Thames Water has picked an Arup/Binnies joint venture to draw up the engineering designs for a new reservoir south of Oxford, near Abingdon.

Plans for the £1.5bn reservoir known as SESRO (South East Strategic Reservoir Option) would secure water supplies to 15 million customers in the Thames Water, Southern Water and Affinity Water catchments from 2040.  

Should Thames Water secure government approval for the reservoir, as part of its draft Water Resource Management Plan, Arup Binnies joint venture will play a crucial role preparing the Development Consent Order submission for the project in 2026.

If granted, construction is forecast to begin in 2029 with SESRO planned to begin operating in 2040.  

Separately, both Arup and Binnies have supported the design and construction of London’s Thames Tideway Tunnel and are playing a pivotal role in the design of the Fens and Lincs Reservoirs.  

Last month Thames Water was granted planning to build a trial compacted clay embankments at the site.

Contractors will excavate the clay and layer it into three mounds, each 50m long, 20m wide, and up to 2m high.

The programme of work will complement ground investigations that are already underway.

The results from the trial, which will take place over a 12-month period, will play a crucial role in informing the engineering design and embankment construction proposed for this vital new water supply.

Mohit Farmah, head of procurement at Thames Water said: “This supply chain of technical experts with global reach will ensure our reservoir proposals are not only compliant with the Planning Act 2008 but are also developed to a world-class standard. “