Seattle-Tacoma International Airport Environmental Assessment for the Sustainable Airport Master Plan Near-Term Projects: Chapter 2 — Alternatives

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.

Notes

Chapter 2 of the Final Environmental Assessment (EA) for the Sea-Tac Airport (KSEA) Sustainable Airport Master Plan (SAMP) Near-Term Projects, dated September 2025. Covers the NEPA-required alternatives evaluation process including two-step screening (Level 1: Purpose and Need; Level 2: operational impacts and cost), the No Action Alternative, and Table 2-1 evaluating scoping-suggested alternatives such as phased construction of passenger gates (56 MAP, 110 operations per hour), terminal processing facility expansion, roadway/curbside changes, full taxiway separation (500-foot Runway 16L/34R and Taxiway B), limited/reduced growth, use of other existing airports, building a new regional airport, alternative transportation modes (high-speed rail, hyperloop), elimination of North Employee Surface Parking Lot L06 (replaced by employee parking garage L07), public/private transit incentives, and secure-side terminal connection to Concourse D. Conducted under FAA Order 1050.1F and FAA Order 5050.4B. Analysis completed by Landrum & Brown, 2020.

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