Notes
Draft memorandum dated April 10, 2000 from Douglas Lindquist, Barry Chen P.E., and Mike Bailey P.E. of Hart Crowser, Inc. to Jim Thomson P.E. at HNTB regarding seismic basis of design for the Third Runway Project (J-4978-14) at Sea-Tac Airport for the Port of Seattle. Compares 475-year return period (0.36g peak acceleration, 10% probability of exceedence in 50 years) versus 975-year return period (0.47g, 5% probability of exceedence in 50 years) seismic events. Covers liquefaction analyses, slope stability analyses using limit equilibrium methods with pseudo-static factor of safety of 1.1, and seismic deformation analyses using FLAC two-dimensional finite difference model. Analyses cover NSA Wall, West MSE Wall (Mechanically Stabilized Earth), and South MSE Wall. Key findings: reinforcement strength for 975-year event approximately twice that needed for 475-year event; maximum displacements at top of model wall 4–5 feet (475-year) versus 7–8 feet (975-year); 975-year event produced yielding of approximately 30% more reinforcing elements. References probabilistic seismic hazard analysis memorandum dated October 8, 1999. AR 044372.