Thames Water’s worst offending ‘illegal sewage spill site’

Peter Hammond, who featured in the Channel 4 docuseries Dirty Business, found that the South Moreton sewage treatment works site between Wallingford and Didcot was the worst.

The professor’s findings, which he says is based on Thames Water’s own data, uncovered 287 “illegal spills” between 2021 and 2025, more than any other site within the utility’s network.

The second worst was also in Oxfordshire, with the Faringdon site recording 271 “illegal spills”.

Oxford’s sewage treatment site was also in the top 10 with 167 “illegal spills”.

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Mr Hammond said in his findings: “South Moreton sewage treatment works has been included in both Environment Agency enforcement considerations and Ofwat’s recently announced fines for illegal discharges of untreated sewage.

“In the first half of 2021, the works discharged untreated sewage almost continuously for five months.”

By 2025, it’s claimed that 61 per cent of all spills at South Moreton were “illegal” at 79. There were also 2,700 spill hours recorded.

Local Greg Knowlson, who lives next to the site, said there used to be otters five years ago downstream at Mill Brook, which South Moreton discharges into.

But that isn’t the case anymore, he told the BBC, saying fish have disappeared from the water too.

“We think it is something to do with the sewage plant – it’s disgusting, really,” he said.

A Thames Water spokesman said: “We have not validated Professor Hammond’s report, so we are unable to comment on the stated conclusions.

“Taking action to improve the health of our rivers remains a key focus for us and over the next five years, we are delivering the most significant upgrade to our wastewater network in 150 years. This includes increasing treatment capacity, reducing storm discharges and introducing new nutrient-reduction schemes.

“The first half of this financial year has been marked by solid progress across all areas of our operational transformation. Our half‑year results showed a 20% reduction in pollutions, reflecting the impact of our focused improvement programmes.

“We are always committed to seeing waterways thrive, but we can’t do it alone. Farming, industry, road runoff, wildlife, and increasingly extreme weather also play a role in river health. We will continue to work closely with the Environment Agency and local partners to understand where improvements to our assets might be further required in future, so that communities can continue to enjoy their rivers.”