Abstract: AT APPROXIMATELY 10:30 A.M. ON NOVEMBER 29, 1991, EMPLOYEE #1, A FLOORMAN ON A GAS DRILLING RIG, WAS CLEANING THE BACKSIDE OF THE DRAWWORKS. HE WAS STANDING ON A SECTION OF THE RIG'S MAIN FLOOR THAT HAD NOT BEEN BOLTED OR OTHERWISE SECURED DURING "RIG UP." THIS SECTION OF THE FLOOR HAD A GUARDRAIL PERMANENTLY ATTACHED. FOUR WET COCOA MATS, WEIGHING APPROXIMATELY 80 TO 120 POUNDS EACH, HAD BEEN HUNG ON THE GUARDRAIL TO DRY. AT SOME POINT IN THE CLEANING OPERATION, EMPLOYEE #1 CLIMBED UP ON THE GUARDRAIL SO HE COULD REACH THE TOP OF THE DRAWWORKS. THE COMBINED WEIGHT OF EMPLOYEE #1 AND THE WET COCOA MATS CAUSED THE UNSECURED SECTION OF FLOOR TO TILT BACKWARDS, WHICH CREATED AN OPENING IN THE FLOOR OF APPROXIMATELY 17 INCHES BY 12 FEET 5 INCHES. EMPLOYEE #1 LOST HIS BALANCE AND FELL THROUGH THE OPENING. HE FELL APPROXIMATELY 20 FEET BEFORE STRIKING A STEAM HEATER LOCATED ON THE RIG SUBFLOOR, WHERE HE SUSTAINED FATAL INJURIES TO THE HEART AND LUNGS.