Hewitech specialise with attenuation & soakaway tank design. All modular storage systems should have a site specific assessment of the long term loads, vertically and laterally imposed on the structure by live loads (traffic) and dead loads (construction above the tank).

The industry standard for this is the CIRIA C680 calculation that incorporates a 2.75 material safety factor applied to the crate compressive test strength. Hewitech’s bespoke software to C680 will provide engineers and contractors with the requisite structural assessments.

Variobox offer the engineer greatest flexibility attenuation tank design that best fit the site’s drainage constraints and available space for construction

• Variobox Plus vertical test loading 700kN/m² lateral test loading of 200kN/m², Variobox Traffic 400kN/m² 100kN/m²
• Variobox depth configurations, 50,65,80, 100, 150, 200, 300, 400 and 600mm.

Hybrid tanks can be designed with the Variobox Traffic towards the tank soffit and the Variobox Plus at the base as the lateral imposed load increases with depth

If groundwater is present above the base of the tank a floatation check should be carried out by Hewitech

Access and maintenance to the engineer’s design is achieved by incorporating the Controlbox with a 500mm open channel, enabling debris to be cleared from the system using traditional drainage jetting techniques.

All attenuation tanks should have a vent to allow air to escape from the system, The CIRIA standard is one vent per 7500m2 of drained impervious area.