A coalition including United Utilities and the Environment Agency has outlined a £3.6 billion to £3.7 billion plan to divert wastewater from Windermere, with funding arrangements still to be explored.
The coalition published its feasibility study Oct. 21 after 15 months of development. It assessed more than 70 options and selected two for further work. Each would use a tunnel to move wastewater away from England’s largest natural lake for advanced treatment. Detailed design is still ahead.
The proposals include up to 138 kilometers of new sewer lines, 35 kilometers of systems to intercept runoff from roads and 37 hectares of sustainable drainage. The coalition estimates that about 12,800 people could receive their first connection to public sewers.
It also estimates the investment could produce about £7.5 billion in economic, environmental and social benefits. The coalition values the Lake District visitor economy at £2.4 billion a year and identifies connected waterways, downstream ecosystems and local employment as potential beneficiaries. It has cited combined sewers, heavy rainfall and flood exposure among the pressures the plan would address.
The UK government pledged in March 2025 to work with local partners toward ending sewage discharges into Windermere. Its statement identified pollution from United Utilities wastewater, private sewage treatment and rural and urban land use. Environment Agency modeling published in May projected that climate change could raise annual nutrient inputs to Windermere and nearby Esthwaite Water by up to 7% by the 2070s. The agency identifies wastewater and land runoff as nutrient sources.
United Utilities is carrying out a separate £200 million improvement program around Windermere. As of Oct. 1, it covered 15 projects, including upgrades to nine treatment works and added storage at six storm overflows.
Steve Ratcliffe, director of sustainable development strategic change at the Lake District National Park Authority, called the new proposal “a feasibility study rather than a final decision.” The coalition’s next steps include detailed design, planning, environmental assessment and regulatory approvals. It estimates construction would take seven years after those steps, but has given no start date. Funding arrangements also remain to be explored.
