Incomplete and unsafe abandonment of natural gas well flow lines, as well as local rules that allowed homes to be built on or adjacent to a former production field with incomplete documentation contributed to two deaths in April 2017 when a home exploded in Firestone, CO, according to the National Transportation Safety Board (NTSB).

In a report issued Tuesday, NTSB determined that the probable cause of the fatal explosion was ignited fugitive natural gas that had migrated from an abandoned Anadarko Petroleum Corp. well,  the Coors V6-14Ji, “through a pipe that was not abandoned” by operator Patina Oil and Gas Corp. The line “most likely was severed in 2015” when the home that was destroyed in the explosion was built.

A contributing factor in the Weld County incident was "the approval by local authorities to allow occupied structures to be built on land adjacent to or previously part of oil and gas production fields without complete documentation” on the location and status of its gathering system pipelines.

Weld County spokesperson Jennifer Finch said county codes did not apply to the home in Firestone since the housing development is within city boundaries. However "development in unincorporated Weld County, almost all of which is zoned agriculture, requires an occupied structure to be at least 200 feet from any tank and 150 feet from any oil and gas wellhead, or 25 feet from any plugged or abandoned well."

Three severed pipelines were found beneath a concrete pad about six feet from the home's foundation: a one-inch-diameter polyethylene (PE) line, and two, two-inch-diameter steel lines, all related to the well south and west of the home. One of the steel lines had previously been linked to the well, but NTSB concluded that gas likely leaked from the well and traveled through the PE line to the house.

"Information gathered during the investigation found that the most likely source of the gas that fueled the explosion was from the Coors well, and the pathway for the gas to reach the residence was the one-inch PE line," NTSB noted.

The devastating tragedy was called a pivotal moment for the oil and gas industry because the state and the industry are safer as a result of steps taken by the Colorado Oil and Gas Conservation Commission.

In the aftermath of the tragedy, former Gov. John Hickenlooper ordered an investigation of the state's 120,000 flowlines. A bipartisan effort strengthened excavation laws and has  resulted in a rulemaking now underway by COGCC.

"The accident was devastating, but it set into motion several positive changes, and I can say with confidence that this industry is safer today as a result, and so are Coloradans," said Colorado Oil and Gas Association CEO Haley. "We have the most comprehensive flowline rules in the country."