13.1.1.1
The
Project covers the following designated project (DP) elements of Schedule 2,
Part I under the Environmental Impact Ordinance (EIAO) (Cap.499):
·
Item F.1, Part I of Schedule 2 of the EIAO - Sewage treatment works with
an installed capacity of more than 15,000 m3/day.
·
Item F.4, Part I of Schedule 2 of the EIAO - an activity for reuse of
treated sewage effluent from a treatment plant
13.1.1.2
This
EIA report has provided an assessment of the potential environmental impacts
associated with the construction and operation of the Project based on the
preliminary engineering design information available at this stage. The assessment has been conducted, in
accordance with the Study Brief No. ESB-313/2019 under the
EIAO for the Project and the EIAO-TM, covering the following environmental
issues.
• Air
Quality Impact
• Noise
Impact
• Water
Quality Impact
• Waste
Management Implication
• Land
Contamination
• Ecological
Impact (Terrestrial and Aquatic)
• Landscape
and Visual Impact
• Hazard
to Life
13.1.1.3
The
findings of this EIA Study have determined the likely nature and extent of
environmental impacts predicted to arise from the construction and operation of
the Project. During the EIA process,
specific environmental control and mitigation measures have been identified and
incorporated into the planning and design of the Project in order to achieve
compliance with environmental legislation and standards during both the
construction and operation phases. An
environmental monitoring and audit (EM&A) programme has
also been developed. The Implementation
Schedules listing the recommended mitigation measures are presented in the Section
13.
13.1.1.4
A
summary of the environmental outcomes/benefits that have accrued from the
environmental considerations and analysis during the EIA study and the
implementation of environmental control measures of the Project are presented
in the sections below. The key assessment
assumptions and limitations of methodologies and summary of environmental
impacts with proposed mitigation measures are presented in Appendices 13.1 and 13.2, respectively.
13.2.1
Environmental Benefits of the
Project
13.2.1.1
The
Government plans to develop Yuen Long South Development Area (YLS DA) which is
a mega-scale and complex development aiming to provide land to transform the
degraded brownfield land to developable land contributing to meet the
territory’s medium to long-term need for housing development. YLSEPP will provide sewage treatment to the
sewage collected from the YLS DA and other developments in the North West New
Territories (NWNT), and to subsequently provide treated effluent for further
production of reclaimed water for reuse.
13.2.1.2
This
Project will treat the collected sewage to a tertiary treatment level. The high
effluent standard is suitable for further production of reclaimed water. Most tertiary treated effluent will be reused
to supply YLS DA and other surrounding areas’ flushing water demand, which
saves freshwater resources. Any surplus
tertiary effluent will be discharged to Yuen Long Nullah for river
vitalization. Given the high effluent
standard of tertiary treatment, it is anticipated that no negative impact to
Deep Bay will be resulted.
13.2.1.3
The
Project will also provide the opportunity to incorporate sustainable design and
green features in the proposed treatment facilities such as co-digestion of
organic wastes with sewage sludge to enhance energy recovery, renewable energy,
green roof, effluent reuse, etc.
13.2.2
Environmental Friendly Design
13.2.2.1
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 have been
considered:
·
Tertiary treatment will be adopted in YLSEPP, so that the treated
effluent can be reused.
·
All the treatment units will be covered and ventilated via deodorization
units to control and minimize odour impact.
·
All the treatment facilities will be enclosed within reinforced
concrete buildings and ventilated with silencers at louvers such that fixed noise impact
can be kept within the acceptable level.
·
A set of design measures will be installed to avoid and minimize the
chance on emergency discharge
·
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.
·
Green building design will be incorporated to encourage low carbon and
green STW, such as provision of photovoltaics (PV) system at building rooftops, biogas
recovery and biodiesel as alternative power source for plant operation, reuse
of treated effluent, etc.
13.2.3
Key Environmental Problem
Avoided and Compensation Area Included
Avoidance of Encroachment into Recognized
Site of Conservation Importance
13.2.3.1
While a number of sites of
conservation importance are located within the assessment area for the Project
and that the Project site is located adjacent to “CA”. The Project site and construction works for
the Project are designed to be confined within areas of existing development
and/or within the boundary for planned development under the approved YLS DA,
such that no sites of conservation importance would be directly affected.
Avoidance of Works within Adjacent Nullah
13.2.3.2
The
effluent discharge pipe for the purpose of emergency discharge will be
constructed within the site boundary. As
such, any works within the adjacent nullah that would induce direct impact to
nearby waterbody has been avoided.
Avoidance and Minimization of Emergency
Discharges
13.2.3.3
The
design layout would adopt measures to ensure the reliability and to avoid and
minimize the risk of emergency discharges of YLSEPP. The following design
measures would be adopted at YLSEPP:
·
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 after PST
·
Regular
maintenances and inspections
·
Application of
Emergency Response Plan
13.2.3.4
In
addition, in case of emergency discharge, the upstream pumping station could be
temporarily suspended, preventing sewage from entering to YLSEPP, so to lower
the risk of any emergency discharge.
13.2.4
Population and Environmental
Sensitive Areas Protected
13.2.4.1
The YLSEPP is located at the southern tip of YLS
DA. Population and environmental sensitive areas in the vicinity of the
Project site have been protected through the avoidance and/or minimization of
environmental impacts from the construction and operation the Project.
13.2.4.2
Provided
that the site formation works of YLSEPP, which will be undertaken by CEDD under Agreement No.
CE 35/2012 (CE) “Planning and Engineering Study for Housing Sites in Yuen Long
South – Investigation”, will be
completed before the construction of YLSEPP and all construction works of the
Project being confined within the site boundary, no ecological sensitive areas
would be directly impacted. Population
protected from air quality and noise impacts due to the construction and
operation of the Project comprise the nearby village houses at Pak Sha Tsuen,
Wong Nai Tun Tsuen and Pui Hong Kui. Environmental sensitive areas protected from
adverse water quality impacts include nearby modified watercourses, and the
future reedbed planned under RODP for YLS DA.
13.2.5
Summary of Environmental Findings
Air Quality Impact
13.2.5.1
The
potential air quality impacts from the construction works of the YLSEPP would
mainly be related to the construction dust from the excavation, piling works,
road paving works, construction of substructures and superstructure works. With the implementation of mitigation
measures specified in the Air Pollution Control (Construction Dust) Regulation,
good site practices, regular watering and EM&A programme, no adverse dust
impact at ASRs is anticipated due to the construction activities of the Project.
13.2.5.2
Flue gas emission would be emitted from the
stacks of CHP and boiler in the YLSEPP.
Cumulative air quality impact arising from YLSEPP operation, the
vehicular emissions from the open roads within the 500m assessment area has
been assessed for operation of YLSEPP.
The assessment results conclude that the predicted cumulative the 19th
highest 1-hour average and annual average NO2, the 10th
highest daily and annual average RSP, the 19th highest daily and
annual average FSP, 10-min average and daily average SO2, and the
maximum 1-hour and the maximum 8-hour average CO at representative ASRs would
comply with the corresponding new AQOs.
The predicted maximum 1-hour average and annual average HCL, maximum
1-hour average and annual average HF, maximum 1-hour average methane, maximum 30-minute
average and annual average formaldehyde would comply with the corresponding
international standards. No adverse air quality impact is
anticipated arising from the flue gas emission associated with the operation of
YLSEPP.
13.2.5.3 All
odour sources in YLSEPP are fully enclosed.
The potential odour emission from the sewage treatment facilities,
sludge treatment facilities and organic waste co-digestion facilities would all
be treated in the deodourizers before discharge into
atmosphere. With implementation of the
best-available deodourizers in the market with 95%
odour removal efficiency, locating deodourizer exhaust
away from ASRs as far as practicable, the assessment results show that the
predicted Project-alone 5-second average odour concentration at the
representative ASRs within the Study Area would be below 1 OU.
13.2.5.4 Considering
the cumulative odour impact due to the Project and the retained chicken farm, the
predicted cumulative odour concentrations at all planned ASRs would comply with
the EIAO-TM criterion of 5 OU. No adverse
residual odour impact would be expected at the planned ASRs.
13.2.5.5 Cumulative
odour exceedances to the EIAO-TM criterion of 5 OU are predicted at two
existing representative ASRs, YAE01 and YAE02, and nearby village houses for a short duration of time during operation
phase of the Project. The frequency of
exceedance in odour concentrations at ASRs within the exceedance zone is up to
0.51% of the time in a year. During the
time of exceedance, the proposed YLSEEP would contribute less than 0.45 OU/m3,
while the major odour contribution would be from the retained existing chicken
farm. Nonetheless, the Project will support the YLS DA and bring about a net
improvement in cumulative odour impact for the YLS DA area. Despite the predicted odour exceedance at
some existing ASRs, the cumulative odour impacts at these ASRs will be substantially
improved compared to that of existing condition without removal of the five
livestock farms. With the removal of the
five livestock farms, an overall reduction in odour impacts at all the ASRs
would be anticipated.
13.2.5.6
It is therefore concluded that there is no
adverse residual odour impact arising from the Project.
Noise Impact
13.2.5.7
The
assessment for the potential construction noise impact from construction of the
proposed YLSEPP and its cumulative impact with concurrent projects have been
conducted. The assessment results
indicate that the predicted construction noise levels of the Project at the
NAPs would exceed the noise criteria without mitigation measures. With mitigation measures in place, the
predicted construction noise levels at all NAPs due to Project would comply
with the noise criteria. Thus, no
adverse construction noise impact arising from the Project would be anticipated. Based on best available information the
cumulative construction noise levels at the NAPs would also comply with the
noise criteria. No adverse cumulative
construction noise impact would be anticipated due to the Project and
concurrent projects.
13.2.5.8
The fixed
noise sources impact associated with the operation of the YLSEPP has been
assessed based on the plant design information provided by the Project Engineer
at the time of the assessment. The
assessment results indicate that the predicted fixed noise levels at the NAPs
would comply with the noise criteria under unmitigated scenario. No adverse fixed noise sources impact due to
the operation of the YLSEPP would be anticipated. Commissioning test should be conducted prior
to operation of the Project to ensure that the fixed noise sources impact would
comply with the relevant noise standards.
Water Quality Impact
13.2.5.9
Minor water quality impact would be associated with
land-based construction works. Water
quality impact may result from wastewater generated from the general
construction activities, construction site runoff, construction works near
inland watercourses, sewage effluent from workforce and accidental chemical
spillage. The potential impact could be
mitigated and controlled by implementing the recommended mitigation
measures. No adverse water quality
impact from construction works for the YLSEPP is anticipated. No adverse residual water quality impacts is expected.
13.2.5.10
Mathematical modelling
was conducted under this EIA to study the water quality impacts caused by the
effluent discharge from the proposed YLSEPP.
The model results indicated that the proposed YLSEPP would reduce the
UIA, TP and E. coli levels in Deep Bay. There would be an increase in BOD, TIN, TN and SS levels in Deep Bay due to the effluent discharge
from the proposed YLSEPP. The high
levels of these parameters were mainly contributed from other background
pollution sources which non-compliance for BOD, TIN and UIA were predicted even
under the "without Project" scenario.
The water quality impact will be alleviated once the Water Reclamation Facilities
is implemented. The overall DO levels were
predicted to be improved in inner Deep Bay.
The predicted change in salinity levels would comply well within the WQO
of no more than 10% change from the background levels.
13.2.5.11
It should be noted that
the proposed YLSEPP has already adopted tertiary treatment which is the highest
treatment standard and the best effluent quality that could be achieved in HK’s
sewage treatment. Although the nutrient
level in Deep Bay WCZ was very high and the water was static, it is anticipated that red tide occurrence in Deep Bay WCZ
was limited by the presence of high SS level in the water column which could
reduce the light penetration and limit the energy source for excessive algal
growth. Hence, nutrient (TIN, TN and TP) was not a critical factor for algal bloom in the Deep
Bay waters. Further effect on the red
tide occurrence due to the slightly increase in TN (and TIN) level from the
Project is not expected given that the existing Deep Bay waters has already
contained abundant TN which is considered high enough to trigger red tide but
the red tide occurrence in Deep Bay waters was limited by other environmental
factors. Furthermore, there will be a
future water reclamation facility to further polish part of the treated
effluent from YLSEPP into reclaimed water which will cut down the freshwater
demand in the region, save the precious freshwater resources in the region and
reduce the pollution loading discharge to the Deep Bay waters. The residual impact on the water quality
would be decrease as comparing with normal operation of YLSEPP (i.e. 65,000m3 discharge to Deep Bay).
13.2.5.12
For emergency
discharge, the model results indicated that elevated levels of key water
quality parameters would be recovered within 1 day after termination of the
emergency discharge for WSRs within Inner Deep Bay. The more distant WSR i.e.
Oyster Culture Area was found not to be affected by emergency discharge
event. The occurrence of emergency
discharge from the proposed YLSEPP can be minimised
by the implementation of appropriate contingency measures, such as
standby unit for all major equipment and back-up power for dual power supply
would be provided for the proposed YLSEPP to prevent emergency
situation as far as practicable.
An Emergency Response Plan will be formulated prior to commissioning of
YLSEPP to minimize the impact of emergency discharges and facilitate subsequent
management of the emergency.
13.2.5.13
Other water quality impacts associated with the
operation phase are identified as surface runoff from paved areas and
accidental spillage. It is expected that
these potential impacts can be prevented by adopting recommended mitigation
measures.
Waste Management Implication
13.2.5.14
Waste
management implications associated with the construction and operation of the
Project were identified and assessed. Waste types generated by the construction
activities of the Project would include C&D materials (from excavation and construction works for the proposed YLSEPP), general refuse (from construction
workforce) and chemical waste (from maintenance of construction plant and
equipment). Provided that these wastes
are handled, transported and reused/disposed of using approved methods and that
the recommended good site practices are strictly followed, adverse
environmental impacts during construction phase would not be anticipated.
13.2.5.15
Reduction
measures have been recommended to minimise the amount
of materials generated in the Project.
Approximately 268,100 m3 of inert materials and 20,900 m3
of non-inert materials would be generated during the construction phase of the
Project. 52,900 m3 of inert
material would be reused on site while the remaining 215,200 m3 of
surplus C&D inert material would be recycled or transported to PFRFs for
beneficial reuse in other projects.
Non-inert waste would 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. The other materials that cannot be reused or
recycled would be disposed to designated outlets.
13.2.5.16
During
operation, the main waste types to be generated would be grit and screenings,
dewatered sludge, chemical waste and general refuse. The grit and screenings would be compacted and
properly stored in a covered container prior being disposed of at landfill on a
daily basis. The transportation and
disposal of the grit and screenings would be managed and controlled by a
reputable waste collector. The dewatered
sludge would be disposed of to the STF. Provided
proper handling procedures and disposal method are adopted, adverse
environmental impacts would not be anticipated during the operation phase.
Land Contamination
13.2.5.17
A site
appraisal, including the review of the YLS EIA Study, further desktop
review and site walkover, was conducted from August 2020 to September 2021 to
identify any potentially contaminating land uses within the proposed YLSEPP
site. Based on the site appraisal
findings, 23 potentially contaminated sites are located within the proposed
YLSEPP site.
13.2.5.18
Similar to the recommendation in the YLS EIA Study, as the
potentially contaminated sites were inaccessible and still in operation, and
there could be changes in site operation or changes in land use within the
proposed YLSEPP site prior to development which may cause potential land
contamination issues, site re-appraisal
for the potentially contaminated sites within the proposed YLSEPP site should
be conducted once site access is available (e.g. after land resumption) in
order to identify the need for SI for any additional hotspots as a result of
on-going land contaminating activities. In addition, re-appraisal would be
required for the other
remaining areas of the proposed YLSEPP site to assess the latest site situation
in order to address any change in land use that may
give rise to potential land contamination issues. The
further works including site re-appraisal for the whole proposed YLSEPP site,
associated SI works, any necessary remediation works
and submission of supplementary CAP / CAR / RAP / RR are recommended to be
carried out when site access is available (e.g. after land resumption) but
prior to commencement of any construction or development works at the
identified contaminated sites, and would follow the relevant
Guidance Manual, Guidance Note and Practice Guide.
13.2.5.19
With the implementation of the recommended further
works for the Project, any soil / groundwater contamination would be identified
and properly treated prior to the construction works. No insurmountable land contamination impacts
to the Project are therefore anticipated.
13.2.5.20
Ecological
Impact (Terrestrial and Aquatic)
13.2.5.21 The
Project site of YLS EPP is restricted within developed land which would be
formed under a separate agreement of YLS DA prior to the commencement of
construction works for this Project, and no encroachment into any sites of
conservation importance is anticipated.
As such, no direct impact on natural habitats and sites of conservation
importance is anticipated. Similarly, no
species of conservation importance or fauna of particular concern (i.e. ardeids, waterbirds, wetland-dependent birds and
reedbed-associated birds) and their dependent habitats was recorded within the
Project site, thus no direct impact is expected. Species of conservation importance that
recorded in close proximity of the Project site, such as Luofushan
Joint-fir, Japanese Pipistrelle and Greater Coucal, are species that are more
tolerant of human disturbance and are well-adapted and commonly found in or
close to disturbed urban areas. Thus, indirect impact on these species is
anticipated to be minor.
13.2.5.22 Though
indirect impacts, in the form of construction disturbance and water quality
reduction, are anticipated, the ecological impact from these indirect impacts
is expected to be minor and low and no mitigation measures are required. Precautionary measures and enhancement
opportunities to further minimise any potential environmental impacts and to
promote the ecological value of the Project are recommended.
13.2.5.23 Ecological
monitoring is not required as no significant construction and operational phase
ecological impacts impact are anticipated.
Landscape and Visual Impact
13.2.5.24
The
Project will inevitably result in some landscape and visual impacts during
construction and operation phases. These impacts have been minimized through
incorporation of sensitive and aesthetic external designs of aboveground
Structures and appropriate landscape and visual treatments within site.
13.2.5.25
With
the implementation of the proposed preliminary mitigation measures, it is
considered that the residual landscape and visual impact will be reduced to an
acceptable level.
Hazard to Life
13.2.5.26
A
quantitative hazard assessment was conducted to evaluate the biogas risk to
existing, committed and planned off-site population due to operation of the
organic wastes co-digestion facility at the proposed
YLSEPP. Both the individual and societal
risk levels were found to meet relevant requirements stipulated in the 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. No adverse
impact is anticipated. Nonetheless,
implementation of good safety practices and recommended design measures are
recommended.
13.3.1.1
The
findings of this EIA have provided information on the nature and extent of
environmental impacts arising from the construction and operation of the
Project. The EIA has, where appropriate,
identified mitigation measures to ensure compliance with environmental
legislation and standards.
13.3.1.2
Overall,
the EIA Report has predicted that the Project would be environmentally
acceptable with the implementation of the proposed mitigation measures for
construction and operation phases. An
environmental monitoring and audit programme has been recommended to ensure the
effectiveness of recommended mitigation measures.