By Grainger Editorial Staff 11/17/23
When winter snow arrives, the road salt comes out.
Salt, or sodium chloride, has been used to help keep highways clear in the winter for almost as long highways have been around. New Hampshire is credited as the pioneer, spreading the chemical on its roads beginning in 1938.
By lowering the freezing point of water, salt causes snow and ice to melt, making travel easier and safer. It’s no surprise that a tremendous amount of salt is used for deicing today. In fact, more than 40% of the salt used in the U.S. is spread on roads and parking surfaces. It amounts to more than 10 times as much salt as is used in food production.
But while road salt is helpful for drivers and pedestrians, it can harm the environment and degrade infrastructure. The chloride in salt is toxic to aquatic life and vegetation, and there’s no natural process that breaks it down to prevent it from building up to dangerous levels. Salt also corrodes buildings, vehicles, roads and other infrastructure. Estimates have placed the cost of road-salt-driven corrosion in the billions or even tens of billions of dollars per year.
And the consequences of salt-driven infrastructure damage can be even worse. According to the American Chemical Society, road salt was a key element of the Flint, Michigan, water crisis. In 2014, the city switched to a water supply that had an unusually high concentration of chloride from road salt runoff. Because the city's water plant wasn't treating the water to control corrosion, the chloride quickly damaged old pipes, allowing extremely toxic levels of lead to leach into the municipal water.
That’s why scientists are concerned that the world’s waterways and soils are getting much saltier. We're always building new roads and surfaces that need to be deiced, and research suggests that people are also using more salt to do the same job in the areas they need to clear.
And while you might think that the majority of environmental road salt comes from deicing highways and other major roads, that’s not necessarily true. In studies of chloride-impacted waterways, the single largest source of road salt was private roads and parking lots.
This means that using road salt responsibly can make a real difference, even if you’re only clearing a parking lot. You can limit the damage caused by road salt runoff – to the environment and to your business infrastructure – while keeping pavements and walkways safe for drivers and pedestrians.
The first thing to know is that you probably need less road salt than you think. One rule of thumb is that when you spread the salt, the grains should be about three inches apart. Another rule of thumb is to use one cup to one-and-a-half cups of road salt per every 250 square feet, which is about the size of two parking spaces.
Here are some more tips to use road salt in a way that limits the damage to infrastructure and the environment:
The Smart Salt Collaborative has published charts that include recommendations for road salt and brine amounts based on pavement temperature:
|Pavement Temperature||Amt. of Rock Salt per 1,000 SF|
|28 F to 32 F||3 pounds|
|23 F to 28 F||4.5 pounds|
|15 F to 23 F||6.5 pounds|
|Pavement Temperature||Amt. of 23.3% Salt Brine per 1,000 SF|
|28 F to 32 F||0.7 gallons in light snow, 1 gallon in medium snow*|
|23 F to 28 F||1 gallon in light snow, 1.3 gallons in medium snow*|
|15 F to 23 F||1.3 gallons in light snow, not recommended in medium snow*|
* Light snow = less than one-half inch per hour. Medium snow = between one-half inch and one inch per hour.
Commercial ice melt products typically blend road salt, or sodium chloride, with other one or more additional chemicals that promote melting, including calcium chloride, magnesium chloride, potassium chloride and calcium magnesium acetate. The biggest advantage of these products is that they're effective at lower temperatures than rock salt. Some ice melts also include corrosion inhibitors that can help limit the damage caused by the chloride they release.
The USGS divides US states into three tiers based on salt usage. The “salt belt” states that use the most are Connecticut, Delaware, Iowa, Illinois, Indiana, Kentucky, Massachusetts, Maryland, Maine, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, Vermont, Wisconsin and West Virginia.
Chemically, road salt and edible table salt are very similar. Road salt is halite, also called rock salt, the mineral form of sodium chloride. This naturally occurring substance is mined from the earth, crushed and sifted through screens to sort it into uniformly sized pieces. Rock salt can be converted to edible salt by processing to purify it and control characteristics like texture, moisture level and storability. Table salt is typically at least 97% pure sodium chloride, and it frequently includes anti-caking agents and iodine, a trace mineral or micronutrient that's an essential part of people's diets. And while rock salt can only be mined from the earth, there are other ways of manufacturing table salt, such as sea water evaporation.
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The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.