All of a sudden, sap season is here and winter’s on its way out. Chances are though, a few more snow or ice squalls are still to come. The next time you find yourself driving behind a big plow truck, take a look at what’s coming out of the spreader. What is used makes a difference for wildlife, especially as the snow melts.
Since the 1940s, rock salt, and lots of it, has been a boon to Northeast drivers. As a tool, it is simple and effective. The crystals are dropped evenly along the road, mixing into the slush over time by the weight of passing vehicles. The slush melts away because the combination of salt and water freezes at a lower temperature than water does alone.
However, the traditional approach of spreading dry rock salt is remarkably wasteful. Studies show that 30 to 40 percent of dry rock salt spread bounces and scatters off the road into the grass or nearby woods. This is bad for transportation budgets, and it’s also harmful to the environment. Most immediately, it’s a hazard for birds, that will die if they ingest too much of it, and to other wildlife which it attracts to busy roads.
As the salt dissolves into meltwater, and breaks down into sodium and chloride ions, it causes other problems. In high concentrations, the chloride can brown leaves and needles, sometimes killing trees and shrubs near the roadways. It can also end up deep in the ground, sometimes ruining the taste of well water. But its largest effects are not ones you can immediately see or taste. When the salt reaches our lakes and rivers, it changes the water chemistry.
The concentration of chloride ions in waterways has gone up steadily over the past seven decades in northern states where rock salt is used. Scientists now regularly find readings between three and ten times what they were in the early twentieth century. Amounts much higher than that, by a factor of 100 or 1,000, have been found in small ponds and streams downstream from large highways and parking lots. At these higher levels, chloride can kill aquatic insects and even fish.
In response to these concerns, as well as the rising cost of rock salt (around $60 a ton to around $80 over just the past two years), state transportation agencies in the Northeast have been increasingly using a salt brine slurry. Wetting the rock salt with brine eliminates salt clumps and makes the salt stick immediately to the road. That increases melting efficiency and reduces the amount of salt needed to clear our roads.
To read more about salt use on Adirondack roads and its environmental impacts, click here.
Kristen Fountain is a freelance writer living in Vermont’s Northeast Kingdom. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation: firstname.lastname@example.org