A ROOF FALL MEASURING 20FT W, BY 25FT LONG BY 10FT HIGH WAS ENC0UNTERED AT XCUT 5 IN THE OLD 1 LEFT TAIL GATE SECTION DURING A PRESHIFT EXAMINATION OF THIS AREA. THE FALL HAD HAPPEDNED IN AN INTERSECTION AND WAS BLOCKING THE SECONDARY ESCAPEWAY ALL EFFECTED PERSONNEL WERE RMEOVED FROM THE AREA. THE ESCAPEWAY WAS REROUTED & WORK RESUMED