Editor’s Note: This is a continuation of coverage from our June 2011 cover story on the latest technologies in winter maintenance.
by Tina Grady Barbaccia
Salt has been the tried-and-true material when it comes to winter maintenance, but one of the latest trends in winter maintenance is a shift toward brine, along with other liquid deicers to make the salt more effective and economical.
The State of Maine has been pioneering use of treated salt, Vermont has been trying it and New Jersey is starting to take a look at it, says David Wood, president of Sears Ecological Applications Co. (SEACO). Other areas, such Illinois’ McHenry County, has also experimented with treated salt and manufacturing its own brine. “The drivers here are environmental concerns, cost and performance,” Wood points out.
With tightening environmental regulations and the current weak economic milieu, there is a need to stretch salt as far as it can go so use of advanced brine technology has become a critical part of winter maintenance.
This served as the impetus for the Maine Department of Transportation’s to conduct a treated salt study. According to the study, Maine DOT found that the combination of a treated salt and liquid deicer through onboard prewetting created the fastest and longest-lasting effect and the lowest cost, from both a fiscal and environmental standpoint. Treated salt usage represented about 30 to 35 percent product saving versus traditional untreated salt, and the untreated salt with additional onboard pre-wetting represented about a 40 to 50 percent savings versus untreated salt.
The purpose of the study was to observe the effectiveness of pre-treated salt and to understand how two different types of liquids, Ice-B-Gone and magnesium chloride, would work in the application. The methodology was having two adjacent interstate crews coordinate timing of applications while tracing various application rates of the different materials, with and without pre-wetting. The rest results were conducted using conventional with rock salt (dry and with liquid added), magnesium chloride (Mag) treated salt (dry and with additional liquid added) and brown treated salt (Ice B Gone) treated salt (dry and with additional liquid added).
Maine DOT’s initial trial of six different methods of applications of salt treated salt follows:
The use of salt brine — a mixture of 23 percent salt and 77 percent water (the carrying capacity of slat in a water solution) — for melting snow and ice was developed in Europe. The mixture is sprayed directly on the road as an anti-icing agent. Although salt brine has the same melting characteristics of regular salt, because it is in brine form, it has the advantage of working immediately and doesn’t have the problem of “bounce and scatter” off the road because of its consistency, according to a study of salt brine use by the Vermont Agency of Transportation, Materials and Research Section. The agency found that brine was cost effective to produce, at about $0.10 per gallon. Additionally, other deicing chemicals can be mixed into the salt brine to lower the effective melting temperature.
During the study in which experimental test sections of Vermont interstates were treated with salt brine and salt brine mixtures, the agency found that it saved an average of 24 percent of material usage.
“Although the data sets were not as extensive as the research team initially thought, the research project was able to produce salt savings of approximately 30 percent and materials cost savings of approximately 30 percent and materials cost savings of approximately 24 percent during the first year of experimentation,” according to the Vermont DOT report. “If such a cost savings could be projected statewide, the potential savings would be almost $1 million annually.”
The research team agreed that there is potential for more salt and cost savings as staff becomes more experienced with the technology.
“Through the use of salt brine, brine blends and brine technology, the research project was able to produce safer, better winter roads at [a] lower cost, [and use] less salt and less sand,” the agency says in the report.