That’s an aerial view of the trouble zone on the northbound 1st Avenue South Bridge, where the discovery of cracks in the bridge deck’s steel grates led to a 2-lane closure two weeks ago and, as announced Wednesday, will require a full replacement of the deck next year. In the meantime, a three-day northbound closure for stabilization work is planned next week, and we asked some followup questions today. The bridge is state-owned, so the Washington State Department of Transportation is responsible for it, and WSDOT spokesperson RB McKeon handled our questions.
The state inspects its bridges at least every two years, and this one would have had its regular 2-year checkup later this year, after a “fair” rating in 2024. But a crew was out looking at it in mid-February and discovered the cracks, making the decision to remove traffic from the two right lanes.
How will traffic be routed away from the NB bridge for next week’s Monday through Wednesday closure? McKeon replied:
During next week’s closure, all northbound SR 99 traffic will exit at South Cloverdale Street, cross the Duwamish River on 14th Avenue South and then travel north on East Marginal Way South, which reconnects with SR 99 north of the bridge closure.
The following on-ramps also will close from 3 a.m. Monday, March 9, through 8 p.m. Wednesday, March 11:
-First Avenue South to northbound SR 509
-West Marginal Way South to northbound SR 99
-Occidental Avenue South to northbound SR 99The First Avenue South Bridge Trail also will close from 5 a.m. Monday, March 9, through 8 p.m. Wednesday, March 11, for bridge repairs. Cyclists and pedestrians must follow a signed detour using the Duwamish Trail to the 14th Avenue South Bridge, where they can cross the Duwamish River then head north on East Marginal Way South to reconnect with SR 99.
Next week’s work will be one by WSDOT bridge-maintenance crews; the April work to replace 9 panels will be done by a contractor who hasn’t yet been chosen. The replacement panels are being made by Mission Critical Solutions in Pennsylvania, as part of Phase 2 repairs projected to cost $1.7 million. The timeline for that work is expected to be available in early April, McKeon told us, and they’ll be looking at the possibility of working during full weekend closures and/or nights to “minimize impact to travelers.” How Phase 2 will affect maritime use of the Duwamish River in that spot isn’t yet settled; WSDOT will talk with the U.S. Coast Guard.
Phase 3 – the full northbound deck replacement – is still in planning, but WSDOT expects to send it out for bidding in December. In the meantime, again, next week’s full northbound closure is