A December 10 Sustainable Cities Network article enumerated the environmental threats posed by the overuse of salt in deicing roads and potential ways public works departments can reduce its usage while still keeping roads passable and safe. From the article:
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.” …
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.
The article also discussed methods to lower road salt usage, including: (1) prohibiting the overloading of salt spreaders; (2) pre-salt wetting; (3) use of sensors which adjust salt dispersion based on road and temperature conditions; and (4) use of brine solutions; and (5) use of salt alternatives such as calcium chloride or beet juice.
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.”