Date of incident: August 2021
Notice of incident number: 2021194460018
Employer: Construction company (prime contractor)

Incident summary
At a commercial building construction site, a mobile crane was being set up to lift building materials. During the process of readying the crane for the lifts, the crane’s load line came into contact with the power lines adjacent to the worksite. A worker came into contact with the energized crane while the load line was touching the power lines and sustained serious injuries.

Investigation conclusions

Cause

• Crane rotated because it was not level and swing brake was not applied. The crane was not sufficiently level and the swing brake, which is designed to prevent unintentional rotation of the crane, had not been applied. Because the crane was out of level, the crane’s counterweight was drawn to the low point and the boom swung in the opposite direction, unrestricted by the swing brake. The boom of the crane rotated clockwise, travelling approximately 11 m (36 ft.), and the boom’s load line contacted the 14.4 kV power lines adjacent to the worksite. The worker was walking behind the crane while carrying a piece of rebar, which contacted the energized crane, creating a path to ground.

Contributing factors

• Inadequate pre-work planning. A pre-job safety meeting was not conducted before the crane was set up. The prime contractor provided the crane operator with an overview of the work to be performed but did not fully explain the hazards of the worksite and the specific details of the panel lifting.
• Inadequate assessment of hazard. The prime contractor failed to adequately assess the potential hazard of the 14.4 kV power lines running adjacent to the worksite. The positioning of the crane in relation to the panels to be lifted and the power lines, even though the power lines were outside of the worksite, created a potential breach of the prescribed minimum distance of 3 m (10 ft.) to be maintained. An assessment of the potential to contact the power lines was not performed, and subsequently an assurance in writing from the power service provider, or additional workplace control measures such as a spotter, were not obtained or implemented.
• Constricted work area. The positioning of the crane in relation to the building and worksite office resulted in narrow passageways for workers to traverse. The narrow passageway between the rear of the crane and the worksite office resulted in the 2 m (78 in.) length of rebar being carried by the worker inadvertently coming into contact with the energized crane. The close proximity of the rear of the crane to the worksite office also significantly reduced workers’ ability to observe the position of the crane boom in relation to the power lines.

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