Work starts May 24 to alleviate congestion by widening a short section of Interstate 5 in downtown Seattle where the freeway reduces down from three lanes to two, considered the worst bottleneck in the state.
“This project is designed to improve traffic mobility through downtown Seattle by removing a bottleneck at Seneca St.,” says Shawn Wendt, Washington State Dept. of Transportation project engineer. “This project will slightly widen about 1,500 ft of northbound I-5, allowing us to make the exit-only lane to Seneca a through-lane. This will mean three through-lanes where currently there are only two.”
The additional lane comes by replacing existing barriers, rails and curbs with a thinner barrier while reconstructing the asphalt shoulders with concrete and then restriping the roadway. MidMountain Contractors won the $27.4-million bid to remove and construct bridge barriers, install sign bridge foundations and sign bridges, pave asphalt and concrete and restripe the roadway.
The section of the interstate—designed in the 1960s—carries about 100,000 vehicles each day and causes both traffic backups and congestion-related collisions, according to WSDOT. In the current structure, the left Seneca St. exit-only lane turns into an off-ramp. The plan rebuilds the existing lane to add a third through-lane after the Seneca off-ramp. This third lane will remain open to all vehicles and for those using the exit.
To create a seamless transition to the existing four lanes of traffic after the Cherry St. on-ramp, crews will add an auxiliary lane from the Cherry St. on-ramp, which will end as an exit-only at Olive Way. The Cherry St. on-ramp will also gain ramp meters.
The project also adds a second lane to the Dearborn/Interstate-90 on-ramp to northbound I-5. Both lanes will have ramp meters.
WSDOT expects the work, largely done at night, to complete construction in fall 2022.