AN UNINTENTIONAL ROOF FALL OCCURRED IN THE #8 RETURN AIRWAY ENTRY, 7000' OUTBY THE ACTIVE WORKING SECTION LOCATED AT SPAD #0458. THE FALL MEASURED 20' LONG X 20' WIDE X 3-5' THICK. THE AIRWAY OR TRAVEL IS NOT AFFECTED BY THIS FALL. THERE ARE 2 RETURN AIRWAYS IN THIS AREA.