Section 11: Environmental ConsiderationsAnchor: #i1001347
Environmental Effects vs. Benefits
Much is written and said each winter about the effects of anti-icing and de-icing chemicals on the environment, but little is said of their benefits to the traveling public. The truth is that anti-icing and de-icing chemicals are essential to the safe transportation of goods and people. When applied heavily and frequently, chemicals can pollute receiving waters, but the degree of their damage largely depends on the type and designated use of the receiving water, and on the drainage system used to discharge the runoff.
Surface waters are not as vulnerable to chemicals as are ground waters because their turbulent actions blend and dilute plumes of incoming liquids almost immediately after the chemicals enter the mainstream. Ground waters, on the other hand, are more susceptible to pollution since there may be no turbulent actions to dissolve the chemicals when the runoff percolates through the soil and enters the water table.
Calcium Magnesium Acetate (CMA) and Potassium Acetate (KAc) are chemicals most benign to the environment because they contain weak biodegradable acids. Sodium Chloride (NaCl), Calcium Chloride (CaCl2), and Magnesium Chloride (MgCl2), on the other hand, leave residues of chloride ions on the highway surface that may not only contaminate surrounding ground waters, but they may also corrode motor vehicles and bridge structures.Anchor: #i1001371
Variations in Effects
The effect of chemicals on receiving waters may vary with the specific use and overall ecological health of each body of water. In some cases, water with elevated concentrations of sodium may be suitable for some uses, but undesirable for certain industrial purposes. For example, high concentrations of sodium in water for human consumption are harmful to people with certain types of heart or kidney diseases, but the major objection comes from taste preferences.
The effect of high salinity on fish life varies with the tolerance of individual species. Some fish cannot tolerate a salt level as low as 400 ppm, while others are able to live with levels higher than that of seawater (30,000 ppm.)
Salt levels in highway runoff vary with the amount of chemicals applied and the intensity of subsequent rainstorm events. Highway runoff can contain salt levels as low as 10 ppm, particularly in areas where chemicals are not used.Anchor: #i1001401
Chemicals in Highway Runoff Not a Major Source of Chloride Contamination
It is important to note that chemicals in highway runoff are not the major sources of chloride contamination of waters. Sewage discharges and runoff from industrial waste and agricultural products also contain high concentrations of chloride that may affect receiving waters as well. Rain and snow may deposit as much as 35 to 40 pounds of chloride per acre annually even without the presence of de-icing chemicals. Areas that are geographically located along coastal waters also experience high chloride concentrations since chloride occurs naturally in sea water, natural brines and water which passes through salt-bearing strata.