Tree #1
1430 Cambridge Rd
Tree #1 is located adjacent tothe property located at 1430 Cambridge Rd. As this is a corner property, the tree itself is physically located on Monterey Rd. See attached arborist report and images for additional information.
Photos of Coast Live Oak Tree @ 1430 Cambridge Rd. (Tree #7715)
Tree #2
1101 Lorain Rd
Tree #2 is located within the public right-of-way along Lorain Rd, adjacent to the frontage of the property at 1101 Lorain Rd. Please refer to the attached aerial map, site photos, and arborist report for additional details.
Tree #3
2290 Sherwood Rd
Tree #3 is located within the public right-of-way along Sherwood Rd, directly adjacent to the front property line of 2290 Sherwood Rd. Please refer to the attached aerial map, site photos, and arborist report for additional details.
CITY OF SAN MARINO
PARKS & PUBLIC WORKS
DEPARTMENT
SONIC TOMOGRAPHY REPORT
City-Owned Trees Previously
Presented to City Council
(Trees #1-3)
Date: July 23, 2026
Prepared by: Peter C. Harnisch -
Consulting Arborist
pg. 1
Peter C. Harnisch Consulting Arborist
(626) 945 3176 Registered Consulting Arborist #595
1022 Santa Ana St. ISA Tree Risk Assessment Qualified
Laguna Beach, CA 92651 ASCA Tree and Plant Appraisal Qualification [email protected] ISA Board Certified Master Arborist WE-0773B Amber Shah, P.E.
Parks and Public Works Director
City of San Marino
7/27/26
Background and Assignment
You recently contacted me about three city owned oak trees that you were concerned about. I inspected the oaks earlier this year (January and May), and recommended that they be removed. You asked me to perform sonic tomography1 to provide further information.
I traveled to the City of San Marino on July 23, 2026. I assigned numbers 1-3 to the subject trees for identification purposes within this report. I took photographs and performed sonic tomography testing at two elevations on the trunk of each subject tree.
Limits of The Assignment
• Observations made in the following report are limited to those which are subject to this report only and based on sonic tomography testing done at two elevations on the trunk of each subject tree.
• They are also limited to what was observed at the time of inspection only. No additional in-depth above or below ground inspections were performed. Many such inspections may be necessary to be more conclusive about what was observed and are not included as part of this report.
• The following report is by no means to be considered as a formal risk assessment for the subject trees. All trees represent some risk of failure; especially those with observed defects. Even with a limited evaluation such as this, there is no guarantee that a tree will not fail unexpectedly. Trees are dynamic living organisms subject to many influencing factors. All trees are potentially hazardous regardless of their apparent health, vigor, or structural integrity. It is impossible to be 100% sure that a tree is absolutely safe. I recommend that you hire a qualified arborist to perform a risk assessment for the subject trees as soon as possible.
You as the tree owner/manager can decide how much risk you are willing to 1 Words in bold appear in glossary
pg. 2
accept, weighed against the value and benefit that you receive from the subject trees.
Observations
The subject trees were all coast live oaks (Quercus agrifolia) and were located within the parkway (between the street and sidewalk) adjacent to the following addresses; Tree # Address
1 1430 Cambridge Rd. (Tree is located on Monterey Rd.)
2 2290 Sherwood Rd.
3 1101 Lorain Rd.
Oak 1
There was irrigated turf within the parkway near Oak 1. Irrigation did not appear to be directed against its base. There was a small conk that appeared to the fruiting body of a Ganoderma fungus (Ganoderma spp.) on the east side of its trunk (see Attachment A:
Photo 1).
The oak’s trunk flare did not appear to be well developed. Expansion of trunk tissue within the root transition zone was not present within most areas near the soil line (see Photo 2). Transverse cracks were seen on exposed portions of buttress roots (see Photo 3).
Foliage was sparse within its canopy; however, it appeared that regrowth had occurred since my previous site visit (last January). Several branches were over extended and appeared to be carrying excessive load.
Oak 2
Oak 2 was surrounded by ivy within the parkway. Its trunk flare was non-existent in most areas near the soil line (see Photo 4). There were obvious signs of decay within the oak’s lower trunk where response growth had formed around necrotic tissue (see Photo 5).
Oak 2 had low foliage density and an abnormal amount of deadwood within its canopy.
Oak 3
There was irrigated turf within the parkway near Oak 3, however, it did not appear to be directed against its trunk. There were obvious signs of decay within the lower trunk; cavities were present on its east and west sides. Necrotic tissue, which had been obscured by secondary bark, could be seen surrounding the two cavities.
Several conks were present at the base of the oak. They appeared to be fruiting bodies of Reishi fungus (Ganoderma lucidium).
Foliage density was low within its canopy and there was an abnormal amount of pg. 3
deadwood at branch extremities.
Discussion
A tree’s heartwood is often located within the center of the trunk. In most trees, heartwood tissue is dead and does not contribute as much to stability as outer parts.
Depending on species and age, it is often absent within many mature trees creating a void.
Live vascular tissue is normally located within the outer portions of a tree’s trunk forming a cylindrical shell wall. It is more critical for structure and tree health than interior parts.
When the perimeter of a tree’s trunk is compromised, its vascular capacity can be diminished. Sometimes, but not always, the condition of a tree’s foliage can be an indication; deadwood and/or sparsity within a tree’s canopy can be an indication of internal decay. This can especially be true when such symptoms are seen in the uppermost portion of an oak where circulatory demand is greatest.
Sparse or discolored foliage throughout the entire canopy can be a sign of a stressed condition for other reasons. This can sometimes be due to poor soil conditions, root disfunction, soil contamination, insect feeding, pathogenic activity, or other causes. A healthy and vigorous oak tree normally has dark green and dense foliage with large leaves that have a glossy appearance.
Trees feed themselves through a process called photosynthesis which occurs on individual leaves. Low foliage density results in diminished photosynthetic activity and a stressed condition where resources are limited. It often predisposes a tree to attack from predatory insects or pathogens which it would normally fend off.
Mature coast live oak trees often contain decay within their roots and/or lower trunks due to Oak Root Fungus (Armillaria mellea). ORF is a fungal pathogen that usually forms below ground where conditions are favorable for its development. A healthy tree will have a well-developed flaring out of trunk material where it transitions into roots near the soil line. A flattened or concave appearance of the flare can result where tissue has been consumed.
ORF can eat away roots and progress upwards into the lower trunk causing decay. It is often concealed by secondary bark which is disfigured, has a rough texture, and has a distinct appearance. In addition, bulges of response growth will sometimes develop to compensate for the loss of underlying vascular tissue. It is generally accepted that trees in this condition are in decline and more prone to failure than those that are not.
pg. 4
Ganoderma fungus is a very common cause of root and butt rot in urban trees. Infected trees will often fail eventually as decay progresses. Conks develop from Summer to Fall2. The size of the fruiting body can sometimes be correlated to the number of years a tree has been infected.
Sonic Tomography Testing
I performed testing on the subject trees utilizing a Rinntech sonic tomography device which measures stress wave velocities between sensors placed on a tree’s trunk or branch. When defective wood or voids are present, stress wave velocities are inhibited.
They generally travel faster through healthy, dense wood.
The device creates graphic images illustrating possible wood strength properties within cross-sectional areas where tested. Different color options can be selected to display results. For our purposes, sound wood would be shown in green where the highest velocities are realized. Unsound wood would be displayed in yellow and red. Red usually represents areas where stress wave velocities are the lowest; indicating where wood is severely compromised or absent. Areas of the graphic shown in yellow will often indicate where incipient decay is present.
Oak 1
I tested the trunk of Oak 1 at two elevations. I placed 18 sensors at 10 centimeters above grade and 21 sensors and 35 centimeters. Results of the testing done at the lower elevation (10cm) seemed to indicate that some compromised wood was present within the center of the cross section (heartwood) which is to be expected. Mostly sound wood was present elsewhere. Results of the test performed at the higher elevation showed similar conditions in the center, however, there appeared to be more incipient decay in outer portions. A small pocket of unsound wood between sensors 3 and 4 could indicate where tissue has been consumed by Ganoderma fungus (see Attachment B: Test Results/Oak 1).
.
Oak 2
Testing was done at 20 and 30cm utilizing 15 sensors on the trunk of Oak 2. Results of both tests indicated severely compromised wood or voids within most of the trunk. A small portion of sound wood could be seen on the tree’s west side between sensors 9 and 14 (see Attachment B: Test Results/Oak 2).
Oak 3
Oak 3 was tested at 20cm with 19 sensors and 75cm with 18 sensors. Results of the test at 20cm showed unsound wood on the tree’s west side between sensors 14 and 17 that appeared to be associated with the defect seen on the trunk (see Photo 6). Other portions of the trunk perimeter appeared mostly sound, however. 2 Luley, Christopher j. 2005; Wood Decay Fungi Common to Urban Living Trees in Northeast and Central United States.
pg. 5
Results of the test done at 75cm indicated a smaller pocket of compromised wood on the oak’s west side and minor areas of incipient decay elsewhere (see Attachment B:
Test Results/Oak 3).
Conclusion
Oak 1
I was surprised by the results of the sonic tomography testing on Oak 1. I expected to see much worse conditions within its trunk; especially at the lower elevation.
Resprouting of foliage within its canopy was also encouraging.
I am concerned about incipient decay found in the second test (35cm), the inadequate trunk flare, cracks in buttress roots, Ganoderma fungus, and excessive branch loading. I believe that branches of Oak 1 could fail if nothing is done. The oak’s inadequate trunk flare and cracks seen in buttress roots could indicate root decay. Further testing would have to be done to be more certain, however.
I am unsure why the oak has such low foliage density; it could be from compromised roots or for other reasons. It may have predisposed it to attack from pathogens which has already begun. I believe that if conditions do not improve quickly, tree mortality is inevitable.
Oak 2
The results of the testing on Oak 2 were what I expected. It was one of the worst results I have encountered. That is probably because I would not normally bother testing a tree with such obvious defects. I believe that its branches, trunk, and roots are structurally compromised; it could fail at any time.
Oak 3
Based on the results of sonic tomography testing, I believe Oak 3 has severe decay within its trunk and possibly its roots. The conks at the base of the oak and obvious signs of decay on its trunk were alarming to me. I believe its poor foliage characteristics were due to circulatory impairment. I believe it is subject to failure at any time.
Recommendations
Oak 1
• Prune over extended branches under the direction of a consulting arborist immediately to prevent limb failures.
• Perform a root crown excavation and inspection and provide further recommendations based on findings.
Oak 2
• Remove tree immediately. Work should be done with the use of aerial equipment as the added weight of a tree climber could lead to a structural pg. 6
failure.
Oak 3
• Remove tree immediately.
Let me know if I can be of further assistance in this matter,
Peter Harnisch
pg. 7
Attachment A: Photos
Photo 1
Photo 2
Conk
Poorly formed trunk flare
pg. 8
Attachment A: Photos
Photo 3
Cracks in buttress roots
Obvious signs of decay
Photo 5
Photo 4
Poorly formed trunk flare
pg. 9
Attachment A: Photos
Photo 7
Photo 6
Conks
Obvious signs of decay
pg. 10
Attachment B: Test Results/Oak 1
Results of the test
done at 10cm shows
compromised wood
within the trunk
center (heartwood)
which is to be
expected. Wood
quality elsewhere
was good.
Results of the test at
35cm seemed to
indicate that more
incipient decay was
present within
peripheral portions of
the trunk than what
was seen in the first
test.
pg. 11
Attachment B: Test Results/Oak 2
Results of the
first test at 20 cm
shows a large
area of severely
compromised
wood or voids
within the trunk.
Similar results
were seen in
the second test
at 30cm.
pg. 12
Attachment B: Test Results/Oak 3
Results of the test
at 20cm indicated
poor wood quality
on the west side of
the trunk where
the defect was
seen and sound
wood elsewhere.
The test at 75cm
showed a smaller
pocket of decay on
the west side of
the trunk and
where Ganoderma
fungus may be
consuming tissue
between sensors 3
& 4
pg. 13
Glossary
Aerial equipment- Devices used to provide temporary access for people or equipment to inaccessible areas, usually in height.
Buttress root- A root at the trunk base that helps support a tree and equalize mechanical stress.
Butt rot- A fungal decay of the basal portion of a tree trunk generally involving the heartwood and caused by polypores.
Canopy- The part of the crown of a tree composed of leaves and twigs.
Cavity: Empty space with a solid object.
Circulatory- Related to the system within trees composed primarily of xylem and phloem and is essential for transporting water, nutrients, and sugars throughout the tree supporting its growth and health.
Circulatory impairment- A condition which restricts or limits the normal circulatory function of a tree or plant.
Concave- Having an outline or surface that curves inward like the interior of a circle or sphere.
Conk- The visible fruiting body of a fungus.
Cross sectional- exposed by making a straight cut through a solid form, especially at right angles to an axis.
Decay- A gradual falling into an inferior condition; progressive decline.
Decline- Gradual loss of vigor and health.
Defect- Imperfection, weakness, or lack of something necessary. In trees, defects are injuries, growth patterns, decay, or other conditions that reduce the load-bearing capacity.
Foliage- The leaves of a plant collectively.
Foliage density- A measure of the amount or concentration of leaves within a plant collectively.
Fruiting bodies- A specialized spore-producing structure, especially of a fungus.
Fungal pathogen- Fungi that cause disease in humans or other organisms. pg. 14
Glossary
Heartwood- Central wood in a branch or trunk characterized by being composed of dead cells, generally darker as compared to the outer sapwood.
Incipient decay- Wood in the early stages of infection or invasion by a wood decay fungus, so that the wood is not yet evidently softened.
Load- The amount of weight carried.
Necrotic tissue- Tissue where the death of cells has occurred due to severe disease or injury.
Pathogenic- An organism that causes disease.
Perimeter- The continuous line forming the boundary of a closed geometric figure.
Photosynthesis- A process in green plants by which light energy is used to form glucose from water and carbon dioxide.
Response growth- growth which develops in reaction to an external stimulus.
Root crown excavation- Process of removing soil to expose and assess the root crown of trees.
Root transition zone- The area where roots meet the stem. It is characterized by an area of elevated radial growth and increased diameter at the base of a tree.
Secondary bark- Bark which is formed subsequent to original tree bark.
Shell wall- The outer walls of a hollow structure such as a pipe or a tree limb.
Sonic tomography- The use of multiple sensors placed around a tree’s trunk to record sound waves traveling through the wood, with measurements resulting in a picture of internal density characteristics.
Stressed condition- A condition in which the plant growing in non-optimal or poor state that negatively influences the plant growth, crop productivity, reproductive capacity, or death if the stress exceeds the plant tolerance limits.
Stress wave- An acoustic emission used in tomography testing.
Transverse- Situated or extending across something.
Trunk- Main or central stem of a tree.
pg. 15
Glossary
Trunk flare- Area at the base of a tree where trunk diameter is expanded as the trunk transitions into roots.
Vascular capacity- The ability of an object; usually a tree or plant, to perform vascular functions.
Vascular tissue- The tissue in plants that is arranged in long, discrete strands called vascular bundles. These bundles include both xylem and phloem, as well as supporting and protective cells in trees and other plants that develop wood.