Abstract: At approximately 11:00 p.m. on December 30, 1987, Employee #1, a senior backhoe operator and job foreman for United Plumbing & Heating Co., Inc., Columbia, MD, was installing 4 in. PVC sewer pipe for a single family house. After Employee #1 finished excavating a section of the 13 ft deep by 6 ft wide by 15 ft long trench, coworkers entered the trench and connected the house sewer line to the main line, then exited the trench. Employee #1 entered the trench to inspect the connection. While he was bending over, the walls of the trench caved in and completely buried him. He was hospitalized for treatment of a fractured shoulder. There were several causal factors related to this accident: the trench walls were vertical and not supported in any way; the soil was soft, unstable, and damp from rain; the excavated soil was stored at the edge of the opening; the trench was adjacent to a back-filled trench; and the employees were not wearing hard hats.