Identification of Salt-Vulnerable Areas: A Critical Step in Road Salt Management

Northern communities repeatedly encounter snow and ice conditions forming hazardous environments on road networks during winter months. Millions of tons of road salts are applied in urban watersheds in North America for winter deicing operations. Although chlorides are nontoxic to humans, it has been shown to create toxic environments in aquatic habitats. Increasing numbers of agencies involved with winter road maintenance are working proactively to develop salt management plans that minimize the adverse environmental effects of deicing chemicals. However, the attention that has been given to another important aspect of developing a salt management plan, the identification of salt-vulnerable areas, seems to be lacking. Too few agencies attempt to identify areas vulnerable to road salts within their jurisdictions for better use of best management practices (BMPs). The low rate of participation of road agencies’ work on salt-vulnerable areas seems to be due to lack of clear guidelines, proper understanding of the process, and the perception that the process may require expensive and advanced data collection and analysis. Because the effectiveness of salt management practices is highly visible in salt-vulnerable areas, it is prudent to put more effort into identification of the vulnerable areas and take action to reduce the risks. This paper presents a risk-based approach for identification of salt-vulnerable areas considering salt application rates at varying land use types, transport pathways, and exposure to receptors. A fuzzy set methodology will be used to estimate the risk associated with the exposed receptors. Transport pathways include both surface and subsurface conveyance of chlorides. This paper also highlights the significance of the contribution by private contractors on salt loadings in urban areas. This risk-based approach would help provide the opportunity to prioritize implementation of management practices in the salt-vulnerable areas. The approach presented is based on research work at Highland Creek Watershed in Toronto, Canada, and Hanlon Creek Watershed in Guelph, Canada. Part of the research work done at Highland Creek and Hanlon Creek Watersheds was monitoring at different land use types by contractors with varying winter maintenance practices. Currently there are no guidelines with respect to salt application rates in parking lots, and as a result the quantity of applied salts tends to vary based on land use and contractor. For example, a contractor who is responsible for a commercial parking lot may apply more road salts then a contractor who is responsible for an industrial parking lot. The different perceived risks associated with the varying land use typically plays a major role in the amount of salt applied in an area, and this concept must be accounted for when identifying salt-vulnerable areas. In addition to the evaluation of the potential for reducing and optimizing salt application rates, other BMPs are identified and assessed. Lining the vegetated roadside ditches to minimize groundwater contamination and the use of capture and controlled release of chloride-laden snowmelt in storm water ponds to reduce chloride peaks in stream water are presented as possible BMPs.

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