Abstract: At approximately 8:30 a.m. on June 15, 1990, Employee #1, a port captain at a work site at mile 167 on the Mississippi River near Donaldsonville, LA, was working with a small crew on the motor vessel "Mr. Fern." Another motor vessel, the "Gloria A" was docked alongside 6 to 8 ft away, depending on wave action. Employee #1 walked from the "Mr. Fern" onto the first deck of the "Gloria A," where he stood on a cover on top of a lube oil tank that was built into her hull. Metal sawing and burning work were in process on the second deck and front of "Mr. Fern," on the side facing Employee #1. Sparking occurred from the burning operation followed by a sudden flash and brief explosion in the "Gloria A" lube tank. The flash blew the cover off the tank and threw Employee #1 into the air and against the overhang of the second deck, inflicting internal injuries and fractures. Although he was not severely burned, Employee #1 died. There was no fire or explosion after the initial flash. The "Gloria A" sank in the river up to its wheelhouse. The exact cause of the explosion is not known. The lube tank was vented above deck on the outside of the "Gloria A" and the explosion may have been caused by a spark contacting tank vapors. Oxygen and LEL meter readings had been taken earlier on "Mr. Fern"; there was 21 1/2 percent oxygen and zero LEL.