Hydrologic and Water Quality Performance of Two Bioswales at an Urban Farm

Many postindustrial cities are transforming underused areas into urban agriculture, which presents unique stormwater management challenges. One way to manage runoff from urban agriculture is to use green stormwater infrastructure; however, to date, green stormwater infrastructure has largely been applied to treat runoff from impervious surfaces and its application to urban agricultural runoff is underexplored. This study seeks to fill this gap by monitoring two bioswales collecting and treating runoff from an urban farm in Milwaukee, WI. To do so, the influent and effluent at each bioswale was sampled and tested for total suspended solids (TSS), total phosphorus, and total nitrogen. Both bioswales were effective at reducing volume, peak flows, total phosphorus concentrations, and high concentrations of TSS ($>25\mathrm{mg}/\mathrm{L}$) but had mixed results in reducing total nitrogen concentrations and TSS at low influent concentrations ($25\mathrm{mg}/\mathrm{L}$). Large volume capture and exfiltration resulted in load reduction (median 98%) across all pollutants. Overall, this project demonstrates the feasibility of bioswales for reducing pollutant loads from urban farms, which may have different pollutant concentrations within stormwater runoff than other typical urban settings.