2008 Fireline Fatality Report

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about page 115

A decision was made to fall a large ponderosa pine (36.7” at the point of the cut). Downslope from the ponderosa pine was a 54” DBH sugar pine that had an uphill lean and a large cat face on the uphill side. When cut, the ponderosa pine fell downslope toward the sugar pine. It was contact with the sugar pine, or vibration from the ponderosa hitting the ground, that caused a portion of the sugar pine, approximately 120 feet long, to break off and fall upslope, hitting FC1 resulting in severe injuries.

Technical Assessment of Accident Site
Due to the lack of eye-witness accounts, a number of key facts are unclear; therefore actual events have been pieced together from interview statements and evidence at scene. FC2 and FC3 are the only surviving witnesses to the accident and they have not granted interviews to the Serious Accident Investigation Team. While it is impossible to determine at this time who actually fell Tree 1, it is possible for experienced observers to read the stump, the lay of the felled tree, and the felling area to determine how the felling of Tree 1 set into motion the sequence of events that lead to FC1 being injured.
Starting at DP 17, EM-CAPT proceeded east along the dozer line cutting an undetermined number of hazard trees. When the crew members reached the accident site one of them proceeded to fall Tree 1. Tree 1 was 36.7” at the point of cut. The ponderosa pine, when examined, appeared to be green with no readily apparent defects that would have required it to be felled as a hazard tree.
The first step in a procedural approach to felling is to survey the tree to be felled and the felling area for any hazards. Tree 2 would have presented a considerable hazard to anyone upslope from its base.The chainsaws EM-CAPT had with them had bar lengths of 28” and 32”; the diameter of Tree 1 at the point the cut was made was 36.7”. Regardless of which saw was used, the sawyer would have had to cut from both sides of the stump in order to complete the undercut. During this process, the sawyer experienced difficulty in obtaining a single plane, or hinge, across the diameter of the stump. This hinge is critical to the process that directs the tree into the undercut and the intended lay.
Closer inspection revealed that the sloping section of the undercut was not cleaned sufficiently as to provide a single plane across the diameter of the stump. The stump exhibits two distinct horizontal (gunning) cuts and two sloping cuts. Multiple Dutchmen that would have altered the holding wood were also present.
Due to the multiple horizontal (gunning) cuts and the multi-faceted sloping cut, it is impossible to accurately determine the exact intended lay of Tree 1; however it appears that the intended lay was to be downslope and to the left (looking downslope) of Tree 2 and 3. The sawyer made the decision that the undercut was completed sufficiently to direct Tree 1 into the intended lay, and proceeded with the backcut. As the backcut was initiated, it appears that the tree may have started to fall before the feller was able to get a sufficient amount of the holding wood cut.
The large amount of holding wood (16” wide) left on the stump can be attributed to Tree 1 starting to fall earlier than expected due to a heavy sidehill lean or a large amount of limb weight. Because of the interaction of the multi-faceted undercut, the Dutchmen present in the undercut and the heavy lean, the tree fell in a sidehill direction, possibly as much as 20 to 40 degrees to the right of the intended lay.

As Tree 1 fell, it is possible that it contacted Tree 3, breaking it off approximately 85’ from the ground. (Statement: CRWB1 [E-10]; MOI: FAL1[F-20] )
As Tree 1 continued to fall, it is possible that it contacted the bole or a limb of Tree 2.
It was this contact, or the vibration from Tree 1 hitting the ground, that caused an approximately 120’ section of the severely weakened Tree 2 to break off 16’ from the ground and fall upslope

It is highly probable that a large cloud of ash and dust was generated when Tree 1 hit the ground. This would have obscured any debris falling toward FC1. Based on the location of the broken pieces of Tree 2 and the known location of FC1 after the accident it was likely that a section of Tree 2, over 8’ in length and approximately 20” in diameter, impacted FC1, causing severe injuries.

Tree 1 was a class C tree. The stump measured 36.7” in diameter at the point the cut was made.
The highest saw qualification of any of the crew members present was that of a faller B.
The undercut of Tree 1 was not cleaned sufficiently as to provide an adequate “hinge” to direct Tree 1 during the felling process.
The undercut of Tree 1 exhibits two distinct horizontal (gunning) cuts and two sloping cuts. Multiple Dutchmen that would have altered the holding wood were also present. (See photo 2)
Tree 1 fell away from its intended lay due to lean, possible limb weight, and an inadequately cleaned undercut.
Tree 1 appeared to have been a sound, green tree with no readily apparent defects that would have required it to be felled as a hazard tree.
FC1 had not completed First Aid/CPR training. First Aid/CPR training is a prerequisite for S-212 (Wildland Power Saws).
The JHA for tree felling provided by EM after the accident was not adequate for the activity of tree felling, additionally no evidence could be found to indicate the JHA had been reviewed by EM or a line supervisor. Recommendations:
Fallers must only fall trees that are within their qualification level, unless being directly supervised by a faller of appropriate qualifications.
Fallers must survey the cutting area for hazards and identify escape routes/safety zones before the felling operation can commence.
Fallers must retain control of the cutting area. (S-212 identifies the cutting area as two times the height of the tree being cut; OSHA Logging Standards 1910.266(h)(1)(iv) states: “No employee shall approach a feller closer than two tree lengths of trees being felled until the feller has acknowledged that it is safe to do so, unless the employer demonstrates that a team of employees is necessary to manually fell a particular tree.”)
Undercuts must be completely cleaned.
Techniques such as boring back cuts and quarter wedging should be considered on leaning trees

what is a boring back cut? I think I know but Im not sure I understand the principle.

[ROOTSXROCKS]

nevermind I continued reading

Boring Backcut: A felling method that utilizes a back cut where the chainsaw bar is inserted behind the holding wood area and the direction of cut proceeds away from the holding wood toward the back of the tree to fell. This is a particularly good method to use on leaning tress as it prevents the tree from pulling a large amount of holding wood and possibly barberchairing.