WSDOT’s new reversible transit connection between SR 520 and Mercer using I-5 express lanes one step closer to fruition

May 25, 2021
WSDOT awarded Walsh Construction a $69-million contract for the project, with construction scheduled to begin this summer.

The Washington State Department of Transportation’s (WSDOT) dedicated transit lane connecting State Route 520 and Interstate 5 express lane is one step closer to becoming a reality.

WSDOT says that Walsh Construction submitted the lowest bid for building the State Route 520 - I-5 Express Lanes Connection Project. The winning price proposal was $68.05 million and WSDOT plans to execute this contract in the coming weeks.

Six contractor teams submitted bids, which were opened May 19. The winning bid was six percent lower than the state’s engineering estimate.

“We’re excited to work with Walsh to build this next piece of the SR 520 Program,” said Program Administrator Omar Jepperson. “When complete, this project will provide a reliable transit link between the region’s major employment centers in Seattle’s South Lake Union and the Eastside via SR 520.”

The project will extend SR 520’s new transit/HOV system to I-5 by providing a dedicated, reversible connection between SR 520 and the I-5/Mercer Street interchange via the I-5 express lanes. The new reversible lane will work in concert with the I-5 express lanes. When the I-5 express lanes are operating in the northbound direction, the new ramp will connect to eastbound SR 520. The new ramp will connect westbound SR 520 vehicles to the I-5 express lanes when they are operating in the southbound direction.

Initially, only buses will use the connection. Later, when construction of the SR 520 - Portage Bay Bridge and Roanoke Lid Project is complete and a new lane is available to receive the connection, the reversible lane will also be open to carpools.

Construction is expected to begin this summer and wrap up in late 2023.

The contract includes:

  • Building a new, reversible transit/HOV ramp between SR 520 and the I-5 express lanes.
  • Restriping I-5 express lanes to retain the four existing lanes while adding a reversible transit/HOV lane between the I-5/SR 520 interchange and Mercer Street.
  • Modifying an existing ramp for reversible operations between the I-5 express lanes and Mercer Street.

Construction of this project is the second of four SR 520 projects that make up the Rest of the West improvements. The projects were funded in 2015 in the Connecting Washington funding package.