The Michigan Department of Transportation (MDOT) has started a pilot project that will explore a liquid alternative to road salt. If it proves cost- and conditions-effective, this approach could save substantial amounts of money, help reduce the amount of salt getting into the environment and protect the ecosystem year-round.
Salt (sodium chloride) works by lowering the freezing point of water. When road salt is spread before ice forms or snow falls, it creates a saltwater mix that keeps roads passable when temperatures dip below freezing. While road salt is a vital tool for commerce and human safety in colder months, this saltwater mix inevitably runs off into sewers, which flow into streams or infiltrate into groundwater, raising the salinity in freshwater systems.
A 2017 study that included researchers at Canadian and US universities found that with current trends, many North American lakes could exceed the US Environmental Protection Agency’s salinity threshold for aquatic life within 50 years. Salt can’t be flushed out of water in normal treatment plants, either. Beyond the broader environmental concerns, the added salt entering groundwater can hurt farmers who grow crops like blueberries that are sensitive to salinity, said Mark Geib, a transportation systems management and operations engineer with MDOT.
This isn’t just a winter problem, either. A recent study out of the University of Toronto found that road salt contaminated at least four rivers and creeks around the city even during the summer months: the Don and Humber rivers and the Etobicoke and Mimico creeks. And 89 percent of samples came back above chronic or acute levels of contamination (set by the Canadian government as 0.12 and 1 gram per liter, respectively). Samples with the highest concentrations were from the urban core of the city. The samples were all taken during periods with no rainfall to get as close to base water flows as possible. These summer streams were found to have chloride ranges between 0.2-1.1 grams per liter. For reference, the salinity of water in the ocean is between 33-37 grams per liter and brackish water typically found where rivers enter the sea can range between 0.5 and 35 grams per liter.
This may not seem like a lot of salinity at first glance, but the researchers believe this is enough to negatively affect two-thirds of the living creatures in the waters around Toronto, that have evolved for very low to nonexistent levels of salt in the water. While some species may be able to acclimate to these increased levels of salt in the water, the Toronto study notes that this isn’t universal, and several endangered species of mussels and fish that live in the area, like the redside dace, may not have much suitable habitat elsewhere that they can access.
Between the price of road salt and environmental concerns, governments have been exploring alternatives. Conservation Ontario issued guidance in 2018 for the province and its communities to identify vulnerable or sensitive areas and methods to reduce salt usage without compromising public safety. Local communities in both countries have explored other options as well, such as agricultural products like beet juice, or releasing rock salt alongside a brine to keep it from bouncing around on the pavement. The pilot approach by MDOT is based on similar work in Wisconsin, where a liquid brine is made ahead of time and sprayed onto road surfaces, instead of spreading solid rock salt.
“We thought if (we, like Wisconsin) could provide a great level of service and save 30-40 percent in the amount of salt you use, it’s a win-win all around the block,” said Geib.
The pilot project got underway in the winter of 2020 in Montcalm County (located between the cities of Lansing, Big Rapids and Mount Pleasant), where MDOT partnered with the Montcalm County Road Commission to maintain state roads.
Next winter, MDOT also will be piloting these liquid approaches in Mount Pleasant and Grand Ledge garages, said Justin Droste, region support engineer with MDOT and one of the heads of the study. The final report on this pilot project is due in June 2025, and Droste said that MDOT will be testing the approach in every winter season until then to ensure that the department has a broad understanding of how this liquid approach works under a variety of circumstances and seasons.
Additionally, a 2019 study published in the Environmental Science and Technology journal found that using brine instead of solids like rock salt reduced the amount of chloride overall reaching urban streams by an average of 45 percent.
In the law passed by the Michigan legislature in December 2020 that authorized this pilot project, MDOT also will be reviewing the effectiveness of adding in agricultural byproducts such as beet juice, which helps deicers remain effective at lower temperatures. Geib said MDOT has used beet juice products in the past. The pilot will be looking further into additional agricultural byproducts in the pilot to get as large a cross-section of options as possible. Geib notes there is an environmental and monetary cost to these supplements, however, and the final recommendations coming out of the pilot will depend on how much the efficacy of the liquid chloride is improved.
Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.