Oso Landslide Assessment

CLIENT Snohomish County

Location Oso, WA

The Oso landslide flowed across the Stillaguamish River valley burying a neighborhood, resulting in 43 fatalities, and blocking the Stillaguamish River.

Shannon & Wilson provided expert witness services and assessed factors contributing to the rapid failure of this 10 million cubic yard landslide. 

We performed geologic reconnaissance, reviewed historic data, reviewed data from new explorations, performed laboratory tests, and evaluated groundwater information. We provided our interpretation of the site geology and factors contributing to the landslide in expert reports and depositions.


Stan Boyle
Senior Vice President

Hollie Ellis

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