Text from
the OSHA Logging Compliance Directive, CPL 2-1.22J.
Definitions and clarifications
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11. Paragraph (h) Tree Harvesting
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f. Paragraph (h)(2)(vii) - Backcuts
(1) Open Face felling. OSHA has revised the final rule to clarify that the
requirements that backcuts be placed above the level of the horizontal face cut does not
apply to open face felling since there is no horizontal face cut where this method is
being used.
(2) In open face felling two facecuts are made diagonally into the stem producing a
notch that is very open (i.e., 70 to 90 degrees). The openness of this notch allows the
tree either to fall completely to the ground, or to fall a much greater distance than in
conventional cutting before the notch closes and the hinge breaks.
(3) Where the tree is able to fall a greater distance before pressure is placed on the
hinge, the tree is more likely to fall in the intended direction and is less likely to
kick back off the stump when the notch does close.
(4) Humboldt cutting The requirement that the backcut be placed above the level
of the horizontal facecut does apply when the Humboldt cutting method is used. In the
Humboldt cutting method, a horizontal cut is made into the face of the tree and a notch is
cut into the stump below the horizontal cut at an angle. By contrast, in conventional
felling, the notch is cut at a diagonal above the horizontal facecut.
(5) In logging operations where the Humboldt method is most heavily used, fellers most
often only cut a notch no greater than 45 degrees, making this method similar to that of
conventional felling. Fellers do this to keep the stumps as short as possible and thereby
reduce the loss of wood. At 45 degrees, however, the face notch alone does not fully
address both the hazards of misdirected falling and kickback.
(6) Proper backcuts that provide sufficient hinge wood are critical. Sufficient hinge
wood helps to hold the tree to the stump during most of its fall and thereby allows the
hinge to steer the falling tree in the right direction. If the hinge is inadequate or if
the pressure is placed on the hinge, it will break too soon and the tree will be left
without a steering mechanism. Without the hinge wood, the tree may twist and bend, and
fall in the wrong direction.
(7) Placing the backcut above the horizontal face cut is also necessary to provide a
platform to block the tree from kicking back once the hinge does break. Where there is
potential that the face notch will close before the tree hits the ground, which is the
case with most cutting using the conventional and Humboldt methods, this platform is
necessary to prevent kickback. Where the backcut is at the same level as the horizontal
cut, there is no platform to block the backward movement of the tree should kickback
occur.
(8) OSHA has not specified in the final rule how far above the face cut the backcut
must be placed. OSHA believes that a backcut placed at least one inch above the face cut
creates an adequate platform to prevent kickback and to allow the hinge to direct the
falling of the tree. OSHA believes that a one-inch platform would provide an adequate
margin of safety for the feller while still providing the contractor with a fairly
square-end log.
NOTE: OSHA's decision to require that backcuts in Humboldt cutting be above the
horizontal face is based in part on the fact that most loggers currently using this method
are making the notch the same size as in conventional felling--45 degrees. A 45-degree
notch is generally not open enough to control for both misdirected falling and kickback
hazards. However, where a notch of 70 degrees or greater is cut, the notch in Humboldt
cutting acts as it does in open face felling. As discussed above, in open face felling,
because of the 70-to-90 degree notch, it is unlikely that the tree will fall in the wrong
direction or kickback, due to the openness of the notch rather than the type of cutting
method being employed. Where the notch is at least 70 degrees, it is not as critical that
the backcut be above the horizontal face cut or the notch of the face cut, regardless of
whether the open face or Humboldt method is being used.
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