Cutting the Salt in Winter Road Maintenance

The Politics of Over-Salting

Entire floors of the Port Authority bus terminal on lock down for crowd control. Kids with special needs trapped on school buses for up to ten hours. Stranded motorists abandoning their cars and setting out on foot across the George Washington Bridge in a driving snow. New Yorkers are no strangers to transit nightmares, but the city’s lukewarm response to last month’s pre-winter storm may go down as one its most epic winter fails.

But it wasn’t the first time New Yorkers’ ire had been piqued by a winter storm. In 1969, many New Yorkers called for Mayor John V. Lindsay to step down after a blizzard took city agencies by surprise and paralyzed the city for three days. More recently, in 2010 a “snowpocalypse” dumped some 20 inches of snow across the metropolitan area and brought Gotham to a grinding halt. In the aftermath, Mayor Michael Bloomberg took heat both from citizens and the press about the city’s delinquent cleanup efforts, which grounded some New Yorkers for days. To prevent any further embarrassments, the Bloomberg administration promised to double down on the city’s response to subsequent winter storms.

Severe weather can be a trial by fire for politicians, and no city official wants to be in the firing line after a mass transit mutiny. Despite the city’s failure to anticipate last month’s storm, when forecasts rapidly escalated from an inch or so of wintry mix to six inches of snow, the city’s response to winter weather has remained aggressive since Bloomberg’s time in office. This is especially true when it comes to the use of road salt, today’s weapon of choice in the battle with Old Man Winter.

Road salt is an inexpensive and effective deicer, and the amount of it poured onto roads nationwide has skyrocketed over recent years. But scientists have found that road salt comes with a significant environmental price: it can pollute freshwater resources, damage ecosystems and pose threats to human health. And it isn’t just harmful to the environment: salt causes an estimated $5 billion in corrosion damage every year in the U.S.

As the capital and environmental costs of road salt continue to mount, has the time come to ask whether we’re putting too much of it on our streets?

Snow and Ice Removal in New York

With an estimated value of $1.9 billion in annual sales and use, salt is big business in the United States. And that goes double for the Empire State: New York is both the third largest producer and top consumer of rock salt in the U.S. The nation’s largest and deepest salt mines are both located in the Finger Lakes region of upstate New York.

In New York City, the Department of Sanitation (DSNY) oversees the city’s sweeping snow and ice removal operations, which is no small challenge. Snow removal agencies must react to up-to-the-minute forecasts, precipitation and pavement temperatures can dictate different deicing strategies, and a fleet of vehicles must be coordinated to ensure that thousands of miles of roads are cleared. DSNY maintains 42 sheds that store mountains of salt for use on winter roads and has some 695 salt spreaders and 1,600 collection trucks outfitted with plows at its disposal when the flakes begin to fall.

Tons of Road Salt Per Inch of Snow, DSNY

When weighted per inch of snow, DSNY’s base response results in very high salt use rates when only an inch or less of snow falls. On two occasions only a trace amount of snow was reported at Central Park. [Hover over chart for numbers]

During the winters of 2016-18, DSNY used an average of 20,124 tons of salt during storms with 2 inches or less of snow accumulation. This works out to more than a ton of salt per lane mile, a high application rate even by the guidelines of The Salt Institute, a trade association that advocates for “the many benefits of salt.” A similar amount of salt was used even during smaller storms, resulting in very high usage when weighted per inch of snow. The tons of salt used per inch of snow also generally trends lower for larger storms, suggesting that lower application rates overall could prove effective. On two occasions DSNY salted when only a trace of snow was recorded in Central Park, indicating that an opportunity may exist to better adapt to changing forecasts. (DSNY did not respond to requests for comments.)

Tons of Road Salt By Agency, Snow Adjusted

When adjusted for snowfall, DSNY uses 37 percent more road salt than NYS DOT. Both DSNY and NYS DOT use significantly more salt than Connecticut DOT. [Hover over chart for numbers]

But how does NYC’s road salt use stack up against other locales? At first glance it may seem comparable to other regional agencies; DSNY used 21.5 tons of salt per lane mile from 2016-18, while the New York State DOT used 23.1 tons per lane mile from 2010-16. However, Central Park received just 64 percent of the total amount of snow that Albany did during those time periods. When adjusted for snowfall, DSNY’s figure jumps to 33.6 tons per lane mile, 37 percent higher than NYS DOT’s annual total. Both DSNY and NYS DOT use significantly more salt on their roads than Connecticut DOT, which spread just 15.7 snow adjusted tons per lane mile from 2009-14.

From 2016-18, DSNY used an average of 407,884 tons of salt per winter season – about 95 pounds for every New Yorker. And clearing the fluffy white stuff doesn’t come cheap: it costs NYC an estimated $1.8 million to remove each inch of snow from its streets, and in 2017-18, the city budgeted $84 million for snow removal alone.

The price of bulk rock salt has soared in recent years, and this winter may prove to be the most expensive yet for road salt expenditures.

Putting Roads on a Low Salt Diet

As the threats that road salt poses to the environment become clear, many states and municipalities are implementing new strategies and techniques in an effort to put their roads on a low salt diet. One basic step is to install application regulators on spreading vehicles, which control the amount of salt being dispersed onto streets. After retrofitting its trucks with application regulators in 2009, the town of East Fishkill, NY was able to cut its salt use by 3,483 tons and save $243,810 in the first year.

Another way to reduce salt use is to use liquid salt brine, which is an effective anti-icing agent. Brine can be spread more evenly than rock salt, and it begins to work immediately because the salt is already in a solution. Switching to brine can reduce salt use by as much as 70 percent, and the initial equipment expenses are often recouped within the first two years.

DSNY Vehicle Traffic by New York City Block, December 9-10, 2017
This map shows the number of times a DSNY snow clearing vehicle visited each block of New York City from December 9-10, 2017. During this storm, a total of 4.6 inches of snow fell in Central Park and 40,000 tons of salt were spread on NYC streets. Snow and ice removal operations also come with a significant carbon footprint: the number of visits to each block ranged from one on some local streets to 87 on high traffic roads. (view large version of map)

New technologies are also helping cut the salt. “Smart snowplows” are equipped with GPS and systems that can gauge pavement temperature, the amount of residual salt from previous applications, and even the presence of ice and the amount of friction on the road. Combined with sophisticated control of plow blades and application rates, these high-tech systems can help operators de-ice roads while using less chemicals. In the lab, researchers have synthesized molecules that can extract chloride from water and worked to develop “ice-free” concretes that resist bonding with snow and ice. Some municipalities have even tried using more eco-friendly deicing compounds such as beet juice, sugarcane molasses and cheese brine on their roads.

Legislators are also beginning to recognize the downsides of road salt: a bill introduced by New York City Council Member Helen K. Rosenthal in 2015 sought to replace salt with alternative deicers on the city’s streets and sidewalks. The bill was left on the table at the end of the 2017 legislative session.

Taking Winter Road Maintenance With a Grain of Salt

In response to NYC’s most recent struggle with snow, city officials have once again promised to respond more aggressively to winter storms. In a statement released after the storm, DSNY cited climate change as contributing to a long-term trend of more frequent, intense and unpredictable storms in New York. In response, the department plans to increase pre-treatement of roadways, admitting that in some cases this policy will result in salt on the streets even when little or no snow accumulates. This may placate some New Yorkers, but it’s an expensive step backward for sustainability and contrary to what many other cities are striving to do: reduce the amount of salt spread on roads.

There’s no silver bullet when it comes to winter road maintenance, but improved techniques and policies can keep roads safe while reducing the amount of salt used on them. “It really can be a win-win for everybody involved,” says Rensselaer Polytechnic Institute biologist Rick Relyea. “It’s not really about posing the health of ecosystems against public safety.”

Research, new technologies and modernized operations are already making progress in reducing the amount of salt on roads and therefore in the environment. But perhaps the biggest challenge will be to change a mindset that’s become second nature over the past 80 years: that when it snows you salt.

Part One: “How Road Salt Harms the Environment“

Sources

• NYC OpenData: DSNY Salt Usage, DSNY PlowNYC Data
• NOAA: Climate Data Online