London is getting a new super sewer, but water bosses say the pipe would need to double in size to stop waste spilling into the Thames.

Tideway is upgrading London's sewer system to cope with the capital's growing population, with the so-called "super sewer" designed to be the width of three double decker buses.

Over 400 people are working on the tunnel across 24 project sites, four of which are in the borough of Wandsworth.

But Sarah Bentley, the CEO of Thames Water, said the company's performance was "unacceptable" as it continues to dump sewage into the Thames every year.

Ms Bentley said in Parliament's Environmental Audit Committee on Wednesday October 13: "When we get inundated with rain up to 39 million tonnes of rainwater then gets contaminated with sewage and gets discharged into the Thames, which is clearly unacceptable.

"The Thames Tideway tunnel will eliminate the vast majority of that. Clearly with incredibly extreme weather events that are increasing, we need to now look at that before that comes into operation over the next two and a half years.

"When the original analysis was done 15 to 20 years ago, we'd have needed a tunnel twice as big."

The 25km Thames Tideway Tunnel will intercept, store and transfer sewage away from the River Thames, with tunnels around 25m under the river.

Tideway said: "London relies on a 150-year-old sewer system built for a population less than half its current size.

"As a result, millions of tonnes of raw sewage spills, untreated, into the River Thames each year. The super sewer is the solution to tackle these problems."

It added: "We're building a 25km super sewer under the Thames to intercept those nasty spills and clean up our river for the good of the city, its wildlife and you."

This tunnel will connect 34 of the most polluting combined sewer overflows (CSOs).

The cost of the project is being paid for by Thames Water's 15 million waste water customers through their bills, which will rise by no more than £25 per year, says Tideway.

Bazalgette Tunnel Limited (BTL) is the licensed infrastructure provider for its finance, building, maintenance and operation.

Plans were approved back in 2014 with construction starting in 2016.

It is hoped the tunnel will be completed in 2023 with all works finished by 2025.

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