E.coli levels six times higher than acceptable have been detected in the River Ver.
The worrying revelation comes after research carried out by intrepid volunteers from the Ver Valley Society.
They collected samples that have been tested by scientists from Brunel University in London.
The beleaguered river has had a difficult few years, with raw sewage being repeatedly dumped into the rare chalk stream, one of only around 200 in the world.
Since March, sewage has been pumped into The Ver seemingly nonstop, with the amount recently surpassing 2,400 hours worth.
The volunteers found around 3,000 E.Coli colonies per 100ml of water in the beloved chalk stream. The accepted threshold is 500 colonies.
Ver Valley Society chair John Pritchard said: "It's extremely frustrating that the sewage has been pouring in for several months now and there isn't really an immediate solution.
"It's a habitat that's very special to the community and these spillages encourage the wrong kind sort of plants and can be detrimental to human health."
Recently, a road in Flamstead, River Hill, was flooded with contaminated water and motorists drove through it, in some cases spraying water over neighbouring hedges.
The UK is currently facing a national E.Coli crisis, with The UK Health Security Agency confirming yesterday (June 27) that one person has sadly died after being infected with the bacteria.
Read more:
• St Albans campaigners take part in 'Restore Nature Now' march
• Steve Coogan visits St Albans and takes trip to River Ver
• General Election candidates respond to sewage in River Ver
These latest developments come as part of an ongoing row over the fate of the Ver.
Last weekend protestors from across the city took part in a demonstration in London to call on the next government to protect the Ver, as well as England's other rivers and streams.
The Environment Agency is currently undergoing an investigation, while Thames Water is yet to implement its Groundwater Impacted System Management Plan, with work delayed until 2025.
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