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520 bridge damaged in windstorm; repair will require closures
Seattle Times staff reporter
State bridge engineers say they must replace a part on the Highway 520 bridge damaged in the Feb. 4 windstorm and bridge closures are planned.
Engineers said they must replace the steel assembly that supports a guide roller under one corner of the east drawspan of the bridge. They said the damage was similar to what happened following a storm seven years ago.
"In 1999, after a similar storm, we experienced damage to one of the vertical guides," said DOT bridge preservation engineer Harvey Coffman. "Looking for the same kinds of problems this time, ultrasound testing results have turned up a small crack in a steel casting that holds one of the guide roller assemblies for the drawspan. It if isn't fixed and the casting should fail, the drawspan will not operate smoothly." He said the pontoon may even rock so drivers might think they hit something on the roadway.
He said the DOT has a spare assembly in stock, which weighs about five tons, and the installation will take place over two weeks.
Short closures are scheduled from 2 to 4 a.m. Thursday and Feb. 22. However, when the assembly is actually replaced, the bridge will be closed for 29 hours, from 5 a.m. Saturday, Feb. 25, to about 10 a.m. Sunday, Feb. 26.
The drawspan will not open for vessels over the next two weeks.
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