A five-mile stretch of state Route 7 closed by a slide June 7 will remain closed through the summer, according to the state Department of Transportation.
The Eatonville-area closure extends from state Route 161 to Alder Lake.
Steep terrain and a still-unstable hillside are challenging experts as they assess how expansive the slide was and why it occurred.
A soil nail wall likely will have to be installed, said Kevin Dayton, the Transportation Department’s regional administrator. Such walls reinforce existing soil by installing threaded steel bars into slopes or cuts as wall construction proceeds from top down.
“It could be August before it is designed and ready to be constructed and October until it is completed,” Dayton said this week. “Until we know the hillside is stable, we won’t open the roadway.”
Unlike typical highway work, this project is more than 100 feet up from the roadway at an approximate 45 degree angle, spokeswoman Claudia Bingham Baker noted.
To assess the condition of the slide, Bingham Baker said, a geotechnical team drilled three holes up to 200 feet deep above the slide site to determine subsurface soil and bedrock conditions. It also installed instruments to measure any movement and ground-water conditions above the slide to help formulate a plan on how to stabilize it in the long term.
More drilling will take place next week within the slide mass to gather more data about the slide, Bingham Baker said.
In the meantime, a signed detour around the closure adds about 10 to 15 minutes to trips for approximately 1,600 drivers a email@example.com