What’s up with the I-405 bridge to nowhere in Bellevue?

May 11, 2023, 4:54 AM

I-405 bridge...

There's a mysterious bridge over I-405. (Photo from King County)

(Photo from King County)

The new bridge over Interstate 405 (I-405) in south Bellevue looks like a bridge to nowhere. Is it part of the freeway widening or something else?

I’ve been watching the construction of this bridge for months. It’s over southbound I-405, just south of SE 8th Street. It doesn’t seem to be attached to anything, and it appears to be a dead-end on the hillside on the left side of the freeway.

I figured it had something to do with the ongoing widening of the freeway, but it just didn’t look right or make sense to me. I found my way to King County’s Curt Warber, the manager of the Eastrail Project for King County Parks, for an explanation.

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“You’re not the only person who has been confused by that new bridge because people drive under it and look on both sides and say ‘there’s no road there, what is happening with that bridge,'” Warber said.

This bridge is a part of 26 miles of new trails being built along the former Burlington-Northern Railroad line from Woodinville to Renton.

The train used to run right through the middle of I-405 there. It went under the northbound lanes and over the southbound lanes.

“That is why 405 is split there, why there’s a northbound split and a southbound split so the train could make its way through,” Warber said.

Those of us who have been here for a while will remember that you drove through a tunnel on southbound I-405 at that spot. It was removed in 2008 during the last I-405 widening project.

“They took out that old Burlington Northern train tunnel, but they had an agreement that when the time was right, they would build a new pedestrian and bike over crossing over the highway to reconnect it,” Warber said.

And that’s what this is. This will provide a trail that crosses the freeway.

“Until we get this thing open, nobody has a good sense of what’s going on up there between the northbound and southbound lanes, but there’s a way to sneak through there,” Warber said. “It’s going to be a lovely trail when we get it done.”

And I think what’s confusing many people, including me, is the size of this bridge. It is a lot bigger than a typical bike and pedestrian bridge, at almost 30 feet wide.

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“We also need to be able to get in there with dump trucks and backhoes and do ditch maintenance, and in 20 years, we’re gonna have to get in there with a paver to repave it,” Warber explained. “We own these trails forever, so we really need to be able to get in there with big construction equipment and fix that trail when needed.”

This trail expansion is also part of what drivers have been seeing along I-405 from the VMAC to Coal Creek Parkway, where the Washington State Department of Transportation (WSDOT) is building two-and-a-half miles of trail.

This project will also include the paving of the beautiful wooden trestle that crosses SE 8th Street. The trail will put you up on top of that.

The bridge over I-405 will be finished this year, but the trail in the area won’t open until late 2025 or early 2026, as work to connect the trail to the trestle continues until then.

Check out more of Chris’ Chokepoints.


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What’s up with the I-405 bridge to nowhere in Bellevue?