Abstract: In August 10, 2004, Employees #1, 2, 3, and 4 were repairing the concrete walls of a diversion box at a wastewater treatment plant. The diversion box was a 10-ft-by-14-ft deep concrete box in the ground that diverted water to the pump station or to a clarifying pond if the pump station fails. At the end of the day all equipment was dismantled and put into the trucks. The diversion box was no longer being ventilated. Employee #1 went into the box without any respiratory protection or a harness and lifeline. He collapsed and was later pronounced dead. Employee #2 went in without respiratory protection or a harness and lifeline to rescue Employee #1, and collapsed. Employees #3 and #4 at different times donned respirators and put a harness on Employee #2 and hoisted him out of the box with a truck hoist. Employees #3 and 4 were unable to get the harness on Employee #1. Mean while Employee #3 went to the operations building to get emergency help. Two city employees were summoned from the maintenance building. The city workers hooked the ventilation back up and put the ventilation hose down in the box. Meanwhile, the fire department arrived and took over the recovery of Employee #1's body. Employee #2 was transported to the hospital and treated for his injuries. Both Employees #1 and 2 were overcome by hydrogen sulfide from the bacteriologic degradation of wastewater.