TagEnvironmental Impact Statement(325)

In September 2025, the Council on Environmental Quality (CEQ) issued updated non-binding guidance to federal agencies on how to conduct environmental reviews under the National Environmental Policy Act (NEPA), replacing earlier guidance from February 2025. The update streamlines the permitting process by incorporating a recent Supreme Court ruling limiting the scope of required environmental analysis, removing climate change and environmental justice considerations, and introducing an optional fee-based program that cuts review timelines in half. Agencies are encouraged to revise their own NEPA procedures using a provided template while continuing existing review processes without delay.

This traffic engineering report analyzes three signalized intersections along S 128th Street near SR 509 in the Sea-Tac area under projected 2032 No Action conditions during the PM peak hour. The study finds that the SR 509 ramp intersections are operating well over capacity, with an Intersection Capacity Utilization of 104.6% and an ICU Level of Service G, while the Des Moines Way S intersection operates more acceptably at 63.3% ICU. Overall intersection control delays range from approximately 19 to 27 seconds, with most approaches functioning at Level of Service B or C.

Appendix O of the Sustainable Airport Master Plan (SAMP) Environmental Assessment documents how the FAA engaged the public and agencies during the NEPA review process for Sea-Tac Airport, including public meetings, briefings, and outreach to communities, elected officials, and underrepresented groups. The summary notes that several Executive Orders and CEQ regulations referenced during the Draft EA have since been revoked, and that the FAA's final decision will rely on updated federal guidance including FAA Order 1050.1F and Executive Order 14154. Public comments received and submitted studies are also included as part of this appendix.

The City of Des Moines, Washington, formally requests that the Port of Seattle reject the Determination of Non-Significance (DNS) for the Sea-Tac Airport Flight Corridor Management Program, arguing that it fails to adequately assess impacts on the city's tree canopy and urban forest. City Manager Katherine Caffrey urges the Port to instead conduct a full Environmental Impact Statement (EIS) examining tree removal, urban heat, air quality, stormwater, and habitat effects. The letter emphasizes that Des Moines residents already face disproportionate noise and health burdens from airport traffic, making tree canopy preservation especially critical to their wellbeing.

This section of the Seattle-Tacoma International Airport Environmental Assessment describes how planners evaluated different alternatives to the airport's near-term expansion projects, using a two-step screening process to determine whether each option met the project's stated goals and was practical to implement. Public suggestions submitted during the scoping process—such as building a new airport, using high-speed rail, limiting growth, or relying on other existing airports—were largely rejected because they could not meet current and future passenger demand at SEA. A No Action Alternative is also included, representing a future scenario in which none of the proposed new construction takes place.

The Port of Seattle is conducting an Environmental Assessment (EA) under federal law for 31 near-term improvement projects at Seattle-Tacoma International Airport (SEA), covering airfield upgrades, taxiway extensions, and passenger facility improvements. The projects, collectively known as the Sustainable Airport Master Plan Near-Term Projects, are intended to reduce congestion, improve safety, and enhance the passenger experience, with construction potentially beginning in late 2025 and completion targeted for 2032. The federal review will determine whether the projects could significantly impact the surrounding human environment, including potential noise and other effects on neighboring communities.

This section of the Seattle-Tacoma International Airport Environmental Assessment lists the individuals and organizations responsible for preparing the EA for the Sustainable Airport Master Plan Near-Term Projects, finalized in September 2025. It includes contributors from the FAA, Port of Seattle, and multiple consulting firms covering areas such as noise analysis, air quality, surface transportation, wetlands, cultural resources, and public engagement. Key organizations involved include Landrum & Brown, Concord Engineering, Confluence Environmental Company, Parametrix, Stell Environmental, and others.

This document is the References section of the Environmental Assessment for Seattle-Tacoma International Airport's Sustainable Airport Master Plan Near-Term Projects, finalized in September 2025. It lists all sources cited across the assessment's chapters, including federal regulations, FAA advisory circulars, technical memoranda, city comprehensive plans, and environmental studies used to evaluate the airport's proposed development projects. The referenced materials cover topics such as air quality, facility requirements, stormwater management, land use, and aviation activity forecasting.

The Final Environmental Assessment for Seattle-Tacoma International Airport's Sustainable Airport Master Plan near-term projects explains that cumulative impact analysis has been removed from the document. This change reflects recent legal developments, including the revocation of CEQ regulations implementing NEPA and a May 2025 Supreme Court ruling, which together mean federal agencies are no longer required to assess the combined environmental effects of separate but related projects. As a result, the section that previously contained cumulative impacts data and analysis is now absent from this final report.

The U.S. Supreme Court ruled in May 2025 that federal agencies have broad discretion in determining the scope of environmental reviews required under the National Environmental Policy Act (NEPA). The case involved a proposed 88-mile railroad in Utah, where the Court held that agencies do not need to analyze the environmental effects of separate upstream or downstream projects — such as oil drilling or refining — when reviewing a specific infrastructure project. Courts must give substantial deference to agency decisions about what to include in environmental impact statements, rather than imposing their own judgment about what details are required.