This Section of the EIA Report
presents the findings of an assessment of the impact of construction and
operation of the proposed East of Sha Chau Facility on existing fisheries resources,
fishing operations and fish culture activities based on the Project Description
(Part 3, Section 1) and the
findings of the Water Quality Impact Assessment (Part 3, Section 2). A
series of fisheries sensitive receivers were identified in the Study Area from
a review of baseline information as follows:
·
Fish Culture Zone at Ma Wan;
·
The seasonal spawning ground in northwestern waters;
and,
·
The two artificial reef complexes (Airport and Marine
Park).
The focus of the impact assessment
will be on these sensitive receivers.
A desktop literature review (Part
1, Section 4) was conducted in order to establish the fisheries importance
of the area within and surrounding the East of Sha Chau Facility. Information from the water quality
assessment was used to determine the size of the study area as that potentially
affected by perturbations to water quality parameters (Part 3, Section 2).
This area became the Study Area for this fisheries impact assessment. The importance of potentially impacted
fishing resources and fisheries operations identified within the Study Area was
assessed using the EIAO-TM. The potential impacts due to the
construction and operation of the East of Sha Chau Facility have been assessed
(following the EIAO-TM Annex 17 guidelines) and the impacts
evaluated (based on the criteria in EIAO-TM
Annex 9).
As discussed in Part 3, Section 1 the proposed East of Sha Chau Facility will consist
of four purposely dredged seabed pits.
The pits will be dredged sequentially prior to backfilling with
contaminated mud and capping with uncontaminated mud. Impacts associated with the East of Sha Chau Facility are
thus divided into those occurring during the dredging of pits and those during
backfilling with contaminated mud and capping with uncontaminated mud. Following this assessment the potential
for residual impacts and cumulative impacts associated with concurrent
projects, or through the combination of the above works, are discussed.
Impacts to the fisheries resources
and sensitive receivers potentially arising from backfilling operations at the
East of Sha Chau Facility are as follows:
Impacts to water quality through
both grab and trailer disposal backfilling operations have been discussed in Part
3, Section 2.
Through detailed water quality
modelling it has been identified that backfilling operations will cause an
increase in suspended solid concentrations in the water column. Due to the greater loss rates
associated with trailer disposal backfilling works, predicted concentrations
calculated for these works have been used in the assessment as they thus
represent a worst-case scenario.
Suspended Solids
Suspended sediment (SS) fluxes occur
naturally in the marine environment, consequently fish have evolved behavioural
adaptations to tolerate increased SS load (eg, clearing their gills by flushing
water over them). Where SS levels become
excessive, fish will move to clearer waters. This level is defined as the tolerance threshold, which
varies from species to species and at different stages of the life cycle.
Ma Wan Fish Culture Zone (FCZ): Water quality
modelling results presented in Part 3, Section 2 have shown that the
maximum SS elevation at the FCZ as a result of backfilling operations is < 1
mg L-1. These values do
not exceed tolerance reported in adult fish at values below 125 mg L-1 ([1]),
or the guideline values identified for fisheries and selected marine ecological
sensitive receivers as part of the recent study for AFCD (50 mg L-1
- based on half of the no observable effect concentrations) ([2]). Impacts to the Ma Wan FCZ as a result
of the backfilling works are thus unlikely to occur as the increases in SS are
expected to be negligible.
Seasonal
Spawning Ground: SS
concentrations predicted to exceed the WQO are expected to stay within
relatively close proximity to backfilling operations (Part 3, Section 2). As high concentrations of SS generally
not predicted to occur in the surface layer, where most fish larvae, eggs and
fry are likely to be found post-spawning, impacts are expected to be low.
Artificial
Reefs: The
predicted elevations of SS concentrations at the ARs within the Marine Park and
at the Airport Exclusion Zone as a result of backfilling operations are very
low and compliant with the WQO (maximum = 2 mg L-1 (dry season) and
3 mg L-1 (wet season)).
As such, impacts are not expected to occur.
Dissolved Oxygen
Nutrients
Aside from the effects of SS, DO and
nutrient release on the water column, backfilling operations have the potential
for release of contaminants during disposal activities. Contaminant impacts to fisheries may
arise as a result of:
·
accumulation of contaminants in the tissue of fish and
invertebrates resulting in sublethal effects which may affect behaviour,
reproduction and increasing susceptibility to disease; and
·
increased mortality, and sub lethal effects to, eggs,
larvae and juvenile species, as these are particularly sensitive to elevated
contaminant concentrations.
Contaminants that accumulate in
commercially important fish species may ultimately impact human health. In order to investigate this potential
expected elevations in the body burden values of marine organisms as a result
of backfilling operations at the East of Sha Chau Facility have been determined
through a bioaccumulation assessment (Annex B). Predictions in the water quality
assessment have indicated that the release of contaminants during backfilling
operations at the East of Sha Chau Facility will cause only minor elevations in
the immediate vicinity of the pits.
Consequently, the bioaccumulation assessment has indicated that
elevations in body burden levels are expected to be minor. The implications of these elevations to
the health of the Indo-Pacific Humpback Dolphin, Sousa chinensis, and human
health through consumption of these organisms are discussed in Part 3,
Section 5 and Annex C.
In addition to the above, it is
important to note that a review of long term biomonitoring data collected in the
East of Sha Chau area has indicated that current disposal operations are not
resulting in an increase in contaminants in target species tissue levels ([3]). As such, backfilling operations in the
East of Sha Chau Facility are also not expected to result in unacceptable
impacts to fisheries resources with regard to contaminant loading.
Dredging, backfilling and capping
plant have frequented the waters surrounding the proposed East of Sha Chau
Facility for approximately ten years.
Fishing vessels that frequent these waters are, therefore, experienced
in navigating waters where such plant are in operation. As such, it is not expected that the
marine vessels will interfere with the fishing activities in this area.
Impacts to the fisheries resources
and sensitive receivers potentially arising from dredging operations at the
East of Sha Chau Facility are as follows:
The construction of
the East of Sha Chau Facility will result in the direct temporary loss of
approximately 106 ha, or 2.7%, of active AFCD Fishing Zones within northwestern
Lantau waters. Based on
information presented in Part 1, Section 4, this would result in a
temporary loss of 7,448 kg yr-1 adult fisheries production and 110
kg yr-1 of fry fisheries production, equating a 1.1 % and 0.5 % of
the Fishing Zones production, respectively. These numbers are considered to be low. No unacceptable impacts to the annual
fishery as a result of dredging operations at the East of Sha Chau Facility are
therefore considered to occur through dredging operations.
It should be noted that once
dredging, filling and capping works associated with the East of Sha Chau
Facility are completed, the seabed and hydrodynamic regime is expected to their
original condition. A review of
long term monitoring in and around the existing capped pits at East of Sha Chau
has demonstrated that within a relatively short period of time, recolonisation
of sediments occurs returning the site to a pre-dredged state ([4]) ([5]). Initially capped pits will be colonised
by infaunal opportunists and during the early stages of recovery and diversity
is expected to be low. However, as
more competitive species begin to colonise, the diversity of the infaunal,
epifaunal benthic assemblages and demersal fisheries resources will increase
until it returns to pre-dredged conditions.
Suspended Solids
Ma Wan Fish Culture Zone (FCZ): Water quality
modelling results presented in Part 3, Section 2 have shown that the
maximum SS elevations at the FCZ as a result of dredging operations is < 1
mg L-1, which is well within the acceptable range and is not
expected to cause adverse impacts.
Seasonal
Spawning Ground: SS
concentrations predicted to exceed the WQO are expected to stay within
relatively close proximity to dredging operations (Part 3, Section 2). As described for backfilling
operations, impacts to the surface layer of the water column are minimal,
therefore, impacts to the seasonal spawning ground are expected to be of low
severity.
Artificial
Reefs:
Predicted elevations of SS concentrations at ARs as a result of dredging
operations are very low and compliant with the WQO (Marine Park AR: maximum =
< 2 mg L-1 (dry season); Airport Exclusion Zone AR: maximum =
< 3 mg L-1 (wet season)).
As such, no impacts to fisheries resources at the ARs as a result of
dredging operations are expected to occur.
Dredging, backfilling and capping
plant have frequented the waters surrounding the proposed East of Sha Chau
Facility for approximately ten years.
Fishing vessels that frequent these waters are, therefore, experienced
in navigating waters where such plant are in operation. As such, it is not expected that the
marine vessels will interfere with the fishing activities in this area.
Impacts to the fisheries resources
and sensitive receivers potentially arising from capping operations at the East
of Sha Chau Facility are as follows:
Suspended Solids
Ma Wan Fish Culture Zone (FCZ): Water quality
modelling results presented in Part 3, Section 2 have shown that the
maximum SS elevations at the FCZ as a result of capping operations is < 1 mg
L-1, which is well within the acceptable range and is not expected
to cause adverse impacts.
Seasonal
Spawning Ground: SS
concentrations predicted to exceed the WQO are expected to stay within relatively
close proximity to capping operations (Part 3, Section 2). As described under Section 4.3.1,
elevations in SS are not expected to occur in the surface layer, where most
fish larvae, eggs and fry are likely to be found post-spawning, therefore, impacts
to the seasonal spawning ground are expected to be of low severity.
Artificial
Reefs:
Predicted elevations of SS concentrations at the Marine Park and Airport
Exclusion Zone ARs within as a result of capping operations are very low and
compliant with the WQO (maximum = < 1 mg L-1 (dry season) and<
1 mg L-1 (wet season)).
As such, no impacts to fisheries resources at the ARs as a result of
capping operations are expected to occur.
Dredging, backfilling and capping
plant have frequented the waters surrounding the proposed East of Sha Chau
Facility for approximately ten years.
Fishing vessels that frequent these waters are, therefore, experienced
in navigating waters where such plant are in operation. As such, it is not expected that the
marine vessels will interfere with the fishing activities in this area.
The only residual impact identified
that may affect commercial fishing operations as a result of the construction
and operation of the East of Sha Chau Facility is the disturbance to fishing
activities during the lifetime of the mud disposal facility. However, the severity of this residual
impact is predicted to be no greater than during previous or ongoing mud
disposal activities at the Contaminated Mud Disposal Facility at East of Sha
Chau which have been shown through a review of long term fisheries resources
data to cause to have no detectable adverse impacts to fisheries ([7]).
The water quality impact assessment
section has presented a discussion on the impacts of cumulative activities on
water quality. Cumulative impacts
to fisheries resources and fishing operations may arise from concurrent
dredging, backfilling or development projects in the area. In addition, cumulative impacts through
the combination of dredging, backfilling and capping operations within the East
of Sha Chau Facility have the potential to occur.
It is apparent that the elevations
of SS are higher when concurrent activities are examined as opposed to when
backfilling or dredging is examined separately.
·
Elevations at the Ma Wan FCZ not predicted to exceed 2
mg L-1 (dry season) which is within the tolerance criteria discussed
above and consequently, acceptable.
·
The majority contributor to the cumulative impact
results appears to be Type 1, or Type 1 (dedicated), disposal operations at the
North Brothers MBA. Should
operational controls be employed to manage disposal operations they should
focus on operations at the North Brothers MBA. Operations within the proposed East of Sha Chau Facility, ie
dredging, backfilling and capping were shown to be able to proceed concurrently
in an environmentally acceptable manner.
·
Under the cumulative scenario, the AR within the
Marine Park has the potential to experience maximum elevations of SS of < 2
mg L-1 (wet season – barge disposal). These impacts are below the WQO and are considered to be
acceptable.
The construction and operation of
the proposed East of Sha Chau Facility has been shown to proceed at rates that
maintain environmental impacts to within acceptable levels. Actual impacts during the works will be
monitored by through a detailed Environmental Monitoring and Audit (EM&A)
programme. Full details of the
EM&A programme are presented in the EM&A Manual which has been based on
the on-going and previous monitoring programmes conducted at the Contaminated
Mud Disposal Facility at East of Sha Chau. This programme will provide management actions and
supplemental mitigation measures to be employed should impacts arise, thereby
ensuring the environmental acceptability of the East of Sha Chau Facility.
Reviews of existing information on
commercial fisheries resources and fishing operations located within the Study
Area have been undertaken.
Information from a study on fishing operations in Hong Kong and the AFCD
Port Surveys indicate that fisheries production values in the vicinity of the
East of Sha Chau Facility vary but are medium to low.
The construction and operation of
the East of Sha Chau Facility may give rise to impacts from disturbances to
benthic habitats, changes in water quality and contaminant release. Disturbances to benthic habitats are
predicted to be confined within the pit boundaries of the East of Sha Chau
facility, and recolonisation of sediments is expected to occur following
completion of works. As changes in
water quality are minimal and transient, adverse impacts to fisheries resources
are not predicted to arise.
Assessment of contaminant release has indicated that the minimal concentrations
will be minimal and well within the relevant criteria.
While no special mitigation measures
are required for fisheries resources, mitigation measures recommended to reduce
impacts to water quality are also expected to mitigate any impacts to fisheries
resources