Des Moines residents get more time to comment on Sea-Tac expansion plan

Des Moines residents have more time to comment on a proposed package of near-term projects at Seattle-Tacoma International Airport after the Port of Seattle extended the State Environmental Policy Act draft environmental impact statement deadline to 5 p.m. Pacific time on August 20, 2026.

The Port announced the 30-day extension July 17, moving the deadline from July 21 after requests for more time to review the document. The review covers 31 proposed Sustainable Airport Master Plan near-term projects, or SAMP NTPs. The projects remain in environmental review; the extension does not approve them or authorize construction.

What the airport review covers

According to the Port of Seattle, the proposed project package includes a second terminal with 19 additional gates, cargo facilities, a ground transportation center, airfield taxiway extensions and expansion of the airport fuel facility. The plan also includes an automated people mover connecting the rental-car facility, the proposed new terminal and the existing main terminal.

The Port says the near-term projects are intended to improve airport safety, efficiency and access and to meet projected demand. Its project page says the proposed projects are designed to be complete or under construction by 2032. That is a planning target, not a final construction authorization; the Port says commission authorization is required before work begins on individual projects.

Why Des Moines is involved

Des Moines is coordinating its review with Burien and SeaTac because of the cities’ proximity to SEA and their shared interest in how airport-related activity could affect nearby communities. The three cities hosted a public meeting and open house July 14 at Burien City Hall.

Local reporting from the meeting described concerns involving potential effects on noise, traffic, air quality, water resources, fuel and cargo facilities, roadways, utilities and other supporting infrastructure. Representatives from Des Moines, Burien and SeaTac presented their shared review of the airport plan.

Those subjects are part of the environmental-review record, not settled findings about what will happen in Des Moines. A DEIS evaluates potential impacts, alternatives and possible mitigation measures. It does not by itself establish that projected noise, traffic, air-quality or water effects will occur as described, nor does it represent final approval of the proposed projects.

How residents can comment

Comments must be received by 5 p.m. Pacific time on August 20, 2026. Residents, airport workers, commuters and nearby businesses can submit comments electronically through the SAMP project website or by email using the Port’s posted instructions. Written comments may be mailed to Steve Rybolt, Port of Seattle, Aviation Environment and Sustainability, P.O. Box 68727, Seattle, WA 98168. Mailed comments must be postmarked by 5 p.m. on August 20.

The City of Des Moines has posted the extension notice, July 14 meeting materials and links to the Port’s comment process. Comments submitted during the formal period become part of the environmental-review record and may inform the Port’s response and later decisions. No final determination on the projects’ impacts or mitigation has been made through the current comment period.

Sources

• City of Des Moines Sustainable Airport Master Plan notice
• Port of Seattle Sustainable Airport Master Plan page
• Waterland Blog July 14 open-house report