A Geocellular Solution for shallow applications

Permavoid is an engineered system of high strength modular cells, interlocked to create a structural raft with exceptionally high tensile and compressive strength under load. It is suitable for replacing a granular sub-base, with the cells delivering enhanced water storage, and is complemented by silt/oil gravity separation features, floating oil treatment components, oil treatment geotextiles and shallow flow control solutions.

Source Control

Permavoid can be used as part of an engineered or soft SuDS solution, enabling designers to offer an effective source control system, that can incorporate water treatment to manage water volume and quality as close as possible to where rainfall lands.

Silt/debris and hydrocarbons can be managed at the head of the system using system components, such as RIDGISTORMSeparate Silt Traps. This prevents pollution migration into the rest of the SuDS and reduces lifetime maintenance requirements.

Why Shallow?

Shallower attenuation or infiltration structures are often necessary because the site is difficult to access or the ground at greater depths presents a construction challenge, such as chemical contamination, a high water table or hard rock substrate. A shallower approach also minimises the need for expensive pumping equipment, and reduces environmental impact because it requires less excavation and fewer trips to transport infill and rubble to and from site.

It is also much more versatile and cost effective than deeper solutions, as no trench supports are required and the need for expensive, heavy plant usually required during installation is eliminated.

Tried and Tested

The Permavoid system has been extensively tested over the last decade with Salford and Coventry University, the Transport Research Laboratory and Highway Agency, to ensure that the system meets the legislative requirements set out by CIRIA, the Environment Agency, SEPA and PPG.

Academic site-wide trials include:


  • Transport Research Laboratory - A pilot-scale trial of reservoir pavements for drainage attenuation incorporating Permavoid sub-base replacement system


  • Coventry University - Assessment and Monitoring of the Oil Retention and performance of the Permaceptor treatment system


  • SEPA-Perth Prison - A 2 year field monitoring exercise of macro-pervious pavement and car park installation incorporating Permachannel oil and silt retention devices

Literature & Technical info