A new $32-billion railroad project be­neath central London won U.K. government approval on Oct. 5. Seven years of construction will begin in 2010 on the Crossrail project, including a whopping 41.5 kilometers of tunnels.

Under development since the early 1990s, the 118.5-km-long east-west Cross-rail system will link surface networks on either side of London with twin, 6-meter-dia bored tunnels. It will be Europe’s larg­est civil engineering proj­ect, claims a Dept. for Transport official.

Cross London Rail Links Ltd., the sponsor, aims to start procuring construction contracts next year. Work on Cross-rail will overlap with the last two years of effort on London’s Olympic sites for the 2012 Games.

With other major infrastructure jobs winding down, U.K. contractors will have enough capacity to handle Crossrail, claims John Wilson, technical director of the Civil Engineering Contractors Association. Working in the congested city means logistics will be the biggest problem, he adds.

CLRL, owned by Transport for London and Dept. for Transport, has four design firms working on the tunnel sections and one on surface stretches. They are led by CLRL’s development manager Bechtel Inc., San Francisco.

As now planned, nine TBMs will drive the tunnel from four access points. They will work in mainly good clay along the western 6 km. But earth pressure balance machines will be needed in eastern drives.

Ground conditions in the eastern drives will include water pockets, gravel, lignite and fissured clay. Few tunnels were built in that area until the Jubilee Line Extension and the Channel Tunnel rail in the last decade.