This Section presents a summary of the key potential
environmental outcomes associated with the construction and operation of the
proposed East of Sha Chau Facility.
The purpose of the assessment was to thoroughly evaluate the East of Sha
Chau Facility in terms of predicted impacts to water quality from dredging,
backfilling and capping of the pits and also concurrent activities. It should be noted that the facility is
proposed to be developed in close proximity to the existing East of Sha Chau
facility which have been demonstrated to operation in an acceptable manner as
indicated by the findings of an intensive EM&A programme.
Computer modelling was used to simulate the loss of sediment
to suspension during dredging, backfilling and capping operations. The assessment concluded that any
sediment disturbed by the works would settle rapidly back onto the seabed and
the suspended sediment elevations would be of short duration. This means that there would be little
transport of suspended sediment away from the pits and that the sediment would
not impact upon sensitive receivers.
An EM&A programme has been devised to confirm that the works would be
environmentally acceptable.
Through the application of criteria utilised in previous
EIAs in Hong Kong, impacts arising from the proposed dredging, backfilling and
capping operations at the East of Sha Chau Facility are predicted to be within
acceptable levels (as defined by the WQOs) and are not expected to cause
adverse impacts to marine sensitive receivers of either high or medium
ecological value (habitats or species).
The loss of the subtidal habitats present within the pit boundaries are
considered to be acceptable as the habitats are of low ecological value. Furthermore, recolonisation of the
capped pits by infaunal organisms and epibenthic fauna is expected to occur
following the completion of capping operations.
The residual impacts occurring as a result of the
construction and operation of the East of Sha Chau Facility are confined to the
loss of the low ecological value subtidal habitats present within the pit
boundaries. The residual impacts
are considered to be acceptable as the habitats are of low ecological value and
because infaunal organisms and epibenthic fauna are expected to recolonise the
sediments.
Water quality modelling of the cumulative impacts of
projects planned to be constructed simultaneously has been conducted. The findings indicated that no adverse
impacts would be expected to water quality sensitive receivers when compared
the allowable increases as defined by the WQO. Unacceptable cumulative impacts as a result of concurrent
project construction and operational activities are, therefore, unlikely to occur
and hence cumulative impacts to marine ecology are not anticipated.
To protect against unacceptable impacts to marine ecological
resources, an EM&A programme has been designed to specifically detect and
mitigate any unacceptable impacts to marine ecological resources.
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.
The carcinogenic risk assessment has indicated that risks
associated with consumption of seafood were below the acceptability criterion
for both the East of Sha Chau and the Background areas. Results of the hazard assessment
indicated that risks associated with consumption of seafood were below the
acceptability criterion for both the East of Sha Chau and the Background areas.
In addition, it does not appear that Indo-pacific Humpback
dolphin prey organisms are predicted to bioaccumulate contaminants to higher
concentrations than in prey of the same species from nearby reference
locations. These results indicate
that the disposal of contaminated sediments at the proposed East of Sha Chau
Facility is not predicted to contribute to an increased risk of harm to
Indo-pacific Humpback dolphins.
Noise impact associated with the dredging, backfilling and
capping works at the East of Sha Chau Facility have been assessed. It has assumed that 2 grab dredgers
will be deployed on-site for dredging work and 1 barge for backfilling or
capping activity. Since restricted
hours construction activities may be required, the prediction results were
compared against the EIAO-TM daytime (non-restricted hours) and the
evening (1900 – 2300) and night-time (2300 – 0700) restricted hours criteria.
The results indicated that the criteria for daytime, evening
and night-time works will comply at all representative NSRs. No mitigation measure is recommended.
The review of the literature indicated that the region
adjacent to the East of Sha Chau Facility had been occupied for over 4,000
years and had been a focal point for Chinese and international maritime
trade. On this basis there is the
potential to include sites and objects of archaeological and historical
significance; however, a review of charts identified no shipwreck records.
Geophysical survey findings indicated that the area has been
heavily disturbed by anchoring, trawling and dredging. The likelihood of the area containing
any well-preserved remains is considered minimal.
No cultural heritage resources were found
below the seabed in the East of Sha Chau Facility from the review of
geophysical survey data. No marine
archaeological resources were identified at the site of the East of Sha Chau
Facility and hence the proposed development will impose no impact to marine
archaeological resources.
The construction and operation of the proposed East of Sha
Chau Facility has been demonstrated at rates that maintain environmental
impacts to within acceptable levels.
Actual impacts during the works will be monitored 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.
No unacceptable residual impacts are predicted for the
construction and operation of the facility at the East of Sha Chau site.
The EIA study has facilitated the integration of
environmental considerations into the design process for the Project. The principal measures identified are
those achieved through pit and dredging design and backfilling and capping
working rates. In addition, a
number of mitigation measures have been identified to minimise the potential
for adverse environmental impacts.
The mitigation measures are detailed in full in the Implementation
Schedule (Annex E) and will be implemented by the Contractor under enforcement
by the EPD.
One of the key environmental outcomes has been the ability
to plan, design and ultimately construct the project so that direct impacts to
sensitive receivers are avoided, as far as practically possible. A detailed assessment of alternative
sites within the Study Area has been conducted. Through this assessment, environmentally sensitive areas
have been protected by the following means.
·
Avoidance
of Direct Impacts to Ecologically Sensitive Habitats: The site for the East of Sha Chau Facility has been selected
based on a review of the environmental considerations of the area and the most
environmentally preferable site within the Study Area has been selected to
avoid direct impacts to ecologically sensitive habitats and species.
·
Avoidance of Indirect Impacts
to Ecologically Sensitive Habitats:
The site for the East of Sha Chau Facility has been selected so that it
is located at a sufficient distance from ecological sensitive receivers so that
dispersion of sediment from dredging, backfilling and capping operations does
not affect the receivers.
As a result, it is not expected that the
construction and operation of the East of Sha Chau Facility will result in
adverse impacts to environmentally sensitive areas.
A key concern in the final site and disposal option design
was to take steps to ensure hat both direct and indirect impacts through
dredging, backfilling and capping operations were avoided or minimised. Consequently, the following approaches
were adopted.
·
Adoption
of Existing Practices: A review of all environmental
monitoring data collected since the commencement of operations at East of Sha
Chau Contaminated Mud Disposal Facility demonstrates that mud disposal
activities at the East of Sha Chau area have remained within environmentally
acceptable levels. As all
dredging, backfilling and capping operations proposed for the East of Sha Chau
Facility have been designed to follow the current practices, no adverse
unacceptable impacts are expected to occur.
·
CMP Design: The East of Sha Chau CMPs have been designed as four
separate pits which minimises the exposure time of contaminated mud to the
marine environment and consequently reduces the magnitude of any potential
impacts.
·
Adoption of Acceptable Working
Rates: The modelling work has demonstrated
that the selected working rates for the dredging, backfilling and capping
operations will not cause unacceptable impacts to the receiving water quality. Consequently, unacceptable indirect
impacts have been avoided.
Key environmental problems have been avoided through the
detailed site selection process that, as discussed above, allowed
environmentally sensitive areas and populations to be avoided. In addition, through the employment of
practices that have been demonstrated to be environmentally acceptable, no
environmental problems are expected to occur as a result of the construction
and operation of the proposed East of Sha Chau Facility.
The construction and operation of the proposed East of Sha
Chau Facility will result in the temporary loss of low ecological value soft
bottom habitat. Following the
completion of capping operations, the seabed will be reinstated and is expected
to return to pre-dredging conditions.
As a result, compensation areas are not deemed necessary.
The design of the East of Sha Chau Facility will involve the
dredging of purpose-dredged pits, backfilling with contaminated mud and
subsequent capping with uncontaminated mud to return the seabed and
hydrodynamic regime to their original condition. A review of long term monitoring data from 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.
The employment of such environmental protection methods in the design of
the East of Sha Chau Facility will, therefore, act as an environmental benefit.