Three bidders shortlisted for £5.7bn Thames Water reservoir main works contract

Thames Water is procuring the main works contract for the proposed White Horse Reservoir near Abingdon in Oxfordshire. The contract is reported at £5.7bn. The source for this page is a Construction News article reporting a Thames Water announcement, not an official notice, so no notice text or tender documents were available. The reservoir would supply customers of Thames Water, Affinity Water and Southern Water and is intended to support water supplies for 15 million people across the South East. Thames Water expects it to take about a decade to build and two winters to fill, with water available from 2040. No lots are mentioned.

The winning consortium will design, build, test and commission the reservoir. Work includes excavation, embankment construction and pipeline installation. Plans also include 500 hectares of habitat and wildlife areas and recreational lakes for activities such as kayaking, sailing and paddling. Costain has already carried out clay investigations at the site. Thames Water expects construction to create more than 1,000 jobs, including geotechnical engineers, archaeologists, ecologists and landscape architects.

Procurement began in January 2026. Candidates were assessed on previous experience, including their ability to carry out tunnelling and mass earthworks, and on their financial standing. Three consortia have now been shortlisted and invited to tender, so the competition is closed to new entrants. The procurement is subject to governance checks under the Procurement Act 2023 and is overseen by the water regulator Ofwat. The source does not state the procedure type, contract duration or options.

The shortlisted consortia are due to submit bids in spring 2027, and Thames Water expects to award the contract in autumn 2027. No exact submission date, Q&A deadline or submission method is given. Separately, Thames Water plans to appoint an infrastructure provider in 2029 through a competitive process. That provider will finance the scheme and deliver it alongside the main works contractor, using the same semi-private model as the Thames Tideway Tunnel.