ROOF FALL OCCURRED IN L/37 INTERSECTION, IMMEDIATE AREA OF FALL WAS THE SITE OF A SMALL ROCK FALL APPROX 2 YEARS AGO, THE ROOF WAS UNBOLTED, THEAREA SURROUNDING THE INTERSECTION WAS BEAMED AND DANGERED OFF. AREA OF FALL WAS APPROX 60' LONG BY 40' WIDE BY 20' HIGH.