On a sunny evening at the Minnesota State Fair, Lauren Schulzetenberg stands next to a stack of 50-pound road-salt bags, a 3-foot-tall water softener, and a sign that reads, "You can save a lot of salt." As fairgoers wander by, Schulzetenberg—an environmental research assistant at Fortin Consulting, a firm focused on Minnesota's water resources—engages them in conversation. First she asks what they already know about salt pollution. Then she launches into her talking points.
Minnesota's lakes and streams are getting saltier, she begins. At elevated levels, salt—specifically the chloride part of salt, or sodium chloride—is toxic to fish and other aquatic life. One teaspoon of salt pollutes five gallons of water, she adds. And while there is no good way to get chloride out of water, there are some simple things people can do to reduce the environmental load, like using less salt on icy sidewalks or changing the settings on their water softeners.
"Our freshwater is one of our greatest resources," Schulzetenberg tells a gray-bearded man from outside of St. Cloud. "Everyone should understand that this is something we should be concerned about."
The fair display is part of an all-out educational blitz by the Minnesota Pollution Control Agency and its partners, including the Department of Natural Resources, to get the word out about salt pollution in Minnesota—an effort that includes winter maintenance workshops, informational websites, and a hefty new document that sums up everything known about chloride pollution in Minnesota. Posted online in June and the first of its kind in the country, the 217-page Draft Statewide Chloride Management Plan is a comprehensive call to action, loaded with alarming numbers: 50 water bodies in Minnesota are now classified as impaired by chloride. Salt has impacted at least 221 river miles, 55 acres of wetlands, and 1,400 acres of lakes.
Statewide, chloride levels have increased in 59 water bodies over the past decade. And the statistics are likely to be far worse than those numbers suggest: So far, data has been collected for only a fraction of Minnesota's rivers, streams, and more than 11,800 lakes.
Chloride is a serious threat to Minnesota's freshwater, says Brooke Asleson, water pollution prevention coordinator at the MPCA. Because it does not break down or settle out of water, she says, the agency wants people to know that prevention is the only solution. "We need to take action quickly to reduce future costs," Asleson says. "Chloride is permanent. You can't get it out."
Chloride occurs naturally in lakes and streams, and many organisms need it to carry out the basic functions of life. But elevated levels can cause cells to lose water and become deprived of nutrients, ultimately killing fish, amphibians, plants, and other aquatic organisms. On land, excessive amounts of chloride can harm pets, soil, cars, bridges, and more.
"It's a mineral and it's natural and we need it," says Tom Burri, a limnologist and water-quality consultant at the Minnesota DNR. "But excessive is bad, and in some instances we're there. We're at that excessive point. And we're disrupting fish and lake systems with this."
Although scientists have known about the potential for chloride to cause problems in the environment since at least the 1960s, Burri says, it wasn't until recently that researchers began to learn the true extent of the problem in Minnesota. In research published in 2008, University of Minnesota environmental engineer Heinz Stefan and colleagues reported that chloride levels were increasing in lakes around Minneapolis and St. Paul. Levels had grown high enough in some places that saltwater, which is heavier than freshwater, was sinking to the bottoms of lakes, which prevented those lakes from mixing seasonally and kept oxygen from getting to bottom-dwelling organisms. And chloride levels peaked in water bodies in winter and spring.
What You Can Do to Fight Chloride Pollution
When clearing winter walks
* Shovel early and often. The more snow and ice you remove, the less salt you’ll need.
* Sprinkle sparsely. Leave 3 inches between salt grains.
* Go lean. A coffee mug is adequate for a 20-foot driveway or 10 sidewalk squares.
* Use a tool. A handheld spreader can apply salt consistently.
* Wait for warmer weather. When ground temperatures are below 15 degrees, it’s too cold for ordinary sodium chloride to work.
* Use the right de-icer. Calcium chloride works at much lower temperatures than sodium chloride.
* Sweep up extra salt. If it is visible on dry pavement, it is not doing anything and will be washed into water bodies.
When considering, choosing, or using a water softener
* You might not need one. Find out the hardness of your water by calling the city, consulting a professional, or using a hardness testing kit. If water is at an acceptable level, think twice about softening. The chloride standard for drinking water is 250 mg/l.
* Don’t over-soften. Check your unit’s settings. It may have been set at an unnecessarily high level at the factory.
* Soften only the water that needs it. Not to outside spigots or cold drinking water taps.
* Monitor your softener. If it uses more than one bag of salt per month, work with a water quality professional to optimize efficiency.
* Look into lower-salt methods. Pre-filters can be used to remove iron, manganese, and hydrogen sulfide without help from water softeners.
* Upgrade your softener. Look for demand-initiated versions that are more salt efficient, operate based on how much water you use, and can reduce salt use by up to 60 percent.
* Lengthen the cycle. If you have a timer-based system, see if you can extend the time between cycles.
Those findings suggested that monitoring programs had been missing salt by collecting samples from surface waters in warm months. "We were really underestimating how much chloride we had," Asleson says. And the problem was not temporary. Up to 78 percent of the chloride that entered the Twin Cities watershed was staying there, the researchers found. The only known way to get chloride out of water is with a process called reverse osmosis. But reverse osmosis is prohibitively expensive for most municipalities. And it creates another problem: salty brine waste that still needs to be thrown away somewhere.
In 2009, the MPCA began to compile information as part of a partnership studying chloride pollution in Minneapolis and St. Paul. Its findings, published in 2016 as the Twin Cities Metropolitan Area Chloride Management Plan, made a clear case that chloride was a significant problem. At the time, data was available on 340 of the metro's 1,000-plus lakes, wetlands, and streams. Of those, levels of chloride exceeded acceptable limits set by the U.S. Environmental Protection Agency in approximately 11 percent, or 39 water bodies. Another 11 percent were considered high-risk. Many contaminated water bodies were in the heart of the Twin Cities and included particularly scenic and popular lakes on city parkland, such as Brownie Lake in Minneapolis and Como Lake in St. Paul. As an "invisible pollutant," Asleson says, chloride hasn't yet made a noticeable difference in how these lakes look to the general public.
As soon as it had finished assessing the state's urban core, Asleson says, the MPCA started looking outstate, where it found that the trouble did not end. Statewide, according to the new report, 50 water bodies have been identified as impaired with chloride. Another 120 are considered to be dangerously close to the limits. And the sources of chloride varied as researchers began to look around.
They found that road salt was the largest chloride source statewide and that water softeners accounted for the majority of chloride coming out of wastewater treatment plants. Overall, road salt is responsible for 42 percent of chloride that enters the environment and gets into groundwater and surface waters in Minnesota, while agricultural fertilizers contribute 23 percent, according to a 2019 study by researchers at the University of Minnesota.
In areas where water is notoriously "hard," or rich with minerals that can leave residue on dishes and pipes and damage plumbing fixtures, water softeners are a major issue. According to the new study, wastewater treatment plants account for 22 percent of the chloride in Minnesota's freshwater, with more than half of that coming from water softeners. In Morris, which has hard water, approximately 90 percent of households have softeners. Although the use of water softeners varies widely, the average household in the state that softens water uses an estimated 25 pounds of salt each month.
Salt is necessary for water softeners, which work by sending water through a sand- or bead-like resin, where hard minerals like magnesium and calcium get traded for sodium. When the resin is used up, it needs to be washed in a salty solution that leaves behind a brine waste. That salty brine ends up in wastewater.
About 100 communities in Minnesota have wastewater treatment plants that are struggling to meet their chloride discharge limits, says Alycia Overbo, a graduate student in the University of Minnesota's Water Resources Science program and author of the chloride-accounting study. And those communities tend to lack the money to invest in centralized water softeners, reverse-osmosis systems, or other salt-reducing strategies. Complexities like those suggest that attacking the chloride problem requires a nuanced strategy. There is no "silver bullet" approach to chloride, Overbo says.
Beyond the main sources, Overbo's study also found that chloride gets into the environment through fertilizer use, livestock waste, dust suppressants, industries, and other inputs. Given its ubiquity, Burri agrees that fixing the salt problem is going to take creative thinking that involves all sorts of audiences.
"It's a big problem [that has] multiple sources," he says. "So it's going to take big solutions from multiple sources."
Several times a week, Connie Fortin, president of Fortin Consulting, stands in front of a classroom full of snowplow drivers, property managers, private contractors, and others who, as part of their jobs, make decisions about how much salt to put on icy roads, parking lots, and sidewalks. When these Smart Salting workshops begin, participants tend to sit back in their chairs, arms crossed, says the MPCA's Asleson, who sometimes helps teach the courses. They may have decades of experience de-icing paved surfaces with loads of salt, she says, and they sometimes resist being told to change what they already know how to do.
Attendees tend to worry about safety, says Fortin, whose firm helped research and write the statewide management plan. If pedestrians and drivers can't see granules of salt on the pavement, they may think surfaces are dangerous.
"Their customers want to hear the crunch of salt in their buildings," she says of attendees. "They associate it with safety."
But visible chunks of salt indicate an oversalted surface, participants learn in the workshops, which offer a variety of recommendations for how to use less salt: calibrating equipment, monitoring pavement temperatures, using liquid alternatives that can be applied in smaller amounts under certain conditions. At lunchtime, attendees often start talking about ideas they might be able to implement.
"By the end of class," Asleson says, "the majority are inspired to go make changes."
Results of the training sessions can be dramatic. After a workshop at the Mayo Clinic in the fall of 2018, the Rochester hospital reduced its winter salt use by 60 percent without any increase in slips and falls. The city of Minnetonka managed to reduce its salt use by more than 50 percent.
"I get a lot of pushback, like, 'We've got to put more salt in the handicap spots, more salt at the medical clinic, more salt at the senior center,'" Fortin says. "But you don't. You just need to do the right amount and understand how to do it. It's not an exact science, but we can get way better."
As educational efforts continue in settings as disparate as conference rooms and State Fair buildings, scientists are looking to new technologies to reduce salt use. At the University of Minnesota in Minneapolis, environmental engineer John Gulliver is studying permeable pavements that allow water to flow through air pockets under the surface. Their original purpose is to reduce flooding and runoff, but an added benefit may be ice deterrence. In field tests, Gulliver has found that permeable pavements prevent water from pooling on the pavement's surface. If that translates to less ice buildup, it could also mean less salt would be needed for de-icing. Permeable pavements aren't practical for high-volume roads, Gulliver says. But they are already being used in some alleys, side streets, and parking lots, where road-salt savings could be substantial.
Other lines of research include salt-free water softeners, chemical alternatives to road salt, and even warm sand.
"We're investigating all kinds of alternatives, and we're looking at the ones that seem to have the most potential," Gulliver says. Still unknown, experts say, is what impact those alternatives might have on the environment. And because many new technologies are still works in progress, the best strategy for now is to use less.
"The most immediate solution that we can undertake is source reduction," Gulliver says. "That means we put less salt down."
Minnesota is not the only state with a chloride problem, but it is the first state to have a management plan. It was also the first state to offer an annual road-salt symposium, which Fortin began organizing 19 years ago with the Freshwater Society. The conference attracts environmental scientists, transportation and maintenance crews, and other attendees from around the state to learn about the latest developments in salt reduction.
"Every other state is watching us, for sure," says Fortin, who looks for ways to keep salt out of the environment in any way possible. "Whether it's in your water softener, whether it's on your driveway, or whether it's on your French fries, use less."
Talking about salt pollution at the State Fair appears to be unique, too, making Minnesota the first to consider conversations about chloride pollution as commonplace as fried foods and merry-go-rounds. But Schulzetenberg's interactions with fairgoers show there's still work to be done before chloride becomes a household word.
One woman is surprised to learn that the water softener in her Brooklyn Park home releases salt into her wastewater, and she admits that she still isn't sure how all the settings on the contraption work. Even passers-by who are savvy about science find they have more to learn. Another woman, a researcher who studies sustainable plastics at the University of Minnesota, comes by the booth looking for stamps to fill a bingo-style activity card, then stays to read the signs and ask questions. "I didn't know salt was making a big problem for the environment," she says. "I think it's quite striking. I never thought about this."