Tideway central-section tunnelling completed3 December 2020
Tunnelling on the central and longest section of Tideway – London’s so-called ‘super sewer’ – has been completed following the holing through of TBM Ursula into a deep shaft at Chambers Wharf in south east London.
After its marathon 7.6km bore from Battersea to Bermondsey, the 8.8m-diameter NFM-made TBM has mined over a million tonnes of spoil which were removed from site by river barges, a process claimed to have eliminated more than 250,000 truck journeys. Transporting concrete segments to site was also undertaken using the river – around 240 barges plied the Thames ceaselessly to ensure Ursula was able to install 4,227 rings without interruption.
Mark Sneesby, Tideway Chief Operating Officer said: “This is an important day for everyone on the Tideway project, as well as for Londoners and the River Thames.”
Central Section Project Director Viv Jones added: “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.”
Tim Newman, Tideway’s Project Geologist said: “TBM Ursula has tunnelled 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.”
The TBM’s break through marks the completion of around four-fifths of the tunnelling which continued despite lockdown restrictions. The machine will remain at the bottom of the shaft while the team at Chambers Wharf prepares another TBM – Herrenknecht mixshield ‘Selina’ – for launch on Tideway’s final and easternmost 5.5km stretch to Abbey Mills Pumping Station where it is expected to break through 70m below ground.
Tideway runs mostly under the River Thames at depths of 30-70m, and will transfer sewage eastwards under gravity. The sewer, expected to cost around £4.1bn (US$5.47bn), is designed to intercept, store and ultimately prevent around 39 million tonnes of raw sewage entering the river annually through combined sewage overflows. Construction is scheduled for completion in 2025.