Nearly 300 feet of damaged guardrail will be torn out and replaced this weekend, necessitating the closure of a four-mile stretch of westbound State Route 18 between Interstate 90 and the Tiger Mountain summit.

Washington State Department of Transportation crews will close westbound SR 18 at 6 a.m., Saturday and reopen it at 2:30 p.m. Eastbound SR 18 will remain open for drivers who want to reach I-90 from the west or the trailhead and parking area at the Tiger Mountain State Forest summit.

Drivers heading westbound to Maple Valley, Auburn and other destinations south and west should detour to Interstates 5, 405 or use other local routes.

The guardrail needs to be replaced and new support posts installed after they were seriously damaged by a semi-truck during the January snowstorm. Crews must completely close the westbound direction because crews cannot safely alternate traffic at this location due to the narrow roadway and semi-trucks might have difficulty stopping on the steep grade.

Updated closure information is on the WSDOT What’s Happening Now page.