Notes
Chapter 4 of the Seattle-Tacoma International Airport (Sea-Tac Airport) Sustainable Airport Master Plan (SAMP) Near-Term Projects Draft SEPA Environmental Impact Statement (EIS), dated May 2026. Covers potential adverse environmental impacts and mitigation measures for Alternative 1 (No Action), Alternative 2 (Proposed Action), and Alternative 3 (Hybrid Terminal Option) under WAC 197-11-444. Analysis years are 2032 (operational baseline) and 2037 (out-year), with construction impacts assessed 2025–2032. Includes forecasted aircraft operations (466,900–509,892) and passengers (57–64 million) by alternative per Table 4.2-1. Section 4.3.1 details air quality impacts for criteria pollutants CO, NO2, PM10, PM2.5, SO2, NOx, VOCs using AEDT version 3f/3g and MOVES version 4/5; human health risk assessment (HHRA) thresholds include hazard index >1 (non-cancer) and cumulative cancer risk >1E-05. NAAQS significance thresholds adopted by Washington State and PSCAA apply. Construction emissions estimated via ACEIT and USEPA MOVES4. FAA Order 1050.1F/1050.1G and NEPA EA findings incorporated by reference.