Pollution by Magnesium Chloride De-icer Being Studied
The de-icing substance magnesium chloride works better than anything else the Colorado Department of Transportation has used to minimize air and water pollution. Those are the preliminary data from a three-year study by the department.
The department embarked on the study of magnesium chloride two years ago--five years after of starting use of the substance.
To date, department research has found that, although the de-icer may not be the ultimate sound solution, correctly applied, it appears to be safer than the previously used de-icing mixture of sand and salt.
Magnesium chloride is a natural salt pumped from the Great Salt Lake and concentrated in holding ponds. In a 25 to 30% concentration, the liquid prevents ice from bonding to a road.
Dr. Bill Lewis said that one aspect mitigating magnesium chloride's application is the possibility of its containing heavy metals. Lewis is a University of Colorado environmental science professor and the chief researcher on the highway department's magnesium chloride study. The trace contaminants, he believes, enter either during the process of concentrating magnesium chloride or possibly during contact with the metals in transport tankers or rail cars.
Magnesium chloride manufacturers also add anti-corrosion ingredients to counter the substance's corrosive effect. Lewis said some of those added organic compounds, particularly phosphorous, are environmentally harmful and are no longer allowed in the highway department's magnesium chloride.
Werner Hutter, project manager of the highway department's research division, said his department is writing new specifications for magnesium chloride, detailing acceptable levels of heavy metals and organic rust inhibitors.
So far, he said, the department has relied mainly on the good faith of magnesium chloride vendors to determine the product's composition.
The vendors do their own testing on batches of magnesium chloride and deliver printed results to the highway department. However, other than the research project, Hutter said, the only regular testing by the highway department is to spot check for corrosion inhibitor. The department, however, also counts on the satisfaction of other magnesium chloride users, including the states of Texas and Washington.
Magnesium chloride has been used on Colorado highways for more than seven years. Thirty-eight to 40 gallons are sprayed for every mile of single-lane highway, but because of the presence of melted ice, it is highly diluted by the time it leaves the roadway. The department reportedly sprayed roads with 4.8-million gallons during the 1997-98 season.
The previous case study was adapted from a story appearing in the December 31 edition of The Denver Post.