Salt brine applied on a sunny afternoon helps fight slippery overnight frost
AMES, Iowa – Jan. 6, 2011 – Even when there is no snow on the ground and daytime temperatures are above the freezing point, the Iowa Department of Transportation (DOT) sometimes uses salt brine as a tool to help keep roads safe when overnight temperatures dip and slick frost threatens to form on the state’s highways.
Salt brine is a simple solution of rock salt and water made at Iowa DOT maintenance garages in large tanks. About two pounds of rock salt are added to each gallon of water to make the solution. When sprayed on the roadway at 50 gallons per mile, the mixture is equivalent to approximately 110 pounds of salt spread over a 12-foot wide roadway, one mile in length.
While it might look unusual to see road crews spraying roads and bridges with salt brine on a day when roads are clear and the sky is sunny, this proactive treatment prevents a bond from forming between the roadway and precipitation when conditions change.
The use of brine has many advantages; it can:
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Lower the cost of road maintenance by reducing the amount of deicing materials used.
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Return road surfaces to normal winter driving conditions faster, resulting in fewer crashes and delays.
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Jumpstart the melting process, because salt needs moisture to begin the melting process.
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Carry over between storms because it leaves a residue on the roadway.
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Be sprayed on materials distributed from the back of a snowplow, thereby activating the dry rock salt.
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Prevent dry materials from bouncing or blowing off the road surface.
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Inhibit a bond from forming between snow and ice and the pavement surface.
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Allow crews to cover more territory during a storm.
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Minimize environmental concerns because materials stay on the roadway, rather than on the roadsides.
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Reduce the amount of sand that is needed, saving tax dollars and natural resources, and preventing sand from entering storm sewers.
While brine is not the answer to all snow and ice situations, it does give workers one more tool against frost, snow and ice, which helps make Iowa a safer place to drive.
