July 16, 2001August 2, 2026

EXH AR029205: 401 Permit Decision-Making Sea-Tac International Airport Third Runway — Final Meeting Notes, Low Flow Analysis

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Final meeting notes prepared by Kate Snider of Floyd & Snider Inc. for the 401 Permit Decision-Making process for the Sea-Tac International Airport Third Runway project, dated July 16, 2001. Attendees included representatives from Washington State Department of Ecology (Ann Kenny), King County (Kelly Whiting), Port of Seattle (Keith Smith), Parametrix, EarthTech, and Aquaterra. Document covers low flow analysis for Miller Creek and Walker Creek, including proposed mitigation periods of August 1–October 31, mitigation flow rates (0.10 cfs for Miller Creek, 0.065 cfs for Walker Creek), reserve storage vault sizing (14 ac-ft, 5 vaults, 92-day release), non-hydrologic effects including septic tank removal, biological impact questions raised by King County, and next steps for the low flow evaluation report and mitigation operations plan. ECY00015001 through ECY00015003.

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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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