Road salt threatens Michigan’s lakes and rivers. Can an alternative be imposed?
“It’s a lot cheaper than anything else and it works a lot better,” said Craig Bryson, spokesperson for the Oakland County Roads Commission, which manages the county’s largest road network. from Michigan.
As much as his agency cares about the environmental impacts of road salt, slippery roads are a major risk of winter accidents, and “human life must be the top priority in our decision matrix”.
Scientists and lawmakers have long been concerned about the environmental costs of rock salt mined from underground caverns (such as this one in Detroit), then spread over the roads to keep snow and ice away.
Just one measurement: Last month, scientists at the University of Wisconsin-Madison and Michigan State University released the results of a study revealing that the company’s dependence on rock salt saline Lake Michigan.
As Michigan suffers another freezing winter, state and local highway officials say the most realistic remedy for Michigan’s salt pollution problem is to simply use less. And a pilot program to replace solid rock salt with liquid brine is helping them do just that.
Turning the saline rivers
In Lake Michigan, researchers from Wisconsin and MSU found that concentrations of chloride (an element of salt) have increased dramatically since the 1800s, from 1 to 2 milligrams per liter of water to 15.
And salt concentrations gradually increase by an additional milligram every two years, thanks to the millions of metric tons of chloride entering the lake after the dissolved salt seeps into rivers in the area.
That’s still well below the hundreds of milligrams known to foul drinking water supplies and endanger freshwater species. But even small increases can trigger unknown ecosystem changes and side effects such as corrosion of drinking water pipes, said Hilary Dugan, associate professor at the Center for Limnology at the University of Wisconsin-Madison and author. principal of the study.
Lake Michigan is still “extremely soft,” said Dugan. âThere is no reason to be alarmed. But I think people should be aware that it’s increasing and it’s all because of the salts of human origin. “
More immediately disastrous are the dramatic impacts that salt can have on lakes and inland waterways, especially those near roads that are heavily salty throughout winter and early spring.
Some rivers experience such intense saline shocks, Dugan said that their salinity can sometimes mimic ocean water. The sudden change can release heavy metals from the river bed and harm fish and wildlife.
Salt has altered the chemistry of some inland lakes so much that their water has stopped mixing. Instead, dense, salt-laden water sinks to the bottom, creating oxygen-poor dead zones. Many North American lakes are in danger to become so salty over the next 50 years, they will exceed federal standards for chloride.
Road salt can also alter groundwater, forcing residents to dig new wells and damaging crops.
“When you put salt on your driveway or sidewalk in the spring, you may notice dead grass on the side,” said Mark Geib, administrator of the transportation systems management and operations division. from the Michigan Department of Transportation. “It’s because he kills the grass.”
Beets are a bust. But what about the brine?
For now, many road crews are focusing on using less salt rather than using another substance.
In Oakland County, Bryson said supplementing solid rock salt with liquid brine helped the agency reduce its annual salt intake from around 85,000 tonnes per year in the early 2000s to 63,000 tonnes. today.