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Southern Water admits polluting sensitive stream

Environment Agency An Environment Agency picture of the River Test flowing through countryside, with the near side appearing brown and pollutedEnvironment Agency
The River Test became discoloured downstream from the waste treatment works

Southern Water has admitted causing a pollution incident which sent a dark plume of sewage four miles (6.5km) along a sensitive Hampshire chalk stream.

The Environment Agency (EA) said the company allowed "potent amounts of suspended solids and iron" into the River Test near Stockbridge in March 2023.

Southern Water pleaded guilty to two charges relating to environmental permit breaches at Medway Magistrates' Court.

The company said the incident "should not have occurred".

The EA said the pollution was discovered during routine water quality checking of the river when dark particles were found.

The plume was traced back to Southern Water's Fullerton wastewater treatments works.

Sampling confirmed the level of suspended solids in the water was more than triple the permitted limit, the EA said.

The amount of iron in the water, giving the pollution a red tinge, was also much higher than the allowed amount.

The firm failed to alert the agency when it became aware of the issue or about the failing equipment that caused it.

White clouds hang in a blue sky above a section of the River Test with green weeds in the clear water
The River Test is the longest chalk stream in the UK rising at Ashe near Basingstoke and flowing 40 miles to Southampton Water

Salmon born within the River Test chalk stream are genetically unique. They are more vulnerable and less resilient than other salmon and need clean, well oxygenated water, the EA added.

Simon Moody, from the EA, said such chalk streams were "precious, natural resources".

"Southern Water's safeguards which should have protected this chalk stream failed one by one. That's unacceptable," he said.

"Chalk streams should be gin clear. Thorough maintenance and tested process would have prevented this."

Following the court hearing, Southern Water said the incident happened "during a period of extreme rainfall and resulted in an asset failure".

"This should not have occurred and fell below the standards we set for ourselves, and that our customers expect," it said.

"We have pleaded guilty at the first opportunity to the pollution that resulted and are cooperating fully with the legal process."

The company is due to be sentenced at a later date.

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