11.1.1
The project is entitled “Improvement of Fresh Water Supply to
Cheung Chau” (hereinafter referred to as “the Project”).
11.1.2
Cheung Chau, with a population of around 23,000, is currently
supplied with treated water from Silver Mine Bay Water Treatment Works on
Lantau via two submarine water mains, 10” (about 250 mm) and 500 mm in
diameter, across Adamasta Channel. Treated water is normally provided by the
500 mm diameter main, with the 10” main serving as emergency backup.
11.1.3
Laid in 1963, the existing 10”
submarine water main providing partial emergency back up fresh water supply to
Cheung Chau is approaching the end of its design life of 50 years. Repairs would be uneconomical and take a long
time given the difficulty of the task and the condition of the main. To improve
the reliability of water supply to Cheung Chau, it is necessary to strengthen
the emergency back up by replacing the existing 10” submarine water main with a
new 500 mm diameter submarine water main.
11.1.4
The Project is to
construct and operate a new submarine water main across Adamasta Channel from
Lantau to Cheung Chau to replace the existing submarine water main, which is
serving as emergency back up, to improve the reliability of water supply to
Cheung Chau.
11.1.5
The Project is a designated project under Item Q.1, Part I,
Schedule 2 of the Environmental Impact Assessment (EIA) Ordinance (EIAO) (Cap.
499) as part of the works will be carried out within the
11.1.6
In accordance with the EIAO, an EIA report is required to be prepared
to meet the requirements of the EIA study brief (ESB-187/2008) and the
Technical Memorandum on EIA Process (EIAO-TM). An Environmental Permit will
need to be obtained for the construction and operation of the Project under the
EIAO.
11.2
Location and
Description of the Project
11.2.1
The Project is located in the southeastern coast of Chi Ma
Wan Peninsula at South Lantau, in the northwestern coast of
11.2.2
The Project is to
construct and operate a new submarine water main across Adamasta Channel from
Lantau to Cheung Chau to replace the existing 10” submarine water main, which
is serving as emergency back up, to improve the reliability of water supply to
Cheung Chau. The Project will comprise the following:
(i)
Laying
of a submarine water main of approximately 1,400 m in length and 500 mm in
diameter across Adamasta Channel;
(ii)
Construction
of landfall and associated works within
(iii)
Construction of landfall and associated
works near Tai Kwai Wan, Cheung Chau.
11.3.1
A number of options for improving the adequacy and
reliability of water supply to Cheung Chau have been investigated and
evaluated. Current evaluation indicates a single 500mm diameter polyethylene
(PE) pipe within a steel casing installed by Horizontal Directional Drilling
(HDD) technique as the recommended option for the alignment across Adamasta
Channel. After making landfall, the land-based water main (500mm diameter
ductile iron (DI) pipe) will be laid underground using conventional open cut
method.
11.3.2
Environmental benefits and dis-benefits of various
alternative water main design, alignment, landfall location and construction method
along with various other constraints were carefully evaluated before deriving
the recommended option.
11.3.3
The concepts of “avoidance” and “minimization” have been
considered in the design to avoid marine works activities and disturbing the
seabed with a view to reduce water quality, ecological and fisheries impacts.
The works area at Cheung Chau has been fine-tuned to avoid encroachment or
disturbance to the rocky shore habitat, Coastal Protection Area as well as
retaining as much trees as possible. In addition, works at the Lantau landfall
has been minimized as far as possible to reduce potential impact on
11.4
Justifications
and Benefits of the Project
11.4.1
With the existing 10” submarine main in service for over 46
years and approaching the end of its service life, repairs would be
uneconomical and take a long time given the difficulty of the task and the
condition of the main. Moreover, the supply through this 10” submarine main
alone can only partially meet the demand of Cheung Chau for treated water. To
improve the reliability of water supply to Cheung Chau, it is necessary to
strengthen the emergency back-up by replacing the existing 10” submarine water
main with a new 500 mm diameter submarine water main.
11.4.2
The proposed Project will provide a secure and reliable water
supply to Cheung Chau. All the residents of Cheung Chau as well as tourists
visiting Cheung Chau will be directly benefited by the proposed Project.
11.5.1
The
construction activities for the HDD works involve site clearance and site
preparation in the works area, drilling within bedrock layer across Adamasta
Channel, pipe installation / connection and site reinstatement. The
construction activities for the land-based water main laying works involve
surface breaking, excavation, laying of pipe, backfilling and surface
reinstatement. Majority of the construction works will occur in Cheung Chau.
All these activities have the potential to impact on the existing environment.
11.5.2
The key
environmental issues assessed in the EIA study are:
·
Water
Quality;
·
Ecological
Impact;
·
Fisheries
Impact;
·
Cultural
Heritage Impact;
·
Construction
Waste Management; and
·
Construction
Noise.
11.5.3
Mitigation
measures have been recommended in the EIA report to mitigate potential adverse
impacts from the construction of the Project.
11.6.1 With the use of HDD technique in laying the submarine water main, there will be no marine works and no impact to the seabed. The preferred construction option of using HDD will significantly reduce potential water quality impacts to the sensitive receivers within the marine waters of the Southern Water Control Zone.
11.6.2 The construction works could impact the water bodies through silt-laden site runoff, inadvertent release of drilling fluids, runoff from workshops & depot, sewage effluent from the construction workforce and discharge of chlorinated water during sterilization of the water main. These impacts can be readily mitigated by provision of suitable temporary site drainage systems with treatment facilities, installation of drilling fluid recycling and treatment systems, implementation of the recommended good site management practices and proper sewage collection and disposal systems.
11.6.3 Water quality monitoring is recommended during the construction phase to check for compliance with permissible water quality limit levels and effectiveness of the proposed mitigation measures.
11.6.4
With the implementation of the recommended mitigation
measures, no adverse residual water quality impact is expected during
construction phase of the Project. Overall, the residual water quality impact
is considered acceptable with respect to the EIAO-TM and Water Pollution
Control Ordinance.
11.7.1
The Project has avoided and
minimized much of the ecological impacts by adopting the HDD construction
method in laying submarine water main. Works at Lantau has been minimized to
avoid impacts to
11.7.2
Ecological resources recorded
within the
11.7.3
The Project would only affect
small sizes of a few low value habitats including rocky shore, plantation and
developed areas. The overall ecological
impact is ranked as minor and the residual impact is considered acceptable with
respect to EIAO-TM.
11.7.4
Besides good site practices, no
other major mitigation measures for ecology is required. With the regular site
inspection performed by the Environmental Team, no specific ecological
monitoring programme is needed.
11.8.1
Literature
review has been conducted to establish the fisheries baseline condition of the
assessment area and assessment of potential impacts conducted in accordance
with the EIAO-TM requirements. With the
use of HDD technique in laying the submarine water main, there will be no
marine works and no impact to the seabed. The Project would not affect
fisheries resources and fishing activities significantly.
11.8.2
Potential
indirect water quality impacts from site runoff and wastewater discharge on
capture fisheries, fish spawning and nursery grounds and mariculture in the
11.9.1
The
findings of the Terrestrial Archaeological Investigation and Marine Archaeological
Investigation indicate that the Study Area of the proposed water main has no
archaeological potential, and no impacts on archaeological deposits are
expected. There is no need for any further investigation or mitigation
measures.
11.10
Construction
Waste Management
11.10.1 Construction and demolition materials will inevitably be produced during the construction phase of the Project. Waste generated during construction works includes site clearance / demolition materials, excavated materials, used bentonite, chemical waste and general works waste. Waste types, quantities and timing have been estimated as far as possible and mitigation measures have been proposed in terms of avoidance-minimisation-reuse-recycling-disposal hierarchy.
11.10.2 Potential for reuse of inert construction and demolition material (public fill) within the Project (or within Cheung Chau) will be explored throughout the course of the Project in an effort to minimise off-site disposal.
11.10.3 Provided that there is strict control of construction and demolition materials generated from the construction works and that all arisings are stored, handled, transported and disposed of in accordance with the recommended mitigation measures, potential impact is not expected. The recommended mitigation measures can be enforced by incorporating them into the waste management requirements as part of the Environmental Management Plan. Environmental audit will be necessary to ensure the implementation of proper waste management practices during construction.
11.10.4 Overall, the residual waste impacts of the Project are considered acceptable with respect to the EIAO-TM and Waste Disposal Ordinance.
11.11
Construction
Noise Impact
11.11.1
The use of powered mechanical equipment during the
construction phase of the Project is expected to create noise nuisance, due to
the close proximity of the works areas and noise sensitive receivers.
Assessment indicates that such noise impacts can be mitigated to acceptable
levels by appropriate measures, including the use of quiet plant, temporary noise
barriers and the implementation of good site practices. The Contractor will be
required to implement these measures when powered mechanical equipment is used
during the construction phase. With these measures in place, no residual noise impact is expected from the
construction works and it will comply with the EIAO-TM daytime construction
noise standard.
11.11.2
Noise monitoring is recommended at selected noise sensitive
receivers during the construction period to check for compliance with permissible
noise standards and effectiveness of the proposed mitigation measures.
11.12
Environmental
Monitoring and Audit (EM&A)
11.12.1
Mitigation
measures have been recommended in the EIA report to mitigate potential adverse
impacts from the construction of the Project. Based on these recommendations,
Environmental Monitoring and Audit (EM&A) requirements have been
established.
11.12.2
An EM&A programme will be set up and implemented to
ensure compliance with the mitigation measures recommended in the EIA report,
to assess the effectiveness of the recommended mitigation measures, and to
identify any further need for additional mitigation measures or remedial
measures.
11.12.3
To ensure that the environmental performance of the works
meet all relevant legal and contractual requirements, the Contractor will be
required to prepare and implement an Environmental Management Plan, which
details the approach the Contractor is to adopt in managing and controlling
potential environmental impact from construction activities for this Project.
11.12.4
Impacts on water quality and noise will be monitored and
audited during construction phase. Impacts on the waste management and ecology
during construction will be audited through site inspection.
11.12.5
Details of the EM&A requirements will be stipulated in a separate
EM&A Manual.
11.13.1
The main objective of the Project is to provide a secure and
reliable water supply to Cheung Chau by constructing a new submarine water main
across Adamasta Channel from Lantau to Cheung Chau.
11.13.2
Based on the findings of the EIA Study, the Project would not
cause any adverse environmental impacts to the concerned
11.13.3
Overall this EIA concludes that
there are no unacceptable environmental impacts associated with the
construction of the Project provided that all the legislation, guidelines and
recommended mitigation measures are followed. The EIA has fully met the
requirements of the Technical Memorandum on EIA Process and the EIA Study
Brief.
END OF TEXT