Madison has been salting its roads in the winter for about 60 years, and despite the concerns of some about its impact on lakes and rivers, a road salt report from Madison Dane County Public Health says people often prioritize winter driving conditions over environmental health.
“I think in the summer its something people talk about and say something needs to be done,” Rick Wenta of Madison and Dane County Public Health said. “In the winter, five minutes of extra travel time is too much of an inconvenience and nobody cares about anything but the road being clear.”
As winter approaches, Madison faces the the pressure to salt roads with the knowledge of its harmful impacts on surrounding lakes.
Wenta said road salt is most commonly applied to streets, driveways and sidewalks in the winter to slow water’s ability to form ice. However, it often dries into a powder and gets carried away by the wind to other locations. It also gets splashed onto roadside vegetation, infiltrates soil and groundwater and drains into lakes or streams, he said.
Road salt is composed of sodium chloride, which has no way of being absorbed by chemical or biological processes. Once it enters the environment, it is there to stay, Wenta said.
A study by University of Minnesota in 2009 found a strong correlation between chloride concentrations in metro area lakes and road salt purchases by the state. Because road salt often makes its way into drinking water, human health could be affected if it reached a substantial level.
“Sodium will raise blood pressure,” Wenta said. “Once it gets above about 20 milligrams per liter, people on a sodium restricted diet are supposed to be informed by the water utility that the well they get their water from is at that level.”
Only one well in the city is getting close to dangerously high sodium levels, he said.
“But if we get to that point, that may be what we need to get people to realize we have to start using less salt on the streets,” Wenta said.
But sodium isn’t the only concern; chloride is toxic to aquatic life and can have negative effects on vegetation and wildlife, the New Hampshire Department of Environmental Services said.
All of Madison’s lakes have experienced increased chloride levels over the past 50 years, but none have been impacted as much as Lake Wingra. Beginning with a chloride concentration of just below 60 milligrams per liter, this number is now up over 100. To put this in perspective, the highest chloride concentration in any of the Great Lakes is less than 25 milligrams per liter, according to the Environmental Protection Agency.
