Blunder caused floating bridge to sink in 1990 storm

portion of floating bridgeThe rebuilt Lake Washington Floating Bridge opened for traffic 23 years ago this week, closing the chapter on a construction blunder that left Seattle with an I-90 bottleneck for nearly three years.

Nasty weather pounded Seattle during Thanksgiving week 1990, a time when the 50-year-old floating bridge – formally named the Lacey V. Murrow Bridge – was undergoing renovation. A new, wider I-90 floating bridge had opened in 1989 adjacent to the existing span, which was slated to carry eastbound traffic once repairs were complete.

floating bridge before grand opening The new 1989 bridge was a big deal for commuters, lessening I-90 congestion. When I shot this photo just before its grand opening, no one foresaw that the 1940 span, on the right, was doomed.

Much of Western Washington suffered flooding around Thanksgiving 1990. The PEMCO Storm Index ranks it as the 17th-worst storm in company history based on paid losses for 773 claims. (As a sidenote, just 23 days later, the No. 5-worst storm hit the Seattle area with 10 inches of snow, high winds, and single-digit nighttime temperatures.)

view of floating bridge after storm from Mt. Baker Ridge High winds and rain pounded the region as renovation workers vacated the old bridge to head home for Thanksgiving weekend. And someone neglected to seal large access holes that had been cut in the sides of the bridge's mid-lake pontoons.

Wind-whipped waves crashed into the holes as rain fell in torrents. Sunday morning, workers found the pontoons nearly submerged. One by one they tilted, snapped off, and sank to the bottom of Lake Washington. (See photo, courtesy WSDOT.) As they sank they also sliced the cables that anchored the new I-90 span in place.

portion of bridge near Mt. Baker Beach That week I drove to Mt. Baker Ridge to view the carnage. With so many of the new bridge's anchors severed, tugboats were on duty 24 hours a day, gently pulling the bridge cables southward to counteract wind and waves and hold the span stationary. (See top photo.)

Parts of the old bridge did not sink. They were corralled and moored near Mt. Baker Beach, alongside Lake Washington Boulevard just south of I-90. I shot one photo that captured workers as they crawled inside the infamous inspection hatches.

workers at bridge inspection hatches On Sept. 12, 1993, the I-90 eastbound replacement span opened, and the floating bridge was whole again, much to the relief of Mercer Island residents and Eastside commuters.

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