Costain, a UK-based infrastructure solutions company, has secured a contract from Thames Water to assist in the design of a new reservoir in Oxfordshire. The project, known as the South East Strategic Reservoir Option (SESRO), aims to enhance water supply resilience for 15 million people across London, the Thames Valley, and areas served by Affinity Water and Southern Water.
The proposed SESRO reservoir, with a capacity of 150 million cubic metres, will not only ensure reliable water supplies but also promote local biodiversity by creating new habitats and offering leisure and recreational facilities.
Costain’s responsibilities include conducting clay compaction trials to evaluate ground conditions at the designated site. These trials will involve constructing three test embankments on Thames Water-owned land, each 50 metres long, 20 metres wide, and up to 3 metres high. Geologists will then analyze the performance of Kimmeridge clay under various compaction scenarios, informing the reservoir’s final embankment design and construction methodology.
In addition to these trials, Costain has provided constructability advice to support Thames Water’s design proposals for the reservoir. This includes recommendations on key project elements such as embankment structures, tunnelling, and integrating a rail siding from the nearby Great Western Mainline. Costain will also ensure that safety, health, environment, and quality (SHEQ) standards are met, while acting as a logistical hub for all ground and environmental investigations, including archaeological assessments.
The clay compaction trials are scheduled to begin this summer and are expected to last six to twelve months, depending on weather conditions. Upon completion, all land used for the trials will be restored to its original state.