Permeable Pavements - Technical Information

Increasing storage in permeable pavements - hydraulic benefits

Additional attenuation storage capacity may be provided within the pavement construction by substitution of the sub-base material with Permavoid units, offering additional attenuation storage benefits, due to the unit’s significantly higher porosity. The Permavoid unit having a nominal porosity of 95%, compared with a typically assumed granular sub-base material porosity of 30%.

The Permavoid system forms a unique high strength structural raft, complying with the British Standard (BS 7533-13:2009) design guidance for permeable pavements constructed from engineered and natural pavers.

Geocellular units can also behave as a conduit, provided a continuous installation is maintained across the pavement cross section, with flows typically driven by hydraulic head. This form of construction may also be used with pavement gradients steeper than 3%, provided appropriate check dams are created within the structure. 

These check dams may be formed through the creation of geomembrane barriers, in addition to the optional use of geofoam units as an effective flow control. Geocellular units have a uniform shape and high porosity, in addition to offering a higher flow resistance than conventional pipe systems, which would further slow the flow of water through the system.