Cumulative Ecological Impacts (Marine Ecology and Indo-Pacific
Humpback dolphin)
Marine Ecology
7.6.7.1
Marine systems are exposed to a
wide range of impacts although, to date, few studies in
7.6.7.2 Whilst it is acknowledged that activities from the current project may slightly increase the pressure on ecological resources due to concurrent dredging and backfilling at the ESC CMPs and North of the Brothers MBA, together with other developments in the area, the predicted impacts from this study are predominantly confined to the construction phase and of short duration, with pipeline dredging anticipated to take a maximum of about 62 days depending upon the dredging technique applied and the ultimate amount of material to be dredged. No operational phase maintenance dredging is required. The activities described above that are concurrent to the PAFF construction phase which may cause cumulative impacts to the marine ecology of the study area may result in the following (ERM, 1997):
¨ a prolonged period of impact;
¨ an increased intensity of the impact; and
¨ induced synergistic impacts (i.e., effects that are greater in combination than singularly).
7.6.7.3 It is anticipated that the ecological impacts due to the pipe laying and PAFF construction are associated with the potential for suspension of sediments and alteration to dissolved oxygen. Section 6 of this EIA on Water Quality has concluded that no sensitive receivers are predicted to be impacted. As the predicted impacts are predominantly confined to the construction phase and hence are short-term, project-specific impacts are not expected to result in unacceptable impacts to water quality and hence unacceptable marine ecological cumulative impacts are similarly not anticipated.
Indo-Pacific Humpback Dolphin
7.6.7.4 There could be potential for cumulative impacts to the Indo-Pacific Humpback dolphin in the study area due to unmitigated noise from construction activities and ambient industrial sources such as Shekou, coupled to the aggregated pressures from fishing, shipping, mud disposal at the CMP’s and pollution arising from numerous sources both in Hong Kong and Southern China. However, as the piling works have been completed under the EP-139/2002/A and further piling is not required, the PAFF is unlikely to increase the duration of the aforementioned pressures and is not likely to increase the intensity of impact and synergistic impacts are not predicted. As such, no significant adverse cumulative marine ecological impacts due to the PAFF construction are envisaged.
Cumulative Impacts to the
7.6.7.5
Previous studies that have
evaluated the potential impacts from contaminated mud disposal at the empty
marine borrow pits at East Sha Chau (ERM, 1997) and sand dredging around The
Brothers (Hyder Consultants, 1998) have concluded that there is likely to be no
cumulative impacts to the Sha Chau and
7.7
Prediction and Evaluation of Operational Phase Impacts
7.7.1.1
As discussed in Section 7.6 above, the majority of potential
ecological impacts are associated with the construction phase. During operation
of the PAFF there is potential for ecological impacts
due to an accidental fuel spillage or leakage from a ruptured pipe. The major
ecological risks associated with fuel spills are discussed in Section 11.
7.7.2
Disturbance to the Benthic Habitat
7.7.2.1 No disturbance of the seabed due to the operation of the PAFF is anticipated as maintenance dredging will not be required for the PAFF project. There will, therefore, be no operational impacts to benthic fauna and corals as a result of the operation of the project.
7.7.3 Disturbance to Indo-Pacific Humpback Dolphin
7.7.3.1 The major potential operational impacts to the dolphin are associated with potentially elevated submarine noise due to vessel movement and berthing, the potential for physical impacts with vessels and cumulative effects attributable to this and other projects in the PAFF study area.
Noise
7.7.3.2 Cetaceans are known to be sensitive to elevated noise and generally avoid areas subjected to high levels of noise disturbance. Noise generated through the operation of the fuel transporting vessels (such as through pumping of fuel) is the major sources of operational phase sounds.
7.7.3.3
The primary sources of sounds
from vessels are due to the boat propeller and related machinery (Greene and
Moore, 1995). Larger vessels create stronger and lower frequency sounds as they
have greater power than smaller vessels and also have slower turning engines
and propellers (Greene and Moore, 1995). Noise from smaller boat traffic has
led to changes in the acoustic behaviour of Indo-Pacific Humpback dolphin
populations in
7.7.3.4 The lower frequency sounds (< 250 Hz) emitted from larger vessels, however, although still detectable by dolphins, have less of an impact than high frequency sound (ERM, 1995; Wursig et al., 2000) and based upon this the PAFF tankers are not predicted to induce considerable disturbance above that already caused by the high volume of vessel traffic in the area. Anecdotal evidence suggests that the dolphins avoided the area around The Brothers during the airport construction (although this was a considerably larger project than the PAFF) however they returned on cessation of construction activities suggesting that disturbance impacts are transient and only present during the construction phase (Hyder, 1998). Further evidence for noise-induced avoidance was observed immediately after the AFRF construction. Immediately following construction of the AFRF, dolphin numbers declined in the area (recorded during the period of Spring 1997) although further surveys (Summer and Autumn 1997; and more recent survey work) revealed that there was an influx of individuals back into the area (Jefferson, 2000a, 2000b, 2005) indicating that temporary avoidance of areas due to noise does not have a long-term detrimental effect on the population.
7.7.3.5 It should be noted that the waters adjacent to the PAFF are used by
a large number of vessels and a busy shipping channel (
7.7.3.6 The sounds emitted from the largest ocean-going vessels (supertankers) are lower (~ 170 dB) than those from strong transient sources such as percussive piling (Greene and Moore, 1995; Wursig et al., 2000). Owing to the transient nature of the fuel vessels visiting the PAFF (initially about three vessels will visit and later less than four per week are predicted during the maximum operation in 2040), the overall reduction in fuel vessel traffic in the study area and the current high utilisation of these waters by dolphin populations, the potential for habituation to vessel traffic appears noise to be strong. The operational noise from the fuel vessels is, therefore, likely to represent an insignificant impact to Indo-Pacific Humpback dolphins.
Collisions with Fuel Vessels
7.7.3.7
There is evidence in
7.7.3.8 The study area is presently utilised by a large volume of marine traffic (mostly comprised of cargo vessels, tugs, barges and fishing vessels; Jefferson, 2000b) and a relatively small number of strandings appear to be due to direct boat collisions (three dolphin carcasses were recorded in Hong Kong with wounds consistent with injuries attributable to vessel collisions between May 1993 and March 1998; Parsons and Jefferson, 2000a). Although only three carcasses were recorded during this period with physical injuries consistent with vessel collision, the small number is likely to be an underestimate of deaths due to collisions as the cause of death is often difficult to ascertain due to decomposition of the carcass. The vessels used for transporting the fuel are, however, large (10,000-80,000 dwt) and relatively slow compared to the motorboats used by fishermen and the high-speed ferries operating in the area (also note that fuel vessels will unlikely to operate at full speed when traversing the area and during the berthing at the PAFF jetty). The fuel-transporting ships that will berth at the PAFF have a greater capacity than those currently berthing at the AFRF. These larger fuel vessels will also only need to berth at the PAFF at a frequency of three per week compared to the current more frequent visits required at the AFRF (where fuel transporting vessels currently berth about 14 times per week). Even during maximum operation, it is also only anticipated that a small number of vessels will visit the PAFF and operational impacts due to physical impact with fuel-carrying vessels are, therefore, extremely unlikely (three visits per week are initially required and an average of 3.6 vessels per week are predicted during maximum operation in 2040, Table 3.2). There is, therefore, an overall reduction in the number of vessels in the study area and the potential for collision with the fuel vessels is predicted to represent an insignificant impact.
7.8.1.1 As presented in Annex 16 of the TM, mitigation measures for projects in important habitat and relating to wildlife in order of priority are:
¨ avoidance;
¨ minimising; and
¨ compensation.
7.8.1.2 The preferred location for construction of the PAFF and pipeline options has been assessed previously (see Section 2) and the proposed scheme selected in order to avoid the key ecological receivers present and important habitats, primarily the key ecological receivers present in the study area including the Indo-Pacific Humpback dolphin.
7.8.1.3
No
adverse changes in water quality have been predicted. As detailed in Section
6.4.6, based on trailer suction hopper dredging (this represents the worst case
and covers the use of the grab dredger), suspended solids in the upper surface
layer rarely exceed 5
mg l-1 throughout the whole study area. Although a short-lived patch of 10 mg l-1 was predicted in waters to the east
of Lung Kwu Chau and this concentration is well below the ambient background
levels occasionally recorded in the study area (often > 100
mg l-1; Mouchel,
2001a; 2001c). The highest sediment concentrations suspended during dredging
are predicted in the bottom layers. It should be noted that the patches
generated by the trailer dredger are predicted to be highly localised generally
below 10mg l-1 within
a few hundred meters of the dredging point. These sediment patches generated in
the deeper waters are predicted to be generally quickly dissipated (such as by
the fast currents of the
7.8.1.4
The mitigation measures
designed to prevent adverse impacts to water quality (for example, using dredging operations that minimise sediment suspension)
will also be effective in preventing impacts to the marine ecological
receivers. It is, therefore, anticipated that no specific mitigation measures
to protect marine ecological receivers (with the exception of Indo-Pacific
Humpback dolphin) are required. Owing to the sensitive nature of project near
the Sha Chau and
7.8.1.5 As cetaceans are affected by noise, certain project-specific mitigation measures relating to noise mitigation have been recommended for the protection of the dolphin population inhabiting the area. These recommended mitigation measures are described below.
7.8.2
Indo-Pacific Humpback Dolphin
7.8.2.1 There was intensive monitoring of the noise emissions from the hammer used in the piling at the AFRF (Wursig et al., 2000) and these data can be used to provide suitable information for comparison of the magnitude of likely impacts in the proposed PAFF. As the hammer used in the piling of PAFF jetty is similar and likely to emit similar noises, impacts to dolphins would be considered to be of a similar magnitude.
7.8.2.2 Unmitigated construction-phase percussive piling was considered to represent a moderate to severe but transient (estimated to last a duration of about 120 days) impact to dolphin populations in the vicinity (within 500m) of the PAFF jetty construction works and minor impacts may be induced further afield (up to a 1000 m from the piling at which distance piling noise cannot be differentiated with confidence from background; Wursig et al., 2000).
7.8.2.3 However, it should be noted, that as detailed in Section 1, some construction works have been undertaken in accordance with Environmental Permit EP-139/2002/A and before works were suspended following the Judgement of the Court of Final Appeal of July 2006. As detailed in Table 1.1, the percussive piling for the jetty was one of the activities that has been completed. The EP required that numerous mitigation measures be undertaken before, during and after the marine piling was undertaken. The following measures were undertaken in accordance with the EP:
¨ Bubble Jacket and Bubble Jacket Trail: In order to mitigate the submarine noise from the percussive piling, a piling system based on a sequestered air-stream bubble jacket or similar, as presented in Figure 7.4, was recommended in the previous EIA (April 2002) to counter the problem of bubble dispersion as the air stream and ensure the bubbles are enclosed by an outer jacket thereby concentrating the bubbles vertically up the pile. Condition 3.2 of the previous EP-139/2002/A stated that a trial of the bubble jacket should also be carried out to demonstrate a noise attenuation effect of 3dB and achieve the following underwater mitigated noise levels:
Distance from Piling (m) dB goal
250 162
500 152
1000 145
Based upon this requirement, a trail of the bubble jacket was
undertaken in March 2004 and a Bubble Jacket Trial Summary Report issued in
January 2005. A copy of the report is provided in Appendix F1. The 3 day trial considered two general
designs of the bubble jacket, termed the Canadian Bubble Jacket and the Fixed
Steel Bubble Jacket with variations of these designs creating 7 options for
assessment overall. The results showed
that Option 7, a Fixed Steel Bubble Jacket combined with the lowest ring of the
Canadian bubble jacket mitigated the noise sufficiently within the
¨ Dolphin Exclusion Zone Around the Piling Barge: this was implemented within a radius of 500m around the piling barge during piling activities and the area visually inspected for dolphins for a period of 30 minutes (thereby adequately spanning the approximate maximum dive time of the dolphins of 4 minutes) prior to commencement of each piling episode.
¨ Acoustic Monitoring: Spot acoustic monitoring of the exclusion zone was undertaken for three days of the first week of piling in order to confirm that dolphins were not being missed by the visual monitoring.
¨ Noise Monitoring During Piling: This was undertaken in order to confirm the underwater noise levels indicated above were achieved. Measurements were taken at three testing locations from the pile driver, namely 250, 500 and 1000m meter intervals west of the pile driver and recordings taken over the initial three days of the first week of piling.
¨
Seasonality of Piling: The piling avoided April to June to avoid the highest frequency of
calving.
¨
Acoustic Decoupling: Air compressors and other noisy equipment mounted on the steel
piling barge was acoustically-decoupled to the greatest extent feasible.
¨ “Ramping-up” of Piling Hammer: The piling hammer was “ramped–up” to gradually increase the noise levels after the 30 minute visual inspection had been completed. The "ramp-up" period lasted about 2-3 minutes, to allow dolphins to move a safe distance from the area.
¨
Dolphin Data Review: It was recommended that a
review of longer term data would be needed as the construction period would be
going on several years after the initial review and the distribution of dolphins
and densities may change over time. Therefore, prior to the commencement of construction
works a review of all new available dolphin data for
¨ Dolphin Monitoring: In order to ensure that any shifts in dolphin distribution due to piling are detected and to determine the efficacy of the recommended mitigation measures, six one-day pre-construction monitoring surveys of dolphin abundance were undertaken in late 2005 and the results are provided in Appendix F3. The results will be compared with the post-construction dolphin abundance monitoring, due to be undertaken for 6 days during a period of 28 days prior to the operation of the PAFF. The methodology used for the pre-construction dolphin abundance monitoring is the same as that recommended for the post-construction surveys detailed in Section 7.8.2.8 below.
7.8.2.4 However, while the piling activities have been completed, the dredging for the pipeline will need to be undertaken and as such the following mitigation measures are recommended.
Dolphin Exclusion Zone: Around the Dredger
7.8.2.5
There does not appear to be any
evidence to suggest that dredging activity has any deleterious impact to
dolphins. No unacceptable adverse impacts are predicted to dolphin populations
as a consequence of pipeline construction and as such no mitigation is
required. Nevertheless, several precautionary measures detailed in this section
and the sections below are recommended to further minimise any possible
impacts. Such measures include the use
of an exclusion zone around the dredging operation within the
7.8.2.6
In addition, as such a measure
relies on the visual detection of dolphins, it is not suitable during evening
and nighttime. Based upon this, dredging works will
be restricted to a daily maximum of 12 hours within daylight hours except for
the section crossing Urmston Road Channel.
The
Avoidance of Calving Season
7.8.2.7 According to recent dolphin data (AFCD, 2005) the dolphin calving season is from March to August and about 76% of calves are born in this period. Thus, in order to minimise disturbance to mother and calves, it is recommended that the dredging along the entire length of the pipeline will avoid this main calving season.
Dolphin Monitoring
7.8.2.8 In order to ensure that any shifts in dolphin distribution due to piling are detected and to determine the efficacy of the recommended mitigation measures, post construction monitoring of dolphin abundance is required for comparison with the pre-construction monitoring undertaken prior to the piling works in late 2005 as detailed above. Should dolphin sighting numbers be significantly different (taking into account naturally occurring alterations to distribution patterns such as due to seasonal change) to the pre-construction activity (following the post-construction monitoring) recommendations for a further post-construction monitoring survey will be made. Data should then be re-assessed and the need for any further monitoring established. Comparison of the post construction dolphin monitoring with that of over the pre-construction dolphin monitoring will allow the assessment of the overall efficacy of the project-specific mitigation measures and an Action Plan for the dolphin is included in the EM&A Manual and Appendix F4 of this report.
7.8.2.9
A monitoring programme is
required to be undertaken during both a 28 day period prior to construction
activities and during a period of 28 days on cessation of construction. The
period required for the post-construction monitoring is based on the monitoring
conducted for the AFRF and is considered to be adequate to derive a reasonably
large amount of data thereby allowing any significant trends in dolphin
distribution to be detected (
7.8.2.10 The monitoring should also be undertaken by a suitably qualified
person (in biology) and should be independent of the construction contractor
and should form part of the independent Environmental Team (ET). The IEC may audit the work of the ET if
deemed necessary. Monitoring will be conducted following the
methodology detailed below.
Vessel-based Observations
7.8.2.11 Line transect surveying techniques have now been standardised in Hong Kong Special Administrative Region Waters so that data from all surveys are directly comparable. The study area with line transects is presented in Figure 7.3a. In order to provide a suitable long-term dataset for comparison, post construction phase dolphin monitoring will employ an identical methodology and follow the same line transects as those presented in Figure 7.3a.
7.8.2.12 On each survey day, the survey vessel will depart from Tung Chung New Pier. Observation for incidental sighting will begin immediately on departure from the assigned pier and continue until the vessel reaches the survey area. The survey vessel shall have an open upper deck, allowing for observer eye heights of 4 to 5m above water level and relatively unobstructed forward visibility between 270° and 90°. When on-effort, the vessel shall travel along the survey lines at a speed of approximately 7 to 8 knots (13 to 15 km/hr). The direction of the survey shall be alternated on different days to avoid possible biases related to the timing of the survey coverage.
7.8.2.13 Vessel-based transect observations by a three-person team shall be conducted by searching the 180° swath in front of the survey vessel (270° to 90°). The area behind the vessel need not be searched, although dolphins observed in this area should be recorded as off-effort sightings. The primary observer will scan the entire search path (270° to 90°) continuously with Fujinon 7X50 marine binoculars or equivalent as the second member of the team, designated the data “recorder”, scans the same area with the naked eye and occasional binocular check. The third observer on the boat is required to rotate into the observation team after half an hour, thus relieving one of the initial team. Observers should rotate every half an hour. While on-effort, observers shall ignore potential sighting cues that could bias the sighting distance calibration (eg pair-trawl fishing vessels).
7.8.2.14 A critical consideration in the survey will be to ensure a strict timed quantification of “sighting effort” in order to maximise the comparative value of the field survey results. The time and position for the start and end of a period of intensive, uninterrupted effort, and the sighting conditions such as visibility range and Beaufort scale associated with it shall be recorded. The collection of effort data allows comparisons within a single study as well as between studies. Strict recording of time and speed travelling along the assigned transect (“on-effort”) shall, therefore, be recorded. Time spent during any deviation from the transect will be recorded as “off-effort”.
7.8.2.15 During periods of poor weather, when visibility is hindered (e.g., below 1km) or when a Beaufort force 5 is reached, the survey should normally be postponed.
7.8.2.16 Sightings distant to 500m perpendicular distance and sightings of single dolphins that were hard to track should not be pursued (although those distant to 500m ahead of the vessel should be pursued). The initial sighting distance between the dolphin and the survey vessel and sighting angle shall be recorded in order to estimate the positions of the dolphins. These and other details of the sighting, including the exact location of the sighting and number of individuals should be agreed among the observation team and recorded immediately. Distances and angles shall be as accurate as possible.
7.8.2.17 A global positioning system shall be used during the surveys. A sighting record shall be filled out at the initial sighting with time, position, distance and angle data filled in immediately and verified between primary observer and recorder. All other information on sea state, weather conditions (Beaufort Scale), as well as notes on dolphin appearance, behaviour, and any other information shall also be completed.
7.8.2.18 An action plan has also been defined to indicate that should dolphin numbers be significantly different (taking into account naturally occurring alterations to distribution patterns such as due to seasonal change) to the pre-construction activity following the 28 days post-construction monitoring, recommendations for a further 6 days monitoring within a 28 day period will be required. The action plan should be undertaken within a period of 1 month after a significant difference has been determined. For the purpose of the EM&A works, the “significance” level which will trigger the action plan shall be proposed by the ET as part of the post-construction monitoring programme design to be agreed with AFCD prior to the monitoring being undertaken. The action plan is detailed in Appendix F4 of this report and in the EM&A Manual.
7.8.2.19 It should be noted that as some construction activities commenced in November 2005, before the Judgement of the Court of Final Appeal of July 2006, the pre-construction abundance monitoring was undertaken in late 2005 and the results are provided in Appendix F3. As such, the post-construction dolphin abundance monitoring will be required to be undertaken for during a period of 28 days prior to the operation of the PAFF.
7.9
Conclusions and Recommendations
7.9.1 Providing good on-site working practice and the recommended mitigation measures are adhered to, significant ecological impacts are not anticipated from either the construction or operational phase of the PAFF project. The major sensitive ecological receiver of concern in the study area is the Indo-Pacific Humpback dolphin. Noise from percussive piling for the jetty at Tuen Mun Area 38 was determined to be the major potential impact to this species and the mitigation measures recommended in the previous EIA (April 2002) and the EP-139/2002/A were followed during the piling activities, which are now complete. Further precautionary mitigation measures are also detailed above and based upon the implementation of these, insignificant impacts are predicted.
7.10
Residual Ecological Impacts
7.10.1
Provided
that the mitigation measures recommended above are implemented, there are no
adverse residual ecological impacts predicted for either the construction or
operational phases of the project.
7.11 Environmental Monitoring and Audit Requirements
7.11.1
The post construction monitoring will prove valuable
in assessing the overall efficacy of the project-specific mitigation measures
implemented. The monitoring shall be undertaken in accordance with the
methodology detailed above. An action
plan has also been defined to indicate that should dolphin numbers be
significantly different (taking into account naturally occurring alterations to
distribution patterns such as due to seasonal change) to the pre-construction
activity following the 6 days of post-construction monitoring, recommendations
for a further period of monitoring will be required. This action plan is
detailed in the EM&A Manual and also presented in Appendix F4 of this
report.
7.11.2
It should be noted that as some construction
activities commenced in November 2005, before the Judgement of the Court of
Final Appeal of July 2006, the pre-construction abundance monitoring was
undertaken in late 2005 and the results are provided in Appendix F3. As such,
the post-construction dolphin abundance monitoring will be required to be
undertaken for 6 days during a period of 28 days on cessation of construction.
7.11.3
As no other significant impacts on other marine
fauna is predicted, no further EM&A is considered to be required during
either the construction or operational phases of this project. EM&A
requirements during the construction phase are described in more detail in
Section 15 of this report and in the EM&A Manual.
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