Hazard Tree Inspections
Periodic, thorough, and documented hazard tree
inspections of developed recreation sites are essential to maintain safe
conditions. Annual inspections are required (Forest Service Manual 2333.2), but
two per year are recommended - one during the summer with leaves on and one
during the dormant season. Severe windstorms usually warrant additional
inspections. Every tree in public use areas with the potential to cause
property damage or personal injury should be examined systematically. For
example, begin at the bottom of the tree looking for signs of root or butt rot
and work up the trunk toward the upper crown, noting anything that makes the
tree potentially hazardous. Binoculars are often helpful when examining the
upper trunk and crown (Figure 9). |
Figure 9 - Careful, close examination of
trees during hazard tree inspections is important: a. Ash looks apparently
sound: b. With the aid of binoculars, several conks are visible on the upper
stem indicating advanced decay. |
Walk completely
around the tree so that defects are not overlooked (Figure 7). Document all
hazardous trees and determine what treatments, whether it be pruning, cabling,
or tree removal, is necessary to reduce or eliminate the hazard. Recording
apparently non-hazardous trees also is important; in case of litigation
involving the failure of a tree with no evidence of structural defects, the
inspector or agency may be protected by this "lack of evidence."
Documenting inspections is extremely important. This can involve a simple
notation in the appropriate office file stating when the inspections were done
and by whom, or can entail a more detailed written evaluation and map of all
trees examined. Detailed documentation of hazard tree inspections has several
advantages over merely noting that they were completed. They can be used:
| 1) |
to record recommended
corrective action and when these recommendations were completed; |
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| 2) |
to note changes in
tree condition during subsequent inspections, even with personnel changes
between inspections; |
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| 3) |
as a record of what
trees fail, using the characteristics of those trees to predict the type of
tree likely to fail in the future 2 ; |
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| 4) |
as evidence of the
frequency and intensity of hazard tree inspections in the event of a court case
involving damage or injury; and |
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Figure 7 - Thorough inspection of
potential hazard trees is essential: a. Basswood (arrow) near campsite looks
safe from this perspective. |
| 5) |
as a record of costs involved in
hazard tree inspections and treatments. The obvious disadvantage of detailed
documentation is that it requires more money and time. |
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| The obvious
disadvantage of detailed documentation is that it requires more money and
time. |
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Figure 7 - Thorough inspection of
potential hazard trees is essential: b. Moving 90 degrees to the left, same
basswood is seen to be leaning directly over campsite. |
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Figure 7 - Thorough inspection of
potential hazard trees is essential: c. Moving another 90 degrees to the left,
large hollow in trunk is now visible, indicating advanced decay.
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An example of a
hazard tree inspection survey from is included in Appendix C. Information
recorded in such a survey would include the name of the inspector, date of
inspection, map of potential hazard trees, defects or hazards observed for each
tree, and recommended corrective action. Follow-up action would be documented
when corrections are made.
To determine its relative hazard, each tree with the potential to cause damage
or injury would be evaluated according to the target it would hit in the event
of failure. It would be evaluated also for structural defects, such as decay
and cankers. Trees with multiple defects generally are more hazardous than
trees with a single defect. Trees thought likely to fail before the next
inspection should be removed or otherwise treated to reduce the risk of
failure. |
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2
USDA Forest Service "Report of Tree Failure" can also
be used. See Appendix B. |
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