Gates open on London's new super sewer heralding new era for the Thames

London’s super sewer, designed to protect the River Thames from sewage pollution, has now been turned on.

BAM delivered the west section of the Tideway project, as part of a joint venture, working alongside Morgan Sindall Infrastructure and Balfour Beatty.

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

Data published by Tideway Ltd today shows that in one day alone when London saw heavy rainfall on 23 September 589,000 m3 was captured by the London Tideway Tunnel with just the first connections activated.

Valves, which operate like giant gates, are now open at 4 of the 21 locations that make up the system, with the rest due to come online in the coming months, when the sewer will reach full operating capacity.

Richard Prime, Managing Director – Major Projects, at BAM said: ‘We are proud to have worked collaboratively with our partners on the Tideway project, a modern engineering marvel that will protect the River Thames from pollution for generations to come. This project aligns perfectly with BAM's vision of building a sustainable tomorrow. As the tunnel begins operation, we reflect with immense pride on what our teams have achieved, contributing to a transformative scheme that will not only enhance biodiversity along the river but also help reconnect communities to the Thames, bringing people closer to the heart of London’s natural environment.’

Tideway CEO Andy Mitchell said: ‘This is an important moment for the Thames. The super sewer has been switched on and is starting to protect the river from sewage pollution. After eight years of construction, in which almost 25,000 people have contributed more than 40 million 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.’

Daniel Ibrahim-Webster, Senior Environmental and Sustainability Manager at BAM, worked on the project for eight years: “For years to come people will see the river becoming cleaner and more biodiverse and that’s all because of the Tideway project and the magnificent engineering that has been built below the ground here.  It’s all about making a cleaner River Thames possible for future generations, and to have played a part in that is fantastic.”

The new system will have a capacity equivalent to 640 Olympic-sized swimming pools.

Teams are now working to bring the system into full operation. This involves connecting the remaining discharge points to the new super sewer and testing the entire system during different weather conditions, including heavy storms.

The project is due to be fully up and running (with testing complete) in 2025. Thames Water will then operate the system, as part of its London wastewater network.