Abstract: At 2:45 p.m. on June 22, 2023, Employee #1 was operating a CAT D9T dozer on top of the 380 Bench in the mine quarry, preparing it for pre-blast drilling. Employee #1 was removing large rocks to flatten the bench area in preparation for the drilling rig to enter the bench. The 380 Bench did not have any visual references, such as berms, delineators, signs or other indicators, to identify the edges. After a push of materials to the southwest edge, Employee #1 reversed the dozer approximately 30-40 feet before making a turn towards the northeast. Employee #1 did not slow down or stop before rolling over the edge of the high wall at an approximate 40 to 45-degree angle to the direction of the high wall edge. The dozer rolled onto its right side and stopped upside down on the roll-over-protection system frame above the operator's cab and against a boulder. The roll was approximately 40 feet downward to the 320 Bench. Employee #1 was not wearing a safety belt, which allowed him to fall out of the operator's seat downwards into the cab's roof, and he suffered fatal head and neck injuries. Paramedics pronounced Employee #1 dead on arrival.