Hello and welcome to the virtual public workshop for the Part 150 study for Seattle-Tacoma International Airport. We appreciate you attending this workshop today and your participation and input is a key component of this study. This series of workshops is a continuation of the in-person workshops that were held starting on September 30th. Today we will review the draft noise exposure maps and how they were developed for SEA as well as how to submit formal comments. The slides being presented are also available on the study website at seapart150.com/documents.
Title 14 Code of Federal Regulations or CFR Part 150 establishes the process for preparing noise exposure maps or NEMs and noise compatibility programs or NCPs. Together they are referred to as a Part 150 study. The purpose of a Part 150 study is to determine the existing and future noise conditions in the vicinity of an airport, educate communities on the federal process and what can and cannot be done to address aircraft noise concerns, and submit locally endorsed recommendations to the Federal Aviation Administration or FAA regarding noise abatement or reduction measures. Part 150 studies are voluntary and must adhere to 14 CFR Part 150 requirements. This is the fourth Part 150 study conducted for SEA with the most recent update completed in 2014.
The Part 150 study is split into two phases. The noise exposure map or NEM phase and the noise compatibility program or NCP phase. This study is currently nearing the end of the NEM phase. The next step in the NEM phase is to publish the draft NEM report. Following the public comment period, we will address your formal comments and the NEM report will be submitted to the FAA for acceptance. We are beginning to transition into the NCP phase of the study as we near completion of the NEM report. The purpose of the NCP is to identify noise abatement, land use, and programmatic strategies to reduce aircraft noise impacts on surrounding communities.
Aircraft noise is regulated at the federal level. The FAA has jurisdiction over civilian aircraft noise and will accept the NEMs once they’re found in compliance with 14 CFR Part 150. The FAA also approves flight procedures, controls aircraft noise at its source by setting noise certification standards and ensures that pilots and aircraft are safe to fly. State and local governments establish the land use compatibility framework. This includes promoting compatible land use through methods such as zoning and mandating sound insulating building materials. Airport authorities such as the Port are the operators of airports and are primarily responsible for building and managing airport infrastructure such as the terminal and runways. However, airports have very limited authority as federal law takes precedence over state and local regulations.
The day-night average sound level or DNL represents the total cumulative exposure to sound expressed in decibels or dB averaged over a 24-hour period. DNL considers the total number of operations at an airport over the course of a day. DNL also takes into account the time aircraft operations occur. And to reflect the increased sensitivity to noise at night, DNL uses a 10 decibel weighting for events that occur between the hours of 10:00 p.m. and 7 a.m. Because noise is measured on a logarithmic scale, this equates each nighttime event.
DNL also uses the concept of average annual day, which reflects a year’s worth of airport operations averaged into a single representative day. FAA requires the use of DNL for all airport noise assessments, including Part 150 studies.
Regulatory guidelines for noise and land use compatibility are included in 14 CFR Part 150 Appendix A, Table 1. The FAA has established DNL 65dB as the significance threshold for noise sensitive land uses such as residential areas. All land use types located outside of the DNL 65 contour are considered compatible for the purposes of 14 CFR Part 150. However, the regulation does allow for the adoption of local land use standards for land use compatibility planning purposes as appropriate. The Part 150 process is the airport sponsor’s way to improve the compatibility between the airport and land use and surrounding communities. Noise sensitive land uses include residential, places of worship, schools, libraries, hospitals, and more. Existing and future land uses surrounding the airport are identified and categorized for the NEM report that is expected to be published later this year and will be posted on the study website at seapart150.com.
Noise modeling provides airport sponsors with key insights into the current and projected noise levels in the vicinity of an airport and in nearby communities. It shows how noise exposure may change over time and how it’s influenced by factors like aircraft type, flight paths, and operating procedures. As required by the FAA, this study uses the FAA’s noise model, the Aviation Environmental Design Tool, also referred to as AEDT.
Data inputs used in the modeling process to determine the amount of noise exposure include the aircraft type, the distance to the aircraft’s destination, also called stage length, the number of aircraft operations, and arrival and departure times. Data inputs used in the modeling process that determine the distribution of noise exposure include airport runway use, flight track locations and usage, local topography or terrain, and airport meteorological conditions such as average temperature, wind speed and direction, and humidity. All of these inputs are processed through AEDT to generate the noise contours we’ll review later.
For this Part 150 study, aircraft operations were based on the airport’s Sustainable Airport Master Plan Near-Term Projects Environmental Assessment or SAMP.
The Port in consultation with the FAA determined the operations developed for the EA for the 2022 existing conditions and 2032 forecast conditions are compliant with 14 CFR Part 150 requirements and are used as the NEMs for this Part 150 study. This slide presents estimated annual aircraft operations for the various categories of aircraft operating at the airport. Total annual aircraft operations are anticipated to increase by roughly 74,000 by 2032 with much of the increase forecast for additional passenger and cargo jet operations.
On the other hand, passenger turboprop propeller aircraft operations are expected to be entirely phased out by 2032.
The slide also presents the estimated distributions of aircraft operations at the airport by time of day for arrivals and departures. Nighttime arrivals are anticipated to increase by approximately 2% by 2032, while nighttime departures are anticipated to decrease by roughly the same percentage. Please note that all of the data and references used to populate the tables in this presentation will be included in the draft NEM report.
Stage length is the distance an aircraft flies from one airport to another and is reflective of a departing aircraft’s weight. Generally, aircraft with longer stage lengths are larger and heavier and will require more time and distance to climb to altitude, resulting in higher noise exposure levels on the ground. This is demonstrated by the figure on the left, which provides a conceptual example of how stage length affects the climb performance of a Boeing 737-800. The table on the right presents the trip lengths that are assigned to the departure stage lengths defined in the AEDT model and the table on the bottom presents the distribution of departure stage lengths at SEA for all aircraft in 2022 and 2032 respectively.
The majority of departing aircraft are between stage length 1 and 4 for both study years, which is representative of a trip length of less than 2,500 nautical miles.
The prevailing winds at SEA create two distinct operating configurations referred to as north flow and south flow. Since aircraft typically take off and land into the wind during north flow, arrivals approach the airport from the south, heading north and departures take off from the airport to the north. This represents approximately 30% of the operations at SEA. During south flow, which is approximately 70% of the operations, the wind is from the south and thus the arrivals approach from the north heading south and departures take off to the south. Flight tracks reflect the paths aircraft fly. The combination of the location and utilization of these paths contribute to the shape of the noise contours around the airport with the most utilized paths generally driving the areas with larger noise contours. This slide presents a sample of aircraft flight tracks during both north flow and south flow. The image on the left presents north flow operations for the period of August 20th to 26th. Conversely, the image on the right presents a sample of aircraft flight tracks during south flow for the period of February 17th to 23rd. In both figures, aircraft departure flight tracks are depicted in green and arrival flight tracks are depicted in blue. For a closer look at the graphics we’re presenting, a high-resolution copy of this presentation is available on the study website at seapart150.com.
Runway utilization is another important factor affecting the size and shape of the noise contours. Higher runway utilization generally results in larger noise contours emanating off that runway. It is important to note the airport cannot control runway utilization. That is determined by the FAA air traffic control tower and may be impacted by wind and weather conditions, construction on the airfield, aircraft performance, and pilot preferences. These graphics present the modeled runway utilization for arrivals and departures for the 2022 existing conditions NEM. In 2022, runway 16 Left and 34 Right are the primary runways used for departures, with runway 16 Left accounting for over 65% of all aircraft departures. In contrast, runway 16 Right and 34 Left were the primary runways for arrivals, with runway 16 Right accounting for approximately 63% of all arrivals.
These graphics present the modeled runway utilization for arrivals and departures for the 2032 future conditions NEM. As activity increases at the airport through 2032 in addition to airfield and taxiway improvements, it is anticipated that roughly 20% of all departure aircraft will shift from runway 16 Left to runway 16 Center under south flow. Runway utilization for arrival aircraft is not expected to change.
This slide presents modeled flight tracks for both the existing and future NEMs based on the flight track data presented in the previous slides. The figure on the left presents the modeled flight tracks for aircraft operating in north flow and the figure on the right presents the modeled flight tracks for aircraft operating in south flow. Between the 2022 and 2032 scenarios, it is not anticipated there will be substantive changes to aircraft flight procedures that would result in changes to the modeled flight tracks. For both figures, aircraft arrival flight tracks are depicted in blue, departures in green, and missed approaches in pink.
These figures present the density of aircraft flight paths recorded from a rolling calendar year of radar data collected at the airport from September 2024 to August 2025 for north and south flow operations. The figure on the left presents north flow operations and the figure on the right presents south flow. The areas with the greatest concentrations or density of flight paths are presented as warmer red colors and areas with lesser concentrations are cooler blue colors.
The figures on this slide present the altitudes of aircraft flight paths in feet above mean sea level or MSL recorded from a sample of radar data collected at SEA between August 20th to 26th 2025 for north flow operations. The figure on the left depicts arrivals and the figure on the right depicts departures. Flight paths with the lowest altitudes are presented as warmer red colors and highest altitudes as cooler blue and purple colors.
Similar to the last slide, the figures on this slide present the altitudes recorded from a sample of radar data collected at SEA between February 17th to 23rd, 2025 for south flow operations. Similar to north flow operations, the figure on the left presents arrival operations and the figure on the right presents departures.
The draft NEMs include the 2022 existing condition and 2032 future condition with the future scenario accounting for anticipated changes in aircraft fleet mix, runway use, and operations. The 2032 NEM will be the basis for evaluating potential NCP recommendations and serve as the basis of comparison for the effectiveness of potential noise abatement measures. The figure on the left presents the draft NEM for 2022 and the figure on the right presents the draft NEM for 2032. Both figures present DNL 65, 70 and 75 noise contours which are represented by solid black, red and blue lines respectively. The contours are overlaid with existing land use and depict aircraft noise exposure with regards to land uses in the vicinity of the airport.
This table presents land uses contained within the DNL 65 or higher contours for the 2022 NEM. In total, over 5,600 acres of land are exposed to DNL 65 or higher, nearly 3,000 of which are located outside of the airport property. There are mixed-use properties, mobile homes, as well as single and multi-family residences within the 2022 NEM. In total, 6,915 housing units are exposed to DNL 65 or higher. These tables present an overview of noise sensitive sites contained within the DNL 65 or higher contours for the 2022 NEM and details the noise sensitive sites within each contour interval. Noise sensitive sites include residential housing units, places of worship, schools, hospitals, historic resources, libraries, and nursing homes. Future sound insulation program eligibility will be evaluated during the NCP phase based on the 2032 NEM.
Consistent with the 2022 NEM, this table presents land uses contained within the DNL 65 or higher contours for the 2032 NEM. In total, over 6,500 acres of land are exposed to DNL 65 or higher, nearly 4,000 of which are located outside of airport property. In total, 9,941 housing units are exposed to DNL 65 or higher in the 2032 NEM.
Similar to 2022, this slide presents noise sensitive sites exposed to DNL 65 or higher in the 2032 NEM. It should be noted that these figures are preliminary and will be subject to further analysis during the NCP phase. It should not be interpreted as a final determination of eligibility or need for sound insulation.
Comparing the contours, the 2032 contours are larger across all contour intervals. The contours for both draft NEMs for the DNL 65, 70, and 75 are represented by black, red, and blue lines respectively. The 2022 contours are presented as solid lines where the 2032 contours are presented as dashed lines. Both sets of contours are overlaid with existing land use.
Comparing noise exposure between the 2022 and 2032 NEMs, the top table illustrates that overall there are approximately 1,000 more acres of land exposed to DNL 65 or higher in 2032 when compared to 2022. Likewise, for residential land uses, there are 500 more acres of residential land exposed to DNL 65 or higher in the 2032 NEM when compared to 2022.
Considering noise sensitive sites, the bottom table illustrates the 2032 NEM exposes 3,026 more housing units, three more places of worship, three more schools, and 15 more nursing homes to noise levels of DNL 65 or higher when compared to 2022.
With the completion of the NEMs, we are preparing the draft NEM report which is expected to be published later this year for review and comment. Following review of all public comments, a final NEM report will be submitted to the FAA for acceptance. As we wind down this phase, we will begin the NCP phase of the study, which we will discuss next.
The purpose of an NCP is to identify noise abatement, land use, and program management strategies to reduce aircraft noise impacts on surrounding communities and propose measures to improve compatibility between airport operations and non-compatible land uses based on the NEMs. Each NCP measure is reviewed by the FAA for technical accuracy, alignment with FAA policy, and the effectiveness of proposed measures. Once the FAA completes review of the NCP, they will issue an approval or disapproval for each measure proposed in the NCP.
In developing NCP measures for submittal to the FAA, measures must include all of the items listed on the right side of the slide. The most prominent criteria include reducing non-compatible land use and/or prevent future non-compatible land uses within the DNL 65 and higher, ensuring the safety and efficiency of the airport is not impacted, and exclude unjust discrimination against certain types of aircraft. If an NCP measure does not address each of these considerations listed on the slide, it will not be approved by the FAA. Likewise, the FAA will not approve NCP measures that redirect noise from one community at the expense of another.
When considering the development of potential NCP measures, it is important to distinguish between those measures that are used for noise abatement versus noise mitigation.
Noise abatement measures are those that reduce noise exposure by moving the source of the noise, such as by moving an aircraft flight path or changing the utilization of an airport’s runways. Alternatively, noise mitigation measures address land uses that are non-compatible with airport noise and can be either preventative, which address future land uses, or remedial that address existing land uses. An example of a preventative measure would be to change zoning on undeveloped land to prevent non-compatible development in areas within DNL 65.
An example of a remedial measure would be providing sound insulation to residences already located within DNL 65.
Below are some common examples of measures included in NCPs grouped by noise abatement, land use, and programmatic strategies, respectively. Other measures, such as those proposed by stakeholders, may also be included in the NCP. We’ve already mentioned example noise abatement and land use measures. Examples of program management strategies often include noise monitoring and reporting, pilot outreach and education, and future Part 150 study updates.
As noted previously, the NEM phase of this study is drawing to a close. The draft NEM report will be published later this year and the study team will review comments and prepare a final NEM report for submittal to the FAA in early 2026. Potential NCP recommendations will be screened and analyzed throughout the spring and summer of 2026.
Once the NCP recommendations are finalized, they will be included in an NCP report and another series of public workshops will be held. We anticipate that will occur late next year. We also anticipate the NCP will be submitted to the FAA in 2027.
This information is separate from the Part 150 study process we are discussing tonight, but was included at the workshop since it’s related to non-compatible land use. The Port of Seattle has a long history of conducting sound insulation programs for the airport. Since the program began in 1985, the Port has insulated over 9,400 single family homes, seven condos, 11 schools, and is currently in the process of providing insulation to nine apartment complexes, and three places of worship. To be eligible for the current program, a resident must reside within the current noise remedy boundary and is also subject to additional FAA requirements. For questions and additional information on this program, please email soundinsulation@portseattle.org.
In addition to the Port’s current sound insulation program, the Port recently started a sound insulation repair and replacement pilot program. To be eligible for participation in the pilot program, your home must be located inside the current noise remedy boundary, insulated prior to 1993, and acoustically test at or above 45 dB DNL interior. For questions and additional information on the pilot program, please email searepairplacepilot@portseattle.org.
To submit written comments on the NEMs or suggestions for the NCP, you may email them to p150@portseattle.org via the comment portal on seapart150.com or by mail to the address shown on this slide. We greatly appreciate your attendance and participation in this virtual public workshop for the SEA Part 150 study and we look forward to answering your questions shortly.