Abstract: At approximately 12:30 p.m. on November 10, 2010, Employee #1 was working for his employer, which had been contracted to install a septic tank in a residential neighborhood using a mobile rat hole drilling rig. Employee was setting up the rat hole drilling rig by guiding the kelly bar into a cookie cutter auger bit that was laying on the ground. The rat hole rig consisted of an 18-foot mast which was hydraulically raised into position and mounted on the bed of a 1985 international heavy duty truck. The rig was powered by a diesel engine that operated the hydraulic system and the ground-level rotary table that spinned the cookie cutter assembly. The cookie cutter was a 28-inch by 28-inch hollow cylinder with an attachment hub on top that the kelly fit into and the bottom cutter consisted of teeth. When the assembly was lowered, it dug a 28-inch by 28-inch hole in the ground. The kelly bar consisted of an internal kelly and an external kelly. The internal kelly fit into the female opening on the cookie cutter, and the external kelly fit over the male protrusion of the cookie cutter. When Employee #1 was assembling the rig, the mast was in the up position and the kelly bar was being lowered. Employee #1 was guiding the external kelly onto the cookie cutter so he could set the pin that keeps the cookie cutter and the kellys attached. Employee #1 looked away during this process and didn't notice the external kelly was hung up on the top of the male protrusion on the cookie cutter and when he went to pin the kellys, the external kelly fell into position on to Employee #1's right hand, partially severing his thumb and finger.