Project News

Flatiron-Lane Joint Venture Completes Main Street Bridge Demolition and Places First Bridge Girders

I-405 Bellevue road section after the Main Street Bridge had been demolished

Since late 2019, Flatiron-Lane Joint Venture has been working with Washington Department of Transportation (WSDOT) to enhance the I-405 highway in King County, Washington, as part of the I-405 Renton to Bellevue Widening and Express Toll Lanes Project.

The project has recently hit multiple milestones:

Main Street Bridge Demolition

From Friday, June 17, through Monday, June 20, the project team utilized a 54-hour full highway closure of I-405 to completely demolish the Main Street Bridge overpass in Bellevue, which enabled the upcoming highway widening work.

Watch the time-lapse video for a recap.


With the old Main Street Bridge out of the way, the crews are currently forming the abutments and columns, with the first girder set scheduled for mid-August.

With the stakeholders’ needs in mind, the project team has an aggressive schedule to construct a new bridge and open the replacement bridge – two lanes must be opened by Nov. 15 to minimize disruption to the public.

The new bridge will have four traffic lanes like the old bridge, but will add a larger sidewalk and new bike path on the north side, with a new multiuse path and planter on the south side.


Column rebar for the new Main Street Bridge
Abutment rebar for the new Main Street Bridge

Column and abutment rebar for the new Main Street Bridge


First Girder Set of the Job at May Creek

During the night of Monday, June 27, crews successfully set the four girders for the first phase of May Creek Bridge, which was the first of 24 girder sets for the project. Each girder weighed 100 tons and was placed via a tandem pick between a 550T and 300T crane.


Night operations to place the first girders at May Creek
Night operations to place the first girders at May Creek

Night operations to place the first girders at May Creek


Since there are no vehicle height restrictions under the bridge, the design team maximized the size of the girders – each girder is 8 feet tall and they were placed 12 feet on center. 

With the girders in place, the crew will work toward pouring the bridge deck in September 2022.


The new bridge will connect with the new I-405 alignment, and will carry all four lanes of the northbound traffic.


Additionally, at the south abutment of the May Creek Bridge, the crew is currently building up the embankment utilizing an MSE retaining wall with precast panels that will support the future northbound lanes.

Notably, as part of the environmental protection measures, May Creek will be restored to its wider profile from before the original highway construction, and large woody materials will be installed in the creek to improve the local salmon habitat.



Sound walls construction underway 

Located east of I-405, next to the northbound traffic, the first sound wall of the job is underway. This Sound Wall is a third of a mile long and measures 30,010 square feet. In total, the project includes five sound walls, that, once complete, will provide significant improvements to lessen highway noise in surrounding neighborhoods.



About the project

Valued at $710 million, the I-405 Renton to Bellevue Widening and Express Toll Lanes Project covers 14 miles of roadway, including 12 miles of express toll lanes. In total, more than 40 bridges will be replaced, widened or undergo rehabilitation as part of the project. The project will reduce congestion for drivers on I-405 by adding one new lane in each direction. 

Learn more about the project:

Previous Article
Upper Llagas Creek Project Tour: Tunnel being built under downtown Morgan Hill will control flooding
Next Article
Flatiron hosts first-ever women-only reception at Beaverdilly