Underperformance Assessment Framework for Bioinfiltration Systems

Abstract

Stormwater management practices (SMPs) are increasingly being implemented in urban environments to provide water quality and quantity benefits to municipalities. Bioinfiltration systems (e.g., rain gardens) are a common type of SMP that rely on the infiltration of stormwater into the soil to capture and filter stormwater and make water available to plants. Most municipalities require that the maximum time for the ponded water to infiltrate (drain-down time) does not exceed 24–72 h after rainfall. If there is sustained ponding beyond this time period, the bioinfiltration system is considered to be underperforming. Management of such underperforming systems often involves substantial and costly restoration efforts (e.g., reconstruction, soil replacement), forfeiting infiltration benefits to pivot to a bioretention or other SMP approach, or even in some cases abandoning the SMP. A systematic forensic investigation to identify the specific cause(s) of underperformance may allow for more targeted, effective, and economical rehabilitation of the underperforming SMP. In this study, an underperformance assessment framework (UAF) was developed and applied to five underperforming bioinfiltration sites to identify the causes of extended ponding and inadequate water quantity removal relative to design standards. Once likely causes of underperformance were identified, targeted rehabilitation techniques were recommended to restore system performance. Through the use of this comprehensive and systematic tool, isolated SMP components can be identified and rehabilitated, thus avoiding the entire system overhaul, minimizing restoration costs, and avoiding the recurrence of similar issues. Future benefits resulting from the increased knowledge of bioinfiltration systems gained by using this tool include improvements to system design and maintenance, thus ensuring the sustainability and resiliency of urban SMPs.