WSDOT: Diverging-diamond interchange at I‑90/SR‑18 to open this summer; more short closures planned

Washington State Department of Transportation officials told the Snoqualmie City Council on June 9 that the diverging‑diamond interchange (DDI) at Interstate 90 and State Route 18 will be placed into its DDI configuration this summer, and that the overall interchange‑widening project is expected to finish late in 2025.

The update, delivered by WSDOT public information officer David Rasback and Aecon project manager Kathleen Mahan, listed specific work completed during a recent five‑day closure and outlined additional short closures ahead. "SR 18 was closed for 130 hours. We had a maximum of 120 people working on the site at any one time," Rasback said, and he provided construction totals including 2,700 tons of asphalt, 250 cubic yards of concrete and 10,000 linear feet of striping installed during the closure.

Why it matters: the interchange project widens roughly 2.5 miles of SR‑18 to two lanes each way between I‑90 and Deep Creek, replaces bridges and builds new pedestrian and wildlife passage beneath the roadway. City officials pressed WSDOT on timing and traffic impacts because the route is a primary commuter and emergency‑services corridor for Snoqualmie…