Selwood’s pumping solutions specialists were able to greatly reduce the financial and environmental cost of works to repair a leaking sewer in Nottingham for Severn Trent Water. The leaking 600mm rising main gravity sewer had the potential to cause serious disruption, as it was on a main road crossing within a few metres of tram tracks and could have burst or created a sink hole.
The initial emergency response before the arrival of the Selwood team had been to use a fleet of 29 tankers to take the water away – a noisy and costly operation with a significant environmental impact.
The challenge
The job at hand was to install an efficient over pumping solution that would bypass the damaged sewer, covering 550 metres from the pump station to the next gravity manhole.
The site was a difficult one due to its location on the public highway and close to the active tram network. Because of this the local authority had to approve all movements.
Works around the tram lines could only happen during a limited time when the tram service was shut down, and equipment could not be lifted to a height above three metres to avoid disrupting the overhead tram power cables. In total the tram was shut for 31 hours across a weekend
The solution
After assessing the site, Selwood’s team specified a set of eight-inch suction pumps, pumping into a 300mm discharge line. Due to the wet well being too small submersible pumps were not an option for this project.
Instead, three electric-powered S200 75kw Selwood Super Silent sewage handling pumps were installed in a Duty/Assist/ Standby configuration to ensure uninterrupted operation. These were chosen for their reliability and ability to lift water out from the wet well even more capably than submersibles could.
To minimise disruption to residents and traffic, four road ramps were used to allow access to local businesses, including a nearby timber yard which was the source of regular HGV movements, and a private boat yard.
A 12-inch mag flow meter was used to monitor flow from the pump station. This helped indicate when the road ramps were starting to rag up and would need cleaning. Tankering points were added along the drain line to enable regular inspection and cleaning.
For the works around the tram lines, a height-restricted crawler crane and low loader trucks were used to keep works clear of the overhead cables.
The result
Despite the challenges, the job was installed in less than a week. The use of electric pumps as specified by Selwood saved a huge amount of time and cost along with significantly reducing the environmental impact of the works.
Continuing to tanker away the water would have cost well over £400,000 for the duration of the works, with the Selwood alternative
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