Many Wisconsin residents use salt to prevent icy sidewalks and roads during the winter. But while salt helps prevent slips and falls, research shows salt persists in bodies of freshwater, leading to detrimental environmental consequences.
While some schools in the University of Wisconsin System have taken steps to reduce their road salt use, UW-Madison doesn’t always take an environmentally responsible approach to salt use, Wisconsin Salt Wise program manager Allison Madison said.
Today, using salt to help eliminate ice on roads and sidewalks is a common occurrence, but the practice started in the city of Madison in the 1960s, Madison said. After approximately 70 years of using road salt, scientists are currently witnessing the consequences of salt pollution in the Yahara watershed, which includes Madison-area lakes and across the state.
“The chloride concentration is going up and up and up in all the Yahara lakes, especially Lake Wingra, because it’s the smallest [and] doesn’t have much ability to dilute the salt that’s coming in,” Madison said.
In Dane County, some water bodies have been deemed impaired under the Clean Water Act, Department of Natural Resources Storm Water Runoff section manager Shannon Haydin said. Scientists place a body of water on a 303(d) impaired list after it reaches a certain pollutant threshold. In Wisconsin, there are 50 rivers and one lake which exceed the chloride threshold for chronic toxicity.
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Often people spread salt on the ground after it snows and then forget about it, Madison said. But salt, which breaks into sodium and chloride ions when dissolved, washes through storm drains into the freshwater rivers and lakes. Once chloride enters a water system, there is no way to remove it.
“It doesn’t ever go away,” Haydin said. “There’s nothing that breaks chloride down, and there are currently no best management practices that will mitigate chloride.”
These increased salt concentrations harm the health of organisms that live in the bodies of freshwater that aren’t adapted to saltier environments. The many species of zooplankton — which play a critical role in freshwater ecosystems — that live in lakes can’t cope with high salt concentrations, Madison said.
Zooplankton bridge an important gap at the bottom of the food chain. They eat the algae and, in turn, the fish eat them. A higher concentration of salt means less zooplankton and less fish food, Madison said.
Higher salt concentrations also limit the amount of zooplankton that eat blue-green algae, Madison said. While phosphorus runoff from fertilizer creates toxic blue-green algae blooms, salt pollution also contributes to this problem by killing the zooplankton which eat that algae.
“The idea there is that salt is a preservative, meaning it prevents the growth of bacteria, right?” Madison said. “Tiny little organisms are killed by a lot of salt because their bodies pretty much turn into pickles. They can’t handle it.”
Despite the environmental risks, road salt is often helpful for preventing icy roads. But it is not always required, and people can reduce the amount of salt they use. Madison said focusing on mechanical removal of snow is a good place to start. If necessary, people should use salt to focus on breaking the bond between snow and the pavement, so it’s easier to move snow.
If a situation necessitates road salt, one coffee cup full of salt is enough for a 20 foot driveway or 10 sidewalk squares, according to the Wisconsin Salt Wise website. Madison said salt works slower at lower temperatures, so when it’s under 15-20 degrees Fahrenheit, it’s largely ineffective. Instead, people should spread sand to create some traction.
Following the snowfall in recent weeks, UW-Madison limnology professor Hilary Dugan took to Twitter to highlight UW-Madison’s excess salt use. According to Dugan, UW-Madison roads and sidewalks had piles of salt, whereas the city of Madison took a more responsible approach.
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Other schools in the UW System have taken steps to reduce their salt use, Madison said. UW-Green Bay now has better methods of mechanical snow and ice removal. UW-Eau Claire and UW-Whitewater both make their own brine, a mixture of salt and water, on campus to reduce their salt use.
“I think UW-Madison needs to follow suit,” Madison said. “It’s a bigger campus, so it’s more complicated. But they also really claimed sustainability as a value, so they need to step up in this regard.”
UW-Madison Division of Facilities Planning & Management marketing and communications director Lori Wilson said that UW-Madison is dedicated to minimizing salt use.
According to Wilson, university staff are trained in using the least amount of salt necessary for it to work effectively, though sometimes the machines used to spread salt unintentionally drop more than necessary.
UW-Madison is currently working with the Office of Sustainability on a program called “Salt Wise at UW–Madison” which aims to work with campus departments and increase transparency on salt use, Wilson said.
Madison said in addition to the lack of knowledge surrounding salt pollution, many property managers choose to use excess amounts of road salt to avoid liability if someone slips and falls on their property.
To address liability concerns, Sen. Andre Jacque and Rep. Elijah Behnke co-sponsored a bill which would protect Wisconsin contractors from liability for ice-related falls. If contractors become certified in best practices and document their salt use at each given site, Madison said the bill would protect them from liability related to snow and ice damages.
The Wisconsin DNR completed a report in December 2022 that outlines 16 recommendations to curb chloride pollution. Haydin said the DNR works mostly with regulations, so one option is to enforce limits on the amount chloride people and organizations can release into the environment. While this rule isn’t currently in place for chloride, these types of policies have been successful in the past.
It takes very little effort for people to reduce their own salt use, Haydin said, and many people just don’t know the environmental effects of salt pollution.
“It’s been really interesting in the last couple of weeks the momentum this topic has gotten,” Haydin said. “It makes me really happy that people are paying attention.”
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