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Thames Tideway Tunnel

As the UK’s largest water supplier, it’s our responsibility to protect our major water source, the River Thames. We’re doing this by working hard to improve the water and sewer networks across London and the Thames Valley to make sure they can cope with current and future demands. One of the ways we’re looking to protect the river is by improving the current sewage pipe network while promoting a healthy river environment, by building the Thames Tideway Tunnel, also known as the ‘Super Sewer’.

This is a 15-mile-long sewer, the width of three London buses, which is being bored under the River Thames. The new tunnel will pipe sewage to our Beckton works. After that, we’ll return clean water to the environment – and use the sewage waste to generate more renewable energy too.

Photograph of workers in a tunnel

Who is building the Thames Tideway Tunnel?

Most of the engineering work is being carried out by a company called Tideway. They started in 2016 and will finish construction by 2024, when they'll hand it over for Thames Water to operate and manage. The tunnel will mainly follow the course of the Thames through London, so it can intercept sewage from the ‘combined sewer overflows’ which are currently polluting the river.

There are three main 'drive sites' at Fulham, Battersea and Bermondsey, with a number of other smaller sites where work will also take place.

Why we need the Thames Tideway Tunnel

The tunnel will intercept at least 94% of the millions of tonnes of sewage overflowing into the tidal Thames every year from the capital’s overloaded Victorian sewer system. It will also capture all of the ‘first flush’ from the sewers after heavy rain. This contains all the sediment that's built up during periods of drier weather and causes the most damage. Instead of over 50 sewage spills a year, there will only be three or four - mostly surface water runoff after heavy storms.

What the Thames Tideway Tunnel will mean to everyone

The Thames Tideway Tunnel will collect sewage before it enters the river and ensure it's properly treated, cleaning up the river for London, its inhabitants and its wildlife and allowing the city to sustain a rich, diverse ecology.

Tideway will greatly reduce the quantity of sewage-related litter in the Thames and, in turn, the amount ingested by wildlife. Over the last 30 years, we've seen a dramatic clean-up of the Thames, making it a prime example of a recovering ecosystem. But the millions of tonnes of raw sewage that still overspills into the river each year represents its last major source of pollution. The visual appearance of the river will improve, and our new structures within it will provide new habitats for aquatic wildlife.

Learn more about the benefits of the Thames Tideway Tunnel.

Who will pay for the Thames Tideway Tunnel?

The tunnel will cost £3.8bn to complete, and an additional £1.1bn has already been spent by Thames Water for preparatory works. The cost of the project is being paid for by Thames Water’s 15 million wastewater customers through their bills.

We'll continue to work as efficiently as we can, keeping our customers’ wastewater bills as low as possible. Spreading the costs of a big investment project like the Thames Tideway Tunnel is widely seen as a fair approach and is standard practice.

If you’d like to learn more about what we’re doing to improve our network, waterways and ultimately our environment for all of our customers and future generations, check out our other investment projects.