Lakes are damaged by road salt

Snow and ice are part of Minnesota winters; lakes are part of Minnesota summers. It’s becoming increasingly clear that these Minnesota staples are intricately linked – the future of one is dependent upon the way we deal with the other.  

When it snows, or even when it is expected to snow, the plows head out with our weapons against dangerous roads: salt and sand.  Unfortunately, salt is causing harm in an unintended place – in lakes, streams, wetlands and groundwater.

Salt dissolves in water and is transported from roadsides and ditches by melt water and runoff in the spring. Once chloride is in a waterbody, there is no economical way to remove it. As little as a teaspoon of road salt is enough to permanently pollute five gallons of water. 

An estimated 365,000 tons of salt is applied to roads in the Twin Cities metro area each winter. A University of Minnesota study found that 78% of this salt is transported to groundwater, lakes or wetlands.

Once in lakes or streams, chloride can affect fish, the insect and plant community structure, diversity and productivity. At high concentrations, chloride is toxic to plants and animals. Salt in the soil can cause increased alkalinity and compaction, which can harm plant growth. It can also affect the soil’s ability to retain water, contributing to soil erosion and plant stress.

In groundwater, excess salts make drinking water taste salty.  Treating the water by reverse osmosis to make the water drinkable is expensive. The Minnesota Pollution Control Agency (MPCA) found that 30% of wells in the Twin Cities have chloride concentrations greater than the chronic water quality standard. More and more lakes and streams are also showing concentrations that are over the standard. There are nearly 50 water bodies in Minnesota that are already listed as impaired due to the level of chloride in the water.

Municipalities and organizations are reviewing the way that road salt is used. Individuals can help by minimizing personal use of salt during the winter. Salt does not help melt ice below 15 degrees Fahrenheit, and more salt does not result in better melting. Less than 4 pounds of salt per 1,000 square feet is the recommended amount to use for ice melting. Using a hand-held spreader can help reduce over-application.  

For more ways to minimize salt use, visit www.pca.state.mn.us/featured/snow-removal-do-it-better-cheaper-and-pollution-free.

SUSAN HUMBLE is with the Chisago Soil and Water Conservation District, 38814 Third Avenue, North Branch. She can be reached at 651-674-2333. 

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