Abstract: At approximately 2:00 p.m. on February 12, 1990, Employee #1 and three coworkers were installing a rubber flexible liner in a 12 ft wide by 20 ft long by 12 ft deep excavation. The walls of the excavation were vertical. The employees were hammering metal stakes into the walls to hold the liner in place when the west wall caved in, burying Employee #1. Rescue attempts were unsuccessful, and the medical examiner listed a fractured skull as the cause of death. Causal factors of this accident include unstable soil; the lack of shoring or sloping; the extra pressure of the excavated dirt on the trench walls; vibration and cracking of the soil caused by driving stakes into walls; lack of training in the recognition, avoidance, and prevention of excavation hazards; and the lack of personal protection equipment (e.g., hard hat). Soil samples taken by OSHA showed it to be an unstable silty clay. At the time of the accident the weather was mostly sunny and 67 degrees. There had been no precipitation 48 hours prior to the cave-in.