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Arborist Report
Tree Cutting and Land Clearing Plan
Boeing Campus, Renton, Wa
September 2017
(Revised August, 2020)
Notice of Disclaimer
Assessment data provided by Davey Resource Group is based on visual recording at the time of inspection. Visual records do not
include testing or analysis and do not include aerial or subterranean inspection unless indicated. Davey Resource Group is n ot
responsible for discovery or identification of hidden or otherwise non-observable risks. Records may not remain accurate after
inspection due to variable deterioration of surveyed material. Risk ratings are based on observable defects and mitigation
recommendations do not reduce potential liability to the City. Davey Resource Group provides no warranty with respect to the
fitness of the trees for any use or purpose whatsoever.
Prepared
For:
Jourden Makinen, WSP USA
33301 Ninth Avenue South, Suite
300
Federal Way, Washington,
98003-2600
Prepared By: Davey Resource Group Inc.
18809 10th Ave NE
Shoreline, WA, 98155
Local Office: 206-714-3147
Corporate Office: 800-966-2021
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September 2017 (Revised 8-14-2020)
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Table of Contents
Table of Contents 2
Revision History 3
Introduction 4
Methods 5
Findings 6
Tree Cutting and Land Clearing Plan 7
Conclusion 14
Appendix A - All Inventoried Trees 15
Appendix B – Tree Retention Worksheet 17
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Revision History
Original Version August 2017.
Tree inspection results, methods and report first drafted.
Revision November 16, 2017.
Construction design variations and additional tree impact was identified.
• Tree #4.5 was identified as a cottonwood and added to the report as proposed for removal.
Revision August 14, 2020
Site visit based on additional construction concerns. Updates to the health and condition assessment of
trees adjacent to anticipated construction activity.
• Tree #1 has grown and been identified as a multi-stem cottonwood averaging 3 inches dbh.
• Tree #9 has declined in health and been downgraded to a poor condition tree.
• Tree #10 has declined in health and been downgraded to a poor condition tree
• Tree #11 has declined in health and been downgraded to a poor condition tree.
• Tree #14 has been added to the proposed removals due to anticipated construction impacts.
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September 2017 (Revised 8-14-2020)
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Introduction
In August, 2017, Davey Resource Group (DRG), a division of The Davey Tree Expert Company, was
contracted by Berger ABAM to conduct a tree inventory of fifty-seven (57) trees, and develop an arborist
report to support application for a Shoreline Substantial Development Permit per City of Renton
regulations. The results will be used to evaluate the potential impacts of excavation and constr uction
activities and determine any tree protection measures required during construction to provide for optimal
tree retention while allowing for necessary site construction activities. This report includes the information
required to obtain a Shoreline Substantial Development Permit from the City of Renton.
There are many factors that can limit specific and accurate data when performing evaluations of trees,
their conditions, and values. The determinations and recommendations presented here are based on
current data and conditions that existed at the time of the evaluation and cannot be a predictor of the
ultimate outcomes for the trees.
The purpose of this report is to provide the details of the inventory and recommended tree protection
measures, including an assessment of current condition, health, and recommendations for maintenance.
The findings in this report can be used to make decisions about tree protection fencing, pruning, and plant
health care.
Site Overview: Blue points illustrate general tree locations on Boeing Campus
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Methods
An International Society of Arboriculture (ISA) Certified Arborist and Certified Tree Risk Assessor (Ian
Scott, PN-5408AUM) from Davey Resource Group conducted the assessment of the trees on August 22,
2017. The trees were assessed by their location, size, current condition, and overall health. The data
was then analyzed with DRG’s Tree Protection Action Key (TPAK), which computes a multi-faceted
condition rating and provides the calculated critical root zones (CRZs).
Only a visual inspection was used to develop the findings, conclusions, and recommendations found in
this report. Numerical values were assigned to grade the attributes of the trees, including structure and
canopy health, and to obtain an overall condition rating. No physical inspection of the upper canopy,
sounding, root crown excavation, and resistograph or other technologies were used in the evaluation of
the trees.
Attributes
Location was recorded based on geolocation on an aerial photo, and reported as GPS coordinates.
Tree # was assigned.
Species (botanical name) was identified, including cultivars where applicable (Table 1).
Diameter at Breast Height (DBH) was generally measured at 4’6” above grade. Where trees had
multiple stems, the reported DBH is the average of all stems.
Height was estimated in feet.
Canopy Radius was estimated in feet.
Condition was assessed by applying a numerical rating to the health and structure to roo ts, trunks,
scaffold branches, twigs, and foliage, and calculating the average of these values to categorize trees as
good, fair, poor, or dead.
Condition Notes recorded issues that may merit maintenance, or additional assessment, such as
deadwood, decay, lean, and vines.
Table 1. Common and Botanical Names of Inventoried Trees
Common Name Botanical Name
maple, bigleaf Acer macrophyllum
Scouler's willow Salix scouleriana
maple, vine Acer circinatum
Cottonwood, black Populus trichocarpa
aspen, quaking Populus tremuloides 'erecta'
Port Orford cedar Chamaecyparis spp.
cascara buckthorn Rhamnus purshiana
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Findings
Species
The species are locally adapted trees.
The most prevalent species inventoried
were quaking aspen (Populus
tremuloides, 45%) followed by Port Orford
cedar (Chamaecyparis lawsoniana, 23%),
and black cottonwood (Populus
trichocarpa, 14%)
Health and Structure
A combined health and structure average
rating was calculated for the population. The
vast majority of trees (50 trees, 89%) are in
good condition. Six trees (9%) are in fair/poor condition, and one is dead. This assessment allows
managers to anticipate the trees’ ability to withstand construction pressures, as trees in good condition
are more resilient. Trees in fair health and structure can often be improved with structural pruning or plant
health care.
Relative Age Distribution
Because the inventoried trees add annual
growth rings to their trunks each year,
their relative age can be approximated by
understanding the distribution of
diameters measured at breast height
(DBH) or 4.5’ above soil grade. The
inventoried trees are young to
established, with 29 trees, (52%) under 7”
DBH and 22 (39%) 7-13” DBH. When
considering tree resilience during
protection, a young and newly
established population is ideal as these
are often able to rebound quickly despite
some root zone disturbance.
Significant trees
The City of Renton considers significant trees black cottonwood over 8” DBH and other species over 6”
DBH. The inventoried trees include six (6) significant black cottonwood, and 33 significant trees of other
species, for a total of Thirty-nine (39) significant trees. Three (3) significant trees are proposed to be
removed.
Species Distribution
Age-class distribution based on Diameter at Breast
Height (dbh).
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Tree Cutting and Land Clearing Plan
Tree Protection in Construction
Construction activities can have significant impacts on nearby trees for many reasons. Roughly one half
of a tree’s biomass is underground in the form of structural and absorptive roots. These roots take up
water and nutrients that trees need to survive, so minimizing impact to these roots is crucial to reducing
tree impacts during construction. Roots can be damaged by even light-weight equipment being driven in
the root zone, an impact that may not be visible until the tree begins to show signs of stress months or
years later. Another root impact occurs when materials are improperly stored or disposed of in the root
zone. This can injure tree roots and contaminate soil. Finally, an obvious impact can occur when
equipment damages trunks and branches, To avoid these impacts, it is a best management practice to
establish fenced tree protection zones to exclude any grading, trenching, soil compaction, material
storage, or mechanical damage. These tree protection zones are based on calculated critical root zones
(CRZs), and have been identified for the Boeing Campus in Renton based on the proposed construction
activity. Any tree that will have major encroachments into the CRZ that will cause the tree to become
hazardous are recommended for removal, rather than tree protection.
Removal
Due to the removal of underground utilities into the critical root zones, the following five (5) trees are
identified for removal. Tree #4 and #4.5 are considered significant trees according to the City of Renton
definition. (Table 2, Figure 1). Tree #4 is a multi-stemmed vine maple with most stems averaging 1-2
inches in diameter.
Table 2. Trees Identified for Removal
Tree # Common Name Condition
Rating DBH (In.)
Canopy
Width
(Ft.)
Hei
ght
(Ft.)
Significant tree
in Renton
3 Cascara
buckthorn Good 1 5 10 No
4 maple, vine Good 8
(10+ Multi-stem) 14 6 Yes
4.5 Cottonwood,
black fair 12 12 40 Yes
9 willow, Scouler's Good 4 8 30 No
14 Cottonwood,
black Good 10 15 40 Yes
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Figure 1. Illustration showing approximate location of proposed tree removals.
Remove Tree
#3, #4, #4.5
Remove
Tree #9
Remove
Tree #14
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September 2017 (Revised 8-14-2020)
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Crown Raising
There are thirty-seven (37) trees along the fence in the proposed work area that can be retained during
construction with crown raising, a type of pruning that removes lower limbs. This type of pruning allows
tree retention along with necessary site activities, and reduces the likelihood of conflict and mechanical
damage to tree limbs. These trees are not in the wetland area, but it appears that most are within the
critical area defined by the City of Renton. They are not trees owned by Boeing, but are immediately
adjacent to the Boeing Property.
Table 3. Trees identified for Crown Raise Pruning
Tree # Common Name
Condition
Rating DBH (In.)
Canopy Width
(Ft.)
Height
(Ft.)
Significant tree in
Renton
19 aspen, quaking Good 12 6 55 Yes
20 aspen, quaking Good 12 8 55 Yes
21 aspen, quaking Good 12 10 60 Yes
22 aspen, quaking Good 12 7 60 Yes
23 aspen, quaking Good 12 6 60 Yes
24 aspen, quaking Good 12 8 60 Yes
25 aspen, quaking Good 12 8 60 Yes
26 aspen, quaking Good 12 8 60 Yes
27 aspen, quaking Good 12 12 60 Yes
28 aspen, quaking Good 12 8 60 Yes
29 aspen, quaking Good 12 9 60 Yes
30 aspen, quaking Good 12 8 60 Yes
31 aspen, quaking Good 12 8 60 Yes
32 aspen, quaking Good 16 10 60 Yes
33 Port Orford cedar Fair 6 0 60 Yes
34 aspen, quaking Good 6 6 50 Yes
36 aspen, quaking Good 3 10 20 No
37 aspen, quaking Good 6 6 20 Yes
38 Port Orford cedar Good 6 8 20 Yes
39 aspen, quaking Good 8 0 20 Yes
40 Port Orford cedar Good 8 6 30 Yes
41 Port Orford cedar Good 8 6 30 Yes
42 aspen, quaking Good 6 8 30 Yes
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Tree # Common Name
Condition
Rating DBH (In.)
Canopy Width
(Ft.)
Height
(Ft.)
Significant tree in
Renton
43 aspen, quaking Good 6 6 40 Yes
44 Port Orford cedar Good 4 6 30 No
45 Port Orford cedar Good 4 8 30 No
46 aspen, quaking Good 6 8 40 Yes
47 Port Orford cedar Good 6 6 40 Yes
48 Port Orford cedar Good 6 8 30 Yes
49 aspen, quaking Good 6 10 30 Yes
50 Port Orford cedar Good 7 6 30 Yes
51 Port Orford cedar Good 5 6 30 Yes
52 aspen, quaking Good 6 8 40 Yes
53 Port Orford cedar Good 4 6 20 No
54 aspen, quaking Good 3 6 40 No
55 Port Orford cedar Good 6 6 30 Yes
56 Port Orford cedar Good 4 6 30 No
Critical Root Zones
Critical and Structural Root Zones
The diameter of the surveyed trees was used to determine the potential Critical Root Zone (CRZ) of each
tree. The CRZ is the area around the trunk where the roots essential to tree health and stability are
located. It is equal to one and a half (1.5) feet for every inch of trunk diameter measured at 4.5 feet from
grade. For example; tree #1, with a DBH of 2 inches had a calculated CRZ of 3 feet. This distance may
extend beyond the tree canopy dripline.
Critical root zones have been calculated f or all the trees inventoried (Table 4) to help managers
understand where CRZs intersect with necessary limits of disturbance due to site construction. The CRZs
of four (4) trees have substantial construction activities within the CRZ, and are not suitable to ret ain.
Where trees are located close together, many critical root zones will overlap, so tree protection fencing
may enclose an entire row of trees, rather than individuals. Tree protection fencing should be installed
before any construction activities begin and remain in place throughout the period of construction. The
fencing should bear signage specifying the tree protection zone is not to be entered, and should include
the contact information of the project arborist who may be contacted in the event any c oncerns arise
about the trees during the course of the project.
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September 2017 (Revised 8-14-2020)
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Table 4. Critical Root Zones of All Trees
Tree # Common Name
Condition
Rating
DBH
(inches)
CRZ
Radius
(Ft)
Total CRZ
Area (SqFt)
Significant
tree in
Renton Action
1 Cottonwood, black Fair 3 3 28 No
2 willow, Scouler's Good 1 2 7 No
3 Cascara buckthorn Good 1 2 7 No Remove
4 maple, vine Good 18 27 2,290 Yes Remove
4.5 cottonwood, black fair 12 12 1,018 Yes Remove
5 willow, Scouler's Fair 1 2 7 No
6 cottonwood, black Good 2 3 28 No
7 willow, Scouler's Fair 2 3 28 No
8 cottonwood, black Good 13 20 1,195 Yes
9 willow, Scouler's Poor 4 6 113 No Remove
10 willow, Scouler's Poor 5 8 177 No
11 willow, Scouler's Poor 21 31 3,114 Yes
12 cottonwood, black Good 7 11 346 No
13 willow, Scouler's Fair 3 5 64 No
14 cottonwood, black Good 10 15 707 Yes Remove
15 cottonwood, black Good 10 15 707 Yes
16 cottonwood, black Good 10 15 707 Yes
17 cottonwood, black Good 7 11 346 No
18 cottonwood, black Good 14 21 1,385 Yes
19 aspen, quaking Good 12 18 1,018 Yes Crown Raise
20 aspen, quaking Good 12 18 1,018 Yes Crown Raise
21 aspen, quaking Good 12 18 1,018 Yes Crown Raise
22 aspen, quaking Good 12 18 1,018 Yes Crown Raise
23 aspen, quaking Good 12 18 1,018 Yes Crown Raise
24 aspen, quaking Good 12 18 1,018 Yes Crown Raise
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Tree # Common Name
Condition
Rating
DBH
(inches)
CRZ
Radius
(Ft)
Total CRZ
Area (SqFt)
Significant
tree in
Renton Action
25 aspen, quaking Good 12 18 1,018 Yes Crown Raise
26 aspen, quaking Good 12 18 1,018 Yes Crown Raise
27 aspen, quaking Good 12 18 1,018 Yes Crown Raise
28 aspen, quaking Good 12 18 1,018 Yes Crown Raise
29 aspen, quaking Good 12 18 1,018 Yes Crown Raise
30 aspen, quaking Good 12 18 1,018 Yes Crown Raise
31 aspen, quaking Good 12 18 1,018 Yes Crown Raise
32 aspen, quaking Good 16 24 1,810 Yes Crown Raise
33 Port Orford cedar Fair 6 9 254 No Crown Raise
34 aspen, quaking Good 6 9 254 No Crown Raise
35 aspen, quaking Dead 3 5 64 No
36 aspen, quaking Good 3 5 64 No Crown Raise
37 aspen, quaking Good 6 9 254 Yes Crown Raise
38 Port Orford cedar Good 6 9 254 Yes Crown Raise
39 aspen, quaking Good 8 12 452 Yes Crown Raise
40 Port Orford cedar Good 8 12 452 Yes Crown Raise
41 Port Orford cedar Good 8 12 452 Yes Crown Raise
42 aspen, quaking Good 6 9 254 Yes Crown Raise
43 aspen, quaking Good 6 9 254 Yes Crown Raise
44 Port Orford cedar Good 4 6 113 No Crown Raise
45 Port Orford cedar Good 4 6 113 No Crown Raise
46 aspen, quaking Good 6 9 254 Yes Crown Raise
47 Port Orford cedar Good 6 9 254 Yes Crown Raise
48 Port Orford cedar Good 6 9 254 Yes Crown Raise
49 aspen, quaking Good 6 9 254 Yes Crown Raise
50 Port Orford cedar Good 7 11 346 Yes Crown Raise
51 Port Orford cedar Good 5 8 177 Yes Crown Raise
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Tree # Common Name
Condition
Rating
DBH
(inches)
CRZ
Radius
(Ft)
Total CRZ
Area (SqFt)
Significant
tree in
Renton Action
52 aspen, quaking Good 6 9 254 Yes Crown Raise
53 Port Orford cedar Good 4 6 113 No Crown Raise
54 aspen, quaking Good 3 5 64 No Crown Raise
55 Port Orford cedar Good 6 9 254 Yes Crown Raise
56 Port Orford cedar Good 4 6 113 No Crown Raise
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Conclusion
The inspection of fifty-seven (57) trees found locally adapted species in primarily good condition. These
trees are young to established, based on DBH. Due to their locations, fifty-one (51) have good potential
to survive some construction impacts. Tree protection fencing for the critical root zones is recommended,
and required by City of Renton regulations. With these measures in place, it is reasonable to assume the
protected trees can be retained on the site.
Thirty-seven (37) trees have been identified for crown-raise pruning. This pruning should occur before
construction activities to facilitate site access and activities and minimize mechanical damage to trees.
After pruning is conducted, tree protection fencing should be installed.
Five (5) trees have been identified for removal, including three (3) trees considered significant in Renton.
These trees should be removed before tree protection fencing is installed and before construction
activities begin.
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September 2017 (Revised 8-14-2020)
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Appendix A - All Inventoried Trees
Tree # Common Name
Condition
Rating DBH (In.)
Canopy
Width (Ft.)
Height
(Ft.)
Significant
Tree in
Renton Action
1 Cottonwood, black Good 2 10 14 No
2 willow, Scouler's Good 1 5 14 No
3 cascara buckthorn Good 1 5 10 No Remove
4 maple, vine Good 8 14 60 Yes
Remove,
(10+multistem)
4.5 cottonwood, black fair 12 12 40 Yes Remove
5 willow, Scouler's Fair 1 5 14 No
6 cottonwood, black Good 2 5 16 No
7 willow, Scouler's Fair 2 10 20 No
8 cottonwood, black Good 13 14 70 Yes
9 willow, Scouler's Poor 4 8 30 No Remove
10 willow, Scouler's Poor 5 8 30 No
11 willow, Scouler's Poor 21 28 30 Yes
12 cottonwood, black Good 7 14 60 No
13 willow, Scouler's Fair 3 6 20 No
14 cottonwood, black Good 10 12 60 Yes
15 cottonwood, black Good 10 14 60 Yes
16 cottonwood, black Good 10 12 60 Yes
17 cottonwood, black Good 7 12 60 No
18 cottonwood, black Good 14 14 60 Yes
19 aspen, quaking Good 12 6 55 Yes Crown Raise
20 aspen, quaking Good 12 8 55 Yes Crown Raise
21 aspen, quaking Good 12 10 60 Yes Crown Raise
22 aspen, quaking Good 12 7 60 Yes Crown Raise
23 aspen, quaking Good 12 6 60 Yes Crown Raise
24 aspen, quaking Good 12 8 60 Yes Crown Raise
25 aspen, quaking Good 12 8 60 Yes Crown Raise
26 aspen, quaking Good 12 8 60 Yes Crown Raise
27 aspen, quaking Good 12 12 60 Yes Crown Raise
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Tree # Common Name
Condition
Rating DBH (In.)
Canopy
Width (Ft.)
Height
(Ft.)
Significant
Tree in
Renton Action
28 aspen, quaking Good 12 8 60 Yes Crown Raise
29 aspen, quaking Good 12 9 60 Yes Crown Raise
30 aspen, quaking Good 12 8 60 Yes Crown Raise
31 aspen, quaking Good 12 8 60 Yes Crown Raise
32 aspen, quaking Good 16 10 60 Yes Crown Raise
33 Port Orford cedar Fair 6 0 60 Yes Crown Raise
34 aspen, quaking Good 6 6 50 Yes Crown Raise
35 aspen, quaking Dead 3 0 No
36 aspen, quaking Good 3 10 20 No Crown Raise
37 aspen, quaking Good 6 6 20 Yes Crown Raise
38 Port Orford cedar Good 6 8 20 Yes Crown Raise
39 aspen, quaking Good 8 0 20 Yes Crown Raise
40 Port Orford cedar Good 8 6 30 Yes Crown Raise
41 Port Orford cedar Good 8 6 30 Yes Crown Raise
42 aspen, quaking Good 6 8 30 Yes Crown Raise
43 aspen, quaking Good 6 6 40 Yes Crown Raise
44 Port Orford cedar Good 4 6 30 No Crown Raise
45 Port Orford cedar Good 4 8 30 No Crown Raise
46 aspen, quaking Good 6 8 40 Yes Crown Raise
47 Port Orford cedar Good 6 6 40 Yes Crown Raise
48 Port Orford cedar Good 6 8 30 Yes Crown Raise
49 aspen, quaking Good 6 10 30 Yes Crown Raise
50 Port Orford cedar Good 7 6 30 Yes Crown Raise
51 Port Orford cedar Good 5 6 30 Yes Crown Raise
52 aspen, quaking Good 6 8 40 Yes Crown Raise
53 Port Orford cedar Good 4 6 20 No Crown Raise
54 aspen, quaking Good 3 6 40 No Crown Raise
55 Port Orford cedar Good 6 6 30 Yes Crown Raise
56 Port Orford cedar Good 4 6 30 No Crown Raise
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September 2017 (Revised 8-14-2020)
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Appendix B – Tree Retention Worksheet
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