Clean Water Tip - Halt the Salt: Safer Ways to Salt Your Street

After a warm start to the season, it is finally starting to look--and certainly feel--like winter in the Lake Champlain Basin. To make walking and driving safer in this icy season, state and municipal road crews salt roadways. This practice started in the 1930s, when cars became more commonplace and roads needed winter maintenance. Since then, the annual use of road salts in the US has increased—in the past 45 years, the amount has tripled—to a yearly estimated total of 25 million metric tons.

All of this salt has to go somewhere. When in contact with the water, salt dissolves into its ion building blocks, the most common of which are sodium and chloride. The now salty water first washes off roads, stoops, parking lots, and sidewalks, and it can kill adjacent vegetation quickly, as these species are rarely adapted to high salinity. Salty water then either seeps into groundwater or flows through waterways, winding up in larger reservoirs like Lake Champlain. Chloride concentrations in Lake Champlain and its tributaries have been steadily rising for the past several decades.

While road salts have the important benefit of preventing ice from forming on walkways and roadways, this substance has negative consequences for aquatic ecosystems and human health. Some fish, amphibians, and aquatic insects are sensitive to salt, and water with high chloride levels is toxic to them. Meanwhile, many mammals like salt a little too much: with salt accumulating on roadsides, deer and moose gather for a high sodium treat, resulting in greater incidents of roadkill. Road salts can infiltrate groundwater too, which impacts the quality of drinking water supplies. Not only does this make drinking water saltier, which is a concern particularly for those with heart problems, but research indicates that the ions from dissolved salt can mobilize harmful substances such as radon, mercury, and lead.

Salt also disrupts the chemical makeup of lakes. Salty water settles toward the bottom of the lake, making this water high in chloride and low in oxygen. Usually, the water column “flips” seasonally with spring turnover, but with high levels of salt “stabilizing” the bottom of the lake, this process can be prevented from occurring fully. Researchers have observed this phenomenon in Mirror Lake, in Lake Placid, New York. The result is a larger section of the lake being oxygen-poor, which is bad news for fish and other species that rely on deeper water in the summer: water is too warm above them, and not oxygenated enough below them.

A “Goldilocks” solution is necessary: there should be enough salt, or, ideally, alternative remedies, applied to prevent accidents and effectively melt ice when needed, but not so much to harm our waterways. New York passed legislation in 2020 to reduce salt use in the Adirondacks and a three-year pilot project to test alternatives got underway in the fall of 2021. LCC supported the NY legislation and is advocating for passage of a similar measure in Vermont. While the greatest impact comes from large-scale reductions, there are still ways for homeowners and apartment dwelllers to salt more mindfully if they choose to apply deicers. We recommend following the tips below excerpted from the Lake Champlain Sea Grant guidelines. Check out their cool YouTube video here!

  1. Don’t apply salt if the temperature is less than 16 degrees F– Salt depresses the freezing point of water, which makes it effective at reducing ice formation and accumulation on streets and sidewalks in the winter—down to a certain temperature. Sodium chloride, the most common type of road salt, is not effective when the pavement temperature is colder than around 16 degrees Fahrenheit (-9 Celsius). Check the temperature of the pavement with an infrared thermometer (if you have one) before you salt. If it’s too cold, opt for an alternative such as gravel, sand or even cat litter. These materials will provide extra traction to help prevent slipping and will also absorb more heat from sunlight which helps melt the snow.
  2. Don’t apply salt to concrete, gravel, or dirt driveways – Salt is even more harmful for the environment and can cause dangerous conditions for driving if you apply it to an unpaved surface. Salt is also corrosive to concrete, particularly new concrete, as water seeps into cracks, re-freezes, and triggers breakage. In those situations, try salt alternatives like gravel, sand, or cat litter to increase traction.
  3. Salt before the snow – Keep an eye on the forecast and salt before a stormTaking action in advance creates a buffer between your driveway and the snow which makes shoveling easier and driving safer!
  4. Use a salt-water solution instead of dry salt – Since any dry salt you spread must combine with water to minimize ice formation, it will work more effectively if you dissolve it in water first and then spray it on surface areas. To make a salt-water solution, combine about two and a half pounds of salt with a gallon of warm or hot water, transfer the mix to a garden sprayer, and spritz it onto surfaces before a storm hits. Using a salt-water solution rather than dry salt, further reduces the ability of snow and ice to bond with the surface and can cut the total salt use and make it easier to plow or shovel after a storm.
  5. Shovel, then salt – If you aren’t able to apply a salt solution before a snow storm, then shovel first and apply the salt as close to the pavement as possible which will reduce the amount of salt you need. If you salt before shoveling, the salt has to seep through the layer of snow before it can start working.
  6. Use the right amount – Spread no more than one or one and a half cups of rock salt for every ten sidewalk squares or two parking spaces with three inches between each of the salt grains. Using more salt doesn’t make it more effective it just wastes money and causes more salt to runoff into waterways or be tracked into homes and other buildings.
  7. Sweep up excess – If you used too much salt and see it on your driveway or walkways after the snow is gone, sweep it up and save it to use for the next storm. If you don’t take this action the salt will infiltrate nearby soils or run off your driveway and pollute a nearby waterway.
  8. Spread the word – Increase the impact of your effort to reduce salt runoff by sharing these tips with your friends, neighbors, and colleagues!