Study of De-icing Salt Accumulation and Transport Through a Watershed

Principal Investigator:

William Herb, Research Associate, SAFHL - Hydraulic Lab

Co-Investigator

Project Summary:

The accumulation of chloride in surface waters and groundwater from road deicing is a growing problem in many regions of the country, including the Minneapolis-St. Paul metro area. Research is ongoing to measure chloride concentrations in lakes, streams, and groundwater, and to develop methods to reduce chloride usage for pavement deicing. There is a lack of information, however, on how chloride is transported within watersheds, and the residence time of chloride in intermediate portions of a watershed (shallow groundwater, streams, wetlands). We propose to study the transport of chloride through surface and shallow groundwater in a metro-area watershed, to characterize chloride transport processes (surface runoff, infiltration, interflow), the seasonal timing of these processes, the residence time of chloride, and how year-to-year variations in weather influence chloride transport processes and the accumulation of chloride in a receiving lakes and wetlands. The results of the study can inform both future mitigation efforts and the monitoring of chloride accumulation. Better knowledge of chloride transport and accumulation time scales can inform future efforts to reduce accumulation in impaired water bodies. Guidance can be provided to city, county and state transportation agencies to focus efforts for reducing deicer usage in the most beneficial areas, and how different road drainage systems influence chloride accumulation. The study results will also provide guidance to the MPCA and watershed districts for monitoring chloride accumulation - how often, where, and when chloride sampling should be done to measure and predict impairment.

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