TagThird Runway(201)

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  • Third Runway Retaining Wall

    Construction workers in high-visibility vests and hard hats walk along the base of a massive segmental concrete block retaining wall, several stories tall. The site shows a gravel access road and erosion control markers, consistent with an active earthwork or infrastructure project.

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    A large mobile industrial processing or water treatment unit is shown at an active work site, with visible mud, hoses, ladders, and heavy machinery. A watermark in the lower left reads 'Photo courtesy of Clear Water Compliance.'

  • thirdrunway retaining wall-DSC 0848

  • pat davis pos fill truck third runway 2006 1000

  • Design and Performance of a 46-m-High MSE wall-edge

  • 2022-09-12

    RCAA scoping comments on the “Sea Tac Master Plan Update, including a third runway”

    The Regional Commission on Airport Affairs (RCAA) submitted formal scoping comments on the proposed Sea-Tac Airport Master Plan Update, which includes the addition of a third runway, calling for the Environmental Impact Statement to comply fully with both federal NEPA and state SEPA requirements. The RCAA emphasized that the EIS must be a comprehensive, nonpartisan document that is accessible to ordinary citizens and public officials, complete with proper citations, consistent terminology, indexed appendices, and clearly sourced maps and data. The comments also urged that all environmental impacts be analyzed across multiple time horizons, including the full useful life of the proposed runway, and that all study documents be made freely available to the public throughout King and Pierce Counties.
  • 2022-09-12

    Aircraft adjacent to 179 drop from third runway

    This engineering cross-section diagram from Sea-Tac International Airport illustrates the dramatic 179-foot elevation drop adjacent to the proposed Third Runway, showing how a massive retaining wall and new embankment would be constructed alongside Miller Creek. The exhibit depicts key infrastructure features including a permanent chain-link security fence, rock underdrain, silt fence, inner collection swale, and a minimum 50-foot creek buffer zone designed to protect the existing waterway. The drawing is part of the Miller Creek Instream and Buffer Enhancements project documentation associated with the Third Runway expansion.
  • 2022-09-12

    Filling wetlands: The approval process

    This document explains the regulatory approval process required for filling wetlands as part of Sea-Tac Airport's third runway expansion, which requires both a federal permit under Section 404 of the Clean Water Act and a state certificate under Section 401. The Port of Seattle filed its third application in October 2000 after two previous attempts failed, facing significant environmental obstacles including contaminated fill material, threats to stream flow and salmon habitat, destruction of nearly 20 acres of wetlands, flooding risks, embankment stability concerns in an earthquake-prone area, and existing pollution levels that already exceed allowable limits. The U.S. Army Corps of Engineers must also weigh the public need for the project against these environmental harms, raising broader questions about whether the expansion is justified at all.
  • 2022-09-12

    Review by Ecology

    This document explains the Washington State Department of Ecology's review process for Sea-Tac Airport's applications to fill wetlands as part of its third runway project. Sea-Tac submitted three separate applications between 1996 and 2000, with the third ultimately receiving a Section 401 water-quality certificate that was later put on hold after the Airport Communities Coalition appealed. The Pollution Control Hearings Board identified three key concerns driving the stay: contaminated fill material, insufficient water rights for dry-season stream flow, and inadequate wetlands mitigation plans.