Final pieces coming together on I-90 Sunset Creek fish passage project

By: Casey Conley

Much like a jigsaw puzzle, large-scale construction projects take shape one step at a time. Each interlocking piece builds on the last.

Taking that metaphor a step further, the full picture of the I-90 Sunset Creek fish passage project in Bellevue’s Factoria neighborhood is starting to come together.

Construction began on this multi-step project in early 2023. The expectation was that work would continue into 2027. We’ve reached a lot of milestones during the last three years. There are just a few more to go, and they are planned through 2026.

The most significant achievement so far is the construction of four bridges across Sunset Creek. Our contractor, Guy F. Atkinson Construction, built these new spans along I-90 and Southeast 36th Street.

The fourth and final bridge, constructed along Southeast Eastgate Way, opened to traffic in October 2025.

Final touches

People driving across the new Sunset Creek bridges can be forgiven for thinking the project is mostly complete. After all, the most visible pieces of this puzzle are now in place. But there is plenty of activity happening beneath those new bridges.

Since construction began in early 2023, contractor crews have built four new bridges across Sunset Creek.

Contractor crews are building concrete walls extending up to 50 feet below the freeway. These walls hold the steep hillside in place. The first phase of these walls is done, and work is underway on the remaining walls.

Contractor crews are currently building concrete walls that extend up to 50 feet below the freeway.

Once that’s done, we will remove the maze of culverts that previously carried Sunset Creek beneath nearly a dozen traffic lanes. These culverts prevent fish from swimming upstream.

We’re also planning important upgrades within Sunset Creek itself. Crews will construct a new stream channel running north-south between the bridges. We will place woody debris and other habitat improvements, giving fish a shady place to rest and stay safe from predators.

Then, we will reintroduce the stream into its new, open-air channel. This is one of the final pieces in this project. Depending on weather and other variables, we expect this will happen in early or mid-2027.

More work remains

We designed this project to minimize congestion and delays for people who live or commute along this section of I-90. We’ve had a healthy number of overnight lane and ramp closures over the last three years, but these occurred when traffic volumes were lowest. We’ll continue to have occasional overnight lane and ramp closures throughout the year as work enters the final stages.

Last spring, our environmental crews counted 43 juvenile coho salmon and 16 cutthroat trout in Sunset Creek near Southeast Eastgate Way. 

The eastbound I-90 HOV lane, which closed in spring 2023, will remain that way for much of the year. This closure makes space for crews to move construction material into the stream bed.

We’re planning more work along Southeast Eastgate Way in 2026. Crews began drainage and grading work in late March. We expect weekday single-lane closures on Southeast Eastgate Way near the new bridge to continue through much of 2026.

Improved fish habitat

The Sunset Creek drainage basin covers nearly 850 acres within the city of Bellevue from its source near Eastgate Park. There are chinook, coho, sockeye, steelhead and cutthroat trout in the stream.

Last spring, our environmental crews counted 43 juvenile coho salmon and 16 cutthroat trout in a small section of Sunset Creek north of I-90. The biggest fish was a cutthroat more than five inches long.

By the time we’re done, this project will open 1.65 miles of potential upstream habitat to salmon and resident fish.

More pieces to this puzzle

This project contains fish passage improvements bundled together into a single contract. Bundling work like this saves time and reduces construction costs.

Construction is now complete fish passage improvements along SR 203 south of Carnation, left, and SR 203 in Fall City. 

Later this year, three culverts that block fish passage on SR 161 in Federal Way and Milton will be replaced along tributaries to Hylebos Creek. We expect work in these areas to resume in early summer and wrap up in early fall. This part of the project opens a combined 2.2 miles of potential upstream habitat.

And in 2024 and 2025, we completed fish passages beneath SR 202 in Fall City and SR 203 to the north and south of Carnation. Taken together, these projects in east King County built three new bridge structures and opened a combined 3.4 miles of potential habitat.

Like a good puzzle, this project has taken time for the pieces to come together. But once the work is finished, we believe you’ll like the finished product.