2.1.1.1 Several options and alternatives have been considered in the development, refinement and selection of the preferred scheme for the KTE to be taken forward for environmental assessment and detailed design. This section of the report provides the details of the project options considered and the constraints and considerations assessed in adopting the preferred scheme.
2.1.1.2
In addition, as part of
this process, the various construction methodology options available have been
reviewed in order to determine the most effective means of building the
project. The review has taken into account engineering feasibility, site
conditions, programme aspects and environmental considerations.
2.1.1.3
The Preliminary Design for
the project has considered a number of options for the major elements of the
rail extension, including rail alignment and stations, and the construction
methods with a view to identifying the optimum arrangement. These considerations have been influenced by
feedback from the Public Consultation programme, from Value Engineering studies
and technical review and have led to the proposed project evolving into a
preferred option / scheme. The
alternatives and the factors considered are discussed below.
2.2
The Without Project Alternative
2.2.1
The ‘Do-nothing’ Option
2.2.1.1 A fundamental project alternative is the option not to implement the KTE project, which in environmental terms is often referred to as the ‘Do-nothing Option’. However, the extension of the existing MTR Corporation KTL from YMT Station to the major population and employment areas of Ho Man Tin and Whampoa is a long standing ambition for the many residents and workers in the area.
2.2.1.2
In the absence of the KTE
project, the public including residents and workers in the Ho Man Tin and
Whampoa areas would continue to depend upon road-based transport (buses,
motorbikes, cars and taxis) to travel to and from central
2.2.1.3 For the above reasons the Do-nothing Option is not preferred and is not considered to be an environmentally preferred solution to the existing transport issues, pollution and problems and is not further discussed in this report.
2.2.2
Potential Environmental Benefits of the Project
2.2.2.1
There are some key
environmental benefits associated with the implementation of the KTE
project. The KTE has been desired by the
local residents and businesses for a long time to provide a railway service to
the Ho Man Tin and Whampoa areas and to relieve road traffic congestion in the
existing east-west corridors in
2.2.2.2 The implementation of a mass transit system, in this case an underground extension to the existing railway system and its introduction into the two major population and employment areas of Ho Man Tin and Whampoa will offer a safe, reliable, faster and more convenient mode of transport than the existing road-based vehicular system.
2.2.2.3 It is considered that during the operation phase, as trains to be operated on the project will be electrically powered, there would be minimal dust emissions. Tunnel ventilation exhausts and emergency smoke extraction facilities would be carefully positioned to avoid adverse air quality impacts. Air quality impacts during the operational phase are, therefore, envisaged to be insignificant.
2.2.2.4 The electric-powered railway is environmentally preferred to the existing vehicular based system particularly in regard to long term air and noise pollution emissions and the energy efficiency associated with mass transit as a mode of transport.
2.2.2.5 In addition to environmental benefits, the installation of an underground transport system rather than a new surface-based transport system will avoid a number of environmental dis-benefits. These include avoiding the sterilisation of land corridors which are associated with new roads or railways constructed at grade or as elevated developments. Only a very small amount of land is occupied by the above ground structures for the proposed KTE (such as station entrances, ventilation buildings, air intakes etc) and the associated noise and landscape & visual impacts of the operational stage are significantly less.
2.3
Alignment Options and Selection Factors
2.3.1
Background
2.3.1.1 The proposed KTE alignment has a number of pre-determined items which cannot be changed and therefore determine the basic alignment. These include the starting point for the rail extension, which is required to connect with the KTL at the existing twin overrun / refuge siding tunnels to the south of YMT Station and this requirement fixes both the vertical and horizontal design at these locations. This, along with fundamental system and railway design criteria which have been adopted, such as minimum horizontal curves, design speed requirements (80kph has been adopted for the whole route) and vertical change limits, resulted in consideration of three main alignment options for which the required design speed can be achieved. These alignment options are:
·
The Base
Scheme: developed in the previous Feasibility Study[1].
This was the originally proposed KTE alignment as shown in the EIA Study Brief;
·
Option A: the YMT Station to HOM Station
to
·
Option B: the YMT Station to HOM Station
to
2.3.1.2 The three alignments are shown in Figure 2.1 and are described in the sections below.
2.3.1.3 No practicable alternative options of station entrance locations were available as these were broadly dictated by each station location and operational requirements. For example, given that the HOM Station is to be an interchange station with the SCL, the station location is effectively fixed to a point at or near to where the KTE and SCL rail lines cross. Other factors were then considered including predicted patronage levels, comments at the public consultation events and availability of suitable locations.
2.3.2
Base Scheme
2.3.2.1
The westerly section of the
Base Scheme comprises the existing twin overrun tunnels beyond YMT Station
which have been constructed to a point in plan almost coinciding with the
street level portal of the World War II Air Raid Precaution Tunnel in
2.3.2.2 For the Base Scheme, the HOM Station is located at the fill platform formed by backfilling of a natural valley and then occupied by the Hong Kong Housing Authority’s Valley Road Estate and is bounded by Fat Kwong Street, Chung Hau Street and Yan Fung Street, as shown in Figure 2.2.
2.3.2.3
This HOM Station comprised four
entrances / exits strategically located at
2.3.2.4
The
easterly section of the Base Scheme to HOM Station comprises an alignment which
passes under
2.3.2.5
WHA
Station is located under Tak On Street and
2.3.2.6 This WHA Station comprised four entrances / exits strategically located at Hung Hom Road close to the junction with Man Tai Street and serving areas to the north of the station, at Hung Hom Road close to Whampoa Mansions and Juniper Mansions, in Tak On Street close to Tak Ting Street and the Whampoa Plaza and bus terminus and in Tak On Street close to the Whampoa commercial complex and serving areas to the south of the station.
2.3.2.7
The
small modifications to the previous Base Scheme, such as modifications to
horizontal curves have enabled the required design speed to be achieved for
this option and existing headways of 128 seconds for peak periods to be
achieved. A crossover some 200m east of HOM Station platform is intended.
2.3.3
Option A
2.3.3.1
Option
A comprises an alignment from YMT Station to HOM Station to
2.3.3.2
The
HOM Station associated with Option A partially overlaps
with the HOM Station for the Base Scheme option but is moved slightly
southwards and extends further to the southwest, as shown in Figure 2.3. The proposed site is
currently used as an open-air car, coach and lorry park on a short term
tenancy. This HOM Station layout would comprise four entrances / exits which
are strategically distributed as follows:
·
Two entrances at
·
An entrance utilising a
potential construction shaft near the junction of
·
An entrance at
2.3.3.3 The easterly section of this option runs south-eastwards from the HOM Station before turning eastwards with a WHA Station under Dyer Avenue between Hung Hom Estate and Tai Wan Road East and in the vicinity of Hung Hom Road and Hutchison Park. The higher ground levels in the area would result in a relatively deep station. Due to the narrow width of the road a stacked platform would be required and a full overrun tunnel is not possible.
2.3.3.4 This WHA Station comprised four entrances strategically located with two entrances at Dyer Avenue the first near Wan Hoi Street and serving areas to the south west of the station and the second near Tai Wan Road and serving areas to the south east of the station and with two entrances at Hung Hom Road the first close to Man Tai Street and the Whampoa Estate and the second close to Tak Hong Street.
2.3.3.5
This location could potentially
utilise
2.3.4
Option B
2.3.4.1
The
western section of this option is the same as for Option A, running initially
south and then slightly north of the Base Scheme. It passes under the King’s
Park playing fields and then crosses the East Rail Line at a point very close
to the Base Scheme before turning more sharply to the south and entering a HOM
Station moved to the south.
2.3.4.2
The
HOM Station associated with Option B (is the same as for Option A) and partially overlaps with the HOM Station for the Base Scheme option
but is moved slightly southwards and extends further to the southwest, as shown
in Figure 2.4. The proposed site is
currently used as an open-air car, coach and lorry park on a short term
tenancy. This HOM Station layout would comprise entrances / exits (as per
Option A) which were strategically distributed as follows:
·
Two
entrance at
·
An Entrance utilising a
potential construction shaft near the junction of
·
An Entrance at
2.3.4.3
The easterly section from HOM
Station passes down
2.3.4.4
The
headways can be maintained and design speed achieved. A crossover can be
achieved only 100m east of HOM Station. A full 110m overrun tunnel at WHA
Station is possible.
2.3.4.5
A
summary of the key alignment elements of the Base Scheme and the two
alternative options is presented in Table
2.1 below.
Table 2.1 : Summary of Alternative Scheme Elements
|
Option |
Western Alignment
Section (to
HOM Station) |
Eastern Alignment
Section (To WHA Station) |
HOM
Station |
WHA
Station |
|||||
|
Follows
|
North
of |
Under
Fat Kwong Street Playground, meets Tak On Street at
Dock Street |
|
|
Northern
Extension Option |
Southern
Extension Option |
Under
Tak On Street |
Under
|
|
|
Base Scheme |
Ö |
|
Ö |
|
|
Ö |
|
Ö |
|
|
Option A |
|
Ö |
|
|
Ö |
|
Ö |
|
Ö |
|
Option B |
|
Ö |
|
Ö |
|
|
Ö |
Ö (with extended overrun / refuge
siding tunnel) |
|
2.3.5
Land Lots Affected
2.3.5.1
All
three of the alignment options would affect both government and private owned
land to some degree. The alignments between YMT Station overrun tunnels and HOM
Station are relatively similar in terms of land lots affected, however the
alignments from HOM Station to WHA Station (and its overrun tunnels) have
significant differences, with the Base Scheme passing under many more private
land lots than Options A or Option B. This is significant in that tunnelling
under existing lots could affect or limit the future development potential of
the lots / properties and significantly affect the owners / developers of the
lots. It could also involve potential ground-borne noise impacts.
2.3.6
Alignment Lengths and Journey Times
2.3.6.1
The
overall alignment lengths (averaged for the twin tubes) between the interface
at the YMT overrun tunnels and the face of WHA Station are approximately 2.26km
in length for the Base Scheme and approximately 2.10km in length for Options A
and B in each direction. Therefore, the
tunnel lengths for Options A and B are both a total of some 300m shorter than
the Base Scheme tunnels.
2.3.6.2
The
approximate journey times for the options are very similar, with the Base
Scheme being only approximately 5 seconds longer (at 120 seconds) for the YMT
Station to HOM Station section than the other options, which have the same (115
seconds) journey times. The approximate journey time for the HOM Station to WHA
Station section is the same for all of the options at approximately 80 seconds,
making a total journey time from YMT Station to WHA Station of 200 seconds for
the Base Scheme and 195 seconds for both Options A and B.
2.3.6.3
The
shorter tunnel lengths (of Options A and B) would have environmental benefits
as follows:
· During the construction stage – less materials and resources usage including less construction activities, less excavated spoil removal and disposal, less use of construction chemicals, tunnel linings, less base plate and rails, and less E&M equipment, such as lights, ventilation ducting and electric cables etc.; and
· During the operation stage – less energy usage to power the trains and for the extra lighting and ventilation.
2.3.7
Construction Programme
2.3.7.1
The overall (tentative)
programmes for the three options are the Base Scheme - 53 months, Option A - 53
months and Option B - 50 months.
2.3.7.2
Many of the construction
requirements and durations for major construction elements of the project are
the same for these options. However:
·
For the Base Scheme a key element is that the
construction of the more northerly HOM Station is longer than the southerly HOM
Station featured in the other two options; and
·
For Option A the WHA Station at
2.3.7.3
The longer construction
duration of these major construction elements causes delays in the Base Scheme
and in Option A. Therefore, as a consequence Option B is the optimum
combination of major construction elements in terms of the construction
programme.
2.3.7.4
The overall programme for the
Option B alignment with the WHA Station located on Tak On Street is 50 months.
Critical items are construction of HOM and WHA Stations which will take
approximately 42 months. The overall programme includes allowance for testing
and commissioning.
2.3.7.5
The
shorter construction programme for Option B (3 months less) has associated
environmental benefits such as reduced duration of disturbance to the nearby
sensitive receivers and earlier removal of the associated work areas with
identified air quality, noise and landscape and visual impacts. In addition the
shorter construction period would enable earlier commencement of rail
operations with the associated benefits of mass transit as identified in
Section 2.2.
2.3.7.6 Proposed construction commencement and completion dates for major elements of the Project have been tentatively scheduled and are discussed in Section 3. A preliminary construction programme is presented in Appendix 3.1.
2.3.8
Public Consultation
2.3.8.1 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.
2.3.8.2 As one of the KTE Project Objective, an extensive series of meetings/consultations with public has been conducted during the preliminary design 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.
2.3.8.3
The Chief Executive in Council
instructed the MTR Corporation to proceed with the further planning and
preliminary design of the KTE on 11 Mar 2008.
Following the announcement of this decision, the KTE scheme was
introduced to the Subcommittee on Matters Relating to Railways of the
Legislative Council in March 2008, as well as the Shatin, Wong Tai Sin,
2.3.8.4 The MTR Corporation commenced the preliminary planning and design study of KTE in June 2008. Since then, the Government and the MTR Corporation have conducted two rounds of extensive public consultation in collaboration with the Kowloon City District Council (KCDC) in 2008 and 2009 to seek public views on the Project. Details of the public consultation are given below.
First Round Public
Consultation
2.3.8.5
An initial proposal with two
alignment options, with the WHA Station located at
·
A presentation to KCDC in June 2008;
·
Four roving exhibitions and three public forums were
held in collaboration with the KCDC in a community centre, school and shopping
mall to collect views and suggestions from the community; and
·
A meeting with stakeholders was held to collect
views and suggestions from the community.
Second Round Public
Consultation
2.3.8.6 Having considered various criteria for the evaluation of alignment options during the preliminary design study, the MTR Corporation put forward the revised scheme of KTE, with the WHA Station located at Tak On Street, for the second round public consultation. This was conducted during the period from July to January 2010, with the following items being undertaken:
·
Presentations to the
·
Presentation to the Subcommittee on Matters Relating
to Railways of the Legislative Council;
·
Three roving exhibitions and two public forums were
held in collaboration with KCDC in a community centre and school to collect
views and suggestions from the community; and
·
Thirty-two meetings with various stakeholders
including residents, schools, owners committee etc., were held to explain the
scheme and collect views and suggestions from the community.
2.3.8.7
Please refer to Appendix 2.1 for the summary of the key
public concerns on the Project. The feedback from the public consultation
indicates that the public generally support the project and look forward to its
implementation as early as possible.
2.3.8.8 In response to comments received, some modifications have been made on the design of the Project to address their concerns, as highlighted below:
Vent Shafts
2.3.8.9 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.
2.3.8.10 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;
·
Louvers of vent shafts would be located away from
sensitive receivers as far as practicable;
·
Vent shafts would be appropriately designed to blend
in to the existing urban context; and
·
Planting would be encouraged to soften the visual
impact of the vent shafts where possible.
2.3.8.11 Potential ventilation shaft noise impacts are assessed in Section 7 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.
2.3.8.12 KTE is an electric railway, and so there would not be any emissions from fossil fuel generated within the rail system. The main 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.
2.3.8.13 There are only a very few sources of dust inside the railway system. MTR Corporation has commissioned a monitoring programme on the dust level at a vent shaft in Central District and benchmarked the results with a nearby Environmental Protection Department 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.
2.3.8.14 The vent shaft is also designed to be sited at more than 5m from any opening at the adjacent building, in accordance with the Fire Services Department’s requirement. At this distance, there should be no noticeable temperature effect as a result of emissions from vent shafts. The vent shafts would therefore not be expected to lead to adverse air quality impacts to the ASRs.
2.4
Preferred Alignment Option
2.4.1
Selection Details
2.4.1.1
The
construction method(s) proposed for all three possible alignments would be the
same and therefore this did not affect the option selection. However, the
preferred construction method for the tunnels, stations and other facilities
are discussed in Section 2.5 below.
2.4.1.2
As
discussed above, all of the alignment options have the same starting point at
YMT Station (overrun tunnels) with fixed horizontal and vertical locations at
this point. Consequently, the alignment options are broadly the same in their
western sections down to HOM Station (with the exception of proximity to
sensitive receivers near King’s Park and Oi Man Estate) and greater differences
occur in the running tunnels as they extend eastwards from HOM Station and in
the location of WHA Station.
2.4.1.3
The
·
They pass under significantly less
private lots from HOM Station eastwards than the Base Scheme. This is important
as it would reduce any future loss of redevelopment potential of the affected
building lots and would avoid potential ground-borne noise impacts;
·
Tunnelling
beneath Wuhu Street will provide construction contractors with greater
flexibility to deal with ground improvement if soft ground is encountered,
whereas the Base Scheme passes under buildings and will present greater
construction risk to the project;
·
The
crossover can be located much closer to HOM Station than for the Base Scheme
and is, hence, operationally superior; and
·
They
have shorter route lengths and will, therefore, use less energy (electricity),
involve less materials usage and generate less excavation materials.
2.4.1.4
In
terms of the stations, the HOM Station options consist of a northern option and
southern option. The two options are quite similar and they partly overlap but
the southern option extends further to the southwest
and ensures that the KTE station box will be in rock. The Base Scheme
features the northern station option. A wide range of factors were taken into
account in the comparative assessment of the two options, including the site,
topography, geology, alignments, passenger comfort and convenience, presence of
other constraints (such as major utilities) and, also, the locations and practicality
of supporting aspects and facilities, such as station entrances and ventilation
shafts. As the station locations are quite close to each other many of these
factors are effectively the same for each option.
2.4.1.5
For the alignment Options A and
B the SCL and KTE lines cross to the south of the development rather than in
the platform centre. An advantage of this is that they cross well under the
assumed rock head level and would therefore be less likely to create any
ground-borne noise impacts. Both lines would be housed in station boxes with
the concourses at the same level thus providing a common concourse / transfer
level.
2.4.1.6
For the WHA Station, the
·
It would generate more patronage;
·
The station would be shallower (11m deep) and,
therefore, would be more passenger friendly;
·
The construction would be simpler;
·
It would provide opportunities for integrated
entrances linking the existing retail basement retail facilities;
·
It is projected to be more accessible to more people
due to its location and will be more convenient for passengers as it is
directly below the main shopping street; and
·
Less influence to the landlords above.
2.4.1.7
In
addition, the options have been considered for a range of environmental issues
to identify potential benefits and dis-benefits associated with each option and
the Base Scheme has more potential impacts than either of the
2.4.1.8
The
three alignment options could broadly be considered to occupy a similar land
corridor and have much in common. This is not surprising given that they all
start at the same location (YMT overrun tunnels) and are designed to serve the
same population areas i.e. Ho Man Tin and Whampoa. Consequently they have
similar potential impacts for several aspects.
2.4.1.9
From
the comparative environmental assessment shown in Table 2.2 it can be seen that the Base Scheme has less of the
identified environmental benefits for the selected criteria (with 4
‘environmentally preferred’ symbols (√)
and more of the environmental dis-benefits (with 10 of the ‘environmentally not
preferred’ symbols (X) than Options
A (with 7 (√) and 7 (X) and B (with 9 (√) and 5(X).
Table 2.2: Potential Environmental
Benefits/Dis-benefits of Alignment Options
|
Criteria |
Alignment
Option |
||
|
Base
Scheme |
Option
A |
Option
B |
|
|
Air-borne Noise |
EAP is
further away from NSRs at King’s Park (e.g. |
EAP
is closer to NSRs at King’s Park (e.g. |
EAP
is closer to NSRs at King’s Park (e.g. |
|
|
Much closer to NSRs at Ho
Man Tin (e.g. Oi Man Estate, |
Further
away from NSRs at Ho Man Tin (e.g. Oi Man Estate, |
Further
away from NSRs at Ho Man Tin (e.g. Oi Man Estate, |
|
|
More
potential NSRs at Tak On Street (X) |
Less potential NSRs at |
More
potential NSRs at Tak On Street (X) |
|
Ground-borne Noise |
Runs directly beneath
residential NSRs at junction of |
Runs directly beneath
residential NSRs at junction of |
Runs under |
|
Air Quality (Construction Dust) |
Much closer to existing
residential development at |
Further away from existing
residential development at |
Further away from existing
residential development at |
|
|
Close to residential ASRs at
Tak On Street (X) |
Further away from
residential ASRs at Tak On Street and less potential ASRs at |
Close to residential ASRs at
Tak On Street (X) |
|
|
WHA Station would be
shallower (11m deep) and require less excavation, generating less dust (√) |
WHA Station under |
WHA Station would be
shallower (11m deep) and require less excavation, generating less dust (√) |
|
Waste Management |
Longer route length (approx.
2.76km) so more spoil generated (X) WHA Station would be
shallower (11m deep) and require less excavation, generating less spoil (√) |
Shorter route length (approx.
2.60km) so less spoil generated (√) WHA Station under |
Shorter route length
(approx. 2.60km) so less spoil generated (√) WHA Station would be
shallower (11m deep) and require less excavation, generating less spoil (√) |
|
Wastewater |
Longer route length
(approx.2.76km) so more tunnel wastewater generated (X) |
Shorter route length
(approx.2.60km) so less tunnel wastewater generated (√) |
Shorter route length (approx.
2.60km) so less tunnel wastewater generated (√) |
|
Land
Contamination |
Potential interface with
contaminated land at old dockyards near to WHA Station (--) |
Potential interface with
contamination at old oil depot near to WHA Station (--) |
Potential interface with
contaminated land at old dockyards near to WHA Station (--) |
|
Cultural
Heritage |
There are no
Declared Monuments within the Project Boundary There are no designated
archaeological sites within the project boundary |
There are no Declared
Monuments within the Project Boundary There are no
designated archaeological sites within the project boundary |
There are no
Declared Monuments within the Project Boundary There are no
designated archaeological sites within the project boundary |
|
Landscape
and Visual |
Minimised landscape and
visual impacts at Ho Man Tin (√) Potential impacts to trees
at Impacts to large trees at |
Landscape and Visual impacts
at Potential impacts at Potential impact to trees on
|
Landscape and Visual impacts
at Potential impacts at Impacts to large trees at |
|
Tunnel
Length |
Greater tunnel length
(2.76km) requires greater materials, resources and energy usage (X) |
Shorter tunnel length (2.60km)
requires less materials, resources and energy usage (√) |
Shorter tunnel length
(2.60km) requires less materials, resources and energy usage (√) |
|
Construction
Duration |
Longer construction programme
(53 months) involves longer duration of disturbance, longer presence of works
areas with associated air quality, noise and landscape & visual impacts
and later commencement of operations (with the anticipated environmental
benefits of the KTE identified in Section 2.2) (X) |
Longer construction
programme (53 months) involves longer duration of disturbance, longer
presence of works areas with associated air quality, noise and landscape
& visual impacts and later commencement of operations (with the associated
environmental benefits of the KTE ) (X) |
Shorter construction
programme (50 months) hence shorter duration of disturbance, shorter presence
of works areas with associated environmental impacts and earlier commencement
of operations (with the anticipated environmental benefits of the KTE
identified in Section 2.2) (√) |
Note: (√) = Environmentally Preferred
Option
(X) = Environmentally Not
Preferred Option
(--) = No Environmental
Preference
2.4.1.10
It should be noted that many of
the benefits / dis-benefits would be associated with the construction stage of
the project and would therefore be of a temporary nature.
2.4.1.11
In
terms of the tunnel alignment itself, the
2.4.1.12
In
terms of the stations, the HOM Station options which extend further south
(Options A and B) were required / operationally determined by the need to link
with the preferred alignment (see above). This consideration overrode other
factors. The WHA Station at Tak On
Street for the Base Scheme and Option B, however, did have operational,
engineering, programme and some environmental benefits over the Dyer Avenue WHA
Station of Option A. Thus, Option B
incorporates the preferred elements, i.e. the Tak On Street WHA Station and the
shorter tunnel alignment as well as the operationally preferred crossover
located closer to HOM Station.
2.4.2
Summary
2.4.2.1
The
Base Scheme incorporates the preferred Tak On Street Alignment for WHA Station
but also includes less favourable design elements, namely the longer tunnel
alignment with a crossover further away from the HOM Station, the joint longest
construction programme and affects the greatest number of private land lots.
2.4.2.2
Option
A incorporates the shorter tunnel alignment and the closer crossover location
(to HOM Station) but also incorporates the ‘not preferred’ Dyer Avenue
Alignment for WHA Station and the joint longest construction programme. The Option
A alignment was also considered slightly less favourable than Option B in terms
of its effects on private land lots.
2.4.2.3
Option
B has the following operational advantages / environmental benefits:
·
Comprises the
·
Has the shorter tunnel alignment (than the Base
Scheme);
·
Has a closer crossover location (to HOM Station)
than the Base Scheme;
·
Has the shortest construction programme;
·
Affects the least number of private land lots;
·
Is further away than the Base Scheme from NSRs at
HOM;
·
Is further away from residential NSRs at
·
There are no ground-borne NSRs directly above the
alignment;
·
Its WHA Station is shallower than the Option A WHA
Station with reduced excavation and potential dust impacts; and
·
Would generate less wastewater than the other
options.
2.4.2.4
The
comparison of benefits and dis-benefits is shown in Table 2.2 above and Option B has been determined to have minimised
environmental effects and provides overall environmental benefits over the
other two options and presents the optimum scheme from an operational and
environmental perspective. As such, Option
B was selected as the preferred alignment.
2.4.3
EAP / VB Location
2.4.3.1
The
Fire Strategy Study for the KTE determined that an Emergency Access Point (EAP)
will be required in the tunnels between YMT Station and HOM Station. A key
reason for this is the distance between the two stations (1,750m between
centrelines of YMT and HOM Stations) is greater than the normal urban line
spacing of 1,000m. In addition the ventilation building needs to be able to
accommodate future ventilation facilities to enable possible future reduction
in KTL headways from the existing 128 seconds to 105 seconds. It is therefore
intended to combine the EAP with a ventilation shaft and also utilise it for
construction access purposes which would help to minimise the number of above
ground structures required.
2.4.3.2
The
possible locations for the EAP / VB are limited as it needs to be in close
proximity to the horizontal alignment to minimise the distance involved for
passenger evacuation and emergency services access in the event of an emergency
and to minimise the ventilation shaft length to save materials usage and energy
required to achieve the ventilation. The EAP / VB also needs to be close to the
mid-point between YMT and HOM Stations to fulfil its purpose.
2.4.3.3
The
above considerations combined with the built up nature of the area has limited
the possible locations for the EAP / VB and a total of 3 locations were
identified. These are shown on Figure
2.9 and are:
·
Option 1 - The Club de Recreio tennis courts
immediately south of the
·
Option 2 - The rugby practice pitch on the lower
platform of King’s Park Sports Ground (to the east and south are the remaining
rugby facilities managed by the Hong Kong Rugby Union, which consist of a club
house, an all-weather artificial turf pitch, a natural turf pitch and a newly
constructed training pitch); and
·
Option 3 - The northern end of the international
rugby pitch on the upper platform of King’s Park Sports Ground (the site is
located at the northern end of the international rugby pitch and immediately
south of the Parc Palais private residential development).
2.4.3.4
An
option evaluation was undertaken for the 3 EAP / VB location options
identifying the pros and cons as well as the environmental benefits and
dis-benefits and this is summarised in Table
2.3 and discussed below.
Table 2.3: EAP
/ VB Location Option Evaluation including Potential Environmental
Benefits/Dis-benefits
|
Alignment Option |
||
|
Option |
Pros / Benefits |
Cons / Dis-benefits |
|
Option 1 |
· Relatively
shallow depth of facility shaft (45m) compared with Options 2 and 3, with
shorter access time for emergency services / passenger evacuation, less use
of resources, materials usage and less excavated spoil removal and disposal · Direct
EVA from · No
upgrading of existing access road required · Target
future headway of 105 seconds can be achieved · The
quantity of excavated spoil (3,740 m3) requiring disposal is less
than the other two options · The
separation distance from the nearest residential areas (Parc Palais) and the
King’s Park sports grounds is greater |
· The
land is privately owned and used as club tennis courts and resumption would
be required. However, the lease for the site expires at end of 2011 · Closer
to the · Visual
impacts to surrounding VSRs |
|
Option 2 |
None |
· The
required land intrudes into a proposed school site which is under development · Deeper
depth of shaft (60m) increases time of emergency services access / passenger
evacuation, greater use of resources, materials usage and quantity of
excavated spoil removal and disposal · Long
EVA via bends and gradients from · Upgrading
of access road works required · Target
future headway of 105 seconds cannot be achieved · The
quantity of excavated spoil (5,950 m3) requiring disposal is greater than
Option 1 · The
separation distance to nearest residential area (Parc Palais) and the King’s
Park sports grounds is less · Visual
impacts to surrounding VSRs |
|
Option 3 |
· The
land is owned by the Government and should be easier to procure |
· The
required land will impact on a clubhouse and an international sports pitch · Deepest
depth of shaft (65m) increases time of emergency services access / passenger
evacuation, greater use of resources, materials usage and quantity of
excavated spoil removal and disposal · Longest
EVA via bends and gradients from · Significant
upgrading of access road and embankment works required · Target
future headway of 105 seconds cannot be achieved · The
quantity of excavated spoil (5,695 m3) requiring disposal is greater than
Options 1 and 2 · The
separation distance to nearest residential area (Parc Palais) and the King’s
Park sports grounds is less · Visual
impacts to surrounding VSRs |
2.4.3.5
The
Option 1 location involves a shorter shaft than Options 2 and 3 which had a
number of environmental benefits including less materials and resource usage,
less excavated spoil to dispose of and less energy use during construction. It
is closer to the Queen Elizabeth Hospital facilities, but is further away from
the Parc Palais residential areas and King’s Park sports ground. It also
provided better existing Emergency Vehicular Access (EVA) and sufficient nearby
emergency parking for fire engines without the need for access road improvement
construction works and associated environmental impacts. The shorter shaft
would also use less energy to achieve the ventilation requirements during
operation. All 3 options would present some visual impacts although these could
be mitigated by tree screening and greening of the building structure.
2.4.3.6
The
Option 1 was determined to be preferred operationally and from a safety aspects
viewpoint by providing quicker / shorter access for emergency services and
passenger evacuation. An additional factor is that MTR Corporation wish to have
the flexibility to reduce the KTL headway in the future and this cannot be
provided by Options 2 or 3. This is explained below under the heading One-Train
Rule below.
One-Train
Rule
2.4.3.7
The
purpose of the one-train rule is to limit or allow only 1 train to be present
in any one ventilation zone to ensure effective and safe passenger evacuation
when operating smoke extraction in the push-pull principle. A longer ventilation zone would mean a longer
travelling time for a train to clear that particular tunnel section, which
implies a longer headway level (a lower service level).
2.4.3.8
The
105 headway requirement for KTE would be required to be in line with the
ultimate system headway of the existing KTL and should not introduce a new
headway bottleneck in the new extension of KTL.
The existing operational headway of KTL is 128 seconds.
2.4.3.9
The
achievable operation headways of the 3 possible ventilation building locations
are summarised in Table 2.4. It is necessary to locate a ventilation
building in between the YMT Station and HOM Station tunnel section to ensure 2
ventilation zones are available in that tunnel section.
Table
2.4: Achievable Headways For
|
Location |
Option |
||
|
|
Option
1 |
Option
2 |
Option
3 |
|
Achieved Operational Headway |
104
sec |
112
sec |
119
sec |
|
Satisfied 105 sec
headway |
ü |
û |
û |
2.4.3.10
The
Option 1 for the EAP / VB was therefore selected as the preferred operational
and environmental option.
2.5.1.1
Since the selection of the preferred
alignment option (Option B - the
2.5.1.2 Details of the Revised Preferred Scheme incorporating the Design Evolution items are provided in Section 3 of this EIA Report.
2.5.1.3 It should also be noted that the Technical Circular (ETWB TCW No. 13/2003) guides the parallel actions on the Gazetting and EIA approval process for the project. In handling any EIA related inconsistencies that may arise due to the gazette documents amendments, MTRCL would follow the guidelines and requirements of Section 13 and Section 10 of the EIAO in the EIA processing. On the other hand, in the separate gazettal processing, MTRCL would follow the requirements as stipulated in Railways Ordinance Cap. 519 to manage any amendments to the gazetted scheme. In addition, if any amendment items which would have any potential environmental impacts, attention will be drawn to the concerned stakeholders through continuous communication with the District Council and local community. Some inconsistencies between the EIA Report and the gazette have occurred and these are listed, together with the implications for further environmental impacts, in Appendix 2.3.
2.6
Construction Methodology
Alternatives
2.6.1
Tunnel Options
2.6.1.1 The whole of the KTE railway alignment is in tunnel and as such the method of forming the tunnel during the construction phase is a key factor for the EIA Study. Notwithstanding, the engineering feasibility of the various alternative options play a key factor in the selection of the preferred options. The main tunnelling methods considered for this project are:
·
Drill-and-blast construction;
·
Mechanised tunnel boring, in which the tunnel is
bored using a tunnel boring machine (TBM);
·
Cut-and-cover excavation technique; and
·
Soft ground tunnelling methods.
Drill-and-Blast
Construction
2.6.1.1
This is the conventional method
of excavation for large face area hard rock tunnels in
2.6.1.2
The use of explosive blasting
for the bulk excavation of hard rock is well proven and tends to be the most
efficient method available / used in
2.6.1.3 For most tunneling projects in rock, the ground condition is somewhere between two extreme conditions of hard rock and soft ground. The tunnel face may have a certain self-supporting stability, however support measures are still necessary. For this project the drill and blast excavation method may be a cost effective solution.
2.6.1.4 Drill and blast techniques are considered to be feasible for most rock tunnel sections of this project and it is particularly suited to the variations in shape and geometry of the tunnels, station boxes and varied excavations required for the KTE project.
Mechanised
Tunnel Boring using a TBM
2.6.1.5 A TBM is a large drill that excavates a circular tunnel without disturbing the ground surface other than at launching and retrieval shafts and therefore minimizes surface disruption. TBMs are custom designed for specific geological conditions (and to meet other project requirements). As the TBM moves forward creating the tunnel, the excavated rock and soil are conveyed backwards for disposal and segmental linings are placed to progressively form the tunnel. TBMs are electric powered and supplied from a temporary electricity sub-station located near the launching shaft.
2.6.1.6 A TBM is particularly suitable for soft and mixed ground tunnels. It can be utilized for short lengths of rock tunnel but tends to be less efficient or flexible for these sections as traditional methods, such as drill and blast.
2.6.1.7 After completion of the required tunnel a TBM is sometimes driven forward to a retrieval shaft where it is disassembled and removed, or possibly left in a resting location, then ‘stripped down’ to remove the useful parts of the machine and left in place.
Cut-and-Cover
Construction
2.6.1.8
The cut-and-cover method of
tunnelling / excavation involves excavating a trench, constructing a tunnel (or
placing a preformed structure) within it and then covering the structure with soil.
To reduce the duration of the disruption and to restore pedestrian and
vehicular traffic as soon as possible the trench is often covered by a
temporary decking arrangement following the excavation. It is proven and
commonly used method of excavation and construction in
2.6.1.9 Cut-and-cover construction accommodates variations in the width of the tunnel and also non-uniform shapes, which are required to build stations and portals. Diaphragm walls, which are often used to support the vertical sides of the excavation, may serve as temporary or permanent support for the excavation / tunnel.
Soft
Ground Tunneling
2.6.1.10 Soft ground tunnelling is normally undertaken as excavation by longitudinal sections in stages. It is common practice with this method to strengthen and prepare the soil for tunneling, by ground modification. This can include various types of grouting (by injection of chemical or cementing agent into the soil), ground freezing and other similar treatments.
2.6.1.11 Excavation for the soft ground tunnels is envisaged to be by mechanical excavation method. Supporting structures are required for the excavation area to ensure soil stability and in order to avoid excessive ground movement.
2.6.1.12 For this project steel canopy tube umbrellas with grout curtains on the perimeter would be installed prior to tunnel excavation. Temporary lining in the form of steel ribs and fibre reinforced shotcrete would be fixed against the excavated soil or treated soil surface for stabilisation. Advance probing would be proceeded to investigate any possible zones of significant water inflow. Grouting would be carried out ahead of the excavation face to minimise overall inflow of ground water to facilitate the excavation work. This can be carried out from the ground surface prior to excavation or from the tunnel level. Additionally, advance drill holes can be adopted to release excessive pore water pressure in soil to avoid sudden collapse of the cut soil face during excavation although this is not preferred if excessive groundwater flows are experienced. A waterproofing membrane and permanent in-situ concrete lining would be constructed against the shotcrete surface with a smoothing concrete layer where required.
2.6.1.13 While this method is slow, it can be particularly effective in certain situations, such as around a subway or utility which cannot be relocated and where special care is required to protect the obstruction. The method allows a tunnel of any shape to be excavated and it is therefore applicable for areas, such as crossovers and bifurcation, in which the tunnel shape or size needs to vary.
2.6.1.14 As the name of the method indicates this method is only intended for soft ground areas and would not be applicable for much of the tunnel route. Soft ground is anticipated in several areas and a combined rough estimate of about 170m of tunnel is anticipated. Therefore the soft ground tunnelling would be undertaken in conjunction with other tunnel construction method(s).
Considerations
for Selection of Preferred Tunnel Construction Method
2.6.1.15 The preferred construction method would be predominantly determined by engineering factors including safety, geological conditions, site conditions / constraints, accessibility, programme and cost effectiveness. Environmental considerations have also been taken into account to minimize the potential noise, air quality, water quality and cultural heritage impacts as well as waste management aspects.
Geography, Geology
and Site Conditions
2.6.1.16
At the western end of the
route, where the proposed alignment connects with the YMT Station overrun
tunnels and runs parallel with the existing Gascoigne Road, the ground level is
approximately +6mPD to +8mPD. As the alignment passes underneath various sports
grounds and across Wylie Road the existing ground level varies from +15mPD to
+35mPD. The alignment then continues under
2.6.1.17 The proposed alignment lies almost entirely within the Kowloon Granite as shown in Figure 4.2. A mantle of decomposed granite overlies the bedrock to varying depths. The majority of the alignment is covered by a layer of fill that is thicker in the area of the ex-Valley Road Estate where in excess of 30m of fill is encountered. Much of the alignment will be constructed through hard rock.
2.6.1.18 The alignment will however encounter several potential faults and zones of soft ground. There are some areas of low rock cover, notably approaching WHA Station. The alignment comes close to the original shoreline at the eastern end, although no marine deposits have been noted near the proposed tunnels.
2.6.1.19 This has been taken into account in the selection of the proposed construction method for the different sections of the alignment.
Environmental
Considerations
2.6.1.20 Potential environmental issues associated with each of the tunnelling construction methods have been reviewed and a summary of their benefits and dis-benefits is presented in Table 2.5.
Table 2.5: Benefits and Dis-benefits of Tunnel
Construction Methods
|
Construction Method |
Benefits |
Dis-benefits |
|
Drill and blast |
All works
underground so minimizes the disturbance to land and public activities at
ground level throughout the construction period Duration of
blasting would be short and infrequent Less spoil to be
disposed of, as compared with C&C method Above ground
works only required for portal construction Noise impact
could be minimized with the provision of temporary doors and barriers at the
portals and shafts |
Higher vibration
to adjacent sensitive receivers, but could be mitigated through blast design
and careful monitoring Blasting would be
required and would require provision of site explosives magazines for storage
of explosives Transportation
of explosives on public roads / marine waters |
|
Bored tunnelling |
All works
underground so minimizes the disturbance to land and public activities at
ground level throughout the construction period Less spoil to be
disposed of compared with C&C method Noise impact
could be minimized by provision of temporary decks over the portal Above ground
works only required for construction of launching and retrieval shafts and
portals (if different locations) Comparatively
lower vibration impact Lesser impact on
groundwater level with the installation of water tight concrete tunnel lining
in pre-cast segments |
Preferable for
24hr operation to ensure stability of ground Requires
additional land for the handling of slurry that requires processing before
disposal Potential
adverse ground-borne noise impact when excavating in rock below existing buildings The required
launching site area would need to be of a significant size to accommodate the
excavation shaft, areas for materials delivery and storage, spoil/slurry
removal operations. |
|
Cut-and-cover |
Accommodation
of different sizes of works areas |
More
construction plant will be involved such that this would generate relatively
more noise and dust impacts Sensitive
receivers will often be affected over a longer construction period Works all
commence at surface so increased disturbance to land and public activities at
ground level throughout the construction period Requires
recycling of bentonite for diaphragm wall construction Larger amount of
spoil required to be disposed of |
|
Soft ground tunnelling |
Allows a tunnel
of any shape to be excavated and is therefore applicable for areas, such as
crossovers and bifurcates where the tunnel size needs to vary. Is useful for
situations such as excavating round a subway or utilities which cannot be
moved |
Is a slow
excavation method and requires dry ground or at least soil preparation
techniques such as dewatering, grouting / injection of chemicals or cementing
agents, ground freezing etc. |
Note: C&C = Cut and
Cover
Preferred Tunnel Construction Methods
2.6.1.21 The anticipated geological conditions along the alignment are critical in the selection of the construction methods. The type of soil, rock and the presence of water have a fundamental impact on the selection.
2.6.1.22 For the long tunnels between YMT Station overrun tunnels and the approach to HOM Station excluding the station areas and short areas of soft ground the only two viable method options are TBM and drill and blast. The cut and cover method was discounted for these tunnels as this would cause severe disruption at the ground surface for the whole route alignment.
2.6.1.23 TBMs are commonly used for the excavation of long tunnels in soft and hard rock. The advantages of excavation by TBM in rock tunnelling are relatively high daily production rates as compared with drill and blast methods, a controlled excavation profile, and low vibration and noise generation. However, the TBM tunnelling would generally involve continuous operation, which often would be a main source of ground-borne construction noise impact. In addition, procurement of a TBM is expected to take about 18 months, due to limited number of suppliers, shortage of manufacturing capability and overall global demand within the buoyant tunnelling market. As such, the daily production rate of TBM will be relatively higher than that for blasting but the overall production rate will be lower for short tunnel sections.
2.6.1.24 Excavation by drill and blast method is not a continuous operation and in general has lower daily production rates than TBM tunnelling. Drill and blast operation will have less lead time required and there are programme advantages. Drill and blast tunnelling in rock is however better at managing ground risk issues but magazines and ventilation adits will be required for supporting the blasting.
2.6.1.25 It is considered that both the TBM and the drill and blast construction methods would minimise the disruption at ground level. Both would be supported by construction access shafts and mucking out points including slurry handling and disposal for the TBM. In addition the TBM would require a launch and potentially a retrieval site and these would be difficult to accommodate in the heavily built up project area. The TBM launching site would need to accommodate the excavation shaft area, areas for materials/equipment delivery and storage, spoil/slurry stockpiling and removal area etc. These would all cause air quality, noise, water quality and landscape and visual impacts and would add to the temporary traffic impacts and management issues. It is anticipated that after tunnel completion the TBM could be ‘stripped down’ and the major parts removed via the launching site leaving the shield skin in place in the tunnel and avoiding the need for a removal site.
2.6.1.26 Overall there would not be significant environmental differences between the TBM and the drill and blast methods.
2.6.1.27 With consideration of the abovementioned engineering constraints, environmental benefits and dis-benefits, and programme risks, drill and blast construction method is preferred for the long rock tunnels while soft ground tunnelling method will be adopted for mixed and soft ground tunnels. Drill and blast construction method will be adopted for the vent shafts/ EAP (although with some mechanical breaking / excavation.
2.6.1.28 The construction method for each tunnel section has therefore been selected, based on engineering and site issues / constraints. The proposed use of drill and blast tunnelling has been maximised to reduce impacts which would otherwise arise for above ground works. The majority of soft ground and mixed ground tunnel sections will be constructed by soft ground tunnelling method.
2.6.1.29 The stations will be constructed by cut and cover method. The preferred construction methods for the different tunnel sections are summarised in Table 2.6 and presented in Figures 3.8 and 3.9.
Table 2.6: Preferred Construction Methods
|
Construction Method |
Tunnel Sections |
Selection Reasons |
|
Mechanical excavation |
Interface connection
tunnels with YMT overrun tunnels
|
Geological and engineering constraints |
|
Cut-and-cover construction method |
HOM and WHA Stations and the WHA Station overrun
/refuge siding tunnel |
Engineering constraints |
|
Drill and blast construction method |
Interface connection with the mechanical excavation
at YMT overrun tunnels to HOM Station northern approach HOM Station southern approach to WHA Station
northern approach (Excluding small areas of soft ground) Total tunnel length
is 1,930m (i.e. 2,100m -170m for soft ground tunneling) EAP / ventilation shafts (with some mechanical
excavation tunneling) |
Geological and engineering constraints Minimisation of ground level disruption and
potential disturbance to the public |
|
Soft ground tunnelling construction
method |
Small areas of soft ground in tunnels and shafts
(The total combined length of soft ground tunneling is approximately
170m) |
Geological and engineering constraints |
[1] This Base Scheme is
actually slightly modified from the Base Scheme produced by the previous
Feasibility Study. However these are only minor amendments to features, such as
the horizontal curves, made to enable achievement of the required design speed.