Lake Windermere: United Utilities’ Proposed Investment to tackle sewage pollution

Earlier this month, United Utilities published its new proposal for investment into sewage infrastructure for Windermere. 

Beginning in 2025, this would see investment of “more than £150 million” into nine wastewater treatment sites and each of the six combined storm overflows (CSOs) which flow into the lake.

United Utilities claims that its investment will reduce the number of spills from these CSOs to 60 spills per year. Environmental Permits require that CSOs only spill during certain “exceptional circumstances”. 

Investigative work by the campaign groups Save Windermere and Windrush Against Sewage Pollution suggests that all six of United Utilities’ CSOs at Windermere currently spill into the lake in breach of their Environmental Permits. Save Windermere alleges that with this investment, United Utilities is effectively asking customers to pay for the company’s alleged pollution.

United Utilities is required to provide real time data on the performance of their CSOs, known as Event Duration Monitoring (EDM). EDM data shows that in 2023 there were 491 spills, running for a total of 8,787 hours. That is the equivalent of 366 full days’ worth of sewage flowing into the lake.

Sewage is high in the nutrient phosphorus. When CSOs spill into a body of water like a lake, the phosphorus it contains can cause the rapid growth of algae along the water’s surface. These ‘algal blooms’ prevent sunlight from penetrating the water and strip it of oxygen, harming its entire ecology. Phosphorus can also cause the growth of blue-green algae, which can be harmful to both humans and animals.

After testing a section of Lake Windermere this year, Save Windermere found that the waters exceeded the WHO threshold for blue-green algae.

In 2023, the Environment Agency attributed roughly 40 per cent of phosphorus pollution in Windermere to United Utilities.

Leigh Day is currently representing thousands of local people and businesses in the River Wye Catchment for the losses they have suffered as a result of phosphorus pollution allegedly caused by industrial agriculture.

Given the challenges faced in Windermere, it is clear that something needs to change to protect one of the UK’s most iconic natural features. It remains to be seen whether United Utilities’ proposals go far enough, particularly given the evidence that its CSOs already spill in breach of their Environmental Permits.

In 2023, United Utilities investigated the feasibility of completely removing sewage infrastructure from Lake Windermere. This month’s new proposal falls well short of this goal.