Integrated Stormwater Treatment at an Auckland Commercial Development
Project Objective
The client’s objective was to maximise land yield across a large shopping centre and adjoining carpark in Auckland, while meeting regulatory requirements and achieving robust water quality outcomes. Given the site’s commercial scale, space efficiency and high-performance treatment were essential.
Stormwater Strategy
To balance performance with spatial constraints, an integrated Green Infrastructure solution was selected. This approach delivered superior pollutant removal while aligning with modern, sustainable design standards.
Treatment Train Overview
The site was divided into two primary catchments, each with a tailored system to address both gross pollutant removal and fine filtration.
Catchment 1 – 32,371 m²
Cascade Separator™ CS6 (pre-treatment / Gross Pollutant Trap)
125m² Filterra® Bioscape® (bioretention for fine pollutant removal)
Catchment 2 – 39,243 m²
Cascade Separator™ CS6 (pre-treatment / Gross Pollutant Trap)
150m² Filterra® Bioscape®
The Cascade Separator™ removes gross pollutants, sediments, and floatables upstream, while the Filterra® Bioscape®provides high-performance bioretention, consistently removing TSS, nutrients, metals, and hydrocarbons.
LittaTrap™ Deployment
Key Outcomes:
Maintenance:
Filterra® Bioscape® is simple and low-cost to maintain, with a 6-monthly replacement for the mulch layer. This can be done by hand maintenance or by a vactor truck to suck up the mulch, and then a mulch blower to reapply the mulch.
Cascade Separator™ follows an inspect-to-maintain service, ensuring the system remains fully functional with minimal maintenance required between service intervals.
LittaTrap™ can be maintained by hand or by a vactor truck. Hand maintenance is simple; Lift the LittaTrap™, Tip out the LittaTrap™ into a rubbish bin and then simply replace the LittaTrap™ back into the drain.
Conclusion:
