Notes

GeoSyntec Consultants submitted a correction letter to the U.S. Army Corps of Engineers and Washington State Department of Ecology on behalf of the Airport Communities Coalition, clarifying an error in their earlier February 16, 2001 technical review letter regarding the Third Runway project at Seattle Tacoma International Airport. The correction changes the word ‘underestimate’ to ‘overestimate’ in Comment #7, clarifying that the Hart Crowser methodology may seriously overestimate the seismic resistance of the wall by calculating yield acceleration only for the failure surface with the lowest static factor of safety rather than systematically searching for the failure surface with the lowest yield acceleration. The corrected comment explains that a proper pseudo-static slope stability analysis should independently search for critical failure surfaces, including sliding block failure surfaces along weak seams such as peat layers.

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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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