Weekend-long closures coming to southbound SR 529, starting Jan. 19

UPDATE 1:52 p.m. Monday, Jan. 29
Work on the SR 529 bridge project has been postponed. We will get word out when new dates have been set.

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By Tom Pearce

Maintenance and preservation are a big part of what we do at our agency. Among other tasks, we inspect more than 3,900 bridges – and when I say bridges, that includes overpasses – in the state at least once every two years. As you can imagine, that’s a lot of poking around, particularly in some tight spaces on some of those structures.

Last year during a routine inspection of the 97-year-old southbound State Route 529 Steamboat Slough Bridge just south of Marysville, our crews found about a dozen worn gusset plates, which connect steel beams. The bridge remains safe to use, but we reduced the speed limit to 25 mph last summer to lessen vibrations and wear.

This is one of the plates that will be replaced on the southbound SR 529 Steamboat Slough Bridge.

It’s taken time to hire a contractor and order replacement parts, but we’re ready to start that work now. In order to replace these worn plates, we’ll need a few weekend-long southbound SR 529 closures, the first of which begins at 11 p.m. Friday, Feb. 2. Southbound SR 529 will reopen at 5 a.m. Monday, Feb. 5. We’ll repeat the closures the weekends of Feb. 10-11 and 24-25, depending on weather.

During the weekend-long closures, people traveling from Marysville to Everett will need to use southbound Interstate 5. People still can get to the west side of SR 529 from northbound SR 529.

Why a full southbound closure?

We need to close the southbound SR 529 lanes because we need the bridge to be still as we remove the old plates and install the new ones. As you can imagine, any traffic on the bridge would create vibrations, which isn’t ideal when you remove a piece that connects the beams.

Once this work is complete, we should be able to return southbound SR 529 to its regular 55 mph speed limit.

Regular bridge inspections

While we check our bridges at least every two years, sometimes our inspectors see things that require more frequent inspections. Our bridge crews have checked the Steamboat Slough Bridge about every six months since 2022. This past summer, they determined we need to replace the plates, which were part of the original structure.

The southbound SR 529 Steamboat Slough Bridge, built in 1927

A little history

The southbound SR 529 Steamboat Slough Bridge is part of the original highway across the Snohomish River delta between Everett and Marysville. Opened in 1927 as part of US 99, the highway had one lane in each direction. The structure is a swing bridge, meaning it can rotate to open a channel for boats to continue upriver. For comparison, the SR 529 Snohomish River bridges have a lift span that raises a section allowing boats to pass.

In 1954, a separate road for US 99 northbound lanes opened, so the original road became southbound only. When US 99 was decommissioned in 1971, the road became part of the state system and was renamed SR 529.

More work on SR 529

The southbound Steamboat Slough work is part of a larger preservation project that also involves the northbound Steamboat Slough Bridge and the SR 529 twin bridges over the Snohomish River.

A four-month closure of the northbound SR 529 Snohomish River Bridge is the biggie for this project. Before we close the bridge this spring, our contractor crews will build a crossover between the northbound and southbound lanes north of the bridge. When the closure begins, the southbound SR 529 Snohomish River Bridge will be reduced to one lane in each direction. After crossing the bridge, northbound traffic will use the crossover to return to the northbound lanes. Our contractor is planning to operate a shuttle to move cyclists and pedestrians between Everett and Marysville.

In addition to the southbound Steamboat Slough Bridge closures, the northbound bridge also will have a couple of multi-day closures. During these, northbound traffic will detour via I-5.

With so much work to complete, this project will continue into 2025. We expect some challenges with traffic, but if you plan ahead and use an alternative, such as I-5, that will help those who need to use SR 529. Thanks for your patience!