AN UNINTENTIONAL FALL OF ROOF WAS DISCOVERED ON THE 9-LEFT SECTION AT APPROX. 0630 ON 7-19. THE FALL WAS DISCOVERED IN THE 2 ENTRY AT THE INTERSECTION OF SPAD 18425. FALL MEASURES APPROX. 20' LONG X 20' WIDE X 8-10' IN HEIGHT. AREA WAS SUPPORTED WITH 5' TENSION REBAR BOLTS. NO EQUIPMENT CAUGHT--NO INJURIES. FALL WILL BE CLEANED UP.