What to Expect from a Tree Inspection – Limited Visual Assessment

Tree inspections generally come under three types – limited visual assessment, basic assessment and advanced assessment. Over the next few weeks, we will be going into greater detail on each of these types of tree inspections. We will begin with the level 1 assessment, the limited visual assessment.

The Level 1 assessment is a visual assessment from a specified perspective of an individual tree or population of trees to identify obvious defects or specified conditions. A limited visual assessment usually focuses on identifying trees with an imminent and/or probable likelihood of failure. Level 1 assessments do not always meet the criteria for a “Risk Assessment” because they may not include analysis and evaluation of individual trees.

Limited visual assessments are the fastest but least thorough means of tree inspection. They are primarily intended for large populations of trees. The assessment is often done on a specified schedule and/or immediately following a storm to rapidly assess a tree population. Tree inventories are usually considered a Level 1 assessment unless a Risk Assessment is included in the inventory.

The assessor performs a visual assessment by looking for obvious defects, such as dead trees, large cavity openings, large dead or broken branches, fungal fruiting structures, large cracks, and severe leans. The client may specify inspection for certain conditions of concern, such as lethal pests or symptoms associated with root decay.

The process of limited visual assessment should include:

  1. Identifying the location and/or selection criteria of trees to be assessed.
  2. Determining the most efficient route and document the route taken.
  3. Assessing the tree(s) of concern from the defined perspective.
  4. Recording the location of trees that meet the defined criteria.
  5. Evaluating the risk. (Note that a risk rating is optional)
  6. Identifying trees needing a higher level of assessment and/or prompt action.
  7. Submitting recommendations or a report.

Now, the Scope of Work in a limited visual assessment should specify the perspective or type of inspection. The trees can be inspected in one of three ways. First, you walk by the trees themselves. A walk-by is a limited visual inspection of one or more sides of the tree performed as the inspector walks past a tree. The inspector may need to stay on the sidewalk (footpath), on public property or within a right-of-way. The Scope of Work may indicate that the assessor has to walk around certain trees to gain a more complete perspective.

Secondly, you could do a drive-by tree inspection. This is a limited visual inspection of one side of the tree performed from a slow-moving vehicle. The Scope of Work may also specify that the inspector walk around certain trees or record images to verify or document observations. This type of inspection is often performed by municipalities, utilities or other agencies or landowners who have large populations of trees to inspect within a limited budget.

Finally, the inspector could do an aerial patrol inspection. These are made from an aircraft flying over utility rights-of-way or other large areas. This type of inspection is conducted by some electric utility companies or other contractors to identify threats to the electric transmission system. Sometimes, a more detailed, ground-based inspection may be specified to confirm observations. Images may be recorded to document the observations made by the assessor.

When a tree of concern is identified, certain specified information about the tree is recorded. At a minimum, this should include the tree location and recommended remedial action. In addition, the documentation should provide the species name of the tree, tree’s size, defect or condition identified and a work priority. A higher level of inspection may be considered necessary at this point and recommended by the inspector.

A constraint of limited visual assessments is that some conditions may not be visible from a one-sided inspection of a tree. Not all conditions are visible year-round. This type of tree inspection may not be adequate enough to make a risk mitigation recommendation. The assessor may use a level 1 inspection to determine which trees require further inspection at the basic or advanced levels after which an appropriate mitigation can be recommended.

Next week, we’ll discuss the basic assessment. If you have any questions about tree inspections in the meantime, please contact us at 512-341-8888.