Attenuation tanks are installed in an excavation prepared and backfilled by the contractor using Variobox crates, LLPE membrane and a protective fleece. The installation is warrantied for 30 years as the membrane is wedge welded and the joints air tested.
Pipe connectors for drainage and ventilation are attached to the tank by Hewitech to facilitate connection of the stormwater pipework by the contractor
Variobox attenuation systems for stormwater retention are the strongest available, proven by rigorously testing for long term performance.
Variobox Plus with a vertical test loading of 700kN/m² and a lateral test loading of 200kN/m² enable the Hewitech system to be designed and installed at greater depths than other crates available within the industry.
Variobox Traffic with a vertical test loading of 400kN/m² and a lateral test loading of 100kN/m² can be used in most trafficked situations
Access and maintenance to the engineer’s design is achieved by incorporating the Controlbox with a 500mm open channel.
The maintenance channel is used to clear debris from the system using traditional drainage jetting techniques.
Variobox 600mm x 600mm footprint is available with depth configurations, 50,65,80, 100, 150, 200, 300, 400 and 600mm.