The first four of 21 sites have been switched on with the new tunnel starting to protect the River Thames from sewage pollution for the first time.

Valves, which operate like giant gates, are now open at four sites with the rest due to come online in the coming months when the sewer will reach full operating capacity next year.

In May 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 1.6m m3.

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.”

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.

While the testing phase is now underway, work continues above ground to finish the new riverside public spaces being created as part of the project.

The Tideway project is being delivered by an alliance of contractors. The west region is being delivered by a joint venture of BAM Nuttall, Morgan Sindall Infrastructure and Balfour Beatty. The central region is being delivered by a joint venture of Ferrovial Agroman UK and Laing O’Rourke. The east region is being delivered by a joint venture of Costain, Vinci Construction Grands Projets and Bachy Soletanche.

System integration is being delivered by Amey, which is responsible for providing process control, communication equipment and software systems for operation, maintenance and reporting across the Thames Tideway Tunnel system.