With the costs of materials skyrocketing, public works departments are increasingly looking for more efficient alternatives to simply spreading sand and salt on their roads to fight winter snow and ice accumulations, and one promising trend is the pretreatment of salt.
A case in point is the town of Acton, Mass., where the Highway Department has implemented a new snow and ice removal program for the 105 miles of roads in their charge, based on the favorable results of an experiment conducted last year.
After much researching and networking with other highway and public works officials who were trying alternatives to sand and salt, the Highway Department tried pretreating its salt stockpiles with an additive consisting of a blend of liquid magnesium chloride and a corn-based enhancer before applying the material to road surfaces for the 2005/2006 winter. It worked so well the department intends to continue the program, according to Russell Robinson, assistant highway superintendent.
"We're very happy with this. Pretreated salt eliminates the use of sand, and saves us the cost of sweeping in spring."
The department documented the results of its experiment in a recent report entitled "Evaluation Of The New Snow And Ice Removal Program."
According to the report, the additive allows the salt to be more effective at lower temperatures and reduces the "bounce" of the salt when spread. The salt stays on the road surface, not on the shoulders, and creates brine that prevents snow and ice from sticking to the road surface.
In analyzing the results of the trial, the report notes that the cost to implement the pretreatment program for the 2005/2006 season was $79,000. The cost included about $68,000 for upgrades to the town's six sander trucks — upgrades that involved mounting blades under the trucks ("belly scrapers") — so that the blades scrape the road in front of the pretreated salt. The remaining $11,000 cost was for the liquid storage tanks and the equipment for the additive.
After the first two storms of the season, the use of sand was completely eliminated. Furthermore, the Police Department reported satisfaction with the program, there was only a minor increase in the amount of salt used compared to the previous five seasons, and there was a total savings of $89,000 in the cost of materials and street sweeping.
On a larger scale, the Maine Department of Transportation is now pretreating salt but the application differs from that of Acton in that MEDOT is applying the liquid deicer from tanks aboard its trucks.
Highway Maintenance Engineer Brian Burne of MEDOT's Bureau of Maintenance & Operations (BMO), which is responsible for more than 400 trucks, said one or two on-board tanks apply either a salt brine or magnesium chloride blend to the salt. Adding the salt brine or magnesium chloride boosts the effectiveness of the salt. Which one is used depends on the temperature.
BMO is also trying out the use of super-saturated brine to pre-wet the salt. This brine has 30-percent salt, compared to the 23 percent in conventional salt solutions. Experiments in Europe have proven that the supersaturated brine is much more effective at lower temperatures than conventional brine, Burne said. He added that truck spinners must be modified to handle the 30-percent solution.
Burne also pointed out they prefer on-board-truck applications of deicers to pretreating stockpiles, because it is not always economical to use pretreated salt when cheaper, untreated salt can do the job depending on the temperature and type of storm.
The magnesium chloride blend used in the on-board tanks is the same type used by the town of Acton — a patented product called Ice B'Gone that incorporates low molecular weight carbohydrates, or simply, sugars, as a key ingredient.
Some towns prefer to have pretreated salt delivered to their yards instead of treating the salt themselves, or simply do not have trucks equipped with the proper dispensing equipment. To accommodate these customers, such salt distributors as International Salt Company maintain stockpiles in strategic market areas where they treat the salt prior to delivering the material.
One site is located on a pier in the Charlestown section of Boston, Mass., where 5,000 tons of International salt was recently treated with the magnesium chloride blend by Gorman Brothers of Albany, N.Y.
The contractor used a Midland portable pugmill to mix the untreated salt with magnesium chloride supplied by a tanker truck.
Lauren Montenegro, owner of Innovative New England, was on hand to represent the supplier of the magnesium chloride blend that was added to the salt in the pugmill. Her company serves as an independent representative for Ice B'Gone and other deicing products manufactured by the Innovative Company, which is headquartered in Ontario, Canada, and has a U.S. office in Rome, N.Y. Montenegro markets the products in Maine, New Hampshire, Rhode Island, and central and eastern Massachusetts.