Image of salt on road

Road Chemicals

Dear Sustainability Sam,

What happens to all the road chemicals used in winter months to keep the roads clear?


Dear Brian,

Thanks for the question! As we all are aware, Minnesota winters are harsh and to keep the roads safe and clear for transportation, counties and municipalities use a combination of anti-icing agents, de-icing agents, and grit materials to keep the roads in passable condition. Anti-icing agents are applied pre-storm to prevent ice from bonding to the pavement. De-icing agents are used post-storm to break up ice and snowpack and to melt black ice patches. Anti- and de- icing agents are largely made up of chemicals called chlorides, which we commonly refer to as road salt. Grit materials are used to create traction and are largely sand. Sand does not melt ice or snow and is easily displaced along the road side, so counties and municipalities rely primarily on the chlorides.

Unfortunately, the chlorides used to melt ice and snow from the roads runs off into storm drains which carry the runoff into Minnesota ‘s wetlands, lakes, streams, and groundwater aquifers. The Twin Cities metro area uses abound 365,000 tons of road salt each year and 78% of that road salt ends up in our local waterways. The Minnesota Pollution Control Agency (MPCA) explains that this is problematic for three reasons. First, salt in our groundwater affects the taste and healthfulness of our drinking water (75% of Minnesotans rely on groundwater for their drinking water). Second, salty water threatens our freshwater fish and other aquatic life. High amounts of chloride in water can be toxic to fish, aquatic bugs and amphibians and can be detrimental to the root systems of trees and plants. Lastly, there is no easy way to remove chlorides from water. And, it takes only small amounts of chlorides to pollute water—one teaspoon of road salt will contaminate 5 gallons of fresh water.

The MPCA is seeing the impact of road salt in Minnesota’s waterways. Their website reports that 27% of monitoring wells in Twin Cities shallow aquifers had chloride concentrations that exceeded EPA guidelines. And 30% of the monitoring wells had chloride levels that exceeded their water quality standards.

The MPCA works hard to balance the safety of the roadways with the impact of road salt on our waterways. Twice a year, all Minnesota roads are swept and cleaned in order to minimize the amount of pollutants and debris that enter our waterways through the storm drains. Additionally, MPCA has implemented a Smart Salting Program which educates snow plow operators how to significantly reduce salt use in winter road maintenance. Their program has been shown to reduce salt use by between 30% and 70%.

What can you do to help? Educate yourself on proper salting techniques by referring to this excellent synopsis on homeowner snow removal:


Sustainability Sam