Date:  Monday, June 23, 2008

Contact: Jamie Holter, WSDOT Communications, 206-440-4698

ENUMCLAW – An unstable slope under the Green River bridge on State Route 169 north of Enumclaw is showing signs of weakness. To maintain safety, WSDOT crews will close the entire bridge Tuesday, June 24, from 6 a.m. until dark (10 p.m.) to allow geotechnical experts to drill under the southbound lanes to assess the stability of the ground.

• SR 169 will be closed to all traffic between SE 400th Street and Auburn-Black Diamond Road, north of Enumclaw.
• Trucks and passenger vehicles will take a seven-mile-long signed detour route that passes west of SR 169. Drivers should expect the detour route to add five to 10 minutes to their trips.

“We know this is a big inconvenience to drivers who travel between Black Diamond and Enumclaw,” said Lorena Eng, WSDOT regional administrator. “But we are concerned about the stability of the slope under the south end of the bridge. We will keep traffic off the bridge until we are sure drivers can use the road safely.”

Tuesday at daybreak, WSDOT crews will close all lanes of the bridge and set up a drill rig to bore holes in the ground under the lanes. This new drilling data will allow WSDOT engineers to analyze the condition of the bridge and roadway foundations.

Once the drilling work and analysis is complete Tuesday night, the bridge will likely reopen to one lane of signalized alternating traffic with a reduced speed limit.

“Our biggest concern is the vibration from big, fast trucks,” said Gary McKee, WSDOT project engineer. “We can minimize the vibration by reducing the speed limit.”

• This one-lane closure will last until further notice and should result in three- to five-minute delays.
• WSDOT hopes to have an emergency contractor working on interim repairs by as early as next week. Preliminary estimates are that the road will be completely closed for up to two weeks for the interim repairs.

The interim work will improve the stability of the roadway. Crews will construct a short retaining wall in the most vulnerable area using “soil nails” and shotcrete, a spray-on concrete designed to help shore up unstable slopes. In the long term the entire unstable area adjacent to the highway will need to have a wall constructed alongside it. This long-term fix must be completed before the heavy fall rains.

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