TABLE OF CONTENTS
1. introduction.. 1
1.1 Project
Background. 1
2. Project Description.. 2
2.1 Location
and Description of the Project 2
2.2 Need
for the Project 3
2.3 Consideration
of Alternative Construction Methods and Sequences of Work. 3
2.4 Construction
Programme. 4
3. Summary of Environmental Impact Assessment Findings.. 5
3.1 Air
Quality. 5
3.2 Noise. 5
3.3 Ecology. 5
3.4 Water
Quality. 6
3.5 Waste
Management 7
3.6 Land
Contamination. 7
3.7 Landscape
& Visual 7
3.8 Cultural
Heritage. 8
4. Summary
of Environmental Outcome. 9
4.1 Estimated
Population Protected from Various Environmental Impacts. 9
4.2 Environmentally
Sensitive Areas and Species with Conservation Concern Protected 9
4.3 Key
Environmental Problems Avoided. 9
4.4 Environmental
Benefits of the Environmental Protection Measures Recommended. 9
5. ENVIRONMENTAL
MONITORING AND AUDIT REQUIREMENT. 11
6. Conclusion.. 12
List of
Figures
Figure 1.1 Site
Location Plan
Figure 1.2 Proposed
Drainage Works at Sung Shan new Village
Figure 1.3 Proposed
Drainage Improvement Works at Tai Wo
Figure 1.4A Proposed
Drainage Improvement Works at Lin Fa Tei (Sheet 1 of 2)
Figure 1.4B Proposed
Drainage Improvement Works at Lin Fa Tei (Sheet 2 of 2)
Figure 1.5A Proposed
Drainage Improvement Works at Ha Che (Sheet 1 of 2)
Figure 1.5B Proposed
Drainage Improvement Works at Ha Che (Sheet 2 of 2)
1.1.1
The
Drainage Master Plan Studies for the Yuen Long, Kam Tin, Ngau Tam Mei and Tin
Shui Wai Drainage Basin (YLDMP) were completed in 1998. The majority of the
improvement works in Yuen Long and Kam Tin recommended under the YLDMP Study
have been completed. Since completion of the DMP Studies, there were changes in
developments within the areas and new development proposals and town planning
studies were commissioned. In addition, some new flooding complaints were
received at the upstream areas of the drainage basins, indicating that further
improvement to the drainage systems was required.
1.1.2
Drainage
Services Department (DSD) commissioned the “Review of Drainage Master Plans in
Yuen Long and North Districts – Feasibility Study” (DMP Review Study) in 2008 so that the new development
scenarios could be incorporated and the effectiveness of the previously
recommended works could also be assessed. The DMP Review Study completed in end
2011 identified that some areas in Yuen Long District could not meet the
required flood protection level according to the latest land use changes and
future developments taking into account various factors, including
sedimentation at the downstream main channels, mangrove growth at river
estuaries, updated extreme sea level statistics at Tsim Bei Tsui and projected
Climate Change impacts, in the hydraulic analysis. To account for the severity
and extent of possible flooding and the works implementation time, the DMP
Review Study proposed drainage improvement works in Yuen Long District.
1.1.3
Atkins
China Ltd (ACL) was commissioned by DSD in November 2013 to undertake an
Investigation, Design and Construction Consultancy entitled “Agreement No. CE
22/2013 (DS) Drainage Improvement Works in Yuen Long, Stage 1 – Investigation,
Design and Construction” (hereinafter called the Assignment). The Project
comprises construction of drainage improvement works to four villages (namely
Sung Shan New Village, Tai Wo, Lin Fa Tei and Ha Che) including landscaping,
waterscaping, utilities diversion, temporary traffic arrangements and any other
works incidental to the completion of the Project.
1.1.4
An Environmental
Impact Assessment (EIA) Study Brief (ESB-279/2014) for four villages namely Ha
Che, Tai Wo, Lin Fa Tei and Sung Shan New Village which is a designated project
was issued by the Environmental Protection Department (EPD) on 14 October 2014.
According to the Study Brief, an Executive Summary is required for these four
villages.
2.1.1
The
works of this project includes investigation, design and construction of
drainage improvement works to four villages: Sung Shan New Village, Tai Wo, Lin
Fa Tei and Ha Che, including landscaping, waterscaping, utilities diversion,
temporary traffic arrangements and any other works incidental works.
2.1.2
The site
location plan is shown in Figure 1.1 and the site specific works
for the four villages are described below and shown in Figures 1.2,
1.3,
1.4A,
1.4B,
1.5A
and 1.5B.
Sung
Shan New Village
2.1.3
It is proposed
to carry out the upgrading works along 610m of the existing stream. The cross
section of the proposed rectangular channel with width ranging from 7.5m to 8.0m varies in
height (3m to 5m) along the stream to
suit the existing site constraints by optimizing the hydraulic capacity but
minimizing the land resumptions. Pedestrian crossings will be re-provided along
the proposed works. The proposed works at Sung Shan New Village are shown in Figure 1.2.
Tai Wo
2.1.4
It
is proposed to provide a 290m long of rectangular channel with 1m wide of
various height at Tai Wo to suit
the existing site constraints by optimizing the hydraulic capacity but
minimizing the land resumptions and discharging to the existing channel at the west. The proposed
channel height is ranging from 1.5m to 3.1m. The proposed works at Tai Wo are shown in Figure 1.3.
Lin Fa
Tei
2.1.5
A
150m long and 2m wide rectangular channel of height of approximately 1.7m is
proposed to intercept part of the surface runoff from the hillside and connect
to the upstream of Shui Tsan Tin stream which will then be upgraded to a
proposed rectangular channel with width ranging from 2.4m to 4.8m wide with
total length of approximately 780m along the original alignment to suit the existing site constraints by
optimizing the hydraulic capacity but minimizing the land resumptions. The proposed channel height at the
south of Lin Fa Tei is approximately 3.7m. The 240m long 2m wide rectangular channel
of various height downstream of Lin Fa Tei channel is proposed to be deepened
along original alignment. Part of the flow will be diverted to the proposed
1650mm dia. storm drain underneath Kam Sheung Road. Pedestrian and vehicular
crossings will be re-provided along the proposed works. The proposed works at Lin Fa Tei are shown in
Figures
1.4A and 1.4B.
Ha Che
2.1.6
Approximately
600m of the existing stream is proposed to be upgraded to a rectangular channel
of various width and depth along the original alignment to suit the existing
site constraints by optimizing the hydraulic capacity but minimizing the land
resumptions. The proposed channel width is ranging from 3m to 6.5m, while the
proposed channel height is ranging from 1.8m to 3.1m. For the bottleneck at Fan
Kam Road, it will be improved by additional twin 1500mm dia. drains located to
the south of the existing twin 1500mm dia. drains. A portion of stream of about
170m long (adjacent to Fu Hing Garden) will be upgraded to 3.5 to 4.5m wide
rectangular channel of various height. Pedestrian and vehicular crossings will
be re-provided along the proposed works. The proposed works at Ha Che
are shown in Figure 1.5A and 1.5B.
2.2
Need for the
Project
2.2.1
Currently,
the four villages are susceptible to flooding in the existing drainage system.
Under the “Review of Drainage Master Plans in Yuen Long and North Districts –
Feasibility Study” (DMP Review Study) commissioned by DSD in 2008, it
was identified that some areas in Yuen Long District could not meet the
required flood protection level according to the latest land use changes and
future developments. This includes taking into account of various factors,
including sedimentation at the downstream main channels, mangrove growth at
river estuaries, updated extreme sea level statistics at Tsim Bei Tsui and projected
Climate Change impacts in the hydraulic analysis. To account for the severity
and extent of possible flooding, the DMP Review Study proposed drainage
improvement works in the Yuen Long District. DSD carried out a further review
on the proposed works under the Project and it was considered feasible to
improve the existing drainage condition for the four villages in Yuen Long. The
proposed drainage improvement works aims to alleviate the flooding spots in the
villages.
2.2.2
In
addition to improving the flood situation in the villages, the proposed
landscaping works of the channels will revitalize the channels in terms of
visual and landscape treatment for public enjoyment and blending into the
environment.
Proposed
Underground Drainage Pipes
2.3.1
The
proposed works for underground drainage pipes would be implemented by open cut
method as far as practicable, due to its cost effectiveness in the improvement
in proposed drainage works. The proposed works would be carried out on a
section-by-section basis to minimize period of nuisance to the nearby sensitive
receivers during construction.
2.3.2
In
open-cut method, temporary traffic management will be carried out on a
section-by-section basis to minimize period of nuisance to the village traffic.
Upon the completion of utility survey and inspection pits to ensure no existing
utilities would clash with the proposed works, ground excavation will take
place between the time periods 7am and 7pm. No construction noise permit would
be required. For excavation greater than 1.2m, sheetpiles with struts and wales
will be constructed as temporary support adjacent to the slope. Underground
pipes would be laid after the completion of pipe bedding and then backfilled with
soil.
2.3.3
In
trenchless method, the insertion pit and receiving pit would be constructed for
the trenchless pipe sections. The proposed pipes would be constructed by pipe
jacking method.
Proposed
Channels
2.3.4
The area
for the proposed widening and deepening of channels will be excavated. Upon the
completion of excavation, fixing of reinforcement bars would be carried out on
site for the structures of the proposed rectangular channels and concreted. The Aquilaria
Sinensis (seedling) in Sung
Shan New Village will be protected and retained during construction.
2.4.1
The
proposed drainage improvement works are planned to commence in 2022 with a view
to completing all the proposed works in 2025.
3.1
Air Quality
3.1.1
With proper implementation of good site
practices stipulated in the Air Pollution Control (Construction Dust) Regulation
and with the adoption of construction machineries and non-road vehicles meeting
the prescribed emission standards and requirements specified in the Air
Pollution Control (Non-road Mobile Machinery) (Emission) Regulation, no adverse
air quality impacts associated with the proposed drainage improvement works is
anticipated.
3.2.1
The potential noise impacts due to the proposed
drainage improvement works at Sung Shan New Village, Tai Wo, Lin Fa Tei and Ha
Che have been evaluated. Whilst the Contractor may prefer to use different
construction methods, types and numbers of Powered Mechanical Equipment (PME),
the assumed tentative construction schedule and plant inventory are
representative and provide a conservative noise assessment of reference value.
3.2.2
With adopting the quiet PMEs, temporary noise
barrier and good site practices as stipulated in the Code of Practice on Good
Management Practice to Prevent Violation of the Noise Control Ordinance (Cap.
400) (for Construction Industry) to minimize the construction noise impacts,
construction noise levels at the representative NSRs will fully comply with the
relevant noise criteria.
3.3.1
The potential ecological impact from the
proposed drainage improvement project at Yuen Long has been evaluated in accordance
with the applicable Technical Memorandum on Environmental Impact Assessment
Process (EIAO-TM). The project will cover four village areas, namely Sung Shan
New Village, Tai Wo, Lin Fa Tei and Ha Che, and a total no. of 14 habitat types
and 41 species of local or global conservation interest has been delineated and
identified within the 500m Study Area of each work site. Because most of the
work site is adjacent to populated village and hence bordered by man-made or
heavily disturbed habitats, only a few natural or semi-natural habitats and
species of conservation interest will be directly or indirectly affected by the
project, including the riverine habitats, one protected plant species (Aquilaria
sinensis), as well as two species of endemic freshwater crab which has been
categorised as "endangered" (Somanniathelphusa zanklon) and
"vulnerable" to extinction (Cryptopotamon anacoluthon) by the
International Union for Conservation of Nature and Natural Resources. The
drainage improvement work which involve widening and deepening of the existing
watercourses in Ha Che and Lin Fa Tei will unavoidably destroy their habitat
and potentially affect the local population of these two species in the Kam Tin
area. As
a whole for the proposed Project which cover a length of ~2800m watercourse,
the ecological impact from the potential permanent loss of 2110 m long
semi-natural watercourse habitat and 25m long channelized watercourse are
considered to be minor to moderate and moderate respectively. All
recognised sites of conservation importance including Tai Lam Country Park and
Lam Tsuen Country Park are avoided under the project.
3.3.2
A range of mitigation measures related to good
site management and construction practice, as well as scheduling of the staged
work program have been recommended to avoid or minimize the ecological impact
to the valuable ecological resources within or in the vicinity of the work
areas. As there is no conflict between Aquilaria
sinensis and the proposed works within the site boundary of the works, this
tree species within the vicinity will be protected and retained during
construction. Translocation of the two endemic crab species to area
protected from anthropogenic disturbance and development pressure within the
Kam Tin Valley, has been recommended before the commencement of the
construction work. Implementation
principle and guidelines has been suggested in this assessment and the detail
processes including any monitoring requirement will be detailed in a
"Freshwater Crab Translocation Plan" to be prepared by an Ecologist
for Agriculture, Fisheries and Conservation Department approval.
3.3.3
Furthermore, the reinstatement of the widened
channels has provided an opportunity to restore the ecological functions
provided by the disturbed riverine habitat, and a range of hardscapes and
greening approach have been suggested to enhance the ecological quality of the
restored habitat, including those suitable for the recolonization of the two
endemic crab species. A "Habitat
Creation and Management Plan" collaborated by an engineer, ecologist and
landscape architect has been recommended to detail the restoration process and
monitoring strategy of the reinstate riverine habitat.
3.3.4
Nevertheless, it should be noted that the
widened channels are open habitat and its riparian zone and the flora and fauna
that could be established or colonised within the work site is subject to the
habitat quality of the adjacent areas including the water quality in the
watercourse upstream and downstream of the widened channels, and the potential
anthropogenic disturbance nearby. Accordingly, the effectiveness of the habitat
restoration should be evaluated on the spectrum and breadth of the ecological
functions performed by the restored habitat.
3.3.5
Finally, with the implementation of the
mitigation measures recommended in this assessment, there will be no residual
ecological impact from the project and off-site mitigation measures would not
be required.
3.4.1
Key issues in terms of water quality would be
related to excavation works for the construction phase of the proposed drainage
improvement works. To minimize potential impacts on water quality during the
channel construction, the excavation would be carried out in dry condition
(even in wet season) by diverting the stream flow from upstream by a temporary
drainage channel with a temporary sheet piles, earth bund or barrier, so that
the works area will remain dry for later excavation and widening works.
3.4.2
With implementation of recommended appropriate
mitigation measures, the construction works for the proposed drainage
improvement works would not be anticipated to result in unacceptable impacts on
water quality.
3.4.3
Water quality monitoring and audit should be
carried out to detect any deterioration of water quality during the construction
phase
3.4.4
During operation of the Project, the drainage
improvement works would not produce extra point sources or non-point source
pollution loading. The new alignments of the drainage would provide widened
sections to alleviate flooding during heavy rainfalls.
3.4.5
In order to avoid adverse pollution from first
flush during rainstorm, regular maintenance debris clearances are recommended,
perfectly before rainstorm events. Maintenance desilting may be necessary for
the proposed channel to remove excessive silts, vegetation, debris and
obstruction. Desilting should be carried out during period of low flow.
3.5
Waste
Management
3.6.1
According to review in historical land use,
relevant spillage accident records of EPD and Fire Services Department and site
appraisal, all identified potentially contaminated sites were located outside
works area boundary and no sign of migration of contaminant was observed.
Therefore, contamination potential arising from the Project works is not
anticipated. Further site investigation for this Project is considered not
necessary.
3.7
Landscape
& Visual
3.7.1
The
proposed drainage developments at the locations studied will see some change in
the landscape and visual amenity of the project sites, although the works
generally involve upgrading of the existing channels rather than constructing a
totally new drainage elements, the assessed landscape and visual impacts are
referenced to the existing context.
3.7.2
The
design of the drainage proposals have sought to be as sensitive as possible,
given the functional requirements, to the existing landscape setting. The
landscape and visual mitigation proposals are centred on the use of natural
watercourse bedding in wider channels in coordination with channel and
embankment greening as well as the provision of tree and shrub planting along
the channel edges to integrate with groups of retained trees to form a narrow
landscape buffer. Since the development proposals are low in height this
planting will screen low-level views (the majority of the existing Visually
Sensitive Receivers (VSR) are low-level) and integrate the proposals within the
existing landscape framework.
3.7.3
Given
the proposed design of the proposals, the likely impacts on landscape resources
and Landscape Character areas during the design year (Year 10) will range from
slight adverse to insubstantial. Although the visual impact assessment suggest
a slight /moderate adverse impact at year 10 for one VSR (VSR-9 at Lin Fa Tei)
the majority are within the range Slight to Insubstantial. However, owing to
the rural nature of the existing setting, the more significant impacts to views
are only available to a relatively few people. It should also be noted that the
works are an opportunity to make visual improvements and that slight and slight
/ moderate beneficial impacts are also predicted at locations where aesthetic
treatments to structures and the introduction of greenery to areas currently
lacking managed vegetation can provide improvements to the visual resources in
the longer term.
3.7.4
In
accordance with the criteria and guidelines for evaluating and assessing
impacts as state in Annex 10, Clause 1.1(c) of the EIAO-TM, overall, it is
considered that the residual landscape and visual impacts of the proposed
development are acceptable with mitigation at all four villages during the
construction and operation phases.
3.8
Cultural
Heritage
3.8.1
The proposed drainage works are generally not
expected to impact on archaeology during the
construction and operational phases with the exception of an area within
Lin Fa Tei Site of Archaeological Interest (SAI) near the previous findings of
wooden remains. It is recommended that
an Archaeological Survey be undertaken for proposed intercept drain works area
near the previous findings prior to the construction phase by a qualified
archaeologist who obtains a
licence under the Antiquities and Monuments Ordinance (Cap. 53). The
scope and methodology of the Archaeological Survey should be agreed with
Antiquities and Monuments Office (AMO) prior to implementation. Tentatively and subject to
agreement with AMO, a fieldscan, where possible, twenty auger tests and four 5
by 1m narrow trenches are proposed to further assess the archaeological
potential of the area. If significant remains are uncovered, the AMO
should be notified and mitigation and/or an appropriate way forward should be
formulated and implemented in agreement with AMO.
3.8.3
Three graded historic buildings are located in
proximity of the proposed works; Lee Tat Bridge (Grade 3) in Shui Tsan Tin
at 13.3m, Lan Fong Study Hall (Grade 3)
in Chuk Hang at 57.7m, and St. John's Chapel (Grade 2) in Cheung Po at 46.4m
from works boundary and require mitigation measures during the construction
phase.
4.1.1
With the adoption
of the recommended mitigation measures during construction phase, the potential
environmental impacts associated with the Project will be minimised to
acceptable levels. There would be no adverse residual environmental impacts to
the noise and air sensitive receivers in the vicinity of the Project.
4.2.1
With the
consideration of various alternative design and construction methods, the
Project will avoid or minimise the impact to environmentally sensitive areas.
Moreover, the Aquilaria Sinensis (seedling) in Sung Shan New Village will also be protected and
retained.
4.3
Key
Environmental Problems Avoided
4.3.1
Key issues in terms of water quality would be
related to excavation works for the construction phase of the proposed drainage
improvement works. To minimize potential impacts on water quality during the
channel construction, the excavation would be carried out in dry condition
(even in wet season) by diverting the stream flow from upstream by a temporary
drainage channel with a temporary sheet piles, earth bunds or barriers, so that
the works area will remain dry for later excavation and widening works.
4.3.2
Noise levels exceedance at the representative
NSRs during construction phase is anticipated for unmitigated scenario. With
adopting the quiet PMEs, temporary noise barrier and good site practices, no
exceedance of the construction noise criteria is anticipated.
4.4.1
The environmental benefits of environmental
protection measures are listed below:
·
Air quality: Implementation of
good house-keeping and dust suppression measures such as water spraying would
avoid/minimize dust emissions during construction phase.
·
Noise: Implementation of temporary
noise barriers and quieter plant would reduce the construction noise impact to
the neighbouring noise sensitive receivers.
·
Water quality: Implementation of
good site practices to avoid/minimize polluted site runoff from the Project to
neighbouring water sensitive receivers.
·
Waste management: Implementation
of waste reduction and good management control could minimize environmental
implication from on-site waste storage.
·
Ecology: The Project will involve
drainage channel widening and will not encroach to any ecological sensitive
areas. Only a few natural or semi-natural habitats and species of conservation
interest will be directly or indirectly affected by the project. With the
implementation of the mitigation measures, there will be no residual ecological
impact.
·
Landscape and visual: Landscape and
visual impacts are acceptable with the implementation of mitigation measures.
·
Land contamination: All identified
potentially contaminated sites were located outside works area boundary.
Therefore contamination potential arising from the Project works is not
anticipated.
·
Built Heritage and Archaeology:
The alignments of drainage channel widening and new drainage culverts will
avoid/minimize direct and indirect impacts to built heritage and archaeology.
5.
ENVIRONMENTAL MONITORING AND AUDIT REQUIREMENT
5.1.1
An Environmental Monitoring and Audit (EM&A)
Manual and an Environmental Mitigation Implementation Schedule (EMIS) have been
prepared to monitor and audit the relevant air quality, noise, water quality,
waste management, land contamination, landscape and visual and cultural
heritage impacts. Event and action plan for the potential environmental impacts
has been formulated and stated in the EM&A Manual.
6.1.1
Upon completion of the proposed channel widening
and new drainage culvert works, there will be reduction of flood risk around
Sung Shan New Village, Tai Wo, Lin Fa Tei and Ha Che. The EIA study concludes
that with incorporation of the recommended mitigation measures and proper
implementation of the EM&A programme, the Project will not impose adverse
impacts on the neighbouring environment during construction and operational
phases.