COMMISSION AGENDA – Action Item No. 8a Page 2 of 9
Meeting Date: January 28, 2020
Template revised June 27, 2019 (Diversity in Contracting).
Aerial obstruction analysis (Light Detection and Ranging, or LiDAR) conducted in 2018 identified
174 trees as obstructions. The 174 trees are located on properties owned by the Port of Seattle,
other public agencies (WSDOT, Highline School District, and City of SeaTac), and private
properties (Hillgrove Cemetery and residentially and commercially zoned properties in the cities
of Burien, Des Moines, and SeaTac). The 174 trees are a significant reduction from the
approximately 1,600 trees that were originally planned to be removed. The intent is to remove
trees having the highest potential impact to flight operations prior to March 1, 2020, and
complete removal of the remaining trees by December 2020. The port may also remove future
obstructions on properties where obstructions currently exist should the property owner desire
this to occur. This will complete the first cycle of a program to manage obstructions every five
years. Various approaches have been considered for tree replanting, which may include
partnering with other public agencies. Replanting will occur starting in 2021 on properties
where trees have been removed and, to the maximum extent practicable, on sites near the
airport, without creating future obstructions to the flight paths. To date, the Port has replanted
over four-times the number of trees removed and replaced the existing invasive herbaceous
cover with a dense woody native shrub understory.
In implementing the Flight Corridor Safety Program 2019, the port will need to memorialize or
assert its rights to access non-port properties for purposes of tree removal and replanting, and
should seek, in coordination with property owners, permanent easements or other lawful
airport protection privileges for continued, long-term protection of the flight surfaces. For
example, acquiring an easement from property owners will protect against future
encroachments by establishing appropriate height limitations for any trees or other objects
located on the property, and the easement would provide a clear mechanism for the port to
promptly and efficiently address any future obstructions, such as granting the right to access
the property to address an obstruction, upon reasonable notice to the property owner.
JUSTIFICATION
There are several federal and state regulations and requirements that provide justification for
obstruction removal. These regulations and requirements include the following:
1. Federal Requirements for Airport Operators to Control Obstructions
a. Federal Aviation Regulation (FAR) Part 77, “Safe, Efficient Use, and Preservation of
the Navigable Airspace”
b. FAR Part 139, “Certification of Airports”
c. Advisory Circular (AC) AC 150/5300.13A change 1, including “Maintenance of
obstacle clearance surfaces”
d. Grant Assurance 20, “Hazard Removal and Mitigation”
e. Grant Assurance 21, “Compatible Land Use”