Methods for Monitoring and Mitigating the Use of Chloride Deicers

Abstract

The winter roadway operations and maintenance community generates a breadth of data detailing the activity and performance of snowplows, deicing practices, and road conditions. While roadway ice clearing is a practical need for communities in temperate climates, one outcome of operations is the distribution of unnaturally high levels of dissolved solids, especially chloride, into environments which are hydraulically connected to maintained roadways and surfaces. The long-term buildup of chloride poses a threat to ecological integrity of freshwater systems. Salt also hastens the oxidation of metals used in the built environment, especially high-iron alloys. A 2007 study of the Twin Cities Metropolitan Area estimated that over a 5-year study period, 70% of road salt applied annually was retained in the landscape or infiltrated to deep groundwater. This research examines the road salt mass balance on a finer scale both spatially and temporally. Continuous monitoring of surface runoff was conducted in a small residential watershed using a novel approach. The results are paired with an analysis of snowplow asset tracking data to estimate what proportion of the total salt added to the catchment in the two-year study enters directly into the stormwater conveyance. Results are followed by a critical discussion of current research and considerations for future research.