The Permavoid Source Control System
The Permavoid Source Control System has been developed for the management of surface water. It extends the choice and flexibility for sustainable drainage solutions by providing robust, effective source control through attenuation or soakaway at shallower levels.
The Permavoid System comprises of high strength modular cells suitable for sub-base replacement in trafficked pavements, channel and gully components incorporating silt/oil gravity separation features, floating oil treatment devices, special oil treatment geotextiles and shallow flow control devices.
It allows the designer to overcome many inherent site problems such as high water table, contaminated soils, unstable ground, rock head, shallow outfalls from site.
Using the Permavoid Source Control System can enable expensive pumping station installations and petrol interceptors to be designed out of drainage schemes.
Where Can Permavoid Help?
Overcoming high water tables
High water tables and even perched water at shallow depth require specific design and construction measures to avoid issues such as flotation of attenuation structures and often prevents the use of soakaways. Anti-flotation and temporary dewatering measures are invariably very expensive, but Permavoid can often provide the attenuation or infiltration solution by avoiding groundwater issues.
Avoidance of pumping stations
Shallow Permavoid systems can very often avoid the need for pumping that might otherwise be required with conventional drainage or deep attention tank solutions. Pumped solutions can be costly to install and maintain and considered to be environmentally unsustainable.
In contaminated sites
Redevelopment of brownfield sites is common-place and issues of ground contamination often come hand in hand. The use of Permavoid shallow attenuation or soakaway structures can very often avoid the need to excavate into contaminated soils that invariably incur significant abnormal costs in either on-site remediation or off-site disposal and the numerous associated environmental issues. Thus, the use of Permavoid systems can often avoid substantial costs and reduce overall construction time.
Over hard rock
Excavation of hard rock is usually expensive and slow. However, Permavoid is ideal for use on sites that are underlain by hard rock at shallow depth, as the systems can be incorporated into the pavement construction invariably avoiding any net additional excavation for the drainage system.
On podium decking
On podium decks, key design, construction and cost issues usually involve issues of weight of overlying construction, creation of falls for drainage layers, pipe penetrations through the deck and loss of headroom within the underlying basement due to the need to suspend drainage beneath the overlying deck. Permavoid systems can avoid all of these issues as it can provide an effective drainage and attenuation layer without the need of falls or outlet penetrations through the deck; is lightweight and can accommodate a wide range of finishes including soft landscaping, activity areas and vehicular pavements.
Difficult site access
In narrow, restricted or otherwise limited access sites, Permavoid can be easily manhandled into place without any heavy lifting or off-loading gear. With a 95% void ratio space for maximum water retention, the lightweight cells can be carried and installed by a single construction worker.
Benefits of the Using the Permavoid System
- Designed and tested for attenuation or soakaway at shallower depths
- Provides effective source control
- Interlocking raft for rigidity and a high compressive and tensile strength under load
- Can be installed above a high water table
- Allows water to be spread across a wide area
- Suitable for use beneath porous and non-porous surfaces
- Ideal for brownfield or contaminated sites
- Removes the requirement for pumping stations
- Reduction in excavation depth and cost
- No need for trench supports or plant to deliver and remove trench support panels
- Provides treatment to remove silt and hydrocarbon deposits
- Oil interception at source – no need for petrol interceptors
- Can be used in combination with other geocellular solutions for deeper applications
Permavoid Modular Cell Sub-base Replacement System
The Only Sub-base Replacement System
Permavoid can be used in place of a traditional aggregate sub-base within trafficked pavements and provides a unique high strength, consistent structural raft with all the associated benefits of highly voided modular geocellular structures. Permavoid can enhance the attenuation capacity of a porous pavement and may also enable the reduction of granular thicknesses. The system is suitable beneath asphalt, block-paved or concrete pavements for the full range of traffic conditions from HGV to domestic driveways. Using Permavoid can reduce the depth of your excavations, saving time and substantially cutting the volume of muck-away, reducing costs.