The majority of the traveling public who use road systems in the winter time really do not understand the complexity and environmental issues associated with winter road maintenance.  Many drivers expect to safely and expeditiously travel on road systems no matter how sever the snowstorm event or they expect to drive on bare pavement immediately after a storm.  Many of the maintenance departments do such a good job that some drivers do not have adequate vehicles and snow tires.  This driver expectation comes with an environmental and a highway operational price that is often hidden to the general public. One of the main sustainable transportation challenges associated with highway operations is the use of traction sand and excess application of chemical de-icing/anti-icing agents.

In some states the main course of action for wintertime road maintenance has been the reactive application of traction sand onto highway and municipal road surfaces, especially in mountainous and foothill environments. Studies have shown that overall, traction sand is not very efficient and of limited use when applied to icy roads. When dry sand is applied to roadways, approximately 30% is immediately displaced off the road surface and as few as 12 cars can entirely sweep the traction sand from snow covered surfaces (AASHTO, Center of Excellence, 2010). Traction sand is generally comprised of a mixture of well defined sediment sized material and salt, usually 5-15% of sodium chloride.  The use of sodium chloride is to prevent clumping of sand material which facilitates the spreading of the sand mixture onto the road surface from the truck and not for deicing.

Traction sand is removed from the road surface and into the drainage system by vehicle movement and displacement, wind, snowmelt and plowing and by the actual application to the road surface. Traction sand released into the watershed or highway drainage system has been shown to impact the local watershed environment by increasing sediment in waterways that can drastically change the stream morphology and existing habitat. High amounts of applied traction can change the stream benthic region thus impact macro invertebrates and fish egg viability. Large amounts of traction sand deposition can fill in sensitive wetlands, riparian vegetation and destroy wildlife habitat. 

State and local municipalities using traction sand for winter maintenance carry an environmental risk related to the environmental regulations such as the Clean Water Act. The Federal Clean Water Act prohibits the discharge of pollutants into waters of the US without a National Pollutant Discharge Elimination System (NPDES) permit.  The discharge of stormwater pollutants into waters of the US must not impact the physical, chemical and biological integrity of a receiving stream. Highway departments run the risk of EPA Municipal Separate Stormwater Sewer System (MS4) Program violations, obtaining a notice of violation to the Clean Water Act from the enforcement agency or are forced to be involved with the development and implementation of a potentially expensive Total Maximum Daily Load (TMDL) study. TerraLogic’s Art Hirsch has been involved with sediment-based TMDLs for Straight Creek (Eisenhower Tunnel) and Black Gore Creek (Vail Pass). Other regulations need to be considered such as Section 404 of Clean Water Act (dredge and fill of waters of the US; wetlands) and the Endangered Species Act.  

New pro-active wintertime techniques have been used, tested and adopted by many State Departments of Transportations (DOTs) that use anti-icing and pre-wetting techniques along with new types of chemical and solid deicers. Reactive approaches wait for the storm to start or ice/snow layer to develop on the road surface before initiating deicing action.

Proactive practices such as anti-icing are taken prior to and in anticipation of winter storms. Studies have shown that proactive wintertime actions are cost effective, less environmentally damaging and provide improved safety to the traveling public. The Colorado Department of Transportation has taken a proactive approach towards wintertime maintenance that has been cost effective and environmentally protective.

Anti-icing is a proactive strategy in which snow and ice control materials are applied before a snow, ice or frost event. This strategy treats potential conditions before problems arise giving maintenance professionals an advanced advantage.  Anti-icing prevents precipitation from bonding (freezing) with the pavement surface or weakens the bonds that may have formed for easier removal than with deicing. Once the bond is broken between the road surface and the ice/snow, accumulated snow and ice can be removed easier by snowplowing. When used correctly anti-icing can reduce plowing and decrease the quantity of chemicals used for winter maintenance. Reduction in accidents due to improved vehicle traction from increased ice/snow removal was realized by Idaho DOT (83% accident reduction) and Colorado DOT (23% reduction). 

Pre-wetting is the injection or spraying of a liquid chemical on solid chemicals or abrasives (traction sand) to enhance their effectiveness and reduce material loss and other forms of waste. It is a viable and desirable alternative to dry application of abrasives of solid deicing chemicals. When pre-wetting traction sand, the wetting agent adds weight and a cushioning effect when directly applied to the road surface; therefore, the material is less susceptible to displacement off the road. If the roadway surface has a layer of ice/snow, the pre-wet agent will partial melt the ice/snow thus allowing the abrasive to become embedded in the layer thus making the material more resistant to displacement. Pre-wetting has been shown to reduce the amounts of traction sand by 50% in cold weather (NCHRP, 2007).

The successful implementation of anti-icing and pre-wetting is dependent upon accurate weather forecasts that will guide the timing and the amount of material applied to the road surface. Anti-icing roads prematurely can result in inefficient use of chemical agent material and labor.  For maintenance departments without weather forecasting, “just in time anti-icing” is an option in which anti-icing agent is applied immediately before or during the initiation of the snowstorm.  Material Decision Management Systems exist that interfaces with weather forecasting and have been instrumental in improving the level of service and reducing maintenance costs. 

Over the past several years deicing and anti-icing chemicals have improved in quality. The Pacific Northwest Snowfighters Association (PNS), which is composed of DOT maintenance departments from the intermountain west and western Canada has established chemical constituent specifications. These specifications have specific concentration limits for heavy metals, phosphorus and cyanide. The main environmental concerns toward using chemical agents have been impacts to water quality and roadside vegetation. Studies have shown that there is a road dilution effect from snowmelts coming off the road surface that reduces the salt concentrations when discharged into a stream. The proximity of the road to a receiving stream is also a critical factor with direct stormwater discharges. Research studies have identified vegetation and soil impacts from high chemical application rates. Proper and efficient application of anti-icing and de-icing chemical is critical towards reducing vegetative impacts.

Highway maintenance department need to review and re-evaluate their winter time maintenance operations in light of increasing maintenance costs, potential environmental risks and liabilities and driving public safety. More public education and outreach would sensitize the traveling public about the overall environmental and economic costs of winter driving expectations.  

Highway departments need to develop winter highway maintenance programs that are sustainable and pro-active in nature by the integration of three main and broad areas; environment, driving public safety and economics.  Highway Maintenance-Sediment Control Action Plans that adopt pro-active actions, complement this sustainability concept by identifying cost effective actions that will reduce environmental impacts, while maintaining the driving publics’ safety and meeting the aesthetic expectations of the community. The overall benefits of a Sustainable Sediment Control Action Plan are as follows:

• Save wintertime maintenance costs (labor, materials and fuel) by optimizing plowing frequencies and changing deicing strategies thus reducing fuel consumption and green house gas emissions
• Reduce overall environmental liability and risk to the highway maintenance department; thus saving potential cost associated with fines and imposed mitigation
• Reduce life cycle cost by using chemical deicing versus traction sand
• Improve air quality by reducing PM10 development 
• Enhance habitat for native wildlife and vegetation 
• Improve the roadside aesthetics 
• Improve driver and bicycle safety and awareness
• Minimize  costs associated with traction sand application, collection, transportation, handling and landfilling