Abstract: Employees #1 and #2 had pumped water out of an approximately 30 ft deep manhole by lowering a gasoline engine-powered pump into the space. After approximately 2 hours and 30 minutes, the employees removed the equipment with a rope and left the manhole lid off so that the wind could disperse some of the visible smoke and vapors. After several minutes, the employees placed the lid back on the manhole. Approximately 17 hours later, Employee #1 entered the manhole and checked the water level at the bottom of the manhole by counting the number of rungs on the fixed ladder that were submerged underwater. Employee #1 was overcome by the toxic atmosphere. For some reason, Employee #2 entered the hole. Several minutes later, both employees were found submerged in 3 to 4 ft of water. They were pronounced dead shortly afterwards. The air quality testing that was performed approximately 24 hours after the accident indicated that carbon monoxide levels exceeded 500 parts per million. Employees #1 and #2 were not trained in hazard recognition and evaluation of confined spaces.