The Waynita Way NE Bridge over Sammamish River Seismic Retrofit Project proposes to seismic retrofit the existing 160-ft long vehicular bridge built in 1947 which carries about 11,500 vehicles a day on a key North-South corridor. The roadway width on the bridge is 26-ft with a 3-foot-wide sidewalk on each side of the bridge. The bridge superstructure is comprised of 4 simple spans of steel girders with a cast-in-place concrete deck. Each span is separated by an expansion joint. The original bridge substructure consists of timber crossbeams supported on double rows of timber piles for the intermediate piers, and concrete walls and footings supported on timber piles for the abutments.
The general aspects of this work involve seismic retrofit activities as described in this Proposal and as specified in the Contract Documents. The work includes replacing timber cross-bracing, adding steel members to bolster the bridge bearings, installing steel plates to the bottom of the bridge deck across expansion joints, installing bracing between crossbeam members and between corbels, and adding steel caps to the top of timber piles to better connect them to the crossbeams at the three intermediate piers.
In compliance with environmental permits, construction workers are to access the bridge substructure by either standing on work platforms that are suspended from the bridge deck or by standing on a barge or boat that is secured to the piers. If a barge or boat is used, it will be put in at an existing boat launch and will be positioned at the site so that it does not disturb any sediment. No clearing or grubbing will be required for the project. There is no anticipated excavation or geotechnical borings for this project. Ground disturbance will be limited to the staging area from equipment and stockpiled materials.
The total estimated cost for this project is in the range of $590,000 to $690,000. The number of working days for Physical Completion of this project is 90. Please contact Khin Gyi at or (425) 806-6826 for any questions regarding this project.
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