DPW deploys new anti-icing program
January 25, 2013
After the three massive snow storms dubbed "Snowmageddon" hit Joint Base Myer-Henderson Hall in February 2010, the Directorate of Public Works invested in upgrading its snow-fighting capability and improving snow removal operations on JBM-HH. The cornerstone of the DPW's snow fighting strategy is a new anti-icing program using salt brine.
What is salt brine?
Salt brine is water saturated with sodium chloride, or more simply, rock salt dissolved in water. Today, it is used as a supplement to the traditional street clearing method of spreading a rock salt and sand mixture. It is JBM-HH's anti-icing program beginning in January 2013 to take a proactive approach to controlling snow and ice on JBM-HH's roadways and parking lots. Applying brine to the roadway surface is similar to spraying a frying pan with either oil or a cooking spray to keep food from sticking to the bottom of the pan.
When is salt brine used?
Salt brine is applied to the road surface up to 72 hours in advance of a predicted snow event. Ideally, pre-application is done during dry weather, allowing the brine to dry completely and embed into the asphalt before freezing precipitation (snow/ice) arrives. When snow hits the asphalt, the brine activates and immediately lowers the freezing point of water. The melting process, however, does not happen immediately. Streets and parking lots may appear snow covered, but don't be deceived by it. The objective of the salt brine is to prevent the bond of ice or snow to the roadway, not to melt it; thus allowing smooth, easy plowing during the weather event. Under the traditional method, when a previously rock salt-treated street was plowed, most of the salt was pushed off the road surface along with the snow. Water and rock salt is mixed into brine to a 23.3 percent concentration of salt which will withstand freezing temperatures to minus 6 degrees, and can be spread with temperatures as low as 10 degrees.
Anti-icing versus De-icing
Anti-icing prevents the snow and ice from bonding to the pavement (proactive approach). However, de-icing is designed to melt through the ice and snowpack and to break its bond with the road surface (a reactive process). Research studies have shown that it can take four to eight times more salt to de-ice than to anti-ice.
Why use salt brine?
It is anticipated that the cost savings for DPW will be approximately $10,000 per storm in material costs alone. It takes about 2.5 pounds of salt to make one gallon of liquid sodium chloride (brine). It costs about $.6 cents/gallon (using $50/ton for salt) to make the 23.3 percent salt brine solution. Therefore salt brine is much more cost effective, and by using the salt brine it allows the DPW to apply it during normal working hours. In addition, this allows the DPW to have all the road and travel lanes of the parking lots pre-treated before driving conditions deteriorate. This will help the snow/ice from bonding to the pavement surface. As a result, the roads return to bare pavement more quickly once the storm has ended.
How is salt brine applied to the road when pre-treating?
Motorists can expect to see DPW crews pre-treating roads with salt brine using pickup trucks and utility vehicles with sprayer units that slide into the bed of typical plow truck.
What should I do when following a vehicle applying salt brine?
Vehicles applying salt brine usually travel at speeds around 25 mph. Motorists should stay back at least 50 feet from the vehicle while pre-treatment operations are in progress.
What are other advantages of using salt brine?
1) Anti-icing returns road surfaces to normal faster, resulting in fewer accidents and delays.
2) Using a liquid ice-melt jump-starts the melting process because rock salt needs moisture to be effective.
3) Brine doesn't bounce or blow off the road surface so material is used more efficiently.
4) If the storm is delayed, salt residue remains on the road ready to begin work when precipitation begins.
5) Crews can cover more territory by beginning treatment in advance of a storm.
6) Increased efficiency results in use of less salt, minimizing environmental concerns.
7) The use of dry sand/abrasives for snow and ice control has very little value in providing lasting friction enhancements and they do not melt snow/ice.
8) Sand/Abrasives although not a chemical, sand/abrasives have a negative impact on the environment. Sand/abrasives use contributes to sedimentation in streams, air quality, water quality and impacts fish and other aquatic resources.