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Special Mersey Gateway report: Deck design key to win

Significant design changes that will save “tens of millions” of pounds, including a switch to a concrete deck last week won Spanish- led Merseylink Consortium preferred bidder status for the £600M Mersey Gateway bridge.

Client Halton Borough Council declared the consortium comprising Spain’s FCC Construcción, Germany ‘s Bilfinger Berger, and Australian investment bank Macquarie preferred bidder last week.

It beat off bids from a Balfour Beatty/Bouygues consortium and a consortium of Bam Nuttall, Hochtief and Spain’s Iridium.

Mersey Gateway

New design: Cable design and deck are different to the reference design (inset)

The contract is to design, build, finance and operate a new toll bridge over the River Mersey between Runcorn and Widnes, together with associated link roads.

“I am thrilled that we have found a solution that keeps the iconic design”

Rob Polhill, Halton Borough Council

The three tower, four span bridge will be built by a construction joint venture led by FCC and also featuring Kier and Korean contractor Samsung.

Key to Merseylink’s win was its decision to replace the steel box girder bridge deck used in consultant Gifford’s original reference design with a conventional cast insitu, post-tensioned concrete box.

This move was driven by the construction joint venture’s lead consultant Flint & Neill. The switch from steel to concrete has been known to have brought costs down, but it is unclear as yet how much money has been saved by the alteration.

The council said that savings amounting to “tens of millions of pounds” on the £2bn project budget had been identified.

Other changes include a redesign of the cable arrangement.

The original design features three, monotower masts positioned in the centre of the deck with parallel cable-stays.

With this design, the height of the cable connections on the tower is proportionate to the horizontal distance to their mounting point on the deck.

Flint & Neill’s design replaces this with a modified fan layout where the cables converge towards the top halves of the towers. This arrangement is considered to more efficient in terms of load transfer.

Other changes include a redesign of some junction layouts.

“We asked the private sector to build the bridge on a fixed price basis,” said Halton project director Steve Nicholson. “That required us to give them design freedom.

Bidders were given flexibility to decide on detailed design, construction methodology and approach viaduct designs, although they were restricted to a three or four span cable-stayed crossing design.

Despite the changes, the council said the bridge retains its “iconic” look. Planning approvals in place demand that the river crossing be a ‘“cable stay[ed] retaining the concept of an iconic gateway to the Liverpool City Region”.

“The outcome demonstrates the value in allowing the private sector to modify the design to reduce costs,” said Nicholson.

“The quality of all the bids we received and the work put in by all the shortlisted bidders has been of a very high standard, and each one satisfied our challenging requirements,” said Halton Borough Council leader Rob Polhill.

“I am thrilled that we have found a solution that keeps the iconic design, but also produces significant financial savings for the council and the government,”

Merseylink will now finalise the design before presenting it to the local planning authority.

The consortium will also enter financial negotiations with Halton with the aim of reaching financial close by the end of the year. Construction is slated to start in January 2014 and is due to take three and a half years.

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