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Border line case

KCRC project study Lok Ma Chau spur

Growing pressure on Lo Wu station at the border with mainland China is making construction of KCRC's third East Rail extension project an increasingly urgent priority.

Hong Kong's return to Chinese control in 1997 resulted in a massive increase in cross border traffic. This has pushed the capacity of KCRC's Lo Wu station, at the border with the mainland, to the limit with the result that the corporation is preparing to build a spur line to a new border crossing station at Lok Ma Chau.

At Lo Wu East Rail, passengers travelling to and from Hong Kong's neighbouring Chinese city of Shenzhen must disembark to go through passport control. On a normal day, around 250,000 people cross the border here, while at weekends and during public holidays, the number climbs as high as 335,000.

At peak times, East Rail trains carrying 3,500 passengers each arrive at the Lo Wu terminus every five minutes, putting enormous pressure on the station, which is unable to expand to handle such large numbers. As queues spill out onto platforms, East Rail services face delays as trains are held back until backlogs clear. Such delays can have a knock on effect on the rest of the busy line, disrupting the whole service.

The solution is to build a spur line running 7.4km west from Sheung Shui station, to a new border station at Lok Ma Chau.

This will be capable of handling 150,000 passengers per day.

Construction of the spur was originally planned to start a year ago. But plans to put the line on viaduct across the environmentally sensitive Long Valley wetlands were thrown out by the Hong Kong government's Environmental Protection Department (EPD).

As a result, KCRC has developed plans for a 4.3km twin bore 8.75m diameter tunnel which will take the line under Long Valley before completing the link to Lok Ma Chau on a 2.1km viaduct designed by consultant Binnie Black & Veatch. The plan received conditional approval from the EPD last month, and it is hoped the project will go out to tender in May.

KCRC has drafted its West Rail tunnelling team on to the project to develop the tunnel design with consultant Arup.

The twin bore structure will run at depths between 10m and 12m through waterlogged terrain.

As a result, KCRC plans to build it with an earth pressure balance shield tunnel boring machine (TBM) similar to the one used on the West Rail's Kwai Tsing tunnels. 'The tunnel will have to traverse rock, mixed and soft ground, ' says KCRC West Rail general manager, construction Jaya Jesudason. It will also pass through waterlogged ground.

Tough environmental controls on work under Long Valley will also heavily restrict work.

'One of the prime criteria when we go across the most environmentally sensitive area is that there will be no access to the surface. We must not disturb the groundwater, pollute the soil or contaminate the groundwater, ' says Jesudason. The tunnel will also have to be completely watertight - 'we'll be looking for zero water ingress', adds Jesudason.

Work will be complicated by the need to construct three cross passages under Long Valley.

Environmental restrictions could rule out the use of grout curtains to stabilise the ground at these points, because of the risk that this would pollute the ground water. Ground freezing is the other option.

The tunnel will in fact extend beyond Long Valley, to prevent the viaduct impacting on a built up area to the west. As a result, contractors will have to build a cut and cover box at the tunnel's mid-point. This will be built within a diaphragm wall and it is expected that the cut and cover box could act as a servicing point for the TBM.

The new station at Lok Ma Chau is to be built on 25m deep bored piles in wet ground, on the banks of the Shenzhen River which forms the border with mainland China.

Construction will involve creating a 5m high sand platform to raise the structure above water level.

Design of the station, by consultant Mott Connell, smooths passenger flows by keeping Hong Kong-bound passengers separate from those heading to China. It will be a 35m high structure standing on 25m deep bored piles.

The station will also incorporate a 230m span two-level cable stay pedestrian footbridge across the river to provide a link to a Shenzen metro station on the other side.

A cable stay structure was chosen to create a free span across the river, says KCRC's Lok Ma Chau construction manager Henry Liu Kwok Chuen.

This is because the river is prone to flooding and piers in the river bed could impede river flows during heavy rains upstream.

Planning ahead A series of future projects will join East and West Rail to form an integrated network by the middle of the next decade.

Expansion of KCRC's railway network is expected to continue after the East Rail extension to Lok Ma Chau opens in 2007.

The Corporation is already working on a series of proposals which, if approved by the Hong Kong government, will link East and West Rail together at two separate points. They could also give KCRC its first route across Victoria Harbour to Hong Kong Island via a new undersea crossing.

Top of the list of priorities for KCRC major projects director James Blake is the Kowloon southern loop. This highly complex combination of bored and cut and cover tunnel under the densely built up tip of the Kowloon peninsula will connect East Rail's new East Tsim Sha Tsui station with West Rail.

The project was earmarked for KCRC in the Hong Kong government's railway strategy in 2000 and the Corporation's proposals are aimed at getting the scheme into the design phase as soon as possible. 'If we get the go ahead we could start scheme design work this year, ' says Blake.

Blake favours the use of design and build for some of the work, such as a shaft for a station at Canton Road on the edge of Kowloon's main shopping district, an area packed with busy roads, high rise hotels and offices. 'Design and build will give contractors more input into the design process so they can deal with the constraints and conditions of the site, ' he says.

KCRC is also bidding against the Mass Transit Railway Corporation (MTRC) for permission to build a new line to relieve the busy southern section of East Rail. Both rail operators have to produce proposals before the Hong Kong government decides which to proceed with.

The Sha Tin to Central link will also take the new line under Victoria Harbour to the Central district and will run north through east Kowloon to Sha Tin via an MTR interchange at Diamond Hill.

The driving force is the need to get a rail link into East Kowloon, where redevelopment of the now disused Kai Tak airport site is expected to trigger a big upsurge in the local population.

To complete the circle KCRC wants to add a northern link between West Rail and East Rail, connecting Kam Sheung Road and Kwu Tong, providing a direct link between east and west for the first time.

The other major extension will be the Port Rail Line, which which will provide a direct freight rail link between the mainland and Hong Kong's container terminals.

Go ahead for this link depends on support from mainland China's rail authorities and the Chinese government, as its viability depends on how quickly freight trains can be processed as they cross the border between Hong Kong and the mainland.

'Rail freight is at a disadvantage to road if processing is slow, ' says Blake.

Development also hinges on the development of a major rail hub at Pinghu just inside mainland China.

KCRC is also competing with the MTRC for a regional express railway linking urban Hong Kong with the mainland Chinese boundary.

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