What is a snow and ice removal program?
Truck applies chemical de-icer to roadway to prevent frost and ice from forming. |
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.
In winter 2008/09, WSDOT teamed up with Darigold to keep traffic moving by producing a locally made anti-icing product that benefits both motorists and the environment. This new anti-icer is made up of salt, de-sugared molasses, mineral and water. Darigold delivers the salt water to WSDOT’s maintenance facility in Chehalis at no cost, instead of having to pay to have the water treated and disposed of at another location. Darigold can deliver up to 11,000 gallons of left over salt water to the Chehalis Maintenance facility daily. WSDOT began using this product on US 12, White Pass last year and is now expanding its use to other state routes in western Washington.
The goal remains the same: to provide a higher level of service with the existing level of funding. Increasing demands on mobility, safety, and environmental protection have resulted in less reliance on abrasives such as sand and increased use of anti-icers. 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.
Why is WSDOT making its own anti-icer?
By manufacturing its own anti-icer, WSDOT is able to keep roads clear for drivers, respect the environment by using recyclable, natural products, and reduce operational costs. Producing this product in-house maintains a steady and reliable supply of anti-icer and reduces dependence on commercial vendors. This is especially helpful during a severe winter storm event when supply may be limited to due to road conditions and closures. Winter snow and ice control is the single most expensive activity in maintenance, making up close to 20 percent of the entire WSDOT Maintenance budget. This product is expected to help WSDOT reduce some of these costs.
Is this new anti-icer safe and does it work?
WSDOT’s Materials Lab tested this product and used it on state roads in Lewis County during the winter of 2007/2008. The product was also tested at independent labs in Boise, Idaho and British Columbia, and received approval from both laboratories.
The new anti-icer meets Pacific Northwest Snowfighters Association’s (PNS) specifications for safety, environmental preservation, infrastructure protection, cost-effectiveness and performance in winter maintenance.
Is it harmful to the environment or my car?
WSDOT continues to limit corrosion to vehicles by using less corrosive inhibited products on our roads and bridges. The new anti-icer is 77 percent less corrosive than straight salt, exceeding the PNS standard which is 70 percent. WSDOT thoroughly trains all maintenance work force on the correct use rates of anti-icing chemicals and uses the latest technology and equipment to ensure accurate equipment anti-icer calibration.
Each winter season, roadside soil, surface water, or groundwater monitoring is conducted at various locations on the highway system to ensure that chloride loading is not occurring in the environment. 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.
Most vehicles manufactured today are made with a protective under coating that helps the vehicle resist damage and corrosion from road salt or chemicals. WSDOT continues to strongly recommend that drivers who drive on roads treated with anti-icer, wash their vehicles to prevent build-up which could cause corrosion over time. 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 (pdf 2.90 MB).
How much anti-icer can WSDOT produce?
WSDOT’s Chehalis Maintenance facility is expected to produce as much as 600,000 gallons of salt brine anti-icer this year. It’s salt vendors Lynden Transport, Inc. and Salt Distributors Inc. have moved over 63,000 tons of salt to Washington so far, with more on the way. Maintenance areas statewide are also filling 1.4 million gallons of liquid anti-icer storage in preparation for winter maintenance.
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. WSDOT’s new salt brine anti-icer is a liquid compound consisting of salt, sugar, mineral and water. A 23.3 percent solution of salt makes up 75 percent of the compound. De-sugared molasses makes up 20 percent and calcium chloride five percent. The salt is the main snow- and ice-fighting ingredient in the compound. Sugar helps bind the compound to the road surface, helping it last three days or more in average conditions. Calcium chloride helps the compound maintain its effectiveness at lower temperatures, melting snow and ice down to 10 degrees Fahrenheit.
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 compacted 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. By manufacturing it’s own anti-icer in-house, WSDOT proves to be innovative and resourceful in it’s use of anti-icing and snow and ice control techniques.