UPDATED 4:20 P.M | The West Seattle Bridge reopened this afternoon, following nearby crashes that were blamed by police on road de-icer.
Three cars spun out on the curve next to the Nucor steel mill, where eastbound traffic turns downhill toward the high bridge, said Steve Pratt, road-maintenance director for the Seattle Department of Transportation.
The crashes happened shortly after a midday application of salt solution de-icer.
“The only thing I can assume is, perhaps the (road) deck is a little too warm,” Pratt said.
Pratt said the city was trying to treat the bridge corridor before tonight’s Seahawks game and afternoon rush hour, and SDOT was hearing reports that a cold front would reach the city by 1 p.m.
He was thinking about Nov. 22, 2010, when freezing rain stranded cars on the Alaskan Way Viaduct, and road crews couldn’t salt the road decks because the stalled traffic was blocking them. So on Monday, he said he wanted to get a jump on the forecast freeze.
“I’m going to put this in the category of ‘no good deed goes unpunished,’ ” he said.
City officials also blamed high car speed for the wrecks. The posted limit is 40 mph near the steel mill and 45 mph on the bridge.
Pratt, who was doing other work in West Seattle at the time, said he drove onto the high bridge from the Delridge Way onramp, trouble free. But when crashes began, the police closed the entire high bridge route, including the Delridge onramp, as an apparent precaution.
SDOT has used salt solution for more than three years and has never had a problem like this.
The de-icer used Monday is called FreezGard, an opaque brown liquid containing magnesium chloride. It takes five to 10 minutes to crystallize on the pavement, said Pratt. Meantime, it goes on slightly slippery, “particularly if vehicles are exceeding the posted speed limit,” said SDOT spokesman Rick Sheridan. Many years ago, the curve at the steel mill wasn’t treated at all, so that when vapor from the steel mill condensed, a sheet of ice invariably caused spin-outs on any frosty morning.
Usually, the city applies salt solution overnight. Just before noon Monday, the air was 43 degrees and the road deck 38 degrees, said Pratt.
He said the city will think twice before applying salt solution in the daytime. Another idea that’s been discussed is a rolling slowdown, where a vehicle behind the de-icing truck slows the drivers behind it for several minutes.
Crashes occurred between noon and 1 p.m. The bridge reopened to traffic in both directions around 3 p.m., after crews dropped sand to improve traction.
The city has applied liquid salt compound since December 2009, following the city’s slow ice response in December 2008 when SDOT under then-mayor Greg Nickels avoided salt, and some streets took days to thaw.