2.1
The existing Island Line (ISL) of
MTRC provides mass transit railway services to major population and employment
centres along the north
2.2
The Second Railway Development
Study, namely Railway Development Strategy 2000, identified the West Island
Line (WIL), which is an extension of the existing ISL, to serve transport needs
in the Western Districts of
2.3
In January 2003, the Executive Council of Hong Kong
gave MTRC permission to proceed with further planning of WIL. The MTRC then commissioned a feasibility
study of WIL in mid-2003, and handed in a modified proposal to the government
in end-March 2004. In June 2005, the Executive
Council gave the green light for further planning and preparations for
WIL.
2.4
In response to the Government's decision to proceed with
detailed planning and preparations for the West Island Line in June 2005, MTRC submitted an updated proposal for the WIL to the Government in August 2006, setting out the detailed scope, cost and
implementation programme for the project. This EIA study has been conducted based on
this updated WIL proposal. In this
proposal, the WIL will extend the existing MTRC ISL from Sheung Wan to
2.5
The proposal for WIL was in response
to the long standing demands from residents in the Western District for
improved transport. The use of
electrically powered trains which do not have direct emission would enable WIL
to become not only an efficient but environmentally friendly mass carrier. The WIL sited within intensive developments
and employment centres would help encourage the usage of railways and thereby
reduce reliance on road-based transport.
The capacity of the existing heavily-loaded road networks could be freed
up, which would help to improve the current traffic congestion problems. This would also help to reduce vehicular
noise and air emissions, improving overall environmental quality.
2.6
The Project comprises the
following elements:
·
Approximately
·
Three stations: Kennedy Town Station (KET Station);
University Station (UNI Station); and Sai Ying Pun Station (SYP Station)
·
An overrun tunnel extended from KET Station to the
existing Ex-police Quarters site.
·
Ventilation shafts, cooling towers and chillers for
stations and railway tunnel.
2.7
The construction of the WIL would
involve substantial amount of rock excavation of which majority could be
carried out by drill and blast method.
It was estimated that there would be up to 13 number of underground work
faces for drill and blast during the peak construction period. Many of the work faces would involve 2 blasts
per day. Considering the explosives
supply and delivery arrangement by the Mines Division of Civil Engineering and
Development Department (CEDD), a project specific magazine would be necessary
to store the explosives required for the WIL Project (refer to Appendix 10.1 –
Quantitative Risk Assessment for details of arrangement). For safety reasons, it is proposed that there
should be sufficient rock cover for the magazine. In view of this, a temporary magazine is
proposed to be constructed under the western side of
2.8
The excavated materials arising
from the WIL construction would reach ground level via four main construction
shafts respectively located at the ex-Police Quarter at Kennedy Town, Kennedy
Praya site, Hill Road Rest Garden and Sai Woo Lane in SYP. They will be disposed via barging points at
the Kennedy Town Incinerator and Abattoir site (KET Abattoir site) and the
Western District Public Cargo Working Area (
2.9
Minor modification
works will be conducted at the Sheung Wan Station (SHW Station) on existing
ISL. A new track crossover is required in the crossover box but thereafter trains will run on existing
ISL tracks to Sheung Wan
Station. Within the station itself, re-arrangement of
escalators, stairs and ticket gates is planned to convert it from a terminal
station to a line station, together with enhancement of other station
facilities. Works are fully within the existing station.
2.10
Site plans for the WIL elements
described above are shown in Figures
2.1-2.7.
2.11
During the Preliminary Design Phase a range of
options, as discussed below, has been explored for how best to deliver WIL
services to the District. This has included suggestions from the public
gathered as part of the public consultation exercise on the WIL proposals which
started in April 2006.
2.12
MTRC proposes to construct the WIL for the
primary purpose of assisting Government to resolve long-standing and future
transport problems in the Western District. The area is hilly and densely
developed, with no space to develop modern roads except by further reclamation.
Away from reclaimed areas, roads are generally narrow, tortuous and some are
too steep to be accessible by vehicles. Government planning (Territorial Population and Employment Data
Matrices released in November 2003) forecasts an increase in population for
the area served by WIL but exclude two foreseeable developments: the planned
40% increase in student numbers at the University of Hong Kong (HKU) and development at the Kennedy Town abattoir and
incinerator site (the former is an increase of about 20 000 students and the
latter might amount to a population increase of over 5000). The present transport situation would only get worse.
2.13
In the absence of the
WIL Project, the public in the Western District will remain to rely on road-based
transport to travel from the Western District to Sheung Wan and areas along the
north
2.14
Unlike multi-lane highways, no land is sterilized
by the underground railway and no reclamation is required for the construction
of WIL. Very little
space is taken up at surface by entrance and ventilation structures. Hence, key potential
environmental dis-benefits which could be resulted from reclamation for
providing land for new highways, such as water quality impacts arising from
increased sediment loads due to dredging works for the reclamation, visual
impacts due to loss of natural coastlines and ecological impacts due to loss of
natural habitats could be precluded.
2.15
Environmental impacts
associated with traffic congestion problems including emissions of traffic
fumes and noise cannot be disregarded.
If the WIL Project is not to be proceeded, the traffic congestion
problem in the Western District would persist, and local residents would suffer
from the aforementioned environmental impacts.
In light of the above, the Do-nothing
Scenario was not preferred.
2.1
A railway to serve
·
Space available for carrying out cut-and-cover
station box at the narrow
·
As tramways aligns along
·
Cut-and-cover construction would be conducted
immediately adjacent to residential/commercial buildings alongside
·
The cut-and-cover construction would result in
elevated noise as well as dust impacts.
The lack of space would also render it difficult to provide direct noise
mitigation measures, such as erection of noise barriers, to shield noise from
the construction site.
2.2
It was concluded in a
study conducted by MTRC in 1977 that
2.3
In the feasibility
study conducted in 2004, it was proposed to relocate the UNI and SYP Stations
into the hillside (Figure 2.10
refers). This proposal had the principal
advantage of removing many of the problems associated with earlier schemes of
constructing the railway under
2.4
At Government’s request, the 2004 ISL extension
scheme (Figure 2.10) was further
developed in February 2005, reinstating the heavy-rail extension of ISL to KET
via UNI and SYP Stations. All
ISL trains would then turn back on track beyond KET Station, replicating the present arrangement west of
SHW. The passenger interchange between WIL (as the extension of ISL to
2.5
In the preliminary design study,
the preferred alignment for WIL was developed by modifying the 2004 ISL
extension scheme, which has already taken into account the need for avoiding direct
physical impacts on key heritage sites e.g. the
2.6
Three stations are proposed under
the WIL Project to serve the Kennedy Town (KET), University (UNI) and Sai Ying
Pun (SYP) areas. Various options that
were considered together with their respective potential engineering and
environmental constraints are discussed below.
2.7
Three location
options have been identified for the KET Station:
·
KET Station Option 1 – Under Kwun Lung Lau, in a
deep cavern
·
KET Station Option 2 – Under Forbes Street
Playground, in a cut-and-cover box
·
KET Station Option 3 – Under the site of the
Kennedy Town Swimming Pool, in a cut-and-cover box
2.8
One of the key
comments from the public on the location of KET Station would be related to the
need for preserving the tree walls in the Kennedy Town Playground and along
2.9
If the station is constructed
inside a rock cavern, the possible location is considered to be as shown on Figure 2.12. If the station is located any further east or
north, there would be insufficient rockhead.
Even in the location as shown in Figure
2.12, it is necessary for the tracks to be at -38mPD, which requires
maximum gradient all the way from UNI Station.
At this depth, KET Station would be the deepest station on the ISL. Issues of emergency escape and FSD access
would be significant problems.
2.10
It is considered that
construction of the station inside a rock cavern is feasible, however, it was
envisaged that, in view of the varied geology in the area, the construction of
this station option would be difficult.
2.11
The other disadvantage
with this location would be that the station would be further from its main
catchments. According to the preliminary
design information for this option, passengers would have to travel
2.12
Constructing the station
inside a rock cavern would imply that majority of the construction works would
be conducted underground. In so doing,
impacts of noise and fugitive dust emission as well as visual impacts during
construction phase could be reduced. The
adoption of this station option would have no adverse impacts on the mature
trees at Kennedy Town (KET) Playground and tree walls at
2.13
Figure 2.13 shows the proposed layout for the station
located under the existing Forbes Street Playground. The eastern end of the cut-and-cover box is
just to the west of the swimming pool complex.
2.14
The station is
oriented such that the eastern approach tunnels just avoid passing under the
main pool. However, the tunnels may
still impose some settlement effects on the unknown pool foundations. Furthermore, the tunnel will pass under the
plantrooms, the grandstand and other facilities. Even with the track level at -12mPD, it is
expected that these facilities will need to be closed/demolished before
construction, requiring the closing of most or all of the pool complex during
construction, and significant rebuilding and remedial works afterwards.
2.15
The station box would
be too long to fit in the space between the pool and the main transverse tree
wall in the KET Playground, and it is thus necessary to add a separate section
of cut-and-cover box under the basketball court. This smaller box would be connected to the
main box at track/platform level by two independent soft-ground tunnels under
the transverse tree wall.
2.16
The cut-and-cover
station box would encroach into the protection zone for the tree walls, as
shown on Figure 2.13. Adverse effect on the root system of the tree
wall would be envisaged.
2.17
Another major issue
with this scheme would be the possibility of ground movements affecting the
tree walls. With cut-and-cover
construction over
2.18
Under this option,
the only location for the ventilation shafts would be within the playground.
Majority of the playground area would then need to be permanently allocated to
the WIL to accommodate these facilities.
Landscape impacts due to permanent loss of the KET Playground would be
envisaged. During construction, the
entire Forbes Street Playground would have to be closed. (The PTI is not
connected to this project and should not be included as it is Government’s
extra over.)
2.19
Figure 2.14 shows the proposed layout for the station
located in a cut-and-cover box, a significant proportion of which would be
constructed under the existing KET Swimming Pool Complex.
2.20
The western portion
of the station would be under the football pitch of KET Playground. With part of the station (eastern end)
located under the swimming complex, it would be possible to keep the entire station away from the tree
wall protection zone and maintain greater clearance to the tree wall than
Option 2. However, a short section
(approximately
2.21
The track level is at
approx. -7mPD,
2.22
Some of the
ventilation shafts can be provided on the existing swimming pool site, thus
minimising permanent loss of KET Playground.
2.23
The KET Playground
would be re-instated after construction of the stations.
2.24
A summary of the reasoning that
has been considered during the process of preferred option selection is given
below.
Table 2.1 Selection
of Preferred Option for KET Station
|
WIL Element |
Option |
Description |
Engineering Factors |
Environmental Benefits & Dis-benefits |
|
KET Station |
1 |
Cavern under Kwun Lung Lau |
-
Tracks to be at -38mPD in order to have sufficient rockhead. This arrangement would require maximum gradient
all the way from UNI Station. There
would be emergency escape and FSD access issues. -
KET Station is in volcanic rock, and would be expected to be more
heavily fractured than the granite at the UNI and SYP areas. Heavier support and more advance grouting
to control groundwater would be necessary.
Longer construction time would be needed. -
Location would be further from its catchments. Passengers would have to travel |
-
Majority of construction activities would be conducted
underground. Construction noise, dust,
landscape and visual impacts associated with surface works would be limited
to activities conducted at construction shafts only. -
Higher energy consumption would be necessary in the long run to convey
the passengers to and from the deep cavern and the ground. |
|
|
2 |
Cut-and-cover box under Forbes Street Playground |
-
Tunnels may impose settlement effects on the unknown pool foundations. -
Possibility of ground movement affecting the structural stability of
the tree walls |
-
Encroachment into the tree protection zone -
Possibility of ground movement would have adverse impact on the tree
walls -
Construction noise, dust, landscape and visual impacts due to
cut-and-cover construction. -
Permanent loss of landscape resource – KET Playground and Forbes
Street Playground |
|
|
3 |
Cut-and-cover box under Kennedy Town Swimming Pool |
-
Better accessibility as compared to the other 2 options -
Significant portion of the station is located under the existing
swimming pool complex. -
Some of the ventilation shafts can be provided on the existing swimming
pool site, thus minimizing permanent land-take from the Forbes Street
Playground. |
-
The siting of the entire station would only result in minor and local
encroachment into the tree protection zone.
Greater clearance to the tree wall than Option 2 can be
maintained. -
Since the depth of excavation can be reduced by about -
Compared to Option 2, duration of construction noise, dust, landscape and
visual impacts due to cut-and-cover construction could be shortened because
of reduced extent of excavation. |
2.25
KET Station Option 1 would appear
to be technically feasible, although it would be difficult to resolve the emergency
escape and firemen’s access issues. The
station would be located in a deep rock cavern well away from the main
catchment, and will be the deepest station on the ISL. The overall impact of this option would be
poor accessibility, longer construction programme and increased cost. Under this option, majority of construction
activities would be conducted underground.
Construction noise, dust, landscape and visual impacts associated with surface works
would be limited to activities conducted at construction shafts only.
Nevertheless, higher
energy consumption would be necessary in the long run to convey the passengers
to and from the deep cavern and the ground.
2.26
The main problems associated with
KET Station Option 2 are:
·
The station box substantially encroaches into the
tree wall protection zone, posing a significant threat to the well-being of the
trees
·
As the cut-and-cover construction is much deeper and
much closer to the tree wall than for other options, significant ground
movements are more likely – these could adversely affect both the trees and the
wall.
2.27
KET Station Option 3 minimises the
risk to the tree wall, and provides entrances which better serve the overall
catchment. It also minimises the impacts
to the Forbes Street Playground. Taking
into account these favourable factors, KET Station Option 3 is considered to be
the optimum scheme for KET Station.
2.28
The proposed station
location is beneath
2.29
The location and
level of Sai Ying Pun (SYP) Station are largely determined by the need to
provide sufficient rock cover for the station cavern, and by the rail alignment.
The alignment is in turn dictated by the need to connect to the existing
overrun tunnel at Sheung Wan. This
section of the rail alignment is very heavily constrained by existing building
foundations and the proposed development by Urban Renewal Authority at
2.30
Furthermore, the
tunnels between SYP and SHW Stations are in mixed ground and will require
tunnelling under compressed air, which constrains the maximum tunnel depth to
comply with health and safety requirements for works under compressed air. From the point of view of passenger
accessibility, it is also desirable to minimize the depth of the station below
ground level. All these factors have been taken into account in determining the
location and level of the station cavern.
2.31
As in the case of UNI
Station, no major options were feasible for SYP Station location due to the
severe alignment constraints.
2.32
The WIL lies within a densely developed
urban area, the selection of entrance locations would therefore be heavily
constrained by the availability of land given it is the government policy to
avoid resumption of private land. Most of the entrances have therefore
been
located in existing open space or, where possible, on the site of an existing
government facility. The priority has been to avoid impacts on mature trees and to locate entrances such
that the maximum potential open space can be reinstated upon completion of
construction. It can be seen from Outline Zoning Plans (Figures
2.33
Some entrances were added as a
result of surveys of public opinion carried out by MTRC. The
2.34
Ventilation shafts serve a dual purpose. In
normal operation, they are the route for air exchange for the
railway system. In emergency mode, they are an essential
component of the smoke control system. A ventilation shaft may also be the site of heat
exchanging plant for the station/trackway air conditioning.
2.35
As is to be expected in planning an underground
mass transit railway in a heavily developed area, it is difficult to find
suitable locations for above-ground ventilation shafts. Additionally, it is noteworthy that in order
to efficiently serve their function, the vent shafts could not be located too
far away from the tunnel alignment.
Alternative locations for vent shafts available for consideration would
be therefore highly limited and generally they have been confined to be
constructed in combination with entrance structures such that the land take is
kept to an absolute minimum. The vent shaft for the overrun tunnel at the west of KET
Station would be an exception. As the
overrun tunnel would be extended to areas with more vacant land, variations in
the location of this vent shaft could be allowed.
2.36
The vent shaft for the overrun
tunnel would be used not only as a ventilation point but also as an at grade
portal for tunnel construction and track installation. The shaft is also needed in the permanent
case for fire escape. As such the vent shaft shall require an access road
during construction which will need to be converted to a permanent EVA to the
vent shaft in the long term. Three alternative proposals as shown in Figures 2.15-2.17 have been considered.
2.37
The vent shaft proposed under
this option will be located at the site of Ex-Police Quarters at
2.38
The vent shaft proposed in this option is placed at the toe
of the slope near the existing petrol station on
2.39
The vent shaft proposed under
this option will be located higher up the slope compared to Option 2 (Figure 2.17). Whilst it will require
less cut and fill than option 2 it will still require substantial earth works
in order to create the platform and build the access road.
2.40
As it can be seen
from the above, given the terrain in the vicinity of the proposed shafts, it is
unavoidable that substantial formation works and retaining structures would be
required to create a suitable working platform and access road. Since only limited geotechnical information
for the three proposed shaft locations is available, the extent of slope
stabilization which may be required beyond the platform areas cannot be
evaluated at this time without further geotechnical investigation. However, based on the information available
at the time, it would be likely that more extensive slope stabilization would
be required for VS Options 2 and 3.
Certainly Option 1 can take advantage of the existing road for access
which can avoid a lot of additional earthworks.
As compared with the Options 2 and 3, this option would have less
landscape and visual impacts since less earthworks would be needed. Additionally, the quantity of construction
waste arisings would be reduced due to reduced extent of earth works. As such, Option 1 has been selected as the
preferred option.
2.41
The entire WIL
alignment will be constructed underground.
Airborne or viaduct-radiated railway noise impacts on sensitive
receivers in the Western District will be fully eliminated. Ground-borne railway noise of the WIL
alignment would be controlled through adopting appropriate trackform, as
discussed in Section 4. The preferred
WIL alignment scheme has been designed to eliminate the need for reclamation
and its associated environmental impacts, as compared to the alignment schemes
developed previously. Considerations
have also been given in the design of the WIL alignment scheme such that
demolition of any
2.42
Options for KET
Station were considered, and their environmental benefits and dis-benefits are
compared and presented in Table 2.1. Apart from construction risk and safety
issues, due efforts have been given in preserving the tree walls at
2.43
For UNI and SYP
Stations, no major options were feasible due to the severe alignment and site
constraints. Environmental factors would
not play a significant part in the selection of the sites for these two
stations given the engineering constraints presented in Section 2.43-2.46.
2.44
Given that the WIL
lies within a congested urban area, the siting of vent shafts is subject to
significant constraints such as engineering, available land and environmental
factors. Sites suitable for the construction of vent shafts are therefore
highly restricted, and alternative sites are generally not available. It should be noted that in accordance with
the Government policy, the resumption of private buildings should be avoided as
far as possible. In searching for
suitable land for constructing the vent shafts, public open areas have to be used
as a priority. Given the potentially
high construction noise levels that would be generated from the demolition of
buildings, resumption of private buildings to provide space for constructing
the vent shafts would not be preferred from an environmental protection
perspective. All these factors have
added to limit the choice of sites for constructing the vent shafts.
2.45
Due efforts have been
given in searching for suitable sites for vent shafts whereby environmental impacts
associated with the construction and operation of vent shafts would be
minimised. The use of the site located
near the bus stop outside the
2.46
Suitable alternative
sites for vent shaft in the waterfront areas have also been explored. However, these locations would be too far
from the station and tunnels that they serve. Therefore, alternative sites in
the waterfront areas were considered not feasible for the use of vent
shaft.
2.47
Furthermore, the
option of siting the vent shaft at
2.48
As discussed in Sections 2.49-2.52, alternative locations
available for consideration were the vent shaft for the overrun tunnel, which
would be extended to areas with more vacant land. Environmental benefits of the preferred
option over the others are presented in Section 2.53 above. Further discussions on the environmental
aspects of the proposed vent shafts are presented in Section 2.117-2.123.
2.49
The basic tunnelling methods
considered for the Project are:
·
drill-and-blast
construction technique
·
mechanized
boring, in which the tunnel would be excavated mechanically with a
tunnel-boring machine
·
cut-and-cover
tunneling techniques
·
sequential
excavation method, a form of mining that involves excavation with roadheaders
and other such equipment and includes ground-modification techniques such as
ground freezing, grouting, etc.
2.50
For most tunnelling projects in rock, the ground is
somewhere between two extreme conditions of hard rock and soft ground. The tunnel face may have a certain self-supporting
stability, yet support measures are necessary.
For
this Project, the classical drill and
blast excavation method may be a cost effective solution.
2.51
Drill and blast techniques are considered feasible for most
rock tunnel sections on this Project, and may also show that a large tunnel section with
about a 12 m span to accommodate twin tracks is feasible. Using advance blasting and monitoring
techniques, the generated vibrations to the existing buildings and utilities
could be well controlled to acceptable levels.
2.52
The successful application of a tunnel boring machine to
bore tunnels depends on the selection of the most suitable equipment and
cutting tools for the rock mass and ground conditions to be encountered.
2.53
A full face tunnel boring machine (TBM) may be suitable
where competent rock alone provides the stability of the tunnel excavation for
a long enough section without structural support, and when the ground is fairly
homogenous along the entire tunnel length to be driven by the boring machine.
2.54
If the ground is so weak that the tunnel face needs
permanent support during excavation, the tunnel may be driven by employing a
shield and by providing immediate support by the provision of pre-cast
segmental linings.
2.55
It is considered feasible to bore most of the tunnel
sections in rock with adequate rock cover using a hard rock TBM and line the
tunnels with cast-in-situ concrete. It
is noted that the extremely hard rock (eutaxite) in the volcanic on the west of
Hong Kong Island can cause excessive TBM cutter wear, and this will be an
important factor to be assessed in determining the cost-effectiveness of a TBM
drive.
2.56
The cut-and-cover method of tunnelling entails excavating a trench,
constructing a tunnel within it, and then covering it with soil. To avoid long-term disruption, and to restore
pedestrian and vehicular traffic as soon as possible, the trench is usually
covered with a temporary deck following excavation.
2.57
Cut-and-cover construction accommodates changes in the width
of the tunnel and non-uniform shapes, which are necessary to build stations and
portals. Diaphragm walls, which are
often used to support the vertical sides of the excavation, may serve as either
temporary or permanent support for the tunnel.
They will generally be used as part of the permanent tunnel structure.
2.58
Sequential Excavation Method, also known as the New Austrian
Tunnelling Method (NATM), entails dividing the space to be excavated into
segments, then mining the segments sequentially, one portion at a time, using
supports. Mining equipment, such as
backhoes and roadheaders, are used to excavate the tunnels. This method is slow,
but it can be especially effective in certain areas, for example, around a
subway or a sewer that cannot be relocated where special care is required to
protect it.
2.59
Whereas TBMs can excavate only a fixed, generally circular, shape
the sequential excavation method allows a tunnel of any shape to be
excavated. The method is especially
applicable for areas, such as cross-over and bifurcation, in which the tunnel
shape or size needs to change.
2.60
To use the sequential excavation method, the ground must be
completely dry and it will be generally necessary to dewater the ground prior
to excavation. Ground modifications, to
strengthen and prepare the soil for tunnelling, are also common with this
method. These include various types of
grouting (injection of chemical or cementing agent into the soil), ground
freezing, and other such treatment.
Potential environmental impacts of ground treatment would mainly relate
to construction noise impacts arising from the use of powered mechanical
equipment such as drill rig, grout pump and grout mixer.
2.61
Given the size of the
WIL rail tunnel, mini and micro-tunnelling is considered not applicable to the WIL
project as this method would generally be used for utility projects (i.e.
drainage and sewerage) only.
2.62
The preferred construction method would be predominantly
determined by the site conditions, site
constraints, contemporary tunnelling methods as well as cost-effectiveness.
2.63
For the WIL tunnels through the
volcanic granite rock masses temporary face stability should not be a key issue
except local to fracture zones and faulted ground. For the excavation of these tunnels, TBM
systems or drill and blast method are the available methods to select from.
2.64
TBM systems are commonly used for the excavation of long tunnels. The advantages of excavation by TBM are relatively
high production rates compared with alternative methods for rock excavation, a
controlled excavation profile, and low vibration and noise generation.
However, the use of excavation by TBM systems would generally involve
continuous operation, which often would be a main source of ground-borne
construction noise impact.
2.65
Excavation by drill and blast method is not a continuous operation and in general therefore has lower production rates than TBM excavation. The progress rates for blasting are affected by the time to
drill the holes, charge the explosive, remove the material and install
temporary supports. In addition, the progress is affected by the delivery of
the explosives and the need to retain blast induced vibrations within the
threshold limits. Generally, blasting results in higher vibration levels than TBM excavation, but for less duration.
2.66
Excavation of tunnels
between KET and SYP Stations by the use of TBM systems was reviewed for
practicality of constructing different tunnel / track arrangements. Although high progress rates are achievable
with TBMs, the layout of WIL does not lend itself to their use. Drill and blast tunnelling in rock is better
to manage risk issues and will, in any case, be required for excavation of
caverns, entrance and ventilation adits.
2.67
For this EIA study, both drill
and blast and TBM methods were considered, and the assessment was conducted
based on the worst-case option where appropriate. As far as ground-borne noise impact is concerned,
the worst-case option for tunnelling would be TBM systems. With regard to indirect vibration impacts on
heritage buildings, the worst-case would be the drill and blast option as it
would generate higher vibration levels than TBM excavation. Additionally, if the drill and blast option
would be adopted for the WIL construction, a temporary underground magazine for
overnight storage of explosives would be needed. In connection with this, this EIA study also
covers the assessment of potential hazard to life issues associated with the
construction and operation of the temporary underground magazine at
2.68
The preferred construction method and sequence of works have
been predominantly determined by the site conditions and constraints, contemporary tunnelling
methods as well as cost-effectiveness.
Therefore environmental comparison of applying different construction
methods and sequence of works is not relevant in this case.
2.69
The WIL will be constructed
through the densely built up urban environment of Western District. The lack of space available at the surface
for locating entrances and railway facilities and for working space poses great
constraints to the planning, design and construction of the railway (refer also
to relevant discussions in Section 2.59).
The proposed location and size of works areas are largely confined to the site of permanent works (e.g. entrances, vent shafts and
KET Station). While works at surface would in any case be
carried out at these works areas, it would be futile to seek out alternatives
for these works areas (i.e. Works Areas A, C, D, H-J, J1-J3, L1, M1, M3 and
N1).
2.70
In addition to the
site of permanent works, works areas of the size required for temporary works would be needed to
support the WIL construction. These
areas would be necessary for the provision of contractor’s facilities, storage,
workshops and site offices, as well as barging points for efficient removal of spoil
would be required. Since these works
areas would need to provide potential barge loading-out points for spoil
disposal, they would be waterfront sites.
2.71
Having regard to the
above, two large areas have been selected on reclaimed land near
2.72
The site for this works area
(Works Area B) was previously occupied by the Kennedy Town Incinerator Plant
and Kennedy Town Abattoir. An EIA study
for the “Demolition of Buildings and
Structures in the
2.73
The EIA Report for the KTCDA
Project was submitted by
CEDD in September 2001 for application of an environmental permit
(Application No: AEP-136/2002). The report was approved on 16 April 2001 and
an environmental permit (EP) was granted on 22 May 2002 (EP No: EP-136/2002).
2.74
CEDD, the Project Proponent of
the KTCDA Project, sought the approval for varying the conditions of the
environmental permit granted, to accommodate the need for utilising part of the
KTCDA site (the KET Abattoir Site) for temporary site offices and material
storage uses. An
Environmental Report for Variation of Environmental Permit (VEP) Application of
“Demolition of Buildings and Structures in Proposed Kennedy Town Comprehensive
Development Area Site” (the VEP Report) submitted by CEDD was approved by EPD
under the EIAO in April 2007.
2.75
Under the VEP
application, CEDD is permitted to implement the KTCDA project in two
phases. Phase 1 would comprise
demolition of buildings and structures in the
2.76
The use of the KET
Abattoir Site as a works area for WIL would be subject to the conditions and
requirements set out in the VEP report and the Environmental Permit (No: EP-136/2002/B). It was assumed in the VEP report that the
site would be for WIL site offices and storage of material uses.
2.77
The proposed uses for the WIL works area at
KET Abattoir Site include:
·
Project
offices for MTRC and Contractors
·
Site
offices, stores and workshops, welfare facilities
·
Receiving
and stockpiling area for excavated spoil
·
Loading
point for spoil barges
·
Landing
and storage area for pre-cast tunnel lining segments
2.78
To facilitate the
construction of WIL, an additional use of the KET Abattoir Site for rock
crushing is proposed. Potential
additional environmental impacts in relation to the proposed rock crushing use
are addressed in this EIA report, including health risk issues associated with
contaminated soil, noise, waste, water quality and dust
impacts as highlighted below.
2.79
The human health risk
issue associated with the contaminated soil and groundwater in
-
a paving layer (not less than
-
the site office at the area should be built as a raised
structure to provide sub-floor ventilation and gas-resistant membranes should
be properly installed and maintained to prevent vapours from soil and
groundwater underneath from entering into the site office
2.80
As indicated in the
VEP Report, there would be no unacceptable land contamination and human health
risk issues as long as the concrete paving would be constructed and remained
intact to act as an integral physical barrier.
The thickness of the concrete paving was determined to be no less than
2.81
To cater for the loadings
from the proposed additional rock crusher use, the adequacy of the
2.82
Other environmental
issues including noise,
waste, water quality and dust impacts associated with the KET Abattoir Site
works area including the rock crushing use have been assessed and necessary
mitigation measures recommended, in Sections 3, 7, 9 and 11 of this EIA report
respectively. With reference to the EIA
findings, no unacceptable environmental impacts were envisaged with the
recommended mitigation measures in place.
2.83
An implementation schedule specifically
for the works area at the KET Abattoir Site is provided in Table 14.2.
2.84
The
2.85
As compared to the works areas
for permanent works, it should be noted that Works Areas B and E are relatively
distant from noise sensitive receivers.
As a result of this, construction noise impacts from the activities
conducted at these two areas could be minimised. Alternative sites
for these two works areas would not be available mainly because of the lack of suitable
waterfront sites in the project area.
2.86
The construction of
the WIL will involve substantial amount of rock excavation of which majority
will be carried out by drill and blast method. Having considered the explosives supply
and delivery arrangement by Mines Division, it was determined that delivery
from Mines department alone could not satisfy the demand for explosives on this
project. As such it was concluded that a site magazine was needed for overnight
storage of explosives.
2.87
Ideally the location
of the magazine should be close to the proposed point of use such that transportation distances can be
kept to a minimum. As all of the sites
requiring explosives are in the north-west Hong Kong island area the search for
a suitable magazine site centred on
Site
Magazine Option 1
2.88
The first option was to locate the
magazine underground in a tunnel off
Site
Magazine Option 2
2.89
The site magazine location under
this option was
identified at the site of a former ammunitions store just off
Selection
of the Preferred Location
2.90
The preferred location for the
site magazine was eventually chosen as the
·
This site was the most remote from
population and therefore offered the least risk.
·
The site was the closest by road
to the WIL works areas which meant that the
transportation distances for explosives would be kept to a minimum.
·
The site had relatively good
access and a platform of land was identified for access to the magazine.
·
The site could be secured in
accordance with Mines Department and police directives.
·
The site is accessible for FSD
appliances in the event of an accident.
·
No land
contaminative uses were identified near this site, in contrast to Site Magazine
Option 1.
2.91
A temporary underground magazine
site will therefore be built at
2.92
An assessment of potential
impacts on ecology for the proposed underground magazine site has been
conducted. Impact on the existing ecological
resources is considered minor. Details can be found in Appendix 2.3.
2.93
Soft/mixed ground
tunnel excavation will be conducted between SYP Station and Sheung Wan (SHW)
Station. Ground treatment will be
required to secure the shield / launch chambers and to stabilise non-cohesive
alluvium in, or adjacent to, the tunnel face.
For the proposed tunnel alignment, ground treatment will be carried out
at three locations namely
2.94
There are only two options to treat
ground in advance of the tunnelling. The first is to treat from the surface and
the second is to treat from the tunnel face as it is advanced. Wherever
possible access from the surface is preferred as it is possible to get better
control over the ground treatment process and thereby gain more confidence with
regard to the quality of the ground treatment. This in turn reduces the risk to
tunnelling in this extremely constrained environment with limited
accessibility. Having examined the tunnel alignment and the areas requiring
ground treatment it became evident that access for ground treatment from the
surface was feasible at the three locations named above. As such the EIA
assumes that these three sites will be made available for ground treatment in order
to reduce the risk for this very difficult tunnelling project.
2.95
Table 2.2 presents a summary of all works areas required for supporting the
construction of WIL. The works areas
locations have been
selected for their suitability as sites for permanent WIL facilities or
temporary works areas. It should be noted that other sites were also examined but rejected
because they were too small, too remote from the alignment or permanent
facilities are no longer to be constructed there.
2.96
Figures 2.19 - 2.25 show the locations of the works areas listed in Table 2.2.
Table 2.2 Major
ground level works areas / works sites for railway works
|
Site Ref. |
Figure No |
Location/Description |
Existing Usage |
Proposed
Usage |
|
MA |
2.20 |
Below |
Vacant |
Temporary underground magazine |
|
A |
2.21 |
Blocks A
and C, Ex-Police Quarters, |
Vacant |
Tunnel
construction access, Vent shaft for KET overrun tunnel |
|
B |
2.21 |
|
Disused facility |
Barging
point and explosives berth, rock crushing facility, spoil stockpile, tunnel
lining storage, site offices, contractor’s site facilities |
|
|
|
|||
|
|
|
|||
|
C |
2.22 |
Kennedy Tower Playground, temporary
playground and football field at |
Playground, football field and toilet |
KET
Station structure (entrances and ventilation shafts). KET Station
construction site. |
|
D |
2.22 |
|
Public swimming pool |
KET
Station structure (entrances and ventilation shafts, PTI). KET Station
construction site. |
|
E |
2.22 |
Western District PCWA |
Public cargo working area |
Barging
Point |
|
F |
2.23 |
Public road outside Western District
PCWA |
Public road with parking meters |
Support
for overhead conveyor system |
|
G |
2.23 |
Car Park at |
STT car park |
Tunnel
construction access and contractor’s site facilities |
|
TGLA site |
HyD site compound |
|||
|
H |
2. 23 |
Roadside amenity at Belcher’s Street
/ The Belcher’s |
Sitting out area and access road to
The Belcher’s |
UNI
Entrance C2. Construction site. |
|
I |
2. 23 |
Roadside amenity |
Roadside amenity |
UNI Entrance
C1. Construction site. |
|
J |
2. 23 |
|
Garden |
UNI
Entrance B2. Construction site. |
|
J1 |
2. 23 |
|
Footway |
UNI
ventilation shaft. Construction site. |
|
J2 |
2. 23 |
|
Substation, slope |
UNI Entrance
B1. Construction site. |
|
Whitty Street Public Toilet |
Public toilet |
|||
|
St Anthony’s School |
Slope |
|||
|
J3 |
2. 23 |
HKU Area / |
HKU footpath and road |
UNI
Entrance A. Construction site. |
|
K |
2.24 |
Vacant site (formerly Mui Fong Street
Cooked Food Bazaar) |
Vacant |
Open space
reprovisioning |
|
L |
2.24 |
Children’s playground at |
Playground |
Contractor’s
site facilities. |
|
L1 |
2.24 |
Children’s playground at |
Playground |
SYP
Entrance B3. Construction site. |
|
M |
2.24 |
|
Basketball court and park |
Tunnel
construction access. |
|
M1 |
2.24 |
Centre Street Market West Block |
Market and Government offices |
SYP Entrance
B1/B2. Construction site. |
|
M2 |
2.24 |
David Lane
Sitting Out Area |
Sitting out
area |
Temporary public toilet and transformer room reprovisioning. |
|
M3 |
2.24 |
David Trench Rehabilitation Centre |
Rehabilitation centre |
SYP Entrance
C (entrance, ventilation building and shaft). Construction site |
|
N1 |
2.24 |
Sai Woo Lane Playground |
Playground |
SYP
Entrance A1 (entrance, ventilation building and shaft). Tunnel construction
access, contractor’s site facilities. |
|
2 Tsz Mi Alley |
Building |
|||
|
4 Tsz Mei Alley |
Building |
|||
|
203-209 Queen’s Road West |
Building |
|||
|
|
|
Health Gate Medical Centre |
Building |
SYP
Entrance A2 (inside Health Gate Medical Centre) |
|
O1 |
2.25 |
|
carriageway |
Ground
treatment |
|
O2 |
2.25 |
Wing |
carriageway |
Ground
treatment |
|
O3 |
2.25 |
New |
carriageway |
Ground
treatment |
2.97
As compared to any aboveground
rail system, the WIL would require less land at surface for its construction
since majority of the WIL elements would be constructed underground. For the WIL project, surface works areas
would mainly be confined to the site of permanent works such as entrances and
vent shafts.
2.98
Since the Western District is a highly
developed area, demolition of some existing buildings would be necessary
to create space for WIL works areas.
Due considerations would thus need to be given in using the available
land for use as works areas as efficiently as possible so that the size of the
works area could be kept to absolute minimum and the need for building
resumption could be minimised. Also
environmental impacts associated with demolition of buildings such as high
construction noise impacts can be avoided.
However, since land availability is an intrinsic constraint to WIL
construction, resumption of some of the existing buildings would be necessary.
2.99
The WIL works areas have been
designed to reduce their footprint at surface as far as practicable so that
environmental impacts and disturbance due to building demolition / resumption
can be averted. For instance, entrances
which are to be served by lifts would be smaller than those served by
escalators. As a result, the size of
works areas for these entrance structures can be reduced. Those entrances to be served by lifts would
include Entrance A and C1 for UNI Station, and Entrances B1 and C for SYP
Station. However, it would only be
efficient to adopt the lift option for entrances located in steeply sloping
areas.
2.100
When selecting the
preferred option, major factors that were considered included not only the
engineering factors and environmental factors, but also views from the public received
during the public consultation exercise.
2.101
As one of
the WIL Project Objective, an extensive series of
meetings/consultations with public has been conducted on the planning and design of the WIL since early planning stage of the
Project, with an objective
to formulate a final scheme which meets the needs of the local community and is
fully supported by the general public. Appendix 2.4 provides a list of the public
consultations conducted since the feasibility study of the WIL in mid 2003 and
a summary of the key public
feedback on the Project. The public generally welcomes and looks forward to the
implementation of WIL as early as possible. In response to comments
received, some modifications have been made on the design of the Project to
address their concerns, as highlighted below.
2.102
KET Station is a good demonstration of this process of balancing railway needs
against environmental concerns. It sits on the alignment designated for
WIL for many years on the Town Planning Outline Zoning Plan, straddling
2.103
During the public consultation
exercise, the Project Proponent was requested to design and locate the vent shafts
such that environmental impacts including fixed plant noise (fan noise), air
quality and visual impacts associated with their operations could be
minimised.
2.104
In response to comments from the
public, the vent shafts will be designed to present minimal environmental
impacts as far as practicable, following assessment findings of this report,
including:
· Quieter plant such as those which have been effectively silenced would be chosen where necessary.
· Noise levels specification would be included when ordering new ventilation equipment.
· Direct noise mitigation measures including silencers, acoustic louvers and acoustic enclosure would be installed where necessary.
· Louvres of vent shafts would be located away from sensitive receivers as far as practicable.
· Vent shafts would be sensibly designed to blend in to the existing urban context
· Planting would be encouraged to soften the visual impact of the vent shafts where possible.
2.105
Potential ventilation
shaft noise impacts are assessed in Section
3 of this report. In accordance with
the assessment results, the ventilation shafts would be designed to comply with
the specified noise limits with no adverse impacts.
2.106
WIL is an electric railway, and so
there would not be any emissions from fossil fuel generated within the rail
system. The only source of carbon
dioxide (CO2) would be from the breathing of the
passengers and staff working in the station.
The ventilation system is designed for an air exchange rate of 5
litre/person/second in accordance with MTRC Design Manual. As a result, all CO2 exhaled by
passengers/staff would be sufficiently diluted by the fresh air intake before
being discharged through the normal air exchange. Similar to other electrified
rail projects with substantial sections underground (e.g. Kowloon Southern
Link), air quality impact from the operations of vent shafts would not be
considered a key environmental issue.
2.107
There is very few source of dust
inside the railway system. MTRC has
commissioned a monitoring programme on the dust level at a vent shaft in
Central and benchmarked the results with a nearby EPD continuous air quality
monitoring station. The measurement
results indicated that the dust level at the vent shaft area was no worse than
any other spots in Central where the air quality was found to be affected
predominantly by road traffic emissions.
2.108
The vent shaft is also designed
to be sited at more than
2.109
The proposed Project
construction commencement dates have been tentatively scheduled as shown in Table 2.3. The construction programme is presented in Appendix 2.2 for reference. The assessments in this report are based on
this programme.
Table 2.3 Tentative Construction Works Schedule of the Project
|
Location |
Tentative
Commencement Date |
Tentative
Completion Date |
|
KET |
Early 2009 |
Late 2013 |
|
UNI |
Mid 2009 |
Early 2014 |
|
SYP |
Late 2009 |
Early/Mid 2013 |