HomeMy WebLinkAboutTR_Arborist Report_2020_06_02_v1.pdf
11415 NE 128th St., Suite 110, Kirkland, WA 98034 | Phone: 425.820.3420 | Fax: 425.820.3437
americanforestmanagement.com
3102 Park Ave N
Renton, WA
Arborist Report
May 28th, 2020
May 28th 2020 3102 Park Ave N - Renton
Page 1
AMERICAN FOREST MANAGEMENT, INC.
Table of Contents
1. Introduction………………………………………………………………….........…….2
2. Description .................................................................................................................................... 2
3. Methodology ................................................................................................................................ 3
4. Observations ................................................................................................................................ 4
5. Discussion ....................................................................................................................................... 5
6. Tree Retention .............................................................................................................................. 6
7. Tree Replacement ........................................................................................................................ 6
8. Tree Protection Measures ……………………………………………………………..6
9. Recommendations…………………...………………………………………………....7
Appendix
Site/Tree Photos – pages 9 - 13
Tree Summary Table - attached
Tree Retention Map - attached
May 28th 2020 3102 Park Ave N - Renton
Page 2
AMERICAN FOREST MANAGEMENT, INC.
1. Introduction
American Forest Management was contacted by Wei Yang of Highland Advisory LLC and
asked to compile an arborist report for a development at 3102 Park Ave N in the City of
Renton. The parcel number is #334210-3215.
Our assignment is to prepare a written report on the current condition of significant trees on
the subject 1.32 acre (57,614 sq. ft.) parcel and any right-of-way or neighboring trees that
may be impacted by future development of the property.
Date of Field Examination: ................................................................... May 21st and 26th, 2020
2. Description
Per Renton Municipal Code 4-11-200, a 'Tree' is defined as: A woody perennial usually
having one dominant trunk, or, for certain species, a multi-stemmed trunk system, with a
potential minimum height of ten feet (10') at maturity. Any trees listed on the Complete King
County Weed List shall not qualify as a tree.
Per RMC 4-4-130, a significant tree has a caliper (trunk diameter measured 4-1/2 feet
above the ground) of at least 6 inches, or an alder or cottonwood tree with a caliper of at
least 8 inches. Trees planted within the most recent ten years qualify as significant trees,
regardless of the caliper. Landmark trees are defined as those with a caliper greater than
30 inches. A total of 90 significant, and 8 landmark trees were identified on the property,
57 of which are listed as 'Weeds of Concern' on the 2019 King County Noxious Weed List
defined as 'Plant species that are not listed as noxious weeds under state law and property
owners are not required to control them. However, the King County Weed Board recognizes
these non-native plants as invasive, recommends control or containment of existing
populations, and discourages new plantings'
No neighboring trees are likely to be impacted by the proposed development, and no
critical areas or buffers are found on the subject parcel.
All subject trees are identified in the field by a numbered aluminum tag attached to their
lower trunk. Field tree tag numbers correspond with the attached Tree Condition Summary
Table which provides descriptive data for all assessed trees, including drip-line
measurements. A copy of the site survey was used as a base layer for the Tree Retention
Map which plots each significant tree, their dripline measurements, and Limits of Disturbance
(LOD).
3. Methodology
Each tree in this report was visited. Tree calipers were measured by tape, and each tree
was visually examined for defects and vigor. Caliper values for multi-stem trees were
calculated using the trunk formula method. (The square root of the sum of each stem
May 28th 2020 3102 Park Ave N - Renton
Page 3
AMERICAN FOREST MANAGEMENT, INC.
squared). Tree heights were measured using a digital hypsometer. The tree assessment
procedure involves the examination of many factors:
• The crown of the tree is examined for current vigor. This is comprised of inspecting
the crown (foliage, buds and branches) for color, density, form, and annual shoot
growth, limb dieback and disease. The percentage of live crown is estimated for
coniferous species only and scored appropriately.
• The bole or main stem of the tree is inspected for decay, which includes cavities,
wounds, fruiting bodies of decay (conks or mushrooms), seams, insects, bleeding,
callus development, broken or dead tops, structural defects and unnatural leans.
Structural defects include crooks, forks with V-shaped crotches, multiple
attachments, and excessive sweep.
• The root collar and roots are inspected for the presence of decay, insects and/or
damage, as well as if they have been injured, undermined or exposed, or original
grade has been altered.
Based on these factors a determination of condition is made. The four condition categories
are described below based on the species traits assessed:
Good – free of significant structural defects, no disease concerns, minor pest issues, no
significant root issues, good structure/form with uniform crown or canopy, foliage of normal
color and density, average or normal vigor, will be wind firm if isolated or left as part of a
grouping or grove of trees, suitable for its location
Fair – minor structural defects not expected to contribute to a failure in near future, no
disease concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced
crown or canopy, average or normal vigor, foliage of normal color, moderate foliage
density, will be wind firm if left as part of a grouping or grove of trees, cannot be isolated,
suitable for its location
Poor – major structural defects expected to fail in near future, disease or significant pest
concerns, decline due to old age, significant root issues, asymmetric or unbalanced crown or
canopy, sparse or abnormally small foliage, poor vigor, not suitable for its location
A ‘viable’ tree is a significant tree that a qualified professional has determined to be in
good health, with a low risk of failure due to structural defects, is wind firm if isolated or
remains as part of a grove, and is a species that is suitable for its location. Trees considered
‘non-viable’ are trees that are in poor condition due to disease, age related decline, have
significant decay issues and/or cumulative structural defects, which exacerbate failure
potential.
4. Observations
General species characteristics are described below. For information on specific trees, see
the attached tree table.
English holly (Ilex aquifolium)
May 28th 2020 3102 Park Ave N - Renton
Page 4
AMERICAN FOREST MANAGEMENT, INC.
English holly is the most common species on the property (46 trees). Most have been planted
in rows oriented east-west to the south of the existing residence, and north-south along Park
Ave. N. The majority have multiple co-dominant trunks as a result of having been cut at 3-4
feet above grade in the past and have since grown to an average height of approximately
30 feet. In King County, English holly is classified as a Weed of Concern and its control is
recommended in natural areas that are being restored to native vegetation and in
protected forest lands.
Coast redwood (Sequoia sempervirens)
Eight significant coast redwood are located on the parcel, four of which are designated
'Landmark' trees with calipers over 30 inches. All but one (#87) are in good condition with
strong taper and root flares. Landmark tree #57 is the only coast redwood found outside of
the grove in the south east corner of the property.
Black locust (Robinia pseudoacacia)
There are eight significant black locust trees located throughout the property, and several
more that are below the six inch caliper threshold which have self-sown. The most common
concerns were structural issues such as forked tops, crooked trunks or asymmetrical crowns.
Overall, most of the black locust trees are in good condition and are viable, the largest of
which is #54 a 'Landmark' tree with a caliper of 33 inches. In King County, black locust is
classified as a Weed of Concern and its control is recommended in natural areas that are
being restored to native vegetation and in protected forest lands.
Yellow cedar (Cupressus nootkatensis)
Six mature yellow cedar trees are found on the property, the largest of which (#19) has a
calculated multi-stem caliper of 47 inches which designates it as a 'Landmark' tree. All of
the yellow cedar are healthy and viable. Most have good trunk taper and strong root flare.
The most common defects observed were poor attachments between co-dominant trunks,
some dead branches, and thin lower crowns.
Green ash (Fraxinus pennsylvanica)
Six green ash trees were found the south east portion of the property. Most have forked
tops and two have severe leans to the south. Most of these are in poor to fair condition.
Pacific dogwood (Cornus nuttallii)
There are five pacific dogwood trees in two groupings on the south side of the lot. They are
variable in size and condition. The largest of which (#74) has a caliper of 18.6 inches and is
in poor condition with a thin canopy and stem dieback. This tree is nearly covered in ivy.
Other significant tree species present in smaller numbers include big leaf maple (Acer
macrophyllum), horse chestnut (Aesculus hippocastanum), shore pine (Pinus contorta),
flowering cherry (Prunus sp.), Portugal laurel (Prunus lusitanica), saucer magnolia (Magnolia
soulangeana), golden arborvitae (Thuja occidentalis), English laurel (Prunus laurocerasus),
Pacific madrone (Arbutus menziesii), and European mountain ash (Sorbus aucuparia).
Notable 'Landmark' trees of these species include #24, a multi-stem big leaf maple with a
calculated caliper of 38.3 inches and an overall height of 64 feet. This tree is in fair
condition with eight primary stems joined low.
May 28th 2020 3102 Park Ave N - Renton
Page 5
AMERICAN FOREST MANAGEMENT, INC.
Tree #64 is a 'Landmark' Pacific madrone with a single trunk caliper of 55.7 inches, which is
the largest caliper on the property. This is an exceptionally large specimen of the species.
This tree is healthy but has English ivy at its base and climbing into its canopy. The grade
slopes downward 13 feet to its west to meet the grade of Park Ave. N. Its canopy has been
pruned for overhead utility clearance at 25 feet to the west.
5. Discussion
The extent of drip-lines (farthest reaching branches) for the subject trees can be found on
the tree summary table at the back of this report. The Limits of Disturbance (LOD)
measurements can also be found on the tree summary table. The LOD measurements are
based on species, age, condition, drip-line, prior improvements, proposed impacts and the
anticipated cumulative impacts to the entire root zone. These should be referenced when
determining retention feasibility.
The City of Renton code requires that tree retention priority should be focused on landmark
trees and significant trees that form a continuous canopy. There are eight landmark trees on
the subject property. The City of Renton defines a landmark tree with a trunk greater than
30" at 4.5' above ground. The attached tree table notes which trees qualify as landmark
trees. The invasive tree species such as English holly and English laurel are low priority for
retention. Retention efforts should be focused on the healthy 'Landmark' trees around the
perimeter of the parcel. Coast redwood #57 is the only 'Landmark' tree situated towards
the center of the lot and not included in a grove of continuous canopy cover.
Much of the property has an ivy infestation. English ivy (Hedera helix) is listed as a non-
regulated Class 'C' noxious weed in King County. This classification of weeds impact the
county, but are already widespread. In most cases, property owners in King County are not
required to control these species, but control is recommended where feasible.
Ivy becomes a problem for trees when it climbs into the tree canopy. The leaves of the ivy
cover branches inhibiting the development of tree leaves and thereby reducing the tree's
photosynthetic processes, causing stress and ultimately decline. The weight of the ivy is also
problematic. Oftentimes, the weight of the ivy will cause stems or branches to fail when they
become over-loaded and cannot support the additional weight. If left untreated, the ivy will
eventually over take the subject trees, causing premature failure.
Ivy will need to be cut away from any trees to be retained. To clear ivy, the vines are cut
back a few feet from the base of the tree and a few feet up the tree trunk, removing the
cut portions. Once the ivy is disconnected from the ground, it will die. The ivy will eventually
decay and fall out of the trees. Given the current infestation, this will take a few years. As
much ivy as possible should be pulled out of the trees to remove additional weight, thereby
increasing structural stability.
English holly, English laurel, European mountain ash, and black locust are listed as weeds of
concern in King County.
May 28th 2020 3102 Park Ave N - Renton
Page 6
AMERICAN FOREST MANAGEMENT, INC.
6. Tree Retention
A total of 98 significant trees were identified on the subject property, six of which are in poor
condition and considered 'Non-viable'. The City of Renton requires retention of 30% of all the
viable significant trees on R-6 zoned sites. The six trees in poor condition were not included the
calculation.
Tree Calculation based on 92 healthy, viable trees
Minimum number of trees that must be retained on site: 28 trees.
RMC 4 -4 -130
c. Tree Removal in Excess of Maximum Allowance: A Routine Vegetation
Management Permit shall be required for tree cutting in greater amounts than
specified under subsection C9 of this Section, Minor Tree Removal Activities, where
tree cutting is proposed without an associated Land Development Permit. Any tree
cutting activities shall be the minimum necessary to accomplish the intended purpose,
and shall be consistent with subsection D3 of this Section, Restrictions for Critical
Areas – General. Trees removed in excess of the maximum amount allowed under
subsection C9 of this Section, Minor Tree Removal Activities, shall be subject to
RMC 4 -4 -130 H1e, Replacement Requirements, unless determined by the
Administrator to be unfeasible in the specific case.
d. Removal of Landmark Tree: A Land Development Permit or Routine Vegetation
Management Permit, which explicitly approves the removal of a landmark tree, as
defined by RMC 4 -11-200, Definitions T, from any property. Replacement trees are
required if the minimum tree density for the subject property is not maintained upon
removal of the t ree.
7. Tree Replacement
Once the final site layout is determined, tree retention and replacement can be calculated.
For planting and maintenance specifications, refer to Section 4-4-130 of the Renton Tree
Ordinances.
8. Tree Protection Measures
The following guidelines are recommended to ensure that the designated space set aside
for the preserved trees are protected and construction impacts are kept to a minimum. Refer
to the City of Renton Code 4-4-130- 9. Protection Measures During Construction for more
information. They are also included at the end of this report.
• Tree protection barriers shall be initially erected at 5’ outside of the drip-line prior
to moving any heavy equipment on site.
• Tree protection fencing shall only be moved where necessary to install
improvements, but only as close as the Limits of Disturbance, as indicated on the
attached plan.
May 28th 2020 3102 Park Ave N - Renton
Page 7
AMERICAN FOREST MANAGEMENT, INC.
• Excavation limits should be laid out in paint on the ground to avoid over
excavating.
• Excavations within the drip-lines shall be monitored by a qualified tree
professional so necessary precautions can be taken to decrease impacts to tree
parts. A qualified tree professional shall monitor excavations when work is
required and allowed up to the “Limits of Disturbance”.
• To establish sub grade for foundations, curbs and pavement sections near the
trees, soil should be removed parallel to the roots and not at 90 degree angles to
avoid breaking and tearing roots that lead back to the trunk within the drip-line.
Any roots damaged during these excavations should be exposed to sound tissue
and cut cleanly with a saw. Cutting tools should be sterilized with alcohol.
• Areas excavated within the drip-line of retained trees should be thoroughly
irrigated weekly during dry periods.
• Preparations for final landscaping shall be accomplished by hand within the drip-
lines of retained trees. Plantings within the drip lines shall be limited. Large
equipment shall be kept outside of the tree protection zones.
9. Recommendations
1. Remove the fewest number of trees necessary to accomplish the intended
development purpose. 'Landmark' trees are the highest priority for retention, trees
listed as Weeds of Concern are the lowest priority for retention.
2. Adhere to all tree protection measures outlined above and in RMC 4-4-130-9
during all phases of development to keep retained trees in a viable condition.
3. Consider removal of invasive species.
There is no warranty suggested for any of the trees subject to this report. Weather, latent tree
conditions, and future man-caused activities could cause physiologic changes and deteriorating
tree condition. Over time, deteriorating tree conditions may appear and there may be
conditions, which are not now visible which, could cause tree failure. This report or the verbal
comments made at the site in no way warrant the structural stability or long term condition of
any tree, but represent my opinion based on the observations made.
Nearly all trees in any condition standing within reach of improvements or human use areas
represent hazards that could lead to damage or injury.
Please call if you have any questions or if we can be of further assistance.
Sincerely,
Benjamin Mark
ISA Certified Arborist #PN-6976A
ISA Tree Risk Assessment Qualified
May 28th 2020 3102 Park Ave N - Renton
Page 8
AMERICAN FOREST MANAGEMENT, INC.
City of Renton Code 4 -4 -130- 9. Protection Measures During Construction
9. Protection Measures During Construction: Protection measures in this subsection shall apply for all trees that are to
be retained on site and off site. Off -site trees containing drip lines that encroach onto the site under construction
shall be consider ed protected trees unless it is determined the abutting property owner is in compliance with
subsection C of this Section, Allowed Tree Removal Activities. All of the following tree protection measures shall
apply:
a. Construction Storage Prohibited: The a pplicant may not fill, excavate, stack or store any equipment, dispose of any
materials, supplies or fluids, operate any equipment, install impervious surfaces, or compact the earth in any way
within the area defined by the drip line of any tree to be reta ined.
b. Fenced Protection Area Required: Prior to development activities, the applicant shall erect and maintain six -foot
(6') high chain link temporary construction fencing around the drip lines of all retained trees or at a distance
surrounding the tree equal to one and one -quarter feet (1 -1/4') for every one inch (1") of trunk caliper, whichever
is greater, or along the perimeter of a tree protection tract. Placards shall be placed on fencing every fifty feet
(50') indicating the words, “NO TRESPASSING – Protected Trees,” or on each side of the fencing if less than fifty
feet (50'). Site access to individually protected trees or groups of trees shall be fenced and signed. Individual trees
shall be fenced on four (4) sides. In addition, the applicant shal l provide supervision whenever equipment or trucks
are moving near trees.
c. Protection from Grade Changes: If the grade level adjoining to a tree to be retained is to be raised, the applicant
shall construct a dry rock wall or rock well around the tree. T he diameter of this wall or well must be equal to the
tree’s drip line.
d. Impervious Surfaces Prohibited within the Drip Line: The applicant may not install impervious surface material within
the area defined by the drip line of any tree to be retained, u nless otherwise approved by the City. (Ord. 5958, 12 -
9 -2019)
e. Restrictions on Grading within the Drip Lines of Retained Trees: The grade level around any tree to be retained may
not be lowered within the greater of the following areas: (i) the area defin ed by the drip line of the tree, or (ii) an
area around the tree equal to one and one -half feet (1 -1/2') in diameter for each one inch (1") of tree caliper. A
larger tree protection zone based on tree size, species, soil, or other conditions may be require d. (Ord. 5676, 12 -
3 -2012)
f. Mulch Layer Required: All areas within the required fencing shall be covered completely and evenly with a minimum
of three inches (3") of bark mulch prior to installation of the protective fencing. Exceptions may be approved if the
mulch will adversely affect protected ground cover plants. (Ord. 5676, 12 -3 -2012)
g. Monitoring Required during Construction: The applicant shall retain a certified arborist or licensed landscape
architect to ensure trees are protected from developmen t activities and/or to prune branches and roots, fertilize,
and water as appropriate for any trees and ground cover that are to be retained.
h. Alternative Protection: Alternative safeguards may be used if determined to provide equal or greater tree
protection. (Ord. 5676, 12 -3 -2012; Ord. 5841, 6 -12-2017)
10. Maintenance:
a. All retained and replacement trees, including protected trees, shall be maintained in perpetuity from the date
of the final Land Development Permit issued for the project, unless tree removal is authorized pursuant to this
Section;
b. All retained trees and vegetation shall be pruned and trimmed to maintain a healthy growing condition or to
prevent l imb failure;
c. With the exception of dangerous trees specifically retained to provide wildlife habitat, any protected tree that
becomes a dangerous tree, as defined in RMC 4 -11-200, or any protected or replacement tree that is stolen, shall be
replaced within three (3) months or during the next planting season if the loss does not occur in a planting season