Salt levels in MN lakes threaten native fish

Road salt threatens freshwater lake health

MINNEAPOLIS - A comprehensive new study shows that many lakes in the Twin Cities metro area have a growing level of chlorine contamination from road salt and other ice melt products. If unchecked it could render those bodies of water lifeless within 30 years 

The study, headed by a University of Wisconsin researcher, examined 371 lakes in Canada and the Upper Midwest and found chloride levels on the rise. Those levels were especially pronounced in urban areas with more paved roads and other impervious surfaces.

The study, done by the Cary Institute of Ecosystem Studies, can be found in the Periodical of the National Academy of Sciences online.

The researchers data on chlorine concentration in Minnesota came from the Minnesota Pollution Control Agency's salt contamination monitoring program. The MPCA online site includes an interactive map tool that allows residents to check the chloride levels in Twin Cities area lakes under scientific surveillance.

Researchers found that lakes in Minneapolis and St. Paul are some of the saltiest lakes, and that is consistent with one of the study's key findings, that "impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes." 

The density of roads within and the existence of developed neighborhoods in close proximity to Twin Cities lakes would translate to more salt getting into waterways.

"Once that salt comes in contact with water the chloride side will just completely break off and go with the water.  And it stays chloride essentially forever," Brooke Asleson, the MPCA's chief advocate for reducing the use of salt, told KARE.

Asleson now works closely with the MPCA's community partners to provide Smart Salting training with school maintenance directors, private snow removal contractors and others, teaching ways to reduce rock salt use.

"We're talking about any salt that’s applied to any paved surfaces, so your driveway, your sidewalk, your parking lots, you got to gas stations, you go to the church, the library," Asleson explained.

"Through this training process we’ve been able to get people to understand that more salt is not necessarily better, that you can get the same amount of melting with a very little amount of salt."

The MInnesota Dept. of Transportation has been working to reduced road salt use for years, with an eye toward protecting aquatic life. Long range research focuses on highway designs that guard against excessive snow accumulation.

"We’re working in the present with trainings, new technologies and alternative chemicals, and we’re working in the future with research," Steve Lund, MnDOT's chief maintenance engineer told KARE.

"Minnesota drivers have high expectations and we like to meet those, and that is a dilemma because of driver expectations to be able to get around."


The Environmental Protection Agency's legal pollution standard for salt is 230 milligrams per liter, or one teaspoon per five gallons of water.

© 2017 KARE-TV


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