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Tuesday, July 03, 2012
Lisa Copeland, WSDOT Communications, 360-357-2789 (Tumwater)
Troy Cowan, ARA for Maintenance & Operations, 360-357-2612 (Tumwater)
EATONVILLE – Steep terrain and a still-unstable hillside are challenging geotechnical experts as they continue to assess a landslide last month that closed a 5-mile stretch of State Route 7 in Pierce County.
Shortly after the slide on June 7, engineers began investigating the site to determine how expansive the slide is and why it occurred.
Unlike typical highway work, this project is more than 100 feet up from the roadway at an approximate 45 degree angle. To assess the condition of the slide, a WSDOT geotechnical team drilled three holes up to 200 feet deep above the slide to determine subsurface soil and bedrock conditions. They also installed instruments to measure any movement and groundwater conditions above the slide to help formulate a plan on how to stabilize it in the long term. Next week more drilling will occur within the slide mass itself to gather more data about the slide.
Kevin Dayton, WSDOT regional administrator, said it is likely a soil nail wall will have to be installed. Soil nail 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.” he said “Until we know the hillside is stable, we won’t open the roadway.”
In the meantime, a signed detour that adds about 10 to 15 minutes to trips will help navigate about 1,600 drivers a day around the closure.
Real-time information about SR 7 or any state highway is available by dialing 511, signing up for email/text alerts via the Web or visiting WSDOT’s Travel Alerts page.
Hyperlinks within the news release:
• WSDOT Web site http://www.wsdot.wa.gov/
• WSDOT’s Travel Alerts page www.wsdot.wa.gov/traffic
WSDOT keeps people, businesses and the economy moving by operating and improving the state's transportation systems. To learn more about what we're doing, go to www.wsdot.wa.gov/news for pictures, videos, news and blogs. Real time traffic information is available at http://wsdot.wa.gov/traffic/ or by dialing 5-1-1.
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