Thames Water is preparing to retender its £500m Teddington Direct River Abstraction (TDRA) project after changing its procurement strategy for the scheme’s main construction works.
The utility had initially planned to procure the principal tunnelling and water treatment elements separately, but has now decided to combine the major civils and tunnelling works with construction of the advanced water treatment facility at Mogden sewage treatment works under a single main contract.
Thames Water said adopting a single-contractor delivery model would reduce interfaces between separate work packages and provide greater control over the overall project.
As part of the change, the company has cancelled the £242m tunnelling competition launched in May last year. A new procurement process covering the enlarged package is expected to begin before the end of 2026.
Under the revised programme, Thames Water intends to submit its development consent order application in early 2027, with the main construction phase expected to begin in 2029 and run for approximately four years.
The nationally significant TDRA project forms part of Thames Water’s long-term Water Resources Management Plan and has received development funding through Ofwat’s AMP8 regulatory settlement.
The scheme will include a 4.2km tunnel, which will be constructed using a 3.5m-diameter tunnel boring machine running from Mogden to the River Thames upstream of Teddington Weir. Four shafts will also be constructed as part of the project.
The tunnel will enable heavily treated wastewater to be returned to the Thames, replacing some of the freshwater that would otherwise need to be abstracted from the river for London’s drinking water supplies.
A separate 150m-long, 2.2m-diameter pipe-jacked connection will transfer abstracted river water into the existing Thames Lee Tunnel. From there, the water will be transferred to the Lee Valley reservoirs in east London.
The project also includes a new tertiary treatment plant at Mogden sewage treatment works. During drought conditions, the facility will treat wastewater to a high standard before returning up to 75 million litres of water a day to the Thames.
The additional resource would allow Thames Water to maintain drinking water supplies while reducing the amount of freshwater abstracted from the river during periods of drought.
Thames Water forecasts that London could face a daily water deficit of around one billion litres by 2050 without additional measures to increase supply and improve resilience.
Myles Rawstron-Rudd, TDRA Project Development Manager, said: “As London experiences one of the hottest summers on record, it is vital that we plan ahead to protect our water security and ensure supplies are available when they are needed most.
“The Teddington Direct River Abstraction (TDRA) project is a critical drought resilience project for London and a key part of our long-term plan to secure water supplies for future generations.
“Following a period of public consultation, technical assessments and stakeholder feedback, a number of updates have been made to the project design. These changes have improved the scheme’s safety, viability and operability, whilst also reducing potential impacts on local communities and the surrounding environment.
“As a result of this work, we’ve now refined our procurement strategy and will deliver the project through a single construction package.
“This approach will provide greater certainty, stronger project controls and improved programme stability through the appointment of a single principal contractor. It will also deliver overall cost efficiencies for the project while maintaining the planned delivery programme. There will be no delays to the project because of this change in procurement approach.”
The revised procurement strategy means contractors will be expected to take responsibility for a broader range of the project’s construction activities under one main contract. The approach is intended to reduce the number of interfaces that Thames Water would otherwise have to manage between separately appointed tunnelling, civils and treatment contractors.
The TDRA project is one of the major infrastructure schemes being developed to address London’s long-term water supply requirements as climate change, population growth and periods of drought place increasing pressure on existing resources.
The scheme is designed to operate primarily during drought conditions rather than as a continuous addition to London’s water supply. By recycling highly treated wastewater through the River Thames and enabling river abstraction upstream of Teddington Weir, it is intended to increase the amount of water available to the wider supply system during periods when conventional abstraction is constrained.
The new procurement exercise will therefore be a significant milestone for the project. Thames Water expects to launch the tender for the combined construction package before the end of 2026, ahead of its planned development consent order submission in early 2027.
Subject to the consenting and procurement processes, construction is scheduled to begin in 2029, with the main works expected to take four years.
