Supermarket chain makes Permavoid purchase for new store
Polypipe’s Permavoid solution meets challenging requirements on-site at a new retail development.
When a national supermarket chain selected a site for their newest food store, main contractors MLM Consulting Engineers turned to Polypipe to provide a water management solution to meet the challenging terrain.
Located in the small Essex market town of Coggeshall, the development featured a high water table at a depth of 0.5m, which was likely due to hydraulic connectivity from a nearby river. Polypipe utilised its popular Permavoid geocellular solution to provide a suitable sub-base replacement system.
The void ratio of Permavoid cells provided ideal coverage levels for the expected rainfall levels within the footprint of the development’s car park area.
Capable of attenuating 110m3 of storm-water, Polypipe supplied Permavoid cells that were 150mm deep to create a high strength structural raft. The system sits beneath permeable paving in place of the traditional aggregate sub-base.
Located beneath the site’s car parking facility, the system specified was required to withstand heavy loads from HGVs and cars during day to day retail and residential use. As the Permavoid’s 95% void fill ratio made it an ideal solution for storm-water storage, it’s high vertical and lateral strength made the tank strong and durable to withstand daily heavy loads.
Using Permavoid at shallow depths meant that necessary excavation was greatly reduced and the light weight, interlocking system meant that installation could be much faster.
To avoid any future pollutants potentially entering the local watercourse, Polypipe provided its Permafilter geotextile beneath permeable pavement and above the tank in order to trap oils and break them down through biodegradation.
Jim Rudd, Director at MLM, said: “With varied cover levels and a high water table, there were a number of engineering challenges to overcome on this site. Thankfully, Permavoid offered us the chance to engineer a solution strong enough to cope with the site’s necessary HGV traffic without compromising on stormwater storage or depth levels.
“The interlocking nature of Permavoid cells also meant that we could configure a system that made best use of the space available on site, providing ideal coverage levels for expected rainfall levels within the footprint of the development’s car park area.”