Road salt levels spike, threaten area lakes

Published 10:09 pm Tuesday, April 11, 2017

MINNEAPOLIS — A new study shows that many lakes in the Twin Cities are so contaminated with road salt that they’ll no longer support native fish and plants within three decades.

The study, published in the Proceedings of the National Academies of Science on Monday, looked at freshwater contamination across the country’s northern region, an area with one of the highest lake densities on earth.

Researchers analyzed the salt histories of more than 370 lakes in 10 northern states and Ontario, Canada. More than 60 of them were in the Twin Cities metro area.

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“One of the most impacted areas is Minneapolis and St. Paul, where you have dozens of small lakes,” said Hilary Dugan, the lead researcher and a limnologist at the University of Wisconsin in Madison. “The smaller the lake, the more easily you load it with salt.”

Dugan said private businesses and homeowners are to blame for about half the salt used each winter.

“When you put down salt on the sidewalk you should be thinking of teaspoons — not cups,” she said. “All you need is a few crystals to work effectively on ice.”

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

Many local governments are succeeding in reducing salt use due in part to the Minnesota Pollution Control Agency’s program to educate people on how to use less salt without compromising safety.

According to the state agency, groundwater in the metro area is also affected, with nearly a third of monitoring wells showing enough salt to affect aquatic life, and almost as many with enough salt to affect the taste of drinking water.