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The £5 million Great Shefford Flood Alleviation Scheme has been completed with the installation of nearly 650 metres of underground pipes, an underground box culvert and a new open vegetated stream that will be a boost for nature.

The Environment Agency noted that the village of Great Shefford has long been affected by flooding from the nearby stream, which caused damage and disruption to homes and infrastructure in 2014, with the risk of it happening again remaining in subsequent years.

The civil engineering initiative to protect the village was commissioned by the Environment Agency. Advantage RSK and fellow group company Binnies acted as the NEC4 project manager, with Jacobs providing the initial concept design and BAM Nuttall acting as the contractor that subcontracted the detailed design to Stantec. The project commenced in the late summer of 2022 and was completed in the summer of 2025.

Advantage RSK Project Manager Sameer Shinh said: “The scheme has been designed to intercept and divert excess water from the Great Shefford Stream during periods of high water and will reduce the impact of flooding on 26 residential properties, seven commercial properties and the A338 Wantage Road. The excess will flow through a 648-metre underground concrete pipeline, a culvert system that runs beneath a farm track and then a newly created 138-metre open river channel that will safely release floodwater into the River Lambourn through a new confluence.

“The combined team has come from a wide range of disciplines, from engineering and operations to environmentalists, geomorphologists, quantity surveyors, archaeologists, land consultants and health and safety professionals.”

Sameer said that, in addition to reducing flood risk, the design enhances biodiversity by integrating native planting and sustainable landscaping techniques into the new open stream, delivering a system that is both technically robust and environmentally sensitive.

He said: “The River Lambourn holds dual environmental designations as both a Site of Special Scientific Interest (SSSI) and a Special Area of Conservation (SAC). The open river channel will be planted with native species and will contribute to the +20% biodiversity net gain target, while offering a visually appealing and sustainable outlet into the River Lambourn.”

Sameer explained that high groundwater levels, the result of an exceptionally wet 2024, created challenges for the project.

He said: “The pipeline route reaches six metres underground, and the biggest risk was that water could inundate the excavations. Additional dewatering was carried out, and the work started later, as it was vital to wait until the groundwater levels were on a sustained downward trend.

“In addition to the groundwater levels, technical constraints due to space and access limitations had to be considered.”

Silt pollution can cause serious damage to the environment, and to minimise the risks and impacts of sediment from construction activities, innovative techniques were used. Sameer explained that lamella separators – a type of sediment treatment tank – were used to remove suspended solids from water so it could be released back into the river, and groynes were deployed to slow the flow of water and encourage sediment to drop out naturally. Silt curtains and booms were placed at the confluence of the river and the new built channel to prevent silt from polluting the nearby waterways.

The project has supported the training and development of emerging professionals. Graduate engineers from RSK’s early careers programme have been meaningfully engaged in site visits, contract administration and coordination between the client and contractor, Sameer said. Through this involvement, they have gained practical experience in the implementation of a New Engineering Contract (NEC) and in the technical aspects of flood risk engineering, helping to build their competence and confidence in real-world project delivery.

Environment Agency’s Angelin Hallaways said: “This scheme highlights how collaborative contracting under NEC ECC Option C (Target Cost with Activity Schedule) enables the delivery of practical flood risk management while prioritising environmental enhancement. Through open dialogue, adaptability to evolving site conditions and the adoption of alternative designs, we have achieved cost-effective, constructible solutions that satisfy both technical and ecological objectives. It exemplifies how modern infrastructure can harmonise with nature rather than oppose it.

“This was a design and build contract, which helped innovation, streamlined decision-making and clarified accountability – particularly important with the changing conditions on site.”