Abstract: The employer was engaged in a water well service operation using a portable drilling rig. The employer was air-developing a water well borehole to eliminate sediment build-up and enhance the water recovery from the underground formation. This procedure consisted of using compressed air as a jet to wash away the sediment and circulate the fluids back to the ground surface. A contained discharge system consisting of PVC sewer pipe was installed to divert the fluids at the surface level. The discharge pipe components were wedged together but were not otherwise secured to prevent separation. Employee #1 was collecting rock screen samples at the discharge end when pressure began building up in the drill stem. As the employee began moving away from the pipeline, a sudden release of air and water pressure was fed into the PVC pipe, causing the pipe joints to separate. Employee #1 was struck in the chest by two sections of water-filled pipe joints as he attempted to evacuate the area. He died of internal injuries.