State report on deadly Gatesville hospital explosion released

The explosion in June that killed three workers and injured 13 others at a physical plant under construction at Coryell Memorial Hospital in Gatesville hospital resulted from a large pocket of natural gas that had flowed from disconnected gas lines into the building, according to a State Fire Marshal’s Office report that says the investigation is now closed.

“Although the specific ignition source was not identified during the investigation, there was no evidence to suggest this was the result of an intentional act or of natural causes. Evidence tended to suggest this was a construction accident," the report concludes.

The natural gas that accumulated in the physical’s plant boiler room and larger mechanical room exploded at around 2:20 p.m. on June 26.

The report says it appears a gas-air mixture ignited in the boiler room and the resulting fire “propagated to the mechanical room where a larger pocket of fuel gas was located.”

“The large explosion occurred when the propagating flame front reached the large pocket of gas at the south end of the mechanical room,” the report says.

An examination of the three water heater units in the mechanical room “revealed that the natural gas pipe supplying them had been disconnected at the coupling to the north and south units,” the report says.

The couplings did not show any sign of forceful separation, the report says, and investigators determined they were disconnected before the explosion.

“The valves on both pipes were open, allowing natural gas to flow freely into the mechanical room,” the report says.

“Interviews with construction employees revealed that plumbers were bleeding air off of the natural gas lines. This information corroborated the open valves and disconnected gas lines observed during the scene investigation,” the report says.

“Witnesses denied smelling natural gas in the structure,” the report says.

Investigators determined the most probable location of a natural gas leak was the open valves and disconnected couplings, the report says.

Investigators were unable to determine the source of ignition, but identified several potential sources including two scissor lifts, fluorescent light fixtures, there HVAC units, cellphones, a BIC lighter, a striker for a welding torch, battery-powered tools, and water and chiller pumps.

Atmos responded to the scene after the explosion and shut off natural gas to the hospital.

Atmos removed the gas meters, but retained them, the report says.

They were returned to the hospital and reinstalled for purposes of investigation.

“A mercaptan test conducted during the scene examination indicated the odorant was detectable at the meter.”