Effects of Road Salt Cations on Dissolved Metals in a Constructed Stormwater Control Measure

Considerable amounts money and resources are spent managing urban stormwater runoff. Stormwater control measures (SCMs), like water retention ponds and basins, are typically constructed to manage stormwater runoff in urban settings. These SCMs have historically been designed for short term water retention to prevent flooding. Generally, SCMs are also relied on to “treat” stormwater and remove contaminants. A new generation of SCMs (NGSCMs) are being constructed to look and act like natural wetlands so natural biological processes improve water quality. In many cases these NGSCMs are not evaluated on how well they improve water quality. The objective of this study is to assess the impact of a recently completed NGSCM on road salt and metals in runoff. We hypothesize that increased road salts cause dissolution of Cu, Zn, Pb, Fe, Ni, and Mn from suspended sediments and into surface water. Preliminary results demonstrate the NGSCM receives high salt loads that are attenuated along the system’s flow path. This suggests that the wetland is retaining salt, preventing discharge to downstream systems. Our results will contribute to broader understanding of the efficacy of NGSCMs for water quality improvement