1.1.1
The squatter area in the vicinity of the existing Hang Hau
Tsuen stream was cleared in 1997. The poor hydraulic performance of the Hang
Hau Tsuen stream is attributed partly to the siltation of the watercourse by
the remains of the former squatter structures, and also to the meandering
watercourse and the presence of an under-sized box culvert at Deep Bay Road. Rapid
developments in the North West New Territories and conversion of agricultural
land to open storage sites and container yards leading to higher surface runoff
has exacerbated the problem. A total of about 43 hectares of land is flood
prone as a result of the inadequate drainage capacity of the Hang Hau Tsuen
stream. To alleviate flooding in the catchment, the existing Hang Hau Tsuen
stream between Deep Bay and Deep Bay Road will need to be improved to an
engineered channel that will meet the required flood protection standards.
1.1.2
The project proponent, Civil Engineering and Development
Department, will implement the improvement works under PWP Item No. 705CL –
“Hang Hau Tsuen Channel at Lau Fau Shan” (hereafter referred to as “the
Project”).
1.1.3
The Project is a designated project under the Environmental
Impact Assessment Ordinance (EIAO) (Cap.499) by virtue of I.1(b) (vi) of Schedule
2, Part I of the EIAO. The Project will discharge into an area within 300 m
from the nearest boundary of an existing Coastal Protection Area (CPA) land use
zoning.
1.1.4
In accordance with the EIAO, an EIA report is required to be
prepared to meet the requirements of the EIA Study Brief (ESB-167/2007) 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.
2.1
Description of
the Project
2.1.1
The Project is located in Hang Hau Tsuen at Lau Fau Shan,
North West New Territories between Deep Bay Road and Deep Bay. The Project comprises
the construction of the Hang Hau Tsuen Channel and associated works to improve
the local drainage systems in the Hang Hau Tsuen area.
2.1.2
The Project comprises the following works:
(i)
Training of Hang Hau Tsuen stream including construction of a
370 m long drainage channel connecting to the downstream ends of Fung Kong
Tsuen Channel and San Hing Tsuen Channel to Deep Bay.
(ii)
Construction of a 25 m long triple-cell box culvert 5.5 m (w)
x 3 m (H) beneath the Deep Bay Road and 4 nos. of footbridges across the
channel.
(iii)
Provision of a 3.5 m wide access road with passing bays along
the northern bank of the channel, 3.5 m maintenance access road along the
southern bank of the channel and 2.0 m wide footpath on both sides of the
channel and ancillary works such as retaining walls, drainage and water works
as well as associated landscaping works.
2.1.3
As requested by a Yuen Long District Council member, a
viewing point and carpark will be provided at the downstream end of the
proposed channel to allow visitors to enjoy the scenery of Deep Bay.
2.1.4
Details of the Project are shown in Figure 1.
2.2.1
The proposed alignment generally follows the alignment of
existing stream course to minimize resumption of existing village houses hence
minimizing disturbance to the public.
2.2.2 Environmental benefits and dis-benefits of various alternative drainage design options along with various other constraints were carefully evaluated before deriving the proposed design.
2.2.3 The concepts of ‘avoidance’ and ‘minimisation’ have been incorporated into the design to protect the stream bed where established mangrove stands and intertidal mudflat communities can be found. The stream bed for the downstream portion of the channel has been largely retained in-situ. A small portion of the mangroves will inevitably need to be removed. Other environmental friendly design includes the use of natural substrates as channel bed material which will encourage accumulation of sediments and eventually re-colonisation of the channel bed by benthic community as well as re-establishment of vegetation.
2.3
Justifications
and Benefits of the Project
2.3.1
The proposed Project is expected to contribute to the relief
of the present drainage problems that have led to severe flooding in the study
area resulting in danger to life, economic loss and disruption to everyday
life.
2.3.2
The current standard of protection of the Hang Hau Tsuen
stream is very low. Upon completion of the Project, the standard of protection
will be increased to 1 in 50 years for village development.
2.3.3
The villagers of Hang Hau Tsuen at Lau Fau Shan will be directly
benefited by the proposed Project.
2.4
Continuous Public
Involvement
2.4.1
Public consultation with the Green Groups, Ha Tsuen Rural Committee,
Yuen Long District Council and oyster farmers association of Lau Fau Shan were
undertaken during the course of the EIA study. Overall, there were no
objections to the final design of the Project.
2.5.1
The construction programme of the Project will likely commence
in end 2009 for completion by end 2012.
3.1.1
Construction
activities for the Project involve site clearance in the works areas,
excavation to formation levels of the channel, construction of channel
structures / linings and ancillary structures, and landscaping works. Small scale
routine maintenance would be necessary during the operation of the proposed
channel to remove excessive silts, vegetation, debris and obstructions in order
to maintain its hydraulic performance and structural integrity. The proposed viewing point and carpark would likely
introduce road traffic along the access road. All these activities have the potential to impact on the existing
environment.
3.1.2
The key
environmental issues assessed in the EIA Report are:
·
Air
Quality;
·
Noise;
·
Water
Quality;
·
Waste
Management;
·
Ecological
Impact;
·
Fisheries
Impact; and
·
Landscape
and Visual.
3.2.1
The construction dust impact
assessment has identified Air Sensitive Receivers
(ASR) within the Study Area. Potential works that may cause potential
construction dust nuisance is also identified. Mitigation measures, as required
by Air Pollution Control (Construction Dust) Regulation, are also highlighted.
With the implementation of the recommended mitigation measures, residual
construction dust impact at nearby air sensitive receivers is expected to
comply with the Air Quality Objectives and EIAO-TM.
3.2.2
Air
quality monitoring is recommended at selected air sensitive receivers during
the construction period to check for compliance with the permissible dust
levels and effectiveness of the proposed mitigation measures.
3.2.3 During the operation phase of the Project, given the low volume of vehicles expected to use the access road, vehicular emission impact from the proposed access road upon the nearby air sensitive receivers is not expected. Maintenance of the channel is also unlikely to cause any adverse impact during operational phase.
3.3.1
The
use of powered mechanical equipment during the construction phase of the Project
is expected to create noise nuisance, due to the close proximity between the
works areas and noise sensitive receivers. Assessment indicates that such noise
impact can be mitigated to acceptable levels by appropriate measures, including
the use of quiet plant, temporary noise barriers, restricting concurrent usage
of equipment 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, residual noise impact would not be expected from
the construction works and will comply with the EIAO-TM daytime construction
noise standard.
3.3.2
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.
3.3.3
The
operation phase of the Project, in terms of road traffic noise and during
maintenance of the channel, is not expected to pose any noise impact to the
surrounding area.
3.4.1 The current condition of the Hang Hau Tsuen stream and Deep Bay in the Study Area is relatively poor as these waterbodies receive a variety of polluting inputs including domestic wastewater from unsewered villages and effluent from open storage sites and container yards.
3.4.2 The construction of the channel could adversely impact the water bodies through silt-laden site runoff, disturbance of stream sediment during excavation, concreting works, runoff from workshops & depot and increased sewage and wastewater resulting from the additional workforce on site. These impacts can be readily mitigated through the construction of a suitable drainage system with silt traps, good site management practices, careful working practices during excavation of the stream and proper sewage collection and disposal system. With the implementation of these measures, no adverse residual water quality impact from construction work is expected.
3.4.3 The Project will not generate any new pollution loading to Deep Bay. Provision of catchpits with sand traps will remove some of the pollutants from the surface runoff at Hang Hau Tsuen before being discharged into Deep Bay. The impact can be further mitigated through the incorporation of vegetated areas into the drainage channel design. The re-established vegetation can act as a natural pollutant trap and filter. The proposed channel will require regular maintenance to ensure effective functioning and prevent the unacceptable built-up of sediments. The routine maintenance of the channel may pose potential impacts if it is not properly executed. By following the recommended good practice guides during maintenance works, no adverse impacts are expected.
3.4.4 The provision of the access road, viewing point and carpark would have minimal impact during operation with the incorporation of gullies and silt / grit traps in the road drainage design.
3.4.5
Water
quality monitoring is recommended during the construction period to check for
compliance with permissible water quality limit levels and effectiveness of the
proposed mitigation measures.
3.4.6 Overall, the residual water quality impacts during construction and operation phases of the Project are considered acceptable with respect to the EIAO-TM and Water Pollution Control Ordinance.
3.5.1 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, 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.
3.5.2 Potential for reuse of inert construction & demolition material (public fill) within the Project will be rigorously explored throughout the course of the Project in an effort to minimise off-site disposal.
3.5.3 A small quantity of contaminated stream sediment will be excavated and need to be disposed offsite in designated marine disposal sites. Potential for reuse of uncontaminated sediment as channel bed material will be maximized as far as practicable. Provided that there is strict control of construction and demolition materials generated from construction works and that all sediments generated 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 would be necessary to ensure the implementation of proper waste management practices during construction.
3.5.4 Waste generated during operation and maintenance of the Project is expected to be minimal. Proper waste management practices have been recommended.
3.5.5 Overall, the residual waste impacts of the Project are considered acceptable with respect to the EIAO-TM and Waste Disposal Ordinance.
3.6.1
The Project has avoided and minimised
much of the environmental and ecological impacts by adopting the preferred
option. The habitats to be lost would be small in size and not of high
ecological value. Compensatory landscape tree planting consisting mostly of
native species and compensatory mangrove planting will be provided to mitigate
the loss. Ecological monitoring is proposed to monitor the survival and growth
of the mangrove planting during operation phase.
3.6.2
With the implementation of the recommended mitigation
measures, the ecological impacts resulting from the proposed works during
construction and operation phases are considered to be acceptable.
3.7.1
Literature review and field
visits have 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. The Project
would affect a small area of an abandoned fishpond. Potential impacts on capture fisheries,
oyster farming and pond culture in Lau Fau Shan and Inner Deep Bay are considered
insignificant. No mitigation is required and the residual impact is
acceptable. Other than the water
quality monitoring programme, no specific fisheries EM&A programme would be
required.
3.8
Landscape and
Visual Impact
3.8.1 The landscape and visual impact assessment indicated that moderate to slight adverse impact will occur during the construction stage and moderate to slight beneficial impact during operational stage. The landscape mitigation measure will minimize the adverse impact of the disturbance to existing trees from moderate adverse to moderate beneficial in the long term. Adverse visual impact, which is in a local context, will be minimized with the incorporation of mitigation measures.
3.8.2
The
Project would result in the loss of 16 nos. of trees. Compensatory tree planting
will comprise about 114 nos.
of native trees in attempt to restore the loss of greenery and to enhance the
overall landscape quality. In addition, native shrub species will be planted.
3.8.3
Apart
from the slight adverse impact on the elimination of small portion of
residential area and fishpond within the site area, it is predicted that the
proposed Project will have negligible adverse landscape impact and moderate
beneficial visual impacts during the operation stage. In conclusion, the landscape
and visual impacts in the construction and operation phases will be “acceptable
with mitigation measures”.
4.
ENVIRONMENTAL
MONITORING AND AUDIT
4.1.1
Mitigation
measures have been recommended in the EIA Report to mitigate potential adverse
impacts from the construction and operation phases of the Project. Based on
these recommendations, Environmental Monitoring and Audit (EM&A)
requirements have been established.
4.1.2
An EM&A
programme will be setup 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.
4.1.3
To ensure that the environmental performance of the works
meets all relevant legal and contractual requirements, the Contractor will be
required to prepare and implement an Environmental Management Plan, which
details the approach that Contractor is to adopt in managing and controlling
potential environmental impact from construction activities for this Project.
5.1.1
The main objective of the Project is to alleviate the
potential flooding problems in Hang Hau Tsuen at Lau Fau Shan.
5.1.2
Based on the findings of the EIA Study, the Project would not
cause any adverse environmental impacts to the concerned Coastal Protection
Area, the ecology of Deep Bay and other sensitive receivers in the Study Area.
The residual construction phase and operation phase impacts are considered
acceptable with respect to EIAO-TM and relevant ordinance requirements.
5.1.3
Overall this EIA concludes that
there are no unacceptable environmental impacts associated with the
construction and operation 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.
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