September 12, 2000August 2, 2026

EXH AR045977: Evaluation of Perched Zone Interception and Possible Impacts to Wetland Hydrology, Borrow Area 3, Sea-Tac Third Runway

Notes

Hart Crowser report prepared for Port of Seattle, dated September 12, 2000 (J-4978-13), evaluating perched groundwater zone interception at Borrow Area 3 for the Sea-Tac Third Runway project. Analyzes shallow perched groundwater flow from northwest to southeast beneath Borrow Areas 3 and 4, its role in sustaining Wetland 29, and the impact of borrow area excavation on wetland hydrology. Responds to Pacific Groundwater Group (PGG, 2000) Hydrology Studies Report commissioned by Washington State Department of Ecology. Includes ModFlow groundwater modeling, water level data, flow nets, seepage face analysis, and swale mitigation design. References Parametrix 1999 wetland mapping.

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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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