State asks Minnesotans to weigh safety, environment when salting slick surfaces

An estimated 445,000 tons of chloride-containing salt is scattered across Minnesota every year.

As a region known for its serene outdoor attractions, including hundreds of lakes, those literal tons of salt are leaving the freshwater lakes and ecosystems across the state in a crisis.

Make no mistake, salting is a tried-and-true method to keep roadways, sidewalks and driveways clear of snow and ice. It reduces slips, falls and vehicle collisions by up to 85%, according to the American Highway Users Alliance. Not to mention the road crews that work hard to keep the state’s 12,000 miles of roadways safe for daily commutes.

However, the Minnesota Pollution Control Agency is encouraging Minnesotans to do their part this winter with a “less is better” strategy for salting surfaces and by using other tools to get the job done. Salt is commonly overapplied and sends chloride into surface water, lakes, rivers and streams.

“Chloride from de-icing is one of the largest contributors to a growing salty water problem in Minnesota. It only takes one teaspoon of salt to permanently pollute five gallons of water,” an MPCA release said. “Once the chloride is in our water it’s there for good. Not only does salt damage our infrastructure, but it harms the environment, freshwater fish and other aquatic life.”

During his past nine years teaching at Bemidji State University, the road salt dilemma has been a frequent topic of study for Environmental Studies Professor Carl Isaacson. He dedicates much of his teaching and research to maintaining and improving water quality along with empowering his students and people across Minnesota to understand the problems at hand and make effective changes in how lakes and rivers are being treated.

“Last semester we talked about salt in my environmental chemistry class,” Isaacson said. “(We studied) the salt/mass balance to find out where all the salt is coming from and how much of it is being retained in the system.”

One surprising variability that Isaacson and his students found when they contacted the Minnesota Department of Transportation was that in some cases, over 10 tons of salt is applied to the road per mile — leaving some lakes in more urban areas of the state just as salty as the ocean.

“Lakes are not functioning like they used to before we showed up, there are lakes that don't turn over because they have so much salt in them,” Isaacson said. “For example, Lake Bemidji stratifies over the course of the year so in the summer, there will be a thermocline. And there are lakes that have had enough salt added to them that the thermocline stays all year round.”

For those less familiar with this process, lakes typically mix or “turn over” twice each year — once in the spring and again in the fall. The mixing brings oxygen to the deepest water and moves nutrients through the water column. Chlorides can cause lakes to stratify and chloride-contaminated water is denser than fresh water so it sinks to the bottom of the lake preventing mixing from occurring as it normally should.

Courtesy / National Geographic Society

The reduction in lakes turning over can result in low oxygen levels in the deepest water, which is also fish habitat. Fish and aquatic organisms cannot survive in water with high chloride content and can also interfere with the growth of aquatic vegetation.

For example, up to 70% of road salt applied on Minneapolis and St. Paul metropolitan area roads end up in groundwater aquifers and nearby lakes, many of which exceed regulatory limits for chloride concentrations. However, researchers at the University of Minnesota speculate that if the state completely stopped using chlorides for deicing, our lakes would eventually flush and return to more normal chloride levels.

Although Isaacson is passionate about protecting freshwater ecosystems from the contamination of road deicing salts, it’s a rather difficult task. Human safety is undoubtedly a huge priority, but balancing ecological impacts and the safety of humans comes at a cost.

“It is critical that policymakers, environmental managers, transportation professionals, scientists and the public recognize that human safety comes at a cost of changing the structure and function of our freshwater ecosystems,” a study on the impacts of road salt salinization in fresh waters reads. “These costs may result in a loss of valuable ecosystem services such as water clarity, drinkable water, recreation venues and fisheries. It is important to find innovative ways of keeping humans safe on the road during the winter months but at the same time protecting freshwater ecosystems from road salt salinization.”

According to MnDOT’s website, snowplow operators attempt to apply only the amount of salt required depending on a slew of variables such as the current temperature, wind conditions and pavement type. Using too much salt is a waste of money and resources, but using too little will cause the roadway to refreeze.

The Minnesota Pollution Control Agency provides ways individuals can take action this winter with these smart salting tips:

• Shovel and scrape. The more snow and ice you remove, the less salt is needed to be effective. The YouTube video "Improved Winter Maintenance: Good Choices for Clean Water" offers tools, techniques, and products that you can use to keep your driveways and sidewalks safe while protecting our waters. 
• 15 degrees and below is too cold for salt. Most salts stop working at around 15 degrees, so instead use sand for traction but remember that sand does not melt ice. 
• Use the right amount. That crunch from sidewalk salt under your feet does not signify safety. People often think more salt equals more snow and ice melt. Around 12 ounces — roughly a coffee mug full — effectively treats a 20-foot driveway or 10 sidewalk squares (about 1,000 square feet). Aim to apply salt consistently (e.g. with a spreader) and use only in critical areas. 
• Sweep up visible salt on dry surfaces. It is no longer doing any work and will be washed away into local waters. You can keep it to use later. 
• Take inventory. If you have common icy spots each winter, keep track of them and fix what you can in the spring to avoid creating icy conditions next winter. 
• Don’t expect perfect conditions. Slow down and drive carefully. Always give plow drivers plenty of space to do their work. Consider purchasing winter tires. 
• Wear proper footwear. Wear shoes or boots with good traction and pay attention to where you are walking, avoid icy spots, if possible. Take it slow and give yourself extra time to get where you’re going. 
• Hire certified Smart Salters. Businesses that need someone to shovel or plow should hire a trained and certified Smart-Salting contractor. Individuals can advocate for reducing salt use in their community, at schools, churches, local businesses and government agencies.

The MPCA offers training for winter maintenance professionals, property managers and others interested in providing safe surfaces in winter and minimizing harmful environmental impacts.
They also offer an online workshop for local leaders to learn how they can help. Check out the MPCA’s Smart Salting training website to learn more, stay current on all things smart salting by subscribing to their newsletter or visit the MPCA website for more snow removal tips and to learn more about the dangers of chloride pollution in Minnesota waters.