This section presents an
assessment of potential impacts to fisheries associated with the construction
and operation of 132kV supply circuit from the existing Pui O Substation on
south Lantau Island via Chi Ma Wan Peninsula via Adamasta Channel towards
Cheung Chau North and Cheung Chau South Substation. Potential sources of impact
associated with the construction and operation have been identified and
assessed. The Study Area is confined to the proposed submarine cable across the
Adamasta Channel and formation of a small-scale reclamation temporary works
area (180m2)
works at Pui O Wan. Preliminary
requirements for mitigation and monitoring are recommended where
appropriate. The assessment focuses on
an identification and evaluation of impacts to fisheries resources, fishing
operations and culture fisheries.
The objectives of the assessment are as follows:
· to establish the importance of the habitats and fishing activity potentially affected by the construction and operation of the proposed project;
·
to identify fisheries
sensitive receiversparameters and the area that will be affected;
· to assess the scale of possible impacts to fisheries arising from the construction and operation of the proposed works;
· to highlight any insurmountable impacts to fisheries;
· to identify any mitigation measures and residual impacts; and
· to assess the need for a fishery monitoring and audit programme.
The criteria for evaluating fisheries impacts are laid out in the Technical Memorandum on Environmental Impact Assessment Process (EIA-TM) of the Environmental Impact Assessment Ordinance (EIAO) (Cap 499). Annex 17 sets out the general approach and methodology for assessment of fisheries impacts. Annex 9 recommends some criteria that can be used for evaluating fisheries impacts. This assessment allows a complete and objective identification, prediction and evaluation of the potential fisheries impacts.
Other legislation that applies to fisheries includes:
· Fisheries Protection Ordinance (Cap 171) 1987 which provides for the conservation of fish and other aquatic life and regulates fishing practices; and
· Marine Fish Culture Ordinance (Cap 353) 1983 which regulates and protects marine fish culture and other related issues.
In Hong Kong, the commercial marine fishing industry is divided into capture and culture fisheries. To assess the capture fisheries within the Study Area, the most up-to-date literature “Port Survey 1996-1997” by the Agriculture, Fisheries and Culture Department (AFCD) was reviewed. A consultancy study on “Fisheries Resources and Fishing Operations in Hong Kong Waters (1998)” (FRFO) has also been reviewed to determine the important areas for nursery and spawning grounds within the Study Area. Mariculture fisheries information was obtained from the AFCD Annual Report 1998/99.
Although the proposed construction works may not lead to any loss of fishing grounds or nursery areas, the potential impacts to water quality upon the commercial fishing grounds and nursery areas within the Study Area are discussed.
In 1998, the estimated
fisheries production in Hong Kong Waters from both capture and culture
fisheries amounted to 186,100 tonnes, valued at HK$ 2,268 million1 the capture
fishery produced about 181,000 tonnes with about 90% of the catch coming from
outside Hong Kong waters1. Capture fisheries accounted for 97 % by
weight of the total production. The
remaining 3 % corresponded to the culture sectors of the industry. Within Hong Kong Waters, the highest yields
for local fisheries were mainly derived from the eastern and northeastern
coasts2.
Fishing Operations
The proposed construction area is
within AFCD fishery area zones, Tai Long Wan (0009), Pui O (0010) and Cheung
Chau (0030). The waters of these three
zones are referred to as the Construction Area. A small-scale reclamation temporary works area in
shallow water (approximately 180 m2) is located at Pui O Wan east
corner whereas the proposed submarine cable will be laid from Tai Long Wan East
to Cheung Chau via the Adamasta Channel crossing the Tai Long Wan and Cheung
Chau fishing zone. The fishing operations and fisheries resources within the
adjacent fishery areas (Chi Ma Wan, 0008; Cheung Sha, 0011; Shek Kwu Chau,
0031) will also be potentially affected and are also discussed. These three zones, combined with the three
zones of the Construction Area, make up the Study Area (Figure 5.1).
On the basis of their ranking (Table 5-1), the fishing zones of the Study Area are of varied importance (from low to medium-high) to the Hong Kong fishing industry. The fishing zones of low ranking include Pui O (0010), Cheung Sha (0011) and Shek Kwu Chau (0031), whereas the fishing zones of medium-high ranking include Tai Long Wan (0009), Cheung Chau (0030) and Chi Ma Wan (0008).
The proposed dredging/small-scale reclamationmarine works willcould potentially affect three
fishing zones: Tai Long Wan (0009), Pui O (0010) and Cheung Chau (0030). Tai
Long Wan and Cheung Chau are ranked medium-high whereas Pui O is ranked low to
the Hong Kong fishing industry. The small
reclaimed area at Pui O Wan east corner will cover only 0.018 hectares which
constitutes less than 1% of the total area (596.51 ha) and provides a
production value of only HK$ 31. The
impacts are likely to be negligible.
Table 5-1 Total
Value (HK$), Adult Catch (kg) and Fry Catch (tails) Displayed on a Total
Production, Production per Hectare and Rank (per Hectare) Basis for the Fishing
Zones in the Study Area (All Fishing Vessels)
|
Fishing Area And AFD Code |
Total Production |
Production (ha-1) |
Rank (Production ha-1) |
||||||
|
Adult Fish (kg) |
Value (HK$) |
Fry (tails) |
Adult Fish (kg) |
Value (HK$) |
Fry (tails) |
Adult Fish (kg) |
Value (HK$) |
Fry (tails) |
|
|
Construction Area |
|
|
|
|
|
|
|
||
|
0009 Tai Long Wan |
53,587 |
1,433,905 |
- |
140 |
3,753 |
- |
72 |
67 |
- |
|
0010 Pui O |
57,973 |
1,632,745 |
7,661 |
77 |
1,712 |
7 |
107 |
116 |
82 |
|
0030 Cheung Chau |
834,581 |
16,740,978 |
- |
241 |
4,835 |
- |
36 |
57 |
- |
|
Other Fishing
Areas |
|
|
|
|
|
|
|||
|
0008 Chi Ma Wan |
76,184 |
2,158,632 |
- |
122 |
3,458 |
- |
81 |
78 |
- |
|
0011 Cheung Sha |
78,347 |
1,749,819 |
7,661 |
76 |
1,712 |
7 |
107 |
116 |
82 |
|
0031 Shek Kwu Chau |
216,916 |
5,726,170 |
- |
64 |
1,689 |
- |
118 |
117 |
- |
(Source: Adopted from Port Survey 96/97, AFCD.)
The proposed
dredging/small-scale reclamation works will affect three fishing zones: Tai
Long Wan (0009), Pui O (0010) and Cheung Chau (0030). Tai Long Wan and Cheung
Chau are ranked medium-high whereas Pui O is ranked low to the Hong Kong
fishing industry. The small reclaimed area at Pui O Wan east corner will cover
only 0.018 hectares which constitutes less than 1% of the total area (596.51
ha) and provides a production value of only HK$ 31. The impacts are likely to be negligible. Although Tai Long Wan
and Cheung Chau are of medium-high ranking, the small dredged area of 13.04
hectares at the Adamasta Channel (<1% of the total area of 3844.29 ha and a
production value of HK$ 58,345) is predicted to exert minimal impact to the
Hong Kong fishing industry. Estimation of the affected dredged area is based on
the worst case scenario for the construction method by dredging instead of
direct burying with 0.3m trench width.
The most
abundant organisms in the catch from five out of the six fishery zones were classified
under the mixed fish species category (Table 5-2). The mixed fish species mainly comprise
juveniles of scad (Caranx kalla), rabbit fish
(Siganus
canaliculatus), sardine (Sardinella sp), pony fish, (Leiognathus brevirostris) and gizzard shad (Clupanodon
punctatus). The mixed species are of very low commercial
value (HK$ 1.6 kg-1) and are sold as fish feed for the mariculture
industry. From the species list presented in Table 5-2, the silver
shrimp (Acetes sp) is high value species (>HK$ 15 kg-1) while shrimp
crad (Carnax kalla) and conger pike peel (Muraenosox
cinereus) is medium value species (HK$ 10-15 kg-1). The remainder of the catch are of low value
at <HK$ 10 kg-1.The (FRFO) study final report provides information on the
dependency upon the study final report provides information on the
dependency upon the general area
within which works will occur for various groups of fishermen in the 1996-7
survey period. Among Cheung Chau
vessels, 27 purse seiners took 73% of their catch in the Cheung Chau/South
Lantau area; for 314 mixeds
vessels 78% of their HK catch was from the same area although only 36% of their
time was spent in HK waters; the fished area for the 131 P4/7 vessels was not
detailed but only 40% of their fishing was in HK waters; while for 94 shrimp
trawlers 88% of their HK catch was from the same area although 77% of their
fishing was done outside HK.
The potential
for a high dependence on the study area among particular fishermen can be
further examined from the Fisheries Information Management System (FIMS) mentioned in
the same study report. The sample
survey estimate shows that 382 vessels had fished the general area (Stats zones
0009, 0010, 0030 and 0031) but only 102 fished in the single zone (0009) Tai
Long Wan most closely representing the works area. Only 24 of these vessels spent 75% or more of their fishing
activity in the general area. Less than
half (47) of those fishing in zone 0009 spent more than 10% of their activity
in the zone and none of them more than 20% of their time. Of those most relatively active in zone
0009, 60% (28) were either P4 or non-mechanized sampans.
Periodic
helicopter surveys by AFCD during 2000 recorded gill netters, long-liners and
shrimp trawlers as fishing in the waters between Chi Ma Wan Peninsula and
Cheung Chau.
Table 5-2 Five Most Abundant Fisheries Resources
Caught within the Study Area. High and
Medium Value Species are Underlined.
|
AFD Fishery Area |
AFD Fishery Area Code |
Most Abundant Organisms in decreasing order |
Common name |
|
Chi Ma Wan |
0008 |
Acetes species Mixed fish species* Apogon/Apogonichthys
species Leiognathus
brevirostris Sillago sihama |
Silver shrimp Cardinal fish Pony fish Sand Borer |
|
Tai Long Wan |
0009 |
Acetes species Mixed fish species* Sillago sihama Stolephorus
zollingeri Leiognathus
brevirostris |
Silver shrimp Sand Borer Anchovy Pony fish |
|
Pui O |
0010 |
Acetes species Mixed fish species* Argyrosomus
species Stolephorus
zollingeri Sillago sihama |
Silver shrimp Croaker Anchovy Sand Borer |
|
Cheung Sha |
0011 |
Mixed fish species* Acetes species Argyrosomus
species Stolephorus
zollingeri Sillago sihama |
Silver shrimp Croaker Anchovy Sand Borer |
|
Cheung Chau |
0030 |
Mixed fish species* Sardinella
jussieu Argyrosomus
species Acetes species Caranx kalla |
Saroine Croaker Silver shrimp Shrimp scad |
|
Shek Kwu Chau |
0031 |
Mixed fish species* Stolephorus
zollingeri Argyrosomus
species Muraenosox
cinereus Trachurus
japonicus |
Anchovy Croaker Conger pike eel Scad |
* Mixed fish species composed of juveniles
of Caranx kalla, Siganus canaliculatus,
Sardinella sp, Leiognathus
brevirostris and Clupanodon punctatus
Fisheries Resources
Under the consultancy study on
“Fisheries Resources and Fishing Operations in Hong Kong Waters (1998)” the
only direct sampling of fisheries resources that was conducted near the
dredging area and reclamation workstemporary working platform
was gill netting at Shek Kwu Chau (G8) and trawling at South Cheung Chau (T12)
(Figure 5-2). Coastal mud shrimp (Solenocera crassicornis and Solenoceridae) in night trawl sample,
and mantis shrimp (Oratosquilla nepa)
and goby (Gobiidae) in day trawl
sample comprised the main portion of the catch in terms of weight, and number,
respectively. Croaker (Sciaenidae) comprised the most abundant in the gill net
catches.
The southern Cheung
Chau and southern Lantau waters have been identified as both as spawning area
and nursery ground for fisheries resources. The
Adamasta Channel falls within the defined spawning and nursery grounds
shown in Figures 2 and 3 of the Executive Summary of the FRFO study. Commercial species that have been
identified as using the southern Cheung Chau waters for spawning are the Moray
Eel (Gymnothorax reevesi), the
Scorpionfish (Inegocia japonicus),
the Scad (Caranx kalla), the Flatfish
(Platycephalus indicus), the Bream (Mylio macrocephalus), the Croakers (Nibea diacanthus and Johnius belengeri), the Blue Crab (Portunus pelagicus) and the Mantis
Shrimp (Oratosquilla spp). Commercial
species that have been found to use the southern Lantau waters as a nursery
ground for fry are the Mantis Shrimps (Oratosquilla
anomala) and (Dictyosquilla foveolata)
as well as both Sciaenid and Serranid fry.
Only one designated Fish Culture
Zone (FCZ), Cheung Sha Wan, is identified in the Study Area. The closest distance of the FCZ at Cheung
Sha Wan to the proposed submarine cable routing is approximately 5 km away and
its zone area consist of 214,200m2. There are no
figures available for individual production at this FCZ, although Hong Kong
production in 1998 totalled 1,200 tonnes valued at $85 million. The main species cultured were the
spotted grouper (Epinephelus chlorostigma),
goldlined seabream (Rhabdosargus sarba),
mangrove snapper (Lutjanus
argentimaculatus) and the pompano (Trachinotus
blochii).
In March and April 1998 widespread toxic red tide algal blooms caused fish kills at many of the FCZs in Hong Kong. As a result the estimated production of marine fish culture in 1998 dropped to 1200 tonnes from 2960 tonnes in 1997.
Based on the preceding review of
the available information on the baseline fisheries resources of the waters in
the Study Area, the only identified sensitive receiver which may be
affected by the proposed dredging cable laying operations has been identified asare Cheung Sha Wan FCZ although this has been shown to be outwith the area
of influence and the recognised spawning and nursery
ground where both
sensitive receivers are not co-located.
New ex gratia
arrangements for mariculturists affected by dredging or dumping projects were
approved in July 1993. If, at any one
time, the suspended solids concentration exceeds 50 mg L-1 or exceeds by
100% the highest level recorded at the fish culture zone during the five years
before commencement of works, mariculturists are eligible for ex gratia allowance payments. When such criteria are exceeded, appropriate mitigation measures,
including stopping work if necessary, should be adopted to keep the impact
within acceptable levels. Should ex gratia payments be triggered the eligible mariculturists
may then opt to:
·continue mariculture in the same place at their own
risk, in which case they would be eligible for an ex gratia allowance equivalent to 50 % of the normal
two-year fish culture cycle; or,
·suspend mariculture operations for two years, in
which case they would be eligible for an ex gratia equivalent to
the notional loss of income for a normal two-year fish cycle; or
·cease mariculture operations permanently, in which
case they would receive the existing ex gratia allowance
payable for extinguishment, which contains elements for the notional loss of
income for two years and the loss of capital investment in rafts and cages.
Direct Impacts
Direct impacts to fisheries
resources and fishing operations include minor habitat loss and temporary loss
of a seabed area, which supports fisheries resources due to the reclamation temporary working platform and
dredging associated with the proposed project. Only 0.018 hectares of the Pui
O Fishing Zone (<1%) associated with the small portion of reclamation at Pui
O Wan will lead to minor habitat loss. The direct impact is likely to be
negligible and therefore will not be further discussed in this Fisheries Impact
Assessment.In
Section 6.4.4, the temporary working platform at Pui O will result in the
temporary loss of 180m2 of intertidal sandy shore. However, this shoreline will be
reinstated after completion of the tunnel excavation and thus the shoreline can be
recolonised. The
sandy shore survey conducted at the proposed portal site indicate that the
habitat supports assemblages that are of low diversity and abundance and is
considered to be of low ecological value. As the area to be directly affected
by the temporary
working platform is
of low ecological value and is small in size (180m2), the impact is considered as
acceptable.
Temporary losses in seabed area which supports
fisheries resource due to dredging only constitute a loss of 1% of the Tai Long
Wan Fishing Zone and 0.3% of the Cheung Chau Fishing Zone.Temporary losses in seabed area
which supports fisheries resource due to dredging only constitute a loss of 1%
of the Tai Long Wan Fishing Zone and 0.3% of the Cheung Chau Fishing Zone.
Although Tai
Long Wan and Cheung Chau are of medium-high ranking, the small dredged area of
13.04 hectares at the Adamasta Channel (<1% of the total area of 3844.29 ha
and a production value of HK$ 58,345) is predicted to exert minimal impact to
the Hong Kong fishing industry.With reference to the level of fishing activity
already stated in section 5.3.2, few fishermen are likely to be heavily
dependent on the area, in which the loss in fisheries production is
expected to be insignificant and short term. Estimation of
the affected dredged area is based on the worst case scenario for the
construction method by dredging instead of direct burying with 0.3m trench
width.Short-term direct disturbance of the seabed is
predicted to occur only within the dredging area during dredging operation.
The
expected duration of cable
laying by dredging operationand direct burying is a total of about108 and 13 weeks (Refer to Figure 2.4 Outline Construction Program)respectively but this is
subject to the construction method and cable material being used. In perspective of the environmental, direct burying
is undoubtedly a
favoured construction method for cable laying. Upon
completion of dredging operations it is expected that the seabed fauna will
recolonise and the affected area will be resumed to support fisheries
resources.
The submarine cables will be covered by concrete slabs
of approximate dimensions 2m(W)x3m(L)x0.3m(D) as protection against maintenance dredging. They will be placed on
the seabed by barge and
crane or diver. The concrete slabs will
gradually be affected by natural sedimentation patterns in the area and
covered, thereby re-establishing the base stratum. It takes about 3 months to
complete the installation of protective concrete slabs.
Indirect
Impacts
Indirect impacts to fisheries resources during construction include sediment release associated with dredging works. Potential impacts to water quality from sediment release are as follows:
· increased concentrations of suspended solids (SS);
· a resulting decrease in dissolved oxygen (DO) concentrations; and
· an increase in nutrient concentrations in the water column.
Suspended sediment fluxes occur naturally in the marine environment. Consequently, fish have evolved behavioural adaptations to tolerate increased SS loads. These include clearing their gills by flushing water over them. When SS levels become excessive fish can move to clearer waters. Susceptibility generally decreases with age, with eggs the most vulnerable and adults the least sensitive to effects from sediments. The rate, season and duration of SS elevations will influence the type and extent of impact upon fish.
Based
on the results contained in “EPD Marine Water Quality for 1999”, the sediment
sampled at SS5 monitoring station closest to the proposed submarine cable
across the Adamasta Channel
were found to be uncontaminated
(refer to Table 5-3). Therefore, the release of contaminants from
sediments into the receiving waters will not be of concern. As SS release due
to the construction works will be minimal, impacts derived from elevations of
SS and nutrients and DO depletion are likely to be negligible and therefore
acceptable to fisheries resources in the Study Area.
Table 5-3 Summary
of Sediment Quality Monitoring Results for SS5 in 1999
demonstrated that the level of
further testing (if any) which needs to be carried out before disposal. Since
only if dredging is undertaken will disposal of marine deposits be required.
The direct burying method does not generate waste for off-site disposal which
is another reason why it is a favoured construction method.
Note: Data presented are in annual medians of
monthly samples
Bolded value indicates non-compliance with the
LCEL.
(Source: Adopted from EPD
Marine Water Quality for 1999)
Potential Impacts to Cheung Sha Wan Fish
Culture Zone and the
Spawning and Nursery Ground in Adamasta Channele
The Cheung Sha Wan Fish Culture
Zone 5km away in areas where is farther away from the cable laying site and full
complicance with the WQO’s is predicted for direct burying. For dredging some exceedances occur and
mitigation measures are required to achieve compliance as indicated in Section
4. Water
quality modelling (see Section 4) has
indicated that in the range between 0.0 and 0.7 less than 1increase in
SS at the Cheung Sha Wan Fish Culture Zone will not exceed the Water Quality
Objectives. As predicted elevation in SS, and consequently depletions in DO and increase in nutrients and contaminants, are very low
in areas farther away from the dredging area, the Cheung Sha Wan Fish Culture
Zone 5km away and other fisheries resources within the Study Area are not
predicted to be affected.The submarine cable route passes through the fast
flowing Adamasta Channel which is part of the overall spawning and nursery
ground. The impacts associated with cable laying by the preferred method direct
burying will be short in duration (13 weeks maximum). Though general WQO set by
EPD are not set specifically protect spawning and nursery function, when SS
levels become excessive, fish often move to less affected areas. It is also noted that the
sediments in the area are not generally highly polluted and coupled with a
relatively low sediment release, it is expected that DO depletion would be
negligible and a very transient, short term impact as stated in Section 4.5.2.
For the direct burying, no specific mitigation measures
are required other than due care during the works
as there is full compliance with the WQO’s implement
the measures given in Section 4 for protection of water quality to also
safeguard fishery resources. Mitigation measures such as using
closed grab and silt curtain (details refer to section 2.5 of R Recommended Pollution Control
Clauses for Construction Contract and Section 4 of this Report) would
reduce SS loss to the water column during dredging operations. However, as SS released due to
the construction works is predicted to be minimalrelatively
small and of short duration and in particular, the need to implement such
mitigation measures will be determined during the Detailed Design stage.In order to minimise the
potential impacts on the recognised spawning and nursery grounds at Adamasta
Channel, it is recommended to implement the aforesaid mitigation measures.
During the operation of the submarine cable across the Adamasta Channel, no impacts to fisheries resources and fishing operations are predicted to occur as the proposed cable will be buried 3m below the seabed.
The severity of impact on fisheries associated with the construction works is considered low. An evaluation of the impact in accordance with the TMEIA Annex 9 is presented as follows:
· Nature of Impact: Short-term impacts to the fisheries resources within the dredging area and its immediate vicinity are perceived. It is worth noting that dredging will take a longer time than direct burying and thus create a greater interference with fishing activity and also possibly with the utility of the area as a spawning and nursery ground. The duration of predicted impacts on resources for dredging, direct burying and laying the protective capping is 108 weeks, 13 weeks and 12 weeks respectively. Direct burying would lead to greater short-term water quality perturbations but over a much shorter period. As a result of minor perturbations to water quality in the Study Area, short-term impacts to the fisheries resources are predicted to occur. Upon completion of dredging operation it is expected that the seabed fauna will recolonise and the affected area will be resumed to its original role of supporting fisheries resources.
·
Size of Affected Area: 180m2 temporary loss on intertidal sandy shore habitats with low ecological value due to temporary working platform at Pui O is anticipated. Pui O is considered as low
ranking to the Hong Kong fishing industry. The small reclaimed area will only
cover 0.018 hectares which constitutes less than 1% of the total area
(596.51ha). The estimated temporarily affected area
by dredging which covers
approximately 13.04 ha which covers approximately 13.04 hectares is
confined mainly to the dredging area at the Adamasta Channel and its immediate
vicinity whereas by direct
burying covers about 0.621ha affected area whereas direct burying. A
temporary loss of a seabed area which supports fisheries resources will occur
due to dredging. The benthnic community within the dredging area will be
disturbed during dredging operation but is expected to recolonise once the
proposed works are completed.
·
Size of fisheries resources/production: Potential Directly impacted
areas at Tai Long Wan and Cheung Chau are both ranked medium-high in comparison
to other areas in Hong Kong in terms of catch weight and value. With reference to the level of
fishing activity already stated in section 5.3.2, few fishermen are likely to
be heavily dependent on the area, in which the loss in fisheries production is
expected to be insignificant and short term. Indirectly impacted areas in the Study Area are
ranked from low to medium-high to the Hong Kong fishing industry. However, as the construction impacts are
predicted to be transient and localised, their influence on fisheries
resources/production should be minimal and therefore insignificant.
·
Destruction and disturbance of nursery and spawning
grounds: The closest nursery and spawning grounds are located at Cheung Chau and South Lantau and in the south Cheung
ChauAdamasta Channel. The submarine cable route
passes through the fast flowing Adamasta Channel which is part of the overall
spawning and nursery ground. The impacts associated with cable laying by the
preferred method direct burying will be short in duration (13 weeks maximum).
Though general WQO set by EPD are not set specifically protect spawning and
nursery function, when SS levels become excessive, fish often move to less
affected areas. It is also noted that the sediments in the area are not
generally highly polluted and coupled with a relatively low sediment release,
it is expected that DO depletion would be negligible and a very transient,
short term impact as stated in Section 4.5.2. Hence, the potential impact on the spawning and
nursery ground is anticipated to be insignificant. in the range
between 0.0 and 0.7 less than 1be edIf compliance
with the Water Quality Objectives is achieved at this area, the potential
impacts through SS elevations and DO depletion are expected to be negligible.
·
Impact on Fishing Activity: Based on the existing limited fishing
activity, due to busy marine traffic in the Study Areaaforementioned information stated in section 5.3.2 on fishing activity and few
fishermen are likely to be heavily dependent on the area, the impact on
fishing activity is expected to be negligible. The reduced duration of the disturbance using direct burying (13 weeks) maximum) compared to dredging (108 weeks), is one of the key reasons why direct burying is a favoured construction method.
· Impact on Aquaculture Activity: As SS elevations and DO depletions are predicted to be in compliance with the Water Quality Objective at the Cheung Sha Wan FCZ, impacts to this sensitive receiver are expected to be negligible.
The Contractors should take all
necessary steps to avoid impacts to water quality during the cable laying in
order to prevent any potential impacts to fisheries resources and fishing
operations. It is considered that the protection measures recommended in
Section 4.8.16 to control impacts to water quality to
within acceptable levels, are also expect to control impacts to fisheries
resources as well as fishing operationsand fish
culture operations. Impacts
on fishing operations can be reduced by confining the construction area in the
radius of 50m from the laying barge and burying machine from Marine Department.
Thus,
no specific mitigation measures for fisheries resources are required during
construction of the cable.Since works will take place in a recognised
spawning and nursery grounds at Adamasta Channel, consideration should be taken
by the Contractors to protect life stages such as eggs and larvae of commercial
resources that stated in section 5.5.1. Appropriate mitigation measures are recommended in
the event that dredging in the option selected.
The monitoring and audit
activities, designed to detect and mitigate any unacceptable impacts on water
quality and marine ecology, will also serve to protect against unacceptable
impacts on fisheries resources. The
EM&A programme will provide management actions and supplemental mitigation
measures to be employed should impacts arise, thereby ensuring the
environmental acceptability of the project.
As insignificant impacts to the fisheriesry are expected to
occur after implementation
of the proposed mitigation measures no specific , the development and implementation
of a monitoring and audit programme specifically designed to assess
the effects on commercial fisheries resources is not necessaryhas been recommended.
A review of existing information
indicates that the Study Area supports fisheries resources and fishing
operations. As impacts
resulting from the project will be confined to dredging and reclamation, no
adverse impacts to fisheries resources are expected. Impacts from
the project will be confined to reclamatiothe temporary working flatformn and the chosen method of cable laying/protection
which may be either by dredging or direct burial. The size of
impact due to dredging and reclamation temporary work areas at Pui O is predicted to
minor. The potential impact
on the spawning and nursery ground is anticipated to be insignificant. Generally the
mitigation measures which are recommended to control water quality impacts to
within acceptable levels, are also expected to control impacts to fisheries
resources. Therefore, no fisheries-specific mitigation
measures are required.In addition to which, appropriate mitigation measures are proposed such as adoption of direct
burying as the preferred cable laying method and using shield over the face of the cutter to
suppress the release and dispersion of sediments to the water column.
Direct
Impacts
Direct impacts to fishing
operations and resources will occur through minor habitat loss and temporary
loss of a seabed area (approximately 13.04 hectares) which
supports fisheries resources due to dredging between / small-scale
reclamation works at Tai Long Wan, and
Cheung Chau.
and Pui O. 0.055ha
permanent loss on The intertidal sandy shore habitats with low ecological
value due to proposed
reclamation works at temporary
working platform Pui
O is anticipatedwill be
temporarily displaced but could recoglonise following re-installmentre-instatement of the
shoreline after completion of the tunnel excavation. The direct impact lead to minor habitat loss due to
a small scale of reclamation at Pui O Wan is likely to be negligible.
The expected maximum duration expected for cable laying by dredging and
direct burying is 108 and 13 weeks respectively. From an environmental perspective, direct burying is undoubtedly
a favoured cable laying method. As direct impacts are predicted to occur
only within the Construction Area during
constructionand few fishermen are likely to be heavily
dependent on the area, the loss in fisheries production is expected to be
insignificant and short term..
Indirect
Impacts
Indirect impacts during the
construction phase include an increase in suspended sediment concentrations and
decrease in dissolved oxygen in the water column. SS fluxes occur naturally in the marine
environment, consequently fish have evolved behavioural adaptations to tolerate
increased SS loads. These include
clearing their gills by flushing water over them. When SS levels become excessive fish can move to clearer waters. Susceptibility generally decreases with age,
with eggs the most vulnerable and adults the least sensitive to effects from
sediments. The rate, season and
duration of SS elevations will influence the type and extent of impact upon
fish. SS levels predicted by water quality
modelling shows that WQO will be met in most situations and therefore
there would only be transient and localised impact on fisheries resources,
including the spawning and nursery grounds of Cheung Chaua and South Lantau and in Adamasta
Channel and the Cheung Sha Wan FCZ. However, these indirect impacts are
anticipated to be localized and transient.
In addition, any constraints measures on construction operations recommended
to reduce impacts to water quality and marine ecology to acceptable levels are
expected to also mitigate for effects on fisheries resources. Therefore, no
special mitigation measures are recommended for the fisheries sensitive
receivers. Those mitigation measures on marine ecology, which
are related to the protection of fisheries resources, are summarised in the
Implementation Schedule.