Experts agree that there are few alternatives to ordinary salt as a versatile, reliable, and economical aid to winter driving. First tested on roadways in New Hampshire in the 1940s, salt has amassed a stellar record for improving safety and cold-weather mobility. However, casual observation reveals that high concentrations of salt that occur near roadsides due to deicing can lead to several detrimental environmental impacts, and closer study has confirmed that the negative effects can extend much further.
According to a United States Geological Survey (USGS) study released in 2010, the effects of road salt on the environment can range from direct toxicity to plants and aquatic organisms to changes in lake dynamics in the receiving waters and the increasing dominance of salt-tolerant aquatic species. Furthermore, salt can linger in the soil, accumulating over decades in a watershed, to eventually make its way into aquatic ecosystems or into groundwater, potentially degrading valuable drinking-water sources.
Yet no one denies sodium chloride’s value in preventing accidents, injury, and loss, and it remains the most popular of deicing materials in the US. Nonetheless, people familiar with the issue generally agree, it is a worthy goal to try to mitigate the impact of salt used for winter safety operations. As the USGS notes in its report, A Fresh Look at Road Salt, it is next to impossible to remove dissolved salt from the environment once it has been applied; therefore, reducing the amount of salt used presents the best prospect for controlling its negative impacts.
Connie Fortin, founder of Fortin Consulting, says agencies that have adopted a scientific approach to deicing and anti-icing, sometimes called “sensible salting,” are beginning to realize reductions in the amounts of chlorides used to treat road surfaces, without diminishing safety. Fortin, who provides training and consulting services in salt-reduction strategies for municipalities and agencies in winter safety operations, says the savings can be significant. For example, she says the University of Minnesota, in its first year after employing sensible salting techniques such as calibrating salt spreaders and closely coordinating deicer application rates with road surface temperatures, cut its rock salt use by 40%, and its magnesium chloride use by 50%. In the process, she says, the university saved close to $55,000 in winter maintenance expenses.
Results such as these are gradually coaxing agencies nationwide to adopt a new perspective on winter safety operations. Specialized training in modernized deicing techniques has become an attractive option for many, and Fortin says she has provided certification training in salt reduction practices for over 3,000 winter maintenance workers, from plow drivers to managers. (See “Ice School“ in the January/February issue of Stormwater for other organizations providing training in sensible salting techniques.)
Lots of Change Needed
Although winter maintenance activities on roadways and highways account for the largest share of salt that enters the environment, deicing activities on parking lots, private roadways, and even paved walkways also rely heavily on snow and ice removal products containing chlorides.
The Cary Institute, a private, not-for-profit environmental research and education organization in Millbrook, NY, in a special report titled Road Salt: Moving Toward the Solution, states, “As much as 40% of salt use in some areas is from private users. Salt is not only used on public roads, but on parking lots and internal roads of commercial and industrial establishments, schools, churches and other nonprofit institutions, apartment complexes and other residences, and by individual home and small business owners.”
Fortin says that for a number of reasons, ranging from the costs of the initial investment in upgraded deicing equipment to liability concerns and traditional contract pricing arrangements (deicing services are often contracted by the ton), reaching out to the private sector with a science-based approach to salting can present some challenges.
A Little Less Salt
Martin Tirado, executive director of the Snow and Ice Management Association (SIMA), says his organization has begun to take an interest in the issue. Noting that SIMA approaches winter maintenance from a business perspective rather than from the perspective of an environmental advocate, Tirado observes, “There is over-application and overuse of salt as a deicer in the private market.”
In a survey of SIMA members asking them to quantify their salt use under given weather and roadway conditions, Tirado says, the responses covered “a tremendous range, from people putting on under 250 pounds per acre to people putting on over 1,000 pounds per acre.”
In view of this disparity, Tirado says that improving efficiency in the private sector through sensible salting could deliver both environmental benefits and significant cash savings to commercial snow and ice management contractors. He says innovative snow and ice removal techniques are gradually making inroads into the private market, and highly motivated small-scale operators are beginning to find success pairing the science of salting with a decent helping of entrepreneurial spirit.
Solutions for Ice
Although intuitively it might seem that heavy loads of salt would accelerate the process of clearing ice from pavement, applying extra salt beyond an optimal amount really does no good. Unlike melting ice through warming, where adding more heat obviously speeds things along, piling on extra salt beyond a certain concentration does nothing to speed up melting. That’s because, technically, salt does not melt ice; instead it prevents cold water from organizing itself into crystals.
As a mass of water approaches freezing, the individual molecules move closer and closer together. Eventually, they get close enough to one another that their electrical charges cause them to latch together to form a matrix, the solid crystals known as ice. As chemist Robert Syvret of the American Chemical Society’s Division of Fluorine Chemistry explains, freeze point depressants interrupt this crystallization process by introducing numerous particles into the water. These particles occupy enough space between the water molecules to keep them separated, so they can’t latch on to one another in the cold as the temperature drops.
“It is called freezing point depression; it is one of the four colligative properties,” says Syvret. “It’s not so important what the salt is, but rather, how many particles the salt contributes. Sodium chloride produces a sodium-plus and a chloride-minus ion–so that one molecule of sodium chloride produces two particles. Magnesium chloride will produce three. It will produce a magnesium-two-plus ion, and two chloride ions. So, all other things being equal, magnesium chloride will reduce the freezing point more than sodium chloride, because it is introducing more particles.”
Syvret says even sugar can lower the freezing point of water somewhat, but it’s much less effective because, unlike salts, sugar molecules don’t separate into a multiplicity of ions when dissolved in water.
Among the most commonplace substances on Earth, water and ice continue to display some puzzling characteristics yet to be fully explained by science. Nonetheless, science envisions the surface layers of ice at the freezing point as a somewhat disorderly latticework of molecules jostling about that do not necessarily conform to the grid-like arrangements of a typical crystal.
Syvret says this disorderly arrangement of molecules may facilitate the activity of salts in reducing the ice to liquid water. “Without being able to see at the atomic level, the presumption is, at the very top monolayer defining the piece of ice the molecules of salt get close enough to the top row of H2O molecules to begin the disruption process. As this process occurs, you get a very thin film of liquid water on top of the ice, which allows transport of the ions to the next level. It’s an ongoing, progressive process from the top down. It’s definitely a contact process.”
The cumulative effect, as more and more molecules break off the ice mass and are prevented from returning, is liquid water with salt in solution.
Uncharted Pavement
Tirado says there is not a great deal of data available today on optimal deicer application rates for treating parking lots, and he says what data are available have primarily been derived from roadway studies.
While Fortin concedes that the roadway application rate charts may continue to engender some controversy, Tirado points out that there are major differences between roads and parking lot pavements under freezing conditions. For example, he says vehicles in parking lots generally don’t drive as fast as on roadways; as a consequence, friction plays a smaller role in helping to melt ice and snow than it would in street traffic, a difference that could call for substantially different application rates.
However, Tirado predicts the information gaps will begin filling in when data become available from a study recently carried out by Morton Salt in conjunction with Michigan Technological University. In addition, he says Landscape Ontario and the University of Waterloo, Ontario, have initiated a three-year salt research project in conjunction with SIMA that he expects will also provide useful information on application rates.
In addition, winter operations on private properties differ from those in the public sector from a management perspective. While highway and municipal agencies generally have the capacity to standardize practices throughout their jurisdictions, parking areas and paved areas of private facilities in any community might be serviced by a myriad of winter maintenance contractors, large and small, each employing its own methods, preferred practices, and business models, adding a level of operational complexity to salt-reduction efforts in the private sector.
Before, and After, the Storm
Dean Outhouse heads operations for a company that provides snow and ice removal and winter safety maintenance for a number of properties in eastern New Hampshire, including commercial parking lots, and “zero-tolerance clients” such as liquor stores, district courts, and the state armory. He says over the 14 years he’s been in the business his practices have evolved, changing the way he looks at salt.
“We started out like everyone else, with a sand/salt mixture–three quarters sand, one quarter salt.” He says that 10 years ago, as he began to recognize the negative effects that sand could have on the environment, he decided to switch to “straight salt.”
That, he says, made his job easier: “You don’t have to put down as much material; you can do more properties with a hopper full of salt than you can with a hopper full of sand/salt mix.” Outhouse, who has a degree in business administration, says his success in breaking with the sand/salt tradition spurred his curiosity, and he began to imagine what else he might do to lessen the environmental footprint of his winter maintenance enterprise. “After investing three or four years in research, I decided to give liquids a try,” he says.
Noting the array of liquid deicers on the market, Outhouse says, “We chose to experiment with the one in particular, because it is the only one approved by the Department of Environmental Services. It’s a byproduct of the distillation of vodka and magnesium.”
One of the first things he learned implementing a liquids program was that “being different can be extremely expensive.” Rather than going out with “just a bag or two of product,” using the liquid required new investments in tanks for his trucks at a cost of $6,500 apiece. In addition, using liquid deicers on walkways required an investment in “backpack sprayers that other companies didn’t have–they’re a couple of hundred dollars.”
For Outhouse, the expense of using liquids tends to limit their use to seasonal contracts where clients pay a flat rate.
“Right now we’re in a recession; the economy is hard on us as far as liquid products,” he says. But he notes, “The advantage is you don’t have to treat as often, and that saves money.” He admits that sometimes it takes a bit of work to acquaint customers with the money-saving aspects of the deal. “It’s hard for someone to spend more money on something and use it less. They’re looking at the paper saying “˜This other guy is charging only $75. Why are you $100 when you’re going to use it less?'”
In addition to his liquids programs, Outhouse uses a product called Magic Salt, which he says has a working temperature of -35°F, in contrast to regular rock salt, which is effective only down to 18°F.
According to company literature, Magic Salt consists of rock salt granules coated with a patented blend of magnesium chloride and condensed distiller solubles. It is non-toxic and biodegradable and has a corrosion index lower than distilled water. It is similar in its application methods to rock salt, although Outhouse considers it much more efficient.
He says the coating allows the product to readily adhere to pavement, making it less likely to bounce and be lost to the roadside during application. He says this stickiness provides a residual effect that can last for days and prevents snow and ice from bonding to the pavement, allowing the product to maintain its effectiveness long after is first applied. As a bonus, Outhouse says the additive reduces corrosion to his equipment, enhancing its longevity and his profitability.
“As with anything, there are pros and cons,” says Outhouse of his workhorse product. “The restriction you have with it is that you’re only able to use it late January to February because you can’t put it down if the temperature is going to rise above 35 degrees; it can get slippery.” But that might be just right for the tough winters New Hampshire regularly dishes out.
Outhouse says he is not done looking for new deicing solutions. “This year we’re going to be trying liquid calcium on walkways,” he says. “We’re going to put it in the backpack sprayers, to spray it directly onto the pavement so it’s not getting tracked into the building.”
Sunny Snowy Colorado
About 12 years ago, Scott Zorno was working as a subcontractor for a small snow removal operation in Denver, CO, that he says didn’t use chemical deicers at all.
“All we did was move snow and let the sun take care of it–a reasonable thing to do,” he notes, in that part of Colorado, with more than 300 days of sunshine per year.
Later, Zorno moved “a little farther up in the mountains” to establish his own snow removal operation, Care Enterprises Snow and Ice Management. Now, with most of his work performed at over 8,500 feet, where snow from a single storm can pile up several feet deep, Zorno found getting down to bare pavement with just the plow and the sunshine could be a bit more challenging.
Zorno says he did a pretty good job keeping the lanes clear for his high-country clientele, with a “basic 1-ton pickup with a 9-foot plow on the front,” but there were some issues.
“We had customers who were saying, “˜Hey, the plowing is great, but it leaves a film and that film can get really icy; can you do something with it?’
“The first thing I did was to think about salt,” he says. However, Zorno says salt was not easy to come by at the time. It had begun to fall out of favor in the region. In fact, the Colorado Department of Transportation (CDOT) had quit using salt several years earlier, not so much because of water-quality concerns over chlorides, but rather in an attempt to address “brown smog” air pollution caused by particulates kicked up from the sand that was traditionally mixed in to enhance traction.
Zorno began to look for an alternative.
“We tried a dry mix of calcium chloride and magnesium chloride in little pellets, a little bit smaller than a BB. The effect was okay, but still not what I was looking for. So, I looked at what CDOT was using at the time and decided to investigate that.”
CDOT had switched to liquid magnesium chloride, which it sprayed on pavements in advance of storms as a pretreatment. Magnesium chloride received high marks from the department. At the conclusion of a three-year study using the liquid magnesium chloride for winter maintenance, CDOT found that, even very close to the highway, “the likelihood of environmental damage from magnesium chloride was much smaller than that of other factors related to road use and maintenance, including the pollution caused by vehicles and the use of salt and sand to promote traction in the winter.”
Zorno notes “several efficiencies from a business point of view” to using liquid magnesium chloride as a pretreatment. “You put it on the pavement before the storm hits, and it melts the snow from the bottom. It eliminates, or drastically reduces, the bonding of the snow to the pavement and makes snow plowing much more effective.”
He adds, “There may be storms or days where we don’t even have to put an application down after the storm, because that chemical is still down in the pores of that asphalt.” He observes, “Companies that don’t pretreat, they’ll plow, and they’ll salt, and the next day morning they’ll go back and salt again; we don’t have to do that.”
Balancing the Costs
Zorno says there are a variety of ways of comparing the costs of various deicing materials, emphasizing that their relative expense depends on how they are used.
On the East Coast, the cost per acre of treating with salt may appear relatively inexpensive, he says, but based on analyses he performed for the Snow and Ice Management Association, “It’s not that much less. It’s 35% less or 40% less, depending on whose numbers you use.”
He says if an operator can work pretreatment into a winter maintenance plan, the cost difference between salt and liquid deicers tends to balance out.
“If you’re going to pre-treat using salt, you have to do it in kind of a panic mode, right before the storm hits,” he says, and that means higher staffing costs. In addition, if a storm passes without delivering precipitation, “the granules can get stuck in the tires of the cars and get tracked away,” or salt granules scattered over a parking area can become a nuisance, getting “stuck on the feet of the people and tracked into the building,” muddling relations with the client.
On the other hand, Zorno says that when using a magnesium chloride liquid, he can pre-treat up to 48 hours before a storm. And, he notes, scheduling is simple. “I say, “˜Okay, it’s going to snow on Thursday,’ and if Tuesday night’s a good night for me personally, I’ll eat a quick dinner, let all the businesses close, then at 8:30 at night I go out, and by midnight I’ll be done with my spraying.”
If the storm passes without snow, Zorno says, thanks to the dry climate in the region, the magnesium chloride anti-icer “will have an on-the-ground life of approximately 10 days to two weeks.”
“We started on this on a commercial basis long before it was popular–I won’t say cutting edge, but pretty close.” Lately, he says, the Snow and Ice Management Association has made training and exposure to pretreatment options “available to guys who have never considered it,” and “more and more vendors are becoming interested.”
Zorno says he has delivered presentations at several SIMA conferences, “talking about liquids and how to use them, and why they are more efficient than salt. We touch on the green issue, which is certainly a force to be reckoned with.” But, he says, “From a business point of view, it is certainly not the driving force. What we say is, “˜It is much less harmful to the environment around the road.'”
Change took time and dedication for Zorno. “In the beginning, I worked on cultivating a relationship with a couple of the local CDOT drivers to learn what they did, how they put it down, and everything else. And then I cultivated a relationship with my supplier. I went to a couple of their trainings for municipals and sat in as the lone commercial operator.”
But he said one of the best teachers is experience–his own and that of others. “The biggest thing is to read the literature, and trial and error. Find somebody else who uses it and try to figure if their use methods and climate are similar to where you are.”
Evolving Strategies to Reduce Risk
As with all deicing products, liquid deicers pose some risk of environmental impacts, Zorno says, and he tries to keep the risks to a minimum through a few simple management practices.
“We try to engineer where our snow piles go, so as they melt they have lots of room before they get into anything resembling a watershed.”
He adds that one of the most important measures in mitigating the environmental impact of winter maintenance “is not being cavalier about application rates.” Zorno says the costs of the liquid deicers enforce a certain discipline that regard. “Liquids are not real cheap; they come in about a buck and a half per gallon. You don’t want to be putting it on frivolously, and you don’t want to be over-applying.”
Tirado says SIMA’s involvement in chloride reduction will continue to evolve.
“It’s been a little reactive in the sense that there have been certain areas of the country, and certain municipalities, that have already created restrictions or are in the initial stages of discussing restrictions on the amount of salt that can be applied as a deicer. The second half of it is the Green Building movement. Property owners and managers are looking at having more green and sustainable work being done on their properties. That hasn’t really been reflected in a direct way in snow and ice contractors, but it will be, and there are some cases where we’re hearing form our members that property managers are requesting minimal usage of chlorides or rock salt being used as a deicer.”
