Abstract: At approximately 8:00 p.m. on April 24, 2009, Employee #1 was assisting a coworker, a welder, with the installation of a new flange at a geothermal energy generation site in Calipatria, CA. The task was to cut a hole into an existing injection well pipe and weld the new flange upon it. A few days before, the pipe had been emptied of fluid and closed by valves on either side of the weld location. The hole was cut by the welder, then the metal and brine scale buildup behind it were removed and the edge of the cut section was smoothed with a grinder. The employee was then instructed to hold the flange over the hole to level it for the welder. As the welder struck the flange with the arc, an explosion occurred and ejected the flange. It struck Employee #1 in the chest with great force, causing blunt force injuries and third degree burns. The burns to his chest encompass approximately 6 inches in diameter. He was transported to Pioneers Memorial Hospital in Brawley, CA, where he underwent burn treatment and was hospitalized.