Tunnelling completed on Stroud sewer upgrade

22 September 2023

Tunnelling has been completed on Severn Trent’s £25m project to reduce sewage overflows in Stroud, Gloucestershire.

Four TBMs were used to lay the 1.7km of new 1.5m diameter sewer pipes and project manager Chloe Dobbs said the project was making good progress.

“We’ve completed the laying of the trunk sewer with all of the tunnel boring machines which has been a big piece of work and we’ve finished laying the rings of the new CSO storm tank shaft which is 26m in depth,” she said.

One of the TBMs was named Florence after the daughter of Severn Trent community communications officer Shannon Currall

“Using the tunnel boring machines has been so beneficial – they have been cutting through the earth, laying new pipes in their path without residents being aware of the amazing work going on beneath their feet.”

The new CSO site houses a 7,400m3 storm tank that will increase the capacity of the local network considerably.

It will have smart controls to hold water back during severe weather events, before returning it to Severn Trent’s treatment works when rainfall has subsided and capacity to treat it is available. 

“The new CSO site and extra capacity doesn’t only tackle the issue of sewer flooding, it will mean that there will be fewer spills into watercourses, such as the River Frome. Once finished, it will have a massive impact on the local area and will play a huge role in our Get River Positive commitment that by 2030 our operations will cause no harm to rivers,” said Dobbs.