Overuse of road salt can be hazardous to environment, infrastructure, advocates say
New England environmental advocates are warning government officials and certain companies about the hazards of using too much salt to de-ice the roads.
Salt crystals can contaminate the waterways, corrode infrastructure, and, in some cases, be hazardous to wildlife, these advocates say.
“You can have a particularly salty patch of water come through and knock out some fish, but also over time lower levels that are not immediately lethal can impair reproduction or lifespan or other functions of life,” said Sean McCanty, the river restoration director for the Neponset River Watershed Association.
Issues with high levels of salt use are worsened as climate change affects weather patterns and increases the need for salt use.
McCanty said new weather patterns have meant heavier snows that require more salt, and more rain that can cause runoff into waterways like the Neponset.
New Hampshire has seen salt use double in the past four years, as changing weather patterns bring less snow and more mixed precipitation that leads to ice, said Steve Landry, supervisor of the watershed assistance section at the New Hampshire Department of Environmental Services.
“We’ll get dumped on with snow. It’ll melt partially the next day, and then it’ll freeze at night, so we’re getting a lot of black ice events. … It’s been a bad and worsening trend,” Landry said. “The weather patterns are dictating more ice management than mechanical removal of snow.”
Road salt is generally made, like table salt, of sodium chloride. The salt, when dissolved in rain or melted snow, lowers the temperature at which ice melts. The ice melts and stays liquid, even when the temperature drops below freezing.
When it washes into streams, the dissolved salt can impact wildlife in the water, said McCanty.
A 2022 paper published in the journal Science of the Total Environment reported that increased levels of road salt in waterways can impact populations of the ecosystems’ smallest microorganisms, which struggle to survive in water with higher salinity, to larger fish which are not adapted to handle saltier water.
Higher amounts of the road salt seep into the rivers and ponds in urban areas, which tend to have fewer permeable surfaces to absorb water, the paper said.
“These are supposed to be freshwater systems, but then they start becoming more like brackish systems when the chlorides get too high,” said Landry. His work includes oversight of a 10-year-old voluntary state program that teaches snow and ice removal companies how to safely reduce salt use.
Landry said the overuse of salt can also damage landscaping, harm trees along roadways and corrode vehicles and infrastructure.
If enough sodium chloride gets into drinking water, it can cause hypertension or issues for people with high blood pressure. The presence of salt infrastructure can also lead to higher concentrations of heavy metals in drinking water, according to the EPA.
Various efforts to reduce the quantity of harmful road salts are used. Alternative salts, like magnesium chloride and calcium chloride are considered safer for the environment but are less effective in the same quantities or more expensive, limiting their usability.
The city of Boston uses sodium chloride rock salt treated with other chemicals to prevent caking. In a recent announcement about winter preparations, the city said it has 44,000 tons of salt on-hand. The city’s highway division said it has no plans to use alternatives but is always looking for “new and innovative options that can benefit our winter storm operations.”
In New Hampshire the state has been working on decreasing the amount of salt that ends up on roads, what Landry said is the most effective way to address the issues caused by oversalting.
Since 2013, the state has been running its Green SnowPro Program, an education initiative for commercial snow and ice treatment companies focused on things like better calibrating equipment and controlling when salt is released to prevent unnecessary build up at intersections. Also among the salt reduction practices is the use of brine rather than rock salt, which is more effective at de-icing as sodium chloride doesn’t do its job until it’s dissolved, Landry said.
“When you apply it, it goes down wet; there’s no bounce and scatter of rock salt off the road surface — it seeps into the pavement and does its job,” Landry said. “If you see rock salt on the road, it’s not doing anything. Winter salt is only effective when it’s in solution.”
Landry said that programs that have gone through the Green SnowPro Program have reported savings in salt and equipment use up to 40% in a winter.
Local efforts have focused on getting a better understanding of the amount of salt that ends up in waterways.
For the past two years, the Neponset River Watershed Association, along with seven other watershed associations, including those representing the Charles River and Mystic River have been monitoring chloride levels in waterways.
McCanty said the work is helping to provide both a baseline measurement and lets them identify spikes from weather events during winter that deposit runoff into streams and waterways.
Through the group’s Neponset Stormwater Partnership, a local effort with towns and cities along the river and its streams, the watershed association has led conversations about reducing road salt use. He said municipalities were interested in decreasing use.
“Obviously, using less salt means buying less salt and putting it out, so it saves money at the municipal level,” McCanty said.
Currently, those conversations have not extended to Boston. McCanty said because the city is large enough to span three watersheds — the Charles, Mystic and Neponset — the decision-making process is more complex. There are additional challenges presented with installing sensors that track salinity in the Neponset near Boston, while making sure they are safe to access. Much of the river that borders Boston was declared a superfund site to address increased contamination in the river sediment.
