Tunnelling begins on Sheffield flood scheme

A flood alleviation project in Sheffield has reached a key milestone with tunnelling underway beneath one of the city’s main industrial areas.

A 1050ft tunnel is being driven beneath Brightside Lane as work progresses on a new flood protection system at Sheffield Forgemasters.

Civil engineering specialist JBA Bentley is leading the project, which will connect two shafts installed at the engineering company’s site, both extending more than 35ft underground.

Known as the Bagley Brook transfer system, the scheme is designed to reduce flood risk when the Lower Don Valley’s enclosed Bagley Brook culvert is unable to accommodate unusually high volumes of storm water.

The system will intercept excess water, allowing it to be temporarily stored before being transferred into the River Don.

Mark Wood, contracts manager at JBA Bentley, said: “JBA Bentley is working to connect the two large rainwater storage shafts on the Brightside Lane site and will subsequently construct a new weir chamber, integrated into the side of the existing Bagley Brook culvert.

“This will allow a large volume of storm water to be redirected from the culvert to a new pumping station which will be located at the side of the River Don.”

As part of the work, a section of flood wall on Sheffield Forgemasters’ boundary with the river will be repositioned to accommodate a new outfall structure.

A pumping station will then be capable of discharging storm water into the Don at up to 8000 litres per second.

The flood alleviation scheme forms part of planning requirements for Sheffield Forgemasters’ new 13,000-tonne forging line, which is currently under construction alongside the Midland Mainline railway.

Gareth Barker, chief operating officer at Sheffield Forgemasters, added: “We have reached a pivotal point in our flood alleviation works as we start driving a tunnel across our site to join two large storm-water shafts.

“The brook is contained by an enclosed culvert built in the Victorian era along our northern boundary and flows into the River Don but cannot discharge when the river is in flood, causing it to back up through the drainage system during heavy storm conditions.

“The creation of a large underground catchment system consisting of storage shafts, a cross-site transfer tunnel, and pumping station, will allow us to control large volumes of water at critical periods, to be released back into the river at a controlled flow rate.

“We have installed the tunnelling machine in the River Don shaft and both motorists and pedestrians will not even be aware that the machine is in operation creating a six-feet diameter tunnel directly beneath Brightside Lane to reach the other tank.”

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