Proposed 19km tunnel would carry sewage away from Windermere
A project backed by United Utilities, the Environment Agency and local campaigners has set out a plan to end sewage discharges into Windermere by building a 12-mile (19km) tunnel that would carry sewage away from the lake, The Guardian reported on 21 October 2026.
Windermere is England's largest lake and lies within the Lake District World Heritage Site. It suffers raw sewage and bacterial pollution linked to discharges from United Utilities, the water company that operates in the area, and receives an estimated 17.7 million visitors a year.
The tunnel is estimated to cost £3.6bn. United Utilities plans to seek government permission to raise customer bills to pay for it. The company said the programme could add up to £3.17 per month to water bills in 2035.
The project will now move into a detailed design phase. Construction is expected to take two years, and United Utilities said completion could take seven years if permission to raise bills is granted. Treated effluent, meaning wastewater that has been through treatment, would be discharged either into the River Leven or into the Irish Sea at Ulverston.
The proposal builds on a feasibility study. Save Windermere, a campaign group led by Matt Staniek, is a partner in the project, and its report involved weekly meetings over 15 months. The project team considered the clean-up of Lake Annecy in France as a model.
United Utilities has published a newsroom item on the study, titled Coalition publishes landmark blueprint for Only Rainwater into Windermere. It concluded that it is technically possible to remove wastewater inputs and highway runoff, meaning rainwater that drains off roads, from the lake. The study proposes a new sewer network, largely off the highway with some sections under the road, using a 1500mm diameter pipe.
The question of pollution is not new. Campaigners from Windrush Against Sewage Pollution (WASP) and Save Windermere identified 140 illegal sewage spill days in Windermere in 2024, more than in any previous year they recorded, according to the BBC.
