Wiltshire Council have revealed a new plan to repair the collapsed B4069 Lyneham Banks.

The key road linking Chippenham and Lyneham suffered major damage in a huge landslip in February last year, and the ground at the site remains unstable.

Since carrying out ground investigations in December, the council has been assessing three different methods for repairing the damage to the highway and guarding against future ground movements.

Council officers have now settled on a preliminary design for a scheme, costing around £5.9 million, to rebuild the damaged section of road and construct a piled retaining wall on the downward slope side of the carriageway.

This would be designed to stabilise both the B4069 and the slope itself, while the project will also improve drainage, remove imported material which is loading the slope, and strengthen the ground in the surrounding area.

The Wiltshire Gazette and Herald: The preliminary planThe preliminary plan (Image: Wiltshire Council)

Chris Cox, an associate geotechnical engineer for the council’s contractors Atkins, said: “Effectively it’s a dig and replace on a localised scale.

“This involves a substantial amount of work, the bored piled retaining wall is potentially 10 or 15 metres deep and may require anchoring to provide additional lateral restraint… that stabilises the slip.

“It comes with a capital cost of around £6 million of construction costs to complete.”

Explaining why they opted for this solution, the council’s major highways projects engineer Steve Wilson explained the decision was based on factors such as cost, the environmental impact, health and safety and land requirements.

He added: “Considering all the different criteria, the best balanced solution we have come up with is a combination of core works and a piled retaining wall.

“The exact details of this solution will need to be designed and the final proposals will be subject to detailed design.

The Wiltshire Gazette and Herald: The B4069 in February, 2023The B4069 in February, 2023 (Image: Newsquest)

“There’s some fairly critical work that needs to happen alongside the design effort for us to develop a scheme we can come forward with.”

The council will now begin the “intense and difficult” process of designing the scheme and seeking funding and legal approval, which is likely to take until the end of 2023.

Construction is not forecast to begin until spring 2024 and will not be completed until 2025.

Other solutions the council explored came with costs of up to £12 million and included completely excavating and replacing the failed slope.

The long timeframe for repairs will come as a blow to affected businesses, but the council added they have employed “open as usual” signage to reduce the impact on these businesses.