ProTank® detention system provides an effective solution for storm water management.
The Problem
A new Auto Masters store to be constructed in Adelaide’s north, was mandated by local authorities to include a storm water detention system to aid in mitigating flood events. Depth of existing services and limited building footprints limited the design options. The system had to meet a minimum holding capacity of 54,000 litres, later increased to 76,000 litres.
The Solution
ProTank®, a stackable high strength below-ground modular stormwater system, was installed as a detention ‘gallery’ below the proposed carpark. Contractors excavated a shallow rectangular zone to approx 2.0m depth. The excavated area was then lined with ‘SuperFlex’, an impermeable membrane, sandwiched between two layers of ‘Geofirma’ cushion geotextile, to provide protection to the membrane from puncture. The ProTank® units were clipped together beside the excavation in a triple module, heavy duty configuration before being placed over, and then wrapped by, the composite lining system.
During the backfilling operation, a layer of ProFab® AS140 warning geotextile (High Vis yellow/orange) was installed between the two compaction lifts, to act as a marker layer (or ‘warning layer’) for any future excavation works on site.
The modular construction method of the ProTank® system exhibits definitive advantages over a more traditional approach of using precast concrete tanks, due in part to the ability to configure (or even re-configure) the layout of the gallery to suit geometric constraints found on site. Just prior to delivery of materials to site, the client increased the required capacity of the system by over 20,000 litres. A quick recalculation and it was confirmed an increase in the footprint size of the gallery (from 8 x 19 to 10 x 22 modules) would allow the system to meet this new volume and still remain within the dimensional constraints of the site without any alterations to the existing construction plans.
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