Abstract: EMPLOYEE #1 WAS PREPARING TO PATCH A 3/8 INCH HOLE ON THE AFT BULKHEAD IN THE CARGO COMPARTMENT OF A 31 FOOT BY 61 FOOT LASH BARGE. THE AFT BULKHEAD HAD A 9 FOOT BY 12 FOOT BY 31 FOOT STRUCTURAL VOID. HE WAS USING A MILLER 250 DIALARC AC/DC WELDING MACHINE. EMPLOYEE #2 HAD JUST ENTERED THE CARGO COMPARTMENT TO RETRIEVE A WASH-DOWN HOSE HE HAD BEEN USING EARLIER. WHEN EMPLOYEE #1 STRUCK AN ARC TO BEGIN WELDING, AN EXPLOSION OCCURRED. BOTH EMPLOYEES DIED FROM MASSIVE HEAD INJURIES. THE STRUCTURAL VOID (BULKHEAD) HAD NOT BEEN TESTED FOR THE PRESENCE OF FLAMMABLE VAPORS PRIOR TO THE EXPLOSION. THE BARGE WAS EMPTY OF CARGO, AND THE HATCH COVERS HAD BEEN REMOVED.