Sustainable Drainage

Polypipe’s proven Permavoid geocellular sub-base replacement system has been installed at the recently opened Winnersh Triangle Park & Ride.

Polypipe provided the ideal stormwater attenuation solution for the new park and ride car parking facility, completed in partnership between Reading Borough Council and Wokingham Borough Council to create a sustainable mode of transport for commuters.

Polypipe worked with the project’s consultant engineer from the early design stage to assist with the initial solution for the new 390 space car park. The scheme incorporated 29 shallow Permavoid attenuation tanks with the capacity to store up to 590m³ of stormwater runoff from the car park.

The site’s geology consists of a high water table to cover level, which meant that an attenuation solution needed to be carefully considered. Due to its shallow installation, Permavoid proved to be the ideal solution as it could be installed above the water table. Working with the design team the tanks were strategically positioned to eliminate the need for the installation team, Keytec Environmental Ltd, to be working within the ground water zone.

The Permavoid high strength geocellular solution, incorporates a unique jointing mechanism that forms an interlocking ‘raft’ with exceptional strength that will support structural loads across the most heavily trafficked areas on the site. The surface finish consisted of both gravel and asphalt and 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.

In addition, Polypipe worked with main contractor Dawnus to ensure that further structural loading calculations were carried out to define the on-site travel routes for the different surface laying machinery to allow surface works to be carried out without any detrimental effect to the Permavoid tank installations.

Sean Robinson, Permavoid Project Manager at Polypipe said: “The Permavoid system is extremely flexible and can provide source control water management in very challenging ground conditions. Due to its inherent strength Permavoid is ideally suited to this project acting as a sub-base replacement system in very shallow applications.

“With our wealth of experience on Permavoid projects, we are not just a supplier, we can provide design, and construction support and advice throughout the project.”

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.”

Date: 09 September 2016