Monday afternoon's traffic backup on westbound Highway 16 was caused by a damaged expansion joint near the tower on the west side of the Tacoma Narrows Bridge, according to the state Department of Transportation.
Maintenance crews closed the right lane of traffic on the bridge about 2 p.m. so they could put a 3/4-inch steel plate over the damaged joint.
That caused a backup that stretched along Highway 16 and past the Tacoma Dome on Interstate 5.
"We never plan to do work in the afternoon on the Tacoma Narrows Bridge," said Lloyd Brown, a transportation department spokesman. "But this situation required immediate attention. In the best interest of the public and of the bridge, we just couldn't wait any longer."
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Brown said motorists can expect a bump for the next few days when traveling over the steel plate, which is about 10 feet long. The plate might remain on the bridge for as long as a week, Brown said, while crews do emergency repairs.
Motorcyclists are advised to use the left lane on the bridge to avoid the plate, because the change in road surface can endanger them, especially in the rain.
The Transportation Department also is asking drivers of large trucks to use the left lane to reduce wear and tear on the damaged joint.
Rob Carson: 253-597-8693