February 07, 2023
Though central Pennsylvania has yet to feel the full force of a northeastern winter this season, traditionally the Pennsylvania Department of Transportation annually applies millions of gallons of salt-based brine and many tons of rock salt to the state’s roadways. But what effect do these road treatments have on the state’s waterways?
Matt Wilson, director of Susquehanna University’s Freshwater Research Institute at the Center for Environmental Education and Research, said the increase of salinity in the state’s waterways has been dramatic and concerning.
“Our road salt application has continually increased each year while the average snow accumulation has not,” Wilson said.
PennDOT uses rock salt, made of sodium chloride (the same compound found in table salt), as a de-icer and crushed limestone or sandstone as an anti-skid or abrasive material. The most immediate and significant impact of these treatments tends to be when a snowstorm is followed by rapid runoff — either through rain or melt.
It’s not a winning combination for aquatic life, Wilson said.
“The critters that live in freshwater streams are just like us,” said Wilson. “They are much healthier and happier when they drink fresh water instead of salt water.”
As salinity increases in streams, the tolerance of aquatic species varies. Typically, more sensitive species — macroinvertebrates like crayfish and mussels — are affected first, while more tolerant species — bass or bluegills — persist, leading to decreased biodiversity in aquatic systems.
“The developmental stages of fish can also be adversely affected,” Wilson said. “You can see increased mortality and decreased growth rates.”
Unfortunately, as Wilson noted, as salt use on roads increases, higher salinity levels are not just isolated to the winter.
“Increased salt applications over time have led to buildup in ecosystems so that we even see increased salinity of streams in the summer now,” he said. “This isn’t just a winter problem – it’s becoming a year-round problem that adds additional stress on top of other impacts from land use and climate change that we have thrown at our streams.”
Some states have started taking steps to reduce salt usage, Wilson said.
“Some states have started using porous pavement, which not only decreases ice formation, it actually creates a 77% decrease in the need for salt application,” he said, adding that there are other solutions that don’t require a change in infrastructure.
“Another option is including biodegradable additives to the salt that increase traction and decrease the melting point of ice, making the salt more effective,” he said. “Some options that have proven effective include adding beet juice or molasses.”
Wilson also suggested the public simply stay off the roads during a snowstorm.