July 20, 2024

Costain to support design of new Oxfordshire reservoir

Costain, an infrastructure solutions provider, has secured a contract with Thames Water to assist in the design of a new reservoir located in Oxfordshire.

The South East Strategic Reservoir Option (SESRO), a new 150m cubic meter reservoir, will ensure a robust water supply for Thames Water customers in London and the Thames Valley, as well as those served by Affinity Water and Southern Water. Additionally, the reservoir will foster new habitats, enhance biodiversity, and offer fresh leisure and recreation opportunities.

Costain will undertake clay compaction trials to assess the ground conditions at the intended site. Within the designated reservoir area, which is Thames Water property, three trial embankments will be constructed. Each will measure roughly 50m in length, 20m in width, and up to 3m in height, employing the same equipment and techniques planned for the actual reservoir embankments. Geologists will evaluate the behaviour of the Kimmeridge clay when subjected to varying compaction scenarios. The results will significantly influence the design and construction approach of the reservoir embankments.

Costain has also offered constructability advice to shape Thames Water’s design plans for the new reservoir. Leveraging its expertise and capabilities within the broader infrastructure ecosystem, Costain has delivered recommendations for design, construction, and sequencing for key components of the project, such as the embankment, tunneling, and the rail siding from the Great Western Mainline, located south of the proposed site.

Furthermore, Costain will deliver safety, health, environment, and quality (SHEQ) assurance, and serve as the logistical center for all ground and environmental investigations, which encompass archaeological evaluations on the premises.

The clay compaction trials are scheduled to start in the summer and may take anywhere from six to 12 months to finish, subject to weather conditions. Upon completion of the project, the land will be returned to its initial condition.

Graham Sugrue, framework director at Costain, commented: “The UK needs to upgrade its water infrastructure to meet increasing demand and remain resilient in the face of climate change. Working with Thames Water to help it develop a reservoir that will serve around 15m people across the South-East is a huge honour.

“This is a project that will see our customer benefit from the breadth and depth of Costain’s capabilities. Our construction and infrastructure experts in water, road and rail, in addition to our environmental, geological and archaeological experts, will work together to provide Thames Water with the information they need to secure government approval and a Development Consent Order.”

Leonie Dubois, head of engagement, land and consent, at Thames Water, added: “We have an excellent track record of working with Costain and we are looking forward to drawing on the team’s expertise for this exciting project. We continue to listen carefully to residents, who naturally want assurances about the design and integrity of the reservoir. This is why we’re starting the process to understand local ground conditions at a really early stage.” 

The news continues Costain’s longstanding relationship with Thames Water, and follows its recent award to upgrade sewage treatment works as part of its Wastewater Asset Assurance Programme. Costain continues to grow in the water sector, having secured long-term framework agreements with both United Utilities and Northumbrian Water to deliver strategic infrastructure programmes for the AMP8 period.