Port Packages mapped: eligibility over time

Changes 1985-2032

• The black outline depicts the 1985-2013 Part 150 noise contour.
• The light orange rectangle is the 92 sq mile area defined under State of Washington law (RCW 53.54.020) that is eligible for funding to mitigate noise impacts–but only those generated by Sea-Tac Airport.
• All sound insulated homes inside the original DNL65 (1985-2032).
• Sound insulated homes inside the current and expected DNL65 (2018-2032).
• Purgatory Packages — sound insulated homes outside the current DNL65.

This slideshow is excerpted from our Port Packages Mapped project. About 9,400 structures have been sound insulated since the Port of Seattle began to tackle issues of noise after the Second Runway in the 1970. At that time, addressing noise meant abatement (property buyouts) and establishing the ‘noise lands’ around the perimeter. Only a limited number of mitigations (sound insulation) were tried before 1993.

The first Part 150 Study was completed in 1985, establishing the noise contour depicted in Slide #1. That boundary remained in place until 2013. The vast majority of sound insulated homes were completed within that original boundary between 1998-2005 in advance of the Third Runway. The policy had been to treat single family homes first. Several hundred homeowners declined to sign avigation easements and several apartment buildings were placed at the back of the queue.

The noise contour shrank dramatically with the 2013 Part 150 Study, leaving approximately 1,100 houses and apartments untreated. Since that time, the Port has offered avigation easements when single family homes changed ownership, finally offering sound insulation to multi-family structures via its 2020 Accelerated Sound Insulation Program.

The reason for the shrinkage has to do with the formula by which DNL65 is calculated. That formula skews heavily towards the noise profile of individual aircraft, not the quantity or sequencing of flights. By 2013, the types of aircraft using Sea-Tac had become quieter, although the effect on public health had become much worse due to peak periods where flights are now often less than one minute apart.

Current federal law provides Port Package update funding for homes treated before 1993. But only if they are within the current DNL65 (Slide #4). We calculate that number as likely being in single digits today.

Purgatory Packages

In 2026, Congressman Smith and Senator Murray were able to obtain an amendment to the Defense Reauthorization Act which will provide for federal reimbursement for Port Package updates (subject to FAA rule making.) But only for homes within the current DNL65 when the project is done. However, the number of homes that were sound insulated between 1993 and today, but which are outside the current or future DNL65 is actually much greater than those inside. We call these Purgatory Packages because they will likely not be eligible for FAA reimbursement in the near term. Those Port Package updates will will require other funding sources–outside of Part 150. The FAA has seemed willing to approve using some types of local airport revenue for noise mitigation outside of Part 150.