Winter is here, snow has fallen, temperatures dip and along comes nature’s slip and slide: ice.
To negate the dangers of ice, people have become accustomed to dumping salt and carefully walking (or rather, waddling) away as the salt works its magic. But after the ice melts, the water soluble chemical does not simply disappear. Instead the chloride sticks around, eventually washing into bodies of water potentially throwing off the local environment’s biochemistry.
An estimated 365,000 tons of road salt is applied to the streets in just the Twin Cities metro alone each year, according to the Minnesota Pollution Control Agency. About 78% of salt applied within the Twin Cities for winter maintenance is either transferred into groundwater or local lakes and wetlands, according to a study by the University of Minnesota.
While the MPCA says salty waters are becoming more of an issue in the state, Kevin Strauss, the community engagement coordinator at the Cannon River Watershed Partnership, says salt intake in the Cannon River Watershed isn’t a major concern right now. Although there is one tributary that has more salt than Strauss said they would like to see in it. Even so, consideration of environmental impacts is still important this winter, as concerns could later arise if neglected. The MPCA lists both the Straight River and the Cannon River as “not impaired” by chloride on its website.
With high flow volume, the salt is generally carried out of the community and to somewhere else. The Cannon River’s flow volume is three times what it was in 1911, according to Strauss. The Cannon River is flowing more now than it has in history, due in part to more rain due to climate change.
“Another part of it is that the ponds and wetlands that used to be here that would slow down and hang on to the water aren’t doing that anymore, we’ve gotten really efficient at draining water,” Strauss said.
Salt levels can be measured by how easily electricity moved through the water. The more salt there is in a body of water, the more easily electricity moves through that sample. Salty water can impair water by threatening aquatic wildlife and drinking water, although the change is a slow process.
Once salt enters water, it becomes difficult to remove. It only takes a teaspoon of salt to permanently pollute five gallons of water, according to the MPCA.
“There’s not really any way to remove it. You know with some other sorts of problems that we run into, there sometimes are solutions of one form or another that you can do to clean up a pollutant, but salt isn’t one of those,” Strauss said.
Two-thirds of Minnesotans rely on groundwater for drinking, according to the MPCA, but salt can contaminate those sources, impacting the water’s taste and health.
High concentrations of salt can be deadly to wildlife such as fish, aquatics bugs and amphibians. Plants absorbing salt water through their root system negatively impacts their health, altering plant community structure. Meanwhile, excess salt can prompt soil to lose its ability to retain moisture and nutrients, making the ground more susceptible to erosion, the MPCA said.
If the negative environmental impacts didn’t cut it, salt also damages and erodes road surfaces, bridges and some metals, potentially raising costs for road repairs.
Understandably, people want to be safe out on the roads and walking around the neighborhood, and salt does help remove ice. But there are ways to prevent excess use of salt and alternatives to salting that should also be considered when determining how to get rid of the pesky ice.
Technically salt doesn’t melt ice, but rather lowers the freezing temperature of water, in effect impairing water molecules’ ability to form ice crystals. However, the salting technique stops melting ice when you get down to 15 degrees Fahrenheit. Thus when it’s below that temperature, it doesn’t matter how much salt you put down, it’s not going to melt, Strauss said. So before dumping more salt, check the temperature.
“You want to make sure that you’re only using salt when it’s going to work, so when it’s 15 degrees Fahrenheit or warmer. And also, usually people over salt,” Strauss said.
The MPCA says to use less than four pounds of salt per 1,000 square feet, for reference the size of an average parking space is about 150 square feet. They also suggest purchasing a hand-held salt spreader to apply the salt consistently across the pavement. Sweep up excess salt on dry pavement, as the salt is no longer doing any work. Excess can be applied elsewhere or thrown away, the MPCA said.
One way to prevent ice buildup is to manually remove snow and ice early with shovels and ice scrapers. If you can remove snow before it melts and refreezes or before it gets compacted into ice, the better and thus the less salt you have to apply.
“Also making sure that your downspouts and storm drains coming off your house are not aimed toward pavement,” Strauss said. “That’s the thing that we recommend year round actually because that reduces stormwater runoff that goes down your driveway and right into the street and storm drains because it can pick up oil or other things from the street, as it’s flowing down and so it’s on average a lot better to aim your downspouts onto your lawn.”
Sand is an alternative when temperatures dip below 15 degree Faherenheit, because it improves grip on sidewalks and around driveways. While there are alternative products to salting that have less of an impact in terms of salinity, Strauss said these products are generally more expensive and prevention of ice build up is a better option.
While ice-melting salt contributes to the problem, Strauss also mentioned that water softeners are also contributing to the salty problem. Brine, water that contains salt, drains to local wastewater treatment plants, but these treatment plants aren’t designed to remove salt from the water before pumping it back out into lakes and tributaries.
“And many of us, you know, got a home with a water softener and whatever the setting was when we moved in here 12 years ago is still the setting today, which may or may not be the right setting,” Strauss said.
About 65% of the chloride going into wastewater facilities is coming from residential and commercial water softening, the MPCA said.