TagSea-Tac Airport(1835)

In August 2025, acoustical engineering firm HMMH measured indoor noise levels at 31 homes near Seattle-Tacoma International Airport to assess eligibility for the airport's Sound Insulation Repair and Replacement Program. Testing found that only one of the 31 homes met the FAA's minimum threshold of 45 decibels interior Day-Night Average Sound Level required to qualify for full sound insulation treatment, while seven additional homes had at least one room exceeding that level. The study used FAA-approved methods, including a Boeing 737-800 aircraft noise spectrum, to calculate how much airport noise penetrates each habitable room with windows closed.

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.

This September 2025 Environmental Assessment evaluates three alternatives for near-term development projects at Seattle-Tacoma International Airport, comparing a No Action scenario against a Proposed Action and a Hybrid Terminal Option through analysis years 2032 and 2037. The study finds that while both action alternatives would increase aircraft operations to approximately 475,655 by 2032 and 509,892 by 2037, resulting in higher emissions and some biological resource impacts, none of the increases are considered significant. Mitigation measures, where warranted, include post-construction stormwater controls and nest protection protocols during construction activities.

This section of the Seattle-Tacoma International Airport (SEA) Environmental Assessment describes the airport's physical setting and surrounding communities as they existed in 2022, serving as the baseline for evaluating potential impacts from near-term expansion projects. SEA occupies approximately 2,800 acres in the City of SeaTac, bordered by state routes and residential neighborhoods in cities including Burien, Des Moines, and Tukwila. The assessment defines a General Study Area of 3,692 acres where direct or indirect impacts from proposed actions may reasonably be expected to occur.

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.