Detailed Site Selection Study for a Proposed Contaminated Mud
Disposal Facility within the Airport East/East of Sha Chau Area
Agreement No. CE 12/2002 (EP)
Environmental
Impact Assessment (EIA)
and
Final Site Selection Report
-
Executive Summary -
Background to the Study
Capacity to dispose of
contaminated mud is currently predicted to be exhausted by early 2009 with the
completion of backfilling of the Contaminated Mud Pit (CMP) IV at East of Sha
Chau. These recently revised
predictions have indicated that there has been a reduction in the forecasted
amounts of contaminated mud requiring disposal, primarily as a result of a
decrease in marine dredging operations in Hong Kong. Several factors may still act to affect the arisings of
contaminated mud including:
·
reprioritization
and reprogramming of works projects;
·
increasing
control of land-based contaminant sources; and,
·
continued
implementation of ETWBTCW No. 34/2002.
When CMP IV is full, a replacement
environmentally acceptable disposal facility for arisings of contaminated mud
will be required. A minimum
capacity of 8 Mm3 has been identified to provide disposal capacity
up to 2015. The assignment Strategic Assessment and Site Selection
Study for Contaminated Mud Disposal (Agreement CE 105/98) recommended a
Contained Aquatic Disposal facility (CAD) at Airport East, such as those
already used at East of Sha Chau) at ([1]). The results and recommendations of CE 105/98 were presented to the
Advisory Council on the Environment (ACE) on 23rd
July 2001 (ACE Paper 4/2001).
Although
members of ACE had no objection to proceeding with the recommended EIA, they
considered that all sites; in particular, remaining portions of East of Sha
Chau, and other disposal options, in particular a confined disposal facility
(CDF – material confined within an artificial island) should still be
considered. To meet these
requirements this study identified suitable sites and disposal options at the
South Brothers and East of Sha Chau areas and, secondly it evaluated the
environmental acceptability of impacts associated with their construction and
operation, through an Environmental Impact Assessment (EIA), and thirdly, based
on a comparison of the outcomes of the two EIAs, a preferred disposal facility
was recommended.
This
Executive Summary provides a précis of the Environmental Impact Assessment
and Final Site Selection Report (EIA FSS) and presents the
recommended disposal facility.
Purpose and Scope of the EIA
The Project is
classified as a Designated Project by virtue of Item C (Reclamation, Hydraulic
and Marine Facilities, Dredging and Dumping), Item C.10 (A Marine Dumping Area)
and C.12 (A Dredging Operation Exceeding 500,000 m3) of Part I of
Schedule 2 under the Environmental Impact
Assessment Ordinance (Cap. 499) (EIAO).
In
order to identify the preferred alternative in both the East of Sha Chau and
the Airport East areas a list of potential alternatives was first
compiled. In each area, three
potential sites were identified following a constraint mapping process, and for
each of the total of six sites, two disposal options were considered, CAD and
CDF.
To
assess which alternatives of the twelve alternatives should be taken forward to
the detailed EIA stage, an evaluation of each of the twelve alternatives based
on environmental, engineering and planning considerations has been
conducted. A ranking system was
applied to reflect the degree of suitability or unsuitability of the alternative. The outcome indicates that CAD
facilities located South of the Brothers and adjacent to the existing facility
in East of Sha Chau ranked the highest and were therefore considered to be most
suitable.
A
thorough evaluation of both the South Brothers and East of Sha Chau Facilities
was undertaken to determine the acceptability of predicted impacts to water
quality from dredging, backfilling and capping of the pits and other concurrent
activities. The study will also
contribute to decisions on the overall environmental acceptability of the
Project, after the implementation of environmental mitigation measures.
The
EIA provides a detailed assessment of the potential environmental impacts
associated with the Project, in relation to the issues specified in the EIA Study Brief (No. ESB-095/2001), including water quality, marine
ecology, fisheries, hazard to health, noise and cultural heritage.
Project Description
Location and Scale of the
Project
The
Study Area is located within the waters off the coast of North Lantau (Figure
1.1).
A
preliminary layout for the proposed facility is shown in Figure 1.2,
along with indicative dimensions.
The Project involves the sequential disposal of contaminated mud into a
series of dredged pits (Pits A, B, C and D). The sequential construction and operation of the pits has
been used to develop scenarios for sediment transport modelling, assess marine
traffic issues and identify key environmental issues for water quality,
ecology, fisheries, human health, noise and heritage assessments.
A
preliminary layout for the proposed facility is shown in Figure 1.3,
along with indicative dimensions.
As with the East of Sha Chau Facility, the Project involves the
sequential disposal of contaminated mud into a series of dredged pits (Pits A, and B and C). The sequential construction and
operation of the pits has been used to develop scenarios for sediment transport
modelling, assess marine traffic issues and identify key environmental issues
for the water quality, ecology, fisheries, human health, noise and heritage
assessments.
Construction and Operational
Activities
The works
that are the subject of the EIA Study include the construction and operation
phases of the Project. The key
components of the Project include the following:
1.
Dredging
of a series of seabed pits within either the East of Sha Chau Facility or South
Brothers Boundaries;
2.
Backfilling
each dredged pit with contaminated mud that has been classified as requiring
Type 2 disposal in accordance with ETWBTC 34/2002 ([2]); and,
3.
Capping
each backfilled pit with uncontaminated mud effectively isolating the
contaminated mud from the surrounding marine environment.
Environmental Impacts
Comparison
of Facilities
In
the comparison of facilities it is important to note that under the Strategic Assessment and Site Selection
Study for Contaminated Mud Disposal (Agreement CE 105/98), a detailed
SAR-wide review of potential sites for a new contaminated mud disposal facility
was undertaken. This study
recommended that East of Sha Chau be taken forward as the preferred site.
Although
members of ACE had no objection to proceeding with this site, they considered
that the remaining portions of East of Sha Chau should be reviewed. As such, this study has investigated
the potential of both the South Brothers and East of Sha Chau areas to
accommodate a new contaminated mud disposal facility.
The
purpose of the assessment was to thoroughly evaluate both the South Brothers
and East of Sha Chau Facilities in terms of the acceptability of predicted
impacts to water quality, marine ecology, fisheries, hazard to health, noise
and cultural heritage from dredging, backfilling and capping of the pits, as
well as the residual impacts and those from concurrent activities. Through this assessment, differences in
the potential environmental performance of each facility have become
apparent.
Through
the adoption of currently acceptable dredging, backfilling and capping rates,
the construction and operation of either the East of Sha Chau or the South
Brothers Facilities will not result in exceedances of the Water Quality
Objectives at specific sensitive receivers (Figures 1.4 and 1.5).
A
detailed environmental assessment of both the East of Sha Chau and South
Brothers Facilities has been undertaken to determine their relative suitability
for the development of a contaminated mud disposal facility. The results of this study indicate that
East of Sha Chau area should be used in preference to the South Brothers site
due to less uncertainties related to concurrent projects on the North Lantau
coastline between 2008-2010. The
South Brothers pits may however still be required post 2010, should capacity be
reached earlier than expected at East of Sha Chau or one or more of the East of
Sha Chau pits not being available due to planning constraints. If this is the case then the EIA of the South Brothers shall be
reviewed and assessed for its relevance to ensure that the information contained
in the current study (Agreement No. CE12/2002 (EP))
is not outdated. Following the precautionary principle
and due to the proximity of Tai Ho Bay
and the uncertainties in the final plans for projects on the North Lantau
coastline, operations at South Brothers Pit C should be avoided.
It should be noted that Pit B at South Brothers will only be used if Pit A is
proven to be environmentally acceptable through Environmental
Monitoring and Audit works.
.
Based
on the above, the multi-pit purpose-dredged Contained Aquatic Disposal facility
(CAD) at East of Sha Chau is recommended for detailed design and
implementation.
It is
important to note, however, that in terms of overall impacts, both facilities
are considered to be acceptable on the grounds that both meet the relevant
assessment criteria. Thus, should
the area currently selected for the East of Sha Chau Facility not be available
when required, there are no insurmountable problems associated with proceeding
sequentially with the South Brothers Facility, if considered necessary.
Should
arisings increase beyond the levels in the current forecast, then it may well
be possible to proceed with facilities within both the East of Sha Chau and the
South Brothers Area.
The construction of the first pit at the
East of Sha Chau Facility is expected to be dredged during 2007/2008 in order
to be ready to receive contaminated mud in early 2009. According to the arisings estimates the
last pit at the facility will be backfilled and capped during the first half of
2015. The South Brothers pits may
however still be required post 2010, should capacity be reached earlier than
expected at East of Sha Chau or one or more of the East of Sha Chau pits not
being available due to planning constraints.
Overall Conclusion
This Environmental
Impact Assessment and Final Site Selection Report has critically assessed
the overall acceptability of the environmental impacts likely to arise as a
result of the construction and operation of the proposed contaminated mud
disposal facility at East of Sha Chau.
Where necessary and practicable, the EIA has specified the conditions
and requirements for the detailed design, construction and operation of the
Project in order to mitigate environmental impacts to acceptable levels.
This
EIA Study has predicted that the Project will comply with all environmental
standards and legislation following the implementation of the recommended
mitigation measures. The EIA has
thus demonstrated the acceptability of any residual impacts from the Project
and the protection of the population and environmentally sensitive
resources. Where appropriate,
EM&A mechanisms have been recommended to verify the accuracy of the EIA
predictions to ensure the effectiveness of the recommended mitigation measures.
In conclusion, it is considered that the EIA provides a suitable basis for the
Director of Environmental Protection to consider granting the Environmental
Permit to allow the construction and operation of the Project..
List
of Figure.
Figure 1.1 Location
of the Airport East and East of Sha Chau Study Areas
Figure 1.5 Key
Marine Ecological Habitats within the Assessment Area