For over a decade, Madisonians have glimpsed white stripes running down the main roads and pathways around the UW campus and the greater City of Madison during the winter months. But where do these markings come from, and what do they mean?
It turns out that the white stripes are a result of the salt brining process, where a mixture of salt and water are applied to the pavement before a major snowfall to prevent the snow from freezing. Applying brine allows the plows to easily push the snow off the roads, and it also reduces the amount of rock salt that road and sidewalk crews have to spread later on. Salt works by lowering the freezing point of water to reduce icy conditions, but it also degrades water quality of surrounding watersheds when it mixes with snowmelt and flows into lakes and streams. Finding ways of keeping roads safe while also preserving the environment is thus a high priority.
The City of Madison services the city streets near UW-Madison such as University, Lake, and Langdon, while salt brining on campus is serviced by the Physical Plant.
According to Bryan Johnson, public information officer of the City of Madison Streets Division, the City uses salt brine in two ways. First, when conditions are favorable prior to a snow event, the Streets Division deploys a five-ton truck along a predetermined route to spray main roads and pathways with brine. This process prevents the snow from binding to the pavement as it falls.
Brine is also used to improve the efficacy of rock salt. Trucks with rock salt spreaders are equipped with saddle tanks that hold brine, which is sprayed as the rock salt is spread in order to keep the salt in the travel lane. Without applying some kind of liquid to the salt, it would simply bounce off the road and wind up in the gutter. Combining brine and rock salt means that less salt is required overall.
“The city has been using brine in the saddle tanks for quite a few years now—since the early 2000s—and as a pre-treating option [it] has been a practice since 2009,” says Johnson. “We’d like to brine and pre-treat more than what we have the ability to do now, and once we can secure the necessary equipment, we will do it.”
Johnson says that the Streets Division wants to use as little salt as possible, while also keeping the roads up to the expectations and needs of the community we serve.
By: Trina La Susa