Salt, cinders central to de-icing plan

Most efforts to clear snow and ice are not detrimental to the environment.
Friday, February 20, 2004 | 12:00 a.m. CST; updated 5:51 a.m. CDT, Sunday, July 20, 2008

Regular snowfall and temperatures hovering below freezing for the past month have led to slick sidewalks and roads this winter in Columbia.

For drivers, this means being extra careful on the roads and relying heavily on city officials to keep the roads drivable.

Cities have several options for combating snow and ice accumulation on roads. Columbia uses two basic de-icers: rock salt and cinders.

Dennie Pendergrass, chief of operations for Columbia Public Works, explains “cinders are a product of our power plant and are used for traction, since they don’t have chemical reaction.”

Cinders are also easy to sweep away once the snow melts, meaning they rarely run off to the water drain. Cinders are usually used with salt.

The second option is rock salt or rock salt used with liquid calcium chloride. The latter combination produces a chemical reaction that generates heat.

Salt slows down in its melting process when the temperature reaches 18 degrees, but calcium chloride proves effective when temperatures dip as low as 5 degrees .

Sand or rock chips can also be used, but they are more difficult to clean from the streets and can end up in water drains. Other options, such as magnesium chloride, are more expensive.

In the past, Pendergrass has used urea, a de-icer that is better than salt in dealing with large amounts of snow and ice but more harsh on the city’s snow-clearing equipment.

“It was bought from Boone County farms but proved to be hard to manage due to its extreme corrosive effect on the equipment,” he said.

As far as the environmental impact de-icers have, Pendergrass said driver safety comes first.

“In our choices, we refer to updated studies, but the safety and the efficiency of the streets always come first in our service for the community,” he said.

Peter Motavalli, an assistant professor of soil nutrient management at MU, said the heavy use of de-icers in Columbia this winter has had a minimal effect on the environment, mainly because of the sheer amount of snow mid-Missouri has received.

“The presence of more snow simply means that, once melted, much more water will dilute the materials,” he said.

The various substances that can be used on roads receive a different evaluation depending on where they end up. The melted ice can either go from the street into the storm drain, or it can move from the sidewalk to the soil.

“Adding calcium chloride to rock salt, as the City of Columbia is doing, is actually beneficial to the soil, but it might never make it to a field,” Motavalli said. “If there’s a flat territory, the materials will most likely just settle there.”

If the materials encounter a frozen layer of snow, the nutrients won’t seep into the soil until spring, Motavalli said.

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