Church Street West CSO Chamber, Radcliffe

This project was a particularly demanding scheme due to several site conditions that affected the construction of an underground concrete CSO chamber and an adjacent storm overflow into the River Irwell.

The site was incredibly tight being in the middle of Radcliffe town centre and major services within the highway needed to be diverted to allow the construction of the chamber including a 300mm diameter gas main, high voltage cables and a 150mm diameter watermain. As service diversion works were being undertaken by the utility companies, the adjacent steep riverbank was stabilised using soil nails, shotcrete and grout injection prior to the construction of the 11.0m x 6.0m x 7.5m deep sheet piled excavation. Rock was encountered at 6.0m deep and  the final 1.5m of excavation needed to be broken out without damaging an adjacent listed building which was continually monitored for excessive vibration.

The base and walls of the chamber were constructed of 170m3 of reinforced concrete and the roof comprised of sectional precast units each weighing up to 20 tonnes. The outfall structure comprised of a further 100m3 of concrete and the chamber and outfall were connected by a 900 mm diameter outfall pipe tunnelled through the rock in a timber heading. Following construction of the concrete chamber, completion works included installation of a mechanised screen, electrical supply, access platforms and ladders.