EFFECT ON WATER & NATURAL ENVIRONMENT

When weighed against the need to maintain roads and highways in safe condition, the practical question is: Which deicer can be used most effectively with a minimum of impact on the environment?

The effect of deicer runoff on surface water and groundwater has been the focus of a great deal of research by government agencies and academics. Collectively, the research agrees that no deicer can claim to be completely harmless to the environment. As a starting point, comparisons of the potential environmental impacts of deicers published by the National Cooperative Highway Research Program show that all of the commonly employed deicer chemistries have environmental drawbacks.¹

Generalized Potential Environmental Impairment Related to Common Snow and Ice Control Chemicals¹

Managing Environmental Impact

To minimize environmental impacts, many researchers and government agencies emphasize the importance of using smaller quantities of deicers to increase the efficiency of mechanical ice removal instead of melting ice completely in place and producing high volumes of deicer-saturated run off. One publication by the United States Environmental Protection Agency, “Storm Water Management Fact Sheet – Minimizing Effects from Highway Deicing”,² recommends a coordinated approach incorporating effective stockpile containment, careful calibration of spreading equipment, pretreatment of surfaces when possible, and mechanical removal as effective means to minimize the impact of deicers. See: The Case for Calcium Chloride.

How Ice Melters Affect the Environment

Much of the concern related to the environmental impact of ice melters is in regard to chloride contamination of water and soil. Before discussion of the issue, it is important to recognize that chloride occurs naturally in the environment. For example, the seawater that covers 70% of planet earth has about 2% chloride content. Sodium chloride is also known as ordinary table salt which we consume every day. Chloride also occurs naturally in foods that are widely considered healthy, including seaweed, rye, tomatoes, lettuce, celery and olives. The National Academy of Sciences, Food and Nutrition Board publishes Recommended Dietary Allowances (RDA) for chloride, identifying age group- and gender-specific goals for daily consumption aimed at maintaining good health. Physicians say too much chloride (or salt) in our diets is not healthy. But the RDA recommendations suggest consuming small amounts of chloride daily is not a health threat. The same can be said for chloride in the lakes, streams and soil around us.

Concern about ice melter impact largely surrounds the introduction of excessive amounts of chloride into soil and water near pavement where these materials are applied. Although chlorides are present already in the natural environment, application of ice melting materials can result in local spikes in chloride concentrations in nearby bodies of water and soil. While there are many different viewpoints about the short- and longer-term impacts of specific deicer materials, there is general agreement that chloride, sodium, calcium and other components of ice melter products can be readily measured in surface water, groundwater and soil near roadways where deicers are used. Since common sodium chloride, or rock salt, is the most widely used deicer, most research has focused on this product.

Impact on lakes and streams – Researchers have found that the presence of chlorides in surface water is often seasonal and tied to winter use of deicing materials. Studies conducted or sponsored by the United States Geological Survey (USGS) and the Wisconsin State Laboratory of Hygiene, the Minnesota Department of Transportation, and the New York State Department of Transportation all documented seasonal increases in chloride and other deicers in the environment.

The USGS/Wisconsin study of streams in the Milwaukee area found a correlation between chloride levels and the health of some aquatic life, while researchers in New York observed that algae and other tiny organisms were more affected by chloride levels than fish. Researchers in New York further note, however, that deicers levels in typical bodies of water were generally lower than those toxic to small organisms. ^3,4,5

Strategies can be employed to minimize deicer introduction into the natural environment. These strategies can include matching deicer application rate to temperature conditions, reducing accumulation of snow and ice on roadways through the use of snow fences or other measures, predicting when to apply deicers, improving the application of deicers with better distribution systems and allowing deicers sufficient time to work before plowing and reapplication. For specific deicer application recommendations, see: Application Best Practices.

¹NCHRP Report 577: Guidelines for the Selection of Snow and Ice Control Materials to Mitigate Environmental Impacts. National Cooperative Highway Research Program, Transportation Research Board of the National Academies, 2007.
²U.S. EPA, Storm Water Management Fact Sheet – Minimizing Effects from Highway Deicing, Office of Water, EPA 832-F-99-016, 1999.
³A Fresh Look at Road Salt: Aquatic Toxicity and Water-Quality Impacts on Local, Regional, and National Scales; S. Corsi, S. Graczyk, S. Geis, N. Booth, K. Richards, Environmental Science and Technology, 2010.
⁴Study of Environmental Effects of De-Icing Salt on Water Quality in the Twin Cities Metropolitan Area, Minnesota; University of Minnesota, Department of Civil Engineering and Minnesota Department of Transportation; H. Stefan, E. Novotny, A. Sander, and O. Hohseni, 2008.
⁵Environmental Impacts of Winter Road Management at the Cascade Lakes and Chapel Pond, Clarkson Center for the Environment Report #1, Funded by the New York State Department of Transportation; T. Langen, M. Twiss, T. Young, K. Janoyan, J. Stager, J. Osso, H. Prutzman and B. Green, 2006.
¹ The Effects of Deicing Chemicals on Turfgrass, D. Minner and B. Bingaman, Iowa State University, 1996.