Minimising or eliminating discharge of untreated or contaminated water into the environment is a major objective for Severn Trent. To reduce flood risks at Oldcotes Pumping Station, a storm drainage tank was to be constructed and connected to the existing sewer network. The system would use two separate legs of 2.3m-diameter High-Density Polyethylene (HDPE) pipe, one 32m long and the other 20m long.
Located near Oldcotes Dyke, the site consisted of variable ground conditions consisting of dense sands and gravelly alluvium with dolomitic limestone bedrock at shallow depth. Groundwater was recorded as shallow as 1.7 – 2.0m below ground level, with groundwater pressure along the faulted and voided zones within the limestone. The conditions presented a significant buoyancy risk, and required measures to counteract uplift, while challenging strata conditions ruled out conventional grouting methods due to flowing groundwater causing washout.
