Tree Risk Assessment

Sometimes an in-field consultation leads to the discovery of a tree defect that requires further investigation. Typical defects include: hollows, decay, cracks, or lean. The defect could be located at the base of the tree or in the upper portions of the tree (such as stems or branches). Often, tree risk assessments are performed on trees near heavily used areas where failure could lead to loss of life or property damage. It is important that defects be examined carefully in order to determine their associated risks of failure. Upon careful examination, arborists can recommend if risks can be mitigated through pruning, cabling, and bracing, or if trees should be removed to eliminate the risk entirely. If the risk is mitigated, it is important to remember that the tree will require future inspections and maintenance.

Property owners and managers have legal responsibilities with respect to trees and unsafe conditions. Specifically, the owner has an obligation to inspect trees periodically for unsafe conditions, and the owner must correct unsafe conditions when they are discovered.

We use several tools to help quantify risk. Climbing inspections by an arborist allow for investigation of the upper parts of limbs and branch unions not visible from the ground. Visual tree assessment (or VTA) can be used to locate areas where defects are likely. Years of experience and extensive training enable our arborists to look for subtle changes in bark texture, color, and patterns that are associated with underlying defects. When suspect areas are located, we may use tools such as a mallet for sounding wood, a thin drill bit and drill to find hollows, or a Resistograph to measure the amount of sound wood in the specific area investigated. The Resistograph provides us with a physical record of wood density and allows us to visualize defects and patterns of decay in trees. We can provide the results of a risk assessment orally or in a more detailed written report.

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