(UPDATE: WSDOT announced on June 11th that this work is now set to start July 12th)

WSDOT has announced the dates for overnight closures required for major work on the northbound side of the 1st Avenue South Bridge – starting four weeks from tonight. But the West Seattle “low bridge” will be open to all on the closure nights. Here’s the announcement:

Beginning July 6, people crossing the northbound State Route 99 Duwamish River Bridge, also known as the First Avenue South bridge, after dark will have to plan for up to 14 nights of detours. Southbound SR 99 will not be affected.

Contractor crews working for the Washington State Department of Transportation will replace 14 sections of steel bridge decking on what has become the main link between West Seattle and downtown Seattle since the closure of the West Seattle Bridge.

During northbound full closures, crews will detour vehicles and pedestrians beginning at 10 p.m. Sunday through Thursday nights. For each day of these closures, the bridge will reopen at 5 a.m. the following morning. No work will take place Friday or Saturday nights.

In addition to the full closures, people using the bridge should plan for overnight lane reductions and additional travel time during June.

Scheduling the bridge closures

The Duwamish River Bridge spans the Duwamish Waterway, a busy marine highway. When crews are working on the bridge, it cannot open for boat traffic. Keeping the bridge closed requires permission from the U.S. Coast Guard, which manages the waterway.

“This is important work to preserve the bridge. If we don’t do it now, we’ll have to wait until fall at the earliest,” said WSDOT Assistant Regional Administrator Messay Shiferaw.

Partnering with SDOT

WSDOT and the Seattle Department of Transportation are working closely to keep traffic moving during the northbound bridge closures. SDOT announced it will allow traffic to use the lower Spokane Street Bridge on nights the northbound Duwamish River/First Avenue South bridge is closed. This could change based on access needs for emergency vehicles. Other detours include the 14th Avenue South Park Bridge, Tukwila International Boulevard, East Marginal Way and Interstate 5.

“This is critical work that WSDOT must prioritize, but it comes at a time when many depend on the First Avenue South bridge more than ever. That is why we’ve worked with WSDOT and others to enable displaced traffic from the First Avenue South Bridge to use the Spokane Street Bridge as an alternative route across the Duwamish every night this work is being done,” said SDOT Director of Downtown Mobility Heather Marx, who also is the West Seattle High-Rise Bridge response lead.

Preserving the Duwamish River Bridge

The Duwamish River Bridge is an important transportation link between Seattle, West Seattle, Burien and points south. Fourteen of the 26.5-foot-long, 6-foot-wide steel deck grids need to be replaced. It takes a few hours to replace each one. During this work, all lanes must be closed for the safety of the people working on the bridge and the traveling public.

Replacing the decking during scheduled closures at times when there is less traffic will keep the bridge in good condition and avoid emergency repairs.

If all 14 nights are needed, that would be Monday night, July 6th through Thursday night, July 9th, plus Sunday night, July 12th, through Thursday night, July 16th, and Sunday night, July 19th, through Thursday night, July 23rd.