Thames Water has announced today that four bidders are in the running to construct the Lee Tunnel - the first of two major infrastructure projects that make up Thames Water's proposed London Tideway Tunnels.

The bidders are:

• FCC
• Laing O'Rourke / Impregilo Joint Venture
• Morgan Est / Vinci / Bachy Joint Venture
• Murphy / Hochtief Joint Venture

The contract involves constructing a seven-kilometre (4.3 miles) tunnel from Abbey Mills pumping station in Stratford, east London, to Beckton Sewage Treatment Works. The value of the contract will be in excess of £400million - the largest ever single contract let by Thames Water. Pending planning and other approvals, construction of the Lee Tunnel is due to begin later this year and be completed in 2014.

Phil Stride, Head of London Tideway Tunnels at Thames Water, said:

"Currently, 32 million cubic metres of storm sewage overflows from London's Victorian sewers into the River Thames and its tributary, the River Lee, each year. This untreated sewage discharges into the river on average more than once a week. The Lee Tunnel will substantially reduce the overflows by capturing and transferring them to Beckton for treatment.

"Together with the proposed Thames Tunnel, the Lee Tunnel will provide London with a 21st Century sewage system and help make the River Thames cleaner and healthier for people and wildlife. We will now go through a vigorous assessment programme to shortlist bidders to construct the Lee Tunnel and pending planning approval, we hope to award contracts later this year."

Planning applications for the Lee Tunnel, including an extension of Beckton Sewage Treatment Works to increase its treatment capacity, were submitted to the London Borough of Newham, the London Thames Gateway Development Corporation and the Olympic Delivery Authority in May 2008.