How does deicer work?

An ODOT snowplow keeps the flow of traffic going through a winter storm on I-5's Siskiyou Pass... ROY MUSITELLI PHOTO/2-21-07

Everett Carroll kicked into gear when a tractor-trailer jackknifed on Interstate 5's Siskiyou Pass during a February snowstorm. The transportation manager for the Oregon Department of Transportation, who already was patrolling the pass in the blizzard with his crew, passed the scene and made a quick assessment, calling out on his radio to stop all northbound traffic at the first mile marker and close the northbound lanes.

"Now the clock starts ticking," he said. "I've got an hour to get this thing open."

The clock's ticking because every hour the interstate is shut down costs about $30,000 in vehicle delays alone, not counting lost business, ODOT officials say.

"You start really impacting the economy," he said. "It's a big deal to keep this interstate open."

Within minutes he ordered crews to push the tractor-trailer to the side and have deicer-plows and sander-plows hit the road.

A diagonal convoy of three plows, two equipped with sanders and the middle one equipped with deicer, took to the freeway summit to clear snow and ice from the pavement.

Another convoy of three plows formed on the southbound lanes, and the six plows, three and three, looped around the summit a couple rounds. Within 45 minutes, Carroll made the call to re-open the road.

ODOT attributes the speediness to deicer.

"The deicer has completely changed the way we manage the Siskiyou Pass and many of our snow regions," said John Vial, ODOT's interim regional manager for southwest Oregon. Before deicer, snow would pack on a road resulting in day-after-day of chain requirements until the weather warmed up. "We can't stop it from snowing, but we can prevent that snow from bonding to the road."

ODOTs deicer trucks, or snowplows equipped with a large tank on top filled with a diluted magnesium chloride compound, spray the liquid onto the road, preventing the bond between the pavement and the snow. The compound also includes a rust and corrosion inhibitor to protect vehicles, bridge structures and utility lines.

ODOT officials say it has much less of a negative impact on the environment than does regular salt (sodium chloride). Crews apply it at varying rates, usually from 15 to 40 gallons per lane per mile, depending on the severity of the storm and road conditions.

The road surface can be pretreated with the liquid prior to the storm hitting as long as temperatures are below 40 degrees. Occasionally when temperatures have been above 40 degrees, the compound has made the roadway slick, say officials.

ODOT's been using the product about 15 years, said Carroll.

Vial said many years ago ODOT decided not to use rock salt on the roadways because of the damage to bridges, concrete pavement, vehicles and the environment, though the surrounding states all use rock salt as one tool to fight icy pavement. Longtime ODOT employees don't recall ever using rock salt.

Allen Walters, who will drive a deicer-plow for 12-hour shifts in a snowstorm, drives around a five- to 10-mile stretch at the summit, making four rounds in an hour.

"Our mission is bare pavement," said Walters, who monitors the air and road surface temperatures from a gauge in his truck. He said the traffic actually spreads the liquid and keeps the surface ice free.

"It's all risk management up here," he said. "You take away the risk, there's less to manage."

Walters, who's been plowing roads for ODOT for 22 winters, said he's seen the traffic volume get worse over the years, not just in numbers, but with distracted and aggressive drivers. With all that, the deicer compound is doubly welcome.

"I think it's probably the most valuable tool that ODOT has gotten since I've been here," he said.

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