It’s time to put our waters on a low-salt diet
We use salt to manage snow and ice in Minnesota, but too much can irreparably harm our lakes and streams. It's time for Minnesota to go on a low-salt diet. (Photo Minnesota Pollution Control Agency.)
Winter is coming! Nope - not Game of Thrones Season 9 (thankfully) - but actual Minnesota Winter. And that means salt season!
Chloride pollution in Minnesota’s waters has been making headlines for years, as salt levels in our waters have increased with real risks to aquatic life.
Chloride is a permanent pollutant; it does not degrade over time in our environment. As a result, just 1 teaspoon of salt in enough to permanently pollute 5 gallons of water!
Where's all this salt coming from?
Chloride is the mineral in salt that occurs naturally at low levels in our environment, but at high concentrations, it can be toxic to aquatic life.
Winter deicers are the primary source of excess chloride to Minnesota’s waters. Salt is applied to roadways, sidewalks, parking lots and driveways to reduce the freezing point of water, helping to prevent ice buildup and improve traction.
About 350,000 tons of deicing chemicals are applied just in the metro area each year, and most of it (about 78 percent) is retained in local surface and groundwater. Statewide, an estimated 730 million pounds of salt is applied to roadways each year — likely well more than is needed to protect public safety.
Globally, salting is becoming more common. By some estimates, salt use by U.S. road maintenance departments has skyrocketed from 0.16 tons/year in 1940 to nearly 20 million tons per year today.
The other major source in the metro area (24%) is from water softeners, which use chloride to soften water. In many communities, that softening salt is eventually carried to wastewater treatment facilities which are not designed to remove chloride before discharging treated effluent into our waters.
Impacts on our environment
As we noted in the 2016 State of the River Report, chloride levels in the metro Mississippi River increased by 81% in recent decades. While river levels are still low, many nearby lakes and tributaries aren’t so lucky. Of tested metro area water bodies, around 40 are impaired for excess chloride with another 40 close to exceeding state standards.
And this isn't just a Minnesota problem. A recent study of 371 lakes in North America found chloride concentrations rising in more than a third of lakes tested.
Local monitoring data also show high chloride concentrations in area groundwater. Twenty-seven percent of the metro area sand and gravel wells exceed federal guidelines for chloride. In Madison, Wisconsin, high chloride levels in groundwater are beginning to make drinking water salty, with concerns that the water may become too salty for most users within 15 to 20 years.
Salt can also harm plants, lake mixing patterns/ecology, pets (especially pet paws) and wildlife.
Chloride can also negatively affect infrastructure (bridges, roads, parking ramps, etc.) and vehicles due to corrosion. By one estimate, a ton of road salt does about $1,500 worth of damage to bridges, vehicles and the environment.
Since it's not feasible to remove chloride from our surface waters or groundwater, the only solution is to reduce chloride pollution before it reaches our creeks, lakes and rivers - an approach we often call "source control".
The win-win: better chloride management
The Minnesota Pollution Control Agency is implementing a chloride management plan across the metro area. The plan emphasizes smart salt trainings focused on using the least amount of salt possible without compromising public safety.
This strategy is a winner for the environment and infrastructure, as well as our pocketbooks.
After the trainings, the University of Minnesota reduced salt use by more than 40 percent and sand use by 99 percent. This saved $55,000 in just the first year of smarter salt usage.
The City of Waconia has saved $8,600 a year in reduced salt costs, and reduced salt use on trails and sidewalks through improved salt application. The City of Prior Lake has reduced salt usage by 42 percent since 2005 (even while increasing lane miles by 7 percent) with a minimum savings of $2,000 per snow event, while the City of Richfield has cut salt use in half. These same strategies have helped the Minnesota Department of Transportation save money by using less salt.
A legislative solution
FMR is working with a diverse coalition of organizations to push legislation that would help reduce chloride use statewide through training, liability protection for private de-icing applicators, and funding to research and develop more eco-friendly alternatives.
FMR River Guardians have been weighing in to support this legislation. (If you're not one already, we encourage you to sign up! River Guardians are also invited to special events, including happy hours (now virtual), where we discuss important legislative and metro river corridor issues.)
What you can do now
We all probably use way too much salt on driveways and sidewalks. According to Wisconsin’s Be Salt WIse! Campaign, just a coffee mug of salt is enough to treat an entire 20-foot driveway or 60-70 feet of sidewalk. Please salt accordingly!
Other steps you can take to reduce chloride pollution include:
- Shovel early and often: Clear walkways and other areas before the snow turns to ice. The more snow you remove manually, the less salt you will need later. Many people find that frequent sweeping with an outdoor broom can be faster and more effective than shoveling.
- Switch: Basic rock salt only works down to about 15 degrees. Below that, normal salt won’t help. Switch to sand for traction or use alternative (but more expensive) ice-melters that work at lower temperatures. While alternative salts still contain chloride, at least they will work at lower temps:
- Magnesium chloride: -10º F
- Potassium acetate: -15º F
- Calcium chloride: -20º F
- Sweep up excess: Collect excess salt before it washes into stormdrains!
- Be hard on salt, soft on water: If you have a home water softener, make sure you use less than a bag a month. If you’re using more, it's time for a tune-up, or to consider replacing your system with a high-efficiency model.
- Slow down: While we’ve come to expect clean and dry roads year-round, the risks to infrastructure and our environment (and sometimes the costs) make that increasingly unrealistic in winter. Careful, slow driving during wintery conditions can protect public safety and make the most of the salt on our roads.
Learn more from our friends at the Mississippi Watershed Management Organization, and consider sharing this page or video with your friends on social!