A rash of traffic accidents in Grand Forks this week raised questions about whether all that brine city street crews were spraying on the roads to deter ice was working.
Streets Superintendent Mark Aubol said, actually, his crews have stopped spraying because even brine will freeze at some point, and he didn't want to inadvertently create an ice rink.
The weather's been pretty chilly, with daytime highs hovering around zero degrees, according to the National Weather Service, and it looks like it'll get even chillier this weekend, with nighttime lows reaching 20 below zero or so.
Brine is a salty solution, and it's the salt that brings down the freezing point of water. So, even when it's 10 degrees and snow should just stick to the street and build up into a layer of ice, the brine causes it to melt.
The key is pavement temperature, which can be different than air temperature. Lots of sun, for instance, will increase pavement temperatures because the darkness of the pavement absorbs heat better. Lots of traffic also will increase temperatures because of the friction of car tires.
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Brine with regular, old sodium chloride, or table salt, works well if the temperature of the pavement is 5 degrees or higher, Aubol said. A solution of calcium chloride, a different kind of salt, can work at temperatures as low as 10-below, he said, but he's reluctant to push it because it could turn colder than that.
Adding to the problem this winter is the wetter than usual snow, he said. It's just getting packed down into ice and becoming very slick, he said.
So, for now, the best thing street crews can do is add a little more salt to the sand that they're spreading on the ice, he said, but the effect doesn't last, as car tires kick the sand to the side of the road.
Reach Tran at (701) 780-1248; (800) 477-6572, ext. 248; or send e-mail to ttran@gfherald.com .
