Forth road bridge set for a new lease of life

THE threat to the Forth road bridge from corrosion is receding, new checks on its main cables are expected to show. The news would further postpone potential curbs on traffic – but also call into question the need for a new bridge costing as much as £1.6 billion.

Bridge chiefs told The Scotsman yesterday that dry air being pumped into the cables to halt the corrosion is coming out dry, indicating the process is stabilising the deterioration.

They are now increasingly confident an impending inspection of the cables which hold up the bridge will show no further deterioration.

That would stave off traffic restrictions such as a lorry ban, which it was thought could be required as early as 2017.

The threat prompted ministers to approve a new bridge beside the Queensferry crossing, which is due to be completed by the end of 2016 in case that worst-case scenario came to pass.

The inspection – the first since 2008 – is due to start in April, with results expected in November.

It is also the first check since dehumidification work – blowing dry air into the cables – started in 2009.

Inspections are also under way on the main cables’ anchorages at either end of the bridge – the last part of the cables still to be checked.

Barry Colford, the Forth road bridge’s chief engineer and bridgemaster, said of the inspection: “This will give us further confidence that dehumidification is having an effect on the cables.

“We are getting good results – dry air is going in and dry air is coming out. This is giving us added confidence,” he added.

“But we still need to inspect the cable to confirm its condition. I am expecting that we will find a situation no worse than in 2008, but I cannot guarantee it.”

Mr Colford said if that was confirmed, the “likelihood” was that the earliest date of any traffic restrictions could be pushed back. He said: “I do not want to pre-empt the inspection, but that’s what we are hoping we will find.”

The inspection will examine six areas of the cables compared to just two, near the middle of the east cable, last time.

The original inspection of the two feet-thick cables in 2004 showed corrosion far worse than expected among the 11,618 pencil-thin wires they comprise.

Analysis found the anticipated weakening of the road bridge could mean traffic restrictions having to be imposed by 2014.

However, this was later put back to 2017 following the second check four years ago.

Mr Colford predicted the latest inspection “will give us more confidence to push it [the earliest date for restrictions] further into the future”.

However, he stressed the new crossing, which is expected to cost between £1.45bn and £1.6bn, was also required to avert major traffic disruption on the Forth road bridge during increasingly- frequent repair work.

This includes replacing expansion joints on the bridge carriageways, which has been postponed until the new bridge opens.

The Forth road bridge also needs more regular resurfacing because of wear from rising traffic volumes.

It carried 24.5 million vehicles last year – twice its design capacity and nearly 1 per cent more than in 2010.

Mr Colford said lane closures had already caused three-hour traffic queues, even during weekends.

He said: “The Scottish Government felt the risk at the time, together with the nightmare scenarios we were presenting [about maintenance work] were enough to persuade them to build a new crossing.”

Last night, the Greens said if the latest cable predictions proved correct, it would highlight the SNP’s “poor decision” that had blown Scotland’s transport budget.

Green MSP Patrick Harvie said Mr Colford’s comments showed the cost of the new bridge would be wasted.

Mr Harvie, a former convener of Holyrood’s transport committee, said: “If correct, this will highlight the poor decision the SNP made to plough ahead with the additional bridge. Greens said repairing the existing bridge would have been better value.

“Instead, ministers have blown Scotland’s transport budget on a vanity project.

“The funds squandered could have been transformational for Scotland’s transport infrastructure, making the transition to low carbon transport a reality.”

Transport minister Keith Brown has said: “The Forth replacement crossing project is absolutely vital to ensure Scotland’s economic wellbeing.

“Should the crossing be restricted or not available, there will be dire economic and social consequences.”

Mr Brown also warned MSPs when they gave final approval for the project in 2010 that they would be “condemned by everyone in Scotland” if they had postponed it until this year’s cable inspection and found they had made the wrong decision.

Gordon Mackenzie, the Liberal Democrat transport convener of Edinburgh city council, which had sought to postpone the move until the cable inspection, said he now accepted MSPs’ decision.

He said: “We hoped the dehumidification would work. Clearly, the Scottish Government decided it could not take the risk and pressed ahead with the bridge contract.

“We felt there was an opportunity to give dehumidification a chance, but that was not accepted by the Scottish Parliament, and we have had to move on.

“We are now focusing on minimising the impact of the new bridge on traffic in west Edinburgh.”

An industry source told The Scotsman yesterday nothing would be gained from postponing construction of the new bridge at this stage.

“Extending the contract would cost too much because the contractors will have priced their bid for an agreed timescale,” the source said.

“If the corrosion predictions are confirmed, it will provide a bit of breathing space, but ministers will want to press on so they can cut the ribbon [to open the bridge].”

Labour’s infrastructure spokesman, Richard Baker, said: “If bridge traffic did have to be reduced before the new Forth replacement crossing was opened, it would clearly have a detrimental economic impact on Edinburgh, Fife and beyond.

“Signs that this is now going to be less likely is very welcome news indeed.”