Thames Tideway Tunnel turned on

Today (14 October), Tideway has formally declared London’s new super sewer open.

The first valves at four of a total 21 locations have been activated, with the benefits for water quality in the Thames already evident. Tideway said on 23 September, a heavy rain day, 589,000m³ of discharges were captured that would normally have entered the river.

This follows the completion of the build after eight years; in May 2024, the new 25km super sewer was connected to the 6.9km Lee Tunnel – completing the full ‘London Tideway Tunnel’ network, which has a combined capacity of 1.6 million m³ to protect the River Thames.

Teams are now working to bring the system into full operation, which is on track for 2025. This involves connecting the remaining discharge points and testing the entire system during different weather conditions, including heavy storms.

Once fully operational, Tideway anticipates that the super sewer will virtually eliminate the harmful effects of sewage pollution on the River Thames through central London.

Tideway chief executive Andy Mitchell said: “This is an important moment for the Thames… After eight years of construction, in which almost 25,000 people have contributed more than 40m working hours, this system is operating for the first time.

“These are early days, with more connections to make and further testing to come, but the super sewer’s positive influence on the health of the Thames will increase over the coming months – and London will soon be home to the cleaner, healthier river it deserves.”

Thames Water will operate the system once it is complete. Chris Weston, chief executive, said: “The Thames Tideway Tunnel, a £4.5bn investment made by our customers, is nearing completion. We are already seeing the benefits of our £700m investment in Lee Tunnel in 2016, and the Channelsea River and River Lea now have ‘good to excellent’ water quality as a result – showing how the Thames Tideway Tunnel is set to bring further improvements in central London.

“We have published plans to upgrade over 250 of our sewage treatment works. In London, we have started the £100m upgrade of Mogden sewage treatment works, and we’re also spending £145m upgrading Beckton sewage treatment works, which will increase capacity and reduce the number of storm discharges.”