TagEnvironmental Impact Statement(325)

This technical appendix, prepared by Jeffery Bogen of DAAC in May 2026, analyzes runway and airspace capacity at Seattle-Tacoma International Airport (SEA) to support the Port of Seattle's Sustainable Airport Master Plan (SAMP) environmental review process. It compares FAA 2016 baseline hourly flow rates against observed 2024–2026 performance data, documents current capacity improvements, and projects annual flight operations through 2037 under both constrained and unconstrained growth scenarios. The document is intended as supporting reference material for public comments on seating capacity impacts under SEPA/EIS review.

Des Moines resident Jeffrey Bogen submitted a formal comment arguing that the Sea-Tac Airport Master Plan (SAMP) Environmental Impact Statement fails to adequately analyze cumulative health effects on nearby communities. He contends that the EIS must go beyond examining individual pollution sources and instead assess the combined burden of aircraft ultrafine particles, roadway traffic emissions, chronic noise, and other stressors together, since scientific research shows these exposures interact and compound one another. Bogen calls for a comprehensive cumulative-risk framework, backed by ten peer-reviewed studies, to be incorporated into the EIS before any accurate public health or policy conclusions can be drawn.

A Des Moines resident's formal comment on the Seattle-Area Metroplex Environmental Impact Statement argues that Sea-Tac Airport's official planning assumption — that average aircraft size will grow by only 0.5% per year — is mathematically incompatible with the airport's own goal of 56 million annual passengers by 2032. The comment shows that reaching that passenger target under the current assumption would require roughly 880,000 flights per year, far exceeding the airport's infrastructure ceiling of about 517,000 operations. The author contends that airlines like Alaska and Delta are already ordering larger aircraft and expanding international routes at Sea-Tac, meaning faster fleet upgauging is not a worst-case scenario but a necessity for the plan to make sense.

A Des Moines resident's formal comment on the Sea-Tac Airport Master Plan (SAMP) Environmental Impact Statement argues that the SAMP's aircraft seat capacity assumptions are now outdated, pointing to major 2026 fleet expansions by Alaska Airlines and Delta that include significantly more and larger widebody aircraft operating from SEA. The comment contends that because larger planes carry more passengers per flight, fewer total aircraft operations would be needed to reach the SAMP's 56 million passenger target, meaning the airport could handle projected growth with less noise impact than the SAMP currently estimates. The author presents revised seat-capacity scenarios suggesting the SAMP's low-growth assumption is internally inconsistent and that updated fleet data should be incorporated into the EIS before final conclusions are drawn.

A Des Moines resident submitted a formal comment arguing that the Seattle-Area Metroplex Environmental Impact Statement (SAMP EIS) significantly underestimates the health risks of aviation noise by omitting key peer-reviewed studies linking aircraft noise to cardiovascular disease, heart structural changes, and sleep disruption. The commenter contends that the EIS relies on outdated and methodologically flawed research, particularly FICAN studies using extrapolated rather than measured data, while ignoring more recent findings from the WHO, the HYENA Project, and a 2025 cardiac MRI study. The comment calls on the FAA to conduct a proper cumulative health effects analysis and require additional noise mitigation measures beyond the current DNL 65 dB contour threshold.

A Des Moines resident's formal comment argues that the Seattle-Area Metroplex Environmental Impact Statement's noise analysis is legally inadequate because it relies solely on a federal FAA noise threshold rather than Washington State's own multi-factor significance standard. The comment contends that the standard noise metric used (DNL) masks the real impact of roughly 96 additional daily flights projected by 2037, since it averages out individual disturbance events rather than counting them. The commenter calls for supplemental analysis using alternative metrics—such as single-event sound levels and nighttime averages—supported by peer-reviewed health studies linking aircraft noise to sleep disruption and cardiovascular harm.

Presentation about the Port of Seattle’s Sustainable Airport Master Plan Near-Term Projects, covering the completed NEPA process and the required SEPA Draft Environmental Impact Statement. The document outlines various airport infrastructure projects including runway improvements, terminal facilities, maintenance facilities, and cargo operations planned for Sea-Tac Airport.

The Port of Seattle released a Draft Environmental Impact Statement (DEIS) under the State Environmental Policy Act (SEPA) for near-term construction and expansion projects at Seattle-Tacoma International Airport, finding that surface transportation would face significant impacts while noise and air quality impacts would remain within legal health standards. A 60-day public comment period runs from May 22 to July 21, 2026, with in-person meetings in SeaTac, Burien, Des Moines, and Federal Way, plus virtual options and multilingual outreach. A Final Environmental Impact Statement is expected by the end of 2026.