If you live in a place with both cars and snow, chances are youve witnessed first hand the annual salting of the roads. Since at least the 1940s, Americans in the snowy states have salted annually, often many times a year, in an effort to make our roads safer. Ask anyone who has spun out while driving, or unwittingly hit a patch of black ice: slippery roads are nothing to scoff at, and salt can be a necessary, even life-saving, tactic for winter road warriors.
The problem is, salting the Earth is something of a Biblical notion: its what one did to an enemy to make land unproductive for agriculture.
In the 20th century, salt transformed from ancient warfare tactic to an economically necessary step that has kept the countrys industrial engine revving. Salts new job became keeping U.S. roads open at whatever cost. The economy depended on it.
But now, those Biblical results are manifest: The environmental damage must be reckoned with. Yet, we simply cannot afford to go salt-free.
Today, shutting down a states roads due to winter weather can cost hundreds of millions of dollars, says Michael Smith, technical training specialist with Bay State Roads at the University of Massachusetts Transportation Center. For example, shutting down the roads of Massachusetts (as happened statewide during a 2013 noreaster) can cost between $300 and $700 million dollars per day, Smith says.
And so, as a nation, we dump 22 million tons of salt every year on our roads.
Fish, animals, insects, plants and algae have changed their behavior in response to the current levels of road salt washing into their habitats. Some species of frog are, incredibly, changing sex as a result of these massive doses of salt. High enough doses can kill them and other wildlife. For the naturalist, folks who like to fish or otherwise enjoy nature, and for locals who rely upon natural tourism, salts side effects cant be ignored.
A hybrid beet juice-salt water brine is helpful to coat asphalt in advance of a snowstorm to prevent precipitation from sticking to the roads. (AP Photo/Gene J. Puskar)
Salt runoff also makes its way into our drinking water supply. It corrodes our pipes, which leads to higher levels of lead, manganese and mercury (among other heavy metals that are all toxic to humans) in our drinking and bathing water. Experts agree that exposure to such high levels of salt can even be problematic for people required to eat a low-sodium diet.
Perhaps more relevant to the pocketbook is the effect of salt on our vehicles: That rust on your car? Salt. The road deterioration that damaged your car? Salt. Or perhaps more specifically, magnesium chloride. In fact, the umbrella term road salt refers to any one of three chlorides: sodium chloride (rock salt), magnesium chloride and calcium chloride.
Dr. Rick Relyea is the director of the Darrin Fresh Water Institute and the Jefferson Project at Rensselaer Polytechnic Institute in Troy, New York, which has been studying the effects of road salt since 2014.
Relyea stresses, Its undeniably important for safety to remove ice. But at what cost?
In general, what we now know as road salt can be lethal to a wide variety of plants and animals, and as is always the case, it depends on the dose, Relyea says. So if we have high amounts of road salt we can kill all kinds of plants and animals. In different parts of the world its different.
In the last five years as public awareness of the problems with these chlorides has grown, municipalities nationwide have responded with changes that, they hope, will be cost effective, good for the environment and good for public safety.
In Lake George, New York, environmental research has uncovered surprising and significant damage to the natural world, and has inspired a shift in how roads are salted. In Cambridge, drinking water is so heavy with salt runoff that coffee machines are corroding, and the city seeks to mitigate the problem both within their own city limits and in neighboring towns that affect their watershed. And in Helena, Montana, concern over salts effect on the environment and cars has inspired a program that takes recycling to new levels.
In Lake George Village, New York, says Relyea, they use a brine, applying it to the road before a snowstorm, which makes it harder for the snow to stick to asphalt and easier to remove by plow.
Brining might sound like something you do to meat before a holiday meal, and its a similar principle employed here. A brine is made of, for example, 80 percent water to 20 percent salt, and then that is what is put down on the pavement before a flake ever falls. Brine prevents the snow from sticking, making it easy to plow, and it prevents black ice from forming. Many municipalities have their own brine recipe that can be tinkered for local conditions. Often that recipe calls for a little carbohydrate, as more than one expert told us.
Carbohydrates meaning, essentially, sugar lower the freeze point. Beet juice is the go-to in some places, while others experiment with molasses, corn, and soybean oil. Its the sugar that makes the brine sticky and effective at low temperatures. Think the same principle as putting a Coca-Cola or a bottle of vodka in the freezer; neither will completely freeze. In that way, the brine recipe really is, well, a recipe.
If you brine the road first, the snow doesnt stick and the road can become dry asphalt quickly. If you pour rock salt on top of already fallen snow, more salt needs to be used, and then the snow melts top-down, waiting for vehicle tires to crush the salt and mix with the snowmelt to become brine anyway rock salt doesnt do anything to the snow unless it goes to a liquid or a brine state. Applying pure salt after the snow has fallen takes more time, more salt, and can leave lower layers of snow stuck to the pavement, because, youre melting top-down instead of (as with the brine) bottom-up.
The Jefferson Project uses a network of high-frequency sensors, including this vertical profiler, to obtain real-time data on the movement of water and pollutants through the Lake George watershed. (Photo courtesy Jefferson Project)
In addition, says Relyea, Lake George changed the edges on their plows. A standard plow, probably ten to 12 feet wide, typically leaves snow in those dips asphalt roads incur. The plow is unable to follow the natural curves of the road. So the community started using a live edge of 5 smaller plows mounted on springs, so it can fit the contour of the road, and remove more snow.
Making these two relatively small changes has reduced the amount of salt used in Lake George by 30 percent in the last few years, which, says Relyea, is a big improvement.
The vast majority of salt Lake George uses is sodium chloride. But is that really safer than, for example, calcium or magnesium chloride? Not really, says Relyea. Depending on what species [of plant, algae, fish, reptile or animal youre talking about], some [chlorides] are much more lethal to plants and animals than others, and its not always the same one each time.
Take the rainbow trout. Calcium chloride is worse for the fish than sodium chloride, he says. Magnesium chloride is bad for the fish too. Which plant or animal [you talk about] depends which [road chemical] is worse.
Impacts are, in some cases, pretty straight forward, says Relyea. Salt does things to animals no one would have guessed. For example, when wood frog tadpoles are exposed to high concentrations of salt, their sex can change. No one had that expectation, says Relyea.
Whats really concerning [are the] groups of animals particularly sensitive to salt, Relyea adds. Zooplankton eat algae. Theyre the reason a lake is clear. Weve seen in Canada, where it only takes 50 milligrams [of salt] to kill them off. Bigger fish eat those zooplankton, and then bigger fish eat them, and so forth. In an ecosystem built upon those zooplankton, that food source dying off is a problem.
We need to be concerned about that, says Relyea. There is some level of hope. And that is that some animals can rapidly evolve higher tolerance to salt, within a matter of months. They are more tolerant than three months earlier. You can still kill them, Relyea adds. But, theyre a little more tough. It does suggest, others might have that ability. This ability to evolve might buy us time [with some species], but some things will not evolve and will die.
And then there are the unintended trade-offs if species do evolve tolerances to road salt. Plankton, says Relyea, evolve, but no longer have a circadian clock. That clock previously dictated things like when to surface and when to go deep, all to avoid predators. The loss of the circadian clock makes them a sitting duck for predators. Thats a huge impact, Relyea says. Again, he notes, Not at all something we expected to see.
Another alarming consequence Relyea cites is the increasing salinization of the Great Lakes, where invasive, salt water-friendly species such as zebra mussels are doing well now. If the Great Lakes get saltier, invasive species will likely do even better.
Back at Lake George, the spring snowmelt runoff brings a mega-dosing of salt. During a spring rain or melt, Relyea says that salt levels in streams can spike to 2,000 milligrams of chloride per liter of water, instead of the 230 milligrams of chloride per liter of water limit dictated in EPA guidelines. (Canadians, he notes, have set the bar even lower, at 140 milligrams per liter.) Relyea says they dont know what the effects of such short-term, massive spikes are yet. The short-term guideline set by EPA is 860 milligrams per liter, he notes. We expect it causes lots of harm.
Lake George is a key driver of the Adirondack regions $2-billion tourism economy, so preserving the natural environment is important. Clear roads and a healthy ecosystem are crucial for seasonal tourism. To put the whole watershed on a low-salt diet, Relyea says, is a win.
Cambridge, Massachusetts, home of both Harvard and MIT, has its own water source, separate from many of the Greater Boston areas systems. But the towns drinking water reservoirs are affected by multiple lanes of high-speed, high volume traffic on Route 4, in addition to the 225,000 to 250,000 cars that travel Route 128 every day. Under those conditions, and during a snowstorm, road salt crews are in high demand and can get stuck in traffic, which makes de-icing more difficult. The need to keep busy roads safe for travel makes the watershed more prone to high salt content. A look at Cambridges water quality report over several years shows sodium content from road salt runoff to be a significant water contaminant.
For Cambridge coffee connoisseurs, the chlorides in the water mean trouble for the machines that brew their high-quality coffee. Even machines under warranty wont be covered when subjected to salty water. Under heat and pressure, chloride becomes acidic and corrosive. This means the equipment doesnt last as long as it should, reports local NPR outlet WGBH.
Continued here:
Cities Are Cutting the Salt from their Winter Road Diets - Next City
