Abstract: At approximately 5:30 p.m. on November 1, 2007, Employee #1, of Midwest Boring & Underground, Inc., was assisting another company with replacing a sump pump in an underground lift station which collected draining and leached water from a construction debris landfill. Three employees of the other company entered the lift station and were overcome by exposure to hydrogen sulfide gas. Employee #1 entered the lift station to assist or rescue the three workers when he, too, was overcome. Employee #1 was killed. Rescue services arrived at the scene and performed air quality monitoring, which revealed that all four workers were exposed to concentrations of up to 200 ppm of hydrogen sulfide gas. The lift station was determined to be a permit-required confined space. The other company, which was the host employer, had not evaluated the lift station to determine whether it was a permit-required space. Neither employee had developed and implemented a written permit space program.