Abstract: Employee #1 was working from a 12 ft stepladder inside a large water containment structure under construction. He was threading bolts through holes in the structure to a coworker on the outside, who would then attach a nut to the bolt and weld the assembly in place. The holes were either 11 or 13 ft from the floor. Employee #1 had just finished threading a bolt when he fell 12 ft off the ladder onto the concrete floor. He suffered blunt trauma injuries to his chest, from which he died. The weather was favorable at the time of the accident, although it had rained the day before and was damp inside the structure. The concrete floor was also covered with mud and many puddles. No auxiliary lights were being used making it darker inside the structure than outside, although no coworkers had indicated, either before or after the accident, that visibility was a concern. The stepladder was inspected and found to be in good condition, and the non-skid surfaces of the steps showed minimal wear. There were no witnesses to the accident. Employee #1 had complained of illness the morning of the accident. The medical examiner's report stated that he was a heavy smoker, but did not have any serious medical history.