Slippery slope 

City grapples with responsible deicer options

When it comes to environmental issues, city officials are always balancing on thin ice. But Missoula Streets Superintendent Brian Hensel wants to vanquish the ice altogether.

Hensel’s charged with helping Missoula Public Works grapple with snow and ice on city streets this winter, as well as saving money. To that end, he convinced City Council to enact an emergency measure to allow him to use a granular deicing product, which, until Nov. 24, was prohibited under city guidelines.

The impetus for the measure is cost, but the debate doesn’t revolve solely around money. Environmental factors and corrosion must also be taken into consideration, a fact Hensel is keenly aware of. He plans to use a non-corrosive sodium chloride to complement the magnesium chloride the city has employed since 1991. While the product he’s chosen, IceSlicer Superblend, may have been prohibited without the emergency ordinance, Hensel’s convinced the effect on the environment will be comparable to the magnesium chloride. 

Historically, municipalities and state highway departments spread pure sodium chloride, aka “road salt,” to combat winter precipitation, and in some parts of the country, they still do. Experts concur that it’s the most effective deicer. When salt touches ice, it forms brine. The brine works its way down through the ice until it reaches the pavement. From there, it spreads along the street undercutting the ice.

However, studies show road salt severely harms the environment and can damage cars and infrastructure. In fact, the Pacific Northwest Snowfighters, a committee of the British Columbia, Washington, Oregon, Idaho and Montana state transportation departments, won’t approve a product for municipal use unless it’s at least 70 percent less corrosive than sodium chloride.

Before 1992, Missoula Public Works mitigated the rock salt issue by covering the streets in a mixture of salt and sand. That changed in 1997 when the Missoula City-County Air Pollution Control program was amended to limit the use of sand when temperatures rose above zero. Sand doesn’t melt, so when spring arrived, so did the dust. To combat the air-quality issues, the city went to a deicer, and to combat corrosion, officials chose liquid magnesium chloride, which has worked relatively well under some conditions, Hensel says.

The main problem boils down to cost. Last year Hensel says the city spent $118 per gallon on Freezgard O, the magnesium chloride he uses. This fiscal year, the price has risen to $133. With a corrosion inhibitor, Freezgard is 12.2 percent as corrosive as salt. Its downside, Hensel says, is that it’s expensive to transport and, since it’s 66 percent water, it only works well under some conditions. 

“It has its niche,” Hensel says. “If it’s 17, 18 degrees out, it works real well. If it’s a lighter snowstorm, you can see it working, it looks wet.”

But if the temperature drops, so does the effectiveness of the magnesium chloride, Hensel says.

“There’s literature out there that says it will work down below 10 or zero,” he continues. “That has not been my experience in Missoula, Montana. When it’s below about 15 degrees and it’s snowing, you have to over-apply it and over-apply it. I’ve also seen it refreeze.”

As a result, last year’s heavy winter forced Hensel to spend $216,873 to keep the roads clean, a substantial increase from his original $170,891 deicing budget. To cut these costs, he’s proposing the IceSlicer Superblend.

In 2001, Stormwater, a trade journal for surface water quality professionals, slammed sodium chloride after a study of its environmental effects. The report showed that sodium chloride harms wildlife, soil and drinking water, and it kills plant life up to several meters from the roadway. The study clumped all sodium chloride products under the road salt category, but didn’t distinguish between the pure form and a product such as IceSlicer.

City Council referenced the Stormwater report during debate over the emergency measure. Another report informing the discussion was published by the Colorado Department of Transportation in 2001 as well. It also concludes that sodium chloride is harmful to the environment, but states the effects are comparable to magnesium chloride. The difference, according to the Colorado study, is that sodium chloride decreases the stability of soil, causes slightly more air pollution and attracts wildlife. Other environmental effects are the same.

Hensel says that other cities in Montana use IceSlicer, including Kalispell, Great Falls, Bozeman and Havre—all with no complaints. Also, Hensel notes, the City-County Board of Health gave the new product its blessing after extensive testing. He says that the product the city is using is as green as such products get, meaning it contains no anti-caking agents or corrosion inhibitors, both of which are tough on plant life.

“We’re trying to use as an environmentally friendly product as we can,” he says.

Corrosion remains a point of contention. According to the Pacific Northwest Snowfighters, the IceSlicer that Hensel wants to use is 20 percent as corrosive as salt. But according to the 2001 Colorado study, the percentage is 80. This, Hensel says, is troubling.

“No one out there can give me a definitive answer about what any of this stuff does as far as corrosion,” he says. “There are so many different variables involved in it, everything from humidity to the amount of moisture you get with it, the type of vehicles, the application rates. There’s a lot of information out there but there’s not a whole lot on in-the-field measurements of corrosion. I’m pulling my hair out.”

As it stands, Hensel will turn to the sand trucks—about half his fleet—to try the IceSlicer on a limited basis.

The real test will come, he says, with the first snowstorm.
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