Chapter Title Page
Figures
Figure 2.1.1 Proposed Alignment of
SIL(E) (Sheet 1 of 5)
Figure 2.1.2 Proposed Alignment of
SIL(E) (Sheet 2 of 5)
Figure 2.1.3 Proposed Alignment of SIL(E)
(Sheet 3 of 5)
Figure 2.1.4 Proposed Alignment of
SIL(E) (Sheet 4 of 5)
Figure 2.1.5 Proposed Alignment of
SIL(E) (Sheet 5 of 5)
Figure 2.2 Two Possible
Locations Evaluated for SOH Station
Figure 2.3 LET Station to
Figure 2.4 Section between
Figure 2.5 Envisaged
Construction Methods for SIL(E)
Figure 2.6.1 Works Areas (Sheet 1 of
10)
Figure 2.6.2 Works Areas (Sheet 2 of
10)
Figure 2.6.3 Works Areas (Sheet 3 of
10)
Figure 2.6.4 Works Areas (Sheet 4 of
10)
Figure 2.6.5 Works Areas (Sheet 5 of
10)
Figure 2.6.6 Works Areas (Sheet 6 of
10)
Figure 2.6.7 Works Areas (Sheet 7 of
10)
Figure 2.6.8 Works Areas (Sheet 8 of
10)
Figure 2.6.9 Works Areas (Sheet 9 of
10)
Figure 2.6.10 Works Areas (Sheet 10 of
10)
Figure 2.6.11 Works Areas (
Figure 2.6.12 Works Areas (Chung Hom Shan
Magazine Site)
Figure 2.7 Typical Layout of
Crushing Facilities
Appendices
Appendix 2.1 List of Public
Consultation Activities
Appendix 2.2 Tunnel Construction
Methods
Appendix 2.3 Tentative Construction
Programme
Appendix 2.4 Construction Timeline for
SIL(E) and Other Concurrent Projects
The South Island Line (SIL) was originally proposed as part
of the Second Railway Development Study (RDS-2) completed in May 2000 as an
extension to the existing railway network to serve the Southern District of
Hong Kong. In June 2002, MTRCL submitted
a preliminary proposal for a medium-capacity SIL, which involved a monorail
system looping from University Station of the planned West Island Line (WIL) to
the southern part of
Subsequently, MTRCL further developed the proposed SIL as
part of a Feasibility Study (FS) entitled “West Island Line and South Island Line
Feasibility Study” which was completed in March 2004. After an evaluation of various alternative
options, the FS recommended the implementation of the proposed SIL(E) from
South Horizons to Admiralty, via intermediate stations at Lei Tung, Wong Chuk Hang
and Ocean Park, for serving the Southern District and provision of a necessary
depot at Wong Chuk Hang to support the operation of SIL, amongst other
recommendations related to WIL. The FS
also evaluated the feasibility of providing additional intermediate stations at
In December 2007, the Executive Council gave the green light for MTRCL to proceed with preliminary planning and design of the SIL(E), which will be a medium capacity railway line running from Admiralty to South Horizons, with three intermediate stations at Ocean Park, Wong Chuk Hang and Lei Tung. In response to the Government’s decision, MTRCL recruited an Engineering Design Consultant to undertake preliminary design for the SIL(E) in February 2008 and appointed separate Engineering Design Consultants to undertake scheme and detailed design in mid 2009. The SIL(E) scheme was gazetted under the Railways Ordinance in July 2009.
The proposed SIL(E) comprises a new medium-capacity railway
system with an approximate total route length of
The new railway line will run in tunnel for a route length of
about
The proposed Admiralty station, which is situated to the east of the existing Admiralty station as illustrated in Figure 2.1.5, will be underground. The two new stations at Lei Tung and South Horizons on Ap Lei Chau (as illustrated in Figures 2.1.2) will also be located underground, while the two stations at Ocean Park and Wong Chuk Hang will be above-ground (Figures 2.1.3 refer).
Southern District has a long desire
to have a railway connected, in particular for the population in Ap Lei Chau.
The proposed SIL(E) will provide a fast, convenient, environmentally friendly
and reliable mode of public transport between South Horizons and the central
business district of Hong Kong, as well as for cross harbour trips via the
interchange with the existing railway network at Admiralty Station. The new railway line serves not only the
resident population in the Southern District but also tourists heading to or
returning from the major existing and future tourist attractions located in the
District. Upon completion of SIL as well
as the Shatin to Central Link, the railway network on
Operation of the new railway line will help relieve existing
traffic congestion experienced at critical bottlenecks, including the Aberdeen
Tunnel and as a result journey times on the
There will be no direct emission of air pollutants from operation of the trains as they are electric powered. Reduced road traffic and congestion will also lead to improvements in local air quality.
Development of the Southern District has long been constrained by the lack of a reliable mass transportation system. Operation of the SIL(E) will remove this constraint and serve as a catalyst to trigger renewal of older districts in the Southern District in the long term. The Wong Chuk Hang area in particular would be rejuvenated. Significant new employment opportunities will also be created as new businesses will be benefited from the improved transport.
The Project comprises:
a.
approximately
b.
construction
of South Horizons (SOH), Lei Tung (LET), Wong Chuk Hang (WCH) and Ocean Park
(OCP) stations as well as Admiralty (ADM) interchange station for SIL(E) and
SCL which includes station structures and protection works for interchange with
SCL. WCH and OCP Stations are designed
to be elevated along the viaduct alignment, while SOH, LET and ADM Stations are
designed to be underground associated with above-ground entrances and exits,
ventilation shafts and plant buildings, and will be constructed by either
drill-and-blast or cut-and-cover tunnelling method;
c.
construction
of tunnels by drill-and-blast, mining and cut-and-cover method. Based on the
current design, tunnel sections from Admiralty to Nam Fung Portal and from Lee
Nam Road to Ap Lei Chau Drive will be constructed by drill-and-blast tunnelling
method, whilst tunnel sections from Ap Lei Chau Drive to the portal at the
southern side of Aberdeen Channel Bridge will be constructed by mining and cut
and cover tunnelling method;
d.
construction
of tunnel portals at southern side of
e.
construction
of ventilation shafts along the alignment associated with the proposed
stations, at
f.
construction
of a railway depot at the ex-Wong Chuk Hang Estate site;
g.
construction
of a viaduct section from
h.
construction
of a railway bridge alongside the existing Ap Lei Chau Bridge across the
Aberdeen Channel;
i.
provision
of site offices, areas for construction material storage, construction shafts,
temporary barging points and temporary magazine site during construction; and
j.
operation
of the railway system and the depot.
At present, traffic pile-up at the Cross Harbour Tunnel and
The proposed SIL(E) will help reduce traffic on the road and help relieve the existing traffic congestion problem. Without the project, people travelling to or from the Southern District will have to continue relying on the existing congested road system in travelling between the region and the central business district. Planned new developments such as new residential developments, offices and schools in the Southern District may aggravate the traffic congestion problem.
MTRCL values the views of stakeholders and considers that the support of the community is important in the development of railway extensions. The Corporation together with the Southern District Council launched a public consultation programme in conjunction with the preliminary design for the SIL(E). The public consultation programme consists of 2 rounds of activities which commenced in March 2008 and September 2008, respectively. Public forums, meetings with residents and a series of roving exhibitions were organised as part of the public consultation programme. The Central & Western District Council and the Wanchai Council were also consulted about the proposed arrangement of Admiralty Station and the feasibility of the provision of the Happy Valley Station. A list of these activities is given in Appendix 2.1.
Most of the feedback received during the public consultation were requested for early completion of SIL(E) to solve the traffic problems. Suggestions received during the public consultation process in relation to the further planning of the SIL(E) project, ranging from issues on station locations and design, through locations of station entrances, to alignment of the railway line have been taken into account as far as practicable in the design of the Project. The 2-round of public consultation has also allowed the Corporation to give the community a better understanding of the planning of the Project and site-specific factors and constraints that have to be taken account of in selecting the preferred alignment and design of the Project.
Key comments received from the various rounds of public consultations were described below.
During the first round of public consultation, some residents
suggested a conceptual plan that involved lowering gradually the level of the
proposed viaduct from Ocean Park, to at grade level in Wong Chuk Hang, then
went underground to deeper level until reaching Ap Lei Chau when the railway
would be in deep rock tunnel, and climbed up again to the proposed underground
station at LET. Further evaluation of
this proposal revealed that given the gradient requirements, the section
changing from viaduct to tunnel would cut across
For the location of SOH Station, apart from two possible
locations including i) to the immediate north of
¡ Lower
SOH Station at
¡ Move the station back under Yuk Kwai Shan to avoid the utilities problem and avoid disruption of the South Horizons area;
¡ Locate
the station in the area of the playground on
However, these schemes were not considered further in view of problems associated with constructability and passenger convenience:
¡ Lowering
of the SOH Station at
¡ Moving
the station back under Yuk Kwai Shan and locating the station in the playground
on
Considerations given to address comments from the public consultation on railway design alternatives and other public comments were detailed in Sections 2.7 and 2.8 below.
2.7
Consideration
of Railway Design Alternatives
The SIL(E) is planned for serving the Southern District of Hong Kong. The purpose of the project dictates to a certain extent the appropriate location of the stations and hence the alignment of the new railway line. The congested urban areas presented many site constraints on the location of the stations and alignment.
2.7.1.1 Consideration of Design Alternatives at FS Stage
The planning of the new railway line for serving the
community began with the identification of those areas in the Southern part of
The maximum flow capacity required to serve the Southern District suggested that a medium capacity system would be appropriate for SIL(E). After a detailed evaluation of various alternative options, the preferred network option recommended in the FS involves a medium capacity system for SIL(E) that will run from Admiralty to South Horizons, with three intermediate stations at OCP, WCH and LET. The station locations were chosen to optimise the station catchments, while taking into account relevant site factors including environmental considerations before selecting the preferred network option and railway alignment. The station locations and associated alignment were identified taking into account the existing land uses such that any encroachment into private land and hence necessary land resumption for the construction of the project can be avoided as far as practicable.
2.7.1.2 Further Consideration of Design Alternatives at Preliminary Design Stage
The Preliminary Design exercise has allowed the further planning and design of the proposed SIL(E) and where possible the evaluation of design alternatives. The alignment design, including key horizontal and vertical alignment criteria, have largely followed the railway engineering design requirements while taking into account the shorter train length of the proposed medium capacity system as compared with the traditional urban line stock of MTRCL. The Preliminary Design exercise commenced with a review of the recommendations of the FS as the base scheme. Design alternatives, where available, were identified and analyzed before determining the preferred or refined design. Amongst other site-specific factors and engineering constraints, environmental benefits and dis-benefits during both the operational and construction phases have been given due consideration in the evaluation of alternatives.
2.7.1.3 Key Considerations and Findings
The key considerations and findings in relation to
consideration of alternative options in terms of alignment, station locations,
location of the depot, as well as train system design are summarised in the
sub-sections below. Taking into account
the prevailing site conditions and constraints, an alignment option review
undertaken as part of the Preliminary Design has confirmed that a viaduct
section will be required in the Wong Chuk Hang and
Discussions focusing the different sections of the project are presented below under the following headings:
¡
Section
between South Horizons and Lei Tung;
¡
Section
between Lei Tung and
¡
Section
between
¡
Section
between
¡
Station
Entrances;
¡
Ventilation
Shafts;
¡
Depot
location;
¡
Train
system;
¡
Temporary
Barging Points; and
¡
Temporary
Magazine.
2.7.2 Section between South Horizons and Lei Tung
2.7.2.1 Location of SOH Station
As shown in Figure 2.2, two possible locations were evaluated for the SOH Station, including:
¡
SOH
Station Option 1 (base scheme) – to the immediate north of
¡
SOH
Station Option 2 (alternative scheme) – under
SOH Station
Option 1
At the FS stage, the SOH Station was recommended to be
located to the immediate north of
During the construction phase, a major disadvantage of this station option is the direct conflict with the existing major 275kV electricity transmission cables. These cables originate from the existing buildings of Hong Kong Electric Company Limited (HEC) opposite the proposed station location. As a result, the cables will have to be diverted for construction of the proposed station and it is envisaged that the diversion work will delay the completion of SOH by about 3 years to 2018.
Besides, to arrive at this proposed station location, the
approach tunnel will have to run along the section of
SOH Station
Option 2
Further evaluation as part of the preliminary design has
identified a practicable alternative location for construction of the SOH
Station. The alternative station
location is under
Compared with Option 1, Option 2 is considered better from
the perspective of avoiding potential noise and visual impact from ventilation
shafts and other fixed plants, which can be integrated into the design of the
plant building alongside
During the construction phase, although required excavation for the cut-and-cover box at Yi Nam Road and Lee Nam Road will also lead to environmental impact in terms of noise, dust and visual impacts on the residents in the proximity, the length of the cut-and-cover section is significantly reduced for Option 2 compared with Option 1, as the south-east end of the station and the associated approach tunnel will be construction inside the hill away from the sensitive receivers. Compared with Option 1, the number of sensitive receivers situated in the vicinity of the work site is also lower for Option 2. Deep station arrangement for Option 2 is technically infeasible due to unacceptable gradient between LET and SOH stations. Station at shallower depth will be in soft ground and thus cut-and-cover method cannot be avoided.
Selection of
Preferred SOH Station Location
Taking into account the factors described above, the SOH
Station Option 2 – under
Table 2.1: Selection of Preferred SOH Station Location
|
Option |
Engineering Factors, including constraints |
Environmental Benefits and/or Dis-benefits (on relative terms) |
|
SOH Station Option 1 – to the immediate north of |
§ Direct conflict with existing major 275kV electricity transmission cables; required diversion will have significant impact on the completion date of the SOH Station; §
Require closure of a section of eastbound |
Dis-benefits: § Noise and visual impacts from ventilation shaft and fixed plant on residential block of Lei Yee House and other nearby sensitive receivers (given their close proximity to the station box), requiring mitigation; § Cut-and-cover construction of station box and approach tunnel and additional excavation required for cable diversion will lead to noise, dust and visual impacts on the sensitive receivers situated in close proximity; § Number of sensitive receivers in the proximity is relatively high |
|
SOH Station Option 2 – under |
§
South-east end of station will be under a
slope to the south of § Length of required cut-and-cover section reduced significantly, reducing extent and duration of necessary traffic diversion |
Benefits: § Ventilation shafts and fixed plants can be integrated into design of the station plant building away from sensitive receivers, thus noise and visual impact can be minimised; §
Some station and tunnel plant can be
accommodated at separate plant building at § Cut-and-cover construction avoided for south-east end of station and approach tunnel, reducing the associated dust, noise and visual impact and secondary environmental impact from major traffic diversion § Number of sensitive receivers is lower than that of SOH Station Option 1 |
2.7.2.2 Alignment Options
Two alternative tunnel alignments (see Figure 2.2) that cater for the two different location options for SOH Station were evaluated accordingly. Taking into account the location of SOH Station selected (i.e., SOH Station Option 2 described above), the preferred alignment of the tunnel between SOH Station and LET Station in which beyond SOH the alignment turns through about 90 degrees and runs under Yuk Kwai Shan to approach LET was selected accordingly. From an environmental perspective, the tunnel alignment associated with SOH Station Option 2 is preferred in terms of minimising potential environmental impact from cut-and-cover construction during the construction phase as described above.
2.7.3
Section between Lei Tung and
2.7.3.1 Alternative Alignments and Station Locations evaluated at the FS Stage
At the early stage of the FS, alternative locations and configuration of LET Station and the associated approach tunnel were considered.
It was identified that the alignment to the south would
require a high viaduct across Aberdeen Channel, running south along the line of
Ap Lei Chau Praya Road before turning to the west. Taking into account the site
constraints, the alignment would need to go into tunnel within the grounds of
Hong Kong True Light College and then along the narrow gap between Hor On House
of Yue On Court and Lei Tung Estate of Tung Ping House. The tunnels would pass under the perimeter of
both buildings. In view of the
significant impact on the existing school, this option was not considered
technically viable. Besides, under this
option, a longer span bridge would be required to cross the Aberdeen Channel
and the non-parallel alignment to the existing Ap Lei Chau Bridge would create
adverse visual impact. The bridge would
also need a central pier away from the location of the existing pier, which would
adversely affect marine traffic through the channel and is not preferable in
terms of potential adverse effect on flushing capacity and water quality within
the Aberdeen Channel (Typhoon Shelter). Two alternative alignments to the north
were also considered, both running parallel to the Ap Lei Chau Bridge, with one
elevated to the immediate north of
The FS therefore concluded that the alignment which passes under Yue On Court and Lei Tung Estate were adopted as the base scheme for further consideration.
2.7.3.2 Further evaluation as part of the Preliminary Design
LET Station
Options 1 and 2
The main considerations given to positioning the LET station include issues with topography, the variation in levels and connectivity between exits. Other design constraint is the potential impact on foundations of existing buildings. This severity limited the available options for siting LET station.
Based on locating the LET Station under Lei Tung Estate as the base scheme, two alternative options for the stations were further evaluated as part of the preliminary design:
¡
LET
Station Option 1 (base scheme) – shallow alignment option;
¡
LET
Station Option 2 (alternative scheme) – deeper alignment option.
Alignment
Options
It was identified that the open cut section of the approach tunnel at Yue On Court as proposed in both Options 1 and 2 would impose impacts on the residents, including potential groundborne noise impact during the operation phase and environmental impact from the excavation works on residential buildings in the proximity during the construction phase.
Further evaluation of alternatives as part of the Preliminary Design process revealed that these impacts can be minimised by adopting a deeper alignment (i.e., Option 2). Option 2 will not require the cut-and-cover section within Yue On Court lot. This will minimise the overall environmental impact on the sensitive receivers in the proximity.
Besides, as shown in Figure 2.3, a shallow alignment scheme for LET Station would require a section over Ap Lei Chau Drive to be placed on viaduct and given the proximity of sensitive receivers, noise and visual impact mitigation measures will have to be incorporated into the design of the viaduct. For the deeper alignment scheme, the corresponding section will be in cut-and-cover tunnel.
As identified through the FS and established in the Preliminary Design exercise, the alignment of the railway bridge across Aberdeen Channel adopted is as such that it will be lying parallel to the two existing highway bridges to minimise any potential visual impact. A similar alignment will also permit similar location of the north pier within the Aberdeen Channel such that any potential adverse effects on flushing capacity and water quality within the Aberdeen Channel (Typhoon Shelter) can be avoided.
Selection of Preferred Station Location and Alignment
Table 2.2 summarises the environmental benefits and dis-benefits considered in the evaluation of the two options of LET Station and associated alignment. The deeper alignment option (i.e., Option 2) was identified to be the preferred option. The tunnel would pass deep underneath the open space of the blocks of Yue On Court. The foundations of existing buildings would not be impacted.
Table 2.2: Selection of Preferred LET Station Location and Associated Alignment
|
Option |
Environmental Benefits and/or Dis-benefits (on relative terms) |
|
LET Station Option 1 – shallow alignment option |
Dis-benefits: § Potential ground-borne noise impact during the operation phase § Potential environmental impact from the excavation works on residential buildings in the proximity during the construction phase § Noise and visual impacts mitigation measures have to be incorporated into the design of a viaduct section over Ap Lei Chau Drive given the proximity of sensitive receivers |
|
LET Station Option 2 – deeper alignment option |
Benefits: § Ground-borne noise impact minimised with deeper tunnel alignment; § Section crossing Ap Lei Chau Drive will be in cut-and-cover tunnel, hence additional noise and visual impact mitigation measures are not required |
2.7.4
Section between
2.7.4.1 Locations of WCH and OCP Stations
As detailed below, a number of vertical alignment options were
considered as part of the Preliminary Design exercise. After a detailed evaluation of the technical
difficulties, construction risk, impact on existing land uses and existing
extra high voltage cables behind wall of Staunton Creek Nullah, operation of
Aberdeen Channel, impact on the construction programme as well as design,
operational requirements, the underground alignment options were not identified
to be practicable. Accordingly, the WCH
and OCP Stations have to be designed at elevated level along the proposed
viaduct. Considerations had been given
to locate the WCH Station to the south of the Staunton Creek Nullah or as far
north as possible of the proposed road layout for
Compared with an underground station, it is envisaged that urban regeneration of Wong Chuk Hang would be better served by an above-ground WCH station. Specifically, it is noted that at Wong Chuk Hang, the presence of the Stauton Creek Nullah dictates that any grade-separated passage across the various roads in the area must be by footbridges rather than by subways. With an above-ground WCH Station, opportunity exists for pedestrian walkways of future developments to link straight into the station concourse, thus enhancing passenger accessibility to the station.
Similarly, an above-ground station at
An above-ground location of the stations will also permit the incorporation of more sustainable and environmentally friendly features into the design, including reduced use of electricity in lighting and air-conditioning systems through permitting natural light and/or wind to enter the stations.
2.7.4.2 Alignment Options
A number of alignment options were considered for the railway section between Aberdeen Channel Crossing and Nam Fung Portal, including:
¡
Option
1 – in deep rock tunnel;
¡
Option
2 – in shallow tunnel; and
¡
Option
3 – on viaduct
Option 1 – in
deep rock tunnel
Under this option, the railway would be running in deep rock
tunnels below ground (at some
In addition to the operational dis-benefit is the environmental dis-benefit resulting from significant amounts of excavated materials produced and the longer construction period due to the extra excavation requirement. Other considerations include issues relating to connectivity and accessibility from a passenger’s point of view, whereby a deep subway would take up more of the passenger’s time to get from A to B, and would be less convenient for the passenger. Therefore, this option was not considered practicable.
Option 2 – in
shallow tunnel
Under this option, the tunnels will be excavated through the mixed ground above the rock layer. Compared with the deep rock tunnel Option 1 described above, both the depth of tunnels and stations are reduced. The depot will also be underground. The crossing at Aberdeen Channel will have to be constructed by cofferdam and/or immersed tunnel method.
During the construction phase, those sections that are required to be constructed by cut-and-cover method would result in environmental impacts on the nearby sensitive receivers. These include noise, dust and visual impact associated with construction activities including site clearance, pipe pile wall or diaphragm wall installation, excavation and spoil removal and tunnel and station construction. Cut-and-cover construction at major road carriageways would also result in traffic disruption, increased traffic congestion and associated noise and gaseous emissions.
During the operational phase, potential environmental concerns including airborne noise and visual impact can be minimised, and similar to the deep rock tunnel option will be confined to areas in the vicinity of above-ground facilities such as ventilation shafts. Ground-borne noise could be an issue but can be mitigated by adopting appropriate trackform design.
However, further consideration of the in-shallow tunnel option revealed its construction are subjected to a number of technical difficulties and construction risk and will have direct impact on existing land uses, operation of Aberdeen Channel and will delay the completion date of SIL(E). These constraints are summarised below:
(i) Impact on existing land uses
Construction of a floodgate and a ventilation building is required for operation of the tunnel section crossing Aberdeen Channel. The provision of these facilities will require the clearance of a significant portion of existing shipyard area on the north shore of the Channel. Land will also be required for a permanent road for access to the facilities. The land requirement will affect the existing shipyards which have been operating at the location since 1985.
In Wong Chuk Hang, for construction of a cut-and-cover tunnel section required to accommodate complex track geometry for entry to the Wong Chuk Hang Depot, a major part of the existing Hong Kong Police College Tactical Training Complex along Heung Yip Road will have to be demolished, affecting the operation of the Police College.
(ii) Impact on
operation of
In order to construct the tunnel section across the Aberdeen Channel, part of the Channel will need to be closed to facilitate the construction of cofferdams, followed by dewatering of the works site, and subsequent construction of the tunnel units. It was estimated that a significant portion (about two-thirds) of the Aberdeen Channel along the tunnel alignment will have to be closed during the construction of the alignment section. The narrowed fairway will affect the operation of the nearby Aberdeen Typhoon Shelter.
(iii) Impact on the Construction Programme of the Project
The new depot planned in Wong Chuk Hang will need to be put in service on day one of the commissioning of the SIL(E). The completion date of the depot will therefore affect the commissioning programme of the new railway line.
The level of the depot tracks is constrained by the level of
the WCH Station tracks in the proximity, as they are linked by connecting
tracks. For the tunnel alignment option,
the level of the proposed WCH depot will have to be lowered by about
Option 3 – on
viaduct
During the construction phase, adopting a viaduct option would allow the possible use of precast elements such that the railway alignment can be completed within a relatively short period, and without major excavation activities that would be required for construction of a corresponding tunnel section. The viaduct option will also effectively reduce the quantity of excavated materials generated from the Project. The direct waste management implications and secondary environmental impacts from handling and disposal of the excavated materials are thus effectively minimised.
During the operational phase, with incorporation of sufficient mitigation measures into the design to address potential noise and visual impacts, the viaduct can be designed and operated to meet established environmental criteria. Measures have been demonstrated to be practicable through similar projects completed locally and overseas.
From the passengers perspective, an elevated section for the
SIL(E) in Wong Chuk Hang and
The possible horizontal alignment of the aboveground viaduct
is very constrained by the existing land uses in Wong Chuk Hang and
Environmental factors have been taken into account in
selecting the horizontal alignment of the viaduct section. Thus, to the west of WCH Station the viaducts
will be lying to the south of the Staunton Creek nullah while to the east of
WCH Station the viaducts will be lying alongside and across
Selection of
Preferred Option
Taking into account the technical, environmental and social constraints as described above, Options 1 and 2 have not been identified to be practicable options for further consideration. The viaduct option (i.e., Option 3) is therefore selected as the preferred option for the railway section between Aberdeen Channel Crossing and Nam Fung Portal. Table 2.3 summarises the key engineering factors and environmental considerations considered in determining the preferred option.
Table 2.3: Selection of Preferred WCH and OCP Station Locations and Associated Alignment
|
Option |
Engineering Factors, including constraints |
Environmental Benefits and/or Dis-benefits (on relative terms) |
|
Alignment Option 1 – in deep rock tunnel |
§ WCH and OCP Stations and WCH depot would need to be placed deep underground; operational requirements cannot be met; § Not identified to be a practicable option for further consideration |
Dis-benefits: § Greater amount of excavation materials requiring disposal will lead to secondary dust and noise impacts on the sensitive receivers along the disposal route Benefits: § Construction phase environmental impact largely confined to those sensitive receivers situated near the mucking out points. Handling of excavated materials by dump trucks will generate secondary environmental impact (in form of dust, noise and gaseous emissions); § Operational phase noise and visual impacts are largely avoided and confined to those associated with operation of above-ground facilities such as ventilation shafts |
|
Alignment Option 2 – in shallow tunnel |
§ Construction subjected to major technical difficulties and construction risk and will have direct impact on existing land uses (existing shipyard area and Hong Kong Police College Tactical Training Complex), operation of Aberdeen Channel (part of the Channel will need to be closed) and will delay the completion date of SIL(E); § Crossing at Aberdeen Channel will have to be constructed by cofferdam and/or immersed tunnel method; § Substantial site formation works and rock excavation required for construction of WCH Depot causing program delay of about 3 years; § Not identified to be a practicable option for further consideration |
Dis-benefits: § During the construction phase, cut-and-cover construction would result in environmental impacts (in terms of noise, dust and visual impact) on nearby sensitive receivers; § Cut-and-cover construction at major roads would result in traffic disruption, increased traffic congestion and associated noise and gaseous emissions; § Enormous amount of excavated materials (about 1Mm3) requiring disposal Benefits: § Operational phase noise and visual impacts are largely avoided and confined to those associated with operation of above-ground facilities such as ventilation shafts |
|
Alignment Option 3 – on viaduct |
§ Compared with a corresponding tunnel section, construction of a viaduct section can be completed within a relatively short period of time §
Possible horizontal alignment is very
constrained by existing land uses in the built-up area of Wong Chuk Hang and § Only possible alignment for the viaduct in Wong Chuk Hang is along the existing Staunton Creek nullah; |
Benefits: § During the construction phase, quantity of excavated material generated from the Project will be reduced. Direct waste management implications and secondary environmental impact (dust, noise and visual impacts) of the Project are effectively minimised; § Given shorter period of construction associated with viaduct and possible use of precast elements in construction, duration of exposing sensitive receivers to potential environmental impact will be significantly reduced; Dis-benefits: § Sufficient mitigation measures have to be incorporated into the design of the viaduct section to address potential noise and visual impact, though these measures has been demonstrated to be practicable through similar projects completed locally and overseas. |
2.7.5
Section between
2.7.5.1 Location of ADM Station
At the FS stage of the study, it was identified that a
proposed station at Admiralty is preferred over Wanchai as the interchange station
and terminus of the SIL(E) based on both engineering and passenger-handling
consideration. The proposed ADM SIL
Station is located under
Alternative options were considered for the design of the ADM
station itself, including the options for a standalone SIL station versus a
parallel SIL/SCL scheme and a stacked SIL/SCL scheme. The stacked SIL/SCL
scheme has been chosen as the preferred scheme with the main environmental
benefit being a reduced overall duration of major construction at
2.7.5.2 Possible HAV Station
As highlighted in Section
2.1, MTRCL has explored in conjunction with the Hong Kong Jockey Club the
feasibility of providing an additional intermediate station at
¡
The
projected patronage upon commencement of operation of SIL(E) is not high;
¡
Significant
technical difficulties are anticipated in construction and there would be
serious traffic disruption in the vicinity of the tram terminus in
¡
In
order to provide the HAV Station, the alignment of the SIL(E) would have to
deviate from the original alignment that efficiently connects Admiralty with
¡
The
much longer tunnel mean longer construction period, which go against the public
expectations for early completion of the SIL(E).
During the construction phase, a longer tunnel also means
that more construction and demolition materials (C&D materials) will be
generated from the construction works.
Construction works at
2.7.5.3
Alignment of the railway line near the proposed tunnel portal
at
Further evaluation as part of the Preliminary Design exercise
suggested that two options exist with respect to the location of the tunnel
portal at
¡
¡
The Option 1 site is steeply sloping in parts with level
differences across the site. Most of the site is heavily wooded while the
remaining area is covered by a mixture of permanent and temporary village
structures. The Option 2 site is a large approximately rectangular site bounded
by
It was noted that the ex-Canadian Hospital site (i.e., Option 2) has a number of significant advantages over the Wong Chuk Hang Old village site (i.e., Option 1), including environmental merits, as summarised below:
¡
Maximise
separation distance of the portal from
¡
The
length of the viaduct section of the railway is reduced by
¡
The
ex-Canadian Hospital site will not be sterilized by the railway line. The tracks will be carried by an elevated box
structure supported by columns and piled foundation to allow future development
on top to encompass the tracks without affecting the railway operation;
¡
No land
resumption or clearance is required. Old
village will be undisturbed by the works;
¡
Access
to the site can be from Nam Fung Road and Nam Fung Path; therefore works
traffic will have minimal impact on access to the nearby village and school
during the construction phase; and
¡
Emergency
vehicle access to the tunnel portal, as well as maintenance access to the
ventilation building will be directed, off
2.7.5.4 Selection of Preferred Alignment
As the decision made was not to provide an additional intermediate station at Happy Valley as part of the SIL(E) in view of lengthen the construction period and cost of the entire SIL(E) project, the alignment that involved a shorter tunnel between ADM and OCP Stations by adopting a 300m radius curve at each end and then connecting with a straight line as shown in Figure 2.1.1 was selected as the preferred option. Besides, the ex-Canadian Hospital site was identified to be a better location for the proposed Nam Fung Portal than the Wong Chuk Hang Old village site.
After identifying the preferred location of the stations, the areas surrounding the stations which would benefit from the provision of station entrances were identified, taking into account the views received from local residents through the public consultation programme. However, available options of entrance locations were identified to be very limited as impact on private land has to be avoided.
For LET station in particular, due to the hilly terrain of the area, the catchment is located at different levels which poses significant constraints to locate the station entrance. In response to the demands of the local community, the station entrance of LET station has been relocated from the playground of Tung Sing House to the vicinity of the Lei Tung Commercial Centre away from the residential blocks. Potential environmental concern during construction and operational phase such as noise could be minimised. This arrangement also offers better coverage for the residents in the neighbouring estates, however, the average walking distance is lengthened.
Environmental impacts such as dust and noise associated with construction of station entrances and associated adits would be transient and limited to the construction phase, and can be effectively mitigated through implementation of standard mitigation measures.
Ventilation facilities are integral parts of a railway providing the necessary air exchange for the stations and tunnels. After determining the preferred locations of the stations and the preferred alignment of the tunnel sections, careful consideration has been given to the locations and design of required ventilation shafts, cooling systems and other fixed plants to ensure that they are situated away from sensitive receivers as far as practicable and sufficient mitigation measures have been incorporated into the design. It is identified that alternative locations for these facilities are subjected to significant constraints such as technical considerations and construction impact to the local community, given that land resumption should be avoided and the ventilation facilities could not be situated too far away from the stations and tunnel alignment. Locating the ventilation facilities further away will significantly affect the efficiency of ventilation and render additional plants and conduits and thus larger footprint.
To minimise the impact from fixed plant on nearby residential
receivers, most of the SOH and LET stations and tunnel plant will be
accommodated at
A new depot is required to house rolling stock and for
regular inspections, maintenance and cleaning to support the daily operation of
SIL(E) and the possible extension of the SIL(W). The depot provides stabling
tracks, facilities for off-loading rolling stock at the day-end using
maintenance tracks, lifting tracks, Engineer’s Train sidings, wash plant and areas
for accommodation for stores, workshops and plant rooms. Because SIL(E) is a
medium capacity system with shorter trains, the depot required is much more
compact than the traditional railway system operated by MTRCL on the
¡
Depot
Location Option 1 – the former Hong Kong School of Motoring site and the area
in its vicinity;
¡
Depot
Location Option 2 – Wong Chuk Hang Estate site
2.7.8.1 Depot Location Option 1
The area required under Option 1 comprises the former Hong
Kong School of Monitoring site, the existing football field of Wong Chuk Hang
Sports Centre, the existing bus depot and the ArchSD’s District Agreement
Office. The total site area is around
4.75 hectares and the site level varies from 6 to 9.5mPD. The site has an irregular shape (measures
Under this option, the main service entrance for the depot
would be located opposite to the
To allow the tracks to ramp down from the main line level to the
depot level, an extensive ramp structure will be required under this
option. Besides, for avoiding
encroachment of the ramp structure into the Aberdeen Sports Ground, it was also
identified necessary to shift
2.7.8.2 Depot Location Option 2
Under this option, the depot will occupy the Wong Chuk Hang
Estate site that is already vacated for demolition. Compared with Option 1, the site has a much
regular shape and a larger area of about 6.5 hectares bounded by
For the operational phase, there are practicable measures that could be incorporated into the design of the depot to ensure that its operation will not pose any unacceptable noise and visual impact on the nearby sensitive receivers. The effectiveness of these measures has been demonstrated through similar projects of MTRCL.
2.7.8.3 Selection of Preferred Depot Location
Taking into account the factors described above, including environmental considerations, Option 2 was identified to be the preferred option for accommodating the proposed depot, i.e. at ex-Wong Chuk Hang Estate. Effort would be made to reduce the footprint of the depot at the detailed design stage. Potential environmental concerns during construction phase such as dust and airborne noise impact could be further reduced.
With consideration of the service level required, it was identified that a medium capacity railway is appropriate for SIL(E). The rolling stock for SIL(E) is similar to those used in the existing Kwun Tong Line. With the shorter train length (3-cars) of the medium capacity system, length of platforms and stations can be reduced accordingly. In general, this will reduce the potential environmental impact (in terms of extent and/or duration) that would be generated from the project during both the construction and operational phases.
2.8
Consideration of
Construction Methodologies
This section describes the planning of the construction of the project, covering the key aspects including the envisaged methods of construction, work site requirements and locations, requirements on barging points for handling excavated materials, and temporary magazines for the tunnelling works.
Two major tunnels are to be constructed under the project,
including a 3.5km long tunnel from Admiralty to Nam Fung Portal and 1.6km long
tunnel from SOH Station to
2.8.1.1 Tunnel Sections
The tunnelling techniques reviewed for possible use in the Project include drill-and-blast, mechanical boring (i.e., with the use of a tunnel-boring machine), mining and cut-and-cover method. A description of these tunnel construction methods is given in Appendix 2.2, including summary of the environmental merits and dis-merits of these construction methods.
The techniques to be adopted for construction of the tunnel sections depend very much upon the levels of the proposed tunnels and the nature of the substrata and have been selected with the objectives of achieving the safest while most efficient construction approach such that disturbance to existing land uses, including periods of exposing nearby sensitive receivers to environmental impacts can be minimised. The sub-sections below describe the construction methods recommended for the tunnel sections of the Project. The adopted construction methods for the different sections are as illustrated in Figure 2.5.
Nam Fung Tunnel
The proposed Nam Fung Tunnel traverses
Possible construction methods identified for this section are drill-and-blast, cut-and-cover, mining and the tunnel boring machine (TBM) method. In view of the geological conditions, it is likely that construction by drill-and-blast would be more efficient and economical and with less programme risk. Drill and blast tunnelling is well proven technology for tunnel construction in hard rock. With careful control of the quantity of explosives, the generated vibration levels on existing structures (buildings, roads, utilities etc) can be well controlled.
As pointed out earlier, the tunnel alignment has been
selected such that any impact or disturbance to
Lei Tung Tunnel
The proposed Lei Tung Tunnel connects
Sequence of
Works
For construction of both Nam Fung Tunnel and Lei Tung Tunnel, it is envisaged that the construction sequence will involve drilling probe holes and carrying out pre-excavation grouting or support as necessary before initiating blasts and mucking out the excavation. Supports will then be installed before the process is repeated. This construction sequence could ensure that environmental effects such as dust could be effectively controlled.
It is envisaged that in view of access and programme difficulties at the Admiralty end, the Nam Fung Tunnel will mainly be constructed from the Nam Fung Portal. However, given the significant length of the tunnel, construction from the Admiralty end may become necessary when construction difficulties at the Nam Fung Portal end are encountered, which may otherwise create a high risk of programme over-run.
Construction of the Lei Tung Tunnel, including LET Station,
will be accessed from the construction adit to be launched at
2.8.1.2
Viaduct Section and
The viaduct section was designed to allow the use of precast segmental method for the standardised viaducts. Where practicable, the deck will be formed from precast segments which will be manufactured at a casting yard offsite and joined together at their final positions onsite. This approach will minimise the extent and duration of construction activities required onsite and hence potential environmental impact (e.g. in terms of noise from use of powered mechanical equipment) on nearby sensitive receivers.
Construction of the viaducts will generally involve use of in situ bored piled foundations founded on bedrock or seabed. For constructing the viaduct section between the Staunton Creek and the existing slope where a degraded woodland was identified, single bore piles are proposed to be used to reduce impacts to degraded woodlands and slopes as this would affect a smaller area. The viaduct pile caps will be constructed by traditional means. The pier segments will be constructed using precast units as much as possible with some segments constructed in situ due to the complexity of the reinforcement. The pile in Aberdeen Channel for supporting the bridge sections would be constructed in the form of bored piles. The piles construction would be through the placing of steel pile casing and construction of a cofferdam at the pier site in which the seawater trapped inside the casing and cofferdam would be pumped out to generate a dry working environment. This construction method of creating a confined and dry environment for sediment dredging/ excavation could minimise the release of contaminant into the water column.
2.8.1.3 WCH Depot
The proposed WCH Depot is located at the former Wong Chuk Hang Estate. Two platforms with different formation levels had to be formed by open excavation followed by construction of temporary perimeter walls, slope formation works and subsequently foundation and superstructure works.
Two possible construction methods identified for excavation are by breaking and surface blasting. In view of the large volume of spoil required to be removed to create the two formed platforms, it is likely that surface blasting would be more efficient and with less programme risk. With excavation by breaking, noise criteria will limit the number of breakers on-site, slowing the progress to the point where breaking will be inefficient and will take longer time than by surface blasting. Prolonged noise and dust nuisance to surrounding noise and air sensitive receivers was also not preferred from the environmental perspective.
Given the scale of the Project, works areas would be required
for supporting the construction and have been identified for site office,
storage of materials and nurseries. For construction of a new railway system
within a built-up urban environment, identification of available work areas and
work sites represents a significant challenge.
Through the design exercise, a number of work areas and work sites have
been identified and these are shown in Figures
2.6.1 to 2.6.12. The locations
of works areas have been selected with consideration of their accessibility and
suitability for construction works and future permanent facilities. The
above-ground works areas have been minimised to reduce the land take as far as
possible and avoid the potential environmental sensitive areas including
For the works at Admiralty, nearly the whole
The use of the large ex-Canadian Hospital site of
approximately 17,700m2 is critical to the implementation of the
Project, as it will be required for the construction of the Nam Fung Tunnel to ADM
Station and for construction of the viaducts towards
The Citybus Depot site adjacent to OCP Station of approximately 9,000m2 provides an available site for construction of the station and viaducts towards WCH Station. Land contamination in this site is not anticipated based on desktop review and site investigation results. The majority of the Wong Chuk Hang Estate site needs to be excavated for the depot and for construction of the station. Rock crushing facilities are proposed at the ex-Canadian Hospital site and the WCH depot site due to the large amount of rock generated. The rock crushers will be enclosed with appropriate dust extraction and collection system subject to the design of the Contractor to minimize the environmental nuisance. A typical layout of the rock crushing facilities is given in Figure 2.7.
Construction of the viaduct section lying between the Staunton Creek Nullah and the existing slope to the west of WCH Station requires careful planning. Appropriate construction techniques and special equipment will be required to minimise the area of degraded woodland that would be affected and noise impact on nearby sensitive receivers.
Construction of the
It is planned that LET Station and the tunnel to its west
leading to SOH Station will be constructed via an adit from the portal proposed
at Lee Wing Street. The construction
adit will intercept the running tunnel at about 300m from the SOH station at
SOH Station and entrances to the station will be constructed by cut and cover. As no off-road work sites are available in its vicinity, the works will inevitably need to be carried out in stages under a series of temporary traffic diversions. Bulk excavation activities will be carried out under road decks provided by maintenance of road traffic. The decks will also help minimise potential environmental dis-benefits associated with the use of cut-and-cover technique in terms of dust, airborne noise emission and visual impact.
The tunnelling and earth works will inevitably generate a
large quantity of excavated materials. A comprehensive strategy for handling
and where practicable reuse of the materials is essential from an environmental
perspective and to avoid impact on the programme of the construction
works. Unfortunately, the majority of
the rock to be excavated is expected to be of volcanic origin which is
unsuitable for recycling or reuse other than as fill material. With a view to minimizing road-based traffic
and stress on road surfaces, barging points have to be set up nearer the work
sites on coast of Hong Kong
2.8.3.1
Proposed Barging Points at
The temporary barging point at Western District Public Cargo
Working Area, proposed shared use with WIL project, is envisaged to handle the
excavated materials generated from the works site at
2.8.3.2
Proposed Barging Points at
In view of the geographic locations of the major mucking out points, it is recommended that separate barging points should be provided near the mucking out points at Island South for more efficient handling and disposal of the excavated materials, and in order to reduce impacts on traffic and the associated environmental impacts.
The overall traffic impact/congestion and associated environmental impacts would be considerably greater if no suitable locations for the proposed barging points could be identified within the Southern District, as the excavated materials would have to be transported by trucks to dumping facilities outside the district via Pokfulam Road or Aberdeen Tunnel and even the Cross Harbour Tunnel, thus putting additional traffic to the major roads in / outside the Southern District. The progress of the construction works would also be affected.
Various alternative sites including either side of the
Aberdeen Channel, the demolished barging point of Ocean Park project and
seafront locations of
Taking into account land availability, extent and
accessibility to sea front, road and marine traffic constraints, incompatible
facilities and local residents’ concerns, two sites were considered as viable
for locating the barging points on the south side of
¡
Site A
– near
¡
Site B
– near
It is proposed that Site A will be used mainly for disposal of excavated materials generated at works sites in Ap Lei Chau and WCH depot, while Site B will mainly serve construction works for Nam Fung Tunnel. Setting up two barging points at Island South is required to share the delivery volume and therefore minimize the environmental and traffic impact on the local community.
Site A – near
Lee Nam Road
The site is located at the south western portion of Ap Lei
Chau. It comprises
As discussed earlier, an access adit is proposed to be
constructed at
Site B – near
Telegraph Bay
The layout and arrangement of the barging point is shown on Figures
2.6.11. The site is located at waterfront area of
Taking into account the concerns of the local community, the
trucks travelling to the barging point would primarily take the route via
To minimize environmental nuisance, the tipping area at the barging point would be enclosed and covered trucks and wheel-washing bay would be used. The operation of the barging point and the environmental conditions would be closely monitored. The Corporation will continue to maintain communication with the local community.
Refer to the Section 7 Hazard to Life on the selection of temporary magazine sites.
2.9 Tentative Construction Programme
Construction of the SIL(E) is expected to commence in 2011 for completion in 2015. The tentative construction programme is given in Appendix 2.3.
There are several major concurrent
designated projects in the vicinity of the Project’s works areas, as summarised
in Table 2.4. Consideration of concurrent projects
for cumulative environmental impacts would only take into account those with
available implementation programmes as shown in Appendix
2.4. Cumulative impacts from the planned and existing major concurrent
projects, if any, have been assessed in the individual sections of this EIA
study.
Another project, Shatin to Central Link (SCL), is also proposed by the Project Proponent. The enabling works of SCL at Admiralty will be carried out under SIL(E) at the time of the ADM construction and thus it is considered that the cumulative impact from the SCL project had been assessed in this EIA study.
Construction works for expansion and redevelopment of
Table 2.4: Major Concurrent Projects
|
Project |
Planned Construction Period |
|
Central Reclamation Phase III |
2003 to 2012 |
|
Wanchai Development Phase II and Central- Wan Chai Bypass |
2010 to 2016 |
|
Harbour Area Treatment Scheme Stage 2A |
2009 to 2014 |
|
Hong Kong West Drainage Tunnel |
2007 to 2012 |