A newly available Environment Agency (EA) inspection report has found Thames Water's Hogsmill Sewage Treatment Works are in breach of its environmental permit on four counts, including a "significant impact" from non-compliance over inadequate storm sewage storage — just a few weeks after the stretch of the Thames at Ham and Kingston was designated London's first new official bathing site.

Save Our Lands and River (SOLAR), a campaign group challenging Thames Water's proposed Teddington Direct River Abstraction (TDRA) scheme, is calling on people to sign a government petition demanding tougher standards for sewage infrastructure.

SOLAR's petition "Ensure new sewage treatment infrastructure meets higher standards as in the EU" has already passed 38,000 signatures and needs 100,000 to be considered for a Parliamentary debate.

An inspection of The EA's Compliance Assessment Report on 11 May 2026 records four non-compliances at Hogsmill Sewage Treatment Works, which treats wastewater from the Kingston, Surbiton and surrounding catchment.

These include:

Storm storage shortfall (rated "significant impact"): The site's storm tanks hold significantly less than the 31,182m³ of offline storage required under its permit. The EA found this shortfall is "expected to significantly increase frequency and duration of storm discharges from the site." which results in sewage being allowed to enter directly into the Thames in Kingston.

Overdue improvement works: A scheme to expand storm tank capacity was originally due to complete in March 2025. Thames Water has now told the EA it doesn't expect to finish until 2028 — three years late.

Failed flow monitoring ("minor impact"): Equipment used to measure flow passed forward to treatment failed its MCERTS certification, after officers found return liquors were being double-counted — undermining confidence that storm discharges are only happening when they're supposed to.

Uncontrolled discharge during storms: Because of how site drainage is routed, the EA found that unprocessed "site returns" are discharged to the environment during storm events via the site's permitted storm outlet — itself a separate breach, since the site is only licensed to discharge settled storm sewage there. The Agency's own spill-monitoring data, included in the report, shows the site has recorded storm discharges every year since at least 2021, including 33 spills totalling 186.75 hours in 2023.

The EA's stated enforcement response is "Investigation," with the Agency saying it "will now consider what enforcement action is appropriate."

Hogsmill STW sits approximately 5k upstream of the River Thames stretch at Ham and Kingston, which the Government designated London's first official bathing water site on the Thames on 15 May 2026 — four days after this inspection took place - where Thames water propose to build the Teddington Direct River Abstracted facilities.

SOLAR campaigners are petitioning for better standards snd its government petition calling for better standards for new and upgraded sewage infrastructure now has over 38000 signatures.

Additionally, campaigners argue that the failings identified at the Hogsmill are linked.

For example, the storm tank upgrade that would have brought Hogsmill's storage up to permitted levels was due to complete over a year ago, and will not now be finished until 2028.

That scheme exists precisely because current infrastructure at the site cannot cope with the flows the catchment now produces.

SOLAR Co-Founder Ian McNuff said: "This report shows exactly the kind of infrastructure gap the petition is about.

"Hogsmill's upgrade to fix this has already slipped by years, on a site just upstream of a part of the river that has mass watersports and general recreational use and more recently became London's first official bathing site on the Thames.

"We need higher standards for this infrastructure as they now have in Europe. Every signature on this petition adds pressure on the government to act in the best interests of people's health and to protect our natural waters."

SOLAR's petition already has 38,718 signatures out of 100,00.

It can be signed here.

Nub News has contacted Thames Water for statement.

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