More than two billion litres of raw sewage were dumped in the River Thames in just two days, according to a report.
Thames Water, which runs the Modgen water treatment works in Isleworth, admitted that an “unacceptable” amount of sewage had flowed into the river during a 48-hour period in October 2020.
The findings come as part of a report published by Parliament’s Environmental Audit Committee (EAC) on the quality of water in the UK’s rivers.
It claims that enough sewage was discharged from the Mogden plant to fill 400 Olympic-sized swimming pools. Mogden is the third largest sewage treatment facility in the UK.
Writing in the report, Thames Water’s chief executive Sarah Bentley claimed that torrential rain brought by Storm Alex on October 3 and 4 had left the company “struggling to treat the sewage”.
She added: "We would have needed either another treatment works the same size as Mogden treating another one billion litres or we would have needed 150 more storm tanks.”
In total, the Mogden facility poured 3 billion litres of untreated sewage into the Thames in 2020 – a rise of 600 per cent from 2016.
Spillages into rivers are legal when sewage facilities are likely to become overwhelmed. The release prevents sewage from spilling out of toilets and manholes in gardens and streets.
Councillor Salman Shaheen, who represents the ward of Isleworth for Hounslow Council, said locals had been left furious by the findings in the report.
Cllr Shaheen said: “People are very angry. They are outraged to hear about it because their kids are paddling in the Thames.
“It really is a treasured resource we have in our part of West London and it is being polluted by a water company.
“Mogden needs to upgrade their facilities. They must increase its storm tank capacity to prevent spillages into the Thames. It can’t be allowed to continue at this level.”
Labour MP for Brentford and Isleworth Ruth Cadbury said: “I’ve supported residents in their campaigns for urgent and sustained action, including calling for Thames Water to expand their capacity and address the crisis of sewage and flood water overwhelming the Mogden and their other sewage treatment works.
“Only then can they reduce the need to pump sewage into the Thames."
A spokesperson for Thames Water said: “We regard all discharges of untreated sewage as unacceptable and will work with the government, Ofwat and the Environment Agency to accelerate work to stop them being necessary.
“Our aim will always be to try and do the right thing for our rivers and for the communities who love and value them. We have a long way to go – and we certainly can’t do it on our own – but the ambition is clear.”
