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Does salt help on roads? Only so much

By Mike Genet mike.genet@examiner.net

Tuesday proved a bit “warmer” for area road crews as they continue to tackle an unusually cold stretch of winter. But the frigid temperatures – which are forecast to be worse in the coming days – have hampered their normal plan of attack to clean up the roads.

In general, the salt spread out behind a plow, or perhaps sprinkled before a storm, doesn’t work nearly as well, if at all, when temperatures barely reach double digits and the sun is more a rumor than reality. And what does start to melt or is left behind by the plow quickly refreezes.

Road crews, such as this one in Blue Springs, have been busy for days, and the cold and falling snow are expected to linger.

“It makes it a little more challenging,” Blue Springs Public Works Director Chris Sandie said Tuesday of the extra-chilly temperatures accompanying light snowfalls. “It’s amazing how much difference even five degrees will make. We’re seeing a lot more clear streets today.” 

Sandy and Zan McKinney, superintendent of streets in ndependence, explain that when temperatures dip to about 19 or 20 degrees, regular road salt (sodium chloride) melts snow much more slowly. An additive such as calcium chloride or potassium chloride can help lower the effective temperature, but it’s more expensive and requires more volume the colder it gets to work just as well.

At 30 degrees, one pound of salt can melt 50 pounds of snow in an hour, McKinney said. At 20 degrees, that pound of salt can do 10 pounds of snow, and at 15 degrees or lower it’s down to four or five pounds of snow, and it takes several hours instead of an hour.

“Completely ineffective, to be honest,” he said of regular salt in these temperatures. “It takes so long for snow to start melting, most of it will get driven off the roads.”

Additives will jumpstart the melting process, McKinney said, and a beet juice or similar brine used before a snowstorm helps treatments stick to the pavement longer, but right now it’s “nearly impossible to have bare pavement.”

“During the day, even when temperatures are low, radiation from the sun helps,” he said. “We have crews out (Tuesday), getting to streets that are harder to get to.”

Sandie said Tuesday his Blue Springs crews hadn’t reached residential streets yet because their road program doesn’t call for plows there until snow reaches 2 inches or more. Also, temperatures this cold can take the moisture left after a plow or from continued traffic and quickly slicken roads – almost like a Zamboni that treated an ice rink.  

“We can keep throwing salt at it, and that’s able to melt it for a little bit, but then it’s frozen again and becomes icy,” Sandie said. “It’s a fine line you have to walk.

“It’s been quite a while since we had a cold spell like this, into next week.”

Both men said their city’s salt supplies are in good shape, but that doesn’t mean they’ll simply use it continuously. McKinney said one has to keep in mind the environmental impact. 

“In the end, all this stuff goes into the storm drains and then into our rivers and streams,” he said.

The Missouri Department of Transportation said its crews have been working in alternating shifts around the clock this week, using everything in the “toolbox” to clean up highways.

“They’re using salt, sand, calcium chloride and beet juice to treat some of their routes,” a social media post read.

In all cases, public works departments urge drivers to have patience and give their road crews room to work.

“We’ll have crews out every day this week, through the day, to push this stuff off the roads,” McKinney said.