Federal Way Challenges Airport Noise Analysis, Calls for Better Metrics

The City of Federal Way is asking the Port of Seattle for more information about how airport expansion could affect aircraft noise over the city, including neighborhoods and schools.

In a July 14 letter commenting on the Seattle-Tacoma International Airport Draft Environmental Impact Statement (DEIS), the city thanked the Port for extending the public comment deadline and noted changes to the glide path for airplanes approaching SEA Airport’s east runway, 34 Right.

Federal Way welcomed the flight-path changes but asked the Port to quantify what they will actually mean for residents on the ground:

“We ask for a response in the SAMP summary if this will reduce noise and for quantification of the increase in height of the flight path for three areas under the flight path: the northern border of Federal Way, the southern border of Federal Way, and above the neighborhoods surrounding Steel Lake Park.”

Much of the remainder of this article comes directly from the city’s statement. I’ve added bold emphasis to highlight several key points.

Federal Way questions how expansion impacts are measured

The city’s strongest concerns center on whether the DEIS adequately evaluates the effects of the airport’s proposed expansion, including 19 additional gates.

Federal Way wrote:

“Third, and most crucially, we are concerned about impacts of the proposed expansion of the airport by 19 additional gates. SEA is projecting passenger traffic from 46.9 million in 2O17 to 56 million in 2027, and further increasing to 66 million by 2034. This will result in greater noise and health impacts on Federal Way residents. The DEIS states that the FAA regulates aircraft noise; in fact, the 1990 federal ANCA statute  [Airport Noise and Capacity Act] strictly limits locally-imposed aircraft noise restrictions. The FAA’s authority does not preempt the mitigation required by SEPA of additional aircraft noise impacts resulting from a proposed airport expansion project.”

City challenges the 65-decibel noise metric

The city specifically objected to the noise metric used in the DEIS:

“The DEIS inappropriately concludes that the SAMP would generate no significant additional noise impacts on Federal Way residents, schools, churches and other sensitive areas, because it used the FAA’s arbitrary, outdated and fundamentally flawed “65-decibel day/night averaging” noise metric. The 65 DNL metric has not been adopted by our state for use in SEPA impact analyses. Human beings experience noise annoyance and health impacts as single loud events, or SEL’s, not averaged with occasional daytime and middle-of-the-night silence.”

Federal Way asks for single-event noise analysis

Federal Way pointed to previous experiences with aircraft noise over the city and asked for a different way of measuring the effects:

“We appreciate that current Port Commissioners personally have experienced the very high decibel levels from frequent and low-flying aircraft over Nautilus Elementary School and its surrounding Federal Way neighborhoods. Thus, as Mayor Ferrell stated in his 2019 SEPA scoping input letter to the Port, the DEIS should re-analyze SAMP noise impacts using a single-event noise metric based on recent state-of-the-art SEL airport noise analyses from around the country.”

City points to mitigation at other airports

Federal Way also argued that other airports have addressed noise impacts at levels below the 65 DNL threshold:

“Due to lawsuits involving proposed expansion projects, other major airports (for example Minneapolis-St. Paul lnternational) have mitigated noise impacts well below the outdated 65 DNL metric. We and our residents expect to know from a revised SAMP DEIS, specifically, what new initiatives will be implemented to mitigate these additional noise impacts.”

Federal Way says it remains involved

In a follow-up email, the city emphasized that it is actively participating in the Sea-Tac Airport Roundtable (StART).

The city also prepared this video for people unable to attend a SAMP-related public meeting.