Engineers claim high risk tower design will make it hard to nail down a fixed price.
Plans for the controversial £118M New Wear Bridge in Sunderland were close to collapse this week after two of the four shortlisted contractors withdrew their bids.
NCE can confirm that Ferrovial and Balfour Beatty have pulled their bids for the complex cable-stayed crossing.
It is understood that both ditched their bids because the project was becoming too complicated and risky to build.
“Contractors will be terrified of it. It’s a very unusual bridge and very complicated to build”
Simon Bourne, independent consultant
Skanska had hoped to bid for the project but failed to make the shortlist when it was announced last October.
That leaves just Northern Ireland-based Graham and Vinci of France bidding to build the 336m long bridge between Castletown and Pallion. Graham’s engineering designer is Ramboll and Vinci’s is Tony Gee & Partners.
Bridge experts had previously warned that contractors would struggle to construct the bridge (NCE 17 May 2012). They predicted this week that the lack of bidders would lead to the project being scrapped.
“I am not at all surprised,” said independent bridge consultant Simon Bourne. “Contractors will be terrified of it. It’s a very unusual bridge and very complicated to build. It saddens me to say, but I suspect that the scheme will just get cancelled,” he said, adding that, faced with only two bidders, the council would find it hard to ensure bids were competitive.
Designs produced by Spence Architect and structures consultant Techniker include two cable stay towers - one 180m tall and the other 140m tall - on either side of the deck.
The towers taper and curve towards each other longitudinally, overlapping when viewed in elevation. Despite the overlap, the design does not include a physical connection between them.
Bourne said the unusual layout would make the structure hard to build. He said it would be difficult to balance the forces going through towers as contractors attached cables to the deck.
Contractors would also have little scope to innovate as they must follow a sequence of more than 400 stages to keep the structure stable during construction.
“It is equivalent to building the largest prestressed concrete bridge in the world - but vertically, not horizontally - on enormously large foundations, and then also building a deck as well, and then also connecting the two with cable stays,” said Bourne. “The risks of its hugely unique nature are very profound.”
A source close to one of the team which withdrew also cited the complex nature of the structure as the reason it pulled out.
“The contractor took the view that the project was not worth it,” said the source.
Bourne said that if the project does go ahead, it was likely that contractors would insert numerous caveats to limit their exposure to unforeseen risks. This would make it hard to tie the winning bidder to a fixed price.
Client Sunderland City Council insisted the project would go ahead.
“With two internationally acclaimed contractors in the bidding process, Sunderland City Council is confident that it can deliver a landmark, affordable, and much needed new bridge across the Wear,” said council leader Paul Watson.
Remaining bidders were also confident.
“We want to show that it can be built and prove the doubters wrong,” said a source close to one of the bid teams.
Watson added that the project would generate a “very high return for the taxpayer”, claiming £4 in economic benefits will be generated from every £1 spent.
The bridge is expected to cost £53.8M. Associated highway improvements and a contingency allocation take the total scheme cost to £117.6M.
The Department for Transport committed £82.6M to the scheme last December. Sunderland City Council is contributing £31.9M, with the remaining £3.5M coming from former regional development
agency One North East.
The council aims to name a winning bidder in April. Construction is expected to take two to three years.