The overall conclusion of the study is that application of magnesium chloride deicer having a chemical composition and application rate similar to those of 1997-98 is highly unlikely to cause or contribute to environmental damage at distances greater than 20 yards from the roadway. Even very close to the roadway, the potential of magnesium chloride deicer to cause environmental damage is probably much smaller than that of other factors related to road use and maintenance, including pollution of highway surfaces by vehicles and use of salt and sand mixtures to promote traction in winter. Magnesium chloride deicer may offer net environmental benefits if its use leads to a reduction in the quantity of salt and sand applied to roadways. The environmental safety of magnesium chloride deicer depends, however, on low concentrations of contaminants and avoidance of rust inhibitors containing phosphorus. Appropriate specifications for vendors and routine testing can insure the continued environmental acceptability of magnesium chloride deicers. Deicers provided by vendors should be monitored independently by CDOT for chemical characteristics. Any significant changes in processing or source material should be disclosed by the vendor. Colorado-based specifications should be developed for vendors. Independent specifications for low elevation could be developed, or the more stringent high elevation specifications can be applied to all purchases.
