• More than 20 million tonnes captured by super sewer network to date
• Tideway confirms bills remain within original £20-£25 per year cost estimate
• Tunnel operating at full capacity, with 12 of 13 public spaces now open

Tideway, the company behind London’s super sewer, has published its latest Annual Report and Accounts, marking a significant year in which the Thames Tideway Tunnel began operating at full capacity and continued protecting the River Thames from sewage pollution.

Since the first connection was made in August 2024, the 25km tunnel system has intercepted more than 20 million tonnes of storm sewage that would otherwise have entered the river.

Designed to protect the Thames for at least 120 years, the system adds more than a billion-and-a-half litres of storage capacity to London’s Victorian sewer network.

The report outlines a pivotal year of transition for the company, as the project moved from large-scale construction into long-term operational management and commissioning.

While the majority of civil engineering work is now complete, work continues to optimise and test the system under a range of storm conditions to ensure long-term reliability and performance.

The report confirms that the cost to Thames Water bill-payers remains within the £20-£25 range outlined at the outset of the project (2014/15 prices).

The report also highlights the scale of the programme’s wider legacy, including the creation of 13 new public spaces along the River Thames and new areas of habitat.

During the year, the company also welcomed Her Royal Highness The Princess Royal to mark the completion of works at Bazalgette Embankment, Tideway’s newest public space, following a successful visit from His Majesty The King earlier in the year.

Michael Queen, Tideway Chair, said: “The Thames Tideway Tunnel project has reached a hugely significant milestone, with the system now operating at full capacity and already preventing millions of tonnes of sewage from entering the River Thames.

“These achievements reflect the work of thousands of people who have contributed to delivering a complex, nationally significant project largely on time and on budget."

The report is the first introduced by Tideway’s new Chief Executive Officer, Matt Parr, who succeeded Andy Mitchell in May 2026 following more than a decade leading the project.

Matt Parr, Chief Executive Officer of Tideway, said: “We are proud of what has been achieved so far – not only in helping protect the Thames from sewage pollution, but in the wider legacy created through skills, public spaces, environmental improvements and investment across London.

“This year represents an important transition point for Tideway, as we move from construction to long-term operation. Our focus remains on safely completing the remaining work, ensuring the tunnel performs reliably, and on continuing to protect the River Thames for generations to come.”