The most popular question we get about our winter attack plans in the Portland area is also the easiest to answer.
Will we use rock salt on the roads if we get hit by a nasty winter storm?
Rock salt is now part of our winter arsenal, along with sand, de-icer, and plows. Salt is an effective tool, but like all of our winter tools, it has its limitations because it is not a perfect solution to all winter ailments.
We won't use rock salt every time it snows in the Portland area, but only when it's the right tool for the job.
Salt is versatile as it can be used to pre-treat roads before they get hit by winter precipitation, such as freezing rain. When using salt, in most cases, we'll mix it with deicer as it's spread on the road. The deicer — magnesium chloride — helps activate the salt and helps keep it stuck to the road.
Salt isn't as effective, however, as the temperature drops. At 30 degrees Fahrenheit, salt works quite well. We can see its impact within 15 minutes. But as the temperature drops, so does its usefulness. When it gets down below 20 degrees, salt can lose much of its effectiveness because the ambient temperature creates a situation where the snow or ice melted by the salt can quickly freeze back into ice.
We'll keep a particular watch this winter to see if salt would help on a few of our familiar Portland-area trouble spots. These include U.S. 26, the Sunset Highway, heading west up the hill from the Vista Ridge Tunnel, and Interstate 5 heading north up Breeze Hill from Oregon 217.
Whenever we use salt, we will do everything we can to minimize the environmental impact. In most cases, for example, we will use salt at the lowest application level necessary. Most often, we will spread salt in the Portland area at 100 pounds per lane mile, a minimal dilution, but we can increase that amount if conditions warrant.
Our needs are quite different from those of other cities. In Duluth, Minnesota, for example, city crews spread rock salt at 400 to 500 pounds per lane mile on the snow when the temperature is 25 to 30 degrees. Of course, they get a lot more snow, and it stays cold for a lot longer in Duluth than in the Willamette Valley.
Most of the salt ODOT uses goes on Eastern Oregon roads. In the winter of 2017-2018, we used 27,000 pounds of salt in the Portland area and 8,977,850 pounds in Eastern Oregon. That was 91% of our total salt use that winter.
Salt use is limited by our storage capacity. In the last few years, we've stored salt in the Portland area in 2,500-pound bags. But that's a slow and inefficient process to get salt where it's most needed. We have 13 salt storage sheds around the state, all outside the Willamette Valley.
Just this fall, we completed a new storage facility at our maintenance yard at Cascade Locks, which will be able to store nearly 2,000 tons of salt. This will allow us to get salt when needed in the Columbia River Gorge quickly. It's now the salt storage facility closest to the Portland area. But not for long.
ODOT may build as many as four new salt storage facilities in the Portland area in the next few years. These enclosed sheds can cost $400,000 each and are built to strict standards ensuring there's no impact on local water quality. Our salt stockpiles are stored indoors. Runoff collection systems are being installed around salt and sand stockpiles and truck-washing areas. Maintenance yard housekeeping practices are designed to minimize runoff.
Each of these winter tools has its strengths and weaknesses. The liquid deicer with a rust inhibitor that we use is effective both before and during a storm to inhibit ice from the bonding to the road surface. The deicer, too, has temperature limitations. Sand provides better traction, but it takes three to five times as long to pick it up as it did to put it down on the road. Plows are effective, but are limited in their ability to break up ice packs.
Each storm is different, so it's hard to say where salt may be used. The best advice is to expect any of these tools — sand, plows, deicer, and yes, salt — may be needed before, during and after a winter storm.
Kris Strickler is ODOT's deputy director. The Oregon Senate will soon consider whether to confirm his nomination as ODOT director.
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