The United States dumps about 21 million metric tons of salt on the roads every year.
Road salt can reduce car accidents on icy winter days. But it often doesn’t stay on the road — and that runoff can harm aquatic life in rivers and lakes as well as damage plants and soil.
Indiana Public Broadcasting talked with experts about ways cities, highway departments and residents can use salt more efficiently.
How does excess salt harm the environment?
University of Vermont extension associate professor Kris Stepenuck educates people on how to reduce road salt through the Lake Champlain Sea Grant program.
She said when salt gets into a lake, it can prevent it from “turning over.” That’s where the layers of water mix, bringing fresh oxygen and nutrients to the bottom.
“So the fish have to stay out of that zone and up above that part of the lake," Stepenuck said.
She said excess salt can also affect the soil and kill plants.
"It can kill soil microbes. It makes soil more compact so that it can't accept water into it, causing more runoff to water bodies at kind of a higher rate," Stepenuck said.
Ways Indiana residents can get smart about salt
Stepenuck said, first, you want to get as much snow off the pavement as possible before salting.
Then, figure out if the road is the right temperature. Salt won’t work below 15 degrees Fahrenheit and may not be necessary above 30 degrees.
Spread the salt grains about three inches apart, using a spreader can help.
Stepenuck said you can also reuse salt you see on the ground once the storm has passed.
“You can sweep it up and you can use it again later. You can save yourself money and that salt will still be just as good in the next round," she said.
If you can plan several hours ahead, you can also pre-treat the pavement with salt brine.
"That works kind of like an egg with some oil in the pan. Before you cook the egg, you put the oil in the pan and it prevents the egg from sticking to the pan. Same thing is true if you have a brine on a pavement ahead of a storm," Stepenuck said.
She said salt brine makes it easier to shovel snow and ice off your driveway.
Though Stepenuck warns, if you get the proportions wrong, it could make the surface more slippery. The brine needs to be 23.3 percent salt. University of Vermont suggests putting 13 pounds of salt in 5 gallons of water to get the right solution.
Stepenuck said salt generally won't work on gravel driveways, instead traction is the goal. Use sand or kitty litter.
How cities, highway departments can use salt more efficiently
A lot of the advice for residents works for local and state governments too.
Natalie Garrett is the strategic communications director for the Indiana Department of Transportation. She said the state tracks how much salt it has in storage and pre-treats the roads with salt brine so the salt stays on the pavement.
Garrett said INDOT also works with a company to help forecast winter conditions on certain routes.
“Can help us identify when we may need to deploy crews, when we may need to start using specific materials, start spreading salt or stop spreading salt," she said.
Stepenuck said cities and highway departments can also look into segmented plows that work better on uneven roads.
What about other methods like ash, sand and beet juice?
Stepenuck said coal ash and sand are good ways to get traction, but those can also pollute local waterways.
"They can fill in fish spawning beds, for instance. And they can affect site feeders, who maybe if the water is cloudy or they can't see — like a fish can't see its prey. And it can also affect fish gills and kind of irritate their gills if it gets into the river," she said.
Things like molasses, cheese waste and beet juice have also been used in the past to get rid of the ice. Stepenuck said the sugars in those products can cause what's called biochemical oxygen demand in a stream.
"There's all these little microbes who are super excited that the sugars are there and they grow and expand and multiply and eat up those sugars. But then they all die. And then when they die, they decompose and there's oxygen use when they're decomposing. And so it causes this crash in oxygen levels in the stream or the river, and then that can kill aquatic life," she said.
Stepenuck said using salt more efficiently is likely the best option right now.
Rebecca is our energy and environment reporter. Contact her at rthiele@iu.edu or on Signal at IPBenvironment.01. Follow her on Twitter at @beckythiele.