10.1
Introduction
10.1.1
Environmental impact
assessments for the Reclamation of Yau Tong Bay are conducted
under the requirement of the Study Brief No. ESB-0010/1998. The key environmental issues involve
noise, water quality, waste management, biogas risk, land contamination and
visual and landscape impacts. Major
findings and the recommendations are summarized in the following sections.
10.2
Major findings of the
Environmental Impact Assessment Study for the Reclamation of Yau Tong Bay
Reclamation Method
10.2.1
With due consideration of the
environmental impacts caused by reclamation to the harbour,
a more environmental friendly reclamation method and construction sequence
among other possible alternatives are recommended for the proposed reclamation. As the release of contaminants in the
seabed could not be avoided during the process of dredging, and treatment and
disposal of both contaminated and uncontaminated dredged marine sediment will
create another environmental impacts, the reduced amount of dredging can
minimize the adverse impact caused by dredging. “Drained” reclamation method is proposed
for general reclamation area in order to expedite the rate of settlement. By this method, except the dredging of
soft marine deposit for the foundation of new seawall and the proposed box
culverts, which is considered essential in engineering points of view, no
additional dredging of marine sediment will be required.
10.2.2
Apart from this reclamation
method, the construction sequence is carefully designed in order to minimize
the adverse environmental impacts arising from reclamation. The existing stormwater
culvert will be diverted to the harbour by a
temporary channel such that the discharge will not enter into the reclamation
site. The permanent seawalls, which
will be built prior to the bulk filling, together with the existing seawall and
the temporary diversion channel will enclose the entire reclamation site,
preventing the dispersal of fill material to the harbour.
10.2.3
In order to alleviate the acute
shortage of filling capacity to minimize the need of new public dump site and
to help extend the existing land fill life in Hong Kong, except the use of rockfill for the foundation of new seawall and sandfill for the drainage blanket to be overlay directly
onto the marine deposit, it is recommended to maximize the use of public
filling material for reclamation of Yau Tong Bay in
principle. Imported sandfill will only be used for reclamation in the case of
unstable or insufficient supply of public filling material which affect the
construction programme.
Noise
10.2.4
An environmental noise impact
assessment on the proposed Yau Tong Bay Development
Reclamation has been conducted to predict the construction noise impacts at the
existing and planned noise sensitive receivers (NSRs)
in the Yau Tong neighbourhood.
10.2.5
The predicted facade noise
levels at the nearby NSRs will be within the
construction noise criterion for domestic premises throughout the reclamation
period.
10.2.6
Recommendation has been given
with practicable mitigation measures to further reduce the construction work
noise impact on the NSRs.
Water Quality
Assessment Criteria
and Water Sensitive Receivers
10.2.7
The water quality impacts of
the YTB reclamation during the construction and operation phases were assessed
against the Water Quality Objective (WQO) for the Victoria Harbour
Water Control Zone (VHWCZ) and the relevant standards at the salt water intakes
in the YTB area. Water sensitive
receivers (WSRs) most likely to be affected are:
·
The salt water intakes of the
existing and future potential reprovisioned Cha Kwo Ling Salt Water Pumping Station (CKLSPS) under Full
Reclamation option;
·
The salt water intakes of the
existing and reprovisioned Yau
Tong Salt Water Pumping Station (YTSPS); and
·
The existing Dairy Farm Ice
Factory salt water intake (DFSI).
Construction Phase
Water Quality Impacts
10.2.8
Sediment plume modelling was conducted to assess the water quality impact
for the different construction phases of the proposed YTB reclamation. According to the current construction
schedule, bulk filling will commence after the seawall construction and thus
the plume is effectively confined in YTB.
Modelling results show that no major impact is
expected in Victoria Harbour during the construction phase.
10.2.9
As a result of the dredging and
filling activities for the YTB reclamation, an elevation of suspended solids in
the water column was predicted at the WSRs. The works
schedule was carefully programmed so that the production rate, and thus the
water quality impact, is minimized.
Furthermore, appropriate mitigation measures were recommended for the
YTB reclamation as follows:
·
Closed grab dredgers with silt
curtain should be used for the dredging and filling of seawall foundation;
·
A silt curtain should be placed
across the seawall opening during the Phase 1 and Phase 2
reclamations using bottom dumping;
·
Double layers of silt screen
should be installed at the salt water intakes of the YTSPS, CKLSPS and DFSI;
and
·
The filling rates of
Phase 1 and Phase 2 reclamations should be limited to 10,000 m3day-1
and 6,000 m3day-1 respectively.
10.2.10
With the proposed mitigation
measures fully implemented, it is anticipated that the size of the sediment
plume of the YTB reclamation (Full Reclamation option) will be reduced,
minimizing the impact on Victoria Harbour. It is also expected that the SS
concentration at the WSRs will satisfy the WSD
tolerable limit for SS (20mgL-1) at the CKLSPS and YTSPS, and the
in-house standard of 20mgL-1 for SS at the DFSI at all times.
10.2.11
Taking into account the impacts
of other concurrent construction activities in Victoria Harbour, including:
·
The Western Coast Road;
·
The Tseung
Kwan O New Town Intensification and Extension;
·
The Tseung
Kwan O Cargo Working Area; and
·
The South East Kowloon Development;
It was found that the YTB reclamation
only contributes to a minor impact on the water quality near YTB. With the implementation of the
recommended mitigation measures, the concurrent construction activities in Victoria Harbour are not expected to cause
any unacceptable adverse impact to Victoria Harbour and the identified water
sensitive receivers.
10.2.12
The model results indicate that
temporary diversion of the YTB stormwater culvert to
the existing water front, south of YTB, would have negligible impact on the
water quality in Victoria Harbour and other sensitive receivers.
10.2.13
Laboratory analysis of marine
sediment samples from YTB revealed that the potential release of contaminants
during the dredging and surcharging works will not cause any exceedance of the UK Water Quality Standards for Coastal
Surface Water, and thus, unacceptable adverse impact is not anticipated.
10.2.14
An environmental monitoring and
auditing (EM&A) program is recommended to ensure that the YTB reclamation
works would not cause unacceptable deterioration of water quality at the neighbouring salt water intakes and in Victoria Harbour.
Operation Phase Water Quality Impacts
10.2.15
A major concern of the YTB
reclamation is the potential impact on the flow through Victoria Harbour and, in turn, the water quality. Hydrodynamic modelling
reveal that the changes in flow discharge rates through Victoria Harbour before and after the YTB reclamation would be very small and the
tidal flow patterns would be similar with minor deviation near YTB. These results indicate that the YTB
reclamation is unlikely to have any noticeable effect on the tidal flow regime
and hence water quality in Victoria Harbour.
10.2.16
In Full Reclamation Option, as
well as the Minimised Reclamation Option, the water
quality at the existing Cha Kwo Ling Salt Water
Pumping Station (CKLSPS) is expected to be acceptable. Hence, reprovisioning
of the existing CKLSPS intake after Yau Tong Bay reclamation will not be required. If it is the intention of WSD to
relocate their CKLSPS, it can be relocated to the new waterfront of YTB
reclamation in Full Reclamation Option.
The potential water quality impact of an emergency discharge from the Yau Tong Sewage Pumping Station on the possible future reprovisioned CKLSPS has been assessed. The model results indicate that the
depth averaged water quality in terms of BOD5, SS and ammoniacal nitrogen is expected to meet the WSD standards
at the future reprovisioned CKLSPS; however, the E. coli standards will be exceeded. The sewage plume is shown to attach to
the shoreline and is buoyant at the surface with a thickness of less than
0.4m. To avoid abstracting the
sewage plume water, it is recommended that the saltwater intake should be
located below -2.0 mPD. The intake water would then be expected
to comply with the WSD water quality standards. The optimal intake configuration should
be reviewed and decided at the detailed design stage if reprovisioning
is required by WSD.
10.2.17
The existing YTB stormwater culvert will eventually be extended to the new
water front of YTB reclamation. The
model results indicate that the polluted stormwater
in the new Kwun Tong nullah
and the new YTB stormwater culvert is not expected to
have any major water quality impact in Victoria Harbour, as well as at both the existing and potential reprovisioned
CKLSPS and YTSPS.
Waste Management
10.2.18
During the construction phase
of the four proposed development options, wastes generated by construction
works are likely to include general site wastes, workforce wastes, maintenance
and chemical wastes, and construction and demolition material. Chemical waste produced from the
construction activities should be handled according to the Code of Practice on
the Packaging, Labelling and Storage of Chemical
Wastes and disposed of by a licenced contractor. These waste arisings
are not expected to generate significant waste management related impacts,
provided that the recommended mitigation measures are implemented and good site
practices are adhered to.
10.2.19
The drained reclamation method
is recommended for YTB reclamation to minimize the volume of dredged sediments
and the potential environmental impacts.
The estimated total dredged volume for the Full Reclamation option is
175,150 m3, among which 82,800 m3 are
classified as Category H mud. The
total dredged volume for the Minimised Reclamation
option is estimated to be 112,170 m3, with 53,270 m3
classified as Category H mud.
10.2.20
It is considered that the
potential impacts of the dredging works and associated dredged sediment
disposal can be minimized provided that the recommended mitigation measures,
including the procedures detailed in WBTC No. 3/2000, are implemented. Contaminated dredged sediments will not
be suitable for open sea disposal.
A sediment sampling and testing programme will
be required at the design stage of the Project in accordance with the
requirements of WBTC No. 3/2000.
The need for any special treatment/disposal procedures for dredged
sediments will be examined in detail at the design stage, as necessary, based
on the results of biological screening.
A review of possible special disposal arrangements has recommended
containment of the contaminated sediments during dumping to prevent any release
of material to the marine environment.
Field trials are recommended to be undertaken during the detailed design
stage (using uncontaminated mud) to establish the optimum handling method.
Biogas Risk
10.2.21
Organically enriched material
is planned to be left in-situ beneath
the proposed YTB Full Reclamation and Minimised
Reclamation options. As methane gas
could be generated under anaerobic conditions, there is a potential for this
gas to be released either during construction or after development of the
reclaimed area.
10.2.22
The risk of gas generation
becoming a development constraint of the two proposed reclamation options for
YTB has been assessed. The
predicted methane gas generation potential is not expected to pose a constraint
to the development of the proposed reclamation.
10.2.23
As sensitive ‘at risk’ rooms
have been identified at the proposed development for both reclamation options,
it is recommended that a precautionary principle be applied. It is recommended that gas monitoring be
undertaken in the immediate post-reclamation period (prior to the commencement
of construction works on the reclamation) to measure methane concentrations in
the fill and to determine actual rates of methane gas emissions. The review of the monitoring results
would determine the extent and type of gas protection measures to be
incorporated in the building design to prevent the ingress and/or accumulation
of any methane gas emissions to potentially dangerous concentrations. Guidelines on criteria for evaluation of
the gas monitoring results and gas protection measure requirements have been identified
for both the ground level and underground structures at the development. As a further precaution, naked flames
should not be permitted during construction involving drilling or excavation.
10.2.24
The proposed monitoring
guidelines and other precautionary mitigation measures recommended for both reclamation
options should be examined further at the detailed design stage with regard to
the specific design details of individual buildings. With the incorporation of the
recommended gas protection measures in the design of the buildings together
with the implementation of the recommended precautionary measures, the risk to
people and property is considered to be low.
Land Contamination
10.2.25
A detailed land contamination
assessment for the site has been completed. Site investigation works, including
soil testing for contamination level, were conducted in accordance with an
endorsed Contamination Assessment Plan (CAP). The soil and groundwater analytical
results revealed that the marine lots were partly contaminated with petroleum
hydrocarbons and heavy metals. High
level of PCBs and PAH were also found in isolated locations. Remediation methods for treating
contaminated soil and groundwater were proposed in the Remediation Action Plan
(RAP) and the developer should implement and complete the required remediation
works to the required standard prior to commencement of any development
construction works.
Visual and Landscape
Impact
10.2.26
The quality of the existing
landscape of Yau Tong Bay is
generally poor. The access to
waterfront is blocked by the shipyards, timberyards
and open storage areas, and the bay is occupied by numerous vessels and barges.
10.2.27
The construction activities
will have low negative impact to the landscape resource and landscape
character. The negative impact
would be further reduced if Minimised Reclamation
Option is adopted.
10.2.28
The mitigation measures
proposed will minimize the potential visual and landscape impact, although, the
effect is limited.
10.2.29
The extent of visual impact to
adjacent lots will depend on the construction programme
of these lots. In general, Yau Tong Estate Redevelopment and EHC site (Phase 1 and 2)
will be completed and occupied by future resident during construction phase of
the project, while resident for EHC site (Phase 3) will still not move in.
10.2.30
The construction activities will
have moderate negative visual impact to the future resident of Yau Tong Estate Redevelopment, EHC site (Phase 1 and 2),
and Cha Kwo Ling Kaolin Mine Site, while the impact
to the industrial workers at Ko Fai
Road will be low. The visual impact
to the existing resident at Sceneway Garden, Lam Tin
Estate, Ping Tin Estate, Kwong Tin Estate, Hong Nga Court, Hong Pok Court, Ko Chun Court and Ko Yee Estate
at mid level of Chiu Keng Wan Shan are considered as
low as their views toward the site will be mostly blocked by the house blocks
of Yau Tong Estate Redevelopment and Ko Chiu Road Estate Redevelopment (Phase 3 and 5) in year
2001, and EHC site development at year 2004 to 2006.
10.2.31
During the operational phase,
the impact remains the same as construction phase if the flat piece of
reclaimed land is allowed to leave idle.
The impact would be reduced if construction work for proposed
comprehensive development are proceed continuously after completion of
reclamation work, although, there will likely be some negative impact due the
construction work.
10.2.32
Based on the above study, the
landscape and visual impact are considered acceptable with mitigation measures
for both Reclamation Options.
10.2.33
If coastal option of Western Coast is
adopted, Full Reclamation Option would be carried out and the proposed elevated
structure of Western Coast
Road would be constructed
at the reclaimed land on western side of the project site, it would form a dominent feature along the waterfront of East Kowloon. The visual impact is
considered negative. It would be
beneficial to the harbour views if the Western Coast Road is constructed on the reclaimed land directly. If such proposal is adopted, footbridges
and/or underground subways will be provided across the Western Coast Road to improve the pedestrian linkage from Yau
Tong and CDA site to the waterfront.
10.2.34
The magnitude of negative
impact on both landscape and visual quality due to the proposed reclamation
works at operational phase would be reduced if Tunnel Option for the future Western Coast Road is adopted (i.e. Minimised Reclamation
Option). It would also help to minimize the impact to the coastal line of Victoria Harbour as the proposed extent of reclamation works are
reduced.
10.3
Overall Conclusion
10.3.1
The existing Yau Tong Bay is currently characterised by industrial
operations such as shipyards, timber yards, sawmills, construction materials
storage, industrial building and vehicle repair workshops. The existing environment of YTB is
considered poor and is suspected to be polluted by the existing
industries. The stagnant water in
the bay, together with the current industrial operations will cause nuisance to
the future residents of the adjacent large-scale housing redevelopment projects
when completed. The harmful
pollutants generated by the highly contaminated industry will also affect the
health of existing and Yau Tong Bay future
residents.
10.3.2
Additionally, the future and
presently operated schools in the vicinity of Yau Tong Bay are vulnerable to noise nuisance generated by the operations on the
existing marine lots. It is
foreseeable that complaints from future nearby residents against the nuisance
will pose a problem and pressure for the government.
10.3.3
Reclamation of Yau Tong Bay and the subsequent development on the reclaimed land provide an
opportunity to remove the existing polluting industrial operations at Yau Tong Bay. It is
undoubtedly to the benefits of everyone who lives or studies in Yau Tong for the bay to be reclaimed such that the nuisance
caused by the polluting industrial operations could be removed as well.
10.3.4
The seabed of the existing Yau Tong Bay is highly contaminated by the discharge or contaminants released
from the existing industrial operations of the surrounding marine lots, such as
shipyards, sawmill or car repairing industry. The odour
arising from the contaminated seabed might cause nuisance to the nearby
residents. Also, consuming the
polluted fishes caught at the bay would be harmful if not hazardous to health. In order to minimise
the adverse impacts of the contaminated seabed to the public and marine
habitat, it is recommended to retain the contaminated marine deposit at its
original position as far as possible and isolate it from the marine
environment. Concealing the
contaminated Yau Tong Bay seabed by
reclamation is an effective method to achieve this.
10.3.5
The reclamation also provides
an opportunity for decommissioning the existing shipyards and demolition of
building structures. This project
not only relieve the pollution problems caused by the existing industries, but
also provide land to achieve important community development objectives, such
as provisions of schools and open space for continuous seafront promenade.