Cosi Hill roadwork and closures are returning, but on the other side of the hill

More road work on Cosi Hill could be coming, and more lane closures for travelers.

A slope stabilization project on US 101 south of Cosmopolis goes out to bid this month.

While the work to stabilize Cosi Hill on the north side recently finalized, this work will focus on the downslope leading to the SR 107 intersection.

WSDOT says that the hill 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 the land continues to slip away.

Geotechnical engineers surveyed the site and recommended installing soldier pile walls to further stabilize the hillside. 

WSDOT says that 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.

Maintenance crews continue to monitor the roadway for further settlement issues. Loads are restricted to no wider than 14 feet to provide clearance.

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

When construction on the south side of the hill begins, travelers between Aberdeen and Raymond will see the highway reduced to a single lane through late summer of 2022. 

To stabilize the hillside, crews will need to drill beams deep into the earth.

According to the WSDOT, this project is scheduled for a bid opening on May 26, 2021.


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