Notes
Draft memorandum J-4978-28 from Hart Crowser (Douglas Lindquist, Barry Chen PhD P.E., Michael Bailey P.E.) to Jim Thomson P.E. at HNTB, dated September 7, 2000, presenting methods and results of liquefaction analyses for the proposed Third Runway embankment and retaining walls at Sea-Tac, Washington. Analyzed 120 borings with Standard Penetration Test (SPT) results from 112 Hart Crowser borings and 8 Civil Tech borings. Evaluates cyclic stress ratio (CSR), cyclic resistance ratio (CRR), factor of safety against liquefaction, and post-liquefaction residual shear strength for the NSA Wall, West Wall, South Wall, and 2H:1V slope area using NCEER 1996 methodology. Five seismic events analyzed ranging from 72-year return interval (0.16g, M6.5) to 975-year return interval (0.47g, M8.0) in the Puget Sound area. Liquefaction-susceptible soils (loose to medium dense sands and sandy silts) found intermittently under all three proposed MSE walls.