US 101 - S of Cosmopolis - Stabilize Slope

Project news

  • Construction to stabilize the hillside could begin late summer 2021. Travelers between Aberdeen and Raymond will see the highway reduced to a single lane through late summer of 2022. 
  • Maintenance 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 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 Mother Nature had other plans. On Jan. 24, 2020, crews discovered more than 12 inches of roadway settlement and reduced the highway to a single lane for safety purposes. Crews recently corrected another unstable slope less than 1,000 feet away during the summer of 2020.

Geotechnical engineers surveyed the site and recommend installing soldier pile walls to futher stabilize the hillside. Previous lower-cost repairs have proven to only last one season and not address underlying causes. This solution offers a more permanent repair to restore both lanes and fully reopen the highway in a safe manner for travelers.

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


  • Late April 2021: Contract advertised
  • June 2021: Construction contract awarded to Quiggs Bros., Inc,
  • Late 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