Abstract: Some employees were installing a new 2.0-meter-diameter sewer line in a trench. An existing 0.7-meter-diameter line ran parallel to the new line. A concrete saddle had previously been installed over the existing clay tile pipe to protect the pipe from an electrical duct that ran perpendicular to the sewer line. The concrete electrical duct and the saddle had been poured at the same time, and no distinctive line was showing between the two. The saddle was about 0.6 meters thick, 0.6 meters wide, and 0.6 meters long. The employees were using a jackhammer to chisel the concrete away from the old pipe because the saddle interfered with the new line. The employees drilled some horizontal holes into the saddle about 100 millimeters below the electrical duct. The superintendent and foreman got into the hole and asked two employees how long it was going to take to remove the concrete saddle. One of the employees stated that it would take about 2 hours at this rate, and the supervisors apparently left the hole. With both employees holding onto the jackhammer, they brought it down at an angle to the concrete saddle. Neither employee was using electrical protective equipment. The jackhammer penetrated the electrical duct and a 13.8-kilovolt underground power line, causing an electrical fault. The ensuing electric arc threw both employees backward into the wall of the trench. One of the employees received an electric shock and sustained severe burns to his arms. The second employee received an electric shock and sustained burns to his left arm and shoulder. The employees were hospitalized for their injuries.