Filterra® Bioretention System

Filterra® is a popular green infrastructure solution for stormwater treatment for sites with limited space—such as urban car parks, streetscapes, and commercial or residential developments. It offers biofiltration in just 10% of the footprint of traditional rain gardens.

Stormwater enters through a curb inlet or pipe into a concrete container, designed with an energy dissipator and mulch layer that minimizes scouring. Water then percolates through engineered filter media—composed of aggregate and organic material—where pollutants like heavy metals, nutrients, fine sediment, hydrocarbons, and total suspended solids are immobilized, decomposed, or incorporated into plant and microbial biomass. Clean water is then collected by an underdrain system and discharged into the stormwater network. Excess water from heavy inflows may bypass the system to a downstream outlet.

Routine maintenance keeps the mulch layer and filter media working as intended, allowing water to drain freely through the system. Without regular care, sediment and debris can build up and clog the unit, reducing its ability to capture pollutants and increasing the risk of flooding. By keeping your Filterra® system in top condition, you help maintain strong environmental performance, support groundwater recharge, and ensure ongoing compliance with council requirements.

At Dutton Stormwater, we offer comprehensive maintenance for Filterra® systems across New Zealand. Our team inspects the unit, removes litter and mulch debris, replenishes mulch layers, checks plant health, and ensures the underdrain is operating correctly.

Filterra® systems typically require maintenance every six to twelve months, depending on site-specific conditions like sediment load, local vegetation, and pollutant sources. After each visit, we provide a tailored maintenance report, complete with photos and recommendations to help keep your Filterra® operating effectively and meeting consent requirements.