Strategies to Mitigate the Impacts of Chloride Roadway Deicers on the Natural Environment

The final report was produced as TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 449: Strategies to Mitigate the Impacts of Chloride Roadway Deicers on the Natural Environment. It documents the range of methods, tools, and techniques used by transportation agencies to minimize the environmental impact of chloride-based roadway deicers.

It can be retrieved from the National Academy of Sciences at: https://www.nap.edu/catalog/22506/strategies-to-mitigate-the-impacts-of-chloride-roadway-deicers-on-the-natural-environment

The goal of this project is to document the range of strategies used by transportation agencies to minimize the environmental impacts of chloride roadway deicers, lessons learned, and knowledge gap and future research.

The potential deleterious effects of deicing chemicals on the natural environment, vehicles, and the transportation infrastructure have long been recognized. The degree of deicer environmental impact is related to the quantities of chemicals ejected into the environment. When chemical deicing was in its youth, the benefits were typically very obvious in comparison to the often more obscure environmental costs. Over time the use of chemical deicers has grown exponentially due to its recognized effectiveness coupled with steady growth in urbanization and increasing societal expectations for maintaining high levels of highway service and uninterrupted commerce throughout the winter. As deicer use has increased, so has awareness of associated environmental impact, and a number of recent studies have raised concerns about the growing indications of deicer related environmental impacts There is a need to identify current and effective practices for reducing the environmental costs of deicers. Unfortunately there is not one simple solution. Environmental impacts of deicers are highly variable and dependent on the nature of the adjacent environment- urban, rural, mountainous, adjacent to water bodies, type of water body, etc. Therefore a “one-size-fits-all” approach will not suffice. Instead a “toolbox” of useful technologies and current practices may be required. Thus, there is need for a synthesis to be made that documents current practices of known technologies for mitigating chloride deicer environmental impacts, their various pros and cons, costs, practicality, unknowns or ambiguities, circumstances under which they are most and least effective, and best estimates of degrees of effectiveness.