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During heavy snows, airport crews might repeat treatments of potassium acetate every 15 minutes. Rock salt treatment on Minneapolis streets costs about 3 percent of what an equivalent treatment with potassium acetate would cost.
At the same time, the designated routine after a heavy snow in Minneapolis and St. Paul means that side streets don’t get plowed until the day after the snow stops — by which time traffic has also created icy ruts that might resist melting and plowing.
In Wisconsin’s Polk County, the highway department has been treating its roads partly with cheese brine — a salt solution used in making provolone and mozzarellae. Highways chief Steve Warndahl said it hasn’t been tested in a lab, but based on tests in a jar outside his office it didn’t freeze until the temperature reached 21 below, as opposed to 6 below for rock salt solution.
“All I know is we put it in a bottle and it didn’t freeze, so we use a bunch of it,” he said, adding that it doesn’t smell and doesn’t get slimy, as magnesium chloride sometimes does. The county buys it from a local dairy for about 8 cents per gallon, compared with about $1.50 per gallon for magnesium chloride.
The supply from the local dairy has not been entirely consistent, though. MnDOT spokeswoman Christine Krueger said that’s one reason MnDOT does not use it.
“We don’t have a lot of cheese production, like Wisconsin does,” she said.
MnDOT has used soybean oil and corn-based substances for winter road treatment, and numerous agencies use beet juice and other vegetable products, but more for adhesion than de-icing. St. Croix County, Wis., is using beet juice on its roads, and a popular anecdote this winter is that roads there, including I-94 east of Hudson, have been in better driving condition than those in Minnesota.
Chris Ouellette, the Wisconsin Transportation Department’s northwest region spokeswoman, said that I-94 in Wisconsin gets far less traffic than metro roads and is the only four-lane highway St. Croix County has to manage.
At MSP, 58.4 inches of snow has fallen this season, 25 percent more than normal to date.
“Most of the snow that fell in December is still here,” Kennedy said. “It hasn’t left us with a lot of options.”
But there’s some good/bad news, due to slowly rising temperatures.
“We now see some of the washboarded ice starting to break on us” on some streets, Kennedy said. “On residential streets, that 6-inch hardpack is going to fluff up on us. It might start to look like we haven’t even been there.”
Bill McAuliffe • 612-673-7646