Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 1 of 8
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PORT OF SEATTLE 3
RESOLUTION NO. 3821 4
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A RESOLUTION of the Port of Seattle Commission adopting SEA Tree 6
Replacement Standards for Airport Activities Area and the 7
SEA Land Stewardship Plan for Seattle-Tacoma 8
International Airport. 9
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WHEREAS, the Port of Seattle is a special purpose government with a mission to 11
promote economic opportunities and quality of life in the region by advancing trade, travel, 12
commerce and job creation in an equitable, accountable and environmentally responsible 13
manner; and 14
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WHEREAS, the Port operates essential transportation infrastructure at Seattle-Tacoma 16
International Airport (SEA), to ensure the efficient movement of people and goods in the 17
region, and must utilize land for development and operations; and 18
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WHEREAS, the Port is committed to responsible management of its natural resources 20
because trees, forests, and other habitat are incredibly important to the environment and 21
provide tremendous benefits to our neighboring communities and the public; and 22
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WHEREAS, the Port continues to ensure that all its operations and development 24
activities are in compliance with city, state, and federal development standards; and 25
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WHEREAS, the Port continually strives to go beyond the minimum regulatory 27
requirements to address environmental justice, improve environmental health, increase 28
climate resilience, and improve habitat for fish and wildlife; and 29
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WHEREAS, the Port Commission, through Resolution No. 3741, adopted the Interlocal 31
Agreement with the City of SeaTac defining the “Airport Activity Area” inside which Port 32
capital development activities are subject to compliance with the Airport Building Department 33
development standards; and 34
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WHEREAS, Burien, Des Moines, and SeaTac municipal codes all include tree 36
replacement standards for development, while no tree replacement standards are currently in 37
effect for the Airport Activity Area; and 38
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WHEREAS, the Port Commission, through Order No. 2023-10, adopted Environmental 40
Land Stewardship Principles and Strategies to guide development of Port environmental land 41
stewardship efforts around trees, forest, and other habitat to further improve the livability, 42
accessibility, and environmental health of the region; and 43
Item Number: 10c_reso
Meeting Date: March 12, 2024
Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 2 of 8
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WHEREAS, the Environmental Land Stewardship Principles recommend a holistic 45
ecological approach, ensuring development and other land use projects replace the ecological 46
function and community benefits of any cleared trees; and 47
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WHEREAS, the SEA Tree Replacement Standards for Airport Activity Area and SEA Land 49
Stewardship Plan emphasize healthy and self-sustaining forests in harmony with the 50
Commission values recommended in the Environmental Land Stewardship Principles; and 51
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WHEREAS, the Land Stewardship Plan is a living, operational document used as a 53
framework to steward trees, forests, and other habitats that will be updated administratively 54
on a periodic basis to reflect new and changing conditions. 55
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NOW, THEREFORE, BE IT RESOLVED by the Port of Seattle Commission as follows: 57
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SECTION 1. Port of Seattle Commission adopts the Tree Replacement Standards 59
policy directive, attached as Exhibit A to this resolution in alignment with the Commission Order 60
No. 2023-10: Port-wide Environmental Land Stewardship Principles and Strategies. 61
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SECTION 2. Port of Seattle Commission adopts the SEA Land Stewardship Plan, 63
attached as Exhibit B to this resolution, in alignment with the Commission Order No. 2023-10: 64
Portwide Environmental Land Stewardship Principles and Strategies. The Plan will be updated 65
administratively, as needed. 66
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ADOPTED by the Port of Seattle Commission at a duly noticed public meeting thereof, 68
held this ______ day of March, 2024, and duly authenticated in open session by the signatures 69
of the Commissioners voting in favor thereof and the seal of the Commission. 70
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Port of Seattle Commission 82
Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 3 of 8
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EXHIBIT A to Resolution No. 3821 84
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SEA Tree Replacement Standards For Airport Activity Area 86
As proposed March 12, 2024 87
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SECTION 1. Purpose. 89
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Port-owned properties are subject to tree replacement standards established by the local 91
jurisdictions in which the properties are located. Certain Port-owned properties within the SEA 92
airport boundary, the “Airport Activity Area” as defined in the 2018 Port-SeaTac Interlocal 93
Agreement, attachment to Resolution 3741, are not subject to City of SeaTac tree replacement 94
standards. 95
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The purpose of this policy directive is to offer tree replacement standards for the “Airport 97
Activity Area”, that may be impacted by Port operational and development purposes, 98
consistent with the Port-wide Environmental Land Stewardship Principles. 99
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Tree replacement standards include components for retention of existing trees on the 101
development site and replacing trees permitted to be cleared. The retention requirement 102
recognizes the intensive industrial and commercial land use that typifies Port development. 103
The replacement standard relies on a holistic ecological approach that gives credit for planting 104
trees and for taking actions to improve forest health at off-site locations, including protecting 105
the life of existing high-value trees and restoring areas infested with invasive plants to native 106
vegetation. 107
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This approach is consistent with the Environmental Land Stewardship Principles, which 109
recommends using holistic ecological methods and practices, as well as the SEA Land 110
Stewardship Plan (Exhibit B), which includes site resource documentation that informs project 111
planning and design, including tree replacement. 112
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SECTION 2. Definitions 114
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When used in this policy directive, the following words and phrases shall have the meanings 116
given below unless the context in which they are included clearly indicates otherwise: 117
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A. Adjacent location. Port-owned property contiguous to and easily and directly accessible 119
from the development footprint. 120
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B. Airport Activity Area (AAA). The area defined in the 2018 Port-SeaTac Interlocal 122
Agreement, attachment to Resolution No. 3741, as being within Airport Building 123
Department jurisdiction and subject to the tree replacement standards herein. 124
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C. Forest. An area with predominant tree canopy cover. 126
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D. Forest cover. The proportion of tree canopy in a given area. Includes trees in forested 128
Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 4 of 8
areas and tree groves as well as individual trees. 129
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E. High-value tree. A tree providing significant ecological function due to size, maturity, 131
species, or location in a tree grove. In general, trees greater than 30 inches diameter at 132
breast height (30 inches DBH) are considered high-value due to their size. All regulated 133
native conifers occurring within a tree grove that contains at least three trees greater 134
than 30” DBH are considered to be high-value trees. 135
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F. Invasive species. Non-native plant species that aggressively colonize areas, threating 137
native plants and habitat as well as infrastructure. Invasive species cause environmental 138
and economic harm. Invasive species prioritized for management are listed on King 139
County’s Noxious Weeds List. 140
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G. Off-site location. Distant from and not directly associated with a proposed development 142
footprint. 143
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H. On-site location. Within the development footprint, which includes the building and 145
supporting infrastructure (e.g., parking areas, landscaping; exterior fencing and 146
lighting). 147
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I. Port-wide Environmental Land Stewardship Principles. Refers to Order 2023-10, 149
approved by the Commission on July 11, 2023. 150
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J. Regulated Tree. A tree that is subject to replacement according to the development 152
standards herein. 153
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K. Tree. A woody perennial plant with a single stem growing to more than 30 feet at 155
maturity and bearing lateral branches beginning some distance above the ground. 156
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L. Tree Grove. A group of trees that grow close together, generally without many bushes 158
or other plants underneath, and anchored by at least three high-value trees. 159
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SECTION 3. Scope and Applicability. 161
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These standards pertains to the “Airport Activity Area”, as defined in the 2018 Port-SeaTac 163
Interlocal Agreement, attachment to Resolution No. 3741. 164
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SECTION 4. Responsibilities. 166
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The Port’s Executive Director, or a delegate, shall ensure the Tree Replacement Standards 168
Policy Directive is implemented and adequately funded, and that the Policy Directive is 169
integrated into capital project plans and key operational decisions in the Airport Activity Area, 170
as defined in the 2018 Port-SeaTac Interlocal Agreement, attachment to Resolution 3741. The 171
Executive Director shall also ensure that outcomes associated with the application of the Tree 172
Replacement Standard Policy Directive are transparently documented and publicly exhibited so 173
that the Port of Seattle Commission can review, in public, how projects are meeting its Tree 174
Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 5 of 8
Replacement Standards. The Executive Director shall also ensure that the program evaluation 175
meets the purpose and timeliness identified in Section 6 of this policy. 176
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SECTION 5. Policy. 178
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A. Tree Replacement Standards. 180
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(1) Regulated Tree. A regulated tree must be replaced according to the 182
standards herein. Regulated trees meet one of the following criteria: 183
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a. equal to or greater than six inches diameter at breast height (6” DBH); or 185
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b. any tree planted by design as part of landscaping for existing development. 187
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(2) Tree Retention. The intensive industrial/commercial land use supporting 189
airport operations provides limited opportunity for retaining existing trees on 190
development sites. Therefore, projects with clearing impacts will not be 191
subject to a minimum retention requirement but shall retain existing trees to 192
the extent practicable. 193
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(3) Tree Replacement. If a Regulated Tree is to be cleared: 195
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a. It must be replaced at a 4:1 ratio. 197
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b. Replacement uses a “stewardship credit” approach for which a replacement 199
credit can be generated the following ways: 200
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i. Tree Planting. Plant one tree in an on-site or off-site location, or 202
ii. Invasive removal. Remove 200 square feet of invasive vegetation 203
from an off-site location and replanting the area with native 204
understory vegetation, or 205
iii. Tree Protection. Protect the life of one tree using one of the following 206
means: 207
a. Retain one regulated tree within the development footprint 208
through project design and construction methods, or 209
b. Protect the life of one high-value tree in an off-site location from 210
invasive threats (e.g., removing English ivy from the tree trunk 211
and vicinity). 212
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B. The tree replacement standards shall be supplemented by specific design criteria, to be 214
applied as part of capital project planning and design. The criteria ensure that tree 215
replacement concepts and designs are consistent with Environmental Land 216
Resolution No. 3821, SEA Tree Replacement Standards and Land Stewardship Plan Page 6 of 8
Stewardship Principles, operational requirements, and equity policy. 217
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(1) Tree replacement requirements are to be evaluated using site inventories for 219
the development site and potential adjacent and off-site planting areas. Site 220
inventories are required to be completed as part of the project planning and 221
design. 222
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(2) Stewardship credits generated by tree planting shall account for greater than 224
50% of the replacement requirement. 225
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(3) Tree replacement shall be prioritized and maximized first on-site, then adjacent 227
to the development footprint before utilizing off-site locations. 228
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(4) For tree replacement that occurs on-site or at adjacent locations, projects shall 230
consider the potential for employee access to tree replacement areas to 231
improve project equity and employee wellness benefits. 232
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(5) Designed tree replacement shall be consistent with rules for safe aviation, 234
including the Wildlife Hazard Management Plan; Flight Corridor Safety Program 235
vegetation height limits and regulatory requirements; and all applicable 236
environmental laws and regulations. 237
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SECTION 6. Program Evaluation. 239
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The Executive Director, or a delegate, shall monitor and evaluate progress towards achieving 241
the policy directive. This monitoring and evaluation shall include but not be limited to the 242
following: 243
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A. Documentation. In alignment with the Airport Building Department permitting, capital 245
projects are required to inventory and documents all trees in the development 246
footprint and trees that are planned for clearing. Projects that clear trees must create 247
a tree replacement plan documenting how trees will be replaced and complete an 248
accounting worksheet demonstrating tree replacement requirements are achieved. 249
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A comprehensive database will be developed and maintained documenting the 251
location and extent of all tree clearing impacts and replacement actions (tree 252
planting, tree protection, invasive restoration). 253
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B. Reporting. Documented tree replacement pursuant to the SEA Tree Replacement 255
Policy Directive will be reported annually in the Environment and Sustainability Center 256
of Expertise’s Key Performance Indicators. Staff will present a summary of Key 257
Performance Indicators annually to the Sustainability, Environment, and Climate 258
Committee. 259
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C. When substantive administrative updates to the SEA Land Stewardship Plan are made, 262
Commissioners will be notified through the Sustainability, Environment, and Climate 263
Committee. 264
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EXHIBIT B to Resolution No. 3821 266
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SEA Land Stewardship Plan 268
(attached separately as Attachment 1) 269
