History repeats itself beneath the Thames
24 August 2021Tunnelling history came full circle recently during the excavation of Tideway, London’s ‘super sewer’, when TBM Selina passed under Brunel’s 19th century Thames Tunnel – the world’s first shield-driven tunnel and the first major underwater tunnel.
The ‘intersection’ occurred beneath the River Thames, near Wapping, in East London as TBM Selina excavates the final 5.5km stretch of the Tideway tunnel between Chambers Wharf and Abbey Mills Pumping Station.
The landmark Thames Tunnel was constructed between 1825 and 1843 and was the brainchild of Marc Brunel. It gave him the opportunity to try his recently patented cast-iron tunnelling shield which supported the ground and allowed miners to work safely in separate compartments.
Although the 396m-long tunnel’s construction suffered a series of catastrophic mid-river inundations between 1827 and 1838, there have thankfully been no such incidents during the construction of Tideway.
At the start of 2021, Selina – an 8.85m-diameter Herrenknecht mixshield machine – was lowered more than 60m below ground and is tunnelling Tideway’s deepest section on a slight decline toward the pumping station at Abbey Mills. It is expected to hole through soon around 70m below ground.
Running mostly under the river at depths of 30-70m, Tideway is designed to transfer sewage eastwards under gravity, intercepting the roughly 39 million tonnes of raw sewage overflows estimated to enter the river every year. Expected to cost around US$5.5bn, the project should be completed in 2025.
