Working closely with construction company, The Carey Group Plc, and international consultancy and construction company, Mace, Polypipe CGU’s supply and install partner, SEL, undertook an evaluation of the site and its ground conditions, recommending a Permavoid system to provide a shallow solution, due to the site being on Brownfield land, having a high water table and a shallow outfall. The shallow depth of the solution not only negated the need for pumping stations, but also reduced the need for temporary works, in turn reducing installation and labour costs as well as health and safety risks.
The project has seen 28 separate Permavoid attenuation tanks installed throughout the site and, with a combined storage capability of 420,000 litres, Polypipe CGU’s high-strength geocellular Permavoid solution, combined with Permachannel and Permavoid Biomat cells, have been strategically located for the capture, treatment, storage and controlled discharge of rainwater at source.
Permachannel acts as both a surface water collection point and a treatment system that intercepts silt and oil with a zero gradient at pavement level. Water is then discharged from the side of each Permachannel into the Permavoid cells, complete with Permavoid Biomat and Permafilter for further treatment and storage, allowing only treated water to be discharged into the local watercourse.
The system incorporates a unique jointing mechanism that forms an interlocking ‘raft’ that will support structural loads across the most heavily trafficked areas, such as those found on the Coronation Street set.
Sean Robinson, Permavoid Project Manager at Polypipe CGU, said: “Creating a drainage system on Brownfield land is a problematic exercise, with the excavation, disposal and remediation of contaminated soil being a costly and time-consuming process. Permavoid proved to be fit for purpose and was an ideal choice for The Carey Group as it allowed the tram to work at much shallower depths while achieving an appropriate level of water storage and dispersal.
“In addition to capturing the surface water, we were also able to incorporate a treatment process at source through the use of our Permachannel, Permavoid Biomat and Permafilter products.
“The Permavoid system is both a practical and cost-effective solution in such applications, installed in areas to facilitate enhanced water treatment prior to dispersal into the storage aggregate compared to a traditional aggregate sub-base. Permavoid maintains structural integrity and reliability of the sub-base, while providing greater storage volumes and a more sustainable solution to traditional methods.”