Those familiar carpets of blue salt crystals could soon be a thing of winters past on Minnesota roads. Instead, expect to see more brine.
Liquid anti-icing agents, like salt brine, are the current stars of the winter maintenance world, while granular anti-icing agents — like sand and rock salt — get used more sparingly and for specific purposes, according to the Minnesota Department of Transportation, academic researchers and environmental consultants.
Reducing the rock salt usage is important. A recent study projected that chloride (salt) contamination in some Twin Cities lakes will make them too salty to support native aquatic life by 2050.
Experts say MnDOT is taking a step in the right direction by using more brine.
"To really oversimplify, if you see an organization where the liquid use is going up and the granular use is going down, that's real progress," said Connie Fortin, president of local environmental firm Fortin Consulting.
This past winter in the metro area, MnDOT used four times as much brine as it did the year before and about double its five-year average.
MnDOT used more than 3 million gallons of brine statewide this winter, a mark it last reached during the winter of 2012-13 that stretched nearly to May.
MnDOT's use of rock salt remained at roughly the five-year average. It's hard to say, though, if the higher brine usage meant crews used less rock salt, because winters come in all shapes and sizes.
The amount of material used each year can depend on factors that are nearly impossible to measure, like how much packed snow was still on the ground from the last storm or whether a storm started during rush hour.
For Steven Lund, state maintenance engineer for MnDOT, the public safety advantages are clear. Just before a storm hits, brine can be applied to keep snow and ice from attaching to pavement. Bonus: Brine is about 75 percent water.
Lund said MnDOT operators "don't just go out and blindly distribute product. They want a clean environment because they live in these communities, too."
The salinity problem in the state's lakes and rivers isn't solely due to the salt on the highways. Homeowners clearing walks and private vendors clearing parking lots introduce a significant, but difficult to measure, amount of chloride into the environment, and water softeners are also a key factor, according to Brooke Asleson of the Minnesota Pollution Control Agency.
Asleson said there's no practical way to remove chloride from water on a large scale. Once it's in, it stays in. It can leave Minnesota's waters eventually, when contaminated water molecules move out into other bodies of water.
Lawrence Baker, a research professor in bioproducts and biosystems engineering at the University of Minnesota, said even if we significantly reduce our salt use now, it might be decades before we see decreases in groundwater contamination.
The best medicine, according to Baker and Asleson, is keeping the chloride from getting into the environment.
How can we reduce salt use? Brine is a good start. Fortin's consulting firm trains winter maintenance personnel to get the same results with less salt, often recommending new technologies that allow for more precise distribution.
Why can't we just use more sand? Lund, the MnDOT engineer, said the transportation industry has largely moved away from sand because it clogs ditches and drains and does nothing to break up snow and ice. MnDOT now uses sand only in specific areas — like on shaded hillsides or at crash sites — where an immediate traction boost is needed.
Asleson and Fortin both pointed to alternative pavements and road materials that could reduce the need for plowing and salting, but they said few local jurisdictions have shown interest.
This all raises a tough question: Can modern humans live in winter climates like Minnesota's without having a significant negative impact on the environment? Can we keep our public safety, our drivable roads and our pristine lakes filled with lively fish?
These experts all agreed it'll take some work — and lower expectations — but that it seems doable.
"There may be times where [authorities] just say, 'Don't drive tomorrow morning; we can't get it off quick enough.' Or 'Drive very slowly; we're trying to do this in an environmentally sensitive way, and it'll take a little longer,' " he said.
Fortin said that lowering the level of service isn't viable in our busy culture but that a better option would be to resist increasing the service level.
"If I'm in Aitkin, Minnesota, and I can park in a lot that has snow on it, let's keep it that way instead of melting every snowflake," Fortin said.
Micah Emmel-Duke is a University of Minnesota student on assignment for the Star Tribune.