Cement Finisher Electrocuted
The National Institute for Occupational Safety and Health (NIOSH), Division of Safety Research (DSR), performs Fatal Accident Circumstances and Epidemiology (FACE) investigations when a participating state reports an occupational fatality and requests technical assistance. The goal of these evaluations is to prevent fatal work injuries in the future by studying: the working environment, the worker, the task the worker was performing, the tools the worker was using, the energy exchange resulting in fatal injury, and the role of management in controlling how these factors interact.
On February 25, 1988, a 42-year-old male cement finisher was electrocuted when the metal handle of a cement-finishing bull float he was using contacted a 13.8-kilovolt (kV) power line. The victim then fell 55 feet to a concrete sidewalk.
State Occupational Safety and Health Administration officials notified DSR of this fatality and requested technical assistance. On March 30, 1988, NIOSH met with employer representatives, conducted a site visit, and discussed the incident with the OSHA Compliance Officer and the county coroner.
Overview of Employer's Safety Program:
The victim had been employed for the past 7 months by a general construction contractor. At the time of the incident the company employed 450 people. The company has a written safety policy and safety program and provides on-the-job training for all new employees. The president of the company manages the safety program.
Synopsis of Events:
In June 1987, the company began construction of a hospital parking garage in a metropolitan area. The company asked the local utility company to insulate three-phase 13.8-kV power lines in the vicinity of the garage since a crane used for handling materials would be operating nearby. Of the three existing lines, the utility company covered only the line closest to the structure with an insulating sleeve. When the job foreman asked why they had not insulated all three lines, representatives of the utility company replied that they had insulated the line most likely to be contacted.
By February 1988, construction had progressed to the fifth level. The parking garage was designed with a 42-inch-high barrier around the perimeter of each level. This concrete barrier was placed on the floor of each level and served as fall protection. Additionally, a 3-foot-wide walkway with 3-foot-high guardrails was installed around the outside of, but somewhat lower than the barrier.
On the day of the incident, the victim was using an aluminum bull float to finish concrete placed for the floor of the fifth level on the power line side of the structure. The handle of the bull float consisted of two 10-foot sections of aluminum pipe. The fifth floor was at approximately the same level as the power lines, which ran parallel to the edge of the structure at a distance of 14 feet.
At some point when the victim was pulling the bull float toward him, the aluminum handle contacted one of the uninsulated power lines. The victim then fell approximately 55 feet to a concrete sidewalk. Although a hospital security guard heard a man yell and saw the victim falling, no one actually saw the victim fall over the barrier and walkway guardrail. The victim may have been sitting on top of the barrier when the bull float handle contacted the power line. This could explain how he fell over the walkway as well.
The security guard summoned the emergency medical service (EMS) personnel. The EMS personnel transported the victim to the hospital where he was pronounced dead. Meanwhile, a construction worker was stationed as a guard near the bull float since the handle was still lying across the power lines. The electrical utility company personnel arrived approximately 1 hour later, de-energized the lines, and removed the bull float.
Cause of Death:
The deputy coroner listed the cause of death as electrocution and traumatic injury.
Recommendation #1: The construction company should conduct separate hazard analyses prior to initiating each distinct phase of the project.
Discussion: The process of construction results in a continually changing worksite. Each phase introduces new hazards or changes the characteristics of existing hazards. Therefore, construction companies should use a phase hazard analysis approach.
Initial notification of the electrical utility company occurred during an early phase of the project, when the primary electrical hazard was the possibility that a crane would contact nearby power lines. The finishing work on the fifth level of the structure introduced additional hazards, including the potential that the bull float handles would extend beyond the nearest insulated line and contact an uninsulated line. Although the job foreman noted that not all power lines were insulated, this observation was not made within the context of a formal hazard analysis. Hazard analysis requires not only the identification of potential hazards, but also the development of methods of eliminating or controlling the hazards.
In this case, the construction company should have insisted that all three power lines be insulated.
Recommendation #2: Upon request, the electrical utility company should routinely insulate all power lines which are in such close proximity to a work area that workers, or their tools or equipment, could potentially contact them.
Discussion: In this incident, only the power line closest to the structure was insulated since it was thought to be more likely contacted. Although electric company representatives may not have foreseen that tools with long, conductive handles (such as bull floats) would be used as the construction progressed, routinely insulating all lines proximate to a worksite is a prudent approach. If all the power lines in this instance had been insulated with sleeves, this death might not have occurred.
Recommendation #3: Tool handles used in proximity to power lines should be constructed of non-conductive material.
Discussion: The bull float handle in this incident was constructed of aluminum, an excellent conductor of electricity. This fatality might have been prevented if the bull float handle had been constructed of a non-conductive material such as fiberglass.