Despite water-quality concerns, sodium chloride is still the most affordable and widely used substance on winter roads.

By Janis Keating

Salt in its common form as sodium chloride: Can’t live with it, can’t live without it. For centuries, it’s been the most popular food condiment (can you imagine French fries without salt?). Yet for those with hypertension, it’s one of the first items banned from the diet. For decades, salt has served as the major substance used for road deicing, yet it damages motor vehicles, bridges, and roads. Salt splashed from streets into lawns and gardens kills the vegetation it hits; indeed, when trying to remove tree stumps, homeowners are told, "Pour table salt on it."

Sodium chloride in runoff from road deicing operations can also dramatically change salinity levels and the chemical composition of receiving waters. Deicing salt is considered a possible pollutant under the National Pollutant Discharge Elimination System (NPDES).

A 1998 study commissioned by the Insurance Corporation of British Columbia examined the environmental effects of salt and various liquid deicers. The final report by Levelton Engineering of Vancouver recommended additional field testing, but concluded that all other deicing chemicals considered have fewer negative environmental impacts than sodium chloride. None of the alternatives was clearly shown to have fewer impacts than the others, however.

How is this shaking out in the real world? According to the cities contacted for this article, by and large, salt is still on the table.

Less Salt on the Potato State

"We try to be as environmentally friendly as we can be," states Errol Morgan, manager of maintenance and operations for Ada County Highway District in Boise, ID. "We have mirror sensors on our trucks to get road temperatures, so we know when and where to treat. We use a minimum of solar salt, and some sand, mostly for abrasive [tire traction]. We put about 5% of solar salt in our sand to keep it from freezing."

Ada County also uses magnesium chloride (MgCl₂), treated with an anticorrosion additive, as an anti-icing tool that crews apply before an impending storm. "If it turns out to be a minor storm, the mag chloride will melt the snow and ice and dissipate it," Morgan explains. "If the storm dilutes the chemical, it creates slush instead of ice, but this gives us time to get the sanders out there."

Morgan points out that Boise’s climate sometimes does the street clearing for them. "The norm around here, a winter storm is followed by a warming trend–rain or warmer weather. If cold weather continues and we get more than 3 inches of snow, we’ll start plowing, but we don’t post-treat [with magnesium chloride] to fight ice. We experimented with calcium chloride. The window for temperatures [in which it can be used] is larger, but it dilutes faster than mag chloride and stops working. Mag chloride takes more time to dilute."

Boise has separate stormwater and sewer systems, and the sand the highway crews drop can be a problem for both. "We don’t have as many sediment traps as we’d like, but we’re working on it," Morgan says. "In spring we vacuum the sand; we catch all we can."

Salt Air in the Windy City

Between lake-effect snow and commonly occurring subzero temperatures, Chicago often battles with winter, and salt is the Streets and Sanitation Department’s usual weapon of choice.

"The city usually uses salt; in colder temperatures, calcium chloride pretreated salt," points out Andrea Gibson, the department’s program director for legislation and policy. "We have been testing alternates. In 1998 we received a $100,000 grant from the Federal Highway Administration to test a calcium-magnesium-potassium acetate blend–CMAK. It worked OK. It’s an anti-icer put down ahead of the storm. Of course, it’s hard to guess; if it turns out there’s no snowstorm, by getting out ahead of time we’d perhaps waste the CMAK. We didn’t like the change it required in our operations. Our usual procedure is to get out there with the salt when the storm starts, not pretreat."

Some cities pretreat quick-to-freeze overpasses and bridges; Chicago keeps watch on these structures through use of embedded temperature sensors. As changing temperatures warrant, more or less salt goes down. Because multi-inch snowfalls are common, streets often require plowing as well.

Chicago also clears certain city sidewalks; some have been testing grounds for other deicing materials. "We tried Ice Slicer–a salt with naturally occurring acetates–at the State Street Mall to preserve the sidewalks, which is an expensive walkway," Gibson reports. "We had success there with it. Ice Slicer was definitely more expensive than salt but cheaper than CMAK. We’d like to try it on some street routes. We wanted to try Ice Beeter, but it comes out very red. People were tracking it in; it stained things."

Gibson’s main role in the department involved acquiring funding for more alternative deicers, an ongoing program. "We would like to eventually use something more environmentally friendly that also fits with our operations and doesn’t threaten public safety. Public safety is our number-one concern."

Seven Salted Hills

Nestled in the Ohio Valley, Cincinnati sits on a series of hills that, in winter, could be a driver’s nightmare if not for the city’s efforts.

"We use salt exclusively, about 30,000 tons in an average year," says Bob Townsend, supervisor of the city’s Highway Maintenance Division. "Years ago, in the 1930s and ’40s, the city used crushed cinders and sand, but that caused lost revenue and taxes because people couldn’t get out to work and shop."

Highway Maintenance is responsible for 2,835 lane-miles of road within the city limits. Indiana, Kentucky, and Ohio maintain the five interstate highways that feed, intersect, or surround the Greater Cincinnati area.

The city’s streets often don’t require plowing. "We don’t scrape unless we have to," Townsend states. "Usually only if it’s over 2 inches. Sometimes you can just melt the snow. Plowing can cause more problems–potholes, windrows, inlets built up with ice, which sometimes gets into the streets and freezes. When the plow blades are dropped, they’re set to 1 inch."

Cincinnati pretreats its roadways, a practice on the increase over the past few years. Weather stations located around the city read road temperatures to help crews determine where work is most needed. "We try to get a fine layer of salt down first," explains Townsend. "It keeps snow from bonding to the roadways. When temperatures get low, we’ll add liquid calcium chloride. We used to leave ice control barrels filled with salt at locations around the city–mostly on hills with more than a 6% grade. Property owners would put out that salt. We cut that way back this year because we found some citizens were using the salt on their own properties instead of on the streets."

Alternatives to salt, such as the various "M-50" products (liquids created from byproducts of agricultural, beer, and distilled alcohols processing, combined with magnesium chloride), have been tested. "We’re always looking for something new," Townsend says. "We’ve done testing evaluation on some M-50 products; we weren’t real happy with it. We’re just now testing Ice Slicer. But salt is still the standard thing."

Denver Passes the Salt

"We don’t use salt at all," says Norman Shaw, Denver, CO’s paving superintendent. "Not sand either. We had an air-quality problem years ago–PM₁₀ problems–with particle-size air-quality dust control. Sand was mostly the problem; we were adding too much."

Denver, which in recent years combined city and county governments, maintains 1,700 lane-miles. With its high elevation, the city often experiences plowable snow. "We’ll plow if we have buildup," Shaw says. "But we mostly pretreat with Ice Slicer or Caliber M1000, which we use in downtown areas. M1000 is made from corn products, so it does have an aroma but minimal tracking."

Lincoln’s Shrinking Salt Usage

By substituting sand or adding a variety of liquid products, Nebraska’s capital city now uses less salt for its deicing projects. "We use chemicals or salt only on arterial streets and emergency and bus routes because of environmental concerns–both for cars and grass–plus we want to keep more [chemicals] out of the stormwater systems," relates Bill Nass, Lincoln’s maintenance coordinator for street operations. "In the residential areas, we’ll plow after 3 or 4 inches, then sand the icy spots. There are rare exceptions; for instance, if the police department calls us about a bad intersection for accidents, then we will salt that area."

Pretreatment, whether for the salt or for the streets themselves, is a big part of Lincoln’s standard procedure. "We spray M-50 on our salt to get it to work in lower temperatures," Nass explains. "We spray M80 directly on streets as a pretreatment. It will work up to week or 10 days. We try to use it mostly on bridges and overpasses–things that freeze first–and also roads with grades or high-accident intersections. We do also use some calcium chloride on emergency snow routes or main arterials when the temperatures are subzero."

Nass points out that many "M" products are brown-colored and have a molasses smell. That isn’t always a drawback, however. "M2000 is clear, but then you couldn’t see if you missed a spot."

"M-50 does add to costs but has some other benefits," Nass adds. "It won’t freeze in chunks; the spreader can throw the right amount. It’s easier on our equipment. They tell you that you can use as much as 50% less salt with M-50; we’re using 35% to 40% less salt now."

Of all the products used, sand seems to collect the most citizen complaints. "We use a lot of sand and get a few complaints when we send street sweepers out," Nass notes. "Mostly we get complaints when we don’t put it down.

"We’ve just started testing Ice Slicer [from P&R Tank Lines of Baltimore, Maryland], a noncorrosive pellet–a mined salt," he continues. "They say it’s less corrosive than water. We monitor the test area. It works even at a very cold temperature, so you don’t have to use sand. The pellet makes its own gripping power to the street."

Runoff entering Lincoln’s stormwater system, which is separate from the sewers, is not treated. "It drains to local creeks–one is Salt Creek, where they used to mine salt. Salt is in our soils," Nass observes.

Don’t Salt the Cranberries!

Although other parts of the state might use more rock salt, the Massachusetts Highway Department uses low salt around certain state watersheds.

"We’ve done this for a number of years," reports Doug Cope, public affairs director for MassHighway. "The public seems generally pleased. We’ve had no bad reaction about the low-salt areas.

"One thousand lane-miles of roadway are designated as low-salt areas, where we use a reduced 50/50 mix of salt and sand. Sand also can dry out the roadway, so it doesn’t reice. All of Cape Cod’s Route 6, the Mid-Cape Highway, is designated as a low-salt area, as are roads around the Quabbin Reservoir, which is Boston’s primary water source. We don’t treat the salt with deicer either."

Because these road sections might not have the traction others do, motorists must play an important part in keeping the areas safe. "In these areas, we put up signs to advise motorists to drive accordingly," Cope points out. "On other roadways, we use a calcium-chloride spray–32% liquid calcium to water. We also use magnesium acetate, CMA. Along one section of Route 25 in the Plymouth area near the cranberry bogs, we use magnesium acetate to minimize salt usage."

Cope reports that before projected storms, MassHighway pretreats bridges and ramps. The state also "pre-stages," meaning that road crews are posted around the area, ready to roll at a moment’s notice. Although the crews mainly treat the roadways, depending on conditions, at times their plows are dropped before 3 in. of accumulation.

Remarks Cope, "With almost 4,000 pieces of equipment working on 12,600 total lane-miles, MassHighway is dedicated to keeping roadways clear."

Minneapolis Melts

Despite their fondness for ice fishing, Minnesotans don’t like ice driving, and Minneapolis uses a salt/sand mixture to deice its streets because it finds deicers too costly. Near any type of lake, however, highway crews don’t use salt, just sand; the sanding trucks also include underbody plows in the event that snow piles up. (Plowing in the city usually starts at 2 in. of accumulation.)

Stormwater and sewers are virtually all separate, according to Richard Trapp, a Sewer Department Office support specialist. "Stormwater drains into the Mississippi, and we don’t usually test the stormwater–only if we suspect a chemical spill." The department has no concerns about deicing salt in the system. "We actually throw salt into catch basins to clear them up," Trapp points out.

Shopping Alternatives on Maine Streets

"We don’t have too many worries about salt in streams," says Kevin Noyes of Portland, ME’s Department of Public Works. "The Fore River is 99% salt water anyhow." Nevertheless, Portland has been using more alternative deicers and less salt in the past few years. "We use rock salt and treat it with calcium chloride and M-50. We also use a salt-and-sand mix. We’re trying to use more M-50. It’s less corrosive and less harmful to vegetation, and we anticipate EPA restrictions on salt."

Although his M-50 supplies cost $1/gal. versus salt’s $30/ton, Noyes still sees advantages: "If I put M-50 in, I need less salt. An area that might have taken 500 pounds of salt only uses 200 pounds of M-50—added salt."

At present, Noyes uses about 700 gal. of M-50 per storm while treating Portland’s 13 mi. of city streets, but he says, "I’d like to be to 2,000 gallons per storm by 2003. We’re very happy with its results. It doesn’t hurt trees, and drivers find this much better. There are less accidents on it. On the Deering Avenue hill, which has a 16% grade, you used to see accidents all the time–not anymore."

M-50 also saves Noyes some complaint-filled phone calls. "Most complaints come when we use sand and salt," he reports. "Most catch basins are a combined [sewer and water] system. It kills the bugs [beneficial bacteria] in treatment plants, so we have to let them know we are using sand and salt, so they can compensate for it. But M-50 doesn’t seem to do that."

For the most precise deicing, most of Portland’s plow trucks run with computerized spreader systems. After they receive Noyes’ temperature readings, drivers specify the amount of material to be spread with the touch of a button. "I use a hand-held laser that tells me what the ground temperature is," describes Noyes. "Then I tell the trucks where to salt. We pretreat the materials coming out of the trucks and pretreat our roads with M-50 up to seven hours before the storm. If the storm drops 1 to 2 inches, we don’t scrape; that causes a lot of refreeze."

Deicing the Great White North

Toronto's snow-melting machines melt up to 136 tonnes (150 tons) of snow per hour.

Although USEPA has no jurisdiction over what Toronto does, the city must answer to its citizens and Environment Canada, and there are concerns that the city’s stormwater drains into the city’s drinking-water source, Lake Ontario.

"Environment Canada is thinking of naming salt as a toxic substance," Toronto Sewers and Drains’ Bill Chapman says. "People will be up in arms! [City] engineers want it named a controlled substance."

In response to concerns about salt, Toronto made a variety of changes to its snow removal operations. Crews now start plowing at a lower accumulation; on main arteries, plows go down at 5 cm (2 in.) instead of 8 cm (around 3 in.). On local roads, plowing now starts at 8 cm instead of 10. All salt trucks have computer controls for rate and spread, so there’s less waste.

Most of Toronto’s sewers and stormwater systems are separate. For areas with combined systems, however, the snow-melting machines are put to work.

"The auger picks up snow, puts it into the tank of hot water–there’s a gas burner inside the truck–melts the snow, then puts the water back onto streets, and it goes into the stormwater drains," explains Gary Welsh, Toronto’s director of transportation services. "We have five units, costing about $1 million apiece. The first unit was put in operation around 1974 or ’75.

"The machine’s original idea came from the Toronto city staff," Welsh continues. "The machines are now made in Nova Scotia by Trecan Combustion Limited. We use the melters in the city sectors with combined sewers and stormwater, approximately 20% of the city."

Sometimes the snow-melting machine’s elegantly simple idea can get complicated. "We have to shut the melter down after 12 to 16 hours and clean it out because we get lots of street grit into the machine," Welsh points out. "The grit is then taken to an appropriate dump site. Of course, sometimes the melters end up sitting idle because there’s not enough snow for them to work on."

For the remaining 80% of the city, Transportation Services uses regular plows and then salts the main roads to deter ice. "We then determine what’s needed to keep local roads safe, which depends on the forecast. If temperatures are going down, we use salt and a limited amount of sand," Welsh explains. "Any salt that does get into the combined sewer ends up in a treatment plant."

Welsh, part of a Canada-wide committee on the proper use of salt, makes sure Toronto’s snow removal crews are trained on salt’s use so they don’t put down too much. "We’re using the latest salt-spreading computerized equipment," he reports. "In the next couple months we’ll be installing RWIS [Road Weather Information Systems]. Not only will we put it on the streets, but we’ll also get some mobile units. Right now we only use rock salt–we didn’t want to use any liquids until we have the RWIS in place–then we will look into liquid deicing. Over the years we used some MAGic with mixed results and limited success. You have to be careful pretreating with liquids; if the temperature is not right, it can make the road worse."

Instead of pretreating, Toronto pre-stages. "We load trucks and send them to seven or eight particular locations around the city to wait. Operators are there 24 hours a day [during storm times], and they’re given five minutes to get their trucks out on the road."

Salt Substitutes

If not salt, what can road crews use to clear streets? A variety of products, which have a wide range of efficacy and costs, are available. (Sample prices quoted in Table 1 are calculated from 22-ton truckload rates.)

Table 1. Deicing Alternatives

 Comparing the cost of these formulations to rock salt’s $30-$40/ton, it’s no wonder that budget-conscious cities cling to the old standby. As many of the preceding sources attest, however, when adding certain amounts of these chemicals to salt, less salt needs to be used, therefore causing a little less pollution.

The search continues for cost-effective nonsalt deicers. The University of Minnesota and the Federal Highway Administration report that CMA produced from cheese whey can have an equal or slightly better ice penetration rate than that of commercial CMA. It’s estimated that cheese-whey CMA can be produced at a production cost of $200-$232/ton, much less than commercial CMA.

The "M" Word

Ice Beeter M-50 applied to snow

Ice Beeter is going through ODOT testing

"M" products have also made inroads as an alternate deicer. Ice Ban, produced by Natural Solutions Corporation of Chesapeake, VA, was one of the first M-50 products. "It had its birth in the ‘M’ products, but since then it has evolved," says Mike Klansek of Natural Solutions. "It’s 97% less corrosive to metals than sodium chloride. It meets PNS [Pacific Northwest Snowfighters Association] and AASHTO [American Association of State Highway and Transportation Officials] standards. Some of our original stuff was black and syrupy, like most of the so-called ‘M’ products, and now our Ice Ban Ultra and Performance Plus are clear or near clear." As with some other products, Ice Ban is often used to pretreat salt, which reduces the amount of salt needed and allows it to melt ice at lower temperatures than sodium chloride alone; Ice Ban claims its products are effective to -40ºF.

Portland’s Kevin Noyes gets his M-50 product from Seaco (Sears Oil Company) of Rome, NY; the product often goes under the trade name of "MAGic." Explains Noyes, "It’s made from stuff they used to pay to get rid of. Someone thought of doing something with it, and now it’s so refined, it’s like using liquid calcium."

"There are different patents on different formulations. We own the patent on the distillers’ version of M-50," says Seaco President Dave Wood. "The active ingredients in all versions are the carbohydrates, which lower the freeze point of the salt they’re added to. It will change magnesium chloride’s freezing point, allowing almost 20% more melting time."

Wood explains the two common ways to use his product: "If you add 8 gallons of M-50 per ton of salt, you can use 30% to 40% less salt. At 17 to 18° , salt won’t work anymore; with M-50, salt will work down to 0º. You also won’t need sand, which can cost about $900 a ton to use, if you count the cleanup costs.

"You can also use M-50 by itself," he continues. "If you apply it before a storm, it’s like a Teflon treatment; the snow and ice won’t stick. It’s most effective in ‘black ice’ situations."

Wood claims studies have shown Seaco’s M-50 makes almost no impact in groundwater supplies. "This creates very little phosphate trail. The chloride decomposes; the rest is absorbed as plant food."

Because of the product’s heavy liquid weight, shipping the product cross-country would price it out of range for most users; therefore, M-50 producers tend to be regional distributors. Seaco, for example, ships mostly to the Mid-Atlantic and New England states.

Mountain Products & Equipment Inc. in Georgetown, KY, ships within the central part of the nation. Holder of the patent for M-50 created using desugared beet molasses, Mountain Products & Equipment calls its product Ice Beeter. "We were one of the original distributors for the original Ice Ban," states Chris Harrison, logistics administrator. "About a year into that we hooked up with a recycled goods dealer. Todd Bloomer, our president, is a chemist. When he learned about it, he thought a beet product would be better because it blends with many other chlorides, not just magnesium chloride."

Similar to the other M-50 products, Ice Beeter claims to be less corrosive than distilled water. Harrison points out that the product to date has produced no fish kill in toxicity tests. "For the tests, we finally had to dump the whole beet sample in, and yet still no fish kill."

The Ohio Department of Transportation (ODOT) is testing Ice Beeter in the Washington Court House/Fayette County area. "They treated 5,000 tons of salt with Ice Beeter," Harrison reports. "The cost of treatment added about $6 a ton to their salt cost, but they’ve been able to eliminate about 30% of their salt usage. They’ve had success thus far with Ice Beeter on their roads, although they’ve had to convince operators to cut back on the salt."

In response to Chicago’s experience of Ice Beeter "painting the town red," Harrison states, "Our current product is made from sugar beets; two years ago it was made from corn. We did get comments about it being ‘brown’ until it’s diluted away. We tried the product on white carpet. In all of our experience it does not stain, but it does track. You get white tracking with salt; it’s white but corrosive. Ice Beeter is water soluble and noncorrosive." The product has not been tested on all materials. "We have not tested Ice Beeter on brick or any other material besides concrete and asphalt," she points out. "Possibly dust from bricks was picked up, and that’s what tracked.

"The University of Pittsburgh is trying it out," Harrison continues. "They told us it tracks in, but thus far they are happy with the results of the product. Ice Beeter has prevented some small accumulation of snow too, although it was not designed for that."

Usually sold by the 4,500-gal. truckload or the 20,000-gal. railcar, Ice Beeter costs between $0.70 and $0.85/gal., or $1.00-$1.25/gal. in smaller quantities.

The Push for Salt-Free

To date, salinity levels in American waterways are not causing alarm; however, as most cities’ stormwater remains untreated, EPA will likely keep monitoring groundwater and surface waters for any changes caused by salt or other chemicals.

A 1991 study by the US Transportation Research Board (Highway Deicing: Comparing Salt and Calcium Magnesium Acetate, available at www.nas.edu/trb/publications/sr235.html) admitted that salt had some detrimental effect on vegetation, but the main thrust of the report involved comparing costs, both direct and indirect, of deicing salt’s use.

Other organizations also monitor riverways. ORSANCO, the Ohio River Valley Water Sanitation Commission (www.orsanco.org/), was established in 1948 to control and abate pollution in the Ohio River Basin. An interstate commission, ORSANCO represents the federal government and eight states (Illinois, Indiana, Kentucky, New York, Ohio, Pennsylvania, Virginia, and West Virginia).

"We test for chlorides," says Jason Heath, ORSANCO’s manager of monitoring assessment and standard programs. "The standard for chlorides is 250 milligrams per liter. Beyond that, it can affect human health. The river’s winter 1999 ratings were in the 20s and 40s–nowhere close to the standard. The Ohio River has a huge dilution capacity."

Environment Canada remains more cautious. In an August 2000 report (www.ec.gc.ca/cceb1/eng/public/road_salts.html), the agency concluded that "road salts are toxic to the environment." Although the report projected action by the end of 2000, a final decision has been delayed until May.

"RiverSides wants the environment minister to act on road salt," says Kevin Mercer, executive director of the RiverSides Stewardship Alliance, a Canadian nonprofit water-quality organization in Toronto. "Chloride levels of 35,000 milligrams per liter have been monitored in storm-sewer discharge pipes at the confluence of two major highways. You could pickle fish!" Groundwater contamination is also a concern. "Fifty percent of road salt doesn’t end up in surface waters–that means it’s getting into the groundwater table. We are poisoning our groundwater table with salt. In the winter, groundwater salt levels can rise to 1,000 milligrams per kiloliter."

Mercer acknowledges, however, that the public safety issue might cause the government to set a frightening precedent of classifying road salts as environmental toxins and yet not regulating them because of concern for traffic safety–a concern he dismisses. "Our position is that salt is an excuse for bad driving habits. It doesn’t stop accidents. It just gives people an excuse to drive poorly.

"We’re trying to educate the public," he continues. "Not only is salt toxic to the environment, but there are also high societal costs: for example, corrosive groundwater salt is rotting some buildings at their foundations."

RiverSides is also concerned with contamination of surface waters; specifically, the Great Lakes. Not only does Toronto draw its water from Lake Ontario, but many parts of the United States also draw water from the Great Lakes.

"Most of the Great Lakes’ waters come from rain; they’re the largest puddle in the world. Their waters are all outflow," Mercer points out. "Twelve percent of the world’s fresh water is sitting there in the Great Lakes. We have to take care of it."

Janis Keating is a frequent contributor to environmental and horticultural magazines.

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