Notes
GeoSyntec Consultants letter dated 6 August 2001, submitted to U.S. Army Corps of Engineers (Regulatory Branch) and Washington State Department of Ecology on behalf of the Airport Communities Coalition (ACC), providing technical review comments on Hart Crowser geotechnical documents for the Seattle-Tacoma International Airport Third Runway embankment fill and West Mechanically Stabilized Earth (MSE) Wall. Reviewed documents include Hart Crowser’s December 4, 2000 geotechnical engineering analyses, January 25, 2001 seismic design memorandum, and March 5, 2001 liquefaction analysis memorandum. GeoSyntec (Patrick C. Lucia, Ph.D., P.E. and Edward Kavazanjian, Jr., Ph.D., P.E.) identifies critical deficiencies: underestimated seismic risk from multiple Seattle-region earthquake sources, incorrect seismic stability and FLAC deformation analyses, improper representation of liquefiable material extent, overestimated composite shear strengths using one-third/two-thirds liquefaction assumption, progressive yielding mechanism ignored at embankment toe, and insufficient documentation for regulatory decision. Exhibit AR021838, PCHB Third Runway proceeding.