Federal investigators release initial findings on Coolidge gas explosion

The National Transportation Safety Board on Wednesday released its preliminary report on a gas line explosion in Coolidge that destroyed a home and killed a man and his 14-year-old daughter.

Related: Father, daughter killed and woman severely burned after Coolidge gas line explosion

NTSB investigators said a natural gas pipeline ruptured around 5:30 a.m. on Aug. 15, about 120 yards away from a family’s rural farmhouse on the outskirts of Coolidge, a small Pinal County city located south of Phoenix.

Authorities said the explosion was heard for miles and the resulting fire burned for more than 2 ½ hours, and according to investigators, a 46-foot section of the pipeline was ejected during the explosion.

The NTSB said the fractured and unaffected portions of the pipeline still were undergoing analysis and testing and the agency’s investigation of the explosion was ongoing.

Pipeline expert weighs in

As the investigation continues, pipeline expert Don Deaver, who is working on the case, is weighing in.

"What happened was the gas pipe broke into two pieces, and there was a 40 foot section that was thrown away, so they were two sections shooting gas out, going up and out at the speed of sound, 1,400 feet per second., and all of that gas was coming up and forming a big cloud, so to speak, natural gas that get bigger and bigger and bigger. With time, it moved towards the house," said Deaver, who is with Deatech Consulting Company.

Right before the explosion, the NTSB said the gas pressure of the pipeline was below the maximum allowed operating pressure.

Deaver said the pipeline was not designed for natural gas service, and according to the NTSB report, the pipeline was originally installed in 1985, and had previously been transporting crude oil. Authorities said the pipeline was converted to natural gas service about 20 years ago, and acquired by Kinder Morgan Inc. in 2012.

"Natural gas is much more dangerous than crude oil. Crude oil is an environmental concern, but this pipeline was not likely to be designed for this rupture propagation and control, and that’s the reason why you had this big hole, and you had a huge section thrown out, 46 feet out," said Deaver.

We have reached out to Kinder Morgan for comment, but officials with the company have yet to respond.

The Associated Press (AP) contributed to this report.

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