18 September 2001
KCRC welcomes endorsement of tunnel option
The Kowloon-Canton Railway Corporation (KCRC) today (Tuesday) welcomed the endorsement by the Chief Executive in Council of the tunnel option for the construction of the Sheung Shui to Lok Ma Chau spur line.
A KCRC spokesman noted that the Environmental Impact Assessment Appeal Board, in delivering its judgement on the appeal against the Director of Environmental Protection’s decision by the KCRC, considered the viaduct option had merit if definitive evidence could be produced to show that the proposed mitigation measures and construction methods would be successful.
"This will take two years or more to establish, with no certainty of definitive end result.
"The earliest possible provision of a second rail boundary crossing is more than ever of critical importance. To achieve this, a part tunnel and part viaduct option has been chosen. This strikes the best balance between timing and certainty of controlling impacts on the environment," he said.
The 4.3 kilometre tunnel follows the original gazetted alignment, and completely avoids the surface of Long Valley. There will be no visual, noise, dust or other impacts on the environment there.
The spur line will go underground just north of Sheung Shui station near the River Sutlej, pass through Kwu Tung where an underground station box will be built, and resurface at Chau Tau. From there, the spur line will continue on viaduct along the gazetted alignment to the Lok Ma Chau boundary crossing terminal.
Referring to concerns expressed by some interest groups that tunnelling might result in leakage of ground water table or blowout at ground level, the spokesman said the Corporation had considerable experience working successfully in equally demanding conditions encountered when boring the Tsing Tsuen Tunnels of West Rail.
"Our Tunnel Boring Machine (TBM) is capable of boring in hard rock and in wet or mixed ground conditions. It uses the Earth Pressure Balance (EPB) system to maintain stable soil and water conditions during tunnelling, thereby avoiding the risk of ground settlements or blowouts.
"The ground water table will not be affected. This is because the tunnel is fully lined with watertight precast concrete segments at the same time as the tunnel is being bored. This prevents surrounding ground water from flowing into the tunnel. Experience gained in building the Tsing Tsuen Tunnels has proven this.
"Contamination of the surrounding ground will not occur, because the EPB system uses a bio-degradable foam for ground stabilisation, avoiding bentonite.
"Excavated materials will be taken away through the launching shaft at Chau Tau to designated government sites. Environmental impacts at the shaft will be controlled by special measures, also proven at West Rail, to comply with all relevant requirements," he said.
The interface between the spur line and East Rail will require the temporary relocation of the existing East Rail tracks near Sheung Shui, and the construction of underground works in close proximity.
Neighbouring large water mains carrying water from the Mainland and some nearby sewer pipes will be affected, but all of these works will be carefully planned and executed to avoid disruption of these critically important public services. The two-year deferment of the originally programmed completion date provides the time needed for these relocation works.
The spokesman said a new Environmental Impact Assessment (EIA) Report will be compiled for the new alignment. It will include the usual public consultation process and, in this connection, the Project Profile of the spur line will be published tomorrow for public exhibition.
The total construction cost of the spur line with a tunnel through Long Valley is about $10 billion at 2001 prices, or $2 billion more than the viaduct option. Nevertheless the Corporation is confident that the increased cost of the spur line can be met by the Corporation from its own resources and that, in spite of the increase in cost, the project will generate a healthy internal rate of return. The Corporation’s aim is to commission the new line for service sometime between the end of 2006 and mid 2007.