By Aileen Robertson

FORTH ROAD Bridge chiefs have admitted the structure’s main cables may have to be replaced, a move which would plunge Fife’s roads network into chaos.

Forth Estuary Transport Authority (FETA) is spending £1.5 million on a feasibility study to determine if it is possible to replace the cables and how much it would cost.

In 2004, an inspection revealed a small proportion of wires inside the cables had broken.

Engineers are working to design a system to dry out the insides of the cables in an attempt to halt corrosion.

Despite hiring a team from the same Japanese firm that installed dehumidifying equipment on longest suspension bridge in the world, FETA maintains there is no guarantee the system will work and a “plan B” must be drawn up.

Barry Colford, FETA depute general manager, said, “We’re commissioning this study in case we can’t stop the corrosion that has been discovered inside the Forth Road Bridge’s main cables.

“We’re optimistic that we can stop the corrosion using a specially-designed dehumidification system to dry the cables out.

“However, although we’re confident that this is the best solution available, there isn’t a sufficient body of evidence available to prove that it will be successful in all cases.

“This study will tell us if it is feasible to replace or augment the main cables, should this become necessary.”

However, the experts also face “several significant engineering challenges,” Mr Colford said.

He continued, “For example, the main towers and cable saddles (where the cable rests on the tower) have already been strengthened and new load paths would have to be identified for any new cable.

“The existing anchorages (for cables, at either end of the bridge) may need to be replaced.

“And the existing truss (the structure that the road sits on) is over-stressed and will need strengthened.”

Replacement could mean closure for two to three years.

Mr Colford continued, “The study will also assess the other practical implications of carrying out such a task.

“Of critical importance is the extent of the traffic restrictions that would be required, and the effects of those restrictions on the adjacent road network.

“Could the cable be replaced or augmented with the bridge even partially open?

“This is a key question considering that the project could take two years or more to complete.”

Strict health and safety laws must also be considered.

Later this month, the FETA board will be asked to award the contract for the study to consulting engineers WA Fairhurst & Partners.

Transport minister Tavish Scott has asked for the findings by the end of May.