WORKER WAS CHECKING OIL LEVEL IN A BULK STORAGE TANK. HE LEANED A CLOSED 6'STEPLADDER AGAINST THE TANK. HE BEGAN TO CLIMB THE LADDER, AT THE 2ND STEP, THE LADDER SLIPPED AWAY FROM THE TANK CAU SING THE WORKER TO FALL AGAINST THE TANK, WHERE HIS CHIN CONTACTED THE LIP OF THE TANK.