Salty, but Safe: Keeping roads passable through winter

Lauren Fisher

Now that we’re climbing out of the throes of winter and the roads are clearing up, we can reflect on surviving another several months of icy highways, thanks in great part to county highway departments. In Eau Claire, we can also thank 53,000 gallons of salt brine, more than 1,300 tons of salt, and 1,000 gallons of beet juice – yes, beet juice.

When salt dissolves into water, the molecules that make up the salt interfere with the water molecules’ ability to bond with one another in a rigid state. This decreases the temperature at which the water will freeze, in a process called “freezing point depression.”  The same effect can be achieved using a number of other chemicals; the Eau Claire Highway Department uses mainly calcium chloride and salt to combat slick lanes.

Depending on the conditions of a storm, Chippewa Valley road crews employ several methods to keep roads clear. Anti-icing takes place before and during the early stages of a storm.  Trucks spray a liquid calcium chloride or salt brine solution on the roads before it rains or snows, which provides a protective layer that prevents ice and frost from bonding to pavement. 

Pre-wetting is when road crews add liquid agents to salt and sand in order to help decrease the freezing point and ensure the materials stick to the road instead of getting blown off by wind and traffic. Finally, de-icing is the process of removing ice and snow from pavement by melting or plowing it.

But there’s a dark side to the use of salt and calcium chloride: Midwestern drivers often find their vehicles paled by a coat of the solutions, which are corrosive. Rust eats away at cars if motorists neglect frequent washes. The highway department itself must take extra care to ensure that road crew trucks are cleaned thoroughly and regularly, or the damage quickly erodes equipment, according to Eau Claire County Highway Commissioner Jon Johnson.

Chemicals used in road maintenance also wash away into water systems, increasing the salt and calcium chloride levels in local water sources. A study in the Proceedings of the National Academy of Sciences published in 2017 predicted that in the next 50 years, chloride exposure will pose a significant risk to aquatic life in North American temperate lakes.

“It’s really hard as someone who wants to protect the environment, but who also wants people to get home safe,” Johnson said. This year, the county highway department used beet juice in addition to traditional methods on a trial basis. Many highway departments are exploring the use of alternative ice preventatives, including, in an especially Midwestern twist, beer and cheese byproducts.

“The challenge is that calcium chloride is the best chemical we can use,” Johnson said. The department will weigh the cost and effectiveness of beet juice against that of calcium chloride to determine if incorporating it into regular operations will decrease environmental impact while still providing safe driving conditions.

In the meantime, Chippewa Vallians can rinse off their rides and enjoy a few months of easy driving before the snow comes for us again.