Charlotte makes breakthrough for London’s super sewer

Engineers building a 25km super sewer in London have reached a significant milestone after one of the project’s giant tunnelling machines broke through the ground to complete a section of tunnel.

Named after suffragist Charlotte Despard, the tunnel boring machine (TBM) is excavating the Frogmore Connection Tunnel from Wandsworth to Fulham as part of the Thames Tideway Tunnel project to protect the River Thames from sewage pollution.

The 1.1km tunnel will take sewage overflows from King George’s Park into the main 25km super sewer at Fulham, where it will be transferred to east London for treatment.

The 500m southern section of the Frogmore Connection Tunnel, from Dormay Street to King George’s Park, is now complete. Charlotte will now be lifted from the shaft, taken back to Dormay Street and placed back into the ground to tunnel 600m north to Fulham.

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The west section of the project is being delivered by a consortium of BAM Nuttall, Morgan Sindall and Balfour Beatty. In a statement, Sally Cox, project director for the west section, said: “This breakthrough, the first on the Tideway project, marks another key step toward a cleaner, healthier River Thames.

“Despite being the smallest TBM on the Tideway project, Charlotte is creating vital infrastructure that will benefit Londoners and their river for many years to come.

“Our tunnelling team has done a fantastic job getting this machine to King George’s Park and will now focus on completing the northern section of the Frogmore Connection Tunnel.”

super sewer
Charlotte makes a breakthrough for the Thames Tideway Tunnel project (Image: Tideway)

Charlotte is 3m wide and over 70m long, while the Frogmore Connection Tunnel is being created at a depth of around 30 metres. The refurbished TBM had previously worked on a water ring-main project in north London.

The Tideway team added that the first section of the main tunnel is also close to completion, as tunnelling machine Millicent approaches Fulham after tunnelling almost 5km from Battersea. To date, 8km of the Thames Tideway Tunnel has been built, with four tunnelling machines in the ground. Once complete in 2024, the super sewer is expected to stop tens of millions of tonnes of raw sewage pouring into the river every year.