Auggie Perez of the Cedar Rapids Public Works Department fills up a salt truck Dec. 14 as teams prepare for imminent cold weather and frozen roads. (Geoff Stellfox/The Gazette)
Salt storage buildings at Cedar Rapids Public Works are emptied as teams prepare Dec. 14 for cold weather and frozen roads in the city. (Geoff Stellfox/The Gazette)
Auggie Perez of the Cedar Rapids Public Works Department fills up a salt truck Dec. 14 as teams prepare for cold weather and frozen roads in the city. (Geoff Stellfox/The Gazette)
When snow cloaks roads in slippery cocoons, crews across the state spring into action to keep streets safe for drivers. But one of the most widely used snow-fighting agents — rock salt — comes at a price, both financially and environmentally.
Rock salt lowers the freezing temperature of water and helps break bonds between the ground and ice, making it easier to clear snow. The Iowa Department of Transportation applies about 200,000 tons of rock salt per year to state highways. The city of Cedar Rapids uses between 8,000 and 10,000 tons annually, and Iowa City crews spread about 3,000 tons each winter.
That salt typically costs anywhere between $70 and $100 a ton — making a dent in government budgets.
And when the salt leaches into waterways, it can alter ecosystems, harm aquatic organisms and impact water quality. A 2018 study showed that U.S. rivers and streams have developed higher salt concentrations and higher pHs in recent decades, blamed in part on the application of road salt.
Iowa’s statewide average for chloride concentration in rivers and streams fluctuated between 17 and 25 milligrams per liter from 2001 to 2018. Historical data showed average chloride concentrations on some Iowa rivers were less than 10 milligrams per liter in the 1940s and 1950s.
That’s why Cedar Rapids and Iowa City are working to reduce the amount of salt they scatter onto Eastern Iowa roads — and representatives told The Gazette how they’re doing it.
“The big driving force in the past used to always be the budgetary items,” said Cedar Rapids Assistant Public Works Director Michael Duffy. “Just as important as the budget is the environmental impact and being good stewards of the material that we use.”
“Whatever salt we put down on the road finds its way into our streams. It’s not great for the environment,” said Iowa City Streets Superintendent Brock Holub. “So, the more we can reduce the amount … that go into our streams, the better off we’re going to be.”
Cedar Rapids reduces salt usage
In Cedar Rapids, crews load trucks with rock salt that is released onto moving belts. The belts move the salt to the back of each vehicle and onto a spinning wheel, where it is then scattered across desired areas.
Thanks to improved calibration of this equipment, along with better planning and practices, Cedar Rapids has decreased its road salt application rates by 30 percent in the last four years, Duffy said.
By knowing exactly how much rock salt is loaded into each vehicle — and the rate it’s being applied at — the city can better track application. And by using the materials where and when they’re most effective, crews can use less. The city also pre-wets the salt before application, which helps control its bounce and scatter.
“Then you don’t have as much material getting kicked all over into areas where you don’t want salt and it’s less effective,” Duffy said.
According to the city of Cedar Rapids website, here are some snow-fighting materials being used around the city:
• Salt: Most effective when applied during temperatures above 15 degrees
• Sand/salt mix: Most effective when temperatures are dropping or conditions require the abrasive qualities of the sand for added traction.
• Sand/salt/flake chloride mix: Most effective when temperatures plummet. This tactic uses a 3:1 sand/salt mix and combines it with the added melting power of chloride flakes. The chloride is effective at melting snow/ice off the road at temperatures that drop to 20 below zero.
• Salt brine: Most effective when used before the snow falls or ice forms, and when temperatures at the time of application are above 15 degrees. The brine helps coat the roads and makes them less susceptible to sticking snow.
• Salt brine/carbohydrate blend: When blended materials are used, they better adhere to the pavement and lengthen the effective time the material is present on the road surface.
Cedar Rapids usually experiences around nine major snowfall events each winter season, with crews leaping into action anywhere between 30 and 50 times. With more than 1,4000 lane miles to clear, it could take crews up to 12 hours to reach every street. Busier roads and emergency snow routes are prioritized.
Crews also often apply salt brine — a liquid anti-icing treatment that’s 23.3 percent salt — before snow falls to hinder any bonds from forming between snow and pavement. Brine can’t be used before every event, though, depending on temperatures.
Iowa City ‘more conservative’ with salt application
As with any location, the amount of rock salt applied in Iowa City each year depends on the number of snow events and amount of snowfall. But crews are trying to use less salt whenever they can, Holub said.
“We’re trying to be more conservative where we can,” Holub said. “What have we done over the last few years? The biggest thing is training your plow operators.”
The city has started to monitor how much salt operators are laying down per lane mile, like the Iowa Department of Transportation does. Operators are also looking out for how cold it is and how much snow is falling so they can properly approach each event.
Iowa City also introduced salt brine into its operations in 2020, using it to treat pavement before snowfalls and to treat salt before application, which reduces scatter. Crews also treat the salt with an organic liquid called AG 64 that contains a lot of sugar. The sugar combined with chloride helps the salt’s effects last longer.
“Our goal is never to melt snow,” Holub said. “Our goal is to keep the road from getting slippery — and so, basically what we’re trying to do is break the bond in between snow and pavement.”
Educating the public
City crews aren’t the only ones applying salt to the ground in the throes of winter. Residents and business owners often do so, too, on parking lots and sidewalks.
This year, through an Iowa Stormwater Education Partnership, the city of Cedar Rapids and the American Public Works Association developed a program called I-SALT to help educate the public, contractors and other jurisdictions on the best snow-fighting practices. The first presentation took place in November in Marion.
“(The public) uses a lot of salt, so really making sure that everybody’s using it effectively is important for us,” Duffy said. “It’s sort of a fine line between safe and excessive use.”
Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.
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