HomeMy WebLinkAboutArborist Report
Protected Tree Report:
Tree Survey, Encroachment,
Protection and Mitigation
418 Fairview Avenue
Arcadia, CA 91007
Prepared For: Mr. Tom Li
Prestige Design, Planning and Development, Inc.
P.O. Box 660866
Arcadia CA 91006
Tel: (626) 538-7373
Email: Prestige.DPD.Inc@gmail.com
Prepared By: Michael Crane
Arbor Care, Inc.
1660 E. Mountain St.
Pasadena, CA 91104
Tel: (626) 737-4007
Email: info@arborcareinc.net
June 2019
Table of Contents
Summary of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Background and Purpose of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Project Location, Description & Tree Ordinance . . . . . . . . . . . . . . . . . . . . . . . . 2
Tree Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Tree Characteristics & Health Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Construction Impact Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Design Analysis of Protected Tree Encroachments . . . . . . . . . . . . . . . . . . . . . . . 7
Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Appendix A - Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Appendix B – Soil and Root Protection Materials . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix C – Trunk Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Appendix D - Protected Tree Construction Impact Guidelines . . . . . . . . . . . . . . 15
Author’s Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Certification of Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Site Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pocket at back
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
1
SUMMARY OF DATA
BACKGROUND & PURPOSE
I was retained by the Project Designer and Manager, Mr. Tom Li, of Prestige Design, Planning
and Development Inc. to be the consulting arborist for the planned redevelopment of the property
located at 418 Fairview Ave., Arcadia. There are Protected Trees located on the property, and
encroaching over the property from off-site. The proposed construction may impact these trees
and this report will serve to both notify the City of Arcadia Planning Division of the extent of the
potential impacts as well as to inform the builder of the proper protection measures which must
be taken in order to preserve them. As part of my preparation for this report I made a site visit to
the property on June 20, 2018. I met with Mr. Li at that time to view and discuss the proposed
construction plans as they relate to the preservation of the Protected Trees. I was given a full
scale Site Plan, with the footprints of proposed structures and other significant infrastructure
plotted on it for my analysis.
Total number of healthy Protected Trees on property including street trees
located in the immediate public right-of-way area . . . . . . . . . . . . . . . . . . . . . . . . 5
Total number of off-site Protected Trees
with canopies (driplines) encroaching onto the property . . . . . . . . . . . . . . . . . . . . 2
Total number of diseased/hazardous Protected Trees on site
proposed for removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
Total number of healthy Protected Trees to be preserved . . . . . . . . . . . . . . . . . . . 5
Total number of healthy Protected Trees to be removed . . . . . . . . . . . . . . . . . . . 2
Total number of Protected Trees that will be preserved, which will
be impacted by construction within dripline (encroached) . . . . . . . . . . . . . . . . . . 4
Total number of Protected Trees with no dripline encroachments . . . . . . . . . . . 1
Total number of proposed mitigation trees to be planted on site . . . . . . . . . . . . . . 0
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
2
PROJECT DESCRIPTION & TREE ORDINANCE
This aerial view (courtesy of Apple Maps) has been illustrated to show the
approximate boundary lines (orange). The locations of the Protected Trees are
numbered in yellow.
The property consists of a one story single-family residence that appears to be in poor condition.
The home will be demolished and the property redeveloped into a six-unit condominium complex.
The landscape is minimally maintained and the Protected Trees are in generally good
condition. The landscape will be redesigned and several of the Protected Trees will be
accommodated into the new landscape.
2
N
3
4
1
6
5
7
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
3
City of Arcadia Tree Ordinance
Oaks, Sycamore, and many other tree species are Protected under the various tree
ordinances. Here is a summary of the tree protection laws.
On January 21, 1992 the City Council adopted Ordinance No. 1962 recognizing oak trees as significant aesthetic
and ecological resources and establishing criteria for the preservation of oak trees. The regulations (Chapter 7 of
the Arcadia Municipal Code) provide that the following oak trees shall not be removed, relocated, damaged, or
have their protected zones encroached upon unless an Oak Tree Permit is granted:
• Engelmann Oaks (Quercus engelmannii) or Coast Live Oak, California Live Oak (Quercus agrifolia)
which have a trunk diameter larger than four (4) inches measured at a point four and one half (4 ½) feet
above the crown root, or, two (2) or more trunks measuring three (3) inches each or greater in diameter,
measured at a point four and one half (4 ½) feet above the crown root.
• Any other living oak tree with a trunk diameter larger than twelve (12) inches measured at a point four
and one half (4 ½) feet above the crown root, or, two (2) or more trunks measuring ten (10) inches each
or greater in diameter measured at a point four and one half (4 ½) feet above the crown root.
On March 3, 2015, the City Council adopted Ordinance No. 2323 amending the code to add Sycamore trees to the
list of City's Tree Preservation Regulations. The protected trees are Oak and Sycamore trees. Protected Sycamore
trees are defined as:
• Plantanus racemosa (Sycamore) with a trunk diameter larger than six (6) inches measured at a point four
and one-half (4½) feet above the root crown, or two (2) or more trunks measuring four (4) inches each or
greater in diameter, measured at a point four and one-half (4½) feet above the root crown.
On August 2, 2016, The City Council adopted Ordinance No. 2338 to add additional protected trees and unprotected
trees to the City’s tree preservation regulations. In September, the City began protecting mature trees that are located
within a required front, side, street-side, or rear yard setback area that are either larger than 12 inches in diameter or
two or more trunks larger than 10 inches in diameter if there are multiple trunks.
Below is a list of the unprotected trees:
1. Fruit trees
2. Fraxinus uhdei (Shamel Ash)
3. Ficuses – Exception: Ficus macrophylla (Moreton Bay Fig)
4. Eucalyptus
5. Ailanthus altissima (Tree of Heaven)
6. Arecaceae (Palm Tree)
7. Schinus terebinthifolius (Brazilian Pepper)
8. Ceratonia siliqua (Carob)
9. Betula pendula (European White Birch)
10. Grevillea robusta (Silk Oak)
11. Morus (Mulberry)
12. Acer saccharinum (Silver Maple)
13. Cupressus sempervirens (Italian cypress)
14. Populus Fremontii (Western Cottonwood)
15. Alnus rhombifolia (White Alder)
16. Populus trichocarpa (Black Cottonwood)
17. Populus ‘Highland’ hybrid
18. Salix lasiolepis (Arroyo Willow)
19. Liquidambars (Sweet Gum)
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
4
TREE SURVEY
This table lists all trees with trunk diameters measuring four inches or greater and heights of 15 feet or greater located on the
property, as well as all off-site Protected Tree Species with trunk diameters measuring four inches or greater encroaching onto the
property. Off-site trees are indicated with an “os” next to their tree numbers. Multi-trunked specimens are indicated next to the
trunk diameter with an “m” and the diameters of the two largest trunks are listed. A determination is then provided for the protected
status of each tree based on criteria of species, size and location. All street trees or trees in public areas are Protected regardless of
species or size. Protected Trees that are not oaks or sycamores have limited protection located in the buildable areas of the property.
Tree numbers correspond to the tree locations plotted on the site plan included in this report and to all references to each tree in this
report. Only Protected Trees located on the property have numbered tags affixed to their trunks. All palm trees are excluded, as all
species are non-protected.
Tree Survey for 418 Fairview Ave., Arcadia
Tree Identification Protected Status
Tree
# Botanical Name Common Name Trunk
Diam.
Protected
Species
Minimum
Required
Size
Located in
Protected
Area
PROTECTED
TREE
1 Quercus agrifolia Coast Live Oak 35" Yes Yes Yes Yes
2 Quercus agrifolia Coast Live Oak 24” Yes Yes Yes Yes
3 Cedrus deodara Deodar cedar 42" Yes Yes Yes Yes
4 Pinus pinea Italian Stone Pine 44" Yes Yes Yes Yes
5os Ulmus parvifolia Chinese Elm 12” Yes Yes Yes Yes
6 Cupaniopsis sp. Carrotwood 14” Yes Yes Yes Yes
7os Pyrus kawakamii Japanese Pear 4” Yes No* Yes Yes
8 Ligustrum japonicum Texas Privet 4” Yes No Yes No
9 Fraxinus sp. Ash 35” No Yes No No
10 Podocarpus sp. Yew Pine m 5,4 Yes No Yes No
11 Podocarpus sp. Yew Pine m 4,2 Yes No Yes No
* Tree #7 is a street tree so it is Protected irrelevant of its size.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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This chart includes all Protected Trees that are either located or encroaching on the property. It provides physical data collected from
field observations. The trees have been surveyed and numbers correspond to the Site Plan included in this report. Tree numbers with
an “os” indicate that the specimen is located off-site and a portion of the canopy extends over the subject property. Trunk diameters of
multi-trunked specimens are listed by the size of the largest trunk or leader with the cumulative of all trunks listed in parentheses.
TREE CHARACTERISTICS & HEALTH MATRIX
CHARACTERISTICS HEALTH
SIZE FORM CROWN
CLASS
AGE
CLASS
FOLIAGE
DENSITY
SHOOT
GROWTH
WOUND
DEFENSE
VIGOR
CLASS TREE NUMBER SPECIES TRUNK DIAMETER (INCHES) APPROXIMATE HEIGHT (FEET) AVERAGE SPREAD (FEET) SYMMETRIC ASYMMETRIC DOMINANT CO-DOMINANT SUPPRESED YOUNG MATURE OVERMATURE NORMAL SPARSE DISEASE / INSECT AVERAGE POOR TWIG DIEBACK NORMAL POOR WOOD DECAY GOOD POOR DISEASED/HAZARDOUS 1 Quercus agrifolia 35 45 60 X X X X X X X
2 Quercus agrifolia 24 30 30 X X X X X X X
3 Cedrus deodara 42 50 60 X X X X X X X
4 Pinus pinea 44 45 40 X X X X X X X
5os Ulmus parvifolia 12 30 30 X X X X X X X
6 Cupaniopsis anacardioides 14 20 20 X X X X X X X X
7 Pyrus kawakamii 4 10 10 X X X X X X X
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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This chart includes all Protected Trees that are located on the property and any off-site encroaching on the property. It provides data
collected from the analysis of construction plans. The tree has been surveyed and numbers correspond to the Site Plan included in this
report. Tree numbers with an “os” indicate that the specimen is located off-site and a portion of the canopy extends over the subject
property. For rootzone impacts, the required excavation is considered only for unbuffered areas.
CONSTRUCTION IMPACTS MATRIX
TREE SPECIES SIZE &
CONDITION ROOTZONE IMPACTS REQUIRED PRUNING OF
LIVE CROWN TREE NUMBER Protected Trees:
• 4” or larger Quercus
agrifolia, engelmannii,
and any other species of
Quercus genus larger
than 12”
• Platanus racemosa
• Any tree located in the
public right-of-way
• All other species 12” or
larger that are not on
the exemption list TRUNK DIAMETER (DBH) CONDITION Sides of tree where excavation (six inches or deeper) will occur Sides where excavation impacts are buffered by existing infrastructure Excavation will remain a distance of at least 10 X DBH from trunk Excavation will remain a distance of at least 5 X DBH from trunk Excavation will remain a distance of at least 3 X DBH from the trunk Removal or Relocation Additional light grading less than 6" deep to occur within dripline Estimated % of total root mass to be removed or severed No Pruning Required Pruning not to exceed 10% Pruning not to exceed 30% Number of cuts larger than 3" in diameter required Diameter of cuts for branch removals 1 Quercus agrifolia 35 Good All - - - - - - - -
2 Quercus agrifolia 24 Good E - Yes 50 1 8
3 Cedrus deodara 42 Good All - - - - - - - -
4 Pinus pinea 44 Good S - Yes - 0 -
5os Ulmus parvifolia 12 Good W W Yes - 0 -
6 Cupaniopsis anacardioides 14 Fair - - Yes - 0 -
7os Pyrus kawakamii 4 Good - - No 0 0 N/A
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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DESIGN ANALYSIS OF PROTECTED TREE ENCROACHMENTS
Refer to Site Plan located in pocket at back of this report, and Photos in Appendix A,
page 9.
Analysis regarding rootzone impacts are based on the type of impact, e.g, soil compaction,
grading, and excavation; as well as the distance from the trunk that the impacts will occur. It is
commonly accepted among professional arborists that a distance equal to three times a trunks
diameter contains the structural roots responsible for keeping the tree upright. This critical
rootzone area is defined as the root plate. Beyond the root plate the roots typically taper off into
smaller, less significant sizes. These smaller roots are usually two inches in diameter or smaller
and make up the rootmass responsible for water and nutrient uptake. Although roots of these
sizes can be cut without significantly impacting health and stability it is advised that no more
than 30 percent of the rootmass within the dripline is severed. The bulk of the rootmass is
located within the top three feet of soil and root growth slows or halts when soil bulk density
exceeds 1.60 g/cm3 for most soils.
Tree #1 – 35” Coast Live Oak: Located in the footprint of a proposed garage. It is planned for
removal.
Tree #2 – 24” Coast Live Oak: Located approximately one foot from the west property line in
the side yard area. The foundation of unit #5 will be built six feet from the trunk. Typical
overexcavation of five feet will come as close as one foot from the trunk. An attempt can be
made to reduce the overexcavation by excavating and recompacting to a greater depth in the area
near the tree. The soil engineer must be engaged in this effort. An enclosed patio area connected
to Unit #5 will encroach within five feet and a concrete walkway will be built within one foot of
the trunk. The existing west property line wall will remain. Crown raising and reduction
pruning will be required to accommodate the exterior wall and roofline. On large low branch
will be removed and small cuts will be required in the upper portion of the crown. No more than
30% of the live crown will be removed.
Tree #3 – 42” Deodar Cedar: Located in the footprint of Unit #2. It is planned for removal.
Tree #4 – 44” Italian Stone Pine: Located in the front yard area. The foundation of Unit #1
will be built 17 feet from the trunk on its south side. A reduced overexcavation coordinated and
approved by the soil engineer shall be explored near the tree. An enclosed patio area connected
to Unit #1 will be built as close as nine feet from the trunk in the southwest quadrant of the
dripline. The driveway will be built in the same footprint as the existing one and the paved
surface will come as close as two feet from the trunk on its east side. Typical landscape
renovations will encroach. Some crown reduction pruning will be required to accommodate the
exterior wall and roofline of Unit #1. Small cuts can accomplish the pruning and no more than
10% of the live crown will be removed.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
8
Tree #5– 12” Chinese Elm: Located just off site near the east property line. The trunk is
contained within the property by the boundary line block wall, which was built to contour around
it. The wall will remain. The tree has a leaning form, which extends over the proposed
driveway. The new driveway will be built in the same footprint and the existing east property
line wall will remain. Reduction pruning at the end of the leaning crown will be required to
accommodate the exterior wall and roofline of Unit #1. Small cuts can accomplish the pruning
and no more than 10% of the live crown will be removed.
Tree #6– 14” Carrotwood: Located at the northeast corner of the property. The driveway will
be replaced in the same footprint. Some crown reduction pruning may be required to gain
establish adequate access along the driveway and haul route. Small cuts can accomplish the
pruning and no more than 10% of the live crown will be removed. No deep excavation will
encroach. The existing east property line wall that encroaches the tree will remain.
Tree #7– 4” Japanese Evergreen Pear: Located off site in the public right-of-way setback area
of the property to the west. No encroachments will occur.
FINDINGS
• Two Protected Trees located on site (Trees #1 and #2) are located in the footpints of
proposed condominium units, and are planned for removal.
• Tree #2, a Protected Oak, will be severely encroached by the required excavation for the
construction of the building pad. Reduction of overexcavation shall be pursued. This
must be done in collaboration of the soil engineer, grading contractor and arborist.
• Tree #4, a Protected Pine, will be significantly encroached and overexacavation should be
minimized as much as possible.
• The proximity of construction to the Protected Trees planned for preservation is not
conducive to the typical installation of protective fences to establish adequate Tree
Protection Zones. Soil and root protection material shall be installed where fences cannot
be placed as specified in Appendix B.
• The haul route for the entire project will be the existing driveway. Trees #4; #5 and #6
are located very close to it and are susceptible to mechanical injury. Construction will
occur within a few feet of Tree #2, and it too is susceptible to mechanical injury. The
trees shall be fitted with trunk protection as specified in Appendix C.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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• The limited landscape area of the design will not accommodate any large trees. Small
patio type trees are appropriate for the open space in the proposed design. Mitigation
Trees for the two Protected Trees planned for removal (Trees #1 and #3) will be limited
to small specimens.
RECOMMENDATIONS
As with many construction projects, soil compaction is the most preventable impact that will
need to be monitored in order to provide reliable protection and long-term preservation of the
trees. To prevent unnecessary soil compaction a protective fences and/or soil and root protection
material must be installed around the Protected Trees before any demolition occurs. The goal is
to enclose the largest possible amount of space underneath the tree so that the heavy equipment
required for demolition and construction can be routed away from root zones. The
recommended fence placements are drawn in dashed lines on the Site Plan of this report. The
main haul route for the demolition phase and into most of the construction phase shall be the
existing driveway on the north side of the property.
• Prior to demolition the contractor and consulting arborist shall meet on site to make sure
fences, soil and root protection materials, and trunk protection systems are properly
placed and installed and to review the goals for the tree protection plan. The location of
the Tree Protection Zones are drawn with a dashed line on the Site Plan included in
this report.
• Tree Protection Zone fences shall be at least four feet tall and constructed of chain link
fencing secured on metal posts.
• Examples of soil and root protection materials are provided in Appendix B.
• Trunk protection specifications are provided in Appendix C.
• Maintain the Tree Protection Zones throughout the completion of the project. No staging
of materials or equipment or washing-out is to occur within the protected zones.
• The removal of existing vegetation near the Protected Trees shall be done by hand. No
rototilling or other deep cultivation or grading shall occur within the driplines.
• Refer to the Construction Impact Guidelines in Appendix C for important general
preservation measures concerning the different elements of this project
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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APPENDIX A – Photos
ABOVE: Looking north from the south property line at Trees #1 and #2. Tree #1
will be removed and Tree #2 will be preserved. BELOW: Tree #1
1
1
2
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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ABOVE: Tree #2. The crown is asymmetric, which will reduce the required
pruning to accommodate the exterior wall and roofline of the encroaching unit.
BELOW: Looking south at the front of the property from the street. Trees #3, #4,
#6 and #7 are visible. Trees #4; #6 and #7 will be preserved and Tree #3 will be
removed. The driveway will be replaced in the same footprint; and the existing
driveway area will be the primary haul route throughout the project.
4
2
6 7 3
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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ABOVE: BELOW: Looking south at Tree #5. Reduction pruning will be required to
accommodate the new structure. Trunk protection will be required for this tree located
along the haul route. BELOW: Looking east at Trees #4 and #6. Trunk Protection will
be required for both of these trees as well.
5
6
4
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
13
APPENDIX B - Soil and Root Protection Within the Tree Protection Zone
If traffic cannot be kept outside of the Tree Protection Zone for the entire duration of
construction, actions can be taken to disperse the vehicular load and protect the roots,
minimizing soil compaction and mechanical root damage. These include:
1) Applying 6 to 12 inches of wood chip mulch to the area.
2) Laying ¾-inch thick plywood or 4x4 inch wood beams over a 4+ inch thick layer of
wood chip mulch.
3) Applying 4 to 6 inches of gravel over a taut, staked geotextile fabric.
4) Placing commercial logging or road mats on top of a mulch layer.
Stone, geotextile, and mulch exceeding 4 inches thick will need to be removed from the TPZ
once the threat of soil or root damage has passed.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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APPENDIX C – Trunk Protection Specifications
Taken from ANSI A300 Best Management Practices – Managing Trees During Construction
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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APPENDIX D - Protected Tree Construction Impact Guidelines
Size and Distribution of Tree Roots – Taken from Arboriculture, Integrated Management of
Landscape Trees Shrubs and Vines. Harris, R.W., Clark, J.W., Matheny N.P. Prentice Hall
2004.
Roots of most plants, including large trees, grow primarily in the top meter (3 ft) of soil (see
figure below). Most plants concentrate the majority of their small absorbing roots in the upper
150 mm (6 in.) of soil if the surface is protected by a mulch or forest litter. In the absence of a
protective mulch, exposed bare soil can become so hot near the surface that roots do not grow in
the upper 200 to 250 mm (8 to 10 in.). Under forest and many landscape situations, however,
soil near the surface is most favorable for root growth. In addition, roots tend to grow at about
the same soil depth regardless of the slope of the soil surface.
Although root growth is greatly influenced by soil conditions, individual roots seem to have an
inherent guidance mechanism. Large roots with vigorous tips usually grow horizontally. Similar
roots lateral to the large roots grow at many angles to the vertical, and some grow up into the
surface soil. However, few roots in a root system actually grow down.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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The importance of soil
Soil supports and anchors tree roots and provides water, minerals and oxygen. Furthermore, soil
is a habitat for soil microorganisms that enhance root function. A soil’s ability to sustain tree
growth is largely determined by its texture, structure (bulk density), organic matter, water and
mineral content, salinity, aeration, and soil-microbe abundance and diversity.
Soil physical properties
Soil texture – the relative proportion of sand, silt and clay, is important because it affects water –
and nutrient-holding capacity, drainage and aeration (gaseous diffusion). Soil structure is the
arrangement of individual soil particles into clumps (aggregates). The net result is the
formulation of larger voids between the aggregates which serve as channels for gaseous
diffusion, movement of water and root penetration. Unfortunately, soil aggregates are readily
destroyed by activities that compact the soil (increase bulk density). When this occurs, gaseous
exchange, permeability, drainage and root growth are restricted.
The influence of the organic matter content of soil properties is quiet significant. Its
decomposition by soil organisms releases substances that bind soil particles into larger granules,
which improves both soil aeration, and drainage. In essence, the breakdown of organic matter
improves water – and nutrient-holding capacity and reduces bulk density. Furthermore, it is the
primary source of nitrogen and a major source of nitrogen and a major source of phosphorus and
sulfur. Without organic matter soil organisms could not survive and most biochemical processes
in the soil would cease.
Soil aeration, the movement and the availability of oxygen, is determined by both soil texture
and structure. In general, compacted and finer soils, due to a higher proportion of small pore
spaces (micropores), tend to drain slowly and hold less air than coarser, sandy, or well-structured
find soils. Water retained in the small pores displaces oxygen and inhibits gaseous diffusion.
The availability of soil water is largely determined by the size of the pore spaces between the soil
particles and the larger aggregates in which water is held. Most of the water in the larger pore
spaces drains readily due to gravitational forces. A relatively thin film of water, which is readily
available to plant roots, remains following drainage. Much of water held within the smaller pore
spaces resists uptake by plant roots because it is held tightly on the soil surfaces.
Plant roots require an adequate supply of oxygen for development. Injury or dysfunction results
when oxygen availability drops below a critical level. Root respiration is the first process to be
restricted, followed by disruptions in growth, metabolism, nutrient and water uptake, and
photosynthesis. Furthermore, the accumulation of high levels of carbon dioxide, produced by the
roots during respiration can also impair root function. Reduced soil aeration resulting from soil
compaction, flooding, excess irrigation, or impervious pavement favors the development of
crown rot (Phytophthora root disease). It also inhibits mycorrhizal fungi that enhance water and
nutrient uptake and resist root pathogens.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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The forest floor under a canopy in most undeveloped forests and woodland settings is typically
covered by a layer of fallen leaves and other woody debris. It is usually cool, shady, well-
aerated, and relatively moist – conditions that favor normal root growth. When the natural leaf
litter is removed and when a tree’s lower canopy is pruned up to provide clearance, the absorbing
roots in the upper few inches of the soil experience higher soil temperatures and increased
desiccation due to direct exposure to sunlight.
Minimizing the Effects of Construction and Development on Tree Root Systems
Activities that injure roots or adversely affect the root zone should be avoided or kept as far from
the trunk as possible. Design changes or alternative building practices that avoid or minimize
construction-related impacts should be considered and proposed when applicable.
Soil Compaction
Soils are intentionally compacted under structures, sidewalks, reads, parking areas, and load-
bearing fill to prevent subsidence, and to prevent soil movement on slopes. Although
unintentional, soil within the root zone of trees is often compacted by unrestricted foot traffic,
parking of vehicles, operation of heavy equipment, and during installation of fill. Compaction
destroys the soil’s natural porosity by eliminating much of the air space contained within it. It
leaves the soil hardm impenetrable and largely unfavorable for root growth. The soil’s natural
porosity, which allows for water movement and storage, gaseous exchange, and root penetration,
is greatly reduced. Consequently, root growth and tree health suffer. Soil compaction is best
managed by preventing it.
Bulk density is used to describe a soil’s porosity, or the amount of space between soil particles
and aggregates. High bulk densities indicate a low percentage of total pore space.
Pavement
Paving over the root systems of trees is another serious problem because it reduces the gaseous
diffusion and soil moisture. Most paving materials are relatively impervious to water penetration
and typically divert water away from a tree’s root zone. Cracks and expansion joints do, though,
allow for some water infiltration into the soil below. Of greater concern, is the loss of roots from
excavation to achieve the required grade, and the necessary compaction to prevent subsidence.
Once the soil surface is compacted, a base material is then added and compacted as well. With
that done, the surface can then be paved. Thus, pavement within the root zones of trees can
damage roots and create unfavorable soil conditions. One alternative to minimize pavement
impacts is to consider placing the pavement on the natural grade over a layer of minimally
compacted base material. To reduce sub-grade compaction, consider using reinforced concrete
or asphalt over a goetextile blanket to help stabilize the soil. On-grade patios or paving that
covers more than one-third of the tree protection zone (TPZ) should be constructed using
permeable materials that allow aeration and water penetration. Soil under permeable surfaces
should not be compacted to more than 80 percent.
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Michael Crane, RCA #440. June 2019
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Excavation and root pruning
Excavation within the root zones of trees should be avoided as much as possible. The extent of
root pruning (selective) or cutting (non-selective) should be based on the species growth
characteristics and adaptive traits, environmental conditions, age, health, crown size, density,
live crown ration and structural condition of the tree. The timing of the root pruning or cutting is
another important consideration. Moderate to severe root loss during droughts or particularly hot
periods can cause serious water-deficit injury or death.
When root pruning/ cutting is unavoidable, roots should be pruned or cut as far from the trunk as
possible. Cutting roots on more than one side of a tree should also be avoided. Root cutting
extending more than half-way around a tree should generally be no closer than about 10 times
the trunk diameter. Recommended distances range from as little as 6 times trunk diameter
(DBH) for young trees to 12 times trunk diameter for mature trees. The size of the TPZ should,
however, be increased for over mature and declining trees and species that are sensitive to root
loss.
The minimum distance from the trunk that roots can be cut on one side of the tree without
destabilizing it, is a distance equal to about three times the diameter (DBH) of the trunk. Roots
severed within that distance provide little or no structural support. Root pruning or cutting
distances from the trunk should be greater for trees that lean and/ or those growing on shallow or
wet soil.
In cases where the proposed grading will adversely affect trees designated for retention, special
attention should be given to proper root pruning and post-construction care for injured trees.
Where structural footings are required for foundations, retaining walls, etc., and roots larger than
2 inches in diameter will be impacted, consider design changes or alternative building methods.
When excavation within 5 times trunk diameter is unavoidable, roots greater than 1 ½ inches in
diameter should be located prior to excavation and then pruned to avoid unnecessary damage.
Hand-digging or use of a hydraulic or pneumatic soil excavation tool is the least disruptive way
to locate roots for pruning. Although mechanical root pruners make clean cuts, they are non-
selective. A backhoe bucket, dozer blade or trencher will typically pull, rip or shatter the larger
root, causing additional damage toward the tree. Once the roots that interfere with the structure
being built, e.g., foundations, footings, retaining wall, curbs, etc., are exposed, they should then
be cut perpendicular to their long axis using a hand-saw, ‘carbide-tipped chainsaw’ or sharp ax,
depending on size. Roots that are pruned in this manner typically regenerate new roots from
near the cut. Roots exposed by excavation should be protected from exposure to
sun and desiccation. Exposed roots that can not be covered with soil by the end of the day
should be covered with moistened burlap or similar material.
Roots can generally be cut in a non-selective manner when excavating near of beyond the
dripline. Ripped, splintered or fractured portions of roots however, should be re-cut. The
damaged portion should be removed using sharp tools. The cut should be flat across the root
Protected Tree Report: Survey, Encroachment and Protection Plan
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Michael Crane, RCA #440. June 2019
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with the adjacent bark intact. Wound dressings should not be applied to pruned or damaged
roots except when recommended for disease, insect or sprout control.
The best approach to avoid water-deficit injury following root loss during the growing season is
to provide ample irrigation. Irrigation should be considered prior to, during, and after root
pruning. Watering schedules should also consider local soil conditions, climate, topography,
time of year, species adaptability, extent of root pruning and tree health. If possible, irrigate the
tree 7 to 10 days prior to excavation so that there is an adequate reservoir of soil water. Water
can be delivered to large construction sites via water-tank trucks and applied directly to affected
trees or stored nearby in plastic tanks. On relatively flat terrain, a 6 to 8 inch soil berm at the
tree’s dripline should be constructed to act as a watering basin. On steep terrain, soaker hoses
should be used. They can be placed across the slope or spirally around the trunk, from about six
feet away to the dripline. In addition, a two to four inch layer of wood chip mulch should be
applied to as much of the root zone as possible to retard soil water loss.
Pruning foliage to compensate for root loss is not supported by scientific research and likely to
result in slower recovery. Fertilization to stimulate root growth is generally unwarranted and
may be counterproductive.
Trenching within the Tree Protection Zone
Trenching for underground utilities should be routed around the TPZ. When this is unavoidable,
trenching within the TPZ should be done by ‘hand’ or using a pneumatic or hydraulic soil
excavation tool, carefully working around larger roots. Roots larger than
1 ½ inches in diameter should not be cut. Dig below these roots to route utilities or install
drains. A combination of tools can also produce satisfactory results, for example, a skillful
backhoe operator under the arborist’s supervision can dig down several inches at a time and
detect larger roots by ‘feel’ (resistance). At that point, as assistant can expose the root and dig
around it. In this manner, the backhoe can then continue extending the trench though the TPZ.
Tunneling (boring) through the TPZ is the preferable alternative. For most large trees, tunneling
depth should be at least 36 inches. Tunneling should begin at the edge of the TPZ, but no closer
than a distance equal to one foot of clearance for each inch of tree DBH. Tunnels should also be
offset to either side of the trunk. For trenching that extends only part way into TPZ, consider
trenching radially to the tree trunk, as this is less harmful than tangential trenching. All trenches
made within the TPZ should be backfilled as quickly as possible to prevent root and soil
desiccation.
Managing Root Injured Trees
Root-pruned trees should be monitored for symptoms of water-deficit injury for a specified
period following root pruning. Irrigation should be considered prior to, during, and after root
pruning. Irrigation schedules should consider local soil conditions, climate, topography, time of
year, species tolerance, extent of root pruning and tree health.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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Grade Change: Fill Soil
Fill soil placed within the root zones of trees can have an adverse effect, particularly if the soil is
compacted to support a structure or pavement. Soil compaction reduces aeration and water
infiltration. Fill soil, die to textural changes, can also prevent water from penetrating the original
soil layer below where the roots are. Furthermore, soil placed against the root crown and lower
trunk can lead to root disease problems, especially if the soil near the trunk remains moist during
the summer from irrigation. Alternatives to placing fills over roots zones shall be considered and
proposed as appropriate.
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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AUTHOR’S CREDENTIALS
Protected Tree Report: Survey, Encroachment and Protection Plan
418 Fairview Ave., Arcadia, 91007
Michael Crane, RCA #440. June 2019
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CERTIFICATION OF PERFORMANCE
I, Michael Crane, certify that:
• I have personally inspected the tree(s) and the property referred to in this report and have
stated my findings accurately.
• I have no current or prospective interest in the vegetation or the property that is the
subject of this report and have no personal interest or bias with respect to the parties
involved.
• The analysis, opinions, and conclusions stated herein are my own and are based on
current scientific procedures and facts.
• My analysis, opinions, and conclusions were developed and this report has been prepared
according to commonly accepted arboricultural practices.
• No one provided significant professional assistance to me, except as indicated within the
report.
• My compensation is not contingent upon the reporting of a predetermined conclusion that
favors the cause of the client or any other party not upon the results of the assessment, the
attainment of stipulated results, or the occurrence of any subsequent events.
I further certify that I am a member in good standing of the American Society of
Consulting Arborists and the International Society of Arboriculture. I have been
involved in the field of Horticulture in a full-time capacity for a period of more than 25
years.
Signed: ____________________________
Registered Consulting Arborist #440; American Society of Consulting Arborist
Board Certified Master Arborist #WE 6643B; International Society of Arboriculture
Licensed California Agricultural Pest Control Adviser #AA08269
June 25, 2019
Date: ______________________________