This EIA has focused on identifying and providing mitigation options for the potential impacts associated with the construction and operation of the 132kV circuit from Pui O Substation to Cheung Chau Substations.
The following aspects have been assessed:
· Construction Impacts including Air Quality, Noise and Water Quality;
· Waste Management Implications;
· Human Health;
· Ecology;
· Cultural Heritage; and
· Landscape and Visual Impacts.
The residual impacts define the acceptability of the project, and are categorised in general accordance with guidance offered by the Technical Memorandum on Environmental Impact Assessment Process (EPD, 1997). Five impact categories have been adopted:
· The impact is beneficial if the project will improve the overall quality of the environmental aspect under consideration;
· The impact is acceptable if the assessment indicates that there will be no significant effects on the environmental aspect under consideration;
· The impact is acceptable with mitigation measures if there will be some adverse effects, but these can be eliminated, reduced or offset to a large extent by specific measures;
· The impact is unacceptable if the adverse effects are considered excessive and are unable to be practically mitigated. In these circumstances compensation may have to be considered by Government; and
· The impact is undetermined if significant adverse effects are likely, but the extent to which they may occur or be mitigated cannot be determined from the study. Further detailed study will be required.
The time scale over which the impacts will occur has also been categorised into short, medium or long term, and reversible or irreversible. No residual impacts are expected.
A
quantitative assessment on the construction dust impacts has identified that
fugitive dust is the primary potential air pollutant during the proposed works.
The assessments predicted an exceedance of hourly TSP dust criteria at the
hostel, SR4 for the situation where no mitigation measures were in place. With the application of the established and
practical dust suppression techniques such as regular watering twice a day,
covering/dampening any stockpiles and dampening dusty materials before
transportation and the control measures stipulated in the Air Pollution Control
(Construction Dust) Regulation, the construction dust impacts can be reduced by
more than 50% to an acceptable level.
No residual air quality impact is expected. As a result, no routine air quality monitoring is recommended.A qualitative
assessment on the construction dust impacts has identified that fugitive dust
is the primary potential air pollutant during the proposed works and the dust
impact will be minimal. Established
dust suppression techniques such as regular watering, covering/dampening any
stockpiles and dampening dusty materials before transportation, have been
proposed. Through the proper
implementation of the recommended mitigation measures, dust generation will be
further controlled and exceedance of the acceptable criteria will not be
expected. As a result, no routine air
quality monitoring will be required.
The
unmitigated noise levels associated with the installation of underground cable
and construction of cable tunnel would cause exceedance of the daytime
construction noise criterion at the nearby NSRs. The most seriously affected
area is Ham Tin Tsuen of Pui O, Lantau where unmitigated noise level of up to
92 dB(A) is predicted. Therefore, adequate control measures will be necessary
for the installation of underground cable and construction of cable tunnel.
Mitigation measures including the use of quiet plant and consideration of
barrier effect are proposed to substantially minimise the noise level. Although
the noise impact at all NSR would comply with the daytime construction noise
criterion (i.e. 75 dB(A) for domestic premises), the Buddhist Wai Yan Memorial
College (i.e. SR6) would still exceed the noise criteria (i.e. 70 dB(A) for
schools) by 5 dB(A). By considering the short duration of this residual impact,
re-scheduling the construction works at SR6 on Saturday (non-teaching period)
or school holidays could minimise the noise impacts. Therefore, the residual
noise impact could be alleviated.
For the construction of the tunnel, numerous of
noisy PMEs such as drilling machine and rock bolt are involved. Construction
noise impact at the nearby NSRs is expected. With the erection of the temporary
vertical noise barrier at Pui O tunnel portal and adoption of quiet plants, the
construction noise impact can be alleviated., The predicted noise levels with mitigation can comply with the
noise criteria.This EIA has concluded that the predicted
construction noise levels without mitigation at all the affected NSRs except
for SR3 will exceed the acceptable noise criteria. With the implementation of
good site practice and practical noise mitigation measures, the construction
noise impacts will be reduced.
After the implementation of
noise mitigation measures, residual construction noise impact will only occur
at SR5, the Buddhist Wai Yan Memorial College. However, it is anticipated that
the exposure to high noise level is only a short duration (2 to 3 days). In
addition, the road breaking activity in front of the school is recommended to
be carried out during the non-teaching period of the school (i.e. Saturday
afternoon and school holidays). The residual impact can be mitigated.
As noise exceedances during
the construction phase are not predicted and the laying underground land cable
is a trade practice well established by CLP, routine environmental noise
monitoring is not required during construction. However regular site audits are
recommended to be conducted to ensure the implementation of good site practice
and appropriate mitigation measures.
It may be concluded that for direct burying method,
short term exceedances of peak elevated SS levels take place especially during
dry season. At Po Yue Wan these occur on neap tide for both the “slow” and
“fast” advancing rates although it should be noted that average results fully
comply with the WQO’s. No short term
exceedances occurred any of the sensitive receivers rather they are, not
unexpectedly, observed in the Adamasta Channel and a Po Yue Wan which is not a
water sensitive receiver.
Although the water quality impact is acceptable, it
has been proposed that a “rest” period of 6 hours should be observed between
the completion of one cable burying operation (by boat) and commencement of the
next cable laying operation. The 6 hour
period is based on the time taken for the sediments to resettle to acceptable
levels as shown in the time history plots in Appendix F. Reference should be made to these plots
relating to the Adamasta Channel and Po Yue Wan where peak concentrations are
observed.
No exceedances of SS levels at all the monitoring
locations are predicted with dredging one trench or three trenches
simultaneously. Therefore, the water quality impact is acceptable.
Water
quality impacts associated with the implementation of this Project are
acceptable.
Direct
burying is the preferred option for the cable laying as it is of shorter
duration than dredging, has lesser and acceptable impacts than dredging and can
fully comply with the WQO’s at the sensitive receivers all year round.
Full
compliance with the WQO’s (throughout the year) has been predicted for the direct burying option,
although confirmatory monitoring is proposed to ensure water quality at Tai
Kwai Wan and Cheung Sha Wan Fish Culture Zone is not impacted by the cable
laying works.
Dredging
will not be carried out for laying the entire length of the cables. Instead, minor dredging works need to be
carried out for laying either end of the cables (due to the shallow depth of
water). The results indicate that the
WQO’s can be achieved if the single trench dredging option is carried out
during the dry season.
For the minor
dredging works which need to be carried out for laying either end of the cables
(due to the shallow depth of water) the results indicate that the WQO’s can be
achieved if the single trench dredging option is carried out during the dry
season.
In
the event that dredging needs to take place during the wet season (eg for
reasons of programming) then practical mitigation measures will be needed to
ensure compliance with the WQO’s. For the single trench option mitigation
measures including the use of closed and sealed grabs and through controlling
the rate of lifting will ensure the WQO’s can be achieved.
In
the event that a three trench dredging option is considered then mitigation
measures would need to reduce the impacts by 40% during the dry season (through
the use of closed grabs) and by 85% during the wet season (using closed grabs,
controlling the rate of lifting and reducing the dredging rate by a further
40%). All of the foregoing are practical measures which can be adopted to
ensure compliance with the WQO’s.
For
the high concentration observed within the typhoon shelter of Cheung Chau Wan
the potential impacts are over-exaggerated because the work carried out in the
typhoon shelter will be carried out by hand using qualified divers. Therefore
the impacts will be significantly less than predicted by the model and no
adverse water quality impact is expected.
The construction programme has scheduled the cable laying work during the dry season. The results of the assessment confirm that cable laying work can be carried out without any adverse water quality impact during the dry season. Even cable laying work is required during the wet season, the water quality can also comply with the WQO with the implementation of the above-mentioned mitigation measures.
The
potential impacts from off-site runoff can be controlled to acceptable levels. There will be no adverse impact
on water quality arising from the temporary working platform at Pui O. The
facility is only required for the excavation of the tunnel. The working
platform is small (180m2) and will be formed behind a seawall of
concrete blocks with no gaps. Once the excavation has been completed the
working platform will be removed and the shoreline reinstated.
An
environmental monitoring and audit will be implemented to ensure the general
mitigation measures are effective and that the actual water quality impacts are
within the acceptable levels during the installation of submarine cables and
the temporary working platform at Pui O Beach.Water quality impacts
associated with the implementation of this Project are acceptable.
Direct burying is the preferred option for the cable
laying as it is of shorter duration than dredging, has lesser and acceptable
impacts than dredging and can fully comply with the WQO’s at the sensitive
receivers.
Full compliance with the WQO’s has been predicted for the direct burying
option, although confirmatory monitoring is proposed to ensure water quality at
Tai Kwai Wan and Cheung Sha Wan Fish Culture Zone is not impacted by the cable
laying works.
For the single trench dredging option the results
indicate compliance with the WQO’s at the sensitive receivers except during the
wet season at Tai Kwai Wan. Practical mitigation measures can be implemented to
reduce impacts to acceptable levels.
In the event that a three trench dredging option is
considered then mitigation measures would need to reduce the impacts at Cheung
Sha Wan fish Culture Zone to allow dredging during the dry season. For the wet
season, mitigation measures would need to include reduction in losses of
sediments (at least 50%) as well as the use of a silt curtain at Tai Kwai Wan to
ensure compliance at Tai Kwai Wan.
The potential impacts from off-site runoff can be
controlled to acceptable levels. Work at Pui O in respect of the tunnel
excavation will not have an adverse impact on water quality as the working
platform is small, a temporary facility and the area will be formed behind a
seawall of concrete blocks with no gaps.
An environmental monitoring and audit will be
implemented to ensure the general mitigation measures are effective and that
the actual water quality impacts are within the acceptable levels during the
installation of submarine cables and the temporary working platform at Pui O
Beach.
It can conclude that for direct burying method,
exceedances of SS levels take place only at Po Yue Wan during wet season neap
tide. Since Po Yue Wan is not a water
sensitive receiver, the predicted SS levels at all the water sensitive
receivers comply with the relevant WQO. Therefore, the water quality impact is
acceptable.
No exceedances of SS levels at all the monitoring
locations are predicted with dredging one trench but exceedances occur at
Cheung Chau typhoon shelter, Po Yue Wan and Adamasta Channel when three
trenches are dredged simultaneously. With the implementation of the general
mitigation measures and pollution prevention measures, the water quality
impacts at the water sensitive receivers are not expected.
An environmental monitoring and audit will be
implemented to ensure the general mitigation measures are effective and that
the actual water quality impacts are within the acceptable levels during the
installation of submarine cables and the reclamation works at Pui O Beach.
A review of existing
information indicates that the Study Area supports fisheries resources and fishing operations. As impacts resulting from the project will be
confined to dredging and reclamation, no adverse impacts to fisheries resources
are expected.Impacts
from the project will be confined to reclamatiothe formation of the
temporary working area and more specifically the cable laying works. As the working
platform is a temporary facility which will be removed to re-instate the shoreline following
completion of the excavation works, and the preferred method for cable laying
is direct burying for reasons given in the foregoing section, the
extent of the impacts on fisheries are likely to be minor. n The potential impact on
the spawning and nursery ground is anticipated to be insignificant. and the chosen method of cable laying/protection
which may be by dredging or by direct burying.
The size of impact due to dredging and reclamation is predicted to be minor.
Generally, the
mitigation measures which are recommended to control water quality impacts to
within acceptable levels, are also expected to control impacts to fisheries
resources. In
addition to which, appropriate mitigation measures are proposed to minimise the such as adoption of dimpacts of the works
on the marine environment.
irect burying as the preferred cable laying method
and using shield over the face of the cutter to suppress the release and
dispersion of sediments to the water column.
Therefore, no fisheries-specificspecial
mitigation measures are required.
Terrestrial Ecology
Altogether 15 habitat types were found in the Study
Area, including forest, tall shrubland, shrubland-grassland mixture, wetland,
abandoned farmland, farmland, rocky shore, sandy shore, backshore shrubland,
mangrove, brackish mudflat, plantation, wasteland, village area and
stream. Based on the ecological
conditions presented in the above sections, it is considered that the forest,
wetland and mangrove have high ecological value. The brackish mudflat, abandoned farmland, tall shrubland, stream
(S1 to S4) are regarded as having moderate ecological value, while the other
terrestrial habitats are common and typical habitats in Hong Kong and most of
the species identified are common and widespread and therefore considered to be
of low ecological value.
The proposed 132 kV circuits will mainly be located
on existing road/ footpaths. The
impacts due to the construction and operation of the underground cable are
considered to be low, and no adverse residual impact is expected. The most sensitive issue is the direct
habitat loss (0.15 ha of tall shrubland) within the South Lantau
Country Park, in which no unacceptable residual impact will be expected. Mitigation measures in the form of good
construction practice and scrub compensatory planting are recommended to
minimise potential disturbance to the surrounding environment.
Marine Ecology
Literature reviews of
existing information supplemented with the results of recently undertaken field
surveys on marine ecological resources indicate that the intertidal rocky
shores within the Study Area are of medium ecological value whereas for the
sandy habitats, low ecological value was assigned. Soft bottom subtidal habitats identified in the review were
regarded as of low ecological value. A
few isolated colonies of hard and soft corals were recorded on the subtidal
hard surface habitats and were considered as of low ecological value. The waters near the proposed reclamationtemporary working
platform and submarine cable laying sites do not appear to be highly
utilised by marine mammals and it is considered that this area does not contain
critical habitat for the Indo-pacific Hump-backed dolphins and Finless
Porpoises.
Potential impacts to marine
ecological resources from the proposed construction works may arise either
indirectly, e.g. through perturbations of the surrounding water quality, or
directly as a result of habitat loss. A
temporary
loss of 180m2
total of 0.055 ha intertidal sandy
shore habitat and some, small areas of rocky shore and a permanent loss of 0.5
ha of subtidal soft bottom assemblages will be permanently lost as a resulted from of the construction activities associated
with the Project. However, the
assemblages to be lost are of low-medium ecological value and given the small
area to be directly affected, the impacts are unlikely to be severe. Indirect impacts during the construction
process, such as an increase in SS levels and decrease in DO in the water
column may impact intertidal and subtidal filter feeders and other marine
organisms. However, the effects are not
expected to be severe and no unacceptable impacts are predicted to occur.
Operational impacts to
marine ecological resources are not predicted to occur through disturbances to
water quality due to changes in the hydrodynamic regime of the area or an
increase in marine traffic for cable maintenance and repair.
Literature reviews of
existing information supplemented with the results of field surveys on cultural
heritage resources indicate that 31 historical buildings and features and two
known archaeological sites are located within the Study Area. The proposed development has tried to avoid
the heritage sites as far as possible but concerns have been raised regarding
the potential impact on some of the identified sites.
Mitigation measures have
been recommended to avoid impacts to cultural heritage resources; control of
the construction work schedule during peak visiting hour at Pui O Tin Hau
Temple; detail design of the underground cable construction to avoid and
minimise the potential impact to the archaeological deposit at Bui O Public
School (Site A) and inner raised beach at Pui O (Site B). The future road level of the proposed Chi Ma
Wan Road widening shall be raised to allow adequate cover requirement for the
cables which shall be laid above the concerned zone. If the avoidance of
reaching the `no dig’ zone below existing ground level at both Site A and Site B is not
possiblePui O
Archaeological Site is not possible, archaeological monitoring should be
undertaken in this section during construction to preserve the archaeological
deposit, if any, by record and take environmental samples for future study if
necessary. The level of
`no dig’ zone shall be agreed with AMO during the detailed design stage of the
cable laying works. The construction contractor
should cooperate with a qualified archaeologist appointed to undertake the
monitoring to allow sufficient time for recording archaeological deposit and
take environmental samples if necessary.
The Landscape and Visual
Impact Assessment highlights that the significant adverse impacts will occur
during the construction phase. Significant impacts are also restricted to
particular locations, namely Pui O tunnel and Tai Long Wan tunnel portals and Cheng Cheung Chau landfall
area. The disturbed
coastline at the
temporary reclaimed workings platformareas
at Pui O tunnel portal and the temporary access for delivery of materials at Tai
Long Wan Landfall area will be reinstated to the existing coastline after
construction. With mitigation measures, mentioned in Section 8.8, With
mitigation measures the long term adverse impacts will be
negligible. The alignment of the circuit is significantly constrained by the
technical engineering requirements.
However, the nature of the proposed works and construction methodology
means that much of the cable can be constructed with minimal disturbance to the
existing landscape owing to the limited working boundary along existing roads,
footpaths. Therefore, the proposed works
will have limited adverse impacts or negligible impacts on baseline condition
with appropriate mitigation measures. In conclusion, the landscape and visual
impacts are considered acceptable with mitigation measures.
In order to suitably manage the potential environmental effects associated with construction related wastes, full consideration must be given of the re-use of surplus clean material on site (where practicable), or within other development projects, once material balances are finalised. All mitigation measures and waste management procedures outlined within the EIA must be implemented in order to control or eliminate the potential impacts to the environment from waste generation and disposal.
13.10 Health
Effect
The predicted EMFs for the proposed underground cables, cables in tunnel and submarine cables will be well under the stipulated guideline limits (below 1/5 of guideline limits) issued by the ICNIRP. As such, the existence of EMF associated with the proposed project is not anticipated to pose any adverse impact on public health.
Based on the findings of the baseline review, geophysical survey and diver inspection, it was confirmed that no archaeological significant material was identified in the study area. Therefore any further archaeological investigation or mitigation measures are not required.
An environmental monitoring and audit (EM&A) programme is recommended to be undertaken during the implementation of the Project. This is summarised herein and will be elaborated upon in the EM&A Manual.