The Twin Cities Metro applies 350,000 tons of road salt every year, but have you ever wondered where it goes when winter ends?
Stormwater and snowmelt carry dissolved road salt into lakes, streams, and groundwater when winter thaws out. Chloride, a major part of road salt compounds, is especially stubborn in water. Once it dissolves, there is no feasible method to remove chloride from water, and stormwater treatment solutions like stormwater ponds and rain gardens are ineffective at removing chloride. Instead, chloride gradually accumulates in our water bodies, harming fish and other aquatic life. The corrosive nature of road salt also contributes between $350 million and $1.2 billion in infrastructure costs each year to the Metro area alone.
What can we do about it?
Here are some helpful tips you can use to make your driveways and sidewalks safer and better for the environment this winter:
Salt is never a substitute for shoveling. Shovel your snow and ice first so that salt is only used for melting ice stuck to the ground.
Traditional salt (sodium chloride) does not melt ice when the temperature is below 15 degrees Fahrenheit. Use a low-temperature alternative such as magnesium chloride or calcium chloride to melt ice at lower temperatures or use sand to add traction. There is no such thing as an "environmentally friendly" salt, so it's best to stick to salt that will work in the given range of temperatures.
Did you know you only need a 12-oz. mug of salt to effectively de-ice a 20-foot driveway or 10 sidewalk squares? When applying salt, aim to leave 2" between grains.
Sweeping up leftover salt and reusing it later is a great way to save money and limit the amount of salt getting into nearby waterways.
Do you hire a contractor to maintain a sidewalk, driveway, or parking lot? Check out the MPCA's list of Smart Salting certificate holders to find a contractor trained on best practices for winter maintenance: https://www.pca.state.mn.us/sites/default/files/p-tr1-01.xlsx