The amount that Scottish Borders Council will spend on restoring the Union Chain Bridge at Horncliffe has gone up from £550,000 to £1m.
The initial estimate for the work was around £5m, but Historic England has since discovered that more work is needed to restore the historic bridge’s original features.
The projected costs now stand at £7.8m, and the regional council has been working alongside its Northumbrian opposite number to put together a Heritage Lottery Fund application to help meet that bill so the bridge can continue to be used.
Northumberland County Council has already increased its commitment to £1m, and this week Scottish Borders Council agreed to follow suit to bridge the £900,000 funding gap.
To pay for its share of the increased costs, the council will divert funding from its roads and bridges capital budget to the project.
Others contributing are Historic Scotland with £500,000, Historic England with £200,000 and Friends of Union Chain Bridge with £100,000.
The Heritage Lottery Fund application is now for £5m.
The Tweed crossing was the longest suspension bridge in the world when opened in 1820 to link Horncliffe in England with Fishwick in Berwickshire.
Currently the oldest suspension bridge in the world still carrying vehicles, it is a grade-one listed structure in England and a category-A listed building in Scotland, the highest designations.
A report to councillors said: “The Heritage Lottery Fund is supportive of the project due to its substantial heritage value but also the international significance and educational opportunities that can be achieved through a potential project.”
Current funding of bridge maintenance is based on a 50-50 contribution between the two councils following an agreement dating back to a report in October 1996.
In 2020, the bridge will celebrate the 200th anniversary of its opening, and it is hoped the works can be completed by that date. However, it is already falling behind schedule, and the Heritage Lottery Fund application missed the June deadline.
Scottish Borders Council wants to see an independent project manager appointed to lead the project team “to create a controlled approach to the delivery of the Heritage Lottery Fund application process and ensure that targets are met going forward”.
The report to councillors goes on: “Northumberland County Council has made significant structural changes to their staffing levels that has left the authority without the key personnel to complete the Heritage Lottery application process, ultimately causing a delay in the application until August 2017.”