Fifty Minnesota lakes and streams are on the state's impaired waters list because of too much chloride.
The chloride is mainly from road salt, Minnesota Public Radio reported. Excess chloride can damage aquatic life reproduction, corrode infrastructure and cause humans health problems.
"We've kind of brought this on ourselves a little bit because we have the capability to have very drivable roads in winter," said Ed Matthiesen, an engineer for the Shingle Creek watershed. "The downside is because we can get salt very cheaply and it's one of the things that keeps the roads clear, we tend to apply a lot of it."
Shingle Creek was the first body of water added to the list about 20 years ago and caused the state to require a 70 percent reduction in chloride.
"It's going to take a long time before we're actually going to start to see the level of chloride come down in our water bodies," said Brooke Asleson with the Minnesota Pollution Control Agency.
Chloride seeps into the ground and gets into shallow groundwater, she said. The salt can be retained there for a long time, depending on the soil.
"So there could be chloride from five years ago, 10 years ago that's we're still seeing kind of making its way to our water bodies through kind of subsurface flow," Asleson said.
Snowplow driver Steve Forness said there's been increased training to make snowplow operators aware of the harmful environmental effects salt can have.
He said screens in his vehicle provide detailed information about the roads conditions and what should be used to make then safer — such as salt brine or a magnesium chloride solution.
"There are times you have to cheat a little bit just because of the conditions and the weather," he said. "But for the most part it's reduced it and everybody's aware of what they're doing more so than before."