The viaduct - which carries the M6 motorway in north-west England - has been partially closed for two and a half years, causing disruption for the 160,000 motorists who use the route every day.

The US$101 million contract is one of the largest repair schemes ever undertaken by the Highways Agency. The road is carried on a pair of viaducts. Northbound vehicles use the original structure, which opened in 1963 and was refurbished in 1996. The new viaduct opened eight years ago. A routine inspection in July 2002 revealed that one of the main bearings on the northbound structure had failed. Further investigations found that all of its 148 bearings needed to be replaced.

Replacing each of the bearings involved jacking up the viaduct to allow the old units to be removed. This operation first required the strengthening of the beam above each bearing. Temporary jacking brackets were then bolted to the steel beams and the bridge was jacked up using four 300t jacks for each bearing.

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