Rock salt has changed the ecology of the nation’s roadsides, altered the makeup of urban lakes and wrecked more than a few pairs of dress shoes. But even environmentalists concede that after a half-century of looking for an alternative, salt still is the most cost-effective and least environmentally damaging way to keep snow-packed streets safe.
Road commissions in Michigan counties apply a combined 250,000 tons of salt to roads each year. That doesn’t include salt applied by cities, the state and private contractors.
With this season’s early and harsh onset of winter weather, twice as much salt as usual could find its way onto outlying roads. In Oakland County, for example, 17,000 tons of road commission salt have been applied. At this time last year, 2,300 tons had been used. Two years ago it was 69 tons.
In Michigan, much of the salt comes from a century-old mine spidering 1,100 feet below Detroit and several downriver communities. On snowy days, hundreds of trucks fill up at Detroit Salt Co. to arm local cities and road commissions for the struggle with ice and snow.
When the snow melts, the salt mixes with the runoff that empties into lakes and streams. There, it can cause problems.
“Road commissions really do not know the effect their salting has,” said Wally Fusilier, a lake scientist in Dexter, Mich.
Fusilier, who has analyzed hundreds of inland lakes for property owner associations, said several lakes show signs of permanent stratification, where a salt-heavy bottom layer of water prevents the healthy mixing of layers. He attributes the condition to increasing amounts of road salt runoff and salt from water softeners that is discharged into septic systems.
Salting also has changed roadside vegetation in many areas, killing evergreens and other plants in highway medians and within 100 feet of the road.
Those plants have been replaced by salt-tolerant species such as seaside goldenrod and cord grasses, said Tony Reznicek, curator of vascular plants at the University of Michigan. That’s created highway corridors of vegetation usually found in seashore salt marshes or salt flats of the Great Plains, he said.
Because the salt-loving plants cannot exist beyond the highway shoulders, they don’t choke out native species the way invaders such as purple loosestrife and spotted knapweed do.
“So that’s not really a problem, but there are certain natural areas, especially those dominated by evergreens, that perhaps they could be more conservative with the salt,” said Reznicek.
For the record: To avoid injuring grass or ornamental plants, Reznicek doesn’t use salt on the walks and driveway at home.
“I have a bucket of sand by the door,” he said. “Sometimes I take a spade and whack the ice down a bit, but the sand generally seems to work.”
New technology lets drivers cut waste by altering the rate of salt delivery or adjusting it to truck speed.
“Back 25 years ago, we were applying 800 pounds per lane-mile,” said Carlo Santia, Macomb County highway engineer. “Now it’s 450 pounds. The environment is a definite concern, but so far nothing better’s come along.”
Crews use sand on some rural roads. But it doesn’t melt snow or ice and can’t be used in urban areas because it clogs sewers. It also is destructive to the ecology of streams, where its accumulation covers spawning beds and habitats for fish and insect larvae.
Other types of chemicals are effective but prohibitively expensive.
“Rock salt is no worse than the rest of the alternatives,” said Bill Rustem, vice president of Public Sector Consultants, a public policy think tank. “There are reasons to be careful with it, but there’s nothing that’s a heck of a lot safer for the environment.”
Still, experiments continue with alternatives. A recent one used beets.
“Yes, beets,” said Michigan Department of Transportation communications manager Ari Adler. “Its base product is made from beets. It’s being used on I-94. We’ll see how it goes.”
