When icy weather descends, snow isn’t the only white stuff that appears on local roads.
Virginia officials coat roadways with rock salt, or sodium chloride, to prevent people from sliding off slick sheets of ice.
Salting streets is a relatively cheap and easy way to melt ice by lowering its freezing point. The U.S. uses between 10 to 25 million tons of salt each year.
But once the storm clears, salt often ends up where it shouldn’t be, creeping into rivers, groundwater and drinking water systems.
“This is becoming one of the fastest growing sources of freshwater pollution in the country,” said Joe Wood, senior scientist with the nonprofit Chesapeake Bay Foundation. “It's really an existential threat to our water resources.”
Salt pollutes waterways by overwhelming and often killing plants and marine life that are not adapted to it.
The bay foundation often focuses on pollution from nutrients, such as nitrogen and phosphorus, which run into the water from storm drains, farms and sewage facilities. Trees and plants are buffers to help manage such pollution, but most cannot filter salt in large quantities, Wood said.
The General Assembly is considering legislation to investigate options for safely treating roads.
A bill from Sen. Danica Roem, D-Manassas, would direct the Virginia Department of Transportation to study the pros and cons of salting methods and alternatives.
Many options have been proposed around the country, such as calcium or magnesium chloride and mixtures including sand, cat litter and even beet juice.
But they all have tradeoffs, Wood said.
“It’s not a problem with an easy solution. And obviously keeping drivers safe on the road is really important,” he said. “So if we can make progress on finding an alternative, that would be huge.”
In the meantime, the focus is on minimizing the amount of salt used, Wood said.
A 2021 study found the use of de-icing salt tripled over the past half-century. But more salt doesn’t always work better, he said.
For residents, the rule of thumb is a coffee cup’s worth of salt is enough to cover the average driveway. Plus, people could sweep up leftover salt after the storm to reuse.
Virginia previously developed a salt management strategy with a voluntary “toolkit” to help local leaders weigh best practices.
“Salt used to melt snow and ice can help provide safe passage for pedestrians, cyclists and drivers,” the workgroup states in the report. “However, salt use can harm water quality (especially our drinking water), impact plants and animals, and damage infrastructure and vehicles.”
Some estimates document an increase in roadway maintenance of more than $600 per ton of salt applied and damage to vehicles of $113 per ton, according to the report.
The salt takes a while to work through the ecosystem, Wood said.
“Even though you only apply it in the winter for a couple days, it can have effects year-round.”
