When it comes to the materials used to keep our roads de-iced in the winter, there isn't a crystal clear choice on what's used.
The products vary from agency to agency. And there are pros and cons of each, considering effects to the environment, vehicles and infrastructure, cost and effectiveness during different temperatures.
John Perfect of the Idaho Transportation Department, which tends to Interstate 90 and U.S. 95, said his agency is using far less sanding gravel these days and more wet salt that has not been run through a kiln.
"One of the big problems with the gravel is that it collected in streams along highways and choked the spawning areas for fish," Perfect said. "Because we haven't used as much in the last few years, those streams have had more of an opportunity to recover."
Perfect said there are also fewer tort claims due to broken windshields since the state has cut back on sanding gravel.
ITD also uses a kiln-dried salt before storms and for black ice, but it's used less frequently than wet salt partially because of the price difference. Dry salt runs $124 a ton compared to $110 for wet salt.
Pocatello gets its wet salt for $55 a ton because of its closer proximity to Salt Lake City.
"The haul up here is a big part of the cost," Perfect said.
Perfect said the salts haven't been harsh on the environment because the state's application rates are lower than other regions. Perfect said ITD uses 100 to 125 pounds per lane mile, whereas some other areas use between 500 and 1,200 pounds.
He said a recent state study on streams on Fourth of July Pass weren't at critical points from salt usage.
"But long-term problems are something we need to look into," Perfect said. "Even though we haven't seen buildups in the soil from the salt, salt can break down the chemistry of the soil, particularly in clay, which we do have."
Perfect said the state doesn't use inhibitors, or sugar byproducts, in its salt products because sugars have high phosphate levels that hurt lake habitat and they're expensive.
"A lot of the recent research on inhibitors as to their effectiveness is inconclusive," he said.
Perfect said inhibitors have been marketed well to inhibit corrosion but there are just too many questions about them. He said five out of nine states in the West no longer use inhibitors.
Coeur d'Alene uses two products to manage ice - a washed sand that is easy to pick up in the spring and salt brine with a sugarbeet by-product as an enhancer/inhibitor, said Tim Martin, street superintendent.
The liquid brine is used on major arterials when road temperatures are consistently above 17 degrees. The sand is used on compact snow and ice in residential areas, sharp corners and hills, Martin said.
The sugar beet by-product, an organic material, is higher in phosphate than other de-icers.
"We carefully monitor our output of the material and sample our outfalls to ensure best management practices," Martin said.
The cities of Post Falls and Rathdrum, along with the Post Falls Highway District, use magnesium chloride and sand during colder temperatures and on compact snow/ice and when the de-icer is slow to melt.
Kelly Brownsberger, the highway district's supervisor, said magnesium chloride is environmentally friendly, results in less corrosion than salt on vehicles and infrastructure and works at a lower temperature than salt (0 degrees compared to 15).
"It stays on the road and, most importantly, it works," Brownsberger said of magnesium chloride.
Magnesium chloride is non-toxic, said Kevin Jump, Rathdrum's public works director.
"We have neither observed vegetative adversity nor harm to animals (using the product)," Jump said. "Despite its higher material cost, the city has considerable labor and equipment savings because magnesium chloride is applied at a lower application rate and applications are less frequent than sodium chloride."
A disadvantage of magnesium chloride is that it's rough on copper and aluminum, of which many of the more expensive auto parts are made.
That's why it's important to regularly wash your car during the winter, street officials and car wash operators say.
"One of the reasons why we stay open in the winter is there are a lot of people who do understand that your car is your second-largest investment to your house," said Jared Olbricht, manager of Hippo Car Wash in Coeur d'Alene.
Perfect said there isn't a perfect solution when it comes to corrosion issues.
"Each product can create different problems to different metals," he said.
Olbricht said it's difficult to remove some road de-ice materials without high-powered equipment.
"With what those materials can do to the roads, I can only imagine what they'll do to a clear coat (on a vehicle)," he said. "Whatever is put on the roads, you don't want on your vehicle for very long."
Olbricht said Hippo uses a separating system that prevents much of the materials from entering the stormwater system and environment.
Most local highway departments said they have used about half of their de-icing budgets for the winter.
Idaho Transportation Department trucks tag team Lookout Pass after a storm.