Winter is a fact of life in Minnesota. Freezing rain and snow fall from the sky onto our driveways and sidewalks, and we remove it with a snow blower and shovel and put on rock salt to do the final melting. Once the salt has dissolved and cleared our icy pavement, we usually do not think about the salt again unless we notice in the spring that there are bare spots in the lawn next to the areas we salted.
There is a much larger issue with rock salt that is less noticeable but causing a big problem; the chloride from rock salt is polluting our lakes, rivers, and wetlands.
Increased chloride levels are a problem for a variety of reasons. First, the chloride affects habitat. High levels of chloride are toxic to the aquatic life and the salty water affects disrupts freshwater ecosystems. Second, unlike pollutants such as phosphorus and nitrogen, chloride cannot be filtered out. The chloride dissolves into the water where it becomes a permanent pollutant. The only way it can be removed is by reverse osmosis, which is not feasible at the scale of lakes and rivers. Every winter when rock salt is spread the snowmelt flows into our lakes and rivers and the chloride concentration in our waterbodies increases.
With so much salt being spread across Minnesota, it may feel like the amount of salt that one person spreads on their driveway could not have any impact, but it does. Just one teaspoon of salt is enough to pollute five gallons of water, so if you reduce your use by one cup that saves nearly 250 gallons of water from being polluted. It all adds up, and you can be part of the solution.
What else can you do?
Sprinkle, don't pour. Large salt granules melt a few inches of ice, so sidewalk salt should be scattered about 3 inches apart. Additional salt just adds unnecessary pollution.
Sweep up extra salt. If there are still salt granules on your sidewalk and driveway once the ice has melted and the sidewalk is dry, sweep up the salt! You can use it after the next storm, plus it won’t get washed into our waters.
Only put down salt when temperatures are warm enough for it to work. Pure rock salt (sodium chloride) can only melt ice if the pavement is above 15 degrees Fahrenheit. If the pavement surface is colder than that, no melting will occur and the salt will just get blown away. At colder temperatures sand can be used for traction on the ice, or you can use de-icers that work at colder temperatures.
Wear appropriate winter footwear. Don’t expect every sidewalk to be as clear and dry as it is in the summer. Put on those boots and be tolerant of safe amounts of snow on the sidewalk.
Drive with care. Leave yourself extra time to get to your destination in the winter, don’t drive when you don’t have to, and consider putting snow tires on your vehicle for the winter for better traction.
We all want to be safe this winter, but let’s also consider our water and use only as much salt as we need and not a granule more.