In addition, prewetted salt works under conditions that render dry salt ineffective. Roadway salting only performs effectively when moisture releases the heat from dissolving salt. At temperatures below freezing, prewetting insures moisture will be present to dissolve the salt. Salt alone would not do the job. Since the late 1960s, Iowa has used liquid calcium chloride to prewet salt.
Calcium chloride remains wet at low temperatures and is itself a deicing agent.
However, it leaves the road wet even after snow and ice have broken up, resulting in blowing snow sticking to the road and creating a hazard to drivers. Calcium chloride costs about 63 cents a gallon. In addition, when ice and snow are gone, salt brine leaves a dry pavement. Finally, salt brine costs only about 6 cents per gallon, a considerable savings over calcium chloride. In addition, 60-gallon prewetting applicators will be mounted on highway department trucks.