Are there environmentally friendlier ways to de-ice pavement besides using salt?
—Heidi David, Concord, NH
Although salt and various salt derivatives melt ice effectively and make both walkways and roads safer, they can be damaging to the environment. After salt is applied, it washes off paved surfaces into storm drains or onto adjacent ground, and can then be carried into nearby bodies of water. According to The New York Times, this salty runoff poisons fish and wilts vegetation. It also corrodes metals, damages concrete and poses health risks to people with high blood pressure.
Some studies have also shown that salt applied to road surfaces increases automobile collisions with wildlife, especially white-tailed deer that are attracted to natural and artificial salt deposits in their normal course of feeding.
Despite these facts, salt remains the cheapest and most effective way to keep pavement free of ice. According to materials consultant Henry Kirchner, individuals can effectively use salt with minimum impact: “Do not use a chemical deicer to melt every bit of ice,” says Kirchner. “Use only enough to break the ice/pavement bond, then remove the remaining slush by plowing or shoveling.” All snow should be cleared away first, and the ice should be chipped off and moved away from water supplies and vegetation.
For small jobs, it may be feasible to use more potent, less environmentally toxic de-icers like magnesium chloride or calcium magnesium acetate instead of rock salt. These stronger, though more expensive, compounds can be strategically applied before a storm to block ice from forming. Sand and cat litter can be used to provide temporary traction, but these materials may dog surface water and bury plants. Although many researchers are experimenting with even more benign de-icers, including by-products of corn and cheese processing, none of these compounds is currently available to consumers.
Perhaps the larger issue is how municipalities store and use large amounts of road salt. Many of the most severe cases of environmental contamination have been caused by improper storage. When salt is stored outside uncovered, rain and snow can carry large quantities to surrounding soil and water.
As to reducing salt use, many cities and towns simply don’t de-ice in flat residential areas, except during ice storms. Some use a mix of sand and salt, instead of pure salt. Also, salt spreading equipment that is well maintained will distribute salt more accurately and, as a result, use less. Additionally, salt that is wetted before being spread sticks better to the road.
According to the trade magazine, Better Roads, a product called Verglimit, a mixture of de-icing salts and caustic soda, can be mixed with asphalt roadway during paving. Its installation doubles the cost of surfacing a road, but helps reduce the amount of salt needed for de-icing roadways and, according to the magazine, “in certain conditions can eliminate the need for salting entirely.”
CONTACTS: The Salt Institute, (703) 549-4648, www.saltinstitute.org ; Better Roads, “Materials for Deicing and Anti-icing,” www.betterroads.com/articles/NewProds/Apr03bid.htm.