After two mild winters, drivers are being reminded ice and snow can make for some messy roads.
Salt and brine have shown to be effective tools to help keep roads clear and safer to drive in the winter, but it comes with a cost.
One study out of Minnesota found that salt damage to infrastructure, cars, and the environment ranged from $803 to $3,341 per ton of road salt used.
It’s also costing the Northwoods its water quality.
Rising chloride levels
The UW Trout Lake station has been collecting data from seven lakes in the Boulder Junction area for 45 years as part of the Long-Term Ecological Research Program. One part of that research has been looking at the chloride levels in lakes.
Limnologist Carol Warden and other researchers have found that lakes, especially those along highways, are seeing increasing levels of chloride.
“We saw with Sparkling Lake in particular, right along Highway 51, that its chloride levels are rising. That trajectory is only going in one direction, and it's on the rise,” said Warden. “That was sort of the catalyst for doing a larger look at lakes around our area, especially lakes that are along major highways, to see if road salt is having an impact on our water chemistry and water quality. And we see that it is.”
The EPA chloride threshold is 230 mg/l. That is the equivalent of a teaspoon of salt in a five-gallon bucket of water.
In lakes that have been tested in Vilas County, researchers are finding up to around 33 mg/l of chloride. Even though that’s far from the EPA threshold, Warden says that the lakes tiniest creatures like zooplankton and other macro invertebrates can be affected by levels as low as 10 mg/l.
For the lakes they have data on, Warden says Sparkling, Midge, Safford, and Little Muskie have the more concerning levels.
“We're seeing those levels that would be concerning to an ecologist. Not quite the levels that are chronic issue according to the EPA, but we do see those sometimes in the Madison lakes,” said Warden. “Obviously that's not right here in our neck of the woods, but it is a picture of what is possible if we keep adding salt to our environment.”
A 2016 study by Hilary Dugan, another UW researcher, predicts many lakes in North America will exceed the 230 mg/l threshold over the next several decades if current trends continue.
The big issue with salt is it just keeps accumulating over time.
Rivers will push it down stream, but it will keep building in seepage lakes—which are common in the Northwoods.
Road salt appears to be the biggest source of chloride in lakes in the Northwoods. Chloride in agricultural settings and, to a lesser extent, water softeners can also add to the problem.
“It's pretty clear that the salting of the roads and of our sidewalks and things like that are the main player,” said Warden.
Reducing salt use
Warden says there are still a lot of questions about finding that balance between safety and protecting the environment.
She pointed to questions like how efficient is the current salt use, those times when road crews pre-treat roads ahead of forecasted snowfall that doesn’t pan out, and is it worth waiting until it actually starts snowing.
“I don't know the answer there. These are questions that we have to find the answers for and work with professionals in that field to know what the best solution is,” said Warden.
Warden does hope people will consider what it means to live in the Northwoods in the winter, that it may be that people need to leave more time to get to their destination because the roads aren’t perfect.
“I would encourage people to take count of their conveniences and see if the value of convenience is larger than the value of the place that you live in, the health of that place,” said Warden.
There’s already some things towns do, like using sand to create traction, that helps reduce salt use. While researchers and counties have conversations about reducing salt use, there’s steps people can take as well.
“Every time you walk out of a commercial store around here, you're basically walking on white covered concrete because there is a layer of salt there already, and then on top of that, you still have the rock salt sitting,” said Warden.
Best practices for clearing snow include removing as much of it manually as possible. If you do use salt, scatter it so there is space between granules. A coffee mug of salt is enough to treat an entire 20-foot driveway or 10 sidewalk squares, according to Wisconsin Salt Wise.
Salt generally stops working around 15 degrees.
Warden expects conversations around salt use and its impact will continue in the years to come.
“Salt can be a real problem,” said Warden. “Get an awareness, see what that's all about, what chloride does to freshwater systems. Then let's work together on seeing how we can reduce the use.”
