The A59 at Kex Gill will not reopen until June and is costing £750,000 to repair, according to North Yorkshire Council.
An extensive repair scheme is underway to stabilise a landslip on the stretch of the A59 between Skipton and Blubberhouses.
There will be extended hours and night working to allow the road to be reopened before the end of June.
The road, which runs across a rural stretch of the county on the edge of the Yorkshire Dales National Park, is deemed to be one of the most important strategic routes nationally as it provides a key link running across the country.
The route closed in February after a crack appeared in the verge as a result of poor weather over the past few months.
In a press release, the Council said:
"February was one of the wettest on record and the persistent rainfall has continued to make the situation worse, with further movement since the start of the closure – something that has been substantiated by geologists.
"Kex Gill has a history of landslips, so a multi-million pound scheme has been launched to create a new three-mile stretch of road. However, the existing road had to be closed again after the latest landslip."
The council's Corporate director of environment, Karl Battersby, said:
“We have reached a point where we can appoint a contractor and decide on the most efficient and cost-effective repair scheme, with preparatory work now under way.
“There have been more than 10 landslips on the A59 at Kex Gill, between Church Hill and North Moor Road, so the ongoing re-alignment scheme is needed now more than ever.
“The repairs will include driving long sheets of steel into the ground to create a structural wall. Once this has been completed, contractors will fill in the excavated area between the steel sheets and the road to provide strength and stability.
“Relocating communications cables and completing drainage and resurfacing works once the area is filled also forms part of the scheme.
“Until the road is reopened, we advise road users to follow the signed diversion route. We would again like to thank people for their patience and reiterate that we are doing all we can to complete the repair as quickly and safely as possible.”
The contractors appointed to manage the project are Sisk, with Ivor King carrying out the specialist steel sheet piling.
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