MILESTONE Infrastructure contracted Pavenet to Break ground and set up the works compound and car park for this long term project.
Transport chiefs say they are being forced to carry out the work now as the westbound Redbridge viaduct, which was built in the 1960s, has begun to deteriorate.
Experts say the bridge’s joints are leaking salty water through to the base of the structure, which has now begun to crack, exposing its metal supports.
The county council’s chief engineer for highway structures, Brian Hill, says the bridge is in such a bad state that the authority would be forced to impose weight restrictions.