This Section of the EIA Report presents the findings of an
assessment of the impact of construction and operation of the proposed South
Brothers Facility on existing fisheries resources, fishing operations and fish
culture activities based on the Project Description (Part 2, Section 1) and the findings of the Water
Quality Impact Assessment (Part 2,
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
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 South Brothers 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 2, 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 South Brothers 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
2, Section 1 the proposed South Brothers Facility will consist of three
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 South Brothers 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 South Brothers Facility
are as follows:
Impacts to water quality through both grab and trailer
disposal backfilling operations have been discussed in Part 2, 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 2, 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.
?/span>
Seasonal Spawning Ground: ?/span>SS concentrations predicted to exceed the WQO are expected to stay
within relatively close proximity to backfilling operations (Part 2, Section
2).?As the South Brothers Facility
lies outside the area that is generally considered to be a seasonal spawning
area for commercial fisheries resources, which makes up the majority of central
northwest Lantau waters, impacts to these seasonal spawning grounds are
expected to be low.?In addition, it is
worth noting that where relatively high concentrations of SS have been
identified as having the potential to occur through backfilling operations, these
are generally not predicted to occur in the surface layer, where most fish
larvae, eggs and fry are likely to be found post-spawning.
Artificial Reefs:?The predicted elevations of SS concentrations at the ARs within
the Marine Park as a result of backfilling operations are very low and compliant
with the WQO (bottom layer = < 1 mg L-1 (dry season)).?Impacts, however, at the AR within the
Airport Exclusion Zone are expected to occur.?
SS elevations at this sensitive receiver have been predicted from the
backfilling works cause an elevation of 21 mg L-1 (wet season).?Although these impacts exceed the WQO it
should be noted that these predictions have been made at the bottom layer.?When the depth average elevations are examined
(Annex A) it can be seen that the maximum depth average elevations are
< 10 mg L-1 in both the wet and dry seasons.?These elevations, although above the WQO
(annual of 5.7 mgL-1), are not expected to cause unacceptable
impacts as such variations in SS values are observed throughout the year in
this area.?Consequently, any species
present on the ARs are expected to be tolerant of such SS elevations.?
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.?
Investigation of this potential expected elevations in the body burden
values of marine organisms as a result of backfilling operations at the South
Brothers Facility has 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 South Brothers 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 2,
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 South Brothers Facility
are also not expected to result in unacceptable impacts to fisheries resources
with regard to contaminant loading.?
Backfilling operations at the South Brothers Facility will
introduce plant into an area where they do not occur frequently at
present.?This has the potential to
interfere with fishing vessel use of the area.?
Information from the Port Survey has indicated that small vessels such
as P4s mainly use the area ([4]).?Given that these vessels are highly mobile it is not expected
that the marine vessels will interfere with the fishing activities of the small
vessel operators in this area.
Impacts to the fisheries resources and sensitive receivers
potentially arising from dredging operations at the South Brothers Facility are
as follows:
The construction of the South Brothers
Facility will result in the direct temporary loss of approximately 164 ha, or
4.2%, 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 21,911 kg yr-1
adult fisheries production and 105 kg yr-1 of fry fisheries
production, equating a 2.7 % 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 South
Brothers Facility are therefore considered to occur through dredging
operations.
It should be noted that once dredging, filling and capping
works associated with the South Brothers Facility are completed, the seabed and
hydrodynamic regime is expected to restore 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 ([5]) ([6]).?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 2, 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.
?/span>
Seasonal Spawning Ground: ?/span>SS concentrations predicted to exceed the WQO are expected to stay
within relatively close proximity to dredging operations (Part 2, Section 2).?As described for backfilling operations, the
South Brothers Facility lies outside the seasonal spawning ground and 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.
?/span>
Artificial Reefs:?Predicted elevations of SS concentrations at ARs as a result of
dredging operations are very low and compliant with the WQO (
Dredging operations at the South Brothers Facility will
introduce plant into an area where they do not occur frequently at
present.?As discussed under the
assessment of backfilling operations, information from the Port Survey indicate
that small vessels such as P4s mainly use the area.?Given that these vessels are highly mobile it is not expected
that the marine vessels will interfere with the fishing activities of the small
vessel operators in this area.
Impacts to the fisheries resources and sensitive receivers
potentially arising from capping operations at the South Brothers Facility are
as follows:
Suspended Solids
Ma
Wan Fish Culture Zone (FCZ):?Water quality modelling
results presented in Part 2, 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: ?/span>SS concentrations predicted to exceed the WQO are expected to stay
within relatively close proximity to capping operations (Part 2, Section 2).?As described under Section 4.3.1, the
South Brothers Facility lies outside the area that is to be a seasonal spawning
area for commercial fisheries resources and 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 ARs within as a
result of capping operations are very low and compliant with the WQO (
Dissolved Oxygen
Nutrients
Capping operations at the South Brothers Facility will
introduce plant into an area where they do not occur frequently at
present.?As discussed under the
assessment of backfilling operations, information from the Port Survey indicate
that small vessels such as P4s mainly use the area.?Given that these vessels are highly mobile it is not expected
that the marine vessels will interfere with the fishing activities of the small
vessel operators in this area.
The only residual impact identified that
may affect commercial fishing operations as a result of the construction and operation
of the South Brothers 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 have no detectable
adverse impacts to fisheries ([8]).
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 South Brothers 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.
?/span>
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. ?/span>Operations within the
proposed South Brothers 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 Airport Exclusion Zone has the
potential to experience maximum elevations of SS of < 3 mg L-1
(wet season – barge disposal).?As
such, no exceedances of the WQO are expected to occur.
?
The construction and operation of the proposed South Brothers
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 South Brothers
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
The construction and operation of the South Brothers
Facility may give rise to fisheries 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 South Brothers
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 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.