Sustainable Airport Master Plan
July 17, 2026
Notice of Comment Period Extension — State Environmental Policy Act Sustainable Airport Master Plan Near-Term Projects Draft Environmental Impact Statement
Extended Comment Period End Date: August 20, 2026 (5 pm)
The Port of Seattle has announced an extension of the public comment period for the State Environmental Policy Act (SEPA) Draft Environmental Impact Statement (DEIS) for the Sustainable Airport Master Plan (SAMP) Near-Term Projects (NTPs) at the Seattle-Tacoma International Airport (SEA).
Comments may be submitted electronically to [email protected] or on the project website. Comments must be received by 5 p.m. Pacific Time on August 20, 2026. Written comments may be submitted to: Mr. 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, 2026.July 15, 2026
July 15, 2026
The Cities of Burien, Des Moines, and SeaTac hosted a public meeting and open house on July 14, 2026. The staff from the three cities updated the public on status and city concerns. Below is the link to the materials from the meeting:
Sample/Template Letter to the Port of Seattle to respond to the EIS
July 14, 2026 Meeting Video
July 14, 2026 Power Point Presentation
July 14, 2026 Open House Boards
SAMP Website
SAMP Flyer
Joint Cities Website
June 15, 2026
The Port of Seattle is proposing a major expansion of Seattle-Tacoma International Airport (SEA), and right now, your voice matters.
What's being proposed?
The Port of Seattle owns and operates SEA Airport and wants to add 19 new gates, a second terminal, expanded cargo facilities, and other improvements to handle more flights and passengers in the years ahead. The project is called the Sustainable Airport Master Plan (SAMP).
Why should Des Moines residents care?
More gates and terminals mean more flights — and more noise, traffic, and air quality impacts for communities closest to the airport. Des Moines sits directly in the flight path, so this expansion could significantly affect daily life here.
Where things stand right now
The Port recently released an Environmental Impact Statement (EIS) — a detailed study of how this expansion could affect surrounding communities. The public comment period is open now through July 21, 2026. This is the formal window where your input becomes part of the official record and must be considered before any final decisions are made.
What the City is doing
Des Moines is partnering with the cities of Burien and SeaTac through a formal agreement to submit coordinated comments on behalf of our communities. The City Council received briefings on June 4 and June 11 — videos and materials are available on this webpage.
June 11, 2026 Meeting Video
June 11, 2026 Power Point Presentation
June 4, 2026 Meeting Video
June 4, 2026 Power Point Presentation
How to make your voice heard
There are two types of upcoming meetings — and they serve different purposes:
Learn about the plan (Port of Seattle meetings)
The Port is hosting open houses to present information about the expansion from their perspective. These are a good opportunity to review the details and ask questions directly of Port staff and consultants.
Tuesday, June 23, 6–8 p.m. — Mount Rainier High School cafeteria, 22450 19th Ave S., Des Moines
Virtual meetings — June 30 (noon) and July 9 (6 p.m.) via Zoom
Full schedule at sea-samp.com/get-involved
Translation assistance and childcare are available at all in-person Port meetings.
Learn how to comment effectively (Cities of Des Moines & Burien joint meeting)
This meeting is hosted by your cities — not the Port — and is focused on you. Staff will walk residents through how to write an effective comment letter, what issues to raise, and how to make sure your concerns are formally on the record.
Monday, July 14, 6 p.m. — Burien City Hall
Other ways to comment before the July 21 deadline
Online at sea-samp.com/get-involved
By email or mail to the Port of Seattle — details at the link above
For more information, past meeting videos, and City updates, visit flow.page/samp-equity
May 22, 2026
The Port of Seattle is now conducting an environmental
review under the State Environmental Policy Act (SEPA). The Draft Environmental
Impact Report (EIS) was released May 22, 2026 with a 60 day comment period.
Accessing the Document
The Port’s SEPA draft EIS is available online and
will also be available at public libraries and at the SEA Airport Conference
Center; including Des Moines Library (21620 11th Ave S., Des Moines, WA 98198).
May 21, 2026
Burien, Des Moines, and SeaTac Denied More Time to Review Airport Plan Impacts
Cities' Request for 90-Day Comment Period for Draft Environmental Impact Statement Covering Seattle-
Tacoma International Airport’s Sustainable Airport Master Plan Near-Term Projects Not Granted
Click here for full joint press release
December 9, 2025
Burien, Des Moines, and SeaTac File Joint Petition for Review of FAA Decision
The Cities of Burien, Des Moines, and SeaTac Raise Concerns Over Federal Decision on Seattle-Tacoma International Airport’s Sustainable Airport Master Plan Near-Term Projects
Click here for full joint press release
Response to the Sustainable Airport Master Plan (SAMP)
The City recognizes the impacts on our community due to our proximity to Seattle-Tacoma International Airport (SEA). The City is responding to the Port of Seattle’s plan to expand SEA, which will increase airport impacts on our community.
The Port's planned expansion to handle more passengers and flights is outlined in the Sustainable Airport Master Plan (SAMP). Under this plan, SEA will add gates, build a new terminal and increase flights.
An assessment released in 2024 under the National Environmental Policy Act (NEPA) found that the airport expansion will not have any additional negative impacts on our communities. The City is appealing that finding, working with the cities of Burien and SeaTac. The cities have filed a petition for review of the “finding of no significance” under NEPA.
In early 2026, we anticipate the state will release a draft Environmental Impact Statement, required by the Washington State Environmental Policy Act (SEPA). This document outlines how the airport's proposed expansion would impact the surrounding area and the measures the Port must take to mitigate this. We are partnering with the cities of Burien and SeaTac to ensure our interests are represented.
Community Involvement
The Council has established the Airport Committee, made up of Des Moines residents. This is an advisory body to the City Council, providing input and recommendations on key airport-related topics.
In December 2024, the City held a public meeting in response to the release of the NEPA Environmental Assessment finding of no significance. A recording of that meeting is linked below.
Read on to learn more about the City’s work regarding airport impacts.
Background
The City of Des Moines held a Public Meeting on Tuesday, December 3, 2024 where City consultants gave a power point presentation on how the public can comment to the Port of Seattle on the Sustainable Airport Master Plan Environmental Assessment.
December 3, 2024 Meeting Video
December 3, 2024 Power Point Presentation
Sample/Template Letter to the Port of Seattle/FAA to respond to the EA
SAMP Website: https://www.airportprojects.net/sampntpenvironmentalreview/
Accessing the Document
The FAA’s NEPA draft EA is available online and will also be available at public libraries and at the SEA Airport Conference Center; including Des Moines Library (21620 11th Ave S., Des Moines, WA 98198).
Environmental Review Process
An environmental review is a process to assess how projects at Port of Seattle facilities may impact the environment in a variety of categories that include air quality and climate, water resources, biological resources, and noise, among others. If impacts are identified, the analysis evaluates the extent of those impacts, and if required, identifies ways to reduce or avoid them. A project may require both federal and state environmental reviews, but not always both are required for every project
The purpose of an environmental review is to assess the potential environmental impacts of a proposed project before it is undertaken. Key objectives include:
- Informed decision-making
- Full transparency and public engagement in the decision-making process
- Compliance with laws and regulations
- Identification of ways to avoid, minimize, or mitigate impacts
The SAMP NTP environmental review includes 31 proposed projects, which is being conducted to comply with the National Environmental Policy Act (NEPA) and State Environmental Policy Act (SEPA). The FAA is the lead agency for NEPA, and the Port follows their guidance under FAA Order 1050.1F.
Steps in the NEPA Environmental Review Process
The typical environmental assessment process includes:
- Developing the purpose and need for the project and determining potential alternatives that provide a solution.
- Undertaking scoping to understand agency and public concerns that are then addressed in National Environmental Policy Act (NEPA) documentation.
- Analyzing and documenting the environmental consequences for all alternatives detailed in the NEPA document.
- Conducting public meetings through the analysis process to advise and continue to collect input from agencies, the community and general public, including a public meeting or hearing at the issuance of the draft EA document.
- Addressing comments on the draft NEPA document, which will aid in the preparation of a final NEPA document.
- Ending with either the lead federal agency – in this case, the FAA – issuing a Finding of No Significant Impact/Record of Decision or the lead agency determining that an EIS is required.
Public comment during the environmental review process is provided during formal comment periods. The purpose of public input during this process is to fully understand the potential impacts related to the proposed projects and consider community concerns before a federal agency makes a final decision.