The Permavoid system is designed to be used in place of traditional aggregate sub-base, providing a unique, high strength, consistent structural raft with all the benefits of a high voided modular geocellular structure.
All Traffic Conditions
Permavoid can be incorporated into the full range of traffic conditions from domestic driveways to HGV applications, and is suitable below pervious and impervious asphaltic, block paved or concrete paved areas. The system complies with the requirements of BS 7533-13 and incorporates a high vertical compressive strength of 715kN/m² and lateral compressive strength of 156kN/m².
High Water Table
With high water tables and even perched water at shallow depth, anti-floatation and temporary dewatering measures are invariably very expensive. The Permavoid system can provide the attenuation or infiltration required, whilst avoiding groundwater issues.
Contaminated Land
Ground contamination issues are commonplace when redeveloping brownfield sites. Permavoid shallow attenuation or infiltration structures can very often avoid the costly need to excavate into contaminated soils, and all the associated off-site disposal costs and environmental issues.
Hard Rock
The Permavoid system is ideal for sites underlain by hard rock at shallow depth. With the system incorporated into the pavement construction, no additional excavation is required for the drainage system.
Shallow Outfalls
Shallow Permavoid systems can very often avoid the need for pumping required by conventional drainage or deep attenuation tank solutions. Pumped solutions are costly to install and maintain, and considered to be environmentally unsustainable.
Limited Access Sites
Permavoid can be easily manhandled into place without any heavy lifting or off-loading equipment. The footprint of the tank does not have to be square. Segmented tanks can fit into whatever space is available.
Ground Stabilisation
Due to its high compressive strength and bending resistance within joints, Permavoid cells create a horizontal consistent structural raft providing a stable structure.
Soft Landscaped Areas
The Permavoid system can be used to provide pre-treatment of stormwater run-off before it enters a swale, dry basin, pond or wetland. It is even possible to install Permavoid below swales and dry basins to improve treatment and increase storage capacity.
Bioretention Systems
The Permavoid system can be an effective storage and treatment solution when incorporated into the design of rain gardens and bio-retention systems where space is limited.
Multi-Function and Urban Landscapes
SuDS is an integral function of Water Sensitive Urban Designs (WSUD), Permavoid offers an efficient storage and treatment system to help achieve improved stormwater management, particularly when incorporated into urban retrofitting applications. Water management features can be prime design elements in road, highway and urban environment drainage, providing substantial benefits to the built environment. Instead of being a problem, water becomes a valuable resource.
Promoting Passive Irrigation
A Permavoid source control system can provide passive irrigation to enhance amenity and biodiversity in urban and greenfield developments. The hollow structural columns within the geocellular units are filled with an absorbent rockwool which draws up water stored within the unit. The Permavoid raft is covered with a proprietary wicking geotextile that supplies water on demand across the structural raft to irrigate the growing medium.
Public Open Spaces
Acting as both a sub-base replacement system and drainage component, the Permavoid system can give maximum attenuation and infiltration capabilities for both natural and artificial surfaces and can be integrated into site-wide SuDS more effectively. The result is a sustainable development in line with the DEFRA national standards for delivery of SuDS.
Driveways
Any domestic driveway or front garden over 5m² that is being paved must incorporate SuDS to minimise the risk of flooding. The Permavoid system, used in conjunction with permeable paving, can help adhere to requirements whilst allowing a wide range of landscaping options.
With impervious pavements Permavoid can be installed as a replacement for granular sub-base to enhance the attenuation capacity due to the high void ratio of the Permavoid modular cell. Permachannel and Permaceptors are used to capture water out of the hard standing areas. They treat surface water run-off and transfer the flow into the adjoining Permavoid layer.
Increasingly, regulations and design guidance highlight developer's obligation to mitigate the risk of pollutants emanating from contaminated run-off from hard standing surfaces. The most common diffuse pollutants are hydrocarbons and contaminated silts.
