Environment

Louisville’s Public Works Department prepares for the onset of frigid temperatures with as much 35,000 tons of salt to keep the streets free of ice and safe for drivers. But salting the roads comes at a cost, damaging local waterways and impairing marine life.

Already this year, there have been spikes of sodium levels in some of Louisville’s smaller, urban streams. United States Geological Survey monitors along the Middle Fork of Beargrass Creek and Chenoweth Run demonstrated levels several times higher than normal after recent storms.

Ward Wilson with the Kentucky Waterways Alliance said that’s likely the result of road salt dissolving and running off into the waterways.

“Right after we’ve salted the roads and it thaws or we get a rain like recently, you get a pretty big change, it will be many times what the normal levels are,” Wilson said.

The salt isn’t usually enough to cause large-scale die offs, but it does affect insect populations, particularly bugs like mayflies and stoneflies.

That, in turn, can cause problems further up the food chain, because the bugs are food for larger animals.

“It is not so much seeing them die immediately, but you go back and you look at what lives there and you find the [organisms] that need high-quality water are the ones we start losing, you see less and less of them,” Ward said.

Still, Ward said road salt is a much more significant problem in states further north, which use it more often. Salinization of the country’s fresh water streams is a growing problem across the country impacting drinking water supplies and biodiversity.

One recent study found salinization and alkalinization have affected as much as 37 to 90 percent of the drainage area across the country. In addition to road salt, the salinity can also come from sewage, decaying concrete and mining wastes.

Public Works Spokesman Harold Adams said the city is aware of the potential impacts and tries to minimize the amount of salt on the roads. A single truck typically dumps about 400 pounds of salt per lane, per mile, he said.

Some cities spray beet juice in place of the brine used to prevent roads form icing ahead of a storm, but Adams said the juice comes with its own set of problems, from odors to sugars that cause their own environmental hazards.

Unfortunately, both Ward and Adams say there aren’t a whole lot of good alternatives to salt.

“Quite frankly it’s a balancing between creating safety on the roads for pedestrians and motorists and those environmental concerns,” Adams said.

Plowing and shoveling snow remains the most environmentally friendly way to deal with the snow, Ward said.

Ryan Van Velzer is WFPL's Energy and Environment Reporter.