June 19, 2001August 2, 2026

Exhibit 76: Analysis of Preferential Ground Water Flow Paths Relative to Proposed Third Runway, STIA

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Draft technical memorandum prepared by Associated Earth Sciences, Inc. (AESI, Project No. BV99122C) for Port Of Seattle, dated June 19, 2001, analyzing preferential ground water flow paths relative to the proposed Third Runway at Seattle-Tacoma International Airport (STIA). Evaluates potential contaminant migration from the Aviation Operations and Maintenance Area (AOMA) to the third runway construction area via subsurface utility trenches, perched ground water zones, and natural westward flow in the Qva aquifer. Prepared in response to Washington Department of Ecology (Ecology) request under Model Toxics Control Act (MTCA) Agreed Order. Concludes no reasonable threat of contaminated ground water migration to Third Runway area. Discusses glacial till perching layers, Qva aquifer hydrogeology, South King County Groundwater Management Plan, and STIA subsurface conditions.

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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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