LANSING, Mich. — Every winter, crews sprinkle millions of tons of salt on roadways throughout the U.S.
All that salt never really goes away.
It washes into streams and rivers, causing spikes in salinity that can harm some aquatic life. Salt also can corrode steel and concrete, leading to deterioration of roads, bridges and cars.
Local officials acknowledge the drawbacks of road salt, but say they've struggled to find a substitute that's as cheap or effective.
What are the alternatives?
Road salt works because sodium chloride lowers the freezing point of water.
Alternatives to traditional road salt, including cheese brine and a beet juice byproduct, have made headlines in recent years, but salt is by far the most popular road de-icer across the United States.
The city of Lansing tried using beet juice during the winter of 2016-17, but found the substance cost too much and "was not as effective as we hoped," city spokeswoman Valerie Marchand said.
The Michigan Department of Transportation likewise has experimented with beet byproduct, but found the material wasn't cheap enough to come in at a low bid for state contracts, said Mark Geib, a Transportation Systems Management Operations administrator for MDOT.
"If anything is found by another state that works better than salt, we'll steal that idea in a heartbeat, just like they'd steal it from us," Geib said.
Typically, some salt is mixed into alternative road de-icers, including beet waste.
"There's still some environmental drawbacks to even the more environmentally-friendly products," Geib said.
Salt is in plentiful supply, which is crucial because the demand for road salt is vast, he noted.
Last fiscal year, MDOT spent about $25 million on roughly 500,000 tons of road salt.
What does road salt do to rivers and lakes?
Road salt inflicts the most damage on bodies of water near heavily-trafficked highways. Too much salt can change the way water circulates, leading to oxygen-deprived "dead zones" at the bottom of lakes.
Changes in salinity are the most dramatic during the springtime, when the first snow melt washes built-up road salt into nearby rivers and streams. A 2015 study from Michigan State University found chloride levels in the Red Cedar River spiked to between 200 and 400 parts per million as a result of snow melt, compared to average level of 75 ppm throughout the year.
That temporary chloride spike can be almost entirely attributed to road salt, said David Long, who helped lead the study.
"There's no major natural source of chloride in the Red Cedar, so you know most of that can be attributed to us, to human activity," said Long, a professor of aqueous and environmental geochemistry.
Lansing crews take special care when salting near rivers and streams, Marchand, a city spokeswoman, said. Workers also make sure snow isn't piled near waterways during the spring, she said.
The city of Lansing spent $257,460 on 6,900 tons of road salt last fiscal year.
A truck is parked outside the Ingham County Road Commission's salt storage barn in Lansing on Thursday, Dec. 20, 2018. (Photo: Roxanne J. Frith/For the Lansing State Journal)
What about drinking water?
Ingham County gets its drinking water from groundwater, according to the Ingham County Health Department. Road salt has been found to affect the chemistry of groundwater, but that doesn't mean there's reason to panic, Long said.
A 2017 test from the Lansing Board of Water & Light found chloride levels in local drinking water averaged 60 parts per million.
The U.S. Environmental Protection Agency does not take enforcement action against water systems over chloride levels, although the federal agency recommends that chloride stays below 250 ppm, the level at which water starts to taste salty.
Saltier water can be a problem for people with certain health conditions, like high blood pressure.
Does road salt hurt animals?
Road salt runoff first hurts the smallest members of aquatic ecosystems, such as the bugs that live in rivers. Those effects can eventually travel up the food chain.
Although it noted pockets of damage, a 1993 study for the Michigan Department of Transportation concluded, "Current deicing use in Michigan has not resulted in any documented widespread adverse effects on the state’s natural environment."
The study found salt to be the best substance for de-icing roads, based on cost and performance.
Still, the study noted the salt can be particularly harmful to threatened and endangered animals and to salt-sensitive plants, like sugar maples, that are within 50 feet of roadways.
And certain animals, like elk, may be more likely to end up as roadkill when they seek out salty roads instead of naturally-occurring salt licks.
"How does one attach a monetary cost to the death of invertebrates in a small stream, and how does it compare to the cost of the death of a tree beside a highway?" the researchers wrote.
Road salt is piled up an Ingham County Road Commission storage facility at Aurelius Road in Lansing on Thursday, Dec. 20, 2018. (Photo: Roxanne J. Frith/For the Lansing State Journal)
How can we use less salt?
Local and state officials acknowledge salt's environmental footprint, and say they try to use as little of the substance as possible.
No one likes being stuck behind a plodding salt truck, but officials have learned to drive the trucks more slowly to reduce waste. If the trucks drive too fast, between 25% and 30% of the salt will bounce off the roadways, Geib said.
In the past, trucks tended to dump larger amounts of salt when vehicles slowed down near intersections — that's why drivers would see piles of salt near stoplights. Now, higher-tech salt trucks are able to avoid such waste by automatically adjusting how much salt they dump based on vehicle speed and other factors, said East Lansing Infrastructure Administrator Ron Lacasse.
Crews coat roads with brine (salty liquid) before major snow storms. That "pre-wetting" process prevents snow and ice from sticking to pavement, allowing a smaller amount of salt to work more effectively.
Local agencies do supplement salt with other de-icers.
The Ingham County Road Commission, for instance, uses sand to create friction on rural roads. That's because salt trucks don't visit those lightly-trafficked areas as often, said Bill Conklin, manager of the county's road department.
Last winter, Ingham County spent roughly $671,417 on 17,000 tons of road salt.
Although it primarily uses road salt, East Lansing also uses a product called Beet Heet (a mixture of salt, magnesium chloride and sugar beet molasses) on sidewalks in its downtown.
East Lansing spent about $102,000 on 2,800 tons of road salt last fiscal year.
“(Salt is) not really friendly to anything at all other than making roads safe for humans.”
Mark Geib, Michigan Department of Transportation administrator
Is salt bad for cars, roads and bridges?
Salt chews up concrete roads and corrodes steel bridges.
Over time, salt can rust the undercarriages of older cars and eat away at paint, creating a pockmarked appearance.
"It's not really friendly to anything at all other than making roads safe for humans," Geib, an MDOT administrator, said of salt's corrosiveness.
Nonetheless, Long, a chemist who served on environmental panels convened by Michigan governors John Engler and James Blanchard, said he once asked an MDOT engineer whether people complained to the state about salt damaging their cars.
"His response was interesting," Long said. "They got a few calls about rusting cars, but mostly people were calling to ask when the salt trucks will be coming out."
Contact Sarah Lehr at (517) 377-1056 or slehr@lsj.com. Follow her on Twitter @SarahGLehr.
