US 101 - N of SR 107 - Stabilize Slope

Project news

  • COVID-19 construction effects
  • Weather permitting, at 4 a.m. Monday, June 1, contractor crews will close a 3.6 mile stretch of the highway between Blue Slough Road and State Route 107. The highway will remain closed through 3:30 p.m. Friday, June 5 for pavement repairs. Once the work is complete, traffic will resume to two-way driving conditions. The slope stabilization project is expected to be complete later this summer.
  • WSDOT is assessing a second slide zone roughly 1,000 feet away (not part of this project) where nearly 12 inches of roadway settlement was discovered on Jan. 24, 2019. An emergency repairs contract is currently being prepared, however a timeline has not been shared at this time.
  • Travelers are encouraged to sign up for Grays Harbor County maintenance and construction email alerts.

Needs & benefits

Why is WSDOT stabilizing a slope on US 101 north of the SR 107 interchange in Cosmopolis?
A stretch of US 101 near milepost 79 sits on a pre-historic landslide and has experienced chronic roadway settlement, leading to repeated lane closures. As a result, maintenance crews have repeatedly patched the roadway through the area, but additional geotechnical earthwork is required for more permanent repairs. Those temporary fixes have proven to only last until the next heavy rainstorm hits.

The End Result
To stabilize the hillside under the highway, contractor crews for WSDOT drilled shaft columns up to 50 feet into the earth. About 600 shafts form a buttress to support the roadway. The rock-filled shafts help hold the hillside in place, reducing the potential for the roadway settlement. Finally, crews will reconstruct and repave the roadway.

Project Benefits
Slope stabilization of “Cosi Hill” is intended to reduce the potential for slide-related closures at this location. This work also is expected to reduce maintenance costs associated with regular leveling, patching and repaving the road.


  • Spring 2019: Project advertised for competitive bids.
  • May 10, 2019: Contract awarded to Rognlin's Inc. 
  • Summer 2019-Fall 2020: Construction
  • Late summer 2020: Most work complete.


Financial Data for PIN 310121G
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $10,018
CWA $0
Total $10,018


Karen Boone
Aberdeen Project Engineer 

Tina Werner
Media Relations

US 101 Cosi Hill Thumbnail

US 101 Cosi Hill current condition
Current condition