Dwr Cymru’s water treatment works at Chester ‘discharged up to 1,000 tonnes of waste’ into the River Dee yesterday.
Water bosses have released an apology but say ‘no services to customers’ were affected.
An investigation has begun to find the cause of the spillage which came from Dwr Cymru/Welsh Water’s Chester treatment plan.
“We are working closely with our partners to investigate if there are any impacts following the incident.”
Steve Wilson, managing director of Dwr Cymru/Welsh Water’s Wastewater Services, said: “We are currently investing £6.9 million to improve how we treat wastewater in Chester.
“This, as well as the location of the burst pipe, meant that we had to release partially treated and diluted wastewater into the River Dee.
“This helped us to avoid any further problems which could have impacted on the wider sewer network.
“While no services to customers were affected by this burst, we are extremely sorry that this has happened.
“We notified both the Environment Agency and Natural Resources Wales and will continue to investigate and work closely with them to minimise any potential impact this may have on the surrounding area.”
An Environment Agency spokesman, said: “We are aware of the pollution incident affecting the River Dee near Chester.
“We are working closely with our partners to deal with the impacts following a release of sewage into the river, to minimise any impacts on the local environment and investigate the cause.”