Road Salt in Maine: An Assessment of Practices, Impacts and Safety

The Road Salt in Maine: An Assessment of Practices, Impacts and Safety report presents the results from a research project by a team from the University of Maine, in cooperation with the Maine Department of Transportation (MaineDOT), that examines the use of road salt in Maine for winter travel safety. It summarizes winter maintenance practices, changing winter weather patterns, environmental impacts and costs, and winter road safety. This report follows a 2010 report (Rubin et al. 2010).

In the 10 years since our previous study, research in Maine and nationwide shows increasing salt
accumulation in both freshwater and groundwater environments. The MaineDOT requested this
study to more closely examine the trends in Maine and the impacts we may experience from
warming winters and changing weather patterns. We collected data from MaineDOT, the Maine
Turnpike Authority (MTA), and Maine’s municipal governments on winter road maintenance
practices, materials (e.g., salt) and costs.

We look at road safety in terms of factors that impact crashes in winter driving. To analyze road
safety and the relationship between winter weather and crashes, we examined data from all
police reported crashes from 2015–2019 in Maine. This is matched with daily weather data from
weather stations throughout the state.

We examined the relationships between wintertime weather and salt use in Maine over the past
three decades. Recent changes in the weather and climate patterns are assessed for their long‐
term trends. A suite of seasonal weather indices used by transportation management agencies are
analyzed for sensitivity to weather/climate patterns and potential use for planning and decision‐
making linked to salt use and application. The analysis provides a quantitative basis to understand
the salience of changing winter weather patterns to salt use and transportation infrastructure
planning and decision‐making. Our analysis offers insights regarding future expectations in a
changing climate.

The evaluation of environmental impacts of from salt use is based on geospatially distributed
records from well testing to assess the prevalence of chloride contamination in groundwater wells.
We derive estimates of the risk of chloride contamination at the town level, as well as their
potential relationship with soil hydraulic conductivity, presence of faults in bedrock and other
location specific factors. We provide some insight into what to expect in the future given climate