Abstract: At approximately 3:00 p.m. on June 17, 2010, Employee #1, a plumber, and the company general manager were laying approximately 475 ft of 4 in. PVC lateral sewer line from a new residential dwelling to a municipal tie-in point. The general manager was operating a Bobcat excavator, Model Number 331E, Identification Number 232711536, while Employee #1 occupied the 4 ft to 7 ft deep trench checking the fall angle of the lateral and connecting gasket joints with grease. Approximately 200 ft into the work, Employee #1 was working in a 7 ft deep part of the trench near a solid wall 2.5 ft wide by 5 ft deep by 33 ft long when it sheared and collapsed. Employee #1 was killed. Upon further investigation, it was learned that nine days prior to this event, the local electric municipal dug and backfilled an underground line from a transformer to the residential dwelling with a trenching machine that made 4 in. to 6 in. wide cuts at a 4 ft to 5 ft depth. The trench wall ran adjacent to the previously trenched electrical line by 2.5 ft. Due to the prior trench work, there was inadequate sloping and backfill and an engineered tension crack which increased the angle of internal friction and shear strength of the wall.