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Stroud Sewerage Scheme Gloucestershire

Work is about to start on the latest and final major phase of the Stroud sewerage scheme, which features the largest shaft ever designed by BSP Consulting to date.

BSP engineers are part of the team involved in a £25 million project to improve the sewer network in Stroud, Gloucestershire.

Tunnelling work is almost complete and now work is starting on a huge 27m deep shaft with an internal diameter of 25m and an external diameter of 26m.

Some 14,300 cubic metres of soil will be removed, with almost 2,000 cubic metres of concrete poured in a single pour over four days to create the reinforced concrete base.

The civil engineering work for the Combined Sewer Overflow chamber is due to be completed by the end of November, and is the last major phase of the Stroud sewerage scheme.

Heavy engineering

BSP associate Paul Hammersley said: “This is the largest shaft that BSP Consulting has designed to date.”

“We were delighted to be appointed on the Stroud sewerage scheme, supporting Severn Trent to improve the sewer network in the town. This is a pivotal moment in the work and will be one of the largest single concrete pours that BSP have undertaken, although well short of the UK record!”

BSP was appointed by contractor Galliford Try to carry out the tunnelling design and shaft design works for the project.

Severn Trent is installing more than two miles of new pipes, upgrading many of the old Victorian sewers in the town, as well as removing the existing large sewer pipe that runs through the canal channel in Stroud.

The work will provide those living in Stroud with a reliable sewer network, as it will create more storage and larger sewer pipes – helping to protect homes and businesses from blockages and flooding. The new shaft provides 7,830m3 of off-line storage on the sewer network and hydraulic modelling predicts the new CSO site will reduce the sewage spill frequency into the River Frome from 50 to 4 occurrences in an average year.

BSP Consulting have redesigned the base slab and managed to reduce its thickness by 600mm from 3600mm to 3000mm thick, which combined with the introduction of an additional shaft ring has not only made the shaft easier and safer to construct, but will reduce the amount of  CO2  from the concrete alone in the base slab by approximately 100tonnes.  There has also been savings made in the amount of steel required, amount of “muck of site” and its associated transportation and an overall cost saving to the scheme.

Read more about the scheme here:


  • Structural Engineering
  • Heavy Engineering


Severn Trent


Galliford Try

Project Description

Civil engineering work for the Combined Sewer Overflow chamber.







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