Influence of Modern Stormwater Management Practices on Transport of Road Salt to Surface Waters

Abstract

Application of road salts in regions with colder climates is leading to ground and surface water contamination. However, we know little about how modern stormwater management practices affect the movement of road salt through urban watersheds. We investigated groundwater contamination and transport of road salts at two stormwater ponds in Baltimore County, Maryland. In association with the ponds, we documented a plume of contaminated groundwater that resulted in Cl loadings to the adjacent stream of 6574 to 40 008 kg Cl per winter, depending on winter snowfall. We also monitored Na and Cl ion concentrations and the temporal dynamics of conductivity at a range of stream sites in watersheds with and without stormwater management ponds. Streams draining watersheds with stormwater ponds had consistently higher conductivities and Cl concentrations during base flow conditions and often exhibited greater peaks in Cl and conductivity associated with winter storms and subsequent melting events, despite the degree of watershed development. Our results indicate that modern stormwater management practices are not protecting surface waters from road salt contamination and suggest they create contaminated plumes of groundwater that deliver Cl and Na to streams throughout the year.

Co-Design of Engineered Hyporheic Zones to Improve In-Stream Stormwater Treatment and Facilitate Regulatory Approval

“…Roseen et al [50] found that frost penetration had a negligible impact on most BMPs performance; Snodgrass et al [53] conclude that green infrastructure BMPs cannot treat road salts and instead advocate for source controls.…”

Influence of Multiple Environmental Factors on Organic Matter Chlorination in Podsol Soil

“…Hence, it is possible that chlorination rates can be influenced by changing pore water Clconcentrations and ionic strength such as during dry or wet periods and in areas with anthropogenic Cladditions to the soil, e.g. from road salt 37,38,39 .…”

Urban Stormwater Characterization, Control and Treatment

“…For example found that while denitrification rates were higher in watersheds with LID practices (constructed stormwater wetlands and restored riparian areas), methane (CH4) emissions were also higher than in non-LID watersheds. Elevated chloride and conductivity were detected in stream baseflow and surface runoff downstream of stormwater infiltration basins, likely due to chloride enriched groundwater plumes originating from these stormwater controls (Snodgrass et al, 2017). Another useful tool was developed by Warsta et al (2017) to automate watershed delineation and characterization as part of building SWMM models.…”