information from WSDOT

A 15-day lane reduction on the southbound State Route 99 Duwamish River Bridge, also known as the First Avenue South bridge, will begin Thursday, March 4.

The bridge will be reduced to two lanes so contractor crews working for the Washington State Department of Transportation can repair bearings and steel beams that support the structure. Work does not affect the northbound bridge.

With the West Seattle Bridge closed, WSDOT Project Engineer Mike Askarian said people who use the SR 99 bridge to reach West Seattle, Burien, SeaTac and other locations will need to use alternative routes or allow extra travel time.

“There is never a good time to do this sort of work, but these repairs are necessary to keep the bridge in good condition,” Askarian said. “We have been watching the bearings that support the bridge for a couple of years. Last fall we found they had worn to the point where they need to be replaced. This is a challenging time for travelers with the West Seattle bridge closed, but doing this work now will prevent future damage to the bridge.”

WSDOT is working closely with the Seattle Department of Transportation to provide early notification about this project and trip-planning resources to keep traffic moving efficiently while reducing congestion, pollution and speeding.

What travelers can expect

The southbound SR 99 Duwamish River Bridge will be reduced from four to two lanes 24 hours a day for 15 consecutive days starting March 4. The work also will require four overnight closures between 10 p.m. and 5 a.m. – two early in the project and two at the end.

Travelers should consider avoiding the bridge, particularly during afternoon peak travel hours.  Alternative routes include East Marginal Way South Bridge, the Tukwila International Boulevard Bridge, Interstate 5 and the South Park Bridge.

Bridge work

During the lane reductions, crews from Massana Construction Inc. will replace bearing pads and repair some of the steel that supports the bridge. The bearing pads – masonry pads that the girder rests on – were part of the initial construction when the southbound SR 99 Duwamish River Bridge opened in 1996. These pads are worn out and need to be replaced. The pads allow precise setting of the elevation of the bridge’s roadway. 

During the first overnight closure, crews will lift the bridge deck a small amount to get to the bearing pads. When work is complete, crews will use the second closure to put the bridge back onto the new pads.