OHIO VALLEY — Sodium chloride, better known as salt, is not only great for bringing out the flavor of a delicious roast, but for the Ohio Department of Transportation (ODOT) it is the best tool for melting snow and ice to keep highways safe during winter.
Each year, the Gallia County ODOT Garage, with a fleet of 12 snowplows, uses about 2,200 tons of road salt during the months of October to March. In Meigs County, with 10 snowplows, the average for that time frame is 2,300 tons. Each snowplow is equipped with a calibrated salt spreader that, depending upon the road conditions, can be adjusted by the driver to ensure the right amount of salt is used at the right time.
“Although salt is not the only deicing material we use, it is by far the most cost-effective solution for controlling snow and ice,” says ODOT District 10 Deputy Director Steve Williams.
Since the 1940s, all highway departments have used some form of sodium chloride to rid roadways of snow and stop the formation of ice. How does this natural resource actually melt snow and ice?
We all know that as the temperature of water reaches 32 degrees Fahrenheit or zero degrees Celsius, ice forms. However, unlike other substances, ice is less dense than water and therefore freezes on the surface, which is why lakes and ponds freeze at the top first.
The magic of salt is that it makes water more dense, and therefore the temperature at which ice forms in a salt-water solution needs to be colder than water’s natural freezing point. In fact, salt melts ice down to negative six degrees Fahrenheit. As most snowstorms occur between the temperatures of 32 and 20 degrees Fahrenheit, salt is by far the most effective means for melting snow and ice. However, when the pavement temperature gets too cold, ODOT uses other deicing material such as calcium chloride which has a lower freezing temperature than salt.
Although science can easily explain how salt keeps water from freezing, plowing snow is just as much an art as it is a science.
For example, one area which requires an artful approach is that of predicting the weather. Or at the very least, being able to adapt to changing weather conditions, which in Ohio seem to change every minute.
“From pretreating the roads to determining which deicing material to use, the weather determines everything we do,” says Williams.
Williams also says that snowplowing itself requires years of experience and a “feel” for the roadway. Especially in heavy snowstorms with decreased visibility, drivers must rely not only on visual and physical queues, but an intimate knowledge of the roadway that they’ve gained from decades of plowing.
With trucks road ready, salt barns stocked and drivers well trained, ODOT’s continued success of its snow and ice operation rests on the interplay between science and art.