SEATTLE - Officials with the Seattle Department of Transportation told the city’s transportation committee Tuesday that an error in applying twice the proper rate of de-icer on Monday, Dec. 2, led to several car accidents on the West Seattle Bridge.
Steve Pratt, the SDOT director of street maintenance, said that staff made a decision the morning of Dec. 2 to pretreat several bridges in the city.
In looking at several forecasts that called for hail or sleet from 1-3 p.m. and freezing temperatures around 5 p.m., Pratt said, “We thought in order to get ahead of that, based on prior experience, we would get that bridge treated.”
However, temperatures stayed warmer than expected that afternoon.
When SDOT applied the de-icer at around 11:30 a.m., Pratt said that the bridge surface was 38 degrees. He said that the manufacturer advises not using the magnesium chloride mixture in any situation above 40 degrees.
Furthermore, Pratt said that the operator had applied the de-icer at twice the appropriate rate.
SDOT Director Peter Hahn said, “The dial was set at 30 instead of 15.”
He added, “It’s really not that mysterious. The setting was wrong. An error was made.”
With double the rate of application, and the warmer-than-expected temperatures, the de-icer created a slippery surface where at least three accidents occurred.
“There are no two ways around it. We made a mistake,” said Pratt.
Joe Kessler, the Seattle police commander for the southwest precinct, told the committee that there were more accidents that did not get reported. Those drivers exchanged information.
Kessler said that when SPD sergeants arrived on scene, “They were slipping too. They realized there was a substance. So they notified dispatch.”
The West Seattle Bridge was shut down between 1 p.m. and 3 p.m., while SDOT crews applied sand over the surface in both directions.
Officials said that the rate of application was corrected for the other bridges that day.
This magnesium chloride mixture has been in use since January of 2011. SDOT officials said this was the first mistake of its kind in three years.
Any person who feels the damage to their car or personal injuries were a result of this mistake can file a claim with the city.
SDOT Spokesperson Richard Sheridan said that the driver and his supervisor will receive additional training on the application of de-icer.
He said that they will also modify their procedures for daytime applications of de-icer, by using dynamic message signs and having SPD officers warn drivers of the use of de-icer.