Thames Water has been fined £4 million after it allowed raw sewage to leak into two Oxford streams for more than 30 hours.
Up to 3,000 fish were killed by the discharge in July 2016, which ran for 3.5km, through a pub garden and past community allotments.
It is the third major fine for Thames Water this year, following prosecutions for two other incidents which also took place in 2016.
Thames Water was accused of failing to carry out essential maintenance in a sewer that was known to have problems with blockages.
The Environment Agency (EA) said the incident was “foreseeable and avoidable” but the company had relied on members of the public noticing the sewage leak because it had no system in place to identify it.
The leak was first noticed by canoeists who found themselves paddling in sewage amongst dead fish, the court heard, before they alerted the EA.
‘Suffering and gasping for oxygen’
Robert Davis, an attending Environment Agency senior officer, said: “It was quite horrific. Sewage pollution was bank to bank and there was a foul stench of raw sewage.
“When we traced the source, we found a waterfall of raw sewage discharging via a pipe into the streams.
“Amongst the dead fish, fisheries officers observed hundreds more on the surface, suffering and gasping for oxygen.”
It brings the total amount of fines levied against Thames Water since 2017 to £32.4 million for 11 cases.
It also follows the announcement by the EA of a major investigation into England’s water companies over apparent illegal levels of sewage being leaked into rivers from wastewater treatment plants.
Robert Davis added: “This fine sends out a clear warning to the boards of all water companies – invest heavily in maintaining your sewers and don’t drop the ball when it comes to carrying out that maintenance.
“Incidents like this are preventable and are completely unacceptable, particularly at a time when the need to protect the water environment for wildlife and people has never been greater and when public consciousness on environmental matters is so high.”
The EA called on members of the public to report suspected water pollution to its incident hotline.
