US 101 - S of Cosmopolis - Stabilize Slope

Project news

  • US 101 travelers can expect to see the highway reduced to a single lane through summer of 2022 while crews drill beams into the ground to stabilize the hillside.
  • On Jan. 24, 2020, crews discovered more than 12 inches of roadway settlement and reduced the highway to a single lane for safety precautions.
  • A construction contract to stabilize the slope near milepost 78.3 will be available for competitive bids beginning spring of 2021.
  • This stretch of US 101 has a history of reoccurring slide activity beneath the roadway due to a chronic, unstable slope.
  • WSDOT invested millions of dollars correcting the area to keep the highway open for travelers. Crews recently corrected the first unstable slope 1,000 feet away from this location during summer of 2020.
  • Crews continue to monitor the roadway for further settlement issues. Loads are restricted to no wider than 14 feet to provide clearance.

Needs & benefits

Why is WSDOT stabilizing a slope on US 101 north of the SR 107 interchange in Cosmopolis?

US 101 south of Cosmopolis was reduced to single lane due to chronic roadway settlement beginning in January of 2020. The highway sits on a pre-historic landslide, resulting in repeated lane closures and delays for travelers between Aberdeen and Raymond.

WSDOT geotechnical engineers have surveyed and recommended a repair to correct the more than 12 inches of roadway settlement by installing soldier pile walls. Previous lower-cost repairs have proven to only last a single season and not addressed underlying causes. This solution offers a more permanent repair in an effort to restore two travel lanes to US 101.

The End Result
A stabilized roadway will help secure the hillside, reducing the potential for roadway settlement and repeated lane closures.  


  • Spring 2021: Contract advertised
  • Summer 2021: Construction begins
  • Fall 2022: Most work complete


Financial Data for PIN 310178F
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $5,345
CWA $0
Total $5,345


Karen Boone
Aberdeen Project Engineer 

Tina Werner
Media Relations