Cassington sewage treatment works, the closest treatment works upstream of wild swimming spot Port Meadow, have been referred to the Environment Agency for investigations.
Researchers from the Oxford Rivers Project submitted their data to the EA after finding that, in 2021, the works had spilled when rainfall was as low as 1mm, and sometimes before any rainfall had occurred.
Further analysis indicated that raw sewage was being discharged into the Thames even when the works was operating below full capacity.
It is currently legal for water companies to discharge raw, untreated sewage into rivers in times of ‘exceptionally heavy rainfall’. Water companies must monitor their overflows and provide data on spills of untreated sewage each year.
READ ALSO: Wild swimmers protest after delay in notification leaves them 'swimming in raw sewage'
It comes as a protest against sewage dumping is set to take place at Port Meadow this weekend.
Oxford MP Layla Moran, who has called on the Government to take action to clean up the Thames in a Westminster Hall debate she secured in November, intends to join it.
Tim Harris, the principal researcher on the Oxford Rivers Project, said: “We first thought something could be wrong when Cassington showed no spills at all on Thames Water’s alerts system since March 2021, despite spilling throughout the year in 2019 and 2020.
“Then, on questioning officers at Thames Water, they stated that the capacity of the works had increased 20 per cent in 2021, an unusually large amount, and despite no investment at the works. This prompted us to look more closely at the data and then submit it to the Environment Agency for investigation.”
Oxford City Council has submitted an application to DEFRA to grant Bathing Water status at Wolvercote stream, and Fiddlers Island near Port Meadow and are awaiting a response.
The application was made on behalf of the Oxford Rivers Project – a programme jointly funded by Thames21, Thames Water, Oxford City Council, and the Rivers Trust – which supports volunteers to collect data on water quality and different river user groups.
READ ALSO: Witney MP accuses Thames Water of using sewage releases as 'a routine process'
Claire Robertson, the Oxford Rivers Project Officer, said: “In our view, it’s totally unacceptable that raw sewage ever goes into our beautiful rivers, but to find out this might be happening illegally, before we’ve even had any heavy rain is even more shocking.”
A Thames Water spokesperson said: “The decision by Ofwat and the Environment Agency to look in to sewage discharges across rivers and other watercourses has rightly brought this issue to the fore. 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.
“We have an unprecedented amount of investment directed towards safeguarding our rivers and streams. Between 2020 and 2025 we are spending £1.25 billion on maintaining and improving our operational sites, including contributing to the health of 745km of rivers across London and the Thames Valley.
“Our aim will always be to try and do the right thing for our rivers and for the communities who love and value them.
READ ALSO: Thames Water criticised after Witney sewage release leads to cancelled Boxing Day swim
"We have a long way to go – and we certainly can’t do it on our own – but the ambition is clear.”
The Environment Agency said they would not hesitate to pursue water companies where there is evidence of non-compliance and take appropriate action – and had concluded seven prosecutions against water and sewerage companies in 2021.
In a statement the EA said: “Sewage pollution can be devastating to human health, local biodiversity and our environment. Water companies, regulators, farmers and others must do more to tackle this.
“To date, 1,300 storm overflows and storm tanks at waste water treatment works have been identified as spilling frequently, and prioritised for further scrutiny following our review of data from over 12,000 sites. Our separate, major investigation into possible unauthorised spills at thousands of sewage treatment works is ongoing.”
Protest starts at 11.30am on Sunday January 23. Meet at the car park in Lower Wolvercote for protest on Port Meadow near the weir.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here