Abstract: Employees #1 and #2 were preparing a hopper barge on a marine railway in a shipyard for its biennial Coast Guard inspection. While opening up the tank's manhole covers, Employee #1 apparently unscrewed the crossbar on the bottom of the cover all the way and it fell to the bottom of the tank. Rust and scale in the sealed compartment resulted in an oxygen deficient atmosphere, and when Employee #1 went down to retrieve the crossbar he died of asphyxia. Employee #2, who apparently went down to help Employee #1, also died of asphyxia. Employee #3, who was part of the rescue team, experienced chest pains and was kept at the hospital for observation for possible hyperventilation. There were no eyewitnesses to the accident.