Abstract: At approximately 1:00 p.m. on October 22, 2014, Employee #1 was adjusting process piping at a waste water treatment plant that had been installed when he encountered a leak. Employee #1 exited Pump Room #2 to notify Water Utilities of the leak. Employee #1 returned to Pump Room #2 to try and close the main valve from the primary clarifier to isolate the flow from the leak. After entering Pump Room #2, Employee #1 was overcome with hydrogen sulfide and unable to exit the room. Upon hearing that Employee #1 had fallen, Employee #2 then entered the room to retrieve Employee #1. Both employees were unable to exit the room and were killed from over exposure to hydrogen sulfide.