by Jim Baumann and David Thompson
Madison’s waterways are clearly impacted by winter salt use. Steadily increasing levels of chlorides from deicers have been found in all of Madison's Lakes, and in our wells.
Odana Pond, at the western end of the Lake Wingra watershed, is listed as an impaired water due to very high chloride levels. Most of the salt is from highways, streets and parking lots, but home use also contributes.
Vultures feast on carp at Odana Pond-->
All deicers are bad for the environment
We checked the formulas for most deicer salts now available in Madison. All are harmful to the lakes, your garden, and concrete; Most contain chloride. Some, like Pet Safe or Ace Ice Melter, even contain urea, a fertilizer. Urea causes growth of toxic algae in the lakes.
The claims on the labels, like "safe for the environment" or "safe for concrete," are false. So if you have ice on a slope, we recommend spreading sand.
If you must use deicer, consider these ways to reduce the quantity...
- Limit use to no more than one pound of salt (NaCl) per 200 square feet of ice.
- A heaping 12 ounce cup should be enough for a 60 foot icy sidewalk
- A hand-held spreader helps you spread the salt evenly.
- More salt does not mean more melting.
- Salt will not work when the temperature is 15° F or lower.
- If salt is visible on dry pavement, sweep up the extra salt for future use.
- After March 1, most snow will melt within a few hours of falling.
Let the sun do your work
Consider using the sun to remove ice on your sidewalk. Few people realize that ice evaporates directly to water vapor, even when temperatures are well below zero. It’s called “sublimation.“
You can speed sublimation by keeping your sidewalk shoveled. Even if there is a thin layer of snow or ice remaining on the pavement, the sun will penetrate, heat the pavement underneath, and cause the overlying ice to sublimate. If you sweep away a fresh dusting of snow, or chop some of the ice, the sun heats the spot of bare pavement, causing the surrounding ice to evaporate even faster. Sublimation works even when it’s cloudy or really cold.
If you read the labels on deicer sacks, they instruct you to shovel snow first, and to remove any slush that forms. The same method applies if you are using the sun to do your work. So why not just forget the salt?
So touch up your sidewalk before you go to work, and let the sun do the rest of the work.
Dealing with thick ice
Ice forms when you don't remove all the snow--as happens with some snow blowers. Another cause is when people walk on the snow, before you remove it. The best defense against ice is to remove all the snow before people walk on it
It usually takes a few days for the remaining snow to turn to ice. During that time, you can easily chip off the packed snow with an ice scraper. Once the pavement is mostly bare, the sun will do the rest.
If you have a patch of very slick ice, it may be a sign that runoff is pooling on your sidewalk--trapped by the higher turf on either side. The best remedy is to build a small rain garden next to the problem area.
Note: the sand that the City provides in barrels around town is 15% salt.
Salt--not worth the harm
Salt does work faster than relying on the sun. But salt is useless when temperatures are low. And when you consider the harm, it simply isn't worth the faster melting.