Posted by Angie Hong | Posted in Keeping water clean | Posted on 18-11-2011
Tags: groundwater, road salt, water pollution
It’s hard to believe that it is true, but Baby Hong is due on December 1, which means that for the first time ever my husband and I will be spending Thanksgiving and Christmas here in Minnesota instead of traveling to Milwaukee or beyond to visit family for the holidays. In truth, I think that avoiding holiday travel for one year was at least ten percent of the reason we decided to have a baby in the first place.
When I think back on the eleven years that I have lived here, my winter driving escapades blend together in a blur of snow, ice, sleet, rain and white knuckles. There’ve been jackknifed semi-trailers, closed down stretches of interstate and bumper to bumper traffic. My personal favorite was the year that we left Minnesota around 5pm to drive to Milwaukee, picked up my mom after her nursing shift got done at midnight, and then continued on through the night to get to East Lansing by early morning on Thanksgiving Day. We spent that day cooking and eating, the next day throwing a 90th birthday party for my grandmother, and on the third day, packed up her entire house, piano and all, so that she could move into an assisted living facility, and then drove through a snowstorm in Kalamazoo to get back to Wisconsin and then Minnesota for work on Monday.
Given my many harrowing experiences with winter driving, it may come as a surprise that I am still very much in favor of recent efforts across Minnesota to reduce the amount salt used for winter road and parking lot maintenance. You see, salt is only part of the equation when it comes to keeping our roads safe in the winter. To begin with, dry rock salt is completely ineffective at melting ice when temperatures are less than 10º and only minimally effective at temperatures less than 15º. During our typically bitter, cold Minnesota winter weather, all of the salt that is dumped on top of parking lots, driveways, walkways and roads serves absolutely no purpose until the weather warms up and begins to melt the ice. In the meantime, wind blows half the salt off the pavement and the rest gets washed away when the snow and ice finally do melt. Using salt as a substitute for plowing or shoveling is equally ineffective. The rock crystals might bore holes in the snow, but they don’t break up the bond between the snow and the pavement and do nothing to keep cars from sliding and careening out of control.
If salt were harmless, its excessive use during the winter would merely be a waste of money and a nuisance. Instead, salt is a major threat to urban streams and our groundwater resources. As salt dissolves in water, the chloride ions remain intact and can move through the environment without breaking down. Almost all of the salt spread on our roads and parking lots eventually migrates to surface waters or groundwater and once there, is almost impossible to remove. There is a real danger that some of our groundwater drinking resources will become unusable in the future as chloride gradually accumulates in the environment. Meanwhile, there are already some streams in the metro area with chloride levels high enough to kill off fish and benthic organisms that form the base of the food chain. Furthermore, when salt finds its way into streams and lakes, it prevents oxygen and nutrients from cycling normally and can also release toxic metals from the sediment.
Because road salt threatens both our health and the health of the environment, the Minnesota Pollution Control Agency, University of Minnesota LTAP, and others have been offering trainings to city, county and state road plow operators, as well as to independent contractors responsible for maintaining parking lots at churches, schools and commercial buildings. As a result, the Minnesota Department of Transportation and many of the larger metro area communities have dramatically reduced the amount of road salt used each year. Instead, drivers have been trained to pre-treat roads when storms are forecasted, precisely measure the rate of salt and chemical application, and target salt to the areas that need it the most – intersections, hills and curves.
The next major hurdle is to reach communities in greater Minnesota, smaller cities and townships within the metro, many of which use private contractors for their winter road maintenance, and the many parking lot contractors that have not yet attended trainings. Although residential salt use is a much smaller problem, homeowners can also help by limiting the amount of salt used on driveways and sidewalks. Calcium chloride, potassium acetate, and magnesium chloride are three salt alternatives that can melt snow in below zero temperatures and a light anti-icing treatment with magnesium chloride or salt brine prior to light to moderate snow or freezing rain will help to prevent ice from bonding with the pavement. Most often, however, a shovel is the most effective weapon against snowy, icy walkways.
More importantly, local residents can encourage public works staff and private contractors in their communities to attend road salt trainings if they haven’t already. We can also take personal responsibility for keeping our roads safe in the winter by driving slower and avoiding unnecessary travel in the middle of snow and ice storms. That’s the strategy I’ll be adopting this winter – staying home for the holidays to hang out with our new baby. I’d like to think I’ll be doing my part to keep the roads safer and the water cleaner.