The recent snows signaled the beginning of winter road maintenance for lakeside cities, many of which are also taking steps to protect Lake Minnetonka and other local waterways from potentially harmful salt runoff.
According to information released by the Mississippi Watershed Management Organization, water pollution from salt (or chloride) is widespread in the Twin Cities, and the vast majority of it comes from winter maintenance de-icers.
As little as a single teaspoon of salt pollutes five gallons of water, and a 50-pound bag holds the potential to pollute 10,000 gallons. Additionally, salt dissolves and becomes invisible shortly after it is applied, making its removal expensive and difficult. This is significant because prevention is the only feasible way to protect clean water.
When snow and ice melt, they wash salt residue into lakes, streams, wetlands and groundwater. Once it is in the water there is no way to remove the chloride, and at high concentrations it can harm fish and underwater plant life.
"When it gets super cold you need to find a product that contains a magnesium or a calcium chloride, or something like a glycol. Or you can switch to sand, which isn't going to melt anything, but it will provide traction for you," said Carolyn Dindorf, vice president and limnologist at the Hamel-based Fortin Consulting Inc., whose mission is providing project design and coordination which will unite citizens, environmental organizations and industry in the common goal of improving rivers, lakes and wetlands.
Local public works departments have noted the effects of salt pollution, taking it into account when de-icing streets.
"We deal with it by monitoring our applications better than we did in years past, and we have a very aggressive cleanup program in the spring. As soon as we can get our street sweeper out we try to pick up as much of the sand residue that is left over from the winter as we can, before it gets into our storm sewers," said David Dudinsky, director of Public Service for Wayzata. The city uses a combination sand-salt mixture for de-icing.
Wayzata has also installed sump manholes, structures that allow solids to settle at their bottoms, which prevents them from washing into Lake Minnetonka with the runoff ice and snow melt. A piece of wet-dry vacuum equipment is used to clean the manholes on a yearly basis.
Minnetonka has also addressed the issue, adopting a brine and pre-wetting system that has reduced the city's use of de-icing salt by approximately 30 percent.
"We try to minimize the salt we use, it kind of depends on the snow. We can control how much salt the trucks put down, so we will notify the drivers of what rate to set their trucks when they're spreading salt. We also pre-wet the salt with brine as it's getting dumped out of the truck, that helps it work quicker and helps us use less," said Darin Ellingson, street and park operations manager, Minnetonka Public Works.
Residents can also contribute to the overall safety and environmental health of their communities through a few simple habits, like removing snow from driveways and property using tools like snow blowers or shovels, depending on the amount of snowfall, before using salt.
Salt should also be applied only to clear surfaces and in an even spread pattern with no overlapping crystals, and users should drop no more than four cups of de-icing material per 1,000 square feet. Sand can be used in extreme cold or in any situation where salt will not work, and excess sand and salt should be swept from cement. On warm days when melting ice becomes runoff, individuals should avoid using salt at all.
Cities are attempting to reduce chloride-saturated runoff while still utilizing de-icing salt for its primary purpose - to keep drivers and pedestrians safe on local streets and sidewalks. While smaller plow crews operate during snowfalls of less than two inches, Wayzata and Minnetonka have snow emergency procedures in place for storms that yield a greater amount.
Wayzata typically declares the emergency by 8 p.m. the evening of the storm, requiring residents to remove all vehicles from the streets by 2 a.m. the following morning to allow snow plows to clear streets before the morning rush hour commute. Residents can follow snow emergency developments on the city's website, and Dudinsky also addressed the importance of plow safety.
"People just need to be more aware that because of our snow plow equipment on the trucks we can't always see who's right behind us," Dudinsky said. "A lot of times in our plowing efforts we'll stop and back up to take another pass. With the slippery roads it's dangerous, so we ask drivers to stay back 100 feet or more when our lights are on and we're plowing."
Minnetonka residents can receive snow emergency-related information by following @MinnetonkaMN on Twitter. Plowing operations usually take place between midnight and 4 a.m. during an emergency, when nearly 30 trucks cover eight to 15 miles of roads on designated routes throughout the city.
After the roads have been cleared and de-iced, perhaps the most important thing for drivers to remember is one of the most basic.
"In the city of Minnetonka, we have a lot of hills and a lot of curves in our roads," Ellingson said. "So it's more important for people to just slow down, and take their time getting around town."