Though research on bioretention has been steadily growing, studies are still predominantly on completed new bioretention systems that are less than 3 years old. It is unknown whether bioretention cells’ engineered media continues to detain and infiltrate intended runoff volumes as systems age. Bioretention media can become clogged with sediment, or the media can compact as it settles, reducing hydrologic performance over time. In this study, we survey and sample 21 Ontario bioretention cells that have been operational for at least 3 years. We measured soil properties such as hydraulic conductivity and field capacity, surveyed the cells to determine their volumetric capacity, and visually observed presence of clogging, plant die-off and saturated conditions. Measured soil parameters were then compared to the original design parameters and to initial conditions to determine if the bioretention media has degraded over time. All of the mature bioretention cells had infiltration rates above the recommended minimum (25 mm/hour). Infiltration rates remained unchanged at most sites but 1/3 had notable increases ranging from 20 -50%. The sand content across all sites was between 70 and 90%, which is consistent with Ontario guidelines for bioretention media. Overall, most bioretention cells continue to perform well from a hydrologic perspective, and infiltration capacity is maintained.

How long will they last? Performance Assessment of Mature Bioretention Systems in Ontario, Canada

The International Low Impact Development Conference highlights interdisciplinary practice, research, and implementation of Low Impact Development (LID), Green Infrastructure (GI), Sustainable Urban Drainage Systems (SUDS) and Water Sensitive Urban Designs (WSUD). The focus of this conference was on using our past and present understanding of LID to tune management programs, design practice, and operation and maintenance into the future.



NOTE: Due to the COVID-19 pandemic, this conference was held virtually. The proceedings have been published to provide readers access to the information that was presented.

[Paper Proceedings](https://doi.org/10.1061/9780784483114)

Conference DOI: https://doi.org/10.26226/m.6317827c362f600015b4eb73