In February 2001, engineering firm GeoSyntec Consultants submitted a technical review letter on behalf of the Airport Communities Coalition, raising serious concerns about the proposed Third Runway expansion at Seattle-Tacoma International Airport. The review identified significant deficiencies in the geotechnical investigation and analysis supporting construction of the embankment fill and West MSE Wall, including insufficient soil strength data and inadequate seismic safety assessments. GeoSyntec warned that the proposed design — which would result in the world's tallest MSE wall built over weak, potentially unstable soils in a seismically active region — could fail under earthquake conditions, threatening both airport operations and nearby natural resources.Open full document
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GeoSyntec Consultants, retained by the Airport Communities Coalition, submitted technical comments to the U.S. Army Corps of Engineers and Washington State Department of Ecology regarding the proposed Third Runway Expansion Project at Seattle-Tacoma International Airport. The letter identifies significant deficiencies in field and laboratory investigation and analysis related to the embankment fill and West Mechanically Stabilized Earth (MSE) Wall, as well as the Industrial Wastewater System Lagoon #3 expansion. GeoSyntec concludes that the project as conceived lacks sufficient basis to demonstrate it can withstand static and seismic loads, particularly given the unprecedented scale of the West MSE Wall and the seismically sensitive location.