Design stalls Balfour Heathrow restart

Balfour Beatty's hopes of restarting work on the central area of the Heathrow Express by mid-February following the tunnelling collapse in October last year have been dashed. The operation has been put back several weeks because of problems in drawing up an engineering solution.

Although still on the drawing board, the final plan will - according to Heathrow Express - 'be a stronger design all round'.

A spokesman said: 'With all the other facilities around - gas, water and existing services - we must have a design that is robust. Access is a difficulty: we have a large depth to go down, yet Car Park Three is close by.'

Other parts of Balfour's œ60 million project are going well. The running tunnel leading to the Central Terminal Area from the north, being tunnelled conventionally, has driven 1km since November.

Before the NATM tunnel collapse, the plan was to have a tunnelled area ready to meet the tbm's first drive when it breaks through in March. But now the contractor plans to detach the machine's shield and skin and leave it in place while the tbm returns to the beginning to start the final phase of the twin-bored tunnel.

British Airport Authority still hopes that the œ300 million Heathrow Express project will be completed on time. It was running four months ahead of schedule when tunnelling in the Central Terminal Area worksite (Terminals 1,2 and 3) collapsed.

The insurance claim of œ50 million is the biggest ever on a UK civil engineering project.