SOUTH West Water says its latest upgrade to sewage treatment facilities near Liskeard is already delivering results, with a marked reduction in storm overflow spills this year.

The St Cleer Sewage Treatment Works recorded 108 spills between January and September 2024, during periods when heavy rainfall pushed the site beyond capacity. For the same nine-month period in 2025, the number of discharges has dropped significantly, following the completion of a major infrastructure project.

At the heart of the improvement is a new stainless-steel storm tank, built to provide extra storage when incoming flows exceed the treatment works’ limit. The additional tank is linked directly to an existing tank on the site, meaning both units now operate in tandem. When the original tank begins to fill during a storm event, the new tank immediately provides extra capacity.

Once water levels at the treatment works return to manageable levels, the stored wastewater is pumped back through the treatment process. This ensures that more of the excess flow is treated properly, rather than being discharged untreated into the environment.

To support efficient operation, the new tank is fitted with a debris-screening unit, which removes larger materials before wastewater enters storage. A manual washdown system also helps keep the tank clean and ready for use, ensuring it can perform reliably during prolonged wet weather.

Karl Stone, South West Water’s wastewater operations manager for Liskeard, said the results highlight how targeted local investment can make a measurable difference.

“This is another great example of how targeted investment and the hard work of our teams is delivering real results,” he said. “While much of this year has clearly seen less rain than last year, by increasing storage and improving how flows are managed at St Cleer, we’re helping to protect local rivers and reduce our reliance on storm overflows.

“We’re really pleased with the results we have seen so far and the progress we are making across the region, but we know there is more to do. As a business we are spending hundreds of millions to improve our storm overflow performance but at a local level it’s so rewarding to see these upgrades in place and having a really positive impact."

Storm overflows are designed as a last resort to prevent homes and businesses from flooding when sewer systems reach their limit. However, rising public concern about their frequency has pushed water companies to accelerate improvements.

South West Water is investing around £760-million over the next five years to cut spills across the region. The company has also committed to being the first in the sector to meet the government’s target of fewer than 10 spills per overflow, per year, by 2040 – ten years ahead of the national deadline.

With projects such as the St Cleer upgrade now operational, the company says it is confident that sustained investment, combined with innovation and careful operations management, will continue to reduce environmental impact while protecting local communities from flooding.