Abstract: On August 27, 2002, Employee #1 and a coworker were installing a new gate and removing the old one from a stand box filled with manure water from a manure pond. The dairy owner ran the pump to draw water out of the box and reduce the water level below the opening port of the gate. When the water level had been lowered, Employee #1 entered the box, removed the old gate and cleaned the old sealing mortar from around the opening. He and the coworker then lowered the new gate into the box. Employee #1 reentered the box to position the gate, while the coworker and one of the dairy owners stood outside the box and held onto the gate from above. They were watching Employee #1 when he suddenly rolled onto his right side and landed, back down, in the water, with his head submerged. The coworker entered the box to rescue Employee #1, passed out momentarily, regained consciousness, and then climbed out of the box under his own power. Emergency responders were called, and Employee #1 was extricated from the stand box. He was transported to the hospital, where he was pronounced dead of the inhalation of hydrogen sulfide and possibly methane. Hydrogen sulfide levels were later measured at 218 PPM under conditions approximating those of the accident.