Tunnel boring of the final 7.6 km (4.7 miles) central section of the main tunnel of the Tideway Project in London, England was completed on Nov. 30 with the tunnel boring machine (Ursula) broke through on the Battersea to Bermondsey Drive at the deep shaft at Tideway’s Chambers Wharf site.

The drive is part of the 25 km (15.5 mile) £4.2bn Thames Tideway Tunnel (as the super sewer is formally known) project. With the completion of the drive TBMs working on the project have now successfully passed beneath 21 Thames crossings, including Tower, Waterloo and Westminster bridges and 19 km (11.8 miles) of tunnel boring has been completed.

Mark Sneesby, Tideway’s Chief Operating Officer, said: “This is an important day for everyone on the Tideway project, as well as for Londoners and the River Thames.

“With around four fifths of the tunneling now complete, everyone on Tideway is focused on getting this job done safely and delivering a cleaner Thames for the city.”

London News Online reported that the work on the remaining 5.5 km (3.4 mile) section due to begin very soon.

Viv Jones, Project Director for the central section, said: “The hard work from our teams on site and below ground has enabled us to safely continue tunneling despite COVID – and continue work on this vital piece of infrastructure.

“Ferrovial and Laing O’Rourke, the contractors on the central section, have done a fantastic job, and I thank the teams involved for their efforts to clean up London’s iconic river.”

As part of its drive, TBM Ursula excavated more than a 1 Mt (1.1 million st) of spoil, all of which was removed from site using barges on the Thames – preventing more than 250,000 HGV trips.

Around 240 barges were also used to transport concrete segments to site. These segments slot together underground to form the rings which make up the tunnel. This section of tunnel is formed of 4,227 rings.

Tim Newman, Tideway’s Project Geologist, added: “Completing the longest single drive on the Tideway project is a wonderful milestone, and our teams have made great progress through a challenging year.

“TBM Ursula has tunneled at incredible depths, encountering a real mix of geology – through clay, sand, gravel and chalk. The expertise required for such a task is immense and allowed us to quickly and safely adapt the tools on the cutterhead as needed.”

TBM Ursula will remain in place at the bottom of the shaft while the team at Chambers Wharf prepares to launch TBM Selina, which will create the final and easternmost section of the super sewer.