Comparing the Hydrologic and Water Quality Performance of Bioretention and High Rate Biofiltration at a Marina in Huron, Ohio

Abstract Submission: An unintended consequence of urbanization is increased anthropogenic pollutant generation that is conveyed to waterways via stormwater. This has encouraged the development of novel stormwater control measures (SCMs) whose performance should be evaluated relative to established practices. This study compares the hydrologic and water quality performance of a retrofitted bioretention cell (BRC) and a high rate biofilter (HRBF) treating similar catchments and constructed side-by-side at a marina in Huron, Ohio. The HRBF media consisted of 60% fine gravel which provided infiltration rates purported to be 40 times greater than that of BRCs. Monitoring was carried out for a total of 24 months and paired stormwater samples were collected at the inlet and outlet of the BRC (n = 12) and HRBF (n = 16) to compare water quality before and after treatment. The BRC significantly reduced both overall runoff volumes and peak flow rates by 26 and 79%, respectively, while the HRBF achieved only 1.4 and 21%, respectively. The BRC and HRBF provided significant reductions of total suspended solids (TSS) concentrations of 92 and 65%, respectively. For every pollutant studied, including nutrients, TSS, and heavy metals, the efficiency ratio of the BRC was greater than that of the HRBF, suggesting the BRC was more effective at retaining pollutants. The BRC reduced annual loads of TSS by 93% and loads of Cu, Pb, and Zn of 86, 85, and 85%, respectively; annual load reductions for the HRBF were less than those for the BRC in all cases. The larger surface area of and greater storage provided by the BRC resulted in significantly better runoff reduction and water quality improvements than the HRBF; however, these SCMs may be the only option for implementation at ultra-urban sites, and therefore serve a critical role in the toolbox of stormwater managers.

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