A water main may have to be re-lined rather than replaced to avoid causing further damage to a railway tunnel on a heritage line.

Yorkshire Water experts are investigating the best way to carry out vital improvements to the water pipe which crosses the Ingrow tunnel in Halifax Road, Keighley.

The water utility stopped the work on October 12 when contractors dislodged brickwork in the tunnel. The Keighley & Worth Valley Railway had to close the line between Keighley and Haworth, which meant steam train services could only run on the northern section of the line. Temporary traffic lights have operated in Ingrow since the work stopped, and part of the main road remains dug up.

Since then, the railway has started legal proceedings for compensation for lost trade.

Yorkshire Water says the tunnel is now safe.

Contractors were unable to immediately resume replacing the ageing water main and are considering the alternative of installing a special plastic layer inside the existing pipe.

"Over the next few days experts will send a robot down the pipe with a TV camera so they can check its exact state," said a Yorkshire Water spokesman. "Once investigations are finished, the work is expected to take a further two weeks.''

Graham Mitchell, railway society chairman, said he understood that the contractors preparing to lay the new water pipe had gone too deep and damaged the brickwork.

It had taken 12 days to repair the damage by fitting a large steel plate to the roof. Passenger numbers on the line in October slumped by about a third to 4,608.

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