Item B - Ice and Snow Policy - Laserfiche WebLink

Home Browse Search

ii from the roadway, but dilution will vary considerably in relation to rate of application, amount of runoff, and other site-specific factors. 5. Analysis of the deicing mixtures that were in use by CDOT during the winter of 1996- 97 showed unexpectedly high concentrations of lead, zinc, and cadmium as well as phosphorus. Ratios of lead, zinc, and cadmium to stream standards exceeded the desired threshold of 500. CDOT tightened its restrictions on vendors for supplies purchased for the winter of 1997-98. 6. Deicers provided by vendors for winter 1997-98 showed lower concentrations of metals and phosphorus than deicer provided by the same vendors during the previous winter. Ratios of contaminants to maximum allowable chronic concentrations in stream water were all below 500, as necessary to assure appropriate dilution prior to entering the environment. 7. Organic materials are expected components of deicers because rust inhibitors may consist of organic compounds. An analysis of the deicing solutions in use during 1996-97 showed that the deicers contained between 280 and 850 mg/L of organic carbon, and that this amount of organic matter would be expected to induce a total oxygen demand between 750 and 2200 mg of oxygen for every liter of deicer applied to the roadway. Deicer supplied for winter 1997-98 contained between 1200 and 2800 mg/L of organic carbon, and would have had oxygen demand higher than that of the previous year (3150-7500 mg for every liter of deicer). Given the extensive dilution of the deicer on and very near the roadway prior to entering the environment, however, this potential oxygen demand appears to present no environmental threat through the depletion of oxygen in streams or other aquatic environments. 8. The biochemical oxygen demand of deicers was measured experimentally. Control sites (i.e., sites not receiving deicers) showed biochemical oxygen demand between 0.04 and 0.11 mg O2/L/day. No significant increase in BOD could be detected as a result of the addition of