What used to be an operation consisting of a fleet of trucks plowing snow and throwing out rock salt or sand is evolving into a high-tech world of specialized chemicals, computerized discharge controls, decision-making software, road and weather information systems, automated treatment systems, and automatic vehicle location systems. Public works employees are increasingly challenged to find the most efficient and effective use of these technologies to meet their department's snow maintenance goals.
Some maintenance operations have faced this challenge with hesitation. For smaller departments—already overworked and understaffed—the overwhelming array of chemicals, equipment, and software, and the associated learning curve, may be too much to take on. Other departments have postponed implementation due to start-up costs. But with increasing environmental regulations and decreasing revenues, the time to embrace this technology is closing in.
Steve Gray, special projects engineer with the New Hampshire DOT (NHDOT), said, “Back in 1994 we participated in the T&E-28 project sponsored by the Federal Highway Administration (FHWA) to test and evaluate the use of anti-icing chemicals. As part of that study, the NHDOT used potassium acetate as an anti-icing agent. After the project ended, NHDOT chose to postpone the implementation of a liquid anti-icing program due to the high cost involved in re-equipping our vehicles and facilities.”
NHDOT recently made the decision to begin anti-icing treatments this year on a specific section of Interstate 93 near Manchester. “Our decision to use a liquid anti-icing chemical in this area was made for primarily three reasons,” said Gray. “First, NHDOT has plans to expand that section of I-93 from four lanes to six or eight lanes of traffic. As a result of that plan, NHDOT agreed to not increase chloride levels in the area as part of a commitment to the agencies involved in overseeing the watershed in that area. Second, NHDOT is trying to reduce salt use due to a dramatic increase in salt prices in our area. Third, NHDOT is endeavoring to provide a better level of service to our citizens.”
Environmental concerns, cost savings related to chemicals, and commitments to increase level of service have provided the motivation for other agencies already using chemicals for anti-icing to invest more fully in the use of chemicals in other snow maintenance activities. Many agencies now include the use of liquid chemicals in their deicing operations for prewetting rock salt or abrasives.
Moving from a more traditional method of snow and ice control to the new arena of snow maintenance is a big step for any agency. To help state and local jurisdictions make this move successfully, the National Cooperative Highway Research Program (NCHRP) has prepared a publication titled Snow and Ice Control: Guidelines for Materials and Methods. This booklet, published by the Transportation Research Board as NCHRP Report 526, is an essential manual for those involved in winter maintenance.ESTABLISHING AN EFFECTIVE PROGRAM
Implementing an anti-icing/deicing program involves choosing the type of chemical to use, application guidelines to follow, and equipment to purchase. These choices are integrated with existing department policies concerning priority levels for routes and level of service desired throughout a storm.
The most widely used chemicals for anti-icing/deicing include sodium chloride, calcium chloride, magnesium chloride, potassium acetate, and calcium magnesium acetate. NCHRP Report 526 can be consulted for specific chemical properties such as mix concentrations and application rates.
A successful anti-icing/deicing program also requires the use of a road weather information system (RWIS). This system is capable of reporting air and pavement temperatures—which can sometimes differ by 20° F—relative humidity, wind speed and direction, subsurface temperature, depth of precipitation on the road, and salt concentration.
Public works personnel can consult an RWIS for help in making decisions related to anti-icing operations such as mobilization of personnel, selection of chemicals, snow or ice control strategy, and route priorities. This is important because anti-icing has proven to provide significant benefits, including preventing formation of a bond between the pavement and snow or ice, reducing clean-up times, eliminating the use of abrasives, and decreasing the amount of materials used, labor costs, and wear on plows and blades.