One of these days you’re going to be driving somewhere after a snow squall on slippery streets and you will mutter to yourself, “Doggone it, why don’t they just put down more salt?” Although you might use different words than “doggone it.”
Well, I have the answer: The pavement might have been too warm, the dewpoint too close to the air temperature, the relative humidity too low, the wind too brisk, the air temperature falling too fast, or the forecast might have said it could rain before it snows, which would wash everything away.
All those issues have to be considered before road crews decide whether to put down anti-icing brine (not road salt) at 40 gallons per paved road mile in advance of a storm. As for applying salt, brine or other material after the storm is past, that’s an entirely different list of variables.
And you thought it was simple.
“Salt really has a science to it,” said Marilee Enus, director of the UNH Technology Transfer Center, which has been conducting training and research on winter operations for years. “Public works agencies need to have a variety of tools in their toolbox. There are many factors to determine what product to use, and when and where they should apply it.”
Other factors include the different conditions on different parts of a driver’s route – it snows far more often in the center of my town than at my house, which is 400 vertical feet lower – the type of plow on the truck and how well the spreader is working.
“You have to calibrate, calibrate, calibrate, know the application rates, know the science. It takes work,” said Enus.
The big complication, as I’m sure you know, is that any substance that makes snow and ice melt more quickly by changing the freezing temperature of water is likely to harm plants, whose life is pretty intertwined with water, and may harm us if it gets into the drinking supply. The money we spend spreading salt and sand in order to drive on roads or stroll on sidewalks with less worry carries an environmental cost.
Consider water quality in the Ossipee River watershed, which covers much of Carroll County.
“Our data revealed that over the last 15 years, over 85% of the sites that we test were trending upwards for salinity. That’s the most significant trend for water quality across all the sites that we test,” said Matt Howe, executive director of the Green Mountain Conservation Group. The organization has released a slew of new material about how to limit salt use when fighting winter’s attempt to make all surfaces friction-free.
“Across the state and across the country, testing confirms that by pouring tons of road salt on our roadways and driveways and parking lots each winter, we are salting our fresh water supply. It’s in our surface water particularly, but increasingly in our groundwater,” he said.
That comment about driveways and parking lots is significant since plenty of salt gets tossed on them every winter, as well as roads. You’ve probably done it yourself but maybe you should think twice about it. (I wear those slip-over-your-shoe ice grippers most of the winter. Kind of a pain but such is life.)
Green Mountain Conservation Group is focusing on getting towns to switch away from dry rock salt, which can bounce and end up in ditches rather than on the road, and instead use various salty liquids known as brine. “Switching over to brining process whenever possible reduces salt by 50% or more,” Howe said.
Because salt crystals need to get wet before they start melting ice and snow, brine works faster than rock salt and generally does a better job staying on the road.
It has one drawback: It can splash up as cars drive past, increasing auto winter corrosion. Howe has the answer: “Whether it’s rock salt or brine, it’s a good idea to wash your car regularly in winter.”
Part of the UNH Tech Transfer Center program helps public works departments make their own brine.
There’s also sand, placed down post-storm to provide some grip. It works pretty well if done properly but is no panacea. Sand doesn’t disappear when the snow melts. Cleaning it out of culverts and ditches in the spring is a big expense, and if it gets into streams and rivers it can clog things up and harm the small, semi-invisible parts of the ecosystem that keep waterways healthy.
Reducing salt and sand use while keeping people safe in winter is a tough problem because it requires the sort of trade-offs that are hard to sell. The apparent cost of less salting is immediately obvious while the benefits are more dissipated over time and space.
That’s part of the reason the UNH Tech Transfer Center, which has long held classes for private contractors who can get a Green SnowPro certification, plans to hold classes for municipal officials and administrators, the folks who determine budgets and operating schedules and staffing levels for public works departments. The more they know about the problem and potential solutions, the better they can respond when people call up town hall to complain.
In the meantime, we can all think twice about tossing salt around our properties or businesses, and drive more carefully and slowly when it’s snowy at all instead of acting like it’s still mid-summer. Our roadside trees, not to mention my well, will thank you.
By the way, if you think I was exaggerating the list of factors to be considered before de-icing roads, check out this flow chart from the UNH Tech Transfer Center.