EE WAS PERFORMING ROUTINE MAINTENANCE ON THE REJECT CONVEYOR ON THE PRIMARY PLANT. HE STEPPED AWAY AND SLIPPED ON A ROCK AND TORQUED HIS BACK. MINOR PAIN: CONTINUED WORK/FINISHED SHIFT. NEXT DAY EE WENT TO HIS PERSONAL DOCTOR. ACCIDENT NOT REPORTED TO SUPERVISOR UNTIL 7/16/04. POOR GROUND CONDITIONS LED TO ACCIDENT - SPILLAGE FROM THE CONVEYOR BELT IN EE'S WORK AREA.