Minnesota has a growing salty water problem that threatens its freshwater fish and other aquatic life. Chloride from both de-icing salt and water softener salt gets into lakes and streams, and groundwater that supplies drinking water. It takes only one teaspoon of salt to permanently pollute five gallons of water. Once in the water, there is no feasible way to remove the chloride.
When snow and ice melts, the salt we spread on icy roads, parking lots, and sidewalks flows with it into storm drains and our lakes, streams, wetlands, and groundwater. An estimated 365,000 tons of road salt is applied in just the Twin Cities metro area each year. A study by the University of Minnesota found that about 78% of salt applied in the Twin Cities for winter maintenance is either transported to groundwater or remains in the local lakes and wetlands. In the Twin Cities and other communities across Minnesota, local partners are addressing this problem by using sand and other strategies to keep winter roads safe while using less salt for de-icing.
People soften their water to make water heaters operate more efficiently, prevent hard water spots on dishes, and make soaps lather more. In most communities, salty brine from water softeners drains to municipal wastewater treatment plants that are not designed to remove salt from wastewater, so the salt passes through to a lake or stream.
Human health and environmental concerns
Drinking water — Salt has contaminated groundwater in some areas of the state, and 75% of Minnesotans rely on groundwater for drinking water. Excess salt can affect the taste and healthfulness of drinking water. Twenty-seven percent (20%) of monitoring wells in the Twin Cities metro area's shallow aquifers had chloride concentrations that exceeded EPA drinking water guidelines, and 30% of Twin Cities wells had chloride concentrations that exceeded the water quality standard.
Fish and aquatic bugs — High amounts of chloride are toxic to fish, aquatic bugs, and amphibians. Chloride can negatively affect the fish and insect community structure, diversity, and productivity, even at lower levels.
Plants — Road salt splash can kill plants and trees along the roadside, and plants that take up salty water through their roots can also suffer. Chloride in streams, lakes, and wetlands harms aquatic vegetation and can change the plant community structure.
Soil — Salt-laden soil can lose its ability to retain water and store nutrients and be more prone to erosion and sediment runoff (which also harms water quality).
Pets — Salt can sicken pets who consume it, lick it off their paws, or drink salty snow melt/runoff. It can also irritate their paw pads.
Wildlife — Some birds, like finches and house sparrows, can die from ingesting deicing salt. Some salt-sensitive species are particularly at risk.
Infrastructure — Chloride corrodes road surfaces and bridges and damages reinforcing rods, increasing maintenance and repair costs.
Monitoring, reporting, and regulations
Road salt runoff tends be a problem in developed areas where there are many roads and other paved surfaces. Chloride in wastewater appears to be a problem in almost 90 Minnesota communities, most in the southern and western parts of the state. MPCA water monitoring shows that salt concentrations are increasing in lakes, streams, and groundwater around the state.
Fifty Minnesota lakes and streams have chloride levels too high to meet the standard designed to protect fish and other aquatic life. An additional 75 water bodies have chloride levels near the standard. Chloride toxicity is a suspected stressor to aquatic life in many waterways, including two trout streams in the Duluth area. Chloride is stressing aquatic life in a stream in the Cannon River Watershed in southern Minnesota; an upstream wastewater treatment facility is the likely source.
- Minnesota's chloride conditions – Map showing waters that have been evaluated for chloride by the MPCA. Bodies of water without a colored label do not have chloride data available.
Track salt pollution in your area
The Izaak Walton League of America offers its Winter Salt Watch program to Minnesota residents. Communities can partner with the organization to bring the program to your area. Participants can request a free kit that helps them find out whether salt pollution is a problem in local streams, lakes, and wetlands. See how Minnesota organizations are utilizing this program:
Smart Salting training
Our Smart Salting training helps organizations that apply road salt improve operator effectiveness and reduce chloride pollution, while keeping roads, parking lots, and sidewalks safe. Participating organizations have been able to reduce their salt use by 30% to 70%, and the training has been shown to prevent chloride contamination in bodies of water. Learn more:
Chloride reduction grants
The MPCA offers grant funding in selected communities to help reduce chloride pollution. In each grant round, funds are awarded to one organization to lead an effort with members of multiple communities or a single community along with local and state experts. The goal of the grant program is to help communities work with residents, local businesses, institutions, and industries to identify chloride sources and decrease or eliminate salt use to reduce impacts in local water resources. Sign up for Smart Salting Update to be notified when grant funding is available.