Windermere Wastewater and Storm Overflow Upgrades
United Utilities is upgrading wastewater treatment and storm overflow storage across the Windermere catchment. The programme is valued at up to £200 million and covers 15 projects: improvements at nine treatment works and additional storage at six storm overflows. Some improvements are complete and construction continues at other sites.[1][2]
Current position
On 1 October 2026, United Utilities reported the first Ambleside tank had reached its full height, improvements at Langdale and Grasmere were complete, and work was under way at Troutbeck.
What is being delivered
- Ambleside: Two stormwater tanks at Miller Field will provide 4,500 cubic metres of storage. The first reached its full height by 1 October 2026; the two-tank project is expected to be completed by December 2027.
- Langdale and Grasmere: Treatment improvements are complete, including phosphorus reduction at Grasmere. Further work is planned at Langdale.
- Troutbeck: New treatment technology is being installed. A site expansion at Near Sawrey and further infrastructure at Far Sawrey and Outgate were planned in the October update.
- Further schemes at Glebe Road, Grasmere, Ferry House and Hawkshead are due by 2030. Twelve projects pass through Ofwat’s staged process for assessing scope, cost and funding.