1.1.2
There is a need for the upgrade of YLSTW into
Yuen Long Effluent Polishing Plant (YLEPP) in order to cope with the forecast
increase in sewage flow upon completion of sewerage under interfacing projects,
extension of village sewerage in area as planned by Environmental Protection
Department (EPD), as well as the proposed housing developments in the region.
1.1.3
DSD has commissioned AECOM Asia Company Ltd to
undertake “Agreement No. CE3/2015(DS) Yuen Long Effluent Polishing Plant –
Investigation, Design and Construction Works” (the Assignment) to upgrade the
YLSTW to YLEPP and cater for the future needs.
1.1.4
The Project is a Designated Project (DP) under
the Environmental Impact Assessment Ordinance (EIAO). A Project Profile (No. PP-458/2012) was submitted to the Environmental Protection
Department (EPD) on 27 February 2012 for application for an Environmental
Impact Assessment (EIA) Study Brief under section 5(1)(a) of the EIAO and the
EIA Study Brief No. ESB-241/2012 for the Project was issued on 5 April 2012
under the EIAO.
1.1.5
Subsequent to the issuance of the EIA Study
Brief No. ESB-241/2012, additional scope including effluent reuse system for
non-potable use and organic waste co-digestion has been proposed under the
Assignment. A new Project Profile, entitled “Yuen Long Effluent Polishing
Plant”, was submitted on 9 Oct 2018 (No. PP-570/2018) and an EIA Study Brief
No. ESB-309/2018 was issued on 14 November 2018 under the EIAO.
1.1.6
The purpose of the EIA study is to provide
information on the nature and extent of environmental impacts arising from the
construction and operation of the Project and associated works that will take
place concurrently. This information will contribute to decisions by the
Director of Environmental Protection on:
·
The acceptability
of any potential environmental consequences that are likely to arise as a
result of the Project;
·
The conditions
and requirements for the detailed design, construction, operation and
associated works of the Project to mitigate against potential environmental
consequences wherever practicable; and
·
The acceptability
of residual impacts after the proposed mitigation measures are implemented.
1.2.1
The Project covers the following DP elements of
Schedule 2, Part I under the EIAO (Cap.499):
·
Item F.1 - Sewage
treatment works with an installed capacity of more than 15,000 m3 per day;
·
Item F.4 - An
activity for reuse of treated sewage effluent from a treatment plant; and
·
Item G4 - A waste
disposal facility (excluding any refuse collection point), or waste disposal
activity, for (a) refuse; or (b) chemical, industrial or special wastes.
1.3.1
This Executive Summary (ES) summarizes the
findings, recommendations and conclusions of the EIA Report for the Project.
2.1
Purpose and Scope of Project
2.1.2
The
YLEPP will be constructed in two phases. Phase 1 works will upgrade the
existing YLSTW into YLEPP with a treatment capacity of 100,000 m3/day
in ADWF. Phase 2 works will be implemented subject to further review of sewage
flow projections and will further upgrade the treatment capacity to 180,000 m3/day
in ADWF.
2.1.3
Phase
1 works (Figure 2.2) will include the following
principal elements:
1) Clearance of the existing main
store and administration building for construction of the new Inlet Works,
including inlet pumping station, screening and degritting facilities;
2) Demolition of existing Primary
Sedimentation Tanks (PSTs) No. 5 to 8 for construction of Lamella PSTs;
3) Demolition of existing
Aeration Tanks (ATs) No. 5 to 8 and existing Final Sedimentation Tanks (FSTs)
No. 5 to 8 for construction of new biological and tertiary treatment
facilities;
4) Reconstruction of sludge
treatment facilities;
5) Demolition of existing PSTs
No. 1 to 4 for construction of sludge dewatering building;
6) Demolition of existing Inlet Works
for construction of new admin building;
7) Installation of odour
mitigation works, including the provision of covers and installation of
associated deodourizers to proposed treatment units; and
8)
Other ancillary works, such as organic waste co-digestion, landscaping,
E&M facilities, workshops, laboratory, roadworks etc.
2.1.4
Phase 2 works (Figure 2.3) will
include the following principal elements:
1) Demolition of existing ATs No.
1 to 4 and existing circular FSTs No. 1, 2, 3 and 4 for construction of new
biological and tertiary treatment facilities;
2) Reconstruction of sludge treatment
facilities;
3) Installation of odour
mitigation works, including the provision of covers and installation of
associated deodourizers to proposed additional treatment units;
4) Construction of additional
Lamella PSTs; and
5)
Other ancillary works, such as landscaping, E&M facilities,
roadworks, etc.
2.2
Need and Benefits of the
Project
2.2.1
Currently, a significant portion of YLSTW
catchment is still unsewered. The proposed trunk sewers and their upstream
village sewerage projects in YLSTW’s catchment are being or to be
implemented. In the coming future, the
sewerage system will be extended to Kam Tin, Fairview Park, Nam San Wai, Pat
Heung, Shek Kong, Ngau Tam Mei and San Tin. These sewerage works are being
implemented under Agreement No. CE 13/2006(DS) Yuen Long and Kam Tin Sewerage
Stage 2 and Stage 3 – D&C and Agreement No. CE 30/2006(DS) Yuen Long and
Kam Tin Sewerage and Sewage Disposal – D&C.
2.2.2
A water quality improvement programme is being
implemented under Agreement No. CE37/2012(DS) Improvement of Yuen Long Town
Nullah (Town Centre Section) Stage 1 Improvement Works. This project will
involve provision of a dry weather flow interceptor (DWFI) system to intercept
the polluted dry weather runoff from Yuen Long Creek to YLEPP for treatment. In
addition to the above mentioned projects, sewage flow from other existing and
planned developments from Kam Tin South, Ngau Tam Mei and Wang Chau, including
the proposed multi-storey buildings in the vicinity of Yuen Long Industrial
Estate, in the catchment would also contribute to the flow build-up at YLEPP.
2.2.3
Having considered the abovementioned projects
and population projections, the projected ADWF will reach approximately 180,000
m3/day in Year 2041. Given the current treatment capacity of YLSTW
is only 70,000 m3/day, a capacity shortfall of YLSTW is anticipated
in future. Thus, there is a need to upgrade the treatment capacity of YLSTW.
The treatment level of YLSTW will also be upgraded for improvement of water
quality of the discharge waterbody.
2.2.4
With the YLEPP in place, opportunities to treat
the sewage from those unsewered areas will be created after completion of the
Project, which provides centralised tertiary sewage treatment. Compared to
de-centralised systems such as scattered septic tanks and local treatment plants,
YLEPP will give higher treatment efficiency and cost effectiveness as well as
improve the living environment of these areas. With the enhancement of odour
management of the YLEPP (covering all odorous facilities and installation of
deodorization units), odour nuisance to the surrounding area would be
effectively controlled and minimized.
2.2.5
The Project will also provide opportunity to
upgrade the existing YLSTW treatment level to a tertiary treatment level to
meet the requirement of “No Net Increase in Pollution Load to Deep Bay”. Given the high effluent standard of tertiary
treatment, the increased pollution loadings due to capacity increase will be
offset by the upgraded treatment performance of YLEPP as well as the
anticipated reduction of pollution loads from unsewered area within Deep Bay
catchments through sewerage connection.
It is anticipated that water quality improvement to the surrounding
waterbodies will be resulted from implementation of the Project.
2.2.6
As a sustainability consideration, co-digestion
of organic wastes with sewage sludge within YLEPP will be adopted to enhance
energy recovery from the anaerobic digestion process. Additional facilities for
organic wastes co-digestion, including reception facilities, digesters and
ammonia stripping plants, will be located within the YLEPP’s footprint.
Consideration of Phased Installation
2.3.1
Formulation of the implementation programme of
YLEPP is based on a number of factors, including requirements of statutory
procedures, site constraints and estimated construction period. It could be
necessary to ensure that the implementation programme could cope with the
buildup of sewage flow in the catchment. According to the sewage flow
projections, the projected ADWF to YLEPP will be up to 180,000 m3/day
in 2041. However, the exact sewage flow is highly subject to the implementation
programme of individual projects and population growth in the catchment. A
phased implementation programme and layout design are required to cater for the
potential future changes.
2.3.2
While all the proposed upgrading works will be
taken place within YLSTW boundary, one of the challenging tasks for upgrading
YLSTW to YLEPP is to maintain the operation of existing YLSTW during
construction period. The treatment capacity of existing YLSTW is 70,000 m3/day,
containing eight equal sets of sewage treatment streams. During Phase 1 works,
half of these treatment streams will be decommissioned and demolished. The
remaining treatment capacity will then be significantly reduced during the
construction period of Phase 1 works and capacity shortfall of such operation
mode may be happened in Year 2026. As such, it is necessary to complete the
Phase 1 works in or before Year 2026.
2.3.3
To deal with the above concerns, it is
considered prudent to increase the treatment capacity of YLEPP Phase 1 to
increase the flexibility for implementing Phase 2 upgrading works. The
recommended treatment capacity for YLEPP Phase 1 would be 100,000 m3/day,
being the maximum capacity that could be provided in the area when half of the
existing treatment streams is decommissioned for carrying out the upgrading
works. The tentative treatment capacity of Phase 2 YLEPP will be designed up to
180,000 m3/d.
2.3.4
The
proposed construction programme and installation phasing of YLEPP is presented
in Table 2.1.
Table
2.1 Implementation Programme
|
Recommended Phased Installation
|
Treatment Capacity (m3/day)
|
Tentative Year of Commissioning
|
Existing
|
70,000
|
-
|
Phase 1
|
100,000
|
2026
|
Phase 2
|
180,000
|
2030(1)
|
Note: (1) The implementation programme of Phase 2 works will be subject to
further review on sewage flow projections
Sewage Treatment
2.3.5
The treatment option evaluation mainly focuses
on the biological treatment processes as this is the critical part in YLEPP
layouts.
2.3.6
A preliminary review of potential biological
treatment processes, including proven treatment processes, market availability,
overseas and local experiences and the emerging treatment process, have been
conducted. Two major types of treatment process include the following:
·
Conventional
Activated Sludge (CAS)
·
Compacted-type Technologies
2.3.7
In considering the footprint for various
biological treatment options, CAS will involve a considerably larger volume of
excavation works and higher construction period. Thus, Compacted-type
Technology were recommended.
Effluent Reuse
2.3.8
In order to reduce water consumption in future
operation and maintenance of YLEPP, reuse of treated effluent is adopted as one
of the sustainability considerations.
2.3.9
The treated effluent will only be reused for the
purposes of chemical preparation, water supplement to deodorisation units and
cleaning of treatment equipment, which consumed majority part of water demand
in daily operation and maintenance of YLEPP.
2.3.10
All the treated effluent reuse will be applied
to YLEPP internally via an automatic close-loop system without direct human
contact. With proper preventive measures in place, potential health and hygiene
impacts are not anticipated during operation and maintenance of the effluent
reuse system.
Sludge Treatment
2.3.11
Sludge treatment at existing YLSTW consists of
primary sludge thickening by gravity thickeners, anaerobic digestion and
dewatering by membrane filter presses. Biogas generated in anaerobic digestion
process is currently used to generate power by micro-turbine on-site. The generated power is then used to warm up
the digesters for the sludge digestion process.
2.3.12
Sludge cake from future YLEPP will be conveyed
to the Sludge Treatment Facility (STF) in Tuen Mun for incineration. Prior to
conveyance to the STF, the following handling options are considered:
·
Dewatering with prior anaerobic digestion including
organic waste co-digestion
·
Dewatering with prior anaerobic digestion
without organic waste co-digestion
·
Direct dewatering without digestion and
organic waste co-digestion
2.3.13
Anaerobic digestion is recommended as this can
reduce the volume of sludge to be disposed of to STF, and allow the recovery of
heat and energy from the biogas generated for utilization within YLEPP.
2.3.14
As a sustainability consideration, co-digestion
of organic wastes with sewage sludge within YLEPP is recommended to enhance energy
recovery from the anaerobic digestion process. Additional facilities for
organic wastes co-digestion, including reception facilities, digesters and
ammonia stripping plants, will be located within the YLEPP’s footprint.
Layout
2.3.15
Consideration of layout options were numerous
engineering constraints and environmental considerations. The internal layout
of YLEPP has been formulated taking account of the following factors:
·
The locations, size and arrangement on new treatment
facility is bounded by recommended treatment options. Thus, compacted size
treatment facility is provided in the layout.
·
In green building
consideration, energy recovery from biogas is recommended. Thus, chimneys from
Combined Heat and Power (CHP) is required in YLEPP.
·
The required
treatment capacity would limit the size of treatment units and so as the
requirement of odour emission and the requirement on deodorization units to
cater the odour nuisance due to sewage treatment process.
·
The layout of
different treatment units is determined with due considerations of not only the
process requirements, but also environmental factors, e.g. most of the air
emission sources are located in approximately middle of the site with
sufficient setbacks from the surrounding sensitive receivers.
·
The scale and
size of above-ground structures are determined by striking a balance between
the plant’s hydraulics and visual impacts to the surroundings. Most of the
structures are designed with heights below the tree lines at the eastern and
western sides which could serve as visual screens.
·
There is a need
to continue operation of YLSTW, thus Phase 1 construction should be commenced
on eastern side of the site. Considerations have also been made on provision of
temporary measures, if necessary, to ensure adequate treatment during the
course of Phase 1 construction.
Consideration of Locations for the New
Treatment Facilities
2.3.16
The location of new treatment facilities is
bounded by the inlet pipes and effluent outfall at the southern and eastern
sides respectively. In order to minimize the scale of construction, existing
sewage inlet pipes/chambers and effluent outfall would be retained and reused
in YLEPP. In addition, all the construction works and new facilities would be
within the existing YLSTW to avoid additional project footprint. The new
treatment facilities arrangement is then designed under these boundary
conditions.
Avoidance and Reducing Environmental Impacts
from Design and Layout
2.3.17
In order avoid and minimize environmental impact
in terms of air quality, noise, water quality, ecological, landscape and visual
aspect, the following major design and layout will be adopted in YLEPP:
·
All the treatment units will be covered and ventilated
via deodorization units. Thus, odour impact would be minimized.
·
All the treatment facilities and building will be
ventilated with silencers at lourvers. Thus, fixed noise impact would then be
minimized.
·
A set of design measures will be installed to avoid
and minimize the chance on emergency discharge
·
All the construction works and new facility will be
well within the existing YLSTW. No additional footprint will be required and
direct loss of nearby habitats are avoided.
·
All the treatment units and buildings are designed
with due considerations on minimizing the building heights by such means as
adopting equipment that requires low headroom.
This is to ensure all the aboveground structures would not be
excessively bulky so as to minimize the visual impacts.
·
All the trees along the eastern and northern boundary
of the site be retained as much as possible in order to maintain a tree-barrier
surrounding YLEPP to avoid/minimise visual impact.
·
YLSTW’s existing effluent discharge point and
emergency discharge points at nearby river / nullah will be retained for YLEPP
in order to avoid direct impact to nearby water body.
Avoidance and Minimization of Emergency
Discharges
2.3.18
The design layout would adopt measures to ensure
the reliability and to avoid and minimize the risk of emergency discharges of
YLEPP. The following design measures would be adopted at YLEPP:
·
Provision of adequate standby units and peaking
factors
·
Provision of by-pass mechanism at coarse and fine
screens
·
Provision of reliable power supply
·
Provision on interim emergency by-pass
·
Regular maintenances and inspections
·
Application of Emergency Response Plan
Consideration of Demolition Methods
2.4.1
The implementation of YLEPP will mainly be
carried out by demolition of existing buildings/structures of YLSTW for
construction of new treatment facilities. With reference to the Code of
Practice for Demolition of Buildings (DCDB, Buildings Department 2004), several
main methods of techniques for the demolition works of the Project are
identified, including:
·
Implosion;
·
Breaker
(excavator mounted);
·
Wrecking ball;
·
Cutting and
drilling;
·
Non-explosive
demolition agents;
·
Thermal lance;
and
·
Water jet.
2.4.2
Implosion
induces higher environmental dis-benefit which does not offer any potential
reduction in polluting impacts in the form of noise, vibration and dust and is
not efficient for slabs and walls that will require demolition. It is also hard
to maintain a live STW during implosion.
2.4.3
Demolition
by breakers (excavator mounted) is top down method for demolishing all types of
structures. The environmental dis-benefit is that machine mounted breakers do
not offer any potential reduction in dust, noise or vibration emissions (DCDB,
2004). However, these methods are
considered having most efficient demolition rate which is an environmental
benefit due to shortening of the construction periods and capability to cater
the tight programme
2.4.4
Wrecking ball is generally suitable for
dilapidated buildings but would not be applicable in this case where the clear
space to the edge of the structures is limited in places and structures have
substantial steel reinforcement. This application also demands high level skill
operators and well-maintained equipment.
2.4.5
Other abovementioned methods with environmental
benefits in the form of noise, vibration and dust can be raised by using
equipment such as crushers, circular saw cutting, wire saw cutting, and stitch
drilling which are effective for all structures and can reduce vibration, noise
and dust. Non-explosive demolition agent
can also reduce vibration, noise and dust but is not applicable to slabs and
walls. The use of thermal lance and or
high-pressure water jets would not generally be recommended unless there are no
other viable alternatives since it would induce longer construction time.
2.4.6
These methods would generally result in lesser
environmental impacts (DCDB, 2004), but the demolition rate of using these
methods are generally longer and, therefore, difficult to meet the tight
programme (to completed Phase 1 works by Year 2026). Nevertheless, a selection
of the above processes could be used for noise sensitive locations and seasons.
2.4.7
A variety of top-down methods are recommended to
be used and various element from a suite of powered mechanical equipment have
been assumed to be in use at locations or seasons with less sensitive to noise
exposure. The use of breakers is
efficient and noise and dust impacts can potentially be controlled by a range
of practical mitigation measures (e.g. noise barriers, dust control) familiar
to the construction industry in Hong Kong.
2.4.8
Other quieter methods such as crushers, circular
saw cutting, wire saw cutting, and stitch drilling would be adopted for the period
from November to March to minimise the construction noise impacts on
overwintering waterbirds.
Consideration of Foundation Methods
2.4.9
The foundation options are highly subject to the
ground conditions. According to the latest ground investigation findings, the
site is constrained by geotechnical constraints (e.g. deep bed rocks, presence
of marbles, high water table, etc.). In considering the geotechnical
feasibility, the following foundation method is shortlisted:-
·
Bored piles (Large diameter boring by reverse circulation
drill (RCD))
·
Percussive piles
·
Box rafts
·
Shallow
foundation (for light-duty structures only)
2.4.10
In
considering the construction noise and ecological impact, raft foundation,
shallow foundation and bored piles by reverse circulation drill will be adopted
as far as possible. However, due to ground conditions constraints and programme constraints, foundation
method such as percussive piling may be required. In order to avoid
construction noise and the associated indirect impact to waterbirds, percussive
piling, if any, will only be adopted in wet season.
2.5
Construction Programme
2.5.1
The Project construction works are anticipated
to commence in 2020 with completion of the Project by 2026 and 2030 for Phase 1
and Phase 2 respectively.
3
Key Findings of the environmental impact Assessment
3.1
Air Quality Impact
3.1.1
Potential air quality impacts associated with
the construction and operational phases of the project have been assessed in
accordance with the criteria and guidelines as stated in the requirements given
in Section 3.4.1 and Appendix B of the EIA Study Brief, as well as Annexes 4
and 12 of EIAO-TM.
The assessment area for air quality impact assessment is within 500m
from the boundary of the Project site.
3.1.2
Potential air quality impacts from the
construction works
of the Project would mainly be related to construction dust from site
clearance, excavation, demolition, piling, pipe works construction and wind
erosion. Quantitative fugitive dust
assessments have been conducted, taking into account the cumulative impact
caused by nearby concurrent sources within 500m from the boundary of the
Project site. With the implementation of mitigation
measures specified in the Air Pollution Control (Construction Dust) Regulation
together with the recommended dust suppression measures including watering once every
two hours on heavy construction works areas and adopting good site practices, no adverse dust impact at air
sensitive receivers would be anticipated due to the construction activities of
the Project.
3.1.3
Potential air quality impacts during operational phase would
come from odour emission from the sewage treatment processes in YLEPP and
ammonia stripping units. Odour emitted would all be treated in the deodourizing
units
with odour removal efficiency of 90 – 95% for odour from sewage
treatment processes and 70% for odour (ammonia) from ammonia stripping units
before venting to the atmosphere. The
other odour emission sources in the YLIE have also been considered in the
cumulative odour impact assessment. With
the implementation of odour control measures, the assessment results show that
the predicted odour concentrations at all ASRs located in the vicinity of YLEPP
would comply with the odour criterion (5 odour units based on an averaging
time of 5 seconds) stipulated in the EIAO-TM.
3.1.4
During operation phase, flue gas emission would
be emitted from the stacks of CHP, boiler and ammonia stripping units in the
YLEPP. Cumulative air quality impact
arising from YLEPP operation, the vehicular emissions from the open roads, and
industrial chimney emissions within the 500m assessment area has been assessed
for Phase 1 and Phase 2. Assessment
results indicate that potential cumulative air pollutants including nitrogen
dioxide, respirable suspended particulates, fine suspended particulates,
sulphur dioxide, and ammonia concentrations at all the representative ASRs
would comply with the AQOs and relevant international standards. No adverse air quality impact would be
anticipated during the operation of YLEPP.
3.2
Noise Impact
3.2.1
Potential noise impacts associated with
the construction and operational phases of the project have been assessed in
accordance with the criteria and guidelines as stated in the requirements given
in Section 3.4.2
and Appendix C
of the EIA Study Brief, as well as Annexes 5 and 13 of the EIAO-TM.
The study area for noise impact assessment is defined by a distance of
300m from the site boundary of the Project.
3.2.2
Construction noise is expected from the use of Powered Mechanical Equipment (PME) during various
construction activities, such as demolition of the existing YLSTW,
foundation and superstructure works for the proposed YLEPP, at all
land-based works areas within Project boundary. Noise impact arising from construction
activities of the Project was assessed.
The predicted maximum unmitigated construction noise levels at the
representative noise sensitive receivers (NSRs) in the vicinity of the
Project work sites
would be 76 – 80 dB(A) for Phase 1 and 67 – 71 dB(A) for Phase 2. With the use of movable noise barrier as
mitigation measure for the exceedance in Phase 1, the predicted maximum construction airborne noise levels at the representative NSRs would be 72
– 75 dB(A), complying with the EIAO-TM criteria.
3.2.3
The noise impact associated with the operation
of the Project was assessed. Based on
the plant design information, the predicted fixed plant noise levels at all the
representative NSRs would be comply with the criteria with the implementation
of mitigation measures including locating plants inside plantrooms (with
installed sound proof door and silencers at air inlet and outlet) and provision
of silencers for ventilation fans. Commissioning test should be conducted
to ensure the compliance of noise standards for fixed plant noise.
3.3
Water Quality Impact
3.3.2
Minor water quality impact would be associated
with land-based construction. Impacts may result from surface runoff,
accidental spillage, and sewage from on-site construction workers. Impacts could be controlled to comply with
the WPCO standards by implementing the recommended mitigation measures. No
unacceptable water quality impact would be expected during the construction
phase of the Project with the recommended mitigation measures properly
implemented.
3.3.3
The treated effluent will be discharged to Shan
Pui River during normal operation. The existing YLSTW will be upgraded to YLEPP
in which a more stringent effluent design standard tertiary treatment will be
provided. It is anticipated that overall
water quality in Deep Bay will be improved and the Project will meet the
“Requirement of No Net Increase in Pollution Load to Deep Bay”
3.3.4
Emergency discharges from the Project would be
the consequence of pump failure, interruption of the electrical power supply or
failure of treatment units. Mitigation measures, including dual power supply, standby
pumps, treatment units and equipment, would be provided to avoid the occurrence
of any emergency discharge. An emergency
response plan will be formulated to minimize the impact of emergency discharges
and facilitate subsequent management of the emergency. No unacceptable water quality impact would be
expected during the operational phase of the Project with the recommended
mitigation measures properly implemented.
3.4
Waste Management Implication
3.4.1
The
wastes impact assessment was conducted in accordance with the criteria
and guidelines as stated in the requirements given in Section 3.4.4 and Appendix E of the EIA Study Brief, as
well as Annexes 7
and 15
of the EIAO-TM.
3.4.2
Construction and Demolition (C&D) materials
will be generated from excavation and demolition activities. Based on the
latest layout, the volume of surplus C&D materials is estimated to be
approximately 240,000 m3 of inert material and 59,200 m3
of non-inert material.
3.4.3
Inert C&D materials from the above
construction works will be sorted and reused as filling material as much as
possible. The surplus will be transported and disposed at Tuen Mun Area 38 Fill
Bank for use as filling material by other projects. Non-inert waste will be recycled as far
as possible before disposed to landfill. Opportunities in minimisation of
generation and maximisation of reuse would be continually investigated during
the detailed design and construction phases.
With the implementation of the recommended good site practices and
mitigation measures for the handling, transportation and disposal of the
identified waste arising, no adverse environmental impacts would be
anticipated.
3.4.5
Other waste materials, including general refuse
and chemical waste will also be generated throughout
construction. Provided that these identified wastes will be handled,
transported and disposed of using the recommended methods and that good site
practices would be strictly followed, adverse environmental impacts are not
expected.
3.4.6
The main waste types to be generated during the
operation phase would be grit and screenings, and dewatered sludge. The collection, transportation and disposal
practices of the grit and screenings would follow the existing arrangements
currently in operation at the existing YLSTW.
The dewatered sludge would be disposed of to the proposed Sludge
Treatment Facilities. Provided proper handling procedures and disposal method
are adopted, adverse environmental impacts are not expected during the operation
phase.
3.5.1
The
land contamination assessment is conducted in accordance with the
criteria and guidelines as stated in the requirements given in Section 3.4.4
and Appendix E of the EIA Study Brief, as well as Section 3.1 of Annex 19 of
the EIAO-TM.
3.5.2
Based on the site appraisal, there are areas
within the existing YLSTW considered to be with potential land contamination
concerns. A sampling and testing programme, targeting the existing YLSTW had
been proposed. Since the site will continue
to operate, the proposed Site Investigation (SI) works and any necessary
remediation action are recommended to be carried out after the phased
decommissioning of existing YLSTW within the Project area but prior to the
construction. Further site walkover, assessment and remediation (if any),
including the submission of Supplementary Contamination Assessment Plan
(CAP(s)), Contamination Assessment Report/ Remediation Action Plan
(CAR(s)/RAP(s)) and Remediation Report (RR(s)) would follow Environmental
Protection Department’s prevailing guidelines and recommendation in the EIA
Study.
3.5.3
With the implementation of further site
walkover, land contamination assessment and, if required, remediation works for
the Project Site, any soil/groundwater contamination would be identified and
properly treated prior to the re-development.
Land contamination impacts are therefore considered surmountable to
future occupants.
3.6.2
A literature review and 12-month ecological
field surveys covering both dry and wet seasons have been conducted. A total
of nine habitat types, including developed area, plantation, orchard,
shrubland, grassland, reedbed, mangrove, pond (both active and inactive) and
modified watercourse, were recorded within the 500m assessment area from recent
surveys, with developed area being the only habitat recorded within the Project
site. The ecological values of the
wetland associated habitats including reedbed, mangrove, pond (both active and
inactive) and modified watercourse (Shan Pui River and Kam Tin River), are
moderate or moderate to high. The
other habitats, except shrubland which is of low to moderate ecological value,
are considered of low ecological value. Species
of conservation importance recorded within the assessment area included two
flora, 39 avifauna, eight butterflies, four odonate, six herpetofauna, six
mammal species and the endemic Bent-winged Firefly. One avifauna and two mammal species of
conservation importance were recorded within the Project area.
3.6.3
The wetland habitats within the assessment area
supported a large number of overwintering waterbirds that over 2,000
individuals of 23 overwintering / migratory waterbirds species of conservation
importance recorded during the dry season months, with the confluence of Shan
Pui River and Kam Tin River as well as active ponds at the northwest part of
the assessment area in Fung Lok Wai being the key wetland habitats that
supported the greatest abundance and diversity of waterbirds. Significantly lower diversity and abundance
of waterbirds were recorded during wet season months, with ardeids that are
common and present all year around in Hong Kong being the dominant
species. No breeding or nursery
behaviour of any species were identified within the assessment area.
3.6.4
Potential direct impacts on recognised sites of
conservation importance within the assessment area (including the Ramsar Site,
Priority Site, WCA, WBA (outside the Project site), SSSI and CA) and natural
habitats have been avoided through confinement of construction works within the
boundary of the existing YLSTW.
3.6.5
Major indirect impacts due to construction noise
disturbances from demolition using breakers mounted on excavators and
percussive piling works on key wetland habitats within assessment area and in
close proximity to the Project site as well as migratory / overwintering
waterbirds have been avoided through scheduling of the percussive piling works
and demolition using breakers mounted on excavators outside dry season (i.e.
November to March, which is the peak overwintering period of waterbirds).
3.6.6
With the implementation of the recommended
mitigation measures (e.g. avoidance of percussive
piling and demolition using breakers mounted on excavators and use of
alternative quieter construction method during peak overwintering period within
dry season; careful phasing of construction activities; provision of noise
barriers around Project site, provision of moveable noise barrier/acoustic mat
for piling plants and breaker; use of enclosure for construction plant, use of
quality powered mechanical equipment (QPME); restriction of construction hours
of construction activities with powered mechanical equipment (PME); etc.), no
unacceptable adverse residual impacts would be expected during construction or
operation phase. Ecological monitoring
should be conducted during construction phase to monitor the effectiveness of
proposed mitigation measures and detect any unpredicted indirect ecological
impacts arising from the proposed Project and the implementation of mitigation
measures would be subject to regular audit as part of the EM&A programme.
3.7
Fisheries Impact
3.7.1
Potential impacts on fisheries have been
assessed in accordance with Section 3.4.6 and Appendix G of the EIA study brief
as well as Annexes 9 and 17 of the EIAO-TM.
3.7.2
No important spawning or nursery grounds were
identified in the immediate vicinity of the existing YLSTW. There are no
existing fish culture zones within the Deep Bay WCZ.
3.7.3
The Project would only involve land-based construction
works within the footprint of existing YLSTW. No loss of active or inactive
fishponds are anticipated within the assessment area. There would be no loss of
oyster culture area or fishing ground near Deep Bay. With the implementation of mitigation
measures recommended in the Water Quality Impact Assessment Section for
controlling water quality impact, the Project would not cause any unacceptable
water quality impact to adjacent fishponds or oyster culture area and fishing
ground near Deep Bay during construction and normal operation. No unacceptable
water quality impacts to adjacent fishponds, oyster culture area and fishing
ground during emergency discharge from YLEPP are anticipated. Groundwater table
monitoring will be undertaken during construction phase of the Project.
3.8.1
A Landscape and visual impact assessment has
been carried out in accordance with Section 3.4.7 and Appendix H of the EIA
study brief, Annexes 10 and 18 of the EIAO-TM, and EIAO Guidance Note No.8/2010.
3.8.2
As the entire project will be developed within
the existing YLSTW and most of the existing perimeter trees will be retained,
the Project will not have substantial landscape and visual impacts during
construction and operation phases. As a whole, it is considered that the
residual landscape and visual impacts of the proposed Project is considered
acceptable with proposed mitigation measures implemented during construction
and operation phases.
3.9.1
Hazard assessment in relation to potential
hazard to life due to biogas was conducted in accordance with the relevant
requirements as specified in Section 3.4.8 and Appendix I of the EIA study
brief, as well as Section 2 of Annex 4 of the EIAO-TM.
3.9.2
The assessment findings revealed that both the individual
and societal risk levels would meet relevant requirements stipulated in the
Hong Kong Government Risk Guidelines (HKRG), i.e. the off-site individual risk
level is far below 1×10-5 per year and the societal risk falls into
the “Acceptable” region. Therefore, the biogas risk associated with the
operation of the YLEPP is considered acceptable.
4
Environmental monitoring and audit (EM&A)
5.1.1
The findings of the EIA provided information on
the nature and extent of the environmental impacts likely to arise from the
construction and operation of the YLEPP.
The EIA has, where appropriate, identified mitigation measures to ensure
compliance with environmental legislation and standards.
5.1.2
Overall, the EIA concluded that the Project
would comply with the requirements of the EIA Study Brief and EIAO-TM with the
implementation of the proposed mitigation measures during the construction and
operational phases
of the YLEPP. The schedule of
implementation of the proposed mitigation measures has been provided in the EIA
Report. An EM&A programme has also been recommended to check the
effectiveness of the proposed mitigation measures.