SEATTLE -- The Washington State Department of Transportation wants to make sure commutes like that of November 22 never happen again during a snowstorm.
If you were unlucky enough to be traveling south bound on I-5 that evening, it would have taken three hours to travel the length of Boeing Field. Northbound I-5 wasn't much better -- a spun out bus, along with jack-knifed big rigs on the Duwamish curves put a cork in the bottle.
WSDOT is reviewing what went wrong that night and how to prevent a repeat, especially since this La Nina winter is just getting rolling.
KING 5 News has learned that even though dump trucks were salting and sanding freeways that day, they weren't putting down enough salt for the temperatures that were about to plummet.
The typical WSDOT truck spreads up to 350 pounds of salt and sand mixture for each mile of travel lane. At that concentration, Maintenance Manager Chris Johnson says roads should stay wet down to 25 degrees. But it got a lot colder that afternoon, down into the teens.
Johnson says at the rate of 500 pounds of salt and sand per mile, roads should stay wet down to 15 degrees, but the salt becomes less effective the colder it gets. According to Johnson, WSDOT trucks in Seattle didn't use that higher concentration before gridlock took over and kept trucks from getting around.
"It got ahead of us," says Johnson.
There are trade-offs in the equation. At 350 pounds per mile, a truck can cover 30 miles worth of lanes before having to reload. At 500 pounds they cover 20 miles and have to reload more frequently.
Already WSDOT has made changes by putting small to moderate size sanding boxes on incident response pickup trucks. With a Washington State Patrol escort, smaller trucks can better get through traffic and provide pinpoint treatment to trouble spots like the Duwamish curve.
This is the first time such small sanding boxes have been used and WSDOT considers the costs reasonable, from about $2,500 dollars for a model that plugs into a trailer hitch, to about $7,500 that takes up the full bed of a pickup truck.