bioretentioner

A bioretentioner is a vegetated stormwater treatment system designed to filter pollutants from urban runoff and to encourage infiltration. It is a form of bioretention, often implemented as a shallow, landscaped basin or trench, commonly referred to as a biofiltration bed, rain garden, or bioretention cell. The goal is to improve water quality and reduce stormwater volume.

Operation: runoff first passes through pretreatment to remove coarse debris, then enters a planted media bed composed of sand, soil mix, and organic matter. As water percolates through the media and plant roots, physical filtration, adsorption of contaminants, microbial processes, and plant uptake remove sediments, nutrients, metals, and hydrocarbons. Water either infiltrates into the underlying soil or is collected by an underdrain and conveyed to the drainage system.

Typical design features include a surface landscape, an underlying drainage layer, a sand or soil media layer, a planting layer, a mulch cover, and an outlet structure or underdrain system. Media depths commonly range from 0.5 to 0.8 meters, with variations based on climate, soil, and intended hydraulics. Pretreatment forebay is often provided to extend life.

Applications include parking lots, road right‑of‑ways, commercial developments, and residential campuses. Bioretentioners help reduce peak flows, improve water quality, and provide aesthetic and habitat benefits. Limitations include lower performance in poorly infiltrating soils, high water tables, or under heavy sediment loads, and ongoing maintenance needs to prevent clogging.

Maintenance involves regular inspection of surface grading, sediment removal, mulch replacement, vegetation management, and cleaning of the underdrain and outlets. Long-term performance depends on proper design, construction quality, and consistent upkeep.