To prevent a repeat of last winter’s extreme snow and ice accumulations that paralyzed the city for days at a time, Portland plans more widespread use of road salt this year.
City Unprepared for Last Year’s Thaw and Freeze Event
Last year’s storm was complicated by a short thaw followed by a days-long deep-freeze that turned packed snow into a sheet of ice that plows couldn’t remove. Traffic was stopped trying to navigate slippery hills and city streets, and schools and businesses were closed for days at a time. Finally, the Washington Department of Transportation brought in eight plows and a supply of road salt, however, many felt that not enough salt was applied and too late to be effective.
Portland Reconsiders More Road Salt Use This Year
The city has begun to re-evaluate its long-held belief that road salt draining into rivers and streams from runoff is too environmentally hazardous. This year, city officials felt that the benefits of using road salt during the area’s crippling though relatively short winter freezes would outweigh any environmental damage.
The city’s new plan calls for more widespread use of road salt, with six new salt spreaders that can be installed on city trucks, and it will turn to other bureaus and private businesses to get more crews out clearing roads. City Commissioner Dan Saltzman and the Transportation Bureau asked for $1.2 million to buy new snow-clearing equipment and $1.6 million a year for PBOT’s weather-response staff and materials. Instead the bureau got $30,000 for the new salt-spreaders, with $300,000 set aside in contingency funds for any unforeseen snow removal costs.
“If we do see a major snow or ice event on the level of last year, I won’t be hesitant to ask for more money,” said Saltzman.
City’s Goal of Passable Roads During This Year’s Snow and Ice Storms
Portland’s transportation bureau this year is prepared for what weather forecasters predict to be a similar snowy season due to the influence of La Nina, a pattern of oceanic cooling. The city will keep 300 tons of salt on hand, enough to treat between 2,000 and 3,000 lane-miles of roadway, and will be able to receive and store another 1,000 tons of salt ahead of a big storm.
With a goal of trying to achieve “passable” roads that are navigable for vehicles with front-wheel drive, Portland will try to limit its use of road salt to the following roads that are routinely impassable in snow, and will focus on public transit and emergency routes:
- West Burnside Avenue
- Sam Jackson Park Road
- Terwilliger Boulevard
- Skyline Boulevard
- Germantown Road
- Southeast 112th and Mt. Scott Boulevard
- North Going Street
To prevent a repeat of last year’s city-wide shutdown of schools and businesses, the city will plow key school routes and the central business district, where heavy traffic was previously thought able to keep roads clear. The city will also consider even more widespread use of road salt in severe storms.
Last Year’s Conservative Approach to Plowing Didn’t Protect Road Surfaces
To avoid damage from plow blades on road surfaces, Portland city plows leave up to half an inch of snow on the road, relying on chemical deicer, the weight of passing vehicles and improving weather to remove the rest. This method didn’t work during last winter’s thaw followed by a days-long freeze, and even with its conservative approach to plowing, Portland still incurred significant road-repair costs after the storm.
Midwestern “snow belt” region cities follow a different plan, setting target times to achieve bare and wet pavement after snowfall. Seattle tries to reach bare and wet pavement within 12 hours after a lull in the storm.
Studies Show Dry Salt Leaves Pavement to Deposit on Side of Road
Portland has learned much from last year’s major snow and ice storm. Although the city is unique with its thaw and freeze events and hilly terrain, city officials should also consider successful methods used by other areas of the country that routinely experience severe winter storms.
Portland’s new de-icing procedures will use dry rock salt or mixtures of rock salt and abrasives delivered to the middle of the road from the bed of a truck to a spinner where it can be widely-dispersed onto the pavement. It is hoped the chemicals will then melt to a liquid which will move away from the crown of the roadway to the lower levels of the roadway, where they can help break the snow and ice on the pavement.
A study conducted by the Michigan Department of Transportation measured the amount of chemicals left on the roadway after a spinner application of dry materials found that nearly 40 percent of the materials left the roadway after application and landed on shoulders or in ditches due to bouncing, where it offered little help with melting snow and ice on the road surface and became the runoff that damages the environment.
Midwest Use of Salt Brine Proves More Effective Than Dry Road Salt
Midwestern cities successfully use a liquid salt brine solution as both a pre-wetting agent for dry materials and as an anti-icing agent for the proactive treatment of snow and ice. In the winter of 2002-2003, the Iowa Department of Transportation used over seven million gallons of brine, and today all of Iowa DOT’s snow plow trucks are equipped with units that pre-wet dry materials at the spinner. For anti-icing, liquid salt brine is placed on the roadway surface prior to a snow or ice event to help prevent snow and ice from bonding to the pavement.
European Studies Show Pre-Wet Road Salt Remains on Roadway
Studies conducted in Switzerland and Germany that measured the amount of dry chemicals that remained on the roadway after vehicle movement found that, after 100 vehicles, only 20 percent of the dry chemicals remained. When the chemicals were pre-wet, after 100 vehicles had passed, 80 percent of the materials remained on the roadway surface.
