January 21, 2011

The best way to clear snow, ice

When you try to navigate the pavement in the days after a snowstorm, you often run into all sorts of snow and ice combinations in various stages of melting and freezing on streets and sidewalks.

When you try to navigate the pavement in the days after a snowstorm, you often run into all sorts of snow and ice combinations in various stages of melting and freezing on streets and sidewalks.

The people who get out to shovel as soon as the snow ends probably do the best by pedestrians. And those who pour on the de-icer instead may only create a slimy, slippery mess.

De-icer does not provide traction for walking safely on slick pavement, said Ward Upham, horticulturist with K-State Research and Extension. Shoveling early is the best way to clear the walks, he said.

"As its name implies, a de-icer can help you clear away ice. It is not a snow shovel substitute," he said.

Upham has these other tips to help you the next time the snow falls:

* De-icer can make walking safer if it is applied before a storm or after snow has been cleared out of the way. De-icers' basic purpose is to break the bond between ice and pavement, usually by causing the ice to melt. In general, the thinner and newer the ice, the better de-icers work.

"You need to follow up with a traction provider only if you leave slick spots or slush behind, either of which can make walking hazardous," Upham said.

None of the material that can be used for traction — from cinders to sand to kitty litter — works as well as getting out the shovel and removing snow and ice as soon as a winter storm subsides, he said.

* Be aware that de-icer or traction materials are often tracked into the house. If you use them, "you may want to make people leave their shoes at the front door," Upham says.

If slush is loaded with de-icer, it can be slimy. In turn, when the slimy stuff comes indoors on shoes, it can leave spots that dry and leave chemical residues. Traction materials such as sand and kitty litter also leave messes that can be hard to clean up.

* Once the need for traction materials is over, they should be cleaned up.

"When you leave such materials on your sidewalk, they end up in one of two places," Upham said. "They get stuck in the edges of your landscape. Or, snow melt and rain take them into your street's gutter, down into the storm drain system and out to a nearby natural body of water. There, they become a space-filling pollutant....

"A buildup of de-icer chemicals can injure the plants and grass growing along walks and driveways. It also can pit concrete — an impact you may not notice until months later."

Types of de-icers

De-icers can easily be overused if homeowners don't know the limitations of the product they've purchased and decide that putting down more will take care of the problem, Upham said.

Here are the five major ingredients used in chemical de-icers and when they should be used:

* Calcium magnesium acetate (CMA) is an acceptably "green" and typically more expensive product made from dolomitic limestone and acetic acid (the principal compound of vinegar). Its performance decreases as the temperature drops below 20. But it does not form a slimy brine as some other de-icers do. CMA also has little effect on plant growth or concrete surfaces.

* Calcium chloride has been the traditional go-to in recent decades. It will melt ice to about 25 degrees below zero. It gets to work fairly quickly but it does form a slippery, slimy surface on concrete and other hard walkways. It probably won't hurt plants unless excessive amounts are used.

* Sodium chloride (rock salt) is the oldest, cheapest option. It is effective down to about 12 degrees. Splashed or melted onto nearby surfaces, it can seriously damage plants, metals and soils. On concrete, it increases the impact of winter's freeze-thaw cycles, so it can be particularly damaging for new pads and sidewalks.

* Potassium chloride is a naturally occurring material also used as a food-salt substitute and a fertilizer. It can melt ice when temperatures are in the teens. It's not widely available as a de-icer ingredient, though, because the compound's high salt index can lead to serious plant injury, above and below ground.

* Urea (carbonyl diamide) is a fertilizer sometimes used to melt ice in temperatures down to 21 degrees. Urea is only about one-tenth as corrosive as sodium chloride. It's less likely to burn plants than potassium chloride. But it can contaminate ground and surface water supplies with nitrates.

Related content