Have you noticed piles of salt or white, chalky residue on sidewalks and parking lots nearly everywhere you go? The threat of potential lawsuits that could follow an injury from someone slipping on the ice on their property causes significant oversalting. It’s a legitimate concern; injuries from falling can be serious and lawsuits can be costly. But a commonly overlooked point is: more doesn’t mean safer when it comes to applying de-icing chemicals. It just means adding unnecessary pollution to our lakes and rivers, because when snow and ice melt, the water runs into our lakes and rivers—and the salt goes with it.
A study by the University of Minnesota found that about 78% of salt applied in the Twin Cities for winter maintenance ends up in groundwater or remains in the local lakes and wetlands. Currently, there 50 waters in Minnesota that have unacceptable levels of chloride. It only takes a teaspoon of salt to pollute 5 gallons of water and an estimated 365,000 tons of road salt is applied in the Twin Cities metro area each year. Within the Bassett Creek watershed, two streams and four lakes are “impaired” due to high concentrations of salt.
Conventional thinking might be, ‘Salt occurs naturally. What’s the big deal?’ While it’s true that chloride can be naturally present in Minnesota’s groundwater in varying amounts due to the weathering of rocks, the volume of salt added to water due to human practices is anything but natural. Whereas non-natural chloride enters groundwater from several sources such as, fertilizer, water-softening salt, and septic systems, deicing salts are thought to have the biggest impact.
Since 75% of Minnesotans rely on groundwater for drinking water, increased salt levels in drinking water poses health risks to a significant portion of the population—especially babies, people with diabetes, high blood pressure, kidney disease, and heart problems. The Minnesota Pollution Control Agency (MPCA) groundwater report found that 27% of monitoring wells in the Twin Cities metro area in the sand and gravel aquifers had chloride concentrations that were greater than drinking water guidelines set by the federal Environmental Protection Agency (250 mg/L). And 30% of wells in the Twin Cities metro area had chloride concentrations greater than the chronic water quality standard (230 mg/L). Chronic refers to ongoing exposures and effects that develop only after a long exposure. [For more information check out the full report: The Condition of Minnesota’s Groundwater, 2007-2011 or the summary of key findings: The Condition of Minnesota’s Groundwater, 2007-2011: Summary.]
Excessive salt impacts everything from the health of our soils, plants, fish, insects, pets, and wildlife to accelerating infrastructure deterioration. Salts can cause soil to lose its ability to retain water, which leads to erosion and increasing sediments going into lakes. Excess salt can make soil more alkaline and compact, and less permeable, making it more difficult to store nutrients that plants need to grow. Direct deicing salt can kill plants and trees along sidewalks and roadsides. Plants can also be harmed by taking up salty water directly through their roots. High levels of chloride are toxic to fish, aquatic bugs, and amphibians. Even at lower levels, chloride can negatively affect the fish and insect community, diversity and productivity. Chloride also changes the density of water. This, in turn, can negatively impact seasonal mixing of lakes causing a decrease in oxygen levels required by aquatic life. Chloride also corrodes road surfaces and bridges and damages reinforcing rods, increasing maintenance and repair costs. Deicing salt accelerates rusting, causing damage to vehicle parts such as brake linings, frames, bumpers.
And, while it certainly is effective, its overuse is resulting in permanent damage to our lakes and rivers and even in groundwater. In fact, 50 lakes and streams in Minnesota have chloride levels above state standards. And perhaps even more eye-opening is that chloride concentrations are above the water quality standards in 30% of the groundwater monitoring wells in the Twin Cities metro area.