In situ performance of biofiltration systems is typically assessed via monitoring campaigns lasting upwards of a few years. However, long-term performance monitoring is also needed, since bioretention soil media (BSM) is expected to have a useful life measured in decades without the need for replacement. This presentation assesses the ability of high-rate biofiltration systems (designed at infiltration rates of 100 inches per hour or greater) to provide consistent water quality and hydraulic performance at the decadal time scale with standard maintenance. Contech Engineered Solutions LLC has continuously evaluated water quality performance at three different high-rate biofiltration sites via third-party field sampling and laboratory analysis. All sites utilize Filterra® Bioretention Systems, a proprietary biofilter that shares pollutant removal processes with conventional bioretention but has a much higher design infiltration rate and a footprint that is typically less than 10% the size of conventional bioretention systems. The study sites represent different sizes, ages, and land uses receiving regular maintenance. Monitoring duration varied by site, ranging upwards to 13 years. Hydraulic evaluation assessed changes in hydraulic capacity over time. Media profile composition and plant growth progression assessed changes in system dynamics. Filterra continues to meet or exceed performance expectations, suggesting that routine maintenance is adequate to maintain design functionality long-term without replacement of the BSM. Sampling methods and results will be presented for hydraulic capacity, component evaluation and parameters of interest including TSS, nutrients and metals. Recommendations will be made for ensuring long-term water quality compliance, focusing on providing proper and timely maintenance.
