Queensferry Crossing five day 'snagging' shutdown this week
And they will press the old Forth Road Bridge back into temporary service to help them get over the week long hump.
But road users will again find themselves reduced to a 40mph limit in both directions for the duration.
It comes after the £1.3 billion superstructure has been besieged by lengthy delays on approaches and claims panels used in the wind shields have become dislodged in places.
They also admit the shutdown - which will see all southbound traffic routed across the old bridge - could see the proposed timetable decimated.
The works are planned to start at 10pm on Thursday and finish by 6am on Wednesday December 6, 2017.
It would be pushed back if the December weather - which has been predicted to be one of the coldest on record - takes a turn for the worse during the remedial action.
Contractors will only give the go-ahead if they get a clear window.
The end result could see the much heralded 70mph speed limit being introduced at the end of the works after drivers were reduced to 40mph then 50mph since opening.
In a news release, Transport Scotland said: “Having closely monitored the new bridge since traffic started using it, the contractors have identified snagging works which require the lifting of the surfacing around the bridge expansion joints.”
It continued: “The five day programme of works is weather sensitive and if the weather is unfavourable this may result in having to reschedule the start of the work or an element of the work once it has begun. Any changes to the programme of works will be publicised as soon as possible to keep road users informed.
“For the duration of the works southbound traffic will use the Forth Road Bridge (FRB) and northbound traffic will use the Queensferry Crossing. Signage and traffic management will be in place to guide traffic over the Forth and road users are advised to plan ahead. The closure will also enable traffic management procedures for diverting traffic to be fully tested.”
It is understood the snagging work will be carried out on the road surface at either side of the bridges expansion joints.
There are two expansion joints on the bridge at either end (north & south) and the road surface needs to be levelled at either side prior to traffic running at 70 mph.
The problem only came to light after traffic starting using the bridge and work has to take place before they could move fully traffic to 70 mph limit.
Transport Minister Humza Yousaf said, who has been closely involved with the project, claimed the issues were ‘“normal” and insisted there would be no additional cost to the taxpayer.
And he said the switch to the Forth Road Bridge would be a “live test” for any emergency use in the future too.
He said: “Snagging issues are normal with any major infrastructure project on this scale and complexity.
“Having closely monitored the bridge since its opening our contractors have informed us that this work is required around the bridge’s expansion joints prior to moving to a 70 mph speed limit.
“The benefit of the gradual move to motorway status for the Queensferry Crossing is that it allows these essential works to happen with the least amount of disruption possible.”
He continued; “Southbound traffic will use the Forth Road Bridge for the entire duration of the lane closures and northbound traffic will use the Queensferry Crossing. For the safety of road workers the speed limit will be 40 mph on both bridges for the duration of the works.
“It is important to also note this work is being carried out under the existing contract for the Queensferry Crossing and is therefore at no additional cost to the public purse.
“I would like to thank travelling public for their patience while the complex process of switchover is ongoing and in particular during these upcoming works.
“Utilising the FRB will provide Amey, the Forth Bridges Operating Company with an opportunity for live testing on the emergency crossover points ahead of any requirement to use them in future.”
It was claimed last week that a number of panels on the 3.5m high baffle barriers had been dislodge or fallen out.
They are designed to keep the bridge open in winds reaching 100mph.
Transport Scotland said the newly announced work was unconnected to the windshielding.
Once complete, the bridge would move to motorway status with the 70mph in place.