--
Two employees of a fertilizer company in Riga, Michigan, were assigned to install a new float valve in an old 35-foot deep cistern for a new 300-foot well. This cistern was covered with a concrete slab with entry through a covered manhole. The first worker entered the cistern and as he reached a plank platform six feet below the opening, he was instantly overcome and fell unconscious into the water below. The man on the surface immediately ran to the nearby plant for help. Several workmen responded and two of them entered the cistern to render aid. They met the fate of the first worker. A passerby who had been drawn to the scene by the crowd which had gathered was told by an excited bystander that several men in the cistern were drowning. Upon hearing this, he shouted, "I can swim, I can swim" and pulled away from a company employee who was trying to restrain him. Now there were four bodies in the well.
Shortly afterward the fire department arrived at the scene with proper rescue equipment. The fire chief entered the cistern wearing a self-contained breathing apparatus. After reaching the plank platform, he removed his face mask to shout instructions to those on the surface and he, too, was instantly overcome. All five persons died in the cistern.
Tests of the cistern atmosphere revealed that H2S in a concentration of about 1000 parts per million was present when the five deaths occurred. The water pumped up from the deep well contained dissolved hydrogen sulfide which was released in the unventilated cistern.