Project overview
This stretch of roadway, often referred to as “Cosi Hill,” sit on a pre-historic landslide and suffers from chronic roadway settlement. Heavy rains triggered the roadway to drop more than five feet.
Crews reopened the highway to two-way travel on Friday, May 20. Final roadway striping and fence installation will occur through early June.
What to expect
This project is now complete.
On January 24, 2020, crews discovered more than 12 inches of roadway settlement and reduced the highway to a single lane for safety purposes. Since then, the roadway has dropped more than five feet.
US 101 near Cosmopolis has a history of reoccurring landslide activity beneath the roadway due to a chronic unstable slope. Over the years, WSDOT has invested millions of dollars into the hillside but unfortunately, heavy rains and rapidly changing weather events have moved the earth below the highway.
WSDOT conducted a thorough investigation of the site. Due to the frequency and severity of slide activity, a careful approach was required. WSDOT hydraulic, geotechnical and transportation experts collaborated to produce a solution that would withstand significant movement after heavy rains. Design engineers decided to implement a proven approach to this long-term fix by installing soldier pile walls to further stabilize the hillside. Crews will secure 45 steel beams roughly 43 feet into the ground, lined up one by one to imitate a line of soldiers. WSDOT implemented this type of solution in a previous slope stabilization project in 2015 along US 101 at Rock Crusher Hill.
Previous low-cost repairs have proven to only last one season and did not address the underlying causes. This solution offers a permanent repair to restore both lanes and fully reopen the highway in a safe manner for all travelers.
