Date of incident: October 2020
Notice of incident number: 2020188270016
Employer: Tree services company

Incident summary
At a private property, workers were removing a Garry oak tree. A worker was in the tree, sectioning a leader (vertical continuation of the main trunk) of the tree, and a ground worker was lowering the cut leader sections via a rigging system. The rigging system consisted of a pulley with a rope fed through it. As the sectioning progressed toward the trunk and the leader sections became increasingly heavy, the worker in the tree redirected the rope held by the ground worker from the pulley, across the tree’s canopy to another limb, and through a friction device. This setup would enable the ground worker to control the descent of the sections more easily. As the worker in the tree completed the cut of a section near the trunk, the rigging system took the full weight of the section. The limb used to redirect the rigging system broke away and crushed the worker against the leader. The worker sustained fatal injuries.

Investigation conclusions

Cause

• Improper worker position. The worker was positioned almost directly below the two high points of the rigging system. When the rigging system took the full weight of the removed section, the side-loading applied to the limb by the redirect caused the limb to break away. It struck the worker in his elevated position on the leader below the limb, crushing him against the leader.

Contributing factors

• Inadequate assessment of hazards. The tree, normally a protected species, had been identified by the municipality where the incident occurred as a candidate for removal. The tree showed evidence of prior limb failures, poor overall condition, incorrectly performed pruning cuts, and potential Armillaria root rot. The cumulative stress of the weight of the removed leader section, the side-loading applied to the limb, and the diminished strength (health) of the limb contributed to its failure at the time of the incident. Neither the increased hazards of a worker working in the tree nor the hazards associated with the deficiency indicators in the tree were adequately considered.
• Inadequate training and experience. The crew lacked adequate experience with the Garry oak species of tree and training to assess the potential dangers associated with the tree. The employer failed to evaluate the crew’s ability to recognize and assess the hazards related to the condition of the tree or the work methods being used.
• Inadequate supervision. The worker in the tree was the designated lead hand. It was not possible to perform the climbing work from within the tree while also providing adequate oversight of the other work at the site. Workers on the ground were routinely in areas with the potential to be struck by objects from above. Also, the hazards created by redirecting the rigging system and side-loading the limb, as well as the worker’s position in the path of potential falling objects, were not recognized. The employer failed to ensure that a supervisor with adequate experience with the Garry oak species of tree was available at the worksite.

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