The utility giant has issued a formal tender for the tunnelling and connection works after a year of market engagement.

The twin-tunnel scheme forms a central part of its long-term Water Resource Management Plan, approved by government and backed by Ofwat for the AMP8 control period.

The tunnelling and connection works are being tendered as a two-stage NEC4 contract with up to four bidders due to be shortlisted for final bids.

Works include:

• A 4.2km tunnelled conveyance route using a 3.5m diameter TBM from Mogden Sewage Treatment Works to a new discharge point on the Thames upstream of Teddington Weir

• A 150m pipe-jacked 2.2m diameter water transfer pipe from a new abstraction point to the existing Thames Lee Tunnel, linking with East London’s reservoir system

• Four access shafts will also be constructed as part of the tunnel works.

Head of procurement and supply chain Mohit Farmah said: “We’re seeking industry leading tunnelling experts to help us deliver this nationally significant infrastructure project.

“This scheme will be vital as we respond to the challenges of climate change and population growth.”

Construction is expected to start in 2029 subject to planning approval. The tunnels will enable recycled water to be released upstream to compensate for drought-time abstraction, protecting wildlife and river health while bolstering supplies.

Interested firms can register to access tender documents (click here).

The nationally significant project will provide up to 75 million litres of water per day during drought, supported by water recycling from Mogden sewage treatment works. Thames Water forecasts a daily water shortfall of 1 billion litres by 2050 unless action is taken.