Year
2024Duration
8 yearsCost
£5bnLocation
United KingdomProject achievements
Connected communities
Potential to closely link previously widespread inhabitants.
Solved the problem
Stop heavy rainfall causing sewage to overflow into the Thames.
Used engineering skill
Designed and built tunnel system to carry overflow away from London.
Increase the ability for London to deal with its own sewage
London’s sewage system was designed in the 1860s for a city of around 4 million.
There are now around 8 million people living in the capital.
Although the system still works well, it’s struggling to cope in terms of capacity.
The result is that millions of tonnes of sewage pour into the river Thames every year.
The Thames Tideway Tunnel is part of a 3-stage project to cut river pollution and clean up the Thames.
Stage 1 upgraded the main sewage treatment works in London – plants including Mogden, Crossness and Beckton can now treat more sewage every year.
Stage 2 built the Lee Tunnel. Operational since 2015, the 6.9km tunnel reduces sewage overflowing into the river Lee.
Stage 3 is the Thames Tideway Tunnel. The 25km tunnel stretches from Acton in west London to Abbey Mills pumping station in Newham in east London, where it will connect to the Lee Tunnel.
Tideway will connect with 34 of the most polluting overflow points along the river - collecting sewage that currently overflows into the Thames and transfer it to Beckton for treatment.
Did you know …
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The Thames Tideway Tunnel is the UK water industry’s biggest-ever infrastructure project.
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Engineers used six tunnel boring machine (TBMs) to dig the tunnel. Each TBM weighed 1,350 tonnes and was 147m long – the same length as 12.5 double decker buses. The first TBM arrived in November 2017 and is called Rachel after engineer Rachel Parsons, who started the UK’s first, women-only engineering company.
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The project created three acres of public space along the Thames – including at Blackfriars (near the City) and Victoria Embankment (near Downing Street). All the new spaces aim to let people get closer to the river.
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To celebrate the end of the tunnelling, in April 2022 London-based composer and cellist Rob Lewis performed live 70 metres underground from the Thames Tideway Tunnel.
Difference the project will make
The Tideway Tunnel – nicknamed the super sewer – aims to make the river Thames cleaner for both Londoners and river wildlife.
Currently, even a moderate amount of rainfall can mean sewage and other social excreta overflows into the Thames and floats past the House of Commons.
High levels of sewage also affects wildlife.
When a large amount overflows into the river, the bacteria that breaks it down sucks oxygen out of the water – suffocating and killing fish.
When the tunnel is finished, the system should only overflow in severe weather conditions, such as three days of solid rain.
How the work is being done
The Thames Tideway Tunnel is 25km long, 66m deep and 7m in diameter.
It follows the route of the river Thames and goes through ground conditions including chalk and clay.
Engineers used three main ‘drive sites’. This is where the tunnel boring machines (TBMs) were lowered into the ground via vertical shafts. They dug the tunnel in three sections – east, central and west.
Each TBM uses a rotating cutterhead to dig. At the same time, the machine creates a tunnel wall behind it using concrete segments.
Waste material was removed using a conveyor belt or pump, depending on the ground.
In some areas the waste is solid, in others it will be more liquid – known as slurry.
The TBMs were transported along the river by barge to where they were needed.
The first TBM arrived in November 2017.
Tunnelling started in 2018 and went on for 24 hours a day for four years to 2022.
Construction of Thames Tideway was completed in 2024. It's expected to be fully operational in 2025.
People who made it happen
The tunnel is being built by three different consortia.
- West section (Acton to Fulham): Balfour Beatty, Morgan Sindall and BAM Nuttall
- Central section (Fulham to Bermondsey): Ferrovial and Laing O’Rourke
- East section (Bermondsey to Newham): Costain, Vinci Construction and Bachy Soletanche
