17.1 This EIA Report has provided an assessment of the potential environmental impacts associated with the construction and operation of the HATS Stage 2A Project. The assessment has been conducted, in accordance with the Study brief No. ESB-129/2005 under the EIAO for the Project, covering the following environmental issues:
n
Air Quality
n
Airborne Noise
n
Ground-borne Noise
n
Water Quality
n
Human Health Risk and Ecological
Risk
n
Waste Management Implications
n
Terrestrial Ecology
n
Marine Ecology
n
Fisheries
n
Landscape and Visual
n
Hazard to Life
n
Cultural Heritage
17.2
Air
quality impact from the construction of the Project has been modelled using the
FDM model. No exceedances of hourly
and daily TSP criteria to occur at ASRs in the vicinity during construction
with implementation of recommended watering frequency of work site. The dust suppression measures stipulated
in Air Pollution Control (Construction Dust) Regulation are recommended to be
implemented during construction of the Project. There would be no adverse residual air
quality impact due to the Project during construction phase.
17.3
Odour
emission from the PTWs and SCISTW would be the main concern during the
operation phase. Air dispersion
modelling (ISCST3) was conducted to simulate the potential odour impacts of the
SCISTW and the PTWs on the ASRs. All
the identified odour sources in the PTWs and SCISTW should all be properly
enclosed or covered, with the foul air drawn through deodorization units and
discharged after treatment. The
odour removal efficiencies of the proposed one stage and two stages
deodorization system should achieve 80% to 90% and 97% respectively as detailed
in this EIA study. Good house
keeping (regular cleansing schedule) should be conducted to minimize odour
generation from the PTWs and SCISTW.
With the proposed mitigation, the residual odour impacts at the ASRs
were predicted to be in compliance with the odour criterion. It is also recommended that odour
monitoring should be carried out during the operation phase to ensure that the
odour criteria are satisfied at the ASRs.
17.4
This assessment has predicted the construction noise impacts
of the Project during normal daytime working hours, taking into account other
concurrent projects including
17.5
Assessing against the noise
standard of 65 dB(A) during examination periods, the predicted noise level at
NSR N1 (i.e. Madam Chan Wai Chow Memorial School) would exceed the noise
standard by up to 5 dB(A), The on-site survey has revealed that NSR N1 has already been noise
insulated with air-conditioners, therefore no adverse noise impact would be
expected at the indoor environment. Notwithstanding this, it is recommended
that the particularly noisy construction activities should be scheduled to be
undertaken during the summer vacation period as far as practicable.
17.6
An indicative assessment has been undertaken for
possible construction activities within the tunnel and bottom of shaft during
restricted hours. Based
on information provided by the Engineer, no major items of PME except
ventilation fans and gantry crane would be operated above ground during
restricted hours (1900 to 0700 hours). The assessment results show that the
predicted construction noise levels at representative NSRs during restricted
hours would comply with the corresponding noise limits, provided that the ventilation fans and motors of
gantry at the production shafts of Sandy Bay PTW would be properly housed and
the silencers would be installed at outlet and inlet of the enclosure for
ventilation fans. It should be noted that the results of the
construction noise impact assessment for restricted hours are for indicative
purposes, the Noise Control Authority will process any CNP application based on
the NCO and the relevant technical memoranda in addition to considering the
contemporary situations / conditions.
17.7
A construction noise EM&A programme is recommended
to check the compliance of the noise criteria during normal daytime working
hours.
17.8
The
noise impact associated with the operation of the Project was assessed. For newly proposed equipment, the predicted noise levels at all
representative NSRs except N12, N13, N14, N15a, N15b, N16, N17 and N20 would
comply with the night-time planning noise criteria. The noise levels at these
affected NSRs would exceed the planning noise criterion by 1 to 13 dB(A). For
cumulative noise impact, the predicted noise levels at all representative NSRs
except N13, N15a and N15b would comply with the night-time ANL. The cumulative
noise level at N13, N15a and N15b would exceed the night-time ANL of 50 dB(A)
by up to 8 dB(A).
17.9
To mitigate the noise impact at
the affected NSRs, acoustic louvers have been proposed for air supply
fans/extraction fans of transfer pumping stations and ventilation fans of deodourization unit at
Sandy Bay PTW, Cyberport PTW and Wah Fu PTW. Besides,
it is recommended that the maximum allowable sound power level (SWL) of each
new transformer at Sandy Bay PTW shall be limited to 89 dB(A) during the
detailed design stage. With such proper designs, the predicted noise levels at
all representative NSRs would comply with both the night-time ANL and
night-time planning noise criteria. No residual operation noise impact arising
from the Project is anticipated.
17.10 Proper designs of PTWs, SCISTW and disinfection facilities would control the potential noise impact at noise sensitive receivers within acceptable levels, operational noise monitoring is not considered necessary.
17.11
The
major activities inducing potential groundborne noise impacts are from
operation of TBM and hydraulic breaker during tunneling and rock breaking. The
noise impacts on the closest sensitive receiver was assessed and the predicated unmitigated noise levels of TBM and hydraulic breaker were 33 and 34
dB(A) at the worst affected NSRs respectively which are well within the statutory requirements.
As such, all NSRs along the proposed tunnel alignment would not be adversely
affected by groundborne noise generated by the construction of the Project, and
mitigation measures as well as monitoring programme would not be necessary.
17.12
No groundborne noise would be
expected during operation of the Project and hence no mitigation measures would be recommended.
17.13 The general construction works for the Project would be land-based except seawall re-construction at the Aberdeen PTW. No dredging activities would be required for the Project. The fine content in the fill material during seawall re-construction at the Aberdeen PTW should be negligible. Key water quality issues associated with land-based construction would include the impacts from site run-off, sewage from workforce, accidental spillage and discharges of wastewater from various construction activities. With well maintained site drainage and the implementation of good site practices, impacts would be controlled to comply with the WPCO standards by implementing the recommended mitigation measures. No unacceptable water quality impact would therefore be expected.
17.14 Temporary bypass of sewage effluent via individual PTW would be required during the construction stage. The water quality impacts during the temporary sewage bypass were assessed using the Delft3D model. The predicted water quality impact associated with the temporary discharge would be short-term and the water quality would return to the normal condition quickly after the sewage bypass period. Water quality monitoring is recommended to be carried out during the temporary sewage bypass to quantify the water quality impacts and to determine when the baseline water quality conditions are restored. Also, a framework of the response procedures has been formulated to minimize the impact of temporary discharges. No insurmountable water quality impact would be expected.
17.15
The water quality impacts during
operation of the Project were assessed using the Delft3D model. Impacts
were assessed over a series of one-year simulation periods. The assessment area included the
17.16 The water quality modelling results showed that the Project would not cause any adverse impact on the marine water quality and on the identified sensitive receivers during normal operations of the SCISTW. The total residual chlorine from the chlorination/dechlorination disinfection process would meet the criterion set for the edge of the zone of initial dilution, with a large safety margin. Whole effluent toxicity tests showed that the chlorination/dechlorination disinfection process did not introduce additional toxic effects to the test organisms. A Post Project Monitoring (PPM) programme was proposed to confirm the model predictions made in this EIA.
17.17 Overflow at PTW may occasionally occur only during storm events and the extent of impact was predicted to be minor and acceptable. Mitigation measures, including dual power supply, standby pumps, treatment units and equipment, would be provided at SCISTW to minimize the occurrence of emergency discharge. Standby unit(s) and dual (backup) power supply would also be provided at all the Stage 2 PTWs to reduce the risk of equipment breakdown at the PTWs. The model suggested that the water quality impacts associated with power or equipment failure at SCISTW and the Stage 2 PTWs would be short term. The water quality would return to the normal condition quickly after the emergency sewage. In case of power outage of the dechlorination plant, the uninterruptible power supply (UPS) system to be provided would switch the power supply of the sodium bisulphite dosing pump to a backup battery almost instantaneously, allowing continuous dosage of sodium bisulphite for at least half an hour so that sufficient time can be provided for shutting down the chlorination plant to avoid the possibility of discharge of chlorinated effluent. An emergency contingency plan has been formulated to minimise the impact of emergency discharges and facilitate subsequent management of the emergency. An event and action plan and a detailed EM&A programme are recommended to collect water quality information and to mitigate the potential impact due to emergency discharge. The monitoring results shall be employed to identify areas for any further necessary mitigation measures to avoid, rectify and eliminate environmental damage associated with the Project.
17.18
A
detailed risk assessment was conducted to assess the potential adverse human
health and ecological effects that may result from exposure of toxic substances
due to HATS effluent discharge.
17.19
Potential
risk/hazard impact due to potential chlorination by-products and other
contaminants present in the chlorinated/dechlorinated HATS effluent would be
acceptable under established assessment criteria in all the three Project
Scenarios. According to the risk assessment results, the Project would not
cause unacceptable risk to human health.
Therefore, the Project would be considered to be environmentally
acceptable in terms of risks/impacts to human health.
17.20
Potential
risk to aquatic life due to CBPs present in C/D HATS effluent would be lower
than the screening value and considered acceptable. Cumulative risk assessment revealed that
CBPs and other pollutants present in the C/D HATS effluent, together with the
pollutants present in the ambient water, may induce a total hazard index level
above the screening value of 1.0.
It is noted that hazard index to aquatic life due to pollutants present
in the background already exceeds the screening value. Effluent discharge from SCISTW would
only induce low incremental risk (i.e. hazard quotient < 1) at edge of
mixing zone for all pollutants considered, indicating that concentration of
CBPs and pollutants would be complied with available local/overseas water
quality standards at the edge of mixing zone.
17.21
According
to USEPA (2005), the calculated HI exceeding the screening value would not
indicate that the proposed action is not safe or that it presents an
unacceptable risk. Rather, it
triggers further investigation.
Further investigation is carried out based on the results of WETT, which
is able to assess the impacts caused by aggregate toxic effects of the mixture
of pollutants in effluent.
17.22
Results
of WETT on C/D effluent are used to supplement the findings of ERA – Aquatic
Life and determine whether the C/D effluent would induce adverse effects to
aquatic life. Statistical analysis
of WETT data revealed that C/D process does not induce additional toxicity to
the sewage effluent. Also, it is
found that the established toxicity criteria are well complied with at both
edge of ZID and edge of mixing zone in all Project Scenarios. With the comfortable margin (about 4/5
of the toxicity criteria value) to the established toxicity criteria, it is expected
that the aquatic life present in the receiving water would not experience
unacceptable toxicity even taking into account the background seawater
conditions. This is supported by
the assessment results that concentration of all COCs would be complied with
available local/overseas water quality standards at the edge of mixing
zone. Therefore, the potential
risks due to C/D effluent imposed to aquatic life are expected to be
acceptable.
17.23
Potential
risk to marine mammals due to CBPs present in C/D HATS effluent would be lower
than the screening value and considered acceptable. Cumulative risk assessment revealed that
CBPs and other pollutants present in the C/D HATS effluent in all the three
Project Scenarios (Hazard Index from 0.126 to 0.129 for dolphins; Hazard Index
from 0.0757 to 0.0800 for porpoises) would also be lower than the screening
level and considered acceptable.
17.24
According
to the risk assessment results, the Project would not cause unacceptable risk
to ecological resources. Therefore,
the Project is considered to be environmentally acceptable in terms of
risks/impacts to marine ecological resources.
17.25 Waste types generated by the construction activities are likely to include C&D material (from excavation and tunnelling works), general refuse from the workforce, and chemical waste from the maintenance of construction plant and equipment. Provided that these wastes are handled, transported and disposed of using approved methods and that the recommended good site practices are strictly followed, adverse environmental impacts are not expected during the construction phase.
17.26
The main waste types to be
generated during the operation phase would be grit and screenings collected at
the upgraded PTWs and the SCISTW, and sewage sludge collected at the
SCISTW. The collection,
transportation and disposal practices of the grit and screenings would follow
the existing arrangements currently in operation at the PTWs and SCISTW. The dewatered sludge from the SCISTW
would be disposed of to the proposed Sludge Treatment
Facilities which would be commissioned in 2012 under the current planned
arrangement.
17.27
Literature review and recent reconnaissance visits on
terrestrial ecological resources identified seven habitat types within the
Assessment Areas of this Project, including developed area, wasteland,
woodland, plantation, shrubland, grassland and watercourse. The identified
natural woodland habitat were found to have moderate / moderate to high
ecological value while all other habitats, plantation woodland, shrubland and
grassland of low value, and developed area, wasteland and watercourse of very
low value.
17.28
Two sites of conservation importance, the existing Pok Fu
Lam Country Park and the coincided Pok Fu Lam Reservoir Catchment
Area Site of Special Scientific Interest (SSSI), falls partly within the
Assessment Area at
17.29
Three faunal species of conservation interest, including
Black Kite, Common Buzzard and Pallas’s Squirrel, were recorded in the
Assessment Areas during the recent visits of the Project. As all the three
fauna of conservation interest are not recorded within the project site / works
areas boundary, there would be no direct impact resulting from construction
works on these species of conservation importance. Hence, adverse impact on
these species of conservation importance was not expected.
17.30
The key direct ecological impacts of the Project would be
the habitat loss on
17.31
Other impact of the Project would be the removal (to be
transplanted / fell) of 376 trees
located within the footprint of the proposed project works. However, as
all of the affected trees are common and widespread species of low ecological
importance, potential impact to the vegetation was considered low. No protected
species or other flora of conservation interest would be affected under this
Project. Compensatory planting would
be provided in a ratio not less than 1:
17.32
With the proposed mitigation measures in place, including
noise mitigation measures and good site practice, indirect disturbance to
adjacent habitats and associated wildlife resulting from the construction noise
and human activities during the construction phase of the Project would be
mitigated to acceptable and minor level. No adverse indirect impact on those
habitat / species of conservation interest adjacent to the Project sites and
proposed works areas would be expected under this Project.
17.33
A
literature review of previous studies and EIA reports was initially conducted
to establish the baseline conditions of the Assessment Area. In areas that were
identified to be directly impacted by the project, i.e. Aberdeen PTW,
ecological surveys (intertidal and dive surveys) were conducted to gather up to
date, detailed information on the baseline condition of the affected site. The
assessment of potential impacts was then conducted in accordance with the EIAO
TM requirements.
Construction Phase
17.34
Few marine works are necessary
during the upgrade of PTWs however, indirect impacts on water quality may
result from site run-off, sewage from workforce, accidental spillage and
discharges of wastewater associated with land based construction activities. If
standard good site practice and the mitigation measures, proposed in Water
Quality Section 6, such as the use of silt/sediment and grease traps, effective
site drainage and provision of chemical toilets are implemented properly then
no significant adverse impact on water quality would be expected.
17.35
Although no marine works are
involved during the upgrade of the majority of PTWs, a small area of seawall
(approx.50m) would be demolished and reconstructed at the Aberdeen PTW site to
complete the construction works. As confirmed by dive surveys, the subject site
supported very limited marine life. Only 3 colonies of a common hard coral
species (Oulastrea crispata), all in
small size (3 to
Operational Phase
17.36
The water quality impact
modeling results in Section 6 indicated that the potential impact zone during
operation of the project would be restricted to the
17.37 However, it should be noted that exceedances of Total Inorganic Nitrogen (TIN) and Orthophosphate do occur in Southern and North Western WCZs which are outside the impact areas stated above. These WCZs are not considered to be impacted by the operation of the project because water quality modeling predicts similar levels of these nutrients with and without implementation of the project. Additionally, the ambient nutrient levels of Southern and North Western WCZ already exceed the relevant WQO/WQC suggesting that exceedances of WQO/WQC for these nutrients are likely due to non-HATS sources.
17.38 The existing SCISTW outfall location was chosen specifically to be in an area with low value ecological resources. No significant adverse ecological impacts are anticipated during operation of the Project because:
·
Disinfection process will result in improvement of water
quality with reduction in E. coli levels in Western Buffer WCZ and western
Victoria Harbour WCZ;
·
Only localized and small changes in TRC
·
No unacceptable ecological risk on marine mammal and marine
life in relation to acute and chronic effects;
·
Water quality criteria for unionized ammonia is met at the
edge of the ZID and this is out of the normal distribution range of dolphins,
porpoises and green turtles;
·
Unionized ammonia levels would be improved in the North
Western, Western Buffer and Victoria Harbour WCZ;
·
Oxygen depletion is minimal and highly localized around the
SCISTW outfall;
·
Improved DO levels in the
·
Highly localised salinity and temperature changes would not
have adverse impacts on the ecological habitats identified;
·
Increases in the levels of TIN and Orthophosphate predicted are
not significant enough to have direct impacts on identified ecological
communities;
·
There is no documented data on the specific conditions
leading to HABs and they have been documented in polluted and un-polluted
water. Increases in nutrient levels during discharge of sewage effluent would
be unlikely to trigger HAB events;
·
TIN and Orthophosphate levels have increased in the
Assessment Area since the implementation of HATS Stage 1, but no increase in
the number of HAB events has been observed;
·
Water quality modelling predicts little difference in levels
of TIN and Orthophosphate with or without the implementation of the project.
Additionally, with the implementation of HATS Stage 2B, TIN and phosphate
discharge will be reduced;
·
Western Buffer WCZ and western Victoria Harbour WCZ, the
areas affected by the effluent, generally support low to moderate ecological
resources;
17.39
Emergency
discharge of sewage effluent at PTW and SCISTW may occur during periods of
heavy rain when inflow exceeds the capacity of the system or as a result of
power/equipment failure. This would result in a rise in the level of E. coli in the receiving water body and
thus a subsequent deterioration in water quality which would potentially cause
adverse impacts to marine ecological resources. Water quality modelling showed
that pollution levels
for parameters such as nutrients and DO were not predicted to be adversely affected
by emergency discharges. Additionally modelling predicted that increases in the
level of suspended sediment resulting from emergency discharges would not
exceed the assessment criteria at coral sites. Water quality was also predicted
to return to normal condition 1 to 2 days after emergency discharges. Due to
the highly transient nature of potential emergency discharges and the ability
of marine organisms to naturally resist pathogenic strains of E. coli (Hang et al., 2000) no insurmountable impact on water
quality is predicted to result from emergency discharges.
17.40 Environmental monitoring and auditing requirements relevant to ecological resources protection are described in detail in the in the standalone EM&A Manual.
17.41
The
existing SCISTW outfall location was chosen in the area where fisheries
resources were considered to be of low value. No significant adverse fisheries impact is
anticipated
·
Improvement in water quality with
reduction in E. coli levels in
Western Buffer WCZ and western Victoria Harbour WCZ
·
Only localized and small changes
in TRC
·
No exceedance of unionized ammonia
levels, which can be toxic to fish
·
Oxygen depletion would be minimal
and highly localized
·
There is no documented data on the
specific conditions leading to HABs and they have been documented in polluted
and un-polluted water. Increases in nutrient levels would be unlikely to
trigger HAB events
·
TIN and Orthophosphate levels have
increased in the Assessment Area since the implementation of HATS Stage 1, but
no increase in the number of HAB events has been observed
·
Water quality modeling predicted
little difference in levels of TIN and Orthophosphate with or without the
implementation of the project
·
Water quality objectives would be
met at Ma Wan FCZ
·
Planned temporary bypass of sewage
during construction will be carried out during the dry season to avoid adverse
impacts on culture fisheries resources
·
Emergency discharges of sewage
effluent at SCISTW or PTW seawall bypass due to heavy rainfall or
power/equipment failure would only cause marginal exceedance of criteria value
for E. coli. However,
as the exceedances would only occur for a very short period (a few hours only),
non-compliance with the WQO/WQC for E.coli
(which is an annual geometric mean value) was not predicted. The emergency
discharge would be rare and very
short term, thus no insurmountable impact is expected on fisheries resources.
17.42 As there would be no significant adverse impacts on fisheries resources from the proposed disinfection or discharge of effluent during normal operation of the project, no fisheries specific mitigation measure would be required. Environmental monitoring and auditing requirements relevant to fisheries protection during emergency discharge of planned bypass of sewage are covered in the water quality assessment, Section 6, ecological risk assessment, Section 8 and the stand alone EM&A Manual.
17.43 The proposed scheme and associated works are predominated zoned as Other Specified Use (OU), Government, Institution or Community (GIC) or Open Space (O). Details OZPs and zoning of related site is listed in Table 13.2. It is considered to be compatible with the surrounding in principle following the planning intentions for the study areas as set out in the OZPs. There also have PTWs or work area located in the zone of open space and residenctial. Mitigation measures will be applied to avoid the adverse landscape and visual impacts in consideration with the surrounding environment.
17.44
Tree survey results indicated
that approximately 376 trees would be affected by the proposed works at the
PTWs, SCISTW and associated works areas.
No potential LCSD Champion Trees or Registered Old and Valuable Trees
are found. There are no rare species or endangered specie but common species.
All the trees with high amenity value which are unavoidably affected by the
works would be transplanted where possible. Detailed tree preservation,
transplanting and felling including compensatory planting proposals shall be
submitted to relevant government departments for approval in accordance with
ETWB TC no. 3/2006 and ETWB TCW No. 29/2004. Since trees would be planted within the PTWs/SCISTW
and works areas to compensate for the loss of existing trees, and roof greening
will be adopted for the provision of more greening to enhance the landscape
quality and waterfront character, the overall residual impacts on existing
trees are considered as slight with mitigation measures.
17.45 With implementation of mitigation measures during construction, there would still be some moderate adverse visual impact on the VSRs adjacent or close to the Project. Residual impacts on VSRs further away the works area would become slight to insubstantial.
17.46 With implementation of mitigation measures during operation, there would be slight adverse impact on VSRs facing the PTW site and associated structures. However, the residual impacts on remaining VSRs would become insubstantial.
17.47 Overall, it is considered that the residual landscape and visual impacts of the proposed development are considered as acceptable with mitigation measures during construction and operation phases.
17.48
Hazard to life impact
associated with the two
Potential Hazardous Installations (PHIs), namely the Hong Kong & China Gas
Company’s Gas Holder Depot and the Shell LPG Transit Depot/Bulk Domestic Supply
were quantitatively assessed. Mitigation and monitoring
measures have been proposed to reduce risk of adverse impact to PHIs.
17.49
Potential
damages to HKCG Gas Holder and Shell Depot can be avoided with implementation
of safety measures and close monitoring procedures during construction phase.
Operation of these PHIs would not be disturbed and gas supply would not be
disrupted provided that vibration and ground settlement caused by construction
works can be controlled within allowable limits. Societal risk for the HKCG Gas
Holder and the LPG
Compound can be maintained to acceptable
level throughout construction and operation phase of the Aberdeen PTW and Ap Lei Chau PTW. Frequency of accidents for the LPG Transit
Depot does not increase during construction of Ap Lei Chau PTW. However,
installation of gas detection system can bring the risk level further down as
an early warning to safeguard construction workers at the project site. Both
17.50
Given
that there would be no overnight explosives storage expected according to the
latest construction programme, the hazard assessment for overnight storage of
explosives is considered not applicable in this EIA.
17.51
Hazard to life impact
associated with the proposed disinfection facilities at SCISTW was
quantitatively assessed, with consideration of identified precautionary
measures/ operation procedures that minimize the risks associated with the
chemicals related operations. The
individual risk and societal risk associated with the chemicals related
operations were found to be acceptable in accordance with the risk guidelines
stipulated in the Annex 4 of the EIAO TM.
Hence, the hazard to life impact due to the proposed disinfection
facilities at SCISTW is considered to be low and acceptable.
17.52
Based on the desk-based study and field
survey findings, none of the heritage resources would be directly impacted by
the proposed project. Indirect impacts that have been identified would arise
from blasting for tunnel, shafts, effluent conveyance system and disinfection
facilities. Recommendations for limiting the peak
particle velocity to 25mm/s have been set for historical structures. A
monitoring programme will be set in place by the Project Proponent to
ensure that the limits are kept within acceptable limits
during blasting for tunnel, shafts, effluent conveyance system and disinfection
facilities in the vicinity of the buildings/structures.
17.53 The findings of this EIA Study have determined the likely nature and extent of environmental impacts predicted to arise from the construction and operation phases of the Project. Where appropriate, the EIA has identified mitigation measures to ensure compliance with environmental legislation and standards. The feasibility, practicability, programming and effectiveness of the mitigation measures have been assessed and determined.
17.54 Overall, the EIA Study for the proposed HATS Stage 2A has predicted that the Project, with the implementation of the proposed mitigation measures for construction and operation phases, would comply with all applicable environmental standards and legislation. This EIA has also demonstrated the acceptability of the residual impacts from the Project and the protection of the population and environmentally sensitive resources.
Table 17.1 Summary of Key Environmental Outcomes / Benefits
|
Area/Issue |
Environmental
Outcomes / Benefits |
|
Major environmental benefits of the Project |
· The current design scheme
to collect sewage from upgraded PTWs through deep tunnel system for
centralised treatment at SCISTW would provide the following major benefits in
terms of the pollution loading reduction: -
Prevent another 190 to 500 tonnes of sewage sludge
(depending on sewage quantity) from being dumped into the harbour each day -
Reduce toxic ammonia by 10% on average -
Reduce total inorganic nitrogen and phosphorus by 5% and
8% respectively -
Increase dissolved oxygen levels by 5% · As part of Stage 2A, advanced
disinfection facilities by means of chlorination/ dechlorination can reduce pathogen
discharge from un-disinfected effluent and enable the closed Tsuen Wan
beaches to be re-opened at the earliest opportunity. · Overall, the project can
significantly improve baseline water-quality conditions compared to the
scenario of “no HATS Stage |
|
Environmentally friendly designs recommended
Key environmental problems avoided |
SCS Alignment Design
& Construction · Deep tunneling instead
of open trench excavation for the SCS construction can minimize significant
environmental, community and traffic impacts in dense urban areas during
construction stage. · Tunnel alignment to be
running offshore can minimise impacts on land-based environmental sensitive
receivers. · Curved alignment design can:- -
Avoid passing through reclaimed lands with sensitive
structures/old built-up areas so that heritage resources can be protected
from vibration impacts. -
Avoid encroachment on private lots and thereby eliminates
interfaces with private properties. This would be resulting in reduction of
programming risk and hence duration of environmental impacts to the public. · Design with minimised
tunnel excavated span can reduce waste generation. · Either drill & blast
or mechanical boring methods will be the major tunnel construction method. Recommended
measures e.g. control of quantity of explosives or speed of mechanical boring
can effectively control vibration, groundborne noise impacts and ground
settlement due to groundwater ingress. PTW & SCISTW Design
& Construction · Enclosed sewage treatment
units with exhaust air control can minimize odour and noise impacts during
operation stage. · Landscape and aesthetic considerations
incorporated to the PTW/SCISTW design can minimise visual impacts and to
beautify the landscape of the local environs, especially for the PTWs located
along the harbour-front. · Adjusted/oriented footprints
of proposed sewage treatment facilities to reduce conflict with the existing
trees. · Effluent conveyance
system at SCI proposed as a deep tunnel can reduce environmental impacts e.g.
dust, noise & visual compared to the open trench excavation method. · Non-percussive bored
pile techniques proposed for PTW/SCISTW construction can minimise noise and
vibration impacts. · Construction works or
packages for PTWs/SCISTW in phases can minimize magnitude of the construction
stage impacts e.g. noise and dust. |
|
Air Quality |
Environmental benefits of environmental protection
measures recommended · ASRs identified near the
construction sites are protected through implementation of dust suppression
measures i.e. regular watering during construction phase. · ASRs identified near the
PTWs and SCISTW are protected from the following proposed odour control measures
during operation phase: -
Properly enclosed or covered the identified odour sources -
Foul air drawn through deodorization units and discharged
after treatment by biofilter and/or activated carbon -
Good house keeping (regular cleansing schedule) to
minimize odour generation Population and
environmental sensitive receivers protected · Existing ASRs &
planned developments, including residential, commercial and recreational
areas within 500m from SCISTW and PTWs. |
|
Airborne Noise |
Environmental benefits of environmental protection
measures recommended · NSRs are protected with implementation
of quiet PME, movable barriers, acoustic mats as well as good site practices
during construction stage. The predicted mitigated noise levels complied with
the noise standards at all NSRs except N1 ( · At N1, the proposed
mitigation measures already reduced the noise level from 78 dB(A) to 70
dB(A). It only exceeded the noise limit 65dB(A) during exams period. Particularly
noisy construction activities were recommended to be undertaken during summer
vacation period to further reduce the construction noise impact. · Acoustic louvers were
proposed for air supply fans/extraction fans of transfer pumping stations and
ventilation fans of deodourization unit at Sandy Bay PTW, Cyberport PTW and
Wah Fu PTW. Besides, it is recommended that the maximum allowable sound power
level (SWL) of each new transformer at Sandy Bay PTW shall be limited to 89
dB(A) during the detailed design stage. With proper designs of PTWs, SCISTW
and disinfection facilities, no residual operation noise impact is
anticipated. Population and environmental sensitive receivers
protected · Existing
and planned NSRs within |
|
Water Quality |
Environmental benefits of environmental protection
measures recommended · Control
construction site runoff and various construction activities as outlined in ProPECC PN 1/94 Construction Site Drainage
would reduce the water quality impact to an acceptable level. · The
Project would bring water quality improvements at the identified water
sensitive receivers including the beaches, the fish culture zones (FCZ) and
the secondary contact recreation subzones as well as the seawater intakes in
western · Operation of HATS 2A
would result in water quality improvements at the identified water sensitive
receivers, including the beaches, the fish culture zones (FCZ) and the
secondary contact recreation subzones as well as the seawater intakes in
western Victoria Harbour as the pollution levels for all the concerned
parameters including all the concentration of nutrients in the receiving marine
water bodies would be reduced. · Provision
of dual power supply and standby facilities proposed at the SCISTW and PTWs can
minimize the potential water quality impacts upon the water sensitive
receivers due to emergency discharge. · In
case of total power outage of the dechlorination plant, the uninterruptible
power supply (UPS) system to be provided would switch the power supply of the
sodium bisulphite dosing pump to a backup battery almost instantaneously,
allowing continuous dosage of sodium bisulphite for at least half an hour so
that sufficient time can be provided for shutting down the chlorination plant
to avoid the possibility of discharge of chlorinated effluent. · With
proper implementation of these mitigation measures, the occurrence of
discharge of non-dechlorinated effluent would be very remote. In case that the dechlorination
process fails, the chlorination process could be practically stopped within
30 minutes to avoid discharge of total residual chlorine into the marine
water. Population and environmental sensitive receivers
protected · All the water sensitive
receivers identified in the Western Buffer, North Western, |
|
Human Health Risk and Ecological
Risk |
Environmental benefits of environmental protection
measures recommended · Chlorination by-products
present in the HATS effluent would not induce
unacceptable human health risk and ecological risk. · A
monitoring programme would be implemented to protect human health and
ecological resources from increased TRC and CBP concentrations in seawater. Population and environmental sensitive receivers
protected · Population
and ecological resources associated with the exposure to toxic substance from
effluent discharges of the Project. |
|
Waste Management Implications |
Environmental benefits of environmental protection
measures recommended · On-site
re-use of excavated materials, e.g. backfilling of trenches for SCISTW
expansion, would reduce waste generation. Grade I/II granite generated form SCS
construction delivered to Lam Tei Quarry would be crushed as aggregates,
other surplus inert C&D material delivered to public filling reception facilities
can be reused for other projects. · Implementation
of the proposed waste control and mitigation measures would avoid the
potential water quality, dust, odour,
and noise impacts associated with handling, transportation and disposal of
the identified wastes arising from the Project. Population and environmental sensitive receivers
protected ·
Water quality, air, and noise
sensitive receivers at or near the Project site, the waste transportation
routes and the waste disposal site. |
|
Terrestrial Ecology |
Environmental benefits of environmental protection
measures recommended · All construction works
would be confined to very low-valued habitats (developed area and wasteland)
and potential direct impact to nearby habitats of ecological importance would
be avoided. · Noise and dust control
measures would minimise indirect impact on adjacent terrestrial
habitats and associated wildlife during the construction phase. Compensation areas included · Direct loss of ~376 individual
trees would be mitigated by compensatory planting of similar native species
at not less than 1:1 ratio in terms of quality and quantity Population and environmental sensitive receivers
protected · Terrestrial ecological
resources near the Project site |
|
Marine Ecology |
Environmental benefits of environmental protection
measures recommended · All the marine habitats
and associated flora and fauna that would be directly impacted due to this
Project are considered to have low ecological values. · Coral colonies at
Aberdeen PTW (only 3 colonies found, all small size, low coverage and
attached on moveable boulder) that would be directly affected would be
translocated to nearby suitable habitats. Coral translocation and
post-translocation monitoring will be carried out to further protect the
corals. This would mitigate the direct impact imposed on these corals as a
result of the project. · Water quality control
measures would minimise potential indirect impacts on marine habitats and
associated life throughout the study area that may result from a
deterioration of water quality during construction. Compensation areas included · Intertidal habitat (seawalls)
directly affected by construction works at Aberdeen PTW would be
reconstructed. Population and environmental sensitive receivers
protected · Ecological resources at
and near the Project site. |
|
Fisheries |
Environmental benefits of environmental protection
measures recommended · Fisheries resources
would be protected by implementation of water quality control measures Population and environmental sensitive receivers
protected · Fisheries resources at
and near the Project site. |
|
Landscape and Visual |
Environmental benefits of environmental protection
measures recommended · Landscape and visual
sensitive receivers would be protected by implementation of the measures, such
as tree transplantation, compensatory tree planting, control of light-time
lighting and erection of decorative screen hoarding compatible with the
surrounding setting during construction phase. · Mitigation measures such
as aesthetic design of PTW / SCISTW and associated structures; shrub and
climbing plants to soften proposed structures; buffer tree and shrub planting
to screen proposed associated structures etc. would lessen the landscape &
visual impacts to the sensitive receivers during operation stage. Compensation areas included · Compensatory planting for
loss of ~376 trees would be equal or not less than 1:1 ratio within the
Project Boundary or proximity areas. Population and environmental sensitive receivers
protected · All VSRs identified
within the Zone of Visual Influence from the Project. |
|
Cultural Heritage |
Environmental benefits of environmental protection
measures recommended · Control of vibration
limit through a monitoring programme to protect historical structures against
groundbourne vibration generated from construction activities e.g. tunnel
blasting. Population and environmental sensitive receivers
protected · Heritage resources
identified close to the Project site which are sensitive to vibration damage. |
|
Hazard to Life |
(i) Assessment for Potential Hazardous
Installations (PHIs) Environmental benefits of environmental protection
measures recommended · With implementation of
safety measures and close monitoring procedures, vibration and ground settlement
caused by construction works can be controlled within allowable limits.
Operation of HKCG Gas Holder at Population and environmental sensitive receivers
protected · Construction workers at
the Project work sites and population in vicinity of HKCG Gas Holder and
Shell Depot. (ii) Assessment for Disinfection
Facilities Environmental benefits of environmental protection
measures recommended · Implementation of the
proposed precautionary measures including special arrangement on chemicals-related
operations to avoid chemical unloading errors and mitigation measures during
construction phase would minimize the risks to acceptable level. Population and environmental sensitive receivers
protected · Population near the
SCISTW. |