Notes

Draft memorandum dated January 17, 2002 from Hart Crowser engineers Doug Lindquist, Reda Mikhail, and Michael Bailey to Jim Thomson (HNTB Corporation), project number 4978-40, regarding FLAC (finite difference model) seismic analysis of three proposed mechanically stabilized earth (MSE) retaining walls for the Third Runway project at Seattle-Tacoma International Airport. Analyses cover four wall sections under seismic liquefaction conditions; predicted deformations generally less than 1 foot for wall sections, up to 2-3 feet for liquefied soils beyond runway embankment limits. Reinforcing stress did not exceed yield strength; some cases exceeded AASHTO limiting value of 0.55 times yield. Results provided to HNTB Corporation and RECo (John Sankey). Corrosion reduction of 1.008 mm per side applied per AASHTO for 100-year design life. Concludes proposed MSE design satisfies seismic performance objectives presented to Corps of Engineers (Hart Crowser 2001b).

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As the source for federal transportation grants, the Puget Sound Regional Council was charged with developing a system to meet the growing need for commercial aviation. When the search for a second airport failed, they authorized the Port of Seattle to build the Third Runway, with a mandate to develop a noise abatement and mitigation program. In their effort to stop the Third Runway, the ACC argued over every detail of the Port's efforts--including property buyouts and sound insulation. The dispute was meant to be settled by a three member Expert Arbitration Panel. This is their final report. It finds 2-1, that the Port's program was insufficient in several respects. Despite that, funding for the Third Runway was approved by the PSRC, and the 'Port Package' program, proceeded largely unchanged. Expert Arbitration Panel's final decision finding that the Port of Seattle had not shown sufficient reduction in real on-the-ground noise impacts to satisfy noise reduction conditions required for approval of a third runway at Sea-Tac International Airport. The majority decision concluded the Port's noise abatement programs were insufficient despite being impressive in scope.

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