LA CROSSE, Wisconsin (WXOW) – Salt is a key component to safe winter travel in northern climates. But across the country, the build up of road salt has been linked to the degradation of natural areas and contaminated drinking water.
"People originally thought, well you put the salt on," said Roger Haro, biology professor at UW-La Crosse. "You know, it melts. Okay. It goes into the water and into storm sewers and stuff like that near the roads and then it's basically gone and dissipates."
This is not the case. After salt enters the environment, it can build up leading to chronic, low-level exposure to plants and animals.
"We're finding now that there's fairly long term lags with this and even after snow melts that there's a persistence of the salt in shallow soil next to roads," said Haro. "So that every time is rains a little bit more salt is liberated and moves. And so instead of just having this pulse of salt go into our creeks and our waterways, you have this long term problem build up over time."
Haro said that low level concentrations of salt can be enough to damage certain algae that are important food sources to insects that are food to native fish. And in high enough concentrations it can have fatal effects on fish, frogs, and other wildlife.
"You get some pretty high levels of these [salt] compounds into the waterways and it can have effects on fish and bugs and wildlife," said David Pericak, DNR Aquatic Habitat Coordinator in La Crosse. "And what's even more important, it can also get into our groundwater… Chloride, which is part of the salts that are applied, the chloride levels are gradually increasing statewide in many of our water supplies."
And as the need for salted winter roads grows so will the strain deicing agents place on the environment.
"This is an increasing problem all the time," said Haro. "As our road construction goes up, and our population goes up, and we need more transport grid, and we're living in a northern tier state. We need to apply salt more and more. And so more and more exposure is going on in the environment."
With an economy heavily reliant on the health of area waterways and wildlife, the strain on the environment is something that has not been lost with La Crosse County Highway Department.
"We care about the environmental impacts," said Ron Chamberlain, Highway Commissioner for the La Crosse County Highway Department. "We'd like to minimize it where and whenever we can. To that end, we're careful about when we use it, we're careful about how we use it. We keep track of the amount we are using on a given plow section. And we've been exploring alternatives to the use of sodium chloride."
Salt is also expensive.
"Aside from being the impact on the environment that salt can be, the other issue is it's and expensive product to use," said Chamberlain. "So for both reasons we want to minimize our use as much as possible, while still giving the traveling public good safe roads."
Luckily, a ton of salt isn't necessary to keep roads safe if you apply it correctly.
"Perception," said Chamberlain. "And I think this is a human fallacy, ‘if some is good, more is better.' On that basis, I would say we probably use less [salt] than people think we use. And we do it in a manner that is conducive to leaving as minimal amount residual as we can get away with."
In La Crosse County, the majority of snow is removed mechanically, without the use of salt. When salt is used, it's applied at the end of the clean up process so it is not just plowed away.
The Highway Department also diligently monitors roadway needs and weather conditions. In many instances salt isn't the best product for the job.
"The first thing to consider is the type of traffic on the road. Salt doesn't work as well on low volume roads. For sodium chloride to work it really needs traffic. It needs to be ground in to work right. So real low volume roads, straight salt isn't going to work real well. The next thing that goes into consideration is the temperature on a given day. Salt doesn't work below twenty degrees real well."
Overall salt use can also be limited by pre-treating roads with a diluted salt solution called salt brine.
"The one that we've actually implemented the most is use of a salt brine solution. The public and everybody has seen us out on a road prior to storms, during the course of the week, spraying what looks like water on the roads. That is water. It's salt brine"
Salt brine helps prevent snow from bonding to the pavement making it easier to remove mechanically. It can also be used to treat roads for frost and light precipitation events.
At home, Chamberlain said mechanical removal of snow is usually the best bet, and salt should be reserved to remaining treat slick spots. More salt is not synonymous to better results.
"I think it's more of," said Chamberlain. "‘If a little bit works and does what needs to be done, then a lot is going to work quicker.' And that's just a common perception with some folks."
"I think we all kind of fall into that trap with a lot of things. You know, ‘more is better all the time,'" said Haro. "Be strategic. Look at what problems are on your own walkways. Go with the directions on the deicing product that you're using and that will help."
The La Crosse County Highway Department is currently exploring other deicing agents and ways to reduce salt use.
Additional information on the impact of salt in the environment can be found in the articles "A Fresh Look at Road Salt: Aquatic Toxicity and Water Quality Impacts on Local, Regional, and National Scales" by Corsi et. al., and "Emerging indirect and long-term road salt effects on ecosystems" by Findlay and Kelly.
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