Cost for repairs to ‘crumbling’ Cumberland basin network could be £50m

Fears of a “catastrophic failure” of Avon Bridge have prompted Bristol City Council leaders to kickstart up to £50million of repairs to the crumbling Cumberland Basin road network.

Cabinet members are due to approve an initial £4.25million on Tuesday, September 5, for inspections and structural maintenance for the major works, which are expected to last five years.

A report to next week’s council meeting said the 1960s design of Avon Bridge, on the A3029 Brunel Way linking Cumberland Basin with Ashton Gate and beyond, was “no longer approved in the UK for any new proposed highway structures as the potential risk profile of potential catastrophic failure is considered to be unacceptably high”.

The report said the degradation of the structure and other nearby elevated roads were “accelerating” and that the final bill and timescale would only be known once the inspections had been completed.

Avon Bridge has “a considerable number of inherent high-risk construction design features” and carried two-and-a-half times the volume of traffic anticipated when it was built, the report said.

It said highways officers would work with the team currently developing a masterplan for the wider redevelopment of the area, which the council has renamed Western Harbour.

The report said that “due to concerns about the structural integrity” of the bridge, a special inspection in 2021 led to “urgent strategic capital works” to re-waterproof and resurface the road and replace all four expansion joints to address water and gritting salt getting into the joints.

“Now that the water ingress into the structure has been addressed, an ‘active management plan’ is essential to avoid uncontrolled deterioration of the structure,” it said.

“Whilst further deterioration is likely given the age of the structure, the role of the authority is to manage the decline of the whole of the Cumberland Basin until its overall future is clearly defined through the Western Harbour master planning.”

The report said the inspection found “extensive issues” with the expansion joints, concrete and the underside of the bridge.

It said: “Significant elements of the Cumberland Basin network are nearing the end of their intended working design life and are now deteriorating at a significant rate.

“The overall Cumberland Basin structure complex has deteriorated much faster than originally designed for.

“Given the condition of the Cumberland Basin network, additional capital investment is now required to manage its ultimate depreciation and decline, and to facilitate the emerging Western Harbour development.

“Currently over a third of the £1million annual structures [bridges] maintenance budget is being spent on the Cumberland Basin network alone. 

“Due to the inflation and depreciation in the structure, the estimated cost for repairs to the Cumberland basin network is envisaged to be between £40million to £50million.

“The Western Harbour regeneration project intends to deliver affordable homes in this sustainable location, while modernising the wider transport network and a resilient flood defence system instead of simply replacing the network as is.

“Now at the master planning phase, it will consider the condition and functions of the Cumberland Basin network as more information is made available through the active management plan this report proposes.”

It said the “continuing ongoing deterioration” of the Cumberland Basin’s roads was “now accelerating” despite the council spending £250,000 to £500,000 a year on maintenance.

“As the Cumberland Basin complex is a pivotal strategic arterial corridor route, after the required capital investment is implemented and executed, future consideration needs to be given on how we pay for the required capital works undertaken to bring the whole complex to required condition.”

The report said part of the cost would be met by underspends in other capital projects while funding would be sought from the West of England Combined Authority and the Government.

“It is stressed that the estimated costs contained in this paper at this stage may be subject to increase once in-depth surveys have been completed,” it said.

“As with all major bridges and structures projects, it is not until any project and scheme is physically executed on site (despite all reasonable investigations and previous inspections), that many ‘unknowns’ become apparent.”

A finance officer said in the report: “The current capital investment issues with the Cumberland Basin complex and Avon Fixed Bridge will be reliant on the future proposals and aspirations of the Western Harbour development and its vision for the area.

“It is important that the future vision is established asap as it has a significant impact on the approach and the scale of refurbishment that might be appropriate, especially if the Western Harbour development proposals include the dismantling of the current complex.”

Work will be staggered over the next three to five years.