A ROOF FALL AT THE AREA OF THE HIGH WALL WAS DISCOVERED IN THE FAN ENTRY. THE ROOF FALL WAS APX. 18 FEET WIDE X 5 FEET LONG X 12 FEET HIGH. THE FALL DID NOT AFFECT PERSONS NOR EQUIPMENT BUT DID RESTRICT THE AIR FLOW. AN ACTION PLAN WAS SUBMITTED, ACKNOWLEDGED AND THE FALL CLEANED UP. ARCHES WERE INSTALLED FOR ROOF SUPPORT THROUGH THE AREA. VENTILATION WAS RESTORED.