An estimated half-million tons of salt spread on Minnesota roadways each winter keeps drivers safe and our economy on the move, but also causes untold damage to lakes and streams.
While little more than a dozen bodies of water in our state have been listed as impaired by chloride, “the more you look, the more you find,” said John Hensel, metro area watershed supervisor for the state Pollution Control Agency. “A lot of waters have not been tested.”
Too much chloride disrupts aquatic life forms’ metabolism. But it’s practically everywhere there’s pavement in Minnesota. The poster child for chloride contamination in Minnesota is Shingle Creek in the northwest Twin Cities suburbs and Minneapolis, which drains a watershed crisscrossed by four major highways — 94, 694, 100 and 169, plus many county and local roads. Officially designated as impaired since 1998, the creek needs a 71 percent reduction in chloride levels to regain aquatic health.
A 2006 MPCA report said such a cleanup “may take one to 15 years.” But Hensel said few significant improvements have yet been documented in any of the state’s chloride-impaired waterways. “It’s been slow,” he said. “We’re looking for progress over 10 years at least.”
It’s nearly impossible to remove chloride from lakes once it gets in — it’s heavier than water and sinks to the bottom — so state regulators are pushing new winter road maintenance technologies that sharply cut the amounts of salt used. “Some of the most environmentally sensitive techniques are being used by governments in the metro area,” Hensel said.
He praised the Minnesota Department of Transportation’s leadership in this effort. State-of-the-art plow trucks now pre-wet icy roadways or apply salt in a liquid solution, cutting both chloride contamination and taxpayer costs.
The city of Prior Lake won a national public works award this year for its snow and ice control program, implemented beginning in 2002. Since then, it has cut average application rates by two-thirds, saving $93,000 a year. That’s a great return on the city’s investment of $300,000 in new equipment over seven years. Even better, Prior Lake waters are showing reduced chloride levels.
According to MPCA estimates, road maintenance and runoff from salt storage produce 87 percent of Shingle Creek’s chloride contamination. Most of the rest comes from residential use and commercial salt applications such as on shopping center parking lots. When it comes to cutting salt use, “The laggards tend to be private applicators,” Hensel said.
But it’s difficult to police non-point-source chloride pollution that comes from practically everywhere in an urban setting, he added. Many salt users may not even be aware of the environmental damage they can cause. They do know, however, that the price of road salt has gone up 66 percent since 2004.
If public sector early adapters can show the way to save lakes and streams and money at the same time — again, who says government can’t innovate? — private businesses shouldn’t be far behind.