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Emergency repairs complete on SR 520 floating bridge

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Date:  Saturday, March 10, 2012

Contact: Andrew Richardson (SR 520 Program Office Communications), 206-660-5924

Crews replace second damaged anchor cable connection

SEATTLE – Emergency underwater repairs to a second damaged State Route 520 floating bridge cable connection found on Friday were complete by this afternoon.

On Saturday, March 10, divers removed and replaced a broken bolt and damaged pin on the southeast anchor cable, an operation made more difficult because the work took place in water 60 feet deep.

All work on the damaged anchor cable connections is now complete.
As part of routine bridge inspections on Thursday, March 8, Washington State Department of Transportation bridge engineers first discovered a damaged pin connection on the west end of the floating bridge. The pin is one of 58 that tie the 1.5-mile-long floating bridge to the Lake Washington lakebed. Working in 30-foot deep water, divers repaired that connection by Friday afternoon.

As a precaution, bridge engineers inspected three other similar anchors and found the same problem on one additional connection at the east end of the bridge. Two other locations were inspected and did not have the same damage.

“Our crews finished the work before the storm comes ashore on Sunday, which is great news,” said WSDOT Bridge Superintendent Archie Allen. “We’re looking at gusts of 35-40 miles per hour on the lake. Those are the kinds of winds that put pressure on these pins.”
 
One-third of the floating bridge anchor cables are inspected every two years, and 15 of the 58 were replaced in 2010. Corrosion was initially suspected as the cause of the damaged pin connections. While a final determination is pending, bridge engineers now say it appears that the steel hardware connections were bent by forces produced by wind and wave action on the lake.

Immediate repairs were necessary because engineers said connecting pins tying together anchor cables and anchors already had slid partially out of position. If a pin was forced completely out, separating the bridge and cable from the anchor on the lakebed, it would reduce the bridge’s ability to withstand large storms.

Repair work is preliminarily estimated to cost up to $60,000.

SR 520 construction closure reminder

  • The bridge remains closed for prescheduled weekend construction. Construction crews are demolishing an overpass in Medina and digging huge trenches across highway lanes in several locations on the Eastside throughout the weekend.

During the closure, bridge maintenance crews also performed maintenance work on the drawspan.
 
Eastside demolition work continues through 5 a.m. Monday, March 12.

Closure details at a glance

  • Mainline SR 520 and all connected ramps between Montlake Boulevard in Seattle and I-405 in Bellevue remain closed through 5 a.m. Monday, March 12
  • The 108th Avenue Northeast on-ramp to eastbound SR 520 will remain open to traffic.
  • Two sections of SR 520 will remain open to traffic: I-5 to Montlake Boulevard and areas east of I-405.

Closure information and detour maps are online. Night work is planned, and residents near the work zone are likely to hear construction noise. Weekend closure details are available at www.wsdot.wa.gov/Projects/SR520Bridge/WeekendClosures


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