• 2022-09-12

    Fact sheet for NPDES permit WA-002465-1, Sea-Tac International Airport

    This document is an NPDES (National Pollutant Discharge Elimination System) permit fact sheet for Sea-Tac International Airport, issued by the Washington State Department of Ecology. It details the locations of numerous water discharge outfalls across the airport property, covering industrial wastewater, stormwater from industrial activities, and stormwater from construction activities. The discharges flow into several local waterways including Des Moines Creek, Miller Creek, Walker Creek, Gilliam Creek, and Puget Sound.
  • 2022-09-12

    Brief analysis of Pollution Control Hearings Board’s ruling on the Sea–Tac Airport’s Section 402 water pollution permit

    The Pollution Control Hearings Board ruled largely in favor of community groups ACC and CASE in their challenge to Sea-Tac Airport's water pollution permit, ordering stricter wastewater treatment standards and rejecting most of the Port's appeals. Key victories included requiring the airport to meet long-overdue water quality standards for its industrial wastewater discharged into Puget Sound, mandating improved toxicity testing during de-icing season, and directing a professional wetlands analysis of Lake Reba. Of the seven final directives issued by the Board, six favored the community appellants and only one favored the Port.
  • 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.
  • 2022-09-12

    Review by the U.S. Army Corps of Engineers

    The U.S. Army Corps of Engineers has been reviewing a permit application related to a proposed third runway at Sea-Tac Airport, described as the largest Section 404 proceeding the Corps had handled and the biggest public works project in Washington State since the Grand Coulee Dam. Key issues under consideration include the replacement of lost wetlands, streamflow impacts, and the seismic stability of the proposed runway embankment. No deadline exists for the Corps to render its final decision, though draft permit conditions were reportedly being prepared by civilian technicians in the Seattle District Office.
  • 2022-09-12

    Functional assessment, impact and mitigation plan review to the record of decision for Seattle, Port of (1996-4-02325)

    This U.S. Army Corps of Engineers document reviews the environmental impact of construction projects at Seattle-Tacoma International Airport, including the Third Runway and related Master Plan Update improvements, focusing on impacts to wetlands and waterways. The Corps conducted an independent assessment of wetland functions and evaluated whether the Port of Seattle's proposed mitigation plans adequately compensated for the destruction or alteration of aquatic resources. After finding the Port's initial December 2000 mitigation plan insufficient, the Corps worked with the Port to develop a revised plan, accepted in November 2001, that better addressed the loss of wetland functions caused by airport construction.
  • 2022-09-12

    Opening brief of petitioner Citizens Against Sea-Tac Expansion

    This legal brief was filed by Citizens Against Sea-Tac Expansion before the Washington Supreme Court, challenging a decision by the Pollution Control Hearings Board regarding the expansion of Seattle-Tacoma International Airport. The group argues that state regulators improperly allowed the Port of Seattle to rely on future, unwritten stormwater permits as proof that airport runoff would meet water quality standards, and that regulators wrongly pre-authorized pollution mixing zones in nearby waterways without sufficient oversight. The case centers on whether proper environmental protections were in place before approving the airport expansion project.
  • 2022-09-12

    Wetland classes found in the project area

    This document classifies and describes the various wetland types found within the Sea-Tac Airport project area, using both the Cowardin (1979) and Hydrogeomorphic (HGM) classification systems. It identifies forested, scrub-shrub, emergent, aquatic bed, and riverine wetlands across three drainage basins — Miller Creek, Des Moines Creek, and Walker Creek — listing the specific wetland units belonging to each category. The classifications support environmental impact assessment and mitigation planning associated with airport development activities.
  • 2022-09-12

    Tabulation of the number of comments received on an issue throughout the permit review process

    This document tabulates public comments received during a permit review process, likely related to a construction or development project near Sea-Tac Airport. A total of 509 individuals opposed the permit, while 101 supported it, with additional concerns raised across topics including MSE wall integrity, wetlands, hydrology, air and noise pollution, and airport/aircraft safety. The index identifies specific commenters — ranging from environmental consultants to aviation industry groups — and maps each comment to a designated paragraph number for formal review response.
  • 2022-09-12

    Corps wetland and aquatic resource impact analysis

    This document analyzes the environmental impacts of construction projects at a north airfield area on wetlands and waterways in the Miller Creek Basin. It details how filling approximately 2.75 acres of wetlands and 980 linear feet of Miller Creek will affect water quality, hydrology, fish habitat, wildlife, and plant communities. It also describes a compensatory mitigation plan at the nearby Vacca Farm site, where Miller Creek will be relocated and wetlands restored to offset the project's ecological losses.