COMMISSION 
AGENDA MEMORANDUM                        Item No.          9b 
BRIEFING ITEM                             Date of Meeting      January 28, 2020 
DATE:     January 15, 2020 
TO:        Stephen P. Metruck, Executive Director 
FROM:    Arlyn Purcell, Director, Aviation Environment and Sustainability 
Steve Rybolt, Sr. Environmental Program Manager, Aviation Environment and
Sustainability 
SUBJECT:  Sustainable Airport Master Plan (SAMP) Near-Term Projects (NTP) Environmental
Review Briefing Forecast and Schedule Update 
EXECUTIVE SUMMARY 
This briefing will provide an overview of the results of the forecast update conducted for the
Sustainable Airport Master Plan (SAMP) Near-Term Projects environmental review and the
current schedule.
SUSTAINABLE AIRPORT MASTER PLAN NEAR-TERM PROJECTS ENVIRONMENTAL REVIEW 
The Port of Seattle prepared the SAMP as  a blueprint for changes at Seattle-Tacoma
International Airport (Sea-Tac Airport) to meet future demand. The SAMP planning process was
completed in 2018 and identified a set of Near-Term Projects (NTP) that are planned for
construction by 2027  as well as a Long-Term Vision.  The NTP are the subject of this
environmental review and include more than 30 projects that would improve efficiency, safety,
access to the Airport, and support facilities for airlines and the Airport. 
The Federal Aviation Administration (FAA) initiated a National Environmental Policy Act (NEPA)
Environmental Assessment (EA) and the Port of Seattle (Port) initiated a State Environmental
Policy Act (SEPA) Environmental Impact Statement (EIS) to evaluate and disclose the potential
environmental effects of the NTP.
Scoping, one of the first steps in the SAMP NTP environmental review, was completed on
September 28, 2018. Scoping is an early and open process for determining the scope of issues
that will be addressed in the environmental review document, soliciting input regarding the
NTP  and  reasonable  alternatives,  and  identifying  concerns  regarding  the  potential
environmental effects of the NTP. The resulting comments provided valuable input that led to
several changes to the SAMP NTP environmental review scope.
One key outcome of the scoping process was a decision to review and update the forecast
originally developed in 2015 as part of the SAMP planning work. 

Template revised April 12, 2018.

COMMISSION AGENDA  Briefing Item No. 9b                                  Page 2 of 3 
Meeting Date: January 28, 2020 

FORECAST UPDATE 
The SAMP forecasts for Sea-Tac Airport were completed in 2015 using 2014 as the base year.
Since then, strong economic growth, lower airfares, and airline competition drove passenger
traffic to rise faster than originally forecast. Passenger volume at SEA increased by 40 percent
between 2014-2018. 
The updated demand forecast shows that the airport will reach the 2027 forecast activity levels
for operations by approximately 2022, five years sooner than originally projected, and for
passenger activity by 2023.  However, this forecast only considers demand for services and
does not consider airport constraints such as the availability of gates and aircraft parking.
Gate and aircraft parking constraints will likely limit substantial activity increases at the airport
beyond 2023. In response, the Port, in collaboration with the FAA, developed estimates to
illustrate slower growth scenarios based on facility constraints. There are separate scenarios for
activity with and without the proposed NTP.
This constrained operating growth scenarios will be used as the basis for the SAMP NTP
environmental review analysis.
The FAA approved the updated 2019 demand forecast and concurred with the constrained
operating growth scenarios on January 10, 2020.
2027                                2032 
Aircraft           Passengers           Aircraft           Passengers 
Operations         (millions)         Operations         (millions) 
SAMP Demand
477,000             56.0             527,000             63.0 
Forecast (2015) 
SAMP Updated
Demand           520,000          61.1          557,000          68.2 
Forecast (2019) 
No Action 
Constrained           499,000             58.1             506,000             60.7 
Scenario 
Proposed Action 
Constrained           508,000             59.2             524,000             63.1 
Scenario 
Table 1  SAMP Demand Forecasts and Constrained Scenarios 
The table above shows both forecast activity demand and constrained growth scenarios. The
SAMP Demand Forecast [2015] and SAMP Updated Demand Forecast [2019] are based on
market demand and do not assume  specific assumptions about physical, regulatory,
environmental or other impediments to aviation activity growth. Conversely, the constrained
growth scenarios represent known barriers to growth at Sea-Tac Airport.


Template revised September 22, 2016.

COMMISSION AGENDA  Briefing Item No. 9b                                  Page 3 of 3 
Meeting Date: January 28, 2020 
EXTENDED SCHEDULE 
The forecast update and other scope changes have resulted in an extension of the schedule: 
Update to the demand forecast and development of constrained operating growth
scenarios 
Continued advanced planning coordination 
Additional technical environmental analysis, in response to scoping comments 
Separation of the NEPA and SEPA documents and processes 
Continued extensive stakeholder engagement and community outreach 
Key milestones include: 
Oct. 2020     NEPA EA draft document released for agency and public review 
Nov. 2020     NEPA EA agency and public review complete 
Apr. 2021     NEPA EA final document and decision 
May 2021    SEPA EIS draft document released for agency and public review 
Jul. 2021       SEPA EIS agency and public review complete 
Sep. 2021     SEPA EIS final document 
ATTACHMENTS TO THIS BRIEFING 
(1) Sustainable Airport Master Plan  (SAMP) Near-Term Projects (NTP) Environmental
Review Briefing  Updated Forecast and Schedule PowerPoint presentation 
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS 
February 26, 2019  Commission Briefing: "Sustainable Airport Master Plan (SAMP) Near-
Term Projects (NTP) Environmental Review Briefing  Scoping Report" 
May 8, 2018  Commission Briefing: "Sustainable Airport Master Plan (SAMP) Planning and
Environmental Update" 
February 13, 2018 - Commission Briefing: "Sustainable Airport Master Plan (SAMP) Planning
Update" 
November 10, 2015  Commission Action: "Environmental Review (National Environmental
Policy Act and State Environmental Policy Act) Personal Services Agreement for the
Sustainable Airport Master Plan" 




Template revised September 22, 2016.