WSDOT outlines I‑5/170 Ninth Street interchange plan, schedules construction for 2029–2031

Laura, a project lead with the Washington State Department of Transportation, gave a detailed update on the I‑5/170 Ninth Street interchange improvements project and said, “The interchange project will improve safety and mobility at the interchange, by replacing the existing signals that are out there today with roundabouts.”

The project would replace the existing signalized ramp terminals with two roundabouts, replace the two bridges that carry I‑5 over 170 Ninth Street, raise I‑5 about 4–5 feet in the project area, lengthen the southbound off‑ramp, add ramp meters, build two 10‑foot shared‑use paths north and south of 170 Ninth Street, and replace a fish‑blocking pipe with an open‑channel stream that provides roughly an 18‑foot minimum opening beneath ramps and bridge spans. Laura said the project also includes drainage treatment, updated traffic technology, lighting and acquisition of property rights “as needed to just support the the.”

Why it matters: the corridor serves commuters, freight, event traffic for the county fairgrounds and an amphitheater, businesses and many residences;…