Abstract: At 11:30 a.m. on July 13, 2017, Employee #1 was assisting in the backup roll change on the 9 Tandem Mill. This process required subfloor sections to be removed to access the rolls located in the nine foot pit below. Following the change out, a subfloor section was being lowered back into the pit. It made contact with a fire suppression water line, causing it to rupture. Employee #1 stepped down onto a floor support structure in order to enter the pit to fix the line. The employee slipped and fell into the pit, hitting his head on a backup rail. Employee #1 was removed from the pit by coworkers via a Stokes basket and was flown to a nearby hospital. The employee sustained fractured ribs, spine, and vertebrae, as well as head trauma. Employee #1 was hospitalized for his injuries.