Salting the Earth

When the City of Carthage fell at the end of the Third Punic War, 146 BC, victorious Romans pulled Phoenecian ships out of the harbor and set them on fire before moving through the city, house to house, rounding up and selling 50,000 people into slavery. Then they set the city on fire. As a final insult before they left, it is said that the Roman soldiers sprinkled salt upon the ground to ensure that nothing could ever grow there again.

During the 17th and 18th centuries, Spain and Portugal punished traitors within their empires by executing them and then pouring salt on their land. Closer to home, some say that Union soldiers salted the fields in Georgia during General Sherman’s infamous March to the Sea (though it’s not likely they used very much, since salt was a hot commodity during the American Civil War).

After the capture of ancient Carthage, came the salting of the land. (Photo from Wikipedia)

Throughout history, pouring salt on the land has symbolized a curse not only for current inhabitants, but also for future generations. Then, during the winter of 1941-42, New Hampshire became the first state in the U.S. to apply salt to roads to help melt snow and ice more quickly. The U.S. used a total of 5000 pounds of road salt that year. After World War II, road salt became more and more common. One million tons of salt were used in 1955, and 10 million in 1972. In 2013, local, state and federal highway departments applied 17 million tons of salt to roads across the nation. Whose future do we seek to curse?

The Minnesota Pollution Control Agency reports that roughly 40 of our metro area lakes and streams have already been contaminated by too much salt. Another 40 are near the threshold and will become impaired if they get any saltier. Even the groundwater we drink is at risk; 30% of private wells in the metro are already considered impaired by too much chloride.

Too much salt at a local store
Winter salt helps to melt ice, but many people use too much. Salt from sidewalks, parking lots and roads has already contaminated 40 Minnesota waterways, and another 40 are in imminent danger,

Though the Roman and Union soldiers’ salting of the earth may have been mostly symbolic, our modern communities face the very real risk of suffering unintended consequences from using road salt, year after year. There is currently no practical technology for removing salt from our surface and groundwater resources and soil once it is there, so the only solution is to use less salt and hope that it doesn’t build up too quickly.

We all value our safety when driving in winter weather, but clean water and healthy soils are vital to our long-term survival as well. Here are three ideas from the Twin Cities Metropolitan Area Chloride Management Plan for how each of us can help:

  • Drive slow & wear boots. Support local and state road maintenance crews, as well as businesses and other large parking lot owners, in their efforts to reduce salt use. Drive slower and wear appropriate shoes when it’s snowy and icy outside.
  • Don’t use more salt than necessary. One pound of salt (one heaping coffee mug) is enough to clear a 20-foot driveway or 10 sidewalk squares (250 sq. ft.).
  • Skip the salt when it is colder than 15°. Salt works by lowering the melting temperature of ice so that it melts when the temperature is below freezing (32°F). However, traditional road salt (sodium chloride) doesn’t work when it’s colder than 15°F, so it is a waste of time and money to put down salt on very cold days. Magnesium chloride and calcium chloride work at colder temperatures (-10° and -20° respectively) but can be more expensive.
  • Sweep up and reuse left-over salt after the ice melts.
  • Watch your water softener. Stop using your water softener if your water hardness is less than 120 mg/L CaCO3. If you do need a water softener, switch from a timer-based to a demand-based system and install a bypass for your outside spigot so that you aren’t softening water for irrigation.

To learn more about water and road salt in the Twin Cities, visit:

One pound of salt (one heaping coffee mug) is enough to clear a 20-foot driveway or 10 sidewalk squares (250 sq. ft.). (Photo from Clean Water MN)