Spray before snow cuts use of salt on roads in St. Louis County
Hours before the next big winter snow hits, state highway crews will be out in force, spraying a brine of salt and water onto roadways.
The mixture, which melts snow as it lands on the roads, has been used by the Minnesota Department of Transportation and University of Minnesota for several years. This winter, St. Louis County is similarly investing in new technology to cut salt use, and the city of Duluth likewise is conducting experiments, using salt brine mixed with beet juice.
The point, on the freeway or the sidewalk in front of your house, is to keep snow and ice from ever freezing to the pavement.
"We can go out hours before the storm and pre-treat and keep the snow from sticking in the first place," said Bob Wryk, regional supervisor for the Minnesota Department of Transportation. "We know it works to reduce crashes and we think it's going to cut the amount of chemical out there."
The benefits are safer roads, a major savings on salt use and less salt running off into the environment. The U of M's Minneapolis campus has cut salt use by 41 percent since 2006 and sand by 99 percent. Accidents and injuries went down, and experts say brining works on sidewalks and parking lots, making it easier to shovel or snow-blow when the storm is over.
That makes it an option for homeowners dealing with snow that gets trampled into an encrusted mess. A mixture of half salt and half water can be sprayed sparingly on sidewalks or driveways before a storm begins, or formulated consumer brands can be used, sold under names like Icenator and Bare Ground Liquid Ice Melt.
"I'm actually trying it out myself," said Gary Amdahl, the manager at Duluth's Northern Tool and Equipment, adding he hasn't had much call for it yet.
Price may be one reason. The consumer brands aren't cheap -- averaging about $25 per gallon. Buyers will have to weigh the price against the work saved.
For highway crews who use less expensive salt brines or wetted salt, the effort more than pays for itself.
With traditional salting efforts, each time the 94 regional MnDOT plow trucks leave their garages, they're deployed with nearly $100,000 of salt and magnesium chloride combined, usually taking several loads each storm to cover about 1,600 miles of highway across Northeastern Minnesota. That totals about $5 million annually just for one region of the state.
St. Louis County spends more than $1.4 million each year on nearly 20,000 tons of salt and 67,000 cubic yards of sand. Officials hope to cut salt and sand use 45 percent -- enough to save taxpayers about $634,000 - with new trucks, spreaders and other technology.
If it's too rainy to use liquids, crews can drop pre-wetted salt ahead of a storm to kick-start the melting effort. Magnesium chloride, while more expensive than salt, will keep working even below zero.
St. Louis County commissioners in September approved $535,000 for four new trucks and 40 pre-wetting machines to add to the county's snow removing fleet. The pre-wetting keeps the otherwise rock hard and dry salt mixture in place and on the highway driving lanes, not pushed off into the ditch.
The county also invested in outfitting 46 of its 151 plow trucks with computerized calibration technology that adjusts salt and sand spreading with truck speed and road temperatures. GPS allows crews to check how much salt and sand is being used on each mile of roadway, and remote sensors can tell drivers how cold the pavement is.
"With everything we are doing now, we hope to see a 45 percent savings in salt and sand," Martimo said.
While the city of Duluth doesn't have the budget to upgrade plow trucks and technology this year, Kelly Fleissner, the city's public works supervisor, said a mechanic last week retrofitted an old truck with a home-made part so that some of the worst hills and intersections can be pre-treated for the first time this winter.
"We have about $20 invested so far (in anti-icing) so we can do some testing and see if it works," he said. "If it doesn't, we'll keep looking at other options. ... But anti-icing before the snow is the wave of the future."
Beet juice experiment
In addition to salt and magnesium chloride, Duluth has tested some designer anti-icing agents on City Hall sidewalks, using a concoction made from salt brine mixed with sugar beet juice. The stickiness of the juice helps the salt adhere to the concrete or blacktop and may keep it from melting at colder temperatures. When added to salt brine, one beet juice product, called GeoMelt, has allowed crews in some cities to cut salt use by 30 percent because it sticks longer and works well below zero.
But state officials note that plant-based additives may spur weed or algae growth. And though MnDOT has more than 40 chemicals on its approved list for melting snow and ice, most are far more expensive than salt alone.
"There are lots of options, but it has to be something we can afford," Fleissner said. "But if the stuff lasts longer and we can use a lot less salt, it may pay for itself."
Until then, cost considerations put the city in the same boat as consumers. For them, if all else fails, Northern Tool and Equipment's Amdahl has two words of advice: