Credit: Photo: Halliday Technologies Inc.
The Ohio DOT uses the RT3 “real time traction tool” to map conditions around Columbus and Cleveland during winter storms. Towed behind or attached to the undercarriage of a truck, the testing wheel compares the friction of wet or treated pavement compared to dry pavement by transmitting signals to an onboard computer.
Credit: Source: Minnesota Pollution Control Agency, Winter Parking Lot and Sidewalk Maintenance Manual
Melting characteristics of deicing chemicals
WAYS TO LIMIT ENVIRONMENTAL IMPACT
While keeping in mind that traffic safety is the primary goal, you can do a lot to reduce environmental damage due to snow and ice control efforts.
Use the right product for the right purpose. Because sand has no affect on melting, don't use it if that's what you're trying to achieve.
Various deicing chemicals—calcium chloride, potassium acetate, magnesium chloride, sodium chloride, and calcium magnesium acetate—are effective only above certain temperatures (see chart above), so be sure to use a material that's appropriate for conditions. (Remember that pavement temperature, not air temperature, is the governing factor.) The acetates cost more, so they're less commonly used, but they also have less environmental impact.
“The acetates act more like a fertilizer when they get into the water, accelerating algae growth,” says consultant Fortin. “But they don't accumulate like chlorides do.”
Use deicing products efficiently. Prewetting helps salt work better and reduces waste. Calibrate equipment regularly to ensure that deicing materials are distributed where and how they should be. When applying deicing chemicals in liquid form, use appropriate concentrations of salt in brine solutions and set equipment for streaming rather than spraying for the most effective distribution.
Whenever possible, look toward anti-icing rather than melting and removal efforts. Spreading chemicals before a storm helps prevent ice from forming, which enhances safety and allows you to use chemicals more sparingly. Concentrate deicing efforts in key areas, such as intersections where cars need to stop and start.
Investigate equipment that measures surface traction in real time. By gauging and transmitting actual road conditions, these devices help determine proper deicer application rates and how to deploy equipment where it's needed most. They allow operators to measure and compare the field performance of various techniques and products under varying conditions.
Locate and manage sand and salt storage sites carefully, to avoid contaminating salt-vulnerable areas.MATCH THE METHOD TO THE CONDITIONS
Across the northern United States and Canada, officials have made progress in implementing snow clearance practices that are effective, economical, and environmentally friendly. Ongoing research, particularly at the state level, as well as new tools and techniques being developed, offer promise for continued improvement.
Have a variety of tools, materials, and techniques available, and learn how to match the method to the conditions in any particular weather event. Using the resources at your disposal to get the best possible handle on weather movements and pavement conditions makes for more effective and efficient control. Use only the appropriate type and amount of chemicals to save money and limit environmental impacts.