South West England
Permavoid geocellular attenuation system
Polypipe provided a sub-base replacement stormwater attenuation solution for Winnersh Triangle, a large park and ride car parking facility between Wokingham and Reading.
The site had been identified by both Reading and Wokingham borough councils as an ideal location for a new 390 car parking space park and ride, in order to give commuters greater public transport options.
The site is notoriously prone to flooding. Its geology consists of a high water table to cover level, which meant that a surface water attenuation solution needed to be carefully considered.
Polypipe selected a Permavoid geocellular attenuation system for this site, as the system can be installed above the high water table.
The system consists of 29 shallow Permavoid attenuation tanks with a storage capacity of 590m³.
The tanks were strategically positioned around the site to eliminate the need for the installation team to work within the ground water zone.
The surface finish consisted of both gravel and asphalt. Polypipe assisted the design team with structural and flotation calculations to ensure the minimum depth of sub-surface could be achieved, while preventing the geocellular tanks from floating.
Polypipe worked with main contractor Dawnus to also ensure that structural loading calculations were carried out to define travel routes for the different surface laying machinery.
The Permavoid geocellular structure incorporates a jointing mechanism that makes it able to support structural loads across heavily trafficked areas on the site.
Richard Tithecott, Project Manager, at Dawnus Construction, said: “The team from Polypipe were a huge help on this project not only in selecting the right product, but assisting with the necessary structural loading calculations. These calculations substantiated our belief that the specified Permavoid system was more than strong enough to cope with the loads likely to be placed on it, which was one of our primary considerations when selecting a shallow attenuation solution”.