Consulting Arborist, Pleasant Hill, CA
An artificial structure secures this large oak in a
road median against mechanical failure.


Tree Risk Assessment, Pleasant Hill, CA
Excavation of soil reveals absence of supporting
roots due to long-term decay.

Tree Risk Assessment

Joe McNeil's years of operating a tree service, climbing and working in trees, combined with an overall interest, education and training in the mechanical properties of wood and trees, and observations and analysis of dozens of failed trees provide him with an advantage in risk analysis and assessment.

Tree risk assessment and management is not precise and is not accomplished by measurement and calculation. It is accomplished by observation, thought and judgment of the experienced and trained arborist.

During the examination of the tree it may be necessary to excavate soil from the base to allow inspection of roots that may be decayed. It is sometimes necessary to climb the tree or use a lift to inspect aerial defects.




Tree Risk Assessment, Pleasant Hill, CA Information may be gained from simply tapping the tree with a mallet. Other times we may use a Resistograph. A Resistograph inserts a 3 mm diameter probe to a 15 inch depth into the tree. It measures wood toughness along that track and converts the measurement into a graph that can be used to infer decay, cavities, internal knots, or other features.

An example of one such graph can been seen here.


The low flat portion of the trace reveals an interior cavity or advanced decay in an oak tree.

Another instrument we have available uses impulse compression waves from an array of sensors to create both horizontal and vertical maps of the varying wave transmission speeds within the tree interior. These variances correspond to different defects that can be inferred from the images. Different graph types are available to assist in distinguishing one defect type from another.


To the left in the image above, the horizontal tomogram, to the right, the cross section approximately at the imaged section. A faint line outlines visible decay to approximately the extent shown by the instrument as slow sound transmission. A vertical section can also be produced.

While these instruments are new and impressive they simply provide the arborist more information with which to make an informed judgment. They do not provide certainty. The final assessment is never a calculation, always a judgment.

Joseph McNeil Consulting Arborist | Pleasant Hill

Serving northern California and the western United States, including Walnut Creek, Alamo, Danville, Lafayette, Orinda, Pleasant Hill and San Ramon, California.