July 16, 2001August 2, 2026

Exhibit 51: 401 Permit Decision-Making, Sea-Tac Airport Third Runway — Final Meeting Notes, Low Flow Analysis

Notes

Final meeting notes from July 16, 2001 for the 401 Permit Decision-Making process for Sea-Tac International Airport Third Runway, covering low flow analysis for Miller Creek and Walker Creek. Attendees included Ann Kenny (Dept. of Ecology), Kelly Whiting (King County), Keith Smith (Port of Seattle), Paul Fendt and Robert Farid (Parametrix), Rick Schaefer (EarthTech), and Joe Brascher (Aquaterra). Topics include proposed mitigation period August 1–October 31, mitigation flow rates of 0.10 cfs (Miller Creek) and 0.065 cfs (Walker Creek) using 1991 as the 2-year return frequency surrogate target year, reserve storage vault sizing (14 ac-ft, 5 vaults in Miller Basin, 92-day release at 0.10 cfs), non-hydrologic effects including septic tank removal under Section 401, biological impact questions raised by King County, and next steps including Port submittal by 7/23. Document marked AR 017658–017660.

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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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