Repair work on a viaduct forming part of the link road off the M6 on to the M5 in West Bromwich has already been delayed five months with a revised opening date of November.
That has now been pushed back to “by Christmas” as contractors discovered further damage in parts of the structure.
Highways England said: “Although unforeseen circumstances have delayed the waterproofing work on the ageing viaduct, the company and its contractors are working flat out to finish the project as soon as possible.”
Work on the £6.4m job started in January in Area 9 where EM Highways holds the Asset Support Contract.
Highways England Project Manager Jess Kenny said: “We understand this has been frustrating for drivers, but unfortunately there was no way for us to tell the full extent of the damage until we’d already started work.
“We were only able to assess the true extent of the concrete damage and the steel corrosion inside the structure once we had removed the surface.
“While the amount of damage is roughly as much as we predicted, the most damaged areas are over the parts which carry the weight of the viaduct, which are crucial to the integrity of the bridge. So repairs have to be done with painstaking precision and care to prevent the bridge becoming weak.
“We have had to completely change our work plan, and only treat small sections of the road at a time which has lengthened the timescale of the work. But we are working hard to complete this as soon as possible.”
The waterproofing work is being carried out between the M6 junction 8 at Walsall to the south and the M5 at West Bromwich.