The de-icer that tames Western roads

Dumping magnesium chloride on winter roads keeps the traffic moving — but how safe is the stuff?

  • Jungle Fuhrman works as a mechanic in Eagle, Colorado, the new Rust Belt of the West

    Allen Best
  • Mag chloride by any other name

    Colorado Department of Transportation
  • This sign post is corroding due to repeated applications of the de-icer magnesium chloride. Location: Speer Boulevard, near Arapaho Street, in Denver, Colorado.


INTERSTATE 70, COLORADO — It’s a catch-22 of winter driving: To allow faster and safer travel, transportation officials in the 1990s began splashing a salt-based de-icer called magnesium chloride on highways before and during snowstorms. It lowers the freezing point by about 10 degrees, making mountain highways less hazardous, proponents say.

But the grayish, gooey substance must be washed immediately from cars and trucks, including the undercarriages, to prevent corrosion of electrical wires, nuts, brake shoes and even ball joints. "If the ball joint goes, you have no control; the car goes wherever it wants to go," says Gary Bergman, the owner of Meadow Creek Tire in Frisco, Colo. "When that happens, you can kiss your rear end goodbye."

In other words, "mag chloride" makes roads safer, but it makes vehicles using them less safe. And although drivers may travel faster, they spend extra time and money washing their cars. Other consequences may not become evident for decades — and some critics say they could include contamination of roadside streams, weakening of concrete bridges, negative effects on wildlife and perhaps even cancer in humans.

Transportation officials think such fears are overwrought. Mag chloride is more effective than other road salts and has reduced accident rates, kept mountain highways open, and caused only minimal damage to the environment and to vehicles. "We have never said it was a perfect product," says Stacey Stegman, spokeswoman for the Colorado Department of Transportation (CDOT). "Each product will have its downside, but we think this product achieves the best balance."

Drink it up!

Colorado is at the forefront of magnesium chloride use in the West. Like most Western states, it long shunned salt, instead using sand for traction. Pitted and cracked windshields from flying rocks were the cost of driving in snow country.

But when sand is ground up by traffic, it becomes dust that hangs in the air — a major component in Denver’s infamous brown cloud. Sand pollution also turned creeks along Interstate 70 into beaches, and aquatic life suffocated under decades and tons of migrating sand pebbles.

So, in 1996, the state began slopping mag chloride on I-70, the major artery across the Colorado Rockies. The highway, which was closed 46 times the previous year, remained open almost continuously, in part due to the mag chloride. Use of the de-icer, which comes from factories along Utah’s Great Salt Lake, has now been expanded to secondary highways in Colorado; application has increased 1,400 percent in the last eight years, to 10.62 million gallons.

Within a few years of its introduction, however, several mountain communities, including Aspen, Basalt and Summit County, banned mag chloride, variously citing safety, health and environmental concerns. According to Gary Lindstrom, Summit County commissioner, "The community as a whole is very upset that all of the trees are dead along the roads. CDOT claims that mag (chloride) does not kill trees, but they can’t explain what does."

CDOT also disputes claims that the chemical could have negative effects on aquatic life. A study by Colorado State University Professor William Lewis found that magnesium chloride applied to roads is rapidly diluted, causing insignificant effects. In a second study, Lewis absolved the de-icer of risks to human health. At a legislative hearing, CDOT executive director Tom Norton sipped a beaker of the lemonade-looking substance, diluted with water to a ratio of one part per 500, the same level as in streams adjacent to roads.

But Norton’s public whistle-wetting missed the point, says Lee Cassin, Aspen’s municipal director of environmental safety. Mag chloride itself may not harm streams or people, but it could be dangerous in combination with other elements. We just don’t know, she says. To be safe, Cassin advocates alternatives — using sand, but sweeping it more often, driving more slowly, and using other de-icers.

"Rust Belt of the West"

The argument over magnesium chloride is being waged across the West. Last year, citizens in Kalispell, Whitefish, and West Glacier, Mont., appealed to the Flathead County commissioners to discontinue its use. The speakers — mechanics, loggers and truckers among them — testified to the damage they had seen and expressed worries about the de-icer’s effects on wildlife. "I hate the stuff," said Bill Anders, a carpenter in Kalispell. "I hate it with a passion."

If magnesium chloride is not the miracle some once thought, Montana transportation officials still say it’s the best answer available for the money, and that it achieves what the average person cares most about, which is driving safety. But critics in Montana, like those in Colorado, say the real question is what price we’re willing to pay for our get-anywhere-fast transportation imperative.

"Jungle" Fuhrman, a mechanic in Eagle, Colo., has seen bolts that never broke before snap as a result of mag chloride-caused corrosion. He calls I-70 the new "Rust Belt of the West." But that isn’t what eats at him the most about mag chloride: "How important is it that 24 hours a day, seven days a week, we be able to drive across the state on I-70?" he asks. "We’re in too much of a hurry. Why can’t we stand back and watch a snowstorm once in awhile?"

The author writes from Arvada, Colorado.

Colorado Department of Transportation

CDOT research reports

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