Tunnelling starts on Sheffield Forgemasters flood alleviation scheme
Civil engineering firm JBA Bentley is leading the £19m project, which includes driving a 1,050ft-long tunnel beneath Brightside Lane and forms part of the wider £1.3bn redevelopment of the Ministry of Defence-owned site.
The tunnel will connect two shafts that have been constructed as part of the scheme. One shaft, located on the north side of Brightside Lane, is more than 40ft wide, while the second, closer to the River Don, is more than 15ft wide. Both extend more than 35ft below ground.
The tunnel will provide a connection between the two shafts and form part of a new system designed to intercept the Lower Don Valley’s enclosed Bagley Brook culvert as it enters the Sheffield Forgemasters site.
The system will allow storm water to overflow from the culvert and be temporarily stored before being transferred into the River Don.
As part of the works, a section of flood wall at Sheffield Forgemasters’ boundary with the River Don will be repositioned to accommodate a new outfall structure and a pumping station will discharge storm water back into the river through the outfall at a rate of up to 8,000 litres per second.
The flood alleviation scheme forms part of the planning requirements associated with Sheffield Forgemasters’ new 13,000-tonne Forging Line, which is currently under construction adjacent to the Midland Mainline railway and forms part of the company’s wider programme of investment at its Sheffield site.
Known as the Bagley Brook transfer system, the project will address a known flood-risk when the culvert is unable to channel abnormal volumes of storm water, causing flooding at the Northern part of the Brightside Lane site.
Gareth Barker, chief operating officer at Sheffield Forgemasters, said: “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.
Gareth added: “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.”
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.”
