January 9, 2023

3 design-build teams to compete for $900M Portage Bay Bridge

Images from WSDOT [enlarge]

The new bridge will actually be two side-by-side structures.

Three design-build teams will compete for a big highway project in Seattle that promises to keep the winner busy for the next seven years. This project will replace the aging Portage Bay Bridge that carries part of state Route 520 and build a landscaped lid over the highway southeast of Roanoke Park. The contract is estimated at $725 million-$900 million.

The teams are: a joint venture of American Bridge Co. and Aecon; Skanska USA Civil West; and a joint venture of Kiewit along with Stacy and Witbeck.

The state Department of Transportation's project website says the existing bridge dates to the 1960s, is near the end of its functional life, and could fail in a severe earthquake.

WSDOT says the project will replace the existing bridge with two new parallel variable-depth segmental box girder bridges. It also will replace the existing eastbound highway off-ramp to Montlake Boulevard East, as well as the existing 10th Avenue East and Delmar Drive East bridges over the highway with the new Roanoke lid bridge. Work will include installation of about 75 retaining walls, landscaping and a reversible ramp gate system.

The new bridges will have three lanes, with a transit/HOV lane in each direction. One of the spans will also extend the cross-lake bicycle/pedestrian trail across the bay to the new lid park. A shared-use tunnel will be built under 10th for the trail, as well as a trail crossing bridge over Interstate 5 at Roanoke Street.

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A large central lawn is envisioned for the Roanoke lid.

Early conceptual designs for the Roanoke lid show extensive green space with a prominent central lawn and areas for seating.

WSDOT plans to publish a request for proposals notice on Jan. 23, and then award the design-build contract on Aug. 31. Construction would start in spring 2024 and continue into late 2030.

This project will connect to road improvements underway in the Montlake area that include a second landscaped lid over the highway. Both are part of the $2 billion “Rest of the West” program that is building improvements to Route 520 from Lake Washington to I-5. These improvements are funded by the 2015 Connecting Washington and 2022 Move Ahead Washington transportation legislation packages.