Salt is a convenient and commonly used de-icer; it is also associated with a number of consumer and environmental concerns.
The first big snowstorm of winter covers the landscape with a fresh blanket of white, briefly replacing ordinary surroundings with a sparkling new world. However, the beauty of new-fallen snow is tempered by the dangers of icy streets and sidewalks. By packing down snow, vehicles and pedestrians create dangerous roads and walkways. Warm daytime temperatures melt snow, which freezes again in the evening. Often, you need more than snowplows and snow shovels to keep the streets and sidewalks safe.
Deicing salt has long been an effective and inexpensive way to clear snow and ice from roadways, driveways, sidewalks, and commercial areas. Although salt is a convenient and commonly used deicer, it is also associated with a number of consumer and environmental concerns. As a result, some snowy cities are experimenting with alternative deicers.
The Ravages of Salt
Plants, soils, and groundwater suffer from the salt splash of passing vehicles. According to the University of Minnesota Extension Service, salt spray can disfigure broadleaf and evergreen trees and shrubs and kill buds and twigs. Absorbed through the soil, damaging levels of salt can result in abnormal fall color, needle-tip burn, and browning of roadside leaves.
Salt dissolves easily and can percolate through the soil into underground aquifers, which often provide drinking water to surrounding communities. A Toronto study has revealed that only 45 percent of salt applied to roads washes away down surface waterways. Shallow aquifers absorb the remaining portion. Improper storage of salt supplies has also caused severe cases of soil and water contamination. If salt stockpiles are left uncovered, a lot of salt can be absorbed into adjacent soil and water.
Sidewalk salt can have the same detrimental effects as road salt. Alternatives for sidewalks include coarse sand, kitty litter, sawdust, or even fertilizer. You should be cautious with fertilizer because too much can damage your landscaping. Also, fertilizers that contain iron sulfate will stain concrete. If you prefer salt for deicing, use it sparingly.
Environmentally Sound Deicers
Highway crews use a combination of salt and sand for deicing and traction on icy roadways; however, the use of sand has led to another set of problems for some areas. When sand is applied to roads, it is ground into dust by vehicles and thrown into the air. This airborne sand is considered particulate air pollution that is regulated by the Environmental Protection Agency (EPA). Cities using sand for deicing must meet EPA air-quality standards or risk losing federal funds. Emerging alternative products include liquid deicers such as magnesium chloride and an ethanol by-product called Ice-Ban, and sand alternatives such as crushed shale or slate.
There are several ways to protect landscaping exposted to salt.
Magnesium chloride is a naturally occurring substance that is applied to roads in liquid form. The liquid can prevent ice from bonding to pavement and dissolve thin layers of ice already formed. Magnesium chloride is often applied to highways and busy intersections just before a storm is predicted to hit.
The Colorado Department of Transportation applied about 5 million gallons of magnesium chloride to state roads during the 1997–98 winter season, and that amount is expected to increase. In the Denver metropolitan area, where particulate air pollution is a concern, magnesium chloride is used almost exclusively. Several studies have been conducted in Colorado to evaluate the environmental impact of magnesium chloride, including a three-year study of its effect on aquatic life. Preliminary results are encouraging, reports Werner Hutter of the Colorado State Highway department. While laboratory tests reveal high concentrations of magnesium chloride can be toxic to aquatic life, field tests demonstrate the substance dilutes quickly and, once diluted, poses a minimal risk to aquatic systems.
In response to citizen complaints, the state of Colorado is conducting a study to evaluate the impact of magnesium chloride on air quality. That study is expected to be complete at the end of the 1999–2000 winter season. The state is also working with the trucking industry to gauge the effects of magnesium chloride on vehicle corrosion.
Ice-Ban, a by-product of the process that turns corn into ethanol, is a sticky brown liquid with a strong, somewhat sweet odor. It is an all-natural, nontoxic substance that is most effective against icy conditions at very cold temperatures. Though the product has been used on state highways without incident, its use in downtown Denver prompted many complaints about the odor and stickiness. There are also some worries that the sweet liquid may attract wildlife onto roads.
For traction on icy roads, city officials in Sheridan, Wyoming, have successfully replaced the traditional sand/salt mixture with a crushed shale product. Although the shale is almost twice as expensive as sand/salt, it provides better traction, is easier to apply and clean up, causes less rust damage, and reduces windshield and headlight damage. It also reduces particulate air pollution in Sheridan.
Experts agree that icy roads will continue to be a problem for state and local governments. While more studies are needed, the new products in the marketplace may replace some traditional sand and salt deicing methods.
Lisa Nelson is a Boulder freelance writer who formerly worked for the Colorado Office of Energy Conservation.
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