Design and Construction of Plastic Geocellular Rain Water Harvesting/Stormwater Detention Tanks

Patrick Wong


Plastic voided modular structures (known as geocellular units) were first used in the mid-1980s in Europe below pavements to store stormwater. Its use has since spread to rainwater harvesting and on-site stormwater detention for residential, commercial and industrial developments. It is an environmentally friendly and sustainable solution. However, there are engineering pitfalls associated with the design and construction of plastic geocellular structures. The main pitfalls are associated with creep rupture of plastic structures, potential construction damage and the lack of care in wrapping the cells with filter fabric and backfilling procedure. As the scale and complexity of geocellular structures have significantly increased in recent years, guidance on appropriate design and construction methods has become more essential for these structures to be adopted as safe, yet economic and sustainable solutions.

In this paper, the author will describe his design and construction experience based on research associated with a court case on the damages associated with a major geocellular on-site stormwater detention project (approx. 8.5 Mega litres), and recent conversion of his backyard swimming pool to a 40,000 Litre rainwater harvesting tank. References on design and construction guidance will be described together with the author’s personal opinion on the use of partial factors in the economic design of geocellular structures.