University of Vermont
Co-Authors: E. Roy, D. Rizzo, A. Torizzo
Phosphorus (P) is a limiting nutrient in freshwater systems, including Lake Champlain. P continues to be considered a top constituent of concern due to eutrophication. The plurality of P runoff entering the lake from Vermont comes from agriculture, however, urban systems contribute more P per acre. The focus of this study is to increase stormwater filtration with green stormwater infrastructure (GSI), decreasing P loads to downstream waters. Subsurface horizontal-flow gravel wetlands are increasingly being installed in the region for this purpose. While numerous studies have investigated similar systems for wastewater treatment, information is lacking on their P removal performance in the context of GSI. Additionally, the effects of chloride (from deicing salt) on gravel wetland performance remain poorly understood. The main concerns of chloride are the effect on wetland biology (namely plants) and potential clogging. We aim to fill these knowledge gaps by testing a number of locally sourced gravels and fabricated “wetland muck” materials to determine their effects on P dynamics when included in gravel wetland GSI designs. Furthermore, local native wetland plants will be used in a greenhouse bioassay to determine the individual species chloride tolerance. Results from our study will inform future stormwater SGW design in Vermont and elsewhere, including guidance on the specifications for materials used.