B4069 Lyneham Banks landslide stabilisation, Wiltshire, UK

NEC has been used to procure the complex reconstruction of a rural road in Wiltshire, UK which was destroyed by a landslide in February 2022. The project was shortlisted for the Upgrade and Renewal Project Award in the 2025 British Construction Industry Awards.

Client Wiltshire Council let the B4069 Lyneham Banks stabilisation project to contractor Octavius under a £3.5 million NEC4 Engineering and Construction Contract (ECC) Option A (priced contract with activity schedule) in May 2024. The work was successfully completed on time and budget in April 2025.

Caused by a combination of historic weaknesses, increased groundwater flows and extra loading from nearby development, the landslip dislodged about 90m of the B4069 and carried it 25m downhill. As a result, a 14.8km section of the road between Lyneham and Chippenham had to be closed for 3 years, causing major disruption to its 5,500 daily users. 

In addition to reconstructing the road on its original alignment, the contract included building a 108m long anchored retaining wall made from 120 no. 14m deep contiguous reinforced concrete bored piles with a 1.5m high capping beam. The slopes above and below the road were regraded, and 560m of linear drainage and 1,000t of stone counterfort drains were installed.

The designer and NEC project manager was AtkinsRéalis. 

Speed and quality

Highway project engineer Jack Francis says the Council selected an NEC4 ECC Option A Contract for the Lyneham Banks scheme following a procurement options exercise. ‘The primary drivers for delivery were speed and quality since the road had been closed for over 2 years and there was a pressing need to return this key route to the local network.’ 

He says the Council worked closely with its term consultant AtkinsRéalis to determine the most appropriate route to market, exploring various options. ‘We had successfully used NEC contracts for the majority of major highway works in Wiltshire and it was concluded that this would be the most appropriate mechanism to deliver the works at Lyneham.’

Francis says the tendered scheme had been well developed, with a full detailed design package. ‘It was therefore agreed that an NEC4 ECC Option A contract would be used to give us greater cost certainty at the outset. Following a competitive tender period, Octavius was selected as the preferred provider to deliver the works in May 2024.’

He says in line with the NEC requirement to act in a ‘spirit of mutual trust and co-operation’, all parties then worked collaboratively and effectively to deliver the works. ‘The contract also ensured that parties were treated fairly and could work in an open and honest environment towards the main goal of reopening the road.’

Francis says that early in the construction phase it was found that land issues were going to cause problems and potentially hold up delivery. ‘By making good use of the NEC early warning process, the team worked collaboratively to mitigate this and other issues, enabling the works to keep progressing and for the road to reopen on time and budget in April 2025.’ 

Collaborative approach

AtkinsRéalis assistant geotechnical engineer Christopher Cox says the project exemplified NEC-inspired collaborative working. ‘There was close cooperation between the client, contractor and specialist subcontractors, and this collaborative approach to supply chain engagement ensured efficient project delivery.’

He says the project adopted an enterprise-style model, promoting shared outcomes and fair risk and reward allocation. ‘Early contractor involvement and continuous communication facilitated problem solving and decision making, driving better outcomes in terms of cost, time and quality. The integration of lessons learned from previous landslide remediation projects further enhanced the collaborative approach, enabling the team to deliver a robust and resilient solution.’

Cox says by acting as stated in the NEC contract, the team overcame a range of unforeseen obstacles, including ground condition variability, delays in gaining third-party land access and ongoing slope movements elsewhere on the site. ‘Despite these challenges, the works were delivered on time and budget, which was a major achievement and demonstrates the effectiveness of NEC’s collaborative approach.’

Benefits of using NEC

• NEC4 ECC Option A contract was considered the best option to achieve the necessary speed and quality, and gave the client greater cost certainty at the outset.
• NEC requirement to act in a ‘spirit of mutual trust and co-operation’ ensured all parties worked collaboratively and effectively to reopen the road on time and budget.
• NEC early warning process encouraged the team to work collaboratively to mitigate issues, enabling the works to keep progressing.
• NEC ensured all parties were treated fairly and could work in an open and honest environment.