Notes

Northwest Hydraulic Consultants, retained by the Airport Communities Coalition (ACC), writes to the U.S. Army Corps of Engineers identifying serious deficiencies in the Port of Seattle’s low flow mitigation analysis for Miller, Walker, and Des Moines Creeks related to the Sea-Tac third runway project. The letter critiques the Port’s assumption that virtually all runway runoff infiltrates into filter strips, arguing this causes embankment recharge volumes to be overstated and stream low flow impacts to be understated. Additional concerns are raised about the use of hourly time steps in HSPF modeling and the Port’s failure to address outstanding public comments and certification requirements.

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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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