Implications of Preliminary Findings from the Nisqually Earthquake of 28 February 2001 on the Seattle Tacoma International Airport Third Runway – Embankment Fill and West MSE Wall Expansion Project

Notes

GeoSyntec Consultants submitted this letter to the U.S. Army Corps of Engineers and Washington State Department of Ecology on behalf of the Airport Communities Coalition, summarizing concerns about the Third Runway Expansion Project at Sea-Tac Airport in light of the Nisqually earthquake of February 28, 2001. The letter highlights damage to mechanically stabilized earth (MSE) walls and extensive liquefaction observed during the moderate earthquake, raising questions about the adequacy of seismic design ground motion criteria and FLAC computer analysis used for the project. GeoSyntec argues that the Hart Crowser probabilistic seismic hazard analysis may have underpredicted expected ground motions at the project site.