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Worker seriously injured when electric arc flash occurred

Date of incident: March 2021
Notice of incident number: 2021180890003
Employers: Construction company; exterior building finishing firms (2; one subcontracted by the other)

Incident summary
At a multi-unit residential building under construction, a worker standing on a scaffold tried to throw a high-visibility vest to another worker, at ground level. The vest became caught on an overhead power line adjacent to the scaffold. The worker tried to free the vest from the power line with a length of aluminum channel and received an electric shock, sustaining serious injuries.

Investigation conclusions


  • Worker made contact with hazardous energy. The worker, positioned on a scaffold within the limit of approach to an energized 14.4 kV power line, used a 3 m (10 ft.) length of aluminum channel to try to remove a high-visibility vest from the power line. An electric arc flash occurred when the aluminum channel contacted the power line. The current flowed from the power line through the aluminum channel to the worker.

Contributing factors

  • Inadequate information, instruction, training, and supervision. Adequate information, instruction, training, and supervision were not provided to workers, which contributed to scaffolds on the site being constructed incorrectly and within 1.93 m (6 ft. 4 in.) of an energized 14.4 kV power line. The exterior finishing firm did not provide the finishing subcontractor with the scaffold manufacturer’s instructions or adequate information about the location of the power lines. The finishing subcontractor did not provide its workers with adequate instruction and training related to scaffold installation, inspection, or use, as well as working near energized power lines, and did not ensure that its supervisors were adequately trained in the tasks they were assigned to supervise.
  • Inadequate worksite planning and coordination. The construction company (prime contractor) did not effectively plan and coordinate the work activity at the site related to working near energized power lines, and did not take reasonable steps to ensure compliance with its own safe work procedures or occupational health and safety requirements related to the erection and use of scaffolds at the worksite.
       The exterior finishing firm did not ensure the work it assigned to its subcontractors was done safely, including having the finishing subcontractor erect scaffolds to be used by all the finishing firm’s subcontractors. The finishing firm did not ensure that the finishing subcontractor was qualified for the work it was hired to do and did not provide them with adequate information about the scaffolds that they were assigned to erect. Further, the finishing firm did not adequately identify the hazard of the energized power lines in the area where the finishing subcontractor was assigned to erect the scaffolds and did not take reasonable steps to ensure that the scaffolds were erected properly and safe for use before assigning workers to use them.
       The finishing subcontractor failed to identify that installing the scaffolds at the front of the building would breach the minimum safe distance to be maintained from the energized power lines. As a result, no measures were implemented to mitigate the risk of working in close proximity to the energized power lines.
  • Inadequate workplace inspections. Although the prime contractor routinely performed workplace inspections, the inspections were not adequate in identifying the hazardous conditions present. The exterior finishing firm failed to perform any inspections of the scaffolds prior to assigning its subcontractors to use them. The scaffold inspection completed by the finishing subcontractor on February 10, 2021, failed to identify the deficiencies with the installation of the scaffolds, which included, among other issues, that some scaffolds were erected within 3 m (10 ft.) of the energized power lines. In the absence of adequate inspections, workers using the scaffolds were exposed to hazardous conditions that were permitted to persist for close to a month leading up to the incident.

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Publication Date: Apr 2023 Asset type: Incident Investigation Report Summary NI number: 2021180890003