The cities of SeaTac, Burien and Des Moines are asking the Port of Seattle to postpone its final environmental impact statement for proposed airport projects until a federal appeals court rules on their challenge to the underlying federal review.

In a joint letter delivered Monday, Oct. 26, the cities warned that moving ahead before the court’s decision could lead to costly revisions, another public comment period and greater exposure to legal challenges.

“The SEPA process does not stand apart from the NEPA process. It rests upon it,” the cities wrote, referring to the state and federal environmental reviews.

The request concerns projects proposed under Sea-Tac Airport’s Sustainable Airport Master Plan (SAMP). The cities’ pending case before the 9th U.S. Circuit Court of Appeals challenges the Federal Aviation Administration’s environmental assessment of those projects.

At issue is how much the Port’s state review relies on that federal assessment.

According to the cities, the Port’s draft environmental impact statement incorporates federal analyses for more than a dozen categories, including noise, water resources, traffic, biological resources, and historic and cultural resources. It also uses the federal assessment’s forecasts, emissions inventories, modeling assumptions and thresholds for determining whether impacts are significant.

If the court sets aside the federal assessment or sends it back for further review, the cities argue, portions of the Port’s final statement that depend on it could also need reconsideration.

For residents following airport noise, traffic and environmental concerns, the cities also raised a question about public participation. Issuing the final statement would close the main opportunity for public input under state law, they said, while subsequent revisions would likely require a new comment period.

The cities further warned that a state decision relying on a federal analysis later found inadequate would be more vulnerable to a legal challenge.

Their letter points to the review sequence chosen by the FAA and the Port. According to the cities, the federal assessment says the agencies elected to conduct the federal and state reviews separately and sequentially, with the state process following the federal review. The Port has described its draft statement as building on the completed federal assessment.

Given that approach, the cities contend, the Port should wait for the court to determine whether the federal analysis is legally sound.

The request follows months of coordinated scrutiny of airport planning. As we previously reported, Burien and Des Moines airport advisory committees met jointly to discuss the environmental review and concerns about noise, traffic and other impacts on surrounding communities.

The three cities announced their joint court challenge in December 2025.

In their latest statement, the cities said they remain willing to work with the Port and discuss the postponement request with its environmental review staff and legal counsel.

“A principled pause would preserve the integrity of the SEPA process and protect public, agency and potentially judicial resources,” the cities wrote.

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