Du, Sen

Pre-wetting is an important tool in the toolbox of winter road maintenance (WRM) operations. This research project collected all available and recent information regarding pre-wetting practices through a comprehensive literature review, an online survey of WRM practitioners, interviews and case studies of nine selected agencies, and outreach to six identified equipment manufacturers/distributors. Through the synthesis of current and best practices, the project resulted in preliminary guidelines or recommendations, mainly based on trial-and-error and field experience, instead of systematic and scientific investigations. There have been many success stories of pre-wetting practice by transportation agencies in northern climates. The pre-wetted material stays on the surface longer, has less bounce and scatter, and resists traffic action. The case study agencies also reported that pre-wetting allowed them to achieve the specified level of service more quickly. A pre-wetting rate of 8–12 gal/ton is effective and 8–16 gal/ton is reasonable for increasing the speed and total ice melting capacity of solid salt and reducing the snow-pavement bond. Practitioners have reported that higher pre-wetting rates (than 10 gal/ton) can achieve better operational results, thus reducing the amount of granular salt needed. For trucks equipped with pumps to make salt slurry, a higher pre-wetting rate (30 to 50 gal/ton) can be achieved. A higher application rate should be used when there is a lower pavement temperature or a more severe snow event. All survey respondents reported the use of on-board systems to apply liquids to solids. Agencies may face initial resistance to pre-wetting from operations staff or other stakeholders, but training and information dissemination coupled with effective field trials will gradually mitigate concerns and build rapport. The project also identified knowledge gaps or research needs relevant to pre-wetting practice.

Winter roadway operations, commonly known as snow/ice control operations, are one of the most critical functions of state, provincial and local transportation agencies in cold regions. These operations aim to provide safety and mobility by timely and effective application of materials and plowing. The most common materials used are salt (sodium chloride, solid and brine), magnesium chloride-based, and calcium chloride-based deicers, agro-based additives and blends, and abrasives, with the specific choice and application method and rate dependent on temperature, precipitation type, level of service goals, budget, and environmental sustainability. Best practices of material application are designed to apply the right type and amount of materials in the right place at the right time. A companion document to this report, the “Material Application Methodologies Guidebook,” synthesizes the use of materials, including application strategies, application rates, and application equipment. This report documents the literature review and agency interviews that were conducted to assemble the information for the Guidebook.