Issue
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Mitigation
Measures and Environmental Outcomes/Benefits
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The
Project
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Provision
of a new sewage collection, treatment and disposal facilities for Sok Kwu Wan
area in order to:
·
Eliminate the direct discharges of untreated or
partially treated sewagegenerated from approximately 1300 residents, 6000 day
visitors and restaurants in Sok Kwu Wan area into coastal area of Picnic Bay
in 2016 (which are equivalent to the ultimate population figures) as well as
from Lo So Shing and Mo Tat Wan which would have total residents of
approximately 532 in 2016.
·
Improve the water quality of Picnic Bay.
·
Improve the local environment in the residential
areas by eliminating unhealthy, malodorous and potentially visually
unpleasant surface discharges.
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Option
Selection & Design
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The
locations and design of the proposed sewer alignment, pumping stations, STW
and submarine outfall are considered environmental friendly due to the
following reasons:
·
Avoid or reduce impacts on sites of
archaeological interest and cultural heritage importance (Lo So Shing
Archaeological Site).
·
Avoid reclaiming land for STW construction.
·
Reduce the risk of untreated sewage leakage by
selecting the route with shorter pipeline on land.
·
Minimizethe encroachment into private lot and the
LCSD playground.
·
Minimize the loss/disturbance of vegetated areas.
·
Avoid direct impact on coral habitats with the
use of HDD.
·
Minimize potential water quality impacts on
nearby sensitive receivers by extending the outfall length, eliminating the
need of reclamation, and using of no-dig method for inshore section of the
outfall pipeline.
·
Improve water quality of Picnic Bay by
eliminating the discharge of untreated or partially treated sewage and
providing a full secondary treatment with nitrogen removal and UV
disinfection unit.
·
Minimize the extent of construction dust and
noise impacts (i.e. the selected route would avoid affecting the receivers in
Lo So Shing)
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Air
Quality –Construction Phase
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2m high
solid fence around construction site of Pumping Station P2 and dust
suppression measures stipulated in Air Pollution Control (Construction Dust)
Regulation are proposed to protect the nearby ASRs.
All ASRs
would be protected to comply with AQQ and EIAO-TM standards.
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Air
Quality –Operation Phase
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All
pumping stations, sequence batching reactor (SBR) feed pump station and
sludge dewatering room would be enclosed and installed with deodorisation
facilities.
All ASRs
would comply with of EIAO-TM odour standard.
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Noise –
Construction phase
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Use of
quieter plants, limiting number of some powered mechanical equipment, use of
noise screening structures and manual working method are proposed to protect
the NSRs located near the pumping stations and along the sewer alignment.
All NSRs
comply with EIAO-TM noise standards, except short-term residual impact during
sewer construction.
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Noise –
Operation phase
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Installation
of a silencer with at least 8 dB(A) noise reduction at Pumping Station P1a is
recommended.
All NSRs
would be protected to meet both daytime and nighttime noise criteria.
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Water
Quality – Construction Phase
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Use of
HDD for the inshore section outfall pipeline installation, reduction of
dredging rate and use of 2-layer silt curtains are recommended to protect the
FCZ at Picnic Bay and secondary contact recreation subzone at Mo Tat Wan.
The FCZ
and secondary contact recreation subzone would be protected to be within the
relevant WQO.
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Water
Quality – Operation Phase (Normal Operation)
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Provision
of full secondary treatment with nitrogen removal and UV disinfection and
disposal of treated sewage at a long submarine outfall near the mouth of
Picnic Bay.
The FCZ
and secondary contact recreation subzone would comply with WQO, except WQO
limit for TIN due to the high background level which has already exceed the
limit. The predicted TIN levels would fall within the background
variations of TIN levels at Picnic Bay.
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Water
Quality – Operation Phase (Emergency Discharge)
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Mitigation
measures such as provision of standby pump and standby generator, 24-hour
temporary storage and contingency measures are recommended to minimize the
occurrence of emergency discharge and potential water quality impact if an
overflow does occur, in order to protect the FCZ at Picnic Bay.
With the
implementation of the recommended mitigation measures and contingencies, the
occurrence of emergency discharge and the residual impacts in the unlikely
event that an overflow does occur would be minimised.
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Ecology
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Use of
HDD for the inshore section of outfall pipeline would avoid the loss of coral
habitats and reduce the temporary seabed loss due to dredging.
Fencing
and labelling of uncommon tree species is proposed to avoid direct or
indirect disturbance during construction.
No
significant and unacceptable residual impact would be expected.
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Fisheries
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With the
implementation of the mitigation measures recommended for the water quality
impact, no unacceptable residual impact on fisheries would be expected.
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Landscape
and Visual Impact
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Appropriate
construction practice, design and surface treatment of the built elements and
appropriate soft landscape treatment within available areas of the Project
are recommended to mitigate the potential landscape and visual impacts.
Landscape
and visual impacts would be acceptable with the recommended mitigation
measures.
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