TABLE OF CONTENTS
12 SUMMARY OF KEY ENVIRONMENTAL OUTCOMES.
12-1
12.1
Environmentally Friendly Design and Benefits of the
Project 12-1
12
SUMMARY OF KEY ENVIRONMENTAL OUTCOMES
12.1
Environmentally Friendly Design and Benefits of the
Project
12.1.1 Environmental
considerations were taken into account in the selection of preferred option,
design and construction method of the Project as detailed in Section 2.
The following environmental friendly designs and benefits have been
incorporated into the Project:
Provision of Eco-shoreline
12.1.2 The
design for the expansion of Aberdeen Typhoon Shelter (ATS) will thoughtfully
incorporate eco-shoreline features, including eco-tiles, tidal pools and
seabird perch, of spanning about 570 m along the proposed breakwaters, land
access and vessel impact protection system (VIPS). These elements aim to
enhance biodiversity, improve ecological performance, and strengthen coastal
protection, ensuring that the development aligns with principles of
environmental sustainability and educational enrichment.
12.1.3 The
subtidal portion of the proposed and modified breakwaters will create
approximately 4.55 ha of artificial hard substrates, which could facilitate the
colonisation of corals and other epibenthos. Additionally, the
construction of the proposed land access connecting to the proposed eastern
breakwater will create approximately 0.2 ha of artificial subtidal hard bottom
habitat. Approximately 1,380 m of artificial intertidal habitat will
be created through the construction of the proposed breakwaters as well as the
proposed land access connecting to the proposed eastern breakwater. Artificial
habitats created by the Project is summarised in Table 7.22.
Preservation
and Promotion of Sea Caves at Coastal Protection Area
12.1.4 There
are sea caves along the Coastal Protection Area (CPA) at Tai Shue Wan and Ap
Lei Pai, which serve as geological archives that provide valuable insights into
coastal erosion and weathering processes. Thus, the alignment of the proposed
land access has been designed to follow the rocky shoreline outside the CPA,
allowing visitors to appreciate the area’s natural geological features,
including sea caves. Currently, access to these sea caves is limited to marine
transportation or kayaking, which restricts public accessibility. The Project
will provide convenient access to the sea caves via the proposed land access,
enabling the public to enjoy a closer view of the natural landscape and
geological features such as sea caves for both leisure and educational
purposes.
Beneficial
Use of Unwanted Materials Generated By Other Projects
12.1.5 The
construction and demolition (C&D) materials generated from the Project,
including those arising from the demolition of part of the existing
breakwaters, will be reused on-site whenever feasible. These materials will
primarily serve as rock fill for the proposed structures, such as the
foundation for the VIPS and landfall of proposed breakwaters. Moreover,
substantial infill material is still needed for the breakwaters. To address
this need, C&D materials generated by other local projects and accumulated
in CEDD’s Public Fill Reception Facilities (PFRFs) would also be used for the
Project as infill materials. This approach will not only facilitate the
beneficial use of a significant quantity of unwanted materials but also
minimise the need to import raw material.
Proposed Wave Wall in the Form of Floating
Breakwater
12.1.6 The
original location of the proposed wave wall is on the top of the tombolo with
the primary objective to attenuate the waves on the west side of the expanded
area of ATS through the existing tombolo. This tombolo, formed by natural
process, connects Yuk Kwai Shan and Ap Lei Pai, creating an eye-catching
geomorphic feature. To preserve the natural scenery, the wave wall in the form
of floating breakwater was proposed to be relocated offshore by about 70 m
eastward within the Project site which could provide the same wave attenuation
performance while minimising the impact on the tombolo. The Benefits of
adopting floating breakwater type wave wall are summarised in the table below.
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Description
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Benefits
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· Consist of precast floating
pontoons and concrete sinkers
· Placement of concrete sinkers on
seabed without seabed stabilisation required
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· Preserve the tombolo located
between Ap Lei Pai and Yuk Kwai Shan
· Avoid disturbing the seabed, as it
eliminates the requirement of seabed stabilisation by methods like dredging
and filling or deep cement mixing (DCM)
· Minimise the potential impacts on
water quality and water flow from construction
· Reduce visible footprint
significantly due to its low freeboard of about 0.6 m during both high tide
and low tide comparing with traditional sloping or caisson breakwater that
would have a greater freeboard of about 5 m during low tide, minimising the
visual impact
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Proposed Land
Access Layout and Location
12.1.7 To
minimise the impact to the existing shoreline of Tai Shue Wan, particularly the
existing sea caves, which falls within the CPA, the proposed land access
connecting to the proposed eastern breakwater and Tai Shue Wan promenade is to
be constructed offshore with shallow foundation.
Proposed Shortening of Existing
Western Breakwater
12.1.8 Various
options of demolition including full demolition and partial demolition are reviewed and analysed. To resume the footprint of
the existing breakwater for mooring purpose, it is required to demolish the
breakwater structure as well as dredging at the seabed as deep as -10 mPD to
-15 mPD to remove all hard materials. As the additional mooring space
that could be provided by full demolition option is minimal, it is proposed to
maintain the major part of the existing western breakwater in-situ by
shortening of part of the breakwater of approximate 70 m and removing the
breakwater structure down to -5 mPD without dredging works at seabed, which
could straighten the passageway for marine vessels to
navigate to/ from the existing Aberdeen South Typhoon Shelter with sufficient
water depth. This approach aims to avoid disturbing the seabed,
thus minimising potential water quality impacts from the modification and to
minimise generation of C&D materials while
maintaining adequate water depth for vessel navigation.
Proposed Eastern and Western
Breakwaters Alternative Structure Form
12.1.9 It
was recommended to adopt vertical type caisson breakwaters as the main
structural form while sloping rubble mound is adopted at the breakwater
landfalls. Vertical type caisson breakwater would require a smaller footprint
and thus reduce the scope of seabed stabilisation as well as disturbance to the
seabed, and together prefabrication of breakwater components off-site, have
less impact on water quality, marine ecology and landscape. Furthermore, the
construction time could be significantly reduced with the use of pre-fabricated
units.
Adoption of Shallow Foundation for
the Proposed Land Access
12.1.10 The existing shallow rockhead along
the proposed alignment of land access presents a favourable opportunity for the
adoption of shallow foundation. Moreover, as the proposed land access will be
located within the sheltered area with less wave loading, use of shallow
foundation could provide the required structural loading capacity. This
type of foundation eliminates the need for extensive pilling works for
construction, effectively reducing the disturbance to the seabed and marine
ecosystem.
Construction Method for Breakwaters
Foundation
12.1.11 In view of numerous environmental
issues resulted from dredged method, e.g. water quality problem and dispersion
of contaminant, DCM is adopted to avoid dredging works. DCM enhances the
stability of the seabed and foundation for breakwater structures and hence
reduce the risk of erosion and collapse over time. The enhanced stability and
durability can contribute to the long-term protection of the coastal areas and
reduce the need for frequent maintenance or reconstruction, which in turn
decreases the overall environmental footprint of the Project.
Low-Carbon Design for Construction
12.1.12 Green construction technologies, including low-carbon
concrete and Glass Fibre Reinforced Polymer reinforcement, will be adopted
where feasible to reduce the overall carbon emission from the production of
conventional concrete and steel reinforcement.
Construction Method for Main
Structures
12.1.13 To further reduce the impacts on
air, noise and water quality, the proposed breakwaters and floating breakwaters
will be constructed with prefabricated units whenever practical. The units will
be manufactured off-site in a controlled environment, thereby eliminating the
need for on-site casting and curing of concrete. This approach may
significantly reduce the duration and intensity of on-site construction
activities, leading to a shorter construction period. Consequently, the
potential for particulate matter generations, construction noise, and water
pollution, such as runoff and sedimentation, will be minimised.
Consideration of Construction
Sequence
12.1.14 Given that the construction of the
proposed breakwaters, involving seabed stabilisation works and caisson unit
installation, has the longest duration compared to the proposed wave wall in
the form of floating breakwater and proposed land access, these breakwaters
works will commence first. The other works, such as proposed land access
and proposed wave wall in the form of floating breakwater, can then proceed in
parallel with the proposed breakwaters construction. This approach
optimises the Project timeline by addressing the most time intensives works
upfront.
12.1.15 To shorten the constriction period
for the breakwaters, multiple work-fronts will be considered to allow different
work activities to proceed in parallel. It is assumed that two work-fronts
comprising sand blanket and geo-textile laying plants along with DCM plants
will be deployed at the same time across various locations. Concurrent
stabilisation of multiple seabed sections accelerates the overall construction
and shortens the duration of potential environmental impacts, thereby enhancing
the Project’s environmental performance.
Consideration of Integration of Tai Shue Wan
Public Pier to Proposed Eastern Breakwater
12.1.16 It was originally proposed to
provide two piers at Tai Shue Wan and Deep Water Bay under separate
project. Upon review by the Government, it is decided to integrate the
function of the proposed Tai Shue Wan pier, taking the form of landing steps with
ramps, into the proposed eastern breakwater under the Project, so as to create
synergy while saving overall costs.
12.1.17 The proposed public landing facility
would adopt the structural form of a multiple landing steps with ramps,
embedded into the vertical face of the eastern breakwater near the
landfall. Fenders would be installed at the berthing face to protect
breakwater structure. Typical marine facilities for public landing steps
such as bollards, handrailing, marine notice board, etc. would also be provided
to serve the intended pier function.
12.1.18 This integration will also enhance
efficient utilisation of marine space for mooring and navigation purposes. The
integration also averted the necessity for an extra concurrent project, thereby
alleviating the additional environmental impacts that would arise from the
construction of a separate pier at Tai Shue Wan, such as seabed disturbance and noise generation.