Abstract: Employees #1 and #2, both riggers, were capping a sulfur well in a shallow bay. They were working from the deck of a barge equipped with a crane with a clamshell bucket. The employees dug around the 10 inch diameter well casing, then set a 10 foot diameter by 20 foot long caisson around the well head. Standard procedures required them to cut off the 10 inch casing approximately 15 feet below the line, then weld a circular plate over the end. Employee #1 went into the caisson to wrap a sling around the pipe after they had cut it off with a pneumatic saw. He was overcome by hydrogen sulfide gas. Employee #2 entered the caisson to rescue Employee #1, and was overcome also. Both were killed. Neither man was wearing a respirator.