ANDERSON – As significant snowfall makes its first appearance of the season, fleets of municipal and state trucks have begun spraying thousands of tons of salt on roads and streets across Indiana to make them safer for travel.
In the United States, interstate de-icing is the largest single use for salt, consuming up to 10 times the amount needed in food production.
Salt sprayed on roadways doesn't just disappear when the snow and ice are gone – the salt is washed away, either into storm drains or through drainage ditches and ultimately into lakes and streams. Eventually, the chemical -- salt is sodium chloride and is typically treated with a non-caking element for spraying on pavement – most often reaches drinking water sources.
When it does, it has measurable effects on the environment.
"Rock salt runoff negatively affects soil, vegetation, concrete, metals and aquatic life," said Julie Savia, an environmental manager at the Indiana Department of Environmental Management.
Though no program thoroughly monitors environmental sodium chloride, Savia pointed to an ever-growing body of scientific studies of the vast amounts of salt leaking into water sources and affecting the environment.
One such study, conducted in 2010 by Indiana University researchers, tested streams and lakes near Bloomington and Ellettsville. It found sharp spikes in the salinity of bodies of water immediately after snowfall and the spraying of road salt.
Those spikes reached more than eight times the level estimated to have long-term effects on 10 percent of aquatic species. The IU study also pointed out that, once salt is introduced into the environment, it is extremely difficult and expensive to remove.
A larger study looking at 39 lakes, three rivers, 10 tributaries and several observation wells near the Twin Cities metro area in Minnesota found about 70 percent of road salt filtered into the local watershed.
"Human safety is of primary concern," Savia said, because of the importance of keeping roads safe for drivers. "But environmental effects need to be considered, as well."
Road salt that settles in soil can damage trees and vegetation as far as 650 feet away from the roadway, according to a study conducted by the Department of Environmental Conservation in New York.
Excess rock salt that accumulates near roads can also lure animals such as deer and squirrels to roads, leading to accidents that kill animals, damage vehicles and threaten people's safety.
Despite the environmental hazards of spraying roads with salt, the practice persists, simply because it's cheap and naturally abundant.
But some states and municipalities are finding ways to mitigate use of road salt.
In Muncie, road crews mix beet juice with traditional rock salt to treat icy roads. The beet juice is effective at lower temperatures and reduces salt application rates by nearly half. It also reduces corrosion of bridges, concrete and cars because beet juice is less caustic than salt, said Muncie Street Superintendent Duke Campbell.
Another option is reusing cheese brine, as many Wisconsin communities have done. The environmental effects, though yet to be thoroughly studied, are expected to be negligible; the liquid would have gone down the drain, anyway.
While mixing road salt with other substances, or replacing it altogether can be an effective solution, other basic steps can be taken to reduce the need for salt on slick roads.
Through more comprehensive maintenance of street equipment, the city of Hobart lowered its use of salt by 10 percent without reducing effectiveness on icy streets. The maintenance program saved the city 828 tons of salt, about $43,000 worth, during the winter of 2012-13, according to IDEM.