Each winter, state, county, and local transportation departments stock their arsenal with the tools necessary to face whatever winter storms may bring. This arsenal includes a variety of chemicals to melt snow and ice. This preparedness has a high price tag; in the U.S., an estimated $2 billion is spent each year on chemicals, materials, labor, and equipment for winter road maintenance.
The most commonly used and economical deicer is sodium chloride, better known as salt; 15 million tons of deicing salt are used in the U.S. each year. Salt is effective because it lowers the freezing point of water, preventing ice and snow from bonding to the pavement and allowing easy removal by plows. However, the use of salt is not without problems. Salt contributes to the corrosion of vehicles and infrastructure, and can damage water bodies, ground water, and roadside vegetation. These issues have led to the investigation and use of other chemicals as substitutes for and supplements to salt. Other deicing chemicals include magnesium chloride, potassium acetate, calcium chloride, calcium magnesium acetate, and potassium chloride (these are described below).
Abrasives such as sand are often used in conjunction with deicing chemicals to provide traction for vehicles, particularly on corners, intersections, and steep grades. However, when sand is overused, it often ends up in the environment, either as dust particles that contribute to air pollution or in runoff to streams and rivers.
Airports present another area of concern with respect to deicing chemicals. The Federal Aviation Administration (FAA) requires that aircraft surfaces be deiced and antiiced to ensure the safety of passengers. However, when performed without prevention measures in place, airport deicing operations can contribute to contamination of ground water and surface water supplies.
Road Salt Storage. Many of the problems associated with contamination of local waterways stem from the improper storage of deicing materials (Koppelman et al., 1984). Salts are very soluble when they come into contact with stormwater. They can migrate into ground water used for public water supplies and also contaminate surface waters. More information about road deicing materials can be found at the American Association of State Highway and Transportation Officials website.
Winter Roadway Deicing/Anti-icing Operations: Approaches to Help Keep Roads Clear and Waters Clean. This 2014 webinar from the U.S. EPA and Federal Highway Administration was recorded and is available to be viewed on demand.
Manual for Deicing Chemicals: Application Practices. This report summarizes the results of a study about minimizing the loss to the environment of chemicals used in controlling snow and ice on highways.
Source Water Protection Practices Bulletin Managing Highway Deicing to Prevent Contamination of Drinking Water. This bulletin focuses on the management of highway deicing chemicals. See the bulletin on storm water runoff for additional management measures
Airport Deicing Effluent Guidelines. The Federal Aviation Administration requires airlines and airports that operate during icy conditions to perform deicing and anti-icing of aircraft and airfield pavement. This ensures the safety of passengers and cargo operations. However, when performed without discharge controls in place, these deicing operations can result in environmental impacts. Airports are required to obtain stormwater discharge permits under the NPDES program and ensure that wastes from deicing operations are properly collected and treated.
Source Water Protection Practices Bulletin Managing Aircraft and Airfield Deicing Operations to Prevent Contamination of Drinking Water. This bulletin addresses two basic types of deicing/anti-icing operations that take place at airports: the deicing/anti-icing of aircraft, and the deicing/anti-icing of paved areas including runways, taxiways and gate areas. It also discusses some source water contamination prevention measures available for use at smaller airports.