PLAN AHEAD Both directions of SR 18 to close August 15-18 over Tiger Mountain summit

WSDOT announces a full closure of SR 18 over Tiger Mountain summit from 9 p. m. on August 15 to 5 a. m. on August 18 for construction and maintenance work.

Both eastbound and westbound lanes will close between I-90 and Issaquah-Hobart Road, with local traffic allowed only to Southeast 104th Street. Freight traffic should utilize I-405 and I-90, as Issaquah-Hobart Road is unsuitable for semi-trucks. Contractor crews will advance work on new lanes of SR 18, which is part of the I-90/SR 18 Interchange Improvements project aimed at widening the highway. This project includes leveling new lanes, milling asphalt, and installing guardrails. Maintenance crews will also address guardrail damage and improve sign visibility during the closure.

The combined efforts aim to limit future closures while enhancing safety and traffic flow through the corridor. The new lanes are expected to integrate with the recently opened diverging diamond interchange upon completion in fall 2025.