Brierfields WwTW, Stormwater Storage Tank

United Utilities built a new underground stormwater storage tank on Lindred Road in the Lomeshaye Industrial Estate, Nelson. At 20 metres deep and 15 metres wide, it holds almost two million litres of storm water, giving Pendle's sewer network extra capacity in heavy rain and reducing overflows into Pendle Water.

Working for principal contractor Advance Plus under an NEC Option A contract, SGC delivered the pipework and chamber package that connected the new tank into the existing sewer network:

• Large-diameter concrete pipework at depths of around 4.5 m, including excavation within a 5 m deep cofferdam
• 150 mm ductile iron mechanical outlet pipework
• Modifications to an existing combined sewer overflow (CSO) chamber, including a new weir wall
• A 2.1 m internal diameter manhole
• Masonry access shafts and associated ducting

Deep excavations had to fit within a tight footprint on a working industrial estate, through a congested network of live underground services. We worked with Advance Plus to develop engineered solutions, including cofferdam excavations to 5 m, and agreed working methods and sequencing to protect live services while keeping the works moving. The weir wall and other modifications inside the live CSO chamber were planned and delivered as a controlled, self-contained operation.

Delivering pipework, mechanical ductile iron, chamber structures, masonry and ducting as one contractor reduced interfaces for the principal contractor. The package was completed on programme and under budget, enabling the new tank to be connected into the existing sewer network and CSO.

Watch the project film