Reducing storm overflows with a new storm tank to protect the River Sowe

Finham Sewage Treatment Works New Storm Tank

The Finham Sewage Treatment Works (STW) in Coventry treats wastewater for around half a million people. Severn Trent wanted to do more to reduce the impact of heavy rain and the resulting storm overflows into the River Sowe, which connects to the River Avon further downstream. Severn Trent Water asked our team to design a new storm tank for Finham STW to reduce storm overflow and improve water quality in the river for bathers and the environment.

Project plans originally called for a deep circular shaft, but unexpected groundwater conditions made this design unfeasible. Our team quickly switched to a rectangular tank design that was better suited to challenging sub-surface water conditions and could be built with less excavation. We used specialist piling to create strong foundations with little vibration, helping keep the site stable and reducing the amount of water that needed to be pumped away. The redesigned tank also removed the need for deep pumps, lowering operational carbon and cost while making construction faster during winter months. Newsletters, video content, and a dedicated virtual room kept the local community up to date with project’s progress and informed them of the long-term benefits for the river ecosystem.

Completed and operational before the project deadline, the 4,880-cubic-metre tank stores stormwater safely during wet weather before being passed on for treatment. This reduces spills to the River Sowe, which benefits both ecology and bathers. There are also planned biodiversity improvements, including tree planting and bird boxes, to help the area recover and support local wildlife.