What is a snow and ice removal program?
Anti-icing is the practice of applying chemicals to roadways to prevent frost and ice from forming. if it does, de-icer helps break the bond to keep it from compacting and bonding onto the highway. WSDOT began using these chemicals in the early 90's. The program continues to improve each year as new chemicals, new application techniques, and experience grows.
The goal remains the same: to provide a higher level of service with the existing level of funding. The experience of past winters reinforces the idea that the anti-icing program has resulted in better pavement conditions, fewer collisions, less severe collisions, and significantly improved freight mobility (big trucks having to chain up less frequently and completing more trips). Average winter speeds have also increased due to consistently better winter roadway conditions.
Does Anti Icing Harm the Surrounding Environment?
Our goal is to minimize chloride levels in the roadside environment. Each winter season, roadside soil, surface water, or groundwater monitoring is conducted at various locations on the highway system. This monitoring has been an ongoing effort since 1999, and has ranged from academic research projects to less formal “before and after” winter season water sampling and testing.
We continue to find that chloride levels are well below regulatory guidelines or standards. For example, in a study of water quality in Peshastin Creek along US 97, the Blewett Pass Highway in Chelan County, the typical level of chlorides in the creek was between one and five parts per million (ppm). The standard for your drinking water is 250 ppm. Annual precipitation, including melting snow provides adequate dilution to prevent build up.
Springtime travelers through Northwest mountain passes may notice brown needles on certain types of trees near the roadway edge. The browning pattern appears on the trees through spring until new growth takes over and green needles reemerge by summer. Learn more about needle browning.
What types of snow and ice removal does WSDOT do?
Liquid anti-icers are generally applied to the roadway before weather events occur, and prevent ice crystals from bonding to the pavement. Chemical concentrations on the road surface is what determines the effectiveness of anti icers. Statewide, a variety of different chemical anti-icers are used, depending on temperature, humidity, and the work to be accomplished. The least aggressive (weakest), but most environmentally benign anti-icer is CMA - Calcium Magnesium Acetate. It is used primarily in western Washington on bridges and overpasses for frost control. Magnesium Chloride is stronger and used in most parts of the state on roads at higher elevation or those subject to colder temperatures. Calcium Chloride is used where conditions can be most severe. It is effective at very low temperatures where other anti-icers are not. As new experimental anti-icing chemicals become available, the department will evaluate them for their effectiveness.
With the availability of solid snow and ice control chemicals, maintenance crews may suspend the use of liquid anti-icers as soon as there is any snow or ice accumulation on the roadway. Solid de-icing chemicals look like sand and are applied like sand. Solid chemical de-icers are used to keep accumulating snow loose and “plowable” so it can be removed with snowplows from the roadway. If snow and ice become compact and bonded to a paved surface, the solid chemical de-icers can absorb into the compact snow or ice, melting it and breaking it up for removal with snowplows.
Comparing salt to corrosion-inhibited anti-icers
During the first two years of testing, results using salt were compared to results using corrosion-inhibited anti-icers. Although the unit cost of salt products is considerably less than the unit cost of corrosion-inhibiting anti-icers, overall costs at the end of a winter season are similar. This is because more salt has to be used, and applied more often, to achieve roadway condition results similar to the corrosion-inhibiting anti-icers. The performance of salt was similar to that of corrosion-inhibiting anti-icers in keeping roads bare and wet during snowy or icy winter conditions. The corrosion-inhibiting anti-icers proved to be consistently less corrosive to steel on motor vehicles than salt, but corrosion to sheet and cast aluminum on vehicles was mixed. In some cases, salt was more corrosive to aluminum. In others, salt was less corrosive to aluminum. Environmental impacts from the use of salt were similar to impacts from the use of corrosion-inhibiting anti-icers. In both cases, chlorides detected in roadside soils and water were far below levels of concern for the protection of the environment and public health. At the end of two years, field-testing data indicated that WSDOT’s emphasis on corrosion-inhibiting anti-icers appears to be preferable when compared to an emphasis on using salt.
What about good old-fashioned sand?
WSDOT continues to use sand under certain winter road conditions. Sand is primarily used to provide traction at intersections, curves, and grades where chemical treatments are not available or effective. Even its application is improved. Sand trucks have a reservoir of liquid anti-icer that is used to wet the sand as it's applied. Dry sand is blown to the shoulders by the first few vehicles that pass requiring it to be reapplied frequently. The chemically wetted sand stays where it’s placed, melts into the snow, and does not require frequent reapplication.
One result of the anti-icing program is a reduction in the use of sand. In some parts of the state, like Spokane, air quality requirements are such that sand use has been limited because it dries and contributes to airborne dust concentrations. Cost savings have resulted as spring clean up of sand accumulated along the roadside has been dramatically reduced. Highway re-striping needs have also been reduced as less sand means less abrasive action that wears road stripes quickly.
The future of WSDOT's Snow and Ice Removal Program
WSDOT’s goal is to be on the leading edge of snow and ice control technology. With continued research on new products and equipment technology, the use of anti-icing and other snow and ice control techniques is going to continue to be a key tool for winter maintenance.