Even the simplest of safety procedures could
have prevented this backyard electrocution
While assisting a private contractor replace the old gutters on a modest two-story home in Greensboro, N.C., one sunny morning, a young man heard a loud noise from the area of the house where his boss had been working. The assistant was standing on a small stepladder on the house's raised wooden deck, preparing the roof edge to receive a new gutter, when he heard the noise and noticed the aluminum ladder his boss had been standing on was no longer in sight.
He immediately got down off the deck and walked around the corner of the house and found the contractor lying face up on the grass, about 8 to 10 feet away from the house. He was shaking and appeared to be having difficulty breathing. Despite calls to 9-1-1 and emergency rescue efforts, the contractor died on the scene.
No blood was found on or near the contractor's body, so it was fairly safe to rule out a blow to the head or another part of his body. The shaking of the body suggested that his heart was in fibrillation, which was confirmed by the medical personnel who later determined he had been electrocuted.
Before the accident, the contractor had been working his way around the house, using a 22-foot extension ladder to reach the gutter. It was at the northwest corner of the house, where the utility service drop for the house was located, that the accident took place (Fig. 1).
When he reached this corner, he would have had to climb down the ladder to move it around the service drop. Before he moved it, the top of the ladder was just lower than the service drop but around the corner. The assistant later stated that he glanced over and saw the top of the ladder slowly move away from the house and around the corner. He suspected that the contractor didn't collapse the ladder prior to moving it because he wanted to speed the job along. But shortly after the assistant went back to his work, he heard the noise and turned to find that the top of the ladder was nowhere to be seen.
We were called in to investigate the cause of the electrocution and provide testimony details for presentation in a court case that had been filed by the mother of the handyman against the electric utility company. I was asked to provide on-site details, photos, and a summary of the sequence of events. All photos and negatives were handed over to the attorney, and an audio summary of my findings was recorded at the scene. By the time we received the case it was already in subrogation. We were contacted months after the accident took place, so the body had already been buried, the ladder had been removed, and the electric utility company had been to the site. As a result, the details of our investigation were based on the evidence as it presented itself.
The assistant's description brought into question what exactly happened. Did the handyman make contact with the utility distribution feeder connected to the service drop or did he bring his ladder into contact with the service drop conductors? With only one witness who had a limited view, it was difficult to answer this question at first, but a thorough recreation of the events revealed that the cause of the accident was as simple as the steps that could have been taken to prevent it.
The facts behind the accident. Our investigation exposed several items of note. First, the corner of the house where the accident took place is located at a high point on the grass-surfaced yard. The surface angles downward from that corner of the house at a 5° slope. The service drop was located on the west side of the house, which was in the shade for most of the morning. As a result, it's likely that the grassy surface was damp with morning dew. Making matters worse, the event took place on a clear sunny day, and sundial calculations revealed that at the time of the accident the sunlight was almost directly parallel to the angle of the ladder against the house. This would have placed the sunlight in the handyman's eyes at the moment he was attempting to move the ladder around the corner of the house.
The 22.8kV 3-phase utility distribution feeder was located about 15 feet from the corner of the house. The conductors were 16 feet above the ground, which placed them in direct line with the height of the service drop. This measurement was estimated based on a comparable height measurement taken off of the raised wooden deck at the rear of the house. The height of the wires met National Electrical Safety Code (NESC) regulations, Table 232-1, which states that the vertical clearance from a “way subject to pedestrians” should be a minimum of 14.3 feet above the ground.
Based on the angle of the grassy surface and the height of the house's northwest corner, we estimated that the contractor would have had to extend the aluminum ladder about 18 to 20 feet to reach the upper corner of the house.
Because the contractor didn't collapse his ladder as he came around the corner, he was putting himself in danger of making contact with the overhead lines. He would have had to lift it up and balance it as he was moving around the corner, and its center of gravity would have been raised, causing it to become unstable and requiring more effort to maintain control. Based on information provided by the assistant, the contractor was about 6 feet tall. After lifting the ladder, he would have added about 2 feet to its extended height. This would most likely place the top of the ladder at approximately 20 to 22 feet off of the ground — about 2 feet above the service drop and well within range of the feeder conductors.
The environment would have also played a part in the unfortunate accident. As he was rounding the corner of the house, the sunlight would have hit him in the eyes, and he most likely lost his concentration for an instant. In addition, the ground had to have been slightly wet from the morning dew because the house was still blocking the grassy surface. These factors could have contributed to a minor struggle to maintain control of the ladder.
We determined that the combination of the sunlight, an imbalanced ladder, and the sloped wet ground more than likely caused him to lose his balance, slant the ladder back toward the distribution feeder conductors, and make contact with them (Fig. 2). The electrical energy would have passed through the ladder, through his body and into the ground, throwing him violently in some direction. The angle of his body indicated he was probably thrown away from the house and landed on his back.
Was the utility line located too close to the house? NESC regulations (Table 234-1) indicate 6.5 feet is the minimum required horizontal distance to a wall of a building. In this case, the horizontal distance between the house and the conductors was approximated to be greater than 10 feet.
Because he was experienced with this type of work, it's safe to assume the handyman was well aware of the hazards presented by the utility service drop, and he must have thought he had sufficient distance to work around the energized conductors. However, he couldn't have anticipated the sunlight or the wetness and slope of the grass. Even if he had walked around the house prior to starting the job, he might not have obtained sufficient information to realize the problem of working at this corner of the house.
The electric utility and the handyman's family settled their case out of court, but the accident ultimately demonstrated the importance of proper safety procedures — even when performing tasks that may have been carried out numerous times before. Though within NESC regulations, the height and displacement of the utility conductors, combined with the factors described above affecting the working area that morning, all contributed to the accident.
The best way to prevent the accident would have been for the handyman and his assistant to draw up a specific plan of action for working around this corner of the house. This could have included employing a safety person at this critical point to hold the ladder or just asking the assistant to help move the ladder around the service drop and the utility conductors. At the very least, the handyman could have avoided the accident by taking the time to lower the ladder while moving it (Sidebar above). Good planning and proper safety procedures could have prevented this needless death.
Cavallaro is an engineering consultant for Forensic Engineering, Inc., in Raleigh, N.C.
Sidebar: Ladders and Lines Don't Mix
The ladder is one of the most commonly used tools on any construction project, so it's easy to take for granted its danger potential near overhead power lines. The following safety guidelines from the Maryland Division of Labor and Industry Occupational Safety & Health Group may seem simple, but they're worth noting. Remember, safety doesn't have to be complicated.
Never attempt to carry a ladder in a vertical position. Ladders should be lowered and turned horizontally when transported from one location to another.
Extension ladders should be collapsed before lowering from a vertical position.
Never attempt to raise or lower an extension ladder without assistance.
When working around overhead electric lines or with electrical equipment, wooden or fiberglass ladders provide a safer alternative than metal.