High road salt use causing Wisconsin lakes to suffer
It comes as no surprise that road salt is bad for your car and your clothes, but all of that salt is also having an impact on lakes in southeast Wisconsin. Chloride is a main component of rock salt used on the roads and for the past few decades researches have been watching chloride levels go up in Wisconsin lakes.
In any given storm, highway departments use anywhere from ten to 20 tons of salt according to Bill Kern of the Jefferson County Highway Department.
"Some of that [salt] will get washed into streams or into storm sewers," said UW-Madison Professor of Limnology Hilary Dugan.
That washed off salt goes straight into our lakes. Professor Dugan is part of a worldwide study looking at the concentrations of chloride in freshwater lakes.
Dugan says that Chloride concentrations have been climbing since the 1940s when road salt was first used and that use has grown exponentially over the past few decades.
"We saw high chloride concentrations in all lakes that were near roads," said Dugan.
Today, both Madison's Lake Mendota and Walworth County's Geneva Lake have chloride levels near 100 milligrams getting closer to the EPA critical threshold of 250 milligrams when you start to see effects on aquatic ecosystems.
“We know from lab experiments that a lot of animals don’t survive well in these higher chloride concentrations," said Dugan.
Rivers and streams across Wisconsin are in even worse shape. The Kinnickinnic River flowing through Milwaukee has chloride levels nearing 5,000 milligrams.
This problem isn't falling on deaf ears. The Wisconsin DOT has started a pilot program to use only liquid on certain stretches of road.
“We’re at the phase where we’re trying to get more liquids on our trucks and are starting a pilot to do a liquid only route," said Highway Commissioner Bill Kern.
The liquid only routes use a brine solution, which still contains melted salt, but no rock salt.
According to Kern, they've used about 50 percent less rock salt in that section. The decrease in salt saves money and the results of the brine have been positive, "The reaction is quicker and we’re able to clear the roads quicker."
Professor Dugan says it's a possibility that southeast Wisconsin lakes could get to a point where the chloride level is so high that there wouldn't be any fish. She added that it's more likely there would be fish just not the one's we are used to. Invasive species like Zebra mussels and Asian carp can adapt quickly, but native walleye may go somewhere fresher.
If major changes aren't made Wisconsin lakes could hit worrisome chloride levels soon, "In a few decades we’ll start hitting some of these concentrations that people consider chronic and acute levels," said Dugan.
Experts say it's not just salt trucks that have an impact. Some of the highest salt usage comes from private plow companies who use a lot of salt to clear large parking lots. Private citizens have a role too. Officials recommend you only use a cup of salt to clear a full standard driveway and that most of us use way too much only contributing to the high chloride problem.