[UPDATED 12/20/22] – With folks in the Midwest staring down a long span of below frigid weather (and a blizzard warning!), icy and snow-covered surfaces are becoming the norm. While we totally understand the desire to reach for a big bag of rock salt, we are also concerned about the troubling trend of our lakes getting saltier.
Readers of this blog are probably tired of hearing the following phrase, but what we do on land ends up in our water.
That means that all of those salt crystals piled up on our sidewalks or carpeting our parking lots don’t just stay there. They mix into the snowmelt, raise its freezing temperature and then wash away into our freshwater ecosystems. And it’s probably not surprising to hear that the things that live in those freshwater ecosystems don’t do so great on a high salt diet.
We know that sometimes salt may be the answer to a dangerously slippery surface. But, if you’re going to use it, here are three things to know:
1. Less is more. We are WAY over-salting our surfaces.
If you are looking at a surface with piles of rock salt clumped together or a uniform carpet of crystals, then you’re looking at a prime example of how NOT to salt. (You’re also looking at a minefield for doggy paws). You may find this hard to believe, but it only takes about one cup of rock salt to successfully treat a 20-foot driveway or 10 or so sidewalk squares.
To the left is a handy visual for what that looks like from our friends at Wisconsin Salt Wise.
You see, the point of those salt crystals on the surface is for them to disappear or, well, dissolve into snowmelt and create a saltier mixture called “brine” that has a lower freezing point than regular water. All of those piles of salt left over after a surface has been cleared are just piles of salt that failed to do its job. And, considering it only takes a teaspoon of rock salt to pollute 5-gallons of freshwater, that adds up to a big problem.
In fact, lakes across North America are getting steadily saltier, thanks in large part to all the road salt we put down in winter. This is true even for the Great Lakes, which are 7 to 8 times saltier now than they were in the 1800’s. The things that live in our lakes evolved to thrive in freshwater systems – anything we can do to keep that water fresh can go a long way toward protecting our waters for future generations.
2. If it’s below 15 degrees (F), it’s probably too cold for salt to work.
This is not to say that salt absolutely won’t work below 15 Fahrenheit. Factors like the sun warming a road surface or even friction from a steady stream of traffic can keep surface temps well above the air temperature. BUT, when you’re looking at super cold conditions – like the weather on tap this Christmas – pouring a bag of salt on your sidewalk isn’t going to do much to improve conditions.
Sure, those salt crystals might embed themselves in the ice surface and provide a little bit of traction but, even if they are able to melt into a mixture with thawing snow and ice, they’ll only lower the freezing point of the solution from the usual 32 degrees F to, you guessed it, right around 15 degrees.
If you’re dealing with truly polar conditions, hold the (rock) salt. (Also, if you’re putting salt down on TOP of existing snow and ice, you’re going to be disappointed with the result – salt works best to prevent snow and ice buildup, not melt away the glacier that’s already formed!
Always shovel first and salt second.
3. Hold the salt and use sand when possible.
Not only does sand work well on slippery surfaces, it also is far less dangerous for our water AND, what’s more, in many municipalities it’s free! Here in Madison, for example, there are more than a dozen locations where residents can find free piles of sand. Just bring a pail and a shovel and take home an environmentally friendly and salt-free alternative for improving winter walking and driving conditions!
Happy Holidays and stay warm!