Water conservation may have been factor in wastewater deaths
Water conservation efforts in Wichita Falls, combined with an increased volume of human waste being pumped into the sewer system, may have contributed to the elevated levels of hydrogen sulfide gas that killed two city workers in July.
Freese and Nicols Inc., a water management consulting firm with locations in Texas, Oklahoma and Georgia, was hired by the city to investigate what produced the poisonous gas that killed Daniel Arredondo and David Sheppard. The men were dispatched to the city's wastewater treatment plant on July 2 to repair a pipe valve that was leaking sewage in the city's basement.
Arredondo and Sheppard were found unconscious inside the plant shortly after beginning the repairs. Both died from their exposure.
Preliminary investigation showed that the men were not wearing protective breathing masks and air tanks when they were found by another city worker, though the men were wearing the gear when they began the work.
Since the incident, a city investigation has been unable to explain what caused the elevated levels of hydrogen sulfide gas inside the plant's basement, which was characterized by a facility administrator as being 'unusual.'
Now, according to documents provided to the Times Record News by the city, it appears that a conclusion may have been reached.
Freese and Nichols wrote in a memorandum to Public Works Director Russell Schreiber that the company had developed four theories as to what had caused the buildup of poison gas — it ruled out all but one.
The most likely conclusion, the consultant found, was that decreased water discharge into sewers, increased human waste and hot summer temperatures caused a proliferation of hydrogen-sulfide-producing bacteria in the city's wastewater collection system.
The bacteria feed on sludge in the wastewater system, reducing sulfur levels in the waste but producing hydrogen sulfide as a byproduct.
When Sheppard and Arredondo were found unconscious, hydrogen sulfide levels in the treatment plant were measured at 509 parts per million, well over the level considered to be deadly in humans.
The consultant also wrote that the depth of sludge storage areas inside 'clarifier' basins at the plant differs from that of some other municipalities', which may have allowed hydrogen sulfide-producing bacteria to become more concentrated than usual.
Freese and Nicols also ruled out three other theories about what may have caused the gas buildup, including one involving a construction contractor who now is the subject of a wrongful-death lawsuit brought by Arredondo's widow. The city is also a defendant in that lawsuit.