A massive pile of Prussian Blue road salt, like that used by the city of Cincinnati to de-ice streets, sits mostly uncovered at the Morton Salt facility on River Road adjacent to the Ohio River near Addyston.
Photo taken near the intersection of Monastery and Baum streets in Mt. Adams on Jan. 21, 2014.
The blue de-icing compound the city of Cincinnati uses does more than clear streets in winter. It can kill stream life, grass and other vegetation.
CINCINNATI -- The hundreds of pounds of road salt spread across Cincinnati streets this week is doing more than melting ice and snow. It increases salt levels in local waterways, kills sensitive stream life, damages roads and can even kill grass and other vegetation.
While Cincinnati officials point to a downward trend in the city’s road salt use, one local environmental expert calls urban waterways like the Mill Creek the “sacrificial lambs” of the de-icing cycle.
“This stuff they are putting on the roads is not good,” said Mike Miller , vice president of Rivers Unlimited and University of Cincinnati professor emeritus of biological sciences--freshwater ecology. “It can be a stressor on a whole bunch of organisms.”
The Toll Of Road Runoff
Miller has studied local water for years, and collected water samples along 25 miles of the Mill Creek Jan. 11. He wanted to measure water quality, including salt content, just after a post-snow event rainfall.
What he found surprised even him.
More than 2 grams of sodium chloride, or salt per liter of water. The upper limit for damage to stream life is 230 milligrams per liter.
“We had 10 times that amount,” he said.
It’s also more salt than he has ever measured in the raw sewage that can overflow into the Mill Creek.
For the darters and minnows, as well as the mayflies and caddisflies that small fish eat, this year's snowy winter may put an end to decades of efforts to revive life along the urban waterway.
“Clearly a lot of road salt does get into the system,” said David Nash , a UC geology professor who has researched groundwater for decades. “There’s certainly an impact on the stream itself. It can change what organisms can survive.”
Road salt inevitably lands along grass edges and near roadside trees, which creates a kind of drought that dries out and can kill plant life, according to researchers .
Even when road salt does what it’s supposed to do, penetrate into streets and melt ice and snow, it causes damage to the very roads it’s treating, setting the stage for potholes in spring.
“The salt can have an impact on highway and highway maintenance as well as the environment,” Miller said. “As the salt expands and lifts the cracks in the asphalt, the asphalt falls apart even faster.”
Less Salt, More Strategies
Department Public Services records show that Cincinnati has cut its salt use by more than half since 2008, from 40,000 tons per snow season in 2008-2009 to 15,000 tons in 2012-2013.
While two mild winters contributed to that decrease, Assistant Director of Public Services Larry Whitaker said that the department has made changes both to save money on salt purchases and to lessen salt’s impact on the environment.
Some of these updated approaches mirror those recommended for use around the country.
For example, the spreaders on trucks are now calibrated to disperse equal amounts per lane mile; trucks also have wings on their tailgates to minimize loss due to salt spray.
Trucks not only have scales to measure the amount of salt they load, they have a road weather information system that allows them to monitor ground temperatures and adjust salt levels accordingly, according to Whitaker.
Other changes involve the de-icers themselves. Cincinnati now makes its own salt brine—two pounds of salt per gallon of salt brine—to use as a pre-wetting treatment that helps salt stick better to roadways, Whitaker said.
Trucks disperse 40 gallons of salt brine per lane mile versus 400 pounds of granular salt per lane mile, he said in an email. Workers also mix brine with beet juice to treat the most extreme road conditions.
This winter’s multiple storms have already proven salt’s worth to Larry Falkin, director of Cincinnati’s Office of Environment and Sustainability, which consults with the Department of Public Services about salt use and management issues.
“We’ve been spreading a lot of salt on the roads,” he said. “Increased salinity in the stream is an inevitable thing if we are going to keep people from sliding off the roads.”
• Blue-tinted road salt is known as Prussian Blue. It contains an anti-caking agent that keeps road salt from clumping on streets.
• In 2003, the EPA declared Prussian Blue a hazardous substance that has the potential (though not yet realized) to break down into one of its components, cyanide. It is now considered a toxic pollutant under the federal Clean Water Act.
• The U.S. Geological Survey provides continuously updated water quality data for sites in all states, including Ohio, Kentucky , and Indiana . You can look up water height, temperature and conductivity (used to measure salt levels) at a variety of the monitoring sites from the comfort of your computer.