Where does all the deicer go? 

The arrival of the snow season brings more than fun in the slopes; it also brings hazardously slippery conditions to city streets. To counter slick conditions, the city uses a liquid magnesium chloride mixture called FreezGard CI Plus, described by Peter Nielsen, Missoula County Environmental Health Unit Supervisor, as “concentrated Salt Lake water.”

In 1992 the city of Missoula abandoned the use of sand and salt on main city streets to comply with air quality regulations. While liquid deicers have minimized levels of air contamination, a two-year study by the Missoula Water Quality District concluded in 1997 that their use boosted the amount of heavy metals in the city’s groundwater. But, the study said, the boost did not generally pose a significant risk to water quality—a stance that city officials echo today.

“At this point we don’t have any reason to believe that there are significant environmental impacts on groundwater or surface water,” Jon Harvala, Missoula County Environmental Health Specialist, said. “We look at it the best we can, and the nearest we can tell, the products that are used now are safe.”

Neilsen said the city of Missoula has some of the most stringent standards for deicer use in the Northwest, and rigorously tests the effects of deicers on the environment. The deicer’s environmental safety, Harvala says, isn’t in question. The only argument has been over the deicer’s effectiveness.

“Under the right conditions (liquid deicer) works very well, it has its strengths,” Street Division Superintendent Brian Hensel said, adding that most complaints come from people upset over the corrosive effect deicers have on vehicle wires, brake parts, bicycles and bridges.

The corrosion inhibitor in FreezGard Plus is an agricultural byproduct derived from the processing of corn. “Oftentimes it is those inhibitors that provide the trace contaminants,” including arsenic and lead, Harvala said. “That’s why they have to be tested to demonstrate they meet the water quality standards.”

Clark Fork Coalition staff scientist Dr. Chris Brick said the amount of deicer applied to streets was the biggest concern when it was first used in 1992, and continues to be a concern now. Brick said liquid deicers are relatively safe as long as maintenance crews abide by the city’s application standard of no more than 30 gallons per lane mile.

By this date last year the city had used 81,000 gallons of deicer. So far this year, 174,000 gallons have been sprayed.

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