Severn Trent says storm overflow spills were 'reduced by 65 per cent' in past six months

The announcement was included in a trading update to financial markets following the company's AGM this week (July 9).

Severn Trent said more than 2,000 storm overflow intervention projects have contributed to an average spills performance of around five per storm overflow for the first six months of 2025. 

The company said this represents a 65 per cent reduction on the equivalent period in 2024, with the firm saying it is "firmly on track" to achieve a target of reducing average spills to below 18 per storm overflow this year.

Storm overflows occur when the sewage system is in danger of being overwhelmed, and untreated rainwater and wastewater is released into rivers or seas to ease pressure on the system.

The company, which serves around 4.5 million customers in the Midlands and Wales, has previously come under fire for its environmental record - and last year was fined more than £2m for an incident in 2020 which saw 260 million litres of raw sewage illegally discharged into the River Trent in Staffordshire.

The company has since announced a £450m programme of work to reduce sewage spills across its network, which includes around 1,000 individual schemes.

In an update to markets delivered this week, Severn Trent said financial performance for the year remains "on track", including at least £25 million in performance related incentives.

"We anticipate the main contributors of our operational outperformance to be improvements in leakage, driven by increased proactive work to find and fix leaks, and our continued efforts to bring down storm overflow spills," they said in a statement.

"In the first quarter, we have invested around £360m in our capital programme, up 19 per cent year on year, and we are on track to deliver between £1.7bn and £1.9bn of capital expenditure in FY26."

In a statement issued earlier this year, the company said it had completed more than 1,500 permanent improvements which had resulted in a reduction of around 24,000 spills from storm overflows in the region.

“From new storm tanks to new treatment solutions, we’ve mobilised a huge team of engineers who are working non-stop to deliver for our customers," said James Jesic, Severn Trent capital delivery and commercial director.

"The team has delivered a major milestone of installing 1,500 overflow improvements, which was made more challenging given the extreme weather events and flooding in many locations. 

"We’re now going even further and even faster by delivering an extra 600 projects by autumn 2025.”