Date of incident: July 2013
Notice of incident number: 2013108490210
Employer: Power line installation company

Incident summary
A crew was in the process of erecting a hydro tower for a high-voltage power line. One of the workers, a power line technician, took his place on top of a tower leg, preparing to receive a "rack" that would join the tower's four legs. A crane was positioning the rack when a guyline that was supporting the leg broke, and the leg collapsed. When the leg struck the ground, the worker was thrown off the leg. But then his fall protection equipment caused him to bounce back and strike the leg. He sustained serious injuries.

Investigation conclusions

Cause

• Tower leg collapsed after pull line broke: A power line technician was seriously injured when the tower leg that he was working on collapsed after the pull line broke. When the leg struck the ground, he was thrown off the leg. His fall protection equipment caused him to bounce back and strike the leg, resulting in serious injuries.

Underlying factors

• Inadequate risk assessment: The employer's safe work procedures failed to account for several crucial factors, such as weights and rated strengths, and failed to consider the loads and forces involved. With this lack of information, the selection and positioning of the rigging were not adequate to protect the workers. Furthermore, the employer's risk assessment did not anticipate the possibility of a structural failure, given that the power line technicians were anchoring themselves to that structure.
• Inadequate rope used as guyline: The synthetic rope selected as the guyline and pull line was inadequate to support the tower leg. The synthetic rope was tested and failed below the manufacturer's rated capacity. With a worker on the leg, the rigging should have had a safety factor of 10, but it did not. Finally, two additional guylines are required when there is a pull line, unless the system is certified by a professional engineer.

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