TagNEPA(463)

The Port of Seattle's Sustainable Airport Master Plan (SAMP) outlines 31 near-term construction projects at Seattle-Tacoma International Airport, including a second terminal with 19 gates, new cargo facilities, and roadway changes, all aimed at serving up to 56 million passengers annually by 2050. A federal environmental review (NEPA) is underway to assess potential impacts, with a 45-day public comment period opening October 21, 2024, allowing community members to submit feedback online, by mail, or at public libraries in Burien, Des Moines, and SeaTac. A separate state-level environmental review (SEPA) will follow once the federal process is complete.

Seattle-Tacoma International Airport's Sustainable Airport Master Plan (SAMP), completed in 2018, outlines 31 near-term development projects and is currently undergoing a federal environmental review (NEPA) process, with a draft Environmental Assessment published in October 2024. The review evaluates potential impacts on air quality, water resources, noise, and other environmental factors before any projects move forward. Once the federal NEPA process concludes, a Washington State-level environmental review (SEPA) will follow.

The Port of Seattle announced the release of a draft Environmental Assessment (EA) for Seattle-Tacoma International Airport's Sustainable Airport Master Plan (SAMP) on October 21, 2024, covering 31 near-term development projects including a second terminal, elevated busway, and new cargo facilities. The plan addresses projected regional population growth of one million people by 2035. Members of the public were invited to submit comments on potential environmental impacts during an open comment period running from October 21 to December 5, 2024.

This technical report analyzes existing surface transportation and traffic conditions around Seattle-Tacoma International Airport as part of the Sustainable Airport Master Plan (SAMP) Near-Term Projects Environmental Review. It examines 108 intersections — including signalized, stop-controlled, and uncontrolled locations — along key travel routes connecting the airport to surrounding communities, focusing on weekday PM peak-hour traffic volumes. The study also includes freeway analysis of SR 518 and I-5 ramps and segments at the request of WSDOT.

This report analyzes existing traffic conditions around Seattle-Tacoma International Airport as part of the Sustainable Airport Master Plan (SAMP) Near-Term Projects Environmental Review. It examines 108 intersections—including 63 signalized, 41 stop-controlled, and 4 uncontrolled—along key routes connecting the airport to surrounding communities, focusing on the weekday PM peak hour (4–6 p.m.). Freeway segments of SR 518 and I-5 were also evaluated at WSDOT's request to provide a comprehensive picture of surface transportation conditions in the airport study area.

The FAA issued a Negative Determination in July 2024, concluding that planned Near-Term Projects at Seattle-Tacoma International Airport (SEA) are not likely to cause coastal effects under the Coastal Zone Management Act. The projects include taxiway extensions, blast pad expansions, and relocation of navigational equipment across four airfield areas, with construction set to begin in 2026 over a six-year period. Because all FAA actions are confined to upland areas within the airport property, no significant impacts to Washington State's coastal zone resources were identified.