In Wisconsin and much of the United States we are seeing increasing salt levels in our lakes, streams and drinking water. These increased levels threaten our fisheries, tourism, economy, quality of life, and the health of our waters.
Where is the salt coming from?
In Dane County, salt entering our water is coming from two main sources:
Winter Application: Road salt has been used as a deicer on streets in the Dane County region since the late 1950s. Every year, more than 525,000 tons of salt is dumped on our state's surfaces, enough to pollute over 400 billion gallons of Wisconsin’s water. According to a recent report from Public Health Madison Dane County, more than 38,000 tons of salt were spread on Madison and Dane Co. roads during the winter of 2016-2017, and that doesn't include what was spread on parking lots, sidewalks and driveways. That is enough to pollute more than 29 billion gallons of water.
Water Softeners: Water softeners help remove hard water minerals (Magnesium and Calcium) from our water before the water is used in our homes and building. When water enters the softener, it passes through special resin beads that attract and trap the hard water minerals like a magnet. Eventually, the resin beads have captured all of the minerals that they can so the softener flushes them with salt water (brine) to remove the minerals from the resin. This water goes to our wastewater treatment plant where the salt passes through the system and enters into local water ways.
What are the Impacts?
Once salt is in the environment it doesn’t go away. It ends up in our lakes, rivers, streams and wetlands, putting our aquatic life at risk and endangering our freshwater resources. Our local lakes, waterways, groundwater and soil have been absorbing virtually all of the salt spread in the city for more than six decades. Chloride from salt is toxic to small aquatic life and degrades the natural eco-system of our lakes. Once salt is in our waterways, it does not break down – it’s here to stay. It only takes 1 teaspoon of salt to permanently pollute 5 gallons of water to a level that is toxic to freshwater ecosystems.
In Dane County, winter maintenance salt causes large seasonal spikes in chloride levels of area lakes, rivers, streams and wetlands. Salt is already showing up at alarming levels in local water resources. Madison’s Lake Wingra’s chloride concentration has increased from 5 mg/L before the use of road salt to 115 mg/L today. In Lake Mendota, salt concentrations increase about 1 mg/L each year. If that rate continues, the waters will eventually taste salty and exceed toxic concentrations for aquatic life. Once salt is in the environment it cannot be recovered.
For more information about the environmental impacts of road salt and other deicing chemicals, check out the Minnesota Stormwater Manual (PDF).
Data source: 2016 Road Salt Report, Public Health Madison—Dane County
*Wells and Private Drinking Water Graph: this figure compares chloride concentration trends in deeply cased wells, which draw water from the lower aquifer, and wells with short casings, which draw water from both the upper and lower aquifers. Check out the Public Health Madison-Dane County Road Salt Reports to learn more.
Once salt gets into water it is very difficult to remove. Treatment, like reverse osmosis or ion exchange, is costly to install and even more expensive to operate. It could cost millions or even billions of dollars, so preventing salt from entering our drinking water resources in the first place is the most cost-effective solution.
Last year, Wisconsin spent $36,170,919 on salt for its highways. That is about 526,199 tons of salt and that doesn't include what communities, businesses and homeowners applied (source)!
Salt alters the composition of soil, slows plant growth and weakens the concrete, brick and stone that make up our homes, garages, bridges, and roads. One ton of rock salt causes between $800 and $3,300 of damage to buildings, bridges and other infrastructure (source).
Winter salt use can also be hard on our furry friends. Road and sidewalk salt can cause irritation on toes, feet, and skin. Problems can also arise if a dog eats salt or licks their paws after a walk. Excess salt can cause toxicity concerns, throw off their electrolyte balance, or cause hypertension, cardiac arrhythmias, vomiting, increased urination, increased thirst, muscle tremors, or seizures. You can keep your pets healthy by shoveling first, and applying only the right amount of salt to keep sidewalks safe.