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SEATTLE — Crews working for the Washington State Department of Transportation (WSDOT) began seismic repairs on the 80-year-old historic SR 99 Aurora Bridge (George Washington Memorial Bridge) on Wednesday, June 1. The $5.7 million project, funded by a 2005 gas tax, is the third and final phase of a plan to strengthen the bridge to better withstand a major earthquake. An estimated 80,000 vehicles use the bridge daily.

Massana Construction won with the lowest contract bid, 30 percent less than the engineer’s estimate. Because Massana just completed the bridge’s new Aurora Avenue safety fence in February, the contractor is familiar with the structure.

The work focuses on14 concrete columns, 14 concrete girders, and four concrete cross beams and six steel trusses over land on the south and north ends of the bridge in Queen Anne and Fremont. No work is planned over water.

Mindful of the bridge’s spot on the National Register of Historic Places and designation as a city of Seattle Landmark, WSDOT engineers worked with seismic specialists at Washington State University to test a special fiber reinforced polymer wrap that will cover the north end columns. (Read more about the FRP jacketing process.) The columns are a unique cruciform shape distinctive of the 1930s when the bridge was built. Maintaining the period look and feel is important to the residents of Fremont and Queen Anne.

Project details
For this project crews will:
• wrap 14 columns in concrete covers and specialized jackets to prevent columns from failing in an earthquake;
• reinforce steel trusses and concrete girders;
• add bracing to support frames;
• replace or repair two expansion joints that allow the bridge to flex; and
• install bearings into the joints in the bridge deck that allow the bridge to sway.

Construction plans
Most of the work will take place under the bridge, which means total bridge closures will be limited to just a handful of nights. There will be two-lane closures at night and single-lane closures during the day. Occasionally, crews also will close streets under the bridge to access to the structure. Local drivers and residents who use street parking will get advance warning.

Noisy work will include jackhammering and busting out old rivets in the steel truss, similar to work on the safety fence. Most of the noise will be during the day; however, there will be three nights during the 18-month-long project when crews will use jackhammers to remove concrete. Local residents will get advance warning of the work.

Construction should be complete by fall 2012. More information is available at www.wsdot.wa.gov/projects/sr99/aurorabridgeseismicretrofit.