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NTSB: Movement of gas meter by unqualified workers 'probable cause' of Minnehaha Academy explosion

Chopper 5 captured video of Minnehaha Academy after the explosion Photo: KSTP/ Chopper 5
Chopper 5 captured video of Minnehaha Academy after the explosion

Updated: December 03, 2019 10:41 PM

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The National Transportation Safety Board (NTSB) on Tuesday released its final report on the Aug. 2, 2017, explosion at Minnehaha Academy's upper campus that killed two people and injured nine others.

In its report, the NTSB said the probable cause of the explosion occurred, "when a pipefitting crew disassembled piping upstream of a gas service meter." The report also stated the lack of documentation that established the scope of work that was expected to be performed was a contributing factor.

The NTSB also reported the two contractors working on the piping at the school were not qualified to work on that section of piping. The contractors were a father and son duo working for Master Mechanical, LLC who were contracted by CenterPoint Energy.

The NTSB said while the foreman overseeing the work was licensed and trained to meet state and local requirements, he was not qualified to work on Department of Transportation jurisdictional piping, which included the section of piping they were working on.

The other contractor working that day was also not qualified to work on jurisdictional piping.

According to the preliminary report, "two workers were installing new piping to support the relocation of gas meters from the basement of the building to the outside. Two new meters mounted on a wall were ready for the new piping to be connected. While workers were removing the existing pipeline, a full-flow natural gas line at pressure was opened." The workers were unable to mitigate the release of the gas, so they evacuated the area, according to the NTSB.

The report goes on to say the school maintenance worker heard and smelled the gas and went to the source in the basement meter room. He exited and made an announcement over his hand-held radio, saying there was gas in the building and everyone should evacuate immediately.

The report states after making that announcement, he raced up the stairs to search for occupants. The building exploded less than a minute later.

The explosion killed two school employees — 47-year-old receptionist Ruth Berg and 82-year-old custodian John Carlson.

More than 14 lawsuits have been filed against CenterPoint and Master Mechanical Inc.

Michael Weiner an attorney for 14 of the plaintiffs told 5 EYEWITNESS NEWS that employees who survived the explosion suffered traumatic brain injuries, physical injuries and PTSD.

"The NTSB report confirms there was really extensive and egregious wrongful and unsafe conduct by both Master Mechanical and CenterPoint," he said.

Weiner told us there needs to be more supervision and training to make sure employees are qualified to do the work they're assigned in the future.

"It's pretty clear from the investigation this never should've happened, it took a lot of unsafe conduct by both Master Mechanical and CenterPoint to get to this explosion," he said. "It wasn't just one thing done wrong- it was many, many things done wrong leading up to him taking off the pipe without being absolutely certain that the gas was turned off."

Following the release of the NTSB report, CenterPoint Energy, who supplies gas to the school, issued a statement.

"CenterPoint Energy supported the NTSB's investigation to determine the cause of the explosion at Minnehaha Academy and identify safety recommendations. The overriding goal shared by everyone is the desire to prevent something similar from happening again, anywhere," a portion of the statement read. "CenterPoint Energy and its employees recognize and are committed to fulfilling their primary responsibility to operate and maintain a safe and reliable gas distribution system. Shortly after the accident, CenterPoint Energy, without waiting for the NTSB investigation to conclude, implemented improvements to its procedures with the goal of preventing an accident like this from ever happening again."

The company's full statement can be read here.

Master Mechanical released the following statement Tuesday:

"We appreciate the thorough investigation conducted by the National Transportation Safety Board (NTSB) and respect the findings contained in the board's final report.

Throughout this entire difficult time, we have cooperated fully with the NTSB.

We continue to keep in our thoughts all those impacted by the incident."

Minnehaha Academy also issued a statement regarding the report: 

"We appreciate the comprehensive work of the NTSB.  As the report makes clear, Minnehaha Academy has no culpability in this tragic event. Since this report relates to an open legal matter, we cannot comment further. This process is being guided by our attorney so that our team can focus its full attention on our students."

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