Salt is in and sand is out as the preferred weapon against ice on Minnesota's streets and highways.
To satisfy residents who prefer to drive on bare pavement, and to reduce the high cost of spring cleanup, suburbs around the metro area are moving toward using straight salt to clear ice from their winter streets.
Sand, traditionally mixed with salt for added traction, is falling out of favor because it fills in wetlands and ponds and takes weeks -- and many man-hours -- to sweep from the streets each spring.
Salt is more expensive than sand -- about $46 a ton compared with $5 for sand -- but it has other benefits.
Cities find straight salt clears pavement faster and costs less overall when the time, labor and fuel spent on sand cleanup are considered.
By using straight salt this winter, for example, Edina expects to cut spring sweeping time in half -- from six to eight weeks down to three or four, said Edina Public Works Coordinator Steve Johnson.
"That's a huge savings," he said.
So long, sand
This winter, Edina and Eden Prairie are experimenting with straight salt for the first time.
Minnetonka and Hopkins stopped routine use of sand four years ago -- like other cities, they keep a small amount of sand to use mostly in extreme cold weather when salt will not melt ice and some sand is needed for traction.
Richfield began a similar practice six years ago; Plymouth, three years ago. Burnsville is in its second winter of straight salt application, and Bloomington is phasing out sand as fast as its budget will allow.
"In the last five years, the switch has just been huge," said Bloomington maintenance superintendent Jim Eiler.
Woodbury, an exception to the trend, has settled on a 75 percent salt and 25 percent sand mix to keep some grit on the roads for traction until salt starts to work, said street supervisor Jim Triebold.
But the trend is clear.
The shift to straight salt is being driven by a growing environmental awareness about the negative effects of sand as well as the rising costs associated with sand cleanup.
At the same time, more sophisticated salt trucks and brine sprayers have allowed salt to be used more sparingly, with better results. So officials say using less sand has not resulted in using more salt.
"We have better equipment, so we can control salt use and our costs better than years ago," said Doug Hartman, Burnsville's street supervisor.
Said Gary Smith, streets superintendent in Plymouth: "All the operators are more aware of how much salt they are putting down, and we can control the volume."
The state has phased out sand over the past 10 years, said Norm Ashfeld, metro maintenance superintendent for the Minnesota Department of Transportation.
"We found over the years ... it causes pollution and gets into the storm water and gets into the rivers and lakes and causes all kinds of problems."
In the metro area, MnDOT uses sand now "only when it's really, really cold and salt won't work," Ashfeld said.
St. Paul made a full switch to salt four or five years ago.
Minneapolis uses straight salt on main streets but continues to put down sand on residential streets. Because residential streets are plowed later, they are typically plowed not to bare pavement but to a hard, packed snow. On that kind of driving surface, sand adds traction, said Mike Kennedy, who works in the public works division.
While eliminating sand lifts one burden on the environment, salt remains a threat.
Any more than one teaspoon of salt in five gallons of water becomes toxic, said Connie Fortin, a consultant working with Hennepin County to reduce salt in ponds, creeks and lakes.
The salt is a concern for the environment but not for vehicles, said Ray Vogtman, Hopkins superintendent of streets. "We don't find it affects cars. Cars nowadays are 90 percent plastic."
To reduce the use of salt, Fortin recommends that cities spray streets with a brine solution that prevents ice from bonding to the pavement, making it easier to remove snow by plowing. Then less salt is needed after plowing.
Using another method, Minnetonka has been able to reduce salt use by about 1,000 tons a winter by using a rock salt treated with magnesium chloride. The chemical makes the ice melt at lower temperatures, and the moisture in the treatment keeps salt from bouncing off the road, said street maintenance manager Jeff Dubay.
As a result, Minnetonka is using less salt, Dubay said. "We used to start our season buying 5,000 tons of salt and 5,000 tons of sand and we would mix that up together and use it throughout the winter. Now we can go through a winter with 3,000 to 4,000 tons of the treated salt.''
Laurie Blake • 612-673-1711