Untreated sewage illegally pumped into Windermere

Millions of litres of raw sewage were illegally pumped into one of England's most famous lakes after a fault, documents seen by the BBC have revealed. United Utilities failed to stop the illegal pollution of Windermere, in the Lake District, for 10 hours in February and did not report the incident to the Environment Agency until 13 hours after it started. An almost identical incident occurred at the same location in 2022.

The firm says it took urgent steps to resolve the incident in February. A pumping station in Bowness-on-Windermere, in Cumbria, normally sends sewage to Windermere Wastewater Treatment Works. But United Utilities documents, obtained by the BBC, show how a telecoms fault on the night of 28 February caused the main pumps to stop. A separate set of emergency pumps then discharged untreated sewage into the middle of Windermere, which is part of a Unesco World Heritage site.

It is England's largest lake and one of the country's most popular natural attractions.The documents show the pumps started discharging sewage into the lake at 23:34 GMT and continued intermittently until 09:49 GMT the following day. When the pumping station is fully operational it is permitted to discharge untreated sewage into Windermere if it’s overwhelmed by rainfall or snowmelt. That wasn’t the case in this incident, meaning this release of sewage into the lake was illegal.

Insiders at United Utilities have told the BBC that, in total, the emergency pumps operated for six hours at nearly 500 litres per second - dumping more than 10 million litres of raw sewage into the middle of the lake. The water firm says it did not measure the volume of untreated sewage pumped into the lake, but it says the BBC’s estimate of the scale of the discharge is unreliable. The company says the incident “was caused by an unexpected fault in the telecommunications network in the area, which United Utilities was not notified about”.