Southern Water has pleaded guilty to environmental offences after polluted wastewater was discharged into the internationally renowned River Test in Hampshire. The water company admitted breaching its environmental permit after the Environment Agency discovered a dark plume of pollution flowing from its Fullerton Wastewater Treatment Works, near Stockbridge, in March 2023. Southern Water entered guilty pleas to two charges at Medway Magistrates’ Court on 14 July 2026. The company will be sentenced at a later date.
Pollution discovered during routine inspection
The incident came to light on 13 March 2023 when Environment Agency officers carrying out routine water quality monitoring noticed dark particles in the River Test. Following the pollution upstream, investigators traced the source almost four miles to Southern Water’s Fullerton treatment works. The plume, which had a distinctive reddish tint caused by elevated iron levels, stretched across around half the width of the famous chalk stream. Sampling revealed levels of suspended solids were more than three times the legal limit, while concentrations of iron also significantly exceeded the site’s environmental permit.
Equipment failures and missed warnings
The Environment Agency’s investigation found that several safeguards at the treatment works had failed. Staff confirmed that only one of the site’s four settlement tanks used to remove sludge and scum was working correctly, with another having been awaiting repair for more than a year. Investigators also found problems with pumps responsible for sending treated wastewater through sand filtration beds, with maintenance issues having been recorded in site logs days before the pollution occurred. Southern Water also admitted it failed to notify the Environment Agency after becoming aware of the equipment failures and the deteriorating quality of treated wastewater. The company later acknowledged it had missed at least two opportunities to report the incident and failed to follow its own internal reporting procedures.
‘Chalk streams should be gin clear’
Simon Moody, of the Environment Agency, said:
“Chalk streams like the River Test are precious, natural resources. But they are also fragile and this incident came to light thanks to the close eye we keep on their health.
“Southern Water’s safeguards which should have protected this chalk stream failed one by one. That’s unacceptable.
“Chalk streams should be gin clear. Thorough maintenance and tested processes would have prevented this.”
Threat to unique wildlife
The River Test is internationally recognised as one of England’s most important chalk streams and supports a unique population of Atlantic salmon. The Environment Agency said salmon born in the River Test are genetically unique and rely on clean, highly oxygenated water to survive, making them particularly vulnerable to pollution incidents.
Water quality improved
Follow-up sampling carried out on 24 March 2023, 11 days after Environment Agency officers intervened, confirmed water quality had significantly improved.
Two charges admitted
Southern Water pleaded guilty to:
- Discharging treated wastewater containing suspended solids above the permitted legal limit.
- Discharging treated wastewater containing excessive levels of iron.
Two further environmental offences will also be taken into consideration when the company is sentenced. The Environment Agency said it completed more than 730 inspections of Southern Water sites this year, with 68 per cent found to be compliant with their environmental permits. Inspectors issued the company with more than 400 improvement actions following those inspections.
