A NON INJURY ROOF FALL OCCURRED ON 16 NORTH START LINE 25' IN BY #3 ENTRY FOR 46 FEET STOPPING 15' BEFORE THE FIRST X-CUT. THE AREA WAS BEING WIDENED FOR THE STARTLINE AND WAS BEING SPOT BOL TED AND TRUSSES WERE BEING INSTALLED WHEN THE ROOF OCCURRED. THE FALL MEASURED 46' LONG 30' WIDEAND 10-12' HIGH.