It’s a cold fall morning in Minnesota. As I step from my car and walk up to the building there is a palpable crunching under my feet. Looking down, I see shallow pools of water intermixed with small piles of white granules reflecting up from the pavement. It’s a familiar sight in the Midwest and my steps are more confident knowing that I am less likely to slip on ice with the salt there. However, this confidence comes at a cost.
Every year, 350,000 tons of salt is applied in the Twin Cities Metro Area alone. Salt (chloride) readily dissolves in water and moves to nearby lakes, rivers, and wetlands. Chloride is virtually a permanent pollutant: it does not break down and it accumulates over time. One tsp of salt is enough to permanently pollute 5 gallons of water. As a result, 77 lakes in the Metro Area now exceed or nearly exceed chloride standards and are being considered for impaired water listing. Higher concentrations of salt kill fish, but even low levels can harm other aquatic plants and animals such as freshwater mussels. Salt also puts drinking water at risk and damages infrastructure through corrosion.
Earlier this month, the MN Zoo hosted two “Smart Salt Workshops” for Zoo staff along with other government agencies and private snow removal companies. The program, put together by the Minnesota Pollution Control Agency, is intended to highlight the negative consequences of salt in our watersheds and help people make proactive, cost-effective, and environmentally conscious choices that still keep surfaces safe for the public.
So, how can you help at home? The big take-home message is to use less salt! For instance, snow should be shoveled and salt only applied to ice. Drop spreaders should be used so that there are no piles of salt – any salt remaining on the sidewalks indicates too much has been applied, and the excess should be swept up. Keep in mind that rock salt does not work below about 20F! Finally, as an alternative to salt, sand or grit can be used to provide traction in slippery areas.