2.                   PROJECT DESCRIPTION

Project Background

2.1               The existing Island Line (ISL) of MTRC provides mass transit railway services to major population and employment centres along the north shore of Hong Kong Island between Chai Wan and Sheung Wan.  An extension of the ISL to Western District has been planned for many years, but has not yet been implemented due to a relatively low financial viability. 

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 Hong Kong.  Further to this study, MTRC submitted a proposal for the WIL to the Government in May 2002.  In this proposal, the WIL would be an extension of the ISL, and its construction would be divided into two phases.  Phase 1 would begin at the already existing Sheung Wan Station.  A further two stations, Sai Ying Pun and University would be added to extend the length of the ISL.  Phase 2 would include an extension of the line from University to Kennedy Town, but its construction would be subject to the land availability of the western reclamation.

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 Kennedy Town, via Sai Ying Pun and University.  The WIL has been gazetted under the Railway Ordinance in October 2007.  It is expected that the construction of WIL (the Project) will commence in 2009, for completion in late 2013 / early 2014.  The construction programme for WIL is provided in Appendix 2.2.

Potential Environmental Benefits of the Project

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.

Scope of the Project

2.6               The Project comprises the following elements:

·          Approximately 3km of underground railway from Sheung Wan via Sai Ying Pun and University of Hong Kong to Kennedy Town

·          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 Mount Davis, with a minimum of 20m of rock cover, to support the construction of WIL.  An underground access tunnel to the magazine storage chambers will be constructed.  The tunnel portals of the access tunnel will be built on a flat platform next to Victoria Road. 

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 (Western PCWA) respectively.  A construction shaft would also be provided at the King George V Memorial Park.  This shaft would not be used for mucking out but for personnel and material access only.

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.

Alternatives Consideration

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.

Do-nothing Scenario

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 shore of Hong Kong Island.  The long-standing traffic congestion problems in the Western District could be solved by constructing new roads.  Nevertheless, given the topography and congested environment of the Western District, no space would be available for developing new roads except by further reclamation. 

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.

Alignment

2.1               A railway to serve Kennedy Town has been planned for more than 30 years.  In that time, more than ten planning studies have been carried out by the Government or MTRC.  The early proposals for rail to serve the west of Hong Kong Island were for the extension of the ISL to Kennedy Town on an alignment along Des Voeux Road West (Figure 2.8 – The Protected Alignment).  This proposal would require a two-level deep cut-and-cover station box within Des Voeux Road West.  However, this proposal was discarded mainly because:

·          Space available for carrying out cut-and-cover station box at the narrow Des Voeux Road West would be highly limited.

·          As tramways aligns along Des Voeux Road West, tram traffic would be adversely affected as a result of the construction works.

·          Cut-and-cover construction would be conducted immediately adjacent to residential/commercial buildings alongside Des Voeux Road West.  This could potentially jeopardize safety of workers as well as users of nearby buildings.

·          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 Des Voeux Road West was too narrow to contain two-level, island platform stations (see Section 2.16 above).  The study further concluded that bored approach tunnels under Des Voeux Road West to serve such stations could not avoid encroachment into adjacent building lines.  The study proposed that four-level, cut and cover stations, with side platforms instead of island platforms, could be built but this required approach tracks to be stacked in tunnels one above the other.  These conclusions were endorsed by the Government (Station Traffic Integration Committee) in 1982 (Figure 2.9).  They have been confirmed in all subsequent planning studies, some of which have also examined bored tunnel stations.  In every case, extensive land resumption was required for excavations to contain the concourse(s) and plant rooms at each station.  It was also noted that the need for cut and cover construction in Des Voeux Road West could not be obviated by adopting this alignment proposal.  Furthermore, the construction of the alignment from University to Kennedy Town would be subject to the land availability of the Green Island reclamation.  In view of the adverse environmental impacts that would likely be resulted from the cut and cover works at Des Voeux Road West and reclamation at Kennedy Town, this alignment proposal was not favoured.

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 Des Voeux Road  West plus the merit of minimising the risk of construction by building the stations and alignments in rock. 

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 Kennedy Town is now named) and a proposed medium capacity system (now labelled South Island Line – West) was then transferred from SYP Station to UNI Station, where it has been included for WIL planning.  In June 2005 Government gave MTRC approval to proceed with further planning and design of the WIL on this basis.  Following this, MTRC commissioned a preliminary design study in 2005 to further develop the WIL project. 

Preferred Alignment

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 Main Building of the University of Hong Kong (Declared Monument).  Key modifications that were made would include moving the UNI Station eastward so that the station and the concerned alignment sections could be constructed in rock as far as possible in order to minimise the construction risk and time required for its construction.  The KET Station was also shifted to further avoid directly impacting the significant heritage and landscape resource i.e. tree walls at Forbes Street (also refer to the discussion on alternative locations for KET Station presented below) and King George V Memorial Park.  The adoption of this preferred alignment would also eliminate the need for reclamation and associated environmental impacts.  The preferred WIL alignment is shown in Figure 1.1.

Stations

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.

KET Station

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 Forbes Street.  In connection with this, a tree protection zone has been established as illustrated in Figure 2.11 with reference to the advice sought from a tree expert Professor CY Jim.  This factor has been duly considered in the selection of preferred option (refer to Section 2.94). 

KET Station Option 1 – Cavern under Kwun Lung Lau

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.  Kennedy Town is in volcanic rock, which is expected to be much more heavily fractured than the granite at the UNI and SYP areas, and this will therefore require heavier support and much more advance grouting to control groundwater, thereby increasing risk of construction and prolonging the construction programme.  The prolonged construction period will increase the duration for which the locals will be affected by the environmental nuisance (including construction noise, fugitive dust, visual etc.) caused by the construction works. 

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 50m vertically to access the station. 

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 Forbes Street.

KET Station Option 2

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 30m deep, it is likely that vertical and/ or horizontal movements could cause some damage to the trees and/or the walls.  Certainly, it is to be expected that the effects will be magnified compared with the shallower excavation depths of KET Station Option 3 – see Section 2.36 below.

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.)

KET Station Option 3

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 10m) of the temporary retaining wall of the north side of KET Station would encroach slightly into the tree wall protection zone.  On this issue, advice from tree preservation expert Prof Jim was sought.  It was considered that minor and local encroachment would be unlikely to result in adverse impact on the wall. 

2.21            The track level is at approx. -7mPD, 5m higher than for Option 2.  Furthermore, no cut-and-cover excavation would be necessary within the basketball court area.  Therefore, the maximum depth of excavation would be reduced by about 10m compared to Option 2.  The reduction in the depth of excavation would in turn shorten the construction programme. As a result, the duration for which the nearby sensitive receivers would experience environmental nuisance caused by construction activities could be reduced. 

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.

Selection of Preferred KET Station Option

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 50m vertically to access the station.

-   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 10m compared to Option 2, less excavated spoil would be generated.

-   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.

UNI Station

2.28            The proposed station location is beneath Pok Fu Lam Road.  The site investigation data has confirmed that the proposed station location is deep in rock, and as such the station will be constructed as a rock cavern. The alignment constraints are such that there are no options for UNI station. The horizontal alignment already incorporates the minimum radius curves to link with KET and SYP Stations. The vertical alignment is controlled by how quickly the tracks can climb from SYP Station at the maximum gradient of 3%.    

SYP Station

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 First Street. There is no flexibility to move the alignment at all.

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. 

Entrances & Associated Adits

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 5.1.5-5.1.7) that most of the proposed entrance sites are situated in either “Government, Institution or Community” (GI/C) or “Open Space” (OS) zones.  Two major government facilities (David Trench Rehabilitation Centre and Centre Street Market West Block) and a toilet block at Whitty Street will be relocated to accommodate three of the entrances. 

2.33            Some entrances were added as a result of surveys of public opinion carried out by MTRC. The Ki Ling Lane entrance at Sai Ying Pun (Entrance B3) is an example of entrances added largely as a result of public demand.  From the point of view of passenger accessibility, it would also be desirable to construct the entrances in areas where populations are located nearby.  This would however result in construction phase environmental impact such as noise and dust impacts.  Although environmental factors would not play a major part in the selection of entrance locations, it was considered that the environmental impacts due to entrance construction would be temporary and could be minimised as far as practicable by the recommended mitigation measures. 

Ventilation Shafts

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. 

Ventilation Shafts for the Overrun Tunnel

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. 

 

VS Option 1

2.37            The vent shaft proposed under this option will be located at the site of Ex-Police Quarters at Ka Wai Man Road (Figure 2.15).  The site is currently occupied by CEDD for their slope reinforcement work.  The construction of the shaft would require demolition of Blocks A and C.

VS Option 2

2.38            The vent shaft proposed in this option is placed at the toe of the slope near the existing petrol station on Victoria Road (Figure 2.16).  A platform would be created at a level of +26mPD with an access road connecting back to Victoria Road to the west.  Due to the steepness of the slope, a substantial amount of earthworks (and slope protection works would) will be required for this location.  

VS Option 3

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.

Selection of Preferred Option

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.

Environmental Considerations Given in the Alignment, Station, Entrance and Vent Shafts Selection

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 Declared Monuments and Graded Historical Buildings, as well as significant heritage and landscape resources (i.e. Tree walls at Forbes Street and King George V Memorial Park, as well as Old and Valuable Trees) can be avoided.  Overall the preferred WIL alignment has been designed to preserve the significant environmental resources in the Western District.

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 Forbes Street.  In view that KET Station Option 3 has balanced both the need for preserving the wall trees at Forbes Street and minimizing construction risk and safety issues, it has been identified as the preferred option. 

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 Haking Wong Building of the University of Hong Kong (HKU) at Pokfulam Road for a vent shaft has been examined.  This site is situated adjacent to Pokfulam Road with busy traffic.  If a vent shaft is to be constructed there, part of the retaining wall and the nearby slope would have to be demolished.  During the course of the demolition works, temporary closure of the eastbound carriageway of Pokfulam Road to the HKU approach road would be necessary.  In addition, significant disturbance to HKU and the community would be anticipated as public utilities including water and gas pipelines, sewerage and cables would need to be diverted.  Therefore, this site would not be a practical option.

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 Des Voeux Road West has been dropped because such a location would involve large-scale excavation works, underground utilities diversion and temporary traffic closure / diversion, and thereby result in significant disturbance to surrounding environment and community. 

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.

Construction Methods

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.

Drill-and-Blast Construction

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.

Tunnel Boring Machine

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.

Cut-and-Cover Construction

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.

Sequential Mining Construction

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.

 

Mini and Micro-tunnelling

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. 

Selection of Preferred Construction Method Option

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 Victoria Road near Mount Davis.

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.    

Works Areas Requirements and Locations

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 Victoria Harbour as ‘principal works areas’, namely the KET Abattoir Site (Works Area B), and Western PCWA (Works Area E).  They are not the sites of future permanent WIL structures but are essential for supporting the WIL construction.  Barging points are also proposed at these two works areas.  They will be used for efficient disposal of excavated materials including demolition debris and for the delivery of major construction materials, plant and equipment. 

Works Area at KET Abattoir Site

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 Proposed Kennedy Town Comprehensive Development Area Site Project (hereinafter known as the “KTCDA Project”) was conducted by the Civil Engineering and Development Department (CEDD) (formerly Civil Engineering Department).  In the EIA study, the KTCDA Project covered the demolition and clearance of all buildings, structures and chimneys, and remediation of contaminated ground within the KTCDA site and related activities.  The nature and extent of environmental impacts, as well as potential safety and health hazards from the Project works were assessed in the EIA study.  The EIA Report for the KTCDA Project concluded that with the implementation of mitigation measures, the identified environmental impacts on representative sensitive receivers would comply with environmental standards. 

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 Kennedy Town abattoir and incinerator area, construction of temporary concrete paving, and handover the Kennedy Town abattoir and incinerator area to MTRC as a works area for WIL.  The KET Abattoir Site will be returned to CEDD after WIL construction work completion.  Remediation of the KTCDA site will be conducted in Phase 2. 

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.

Health Risk Issues

2.79            The human health risk issue associated with the contaminated soil and groundwater in Kennedy Town abattoir and incinerator area to populations located at and in the vicinity of the site was assessed in the VEP Report.  The VEP Report concluded that the human health risk at the Kennedy Town abattoir and incinerator area would be acceptable and in compliance with the established criteria with the following mitigations:

-          a paving layer (not less than 200mm thick) should be constructed, and remained intact to act as an integral physical barrier

-          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 200mm thick, assuming that the site would be used for site offices and material storage only.

2.81            To cater for the loadings from the proposed additional rock crusher use, the adequacy of the 200mm  concrete paving thickness has been reviewed.  Based on the calculations provided in Appendix 2.5, the bearing capacity and shear for a 200mm thick concrete slab should be sufficient for supporting the use of a rock crusher at the KET Abattoir Site The same construction method of the temporary paving, as well as the site offices as described in Section 1.16 -1.17 and illustrated in Appendix 1.2 of the VEP Report will be followed.  Therefore, with the implementation of the same VEP conditions, no unacceptable land contamination and human risk issues are anticipated from the proposed additional rock crushing use.

Other Environmental Issues

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. 

Implementation Schedule

2.83            An implementation schedule specifically for the works area at the KET Abattoir Site is provided in Table 14.2.

Works Areas at the Western PCWA

2.84            The Western PCWA works area (Works Area E) would provide support to the construction of two stations - UNI and SYP Stations and the tunnels between these stations.  A conveyor belt system will be provided at Works Area F to convey the excavated materials from the mucking out point at the car park at Kennedy Town Praya (Works Area G) to the barging point at the Western PCWA works area (Works Area E) across Shing Sai Road (Works Area F).  Such setting would avoid the need for major mucking out in the residential areas. 

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. 

Temporary Underground Magazine

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 Hong Kong Island.  One of the sites that was considered was Green Island.  However, this was discounted due to delivery problems in the event of bad weather.  A shortlist of two potential magazine sites was prepared:

Site Magazine Option 1

2.88            The first option was to locate the magazine underground in a tunnel off Sai Ning Street in Kennedy Town. The plan was to end the rail tunnel at Sai Ning Street and to build a magazine of the side of the rail tunnel (Figure 2.18).  However, the overrun tunnel would then need to be constructed near a petrol station at Victoria Road.  This petrol filling station has operated over several decades, and would have potential land contamination issues resulting from localised fuel leakage/spillage. The overrun tunnel was finally realigned to keep away from the petrol filling station.

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 Victoria road on the west side of Hong Kong Island (Figure 2.1). The possibility of a surface magazine or an underground magazine were considered at this location.

Selection of the Preferred Location

2.90            The preferred location for the site magazine was eventually chosen as the Victoria road site, Site Magazine Option 2. The underground magazine option was chosen as the steep topography at this site was conducive to safe handling and secure storage of explosives. The other reasons for selecting the Victoria Road site as the preferred site were:

·         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 Victoria Road near Mount Davis for the storage of explosives for blasting (Figure 2.1).  Apart from the access tunnel portals and access road, the access tunnel and explosive storage chambers will be built underground.  The temporary underground magazine will be removed after the completion of the WIL construction.

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.

Ground Treatment Works Areas at Des Voeux Road West, Wing Lok Street and New Market Street

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 Des Voeux Road West, Wing Lok Street and New Market Street (i.e. Works Areas O1-O3). 

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. 

Works Areas for WIL - Summary

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 Victoria Road near Mount Davis

Vacant

Temporary underground magazine

A

2.21

Blocks A and C, Ex-Police Quarters, Kennedy Town

Vacant

Tunnel construction access, Vent shaft for KET overrun tunnel

B

2.21

Kennedy Town Incinerator and Abattoir

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 Forbes Street, access road

Playground, football field and toilet

KET Station structure (entrances and ventilation shafts). KET Station construction site.

D

2.22

Kennedy Town Swimming Pool

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 Kennedy Town Praya

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

Hill Road Rest Garden

Garden

UNI Entrance B2. Construction site.

J1

2. 23

Hill Road

Footway

UNI ventilation shaft. Construction site.

J2

2. 23

Western Court

Substation, slope

UNI Entrance B1. Construction site.

Whitty Street Public Toilet

Public toilet

St Anthony’s School

Slope

J3

2. 23

HKU Area / Public Road Side Amenity

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 Mui Fong Street

Playground

Contractor’s site facilities.

L1

2.24

Children’s playground at Ki Ling Lane

Playground

SYP Entrance B3. Construction site.

M

2.24

King George V Memorial Park (part)

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

Des Voeux Road West

carriageway

Ground treatment

O2

2.25

Wing Lok Street

carriageway

Ground treatment

O3

2.25

New Market Street

carriageway

Ground treatment

 

 


Size of Works Areas

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. 

Public Consultation

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. 

Tree Walls

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 Smithfield.  Notwithstanding this designation, extreme measures have been taken to preserve the ‘tree walls’ in the western part of the reserved alignment, which border Forbes Street and the recreational areas adjacent to it.  This has been achieved by placing the cut and cover box containing the station as far to the east as topography permits and adopting a radical internal station design to minimise the station length.  An entrance on Smithfield serves the population north and south of the station and one on Rock Hill Street serves the population to the north-east.  A third entrance is located at a PTI for GMB and taxis on the east side of Smithfield.  Provision has been made in station design for a future entrance to serve new developments along Cadogan Street. 

Vent Shafts

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 5m from any opening at the adjacent building, in accordance with the Fire Services Department’s requirement.  According to the preliminary design of WIL, the distance between the vent shafts and openings of the adjacent building would be over 8m away, and at this distance, there should be no noticeable temperature effect as a result of emissions from vent shafts.  The vent shafts would therefore not expect to lead to adverse air quality impacts to the neighbourhood. 

Construction Programme

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