(WSB photo, Tuesday)
When WSDOT closed two lanes of the northbound 1st Avenue South Bridge after an inspection revealed problems, an update was promised by this Friday. Today, we have it – a repair plan starting with a three-day closure next Monday through Wednesday, and longer closures to come. Here’s the announcement from WSDOT:
The Washington State Department of Transportation will begin temporary repairs on the northbound State Route 99 First Avenue South bridge during a three-day closure of all northbound lanes from 5 a.m. Monday, March 9, through 8 p.m. Wednesday, March 11. Two lanes of the bridge were closed Feb. 18 after a bridge inspection identified cracks in the steel deck grates of the bridge in Seattle.
This repair effort is structured in three phases:
-Immediate stabilization and reopening of all northbound lanes
-Limited grate replacement in mid-to-late April
-Full northbound deck replacement in 2027The first phase of repairs must take place during daytime hours for both safety and efficiency. The temporary repair will allow all northbound lanes to reopen with a temporary speed limit reduction to 25 mph. The speed reduction will remain in place until the second phase of the repair is complete.
Phase 1: Stabilizing the bridge now (March 9-11)
During the March 9-11 full northbound closure, crews will modify existing grated panels and install steel plates over the cracked grates to restore safe vehicle access across all lanes. Welding and reinforcement work will strengthen the most affected sections of the bridge deck.
The temporary steel plating and reduced speed limit are intended to reduce stress on the deck and provide safe passage across the bridge until permanent grate replacements are installed.
This closure will occur immediately following a full weekend closure of northbound and southbound I-405 in Bothell on March 7-8. The sequencing reflects the urgency of the bridge repairs and the limited window available to complete the work before another full weekend closure of I-405 scheduled for March 13-16.
The bridge will remain operational for marine traffic but closed to vehicles during these repairs. Travelers will need to use alternate routes such as I-5 and I-405.
Phase 2: Replacing nine failing panels before summer (Starting mid-to-late April)
The next phase involves full replacement of nine steel grate panels inspectors deemed in the worst condition. Manufacturing these panels is underway and is expected to take approximately six weeks, with installation scheduled to begin as soon as they are delivered. This work will also require a full northbound closure of the First Avenue South bridge. This work is expected to start in mid-to-late April pending panel delivery and U.S. Coast Guard coordination.
WSDOT is executing an emergency contract and will work closely with the selected contractor to maximize efficiency while minimizing impact to travelers. An updated timeline will be shared in early April before work begins. WSDOT and the contractor will consider a series of full weekend closures as well as options for night work.
The goal is to complete the replacement of these nine panels before the 2026 FIFA World Cup begins in June, when hundreds of thousands of spectators will visit the greater Puget Sound region. Completing this work now ensures that SR 99 remains a viable route during a period when the transportation system will be in high demand.
Once this phase is complete, all northbound lanes will reopen at normal speeds.
Phase 3: Long term preservation work in development (2027)
Design is underway for a full replacement of the northbound bridge deck, with construction expected in 2027. This project will address broader needs and will require more substantial coordination with the U.S. Coast Guard and regional partners. More information will be shared on this phase of the project in early 2027.
About the First Avenue South bridge
The First Avenue South bridge is a moveable, double-leaf bascule bridge spanning the Duwamish River. Like a drawbridge, its two sections lift from the center to allow marine traffic to pass. When closed, the two halves meet to carry vehicles, transit and freight.
Because the bridge both moves and carries heavy daily traffic, it includes mechanical systems and specialized steel deck components that require ongoing maintenance and inspection. Areas near the center of the span experience the greatest stress. During its last full inspection, the bridge was rated in fair condition.
The First Avenue South bridge is part of a statewide bridge system with infrastructure operating beyond its intended service life. WSDOT often extends the life of these bridges through targeted repairs while larger preservation projects are being developed. That approach allows structures to remain in service, but it also means that when conditions change, crews must act quickly and sometimes close lanes or structures in the interest of public safety. Each time WSDOT must take this action highlights the critical need for investment in the preservation of our transportation system. Governor Ferguson proposed a $2.1 billion investment in preservation including $1.1 billion for bridges.
The bridge served as the main detour route across the Duwamish River when the West Seattle Bridge – which is a city-owned structure – closed 2020-2022.