Magnesium chloride use encounters road bump

By Stephen Clearheart Johnson
North Forty News

In the early 1990s Colorado became a leader in the use of magnesium chloride as a dust suppressant and stabilizer on dirt roads and a deicer on paved highways.

Now, Colorado has become a leader in learning the downside of this chemical. Commonly called "mag," it has the formula MgCl2.

This chemical replaced the use of a rock-salt/sand mixture for deicing and was quickly adopted by the Colorado Department of Transportation because it cost much less and could be spread more easily and quickly. In 2006-2007, CDOT used 9 million gallons, at a rate of about 40 gallons per lane mile.

Mag also reduced stream sediment previously caused by sand and greatly helped reduce Denver's persistent violations of EPA air quality standards for particulates. Using mag reduced wintertime accidents by up to 76 percent in Glenwood Canyon and 53 percent at Denver's Mousetrap.

Detractors spoke up early to question the environmental impacts. Arborists, nursery and other tree workers pointed out that salts are poisonous to trees.

CDOT countered with a 1999 research study that concluded "...highly unlikely to cause or contribute to environmental damages at distances greater than 20 yards from the road." Again in 2000 the Colorado Department of Public Health issued a report that stated, "These deicers pose no worse human health threat than do salt/sand mixtures."

Other states like Montana and many county and city street departments cited the Colorado studies to justify their use of mag. One city of Boulder web site still maintains that mag is "a plant nutrient."

But the detractors became more numerous. Electrical cooperatives in Colorado began to experience an increase in outages and pole-top fires attributed to insulators becoming coated with mag chloride. A USDA study backed them up by noting that mag reacts adversely with aluminum.

Then safety concerns began to come in from motorists and truckers who found that mag could affect wiring and metal frames, especially where it settled in joints where it could not be washed out. Worse, it affected brake shoes and ball joints. School bus operators began to complain that it shorted out their radio antennae.

The complaints have become rancorous. A recent editorial by the Truckload Carriers Association stated, "CDOT's insistence on scientific proof of wiring corrosion is just a way to shift the problem away from them."

Then new studies began to come out. First, a study by the University of Northern Colorado in 2004 and most recently a study at Colorado State University, in which Larimer County participated, that showed that up to 15 percent of trees along treated roads were damaged, especially down slope and up to 200 feet from the road. The chloride ions, it seems, inhibit a tree's ability to take up water. Other vegetation is variously affected, with junipers showing the most damage.

Although Larimer County briefly experimented with mag as a deicer 10 years ago, County Road and Bridge Director Dale Miller chose not to use any liquid deicing program. Because mag used in a deicing role must be applied before a storm, Miller thought that it was not cost effective to keep crews and equipment on constant standby.

Miller also noted an accident potential with the use of liquid deicers in winter weather. Indeed, the cities of Colorado Springs and Sante Fe, N.M., recently experienced accidents and even deaths when mag caused streets to become icy before the snow fell.

But Larimer County has used mag for dust suppression and stabilization on dirt roads. This changed in the summer of 2007, when Larimer County participated in the CSU studies. As the results came in, Miller modified the use of mag and began substituting a lanolin-based product in forested areas or areas of steep curves and side slopes.

Miller intends to keep using mag in some areas. "We have not found a product as useful or economical as mag chloride," he said.

Miller noted that Larimer County used 1.1 million gallons in 2007, down from 3.3 million in 2005.

When asked about the safety of the lanolin product, Miller said, "Lanolin is not supposed to be harmful, but that's what we were told about magnesium chloride."

He will continue participating in CSU research studies to look at areas switched from mag to lanolin and new plots treated with lanolin only.

"We are conscientious about the materials we use," he said. "We're not going to harm the environment just for the sake of cost-effectiveness."