Researchers Call for Road Salt Reductions

Sodium Chloride Seeps into Water Supplies Over Time

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Victoria Kelly is environmental monitoring program manager at the Cary Institute of Ecosystem Studies in Millbrook, N.Y.

Dr. Stuart E.G. Findlay is an aquatic ecologist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y.

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Posted: Wednesday, December 10, 2014 3:29 pm

As winter weather sets in across much of North America, the annual debate over road salt ensues.

On the one hand, salt and other deicers save lives and money by reducing accidents and allowing commercial traffic and air travel to continue flowing throughout the season. On the other hand, the sodium chloride that gives salt its ice melting punch can be corrosive to vehicles, roads and bridges. When the spring melt carries it into nearby streams, it can be a hazard to plants and aquatic animals.

And, if it finds its way into the groundwater system it can even contaminate drinking water and pose a risk to human health, said Victoria Kelly, environmental monitoring program manager at the Cary Institute of Ecosystem Studies in Millbrook, N.Y.

“There is a growing body of research that shows salt use is degrading freshwater resources,” Kelly said in an interview released today by the Institute. “In Dutchess County (N.Y.), it’s not uncommon for private wells to have sodium concentrations that exceed government health standards. This is especially alarming for people with sodium restrictions.”

In the state of New York alone, a half a million tons of salt is applied to roadways in a typical winter, and according to the Virginia-based Salt Institute, transportation agencies across the country applied about 17 million tons of salt to U.S. roads in 2013.

Cary Institute freshwater ecologist Dr. Stuart Findlay said the use of rock salt on roads has had a cumulative effect on the environment. “Road salt is not simply transported from roadways, to streams, to the ocean. Our long-term studies indicate it is retained in watersheds, where it accumulates. In some rivers and streams, peak salt levels have risen well above the federal level set to protect fish and amphibians (230 mg Cl/L). Even lower levels of exposure have negative effects on sensitive plants and animals if exposure times are long,” Findley said.

Salt, which lowers the freezing point of water, has been used as a road deicer since the 1940s. Its use gradually increased as more roads were built and faster highway speeds became the norm.

“Deicing salt is simply unrefined table salt,” Kelly explained. “We mine it from underground salt deposits, which were formed by ancient oceans, using drilling and blasting. The U.S. is one of the world's leading road salt producers, with New York alone mining more than 4 million tons a year.”

As a result, rock salt is relatively cheap and plentiful. But, is there a better way?

“Anyone who has ever been stuck behind a salt truck knows that spreaders can be inefficient. Older equipment applies salt at a steady rate, regardless of vehicle speed or road conditions. Because salt bounces, a lot ends up on the roadside, where it does little to help drivers,” Kelly said.

“Management practices can reduce salt overuse. Some are as simple as calibrating equipment, not overfilling trucks, and pre-wetting salt. There are also temperature sensors and application regulators that fine-tune the amount of salt applied. When the Town of East Fishkill, N.Y. retrofitted their trucks with this technology, they experienced real savings in their salt budget,” she said.

Findlay said spraying a brine solution is another way to use less salt. “Compared to rock salt, brine uses 60 to 70 percent less sodium chloride overall, and it doesn’t bounce. Applying it before a snow event prevents the ice-pavement bond from forming, making it easier to remove snow later on. Because brine is a liquid, it does require different spreading equipment, so there is an initial capital expense,” he said.

Alternatives do exist, but some like calcium chloride are 5 to 6 times more expensive than salt, so they’re only economically feasible in especially vulnerable areas near reservoirs and municipal water supplies, Kelly said. The push to find an inexpensive and environmentally friendly alternative to salt has some people thinking outside the box.

“From beet juice in Michigan to cheese brine in Wisconsin, novel deicers have gotten a lot of attention lately,” Findlay said. “One thing is clear – we really need to exercise best-management practices when applying salt, and invest in research on salt alternatives. It can take decades for road salt to flush out of a watershed, so the increased salt concentrations we see today will be with us even after its use has stopped.”

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