Costain embarks on an ambitious project to support Thames Water with the design of a new reservoir in Oxfordshire.
- The South East Strategic Reservoir, also known as the Abingdon reservoir, is set to enhance water supply for millions in London and the Thames Valley.
- Clay compaction trials are essential to determine the suitability of the site for the reservoir’s construction.
- Geological and archaeological evaluations will inform the reservoir’s design and construction methodologies.
- The project’s timeline outlines construction beginning in 2029, with completion aimed for 2037.
Costain has been tasked by Thames Water to provide critical constructability advice and conduct clay compaction trials for a new reservoir in Oxfordshire. Known as the South East Strategic Reservoir Option (SESRO), or simply the Abingdon reservoir, this ambitious 150 million cubic metre project aims to enhance the water supply resilience for customers across London and the Thames Valley, as well as those relying on Affinity Water and Southern Water.
The trials will involve constructing three test embankments within the proposed reservoir site, utilising similar methodologies and machinery planned for the actual construction. Each test embankment will be approximately 50 metres long, 20 metres wide, and up to 3 metres high. This detailed approach will enable geologists to assess the performance of the Kimmeridge clay under various compaction conditions, ultimately impacting the design and methodology of the reservoir’s construction.
The main structural elements of the reservoir embankments will reach heights of 15 to 25 metres and will incorporate bedrock clays excavated from the site. These excavations will create the reservoir basin, ensuring a watertight base. The expertise of Costain in providing constructability advice covers intricate details relating to the design, construction, sequencing, and essential project components such as embankments, tunnelling, and a rail siding from the nearby Great Western Mainline.
Additionally, Costain will assume responsibility for safety, health, environment, and quality assurance, alongside logistical management of ground and environmental investigations, which include archaeological assessments. The clay compaction trials are scheduled to commence in the summer and may span six to twelve months, contingent on weather conditions, before returning the land to its original state post-trials.
The environmental surveys have already begun following the approval of these trials, with extensive public consultations initiated in early June to refine the design through community input. A statutory consultation is foreseen for the summer to autumn of 2025, prior to the submission of a Development Consent Order application in autumn 2026. Thames Water anticipates approval by 2028, leading up to construction from 2029 to 2037, and the reservoir becoming operational by 2040.
The Oxfordshire reservoir project exemplifies forward thinking in infrastructure, crucial for future water security.
