Contracted workers lacked crucial training and were unauthorized to carry out some of the tasks while moving a natural gas meter just before they set off the earthshaking blast at Minnehaha Academy in 2017 that killed two people and injured several others, according to newly released federal findings.
Along with its scrutiny of the work crew's credentials to do the work, the agency also pointed out secondary shortcomings by CenterPoint Energy in connection with the explosion, which occurred as the natural gas supplier and Eagan-based Master Mechanical Inc. (MMI) collaborated in moving meters from inside to outside the Upper Campus building on Aug. 2. School was out of session but 36 staff members and six students were present.
Nine people were wounded, and part-time custodian John F. Carlson, 82, and receptionist Ruth Berg, 47, were killed.
Instruction at the private school's 104-year-old building was relocated as demolition and rebuilding took place. Classes resumed at the campus in August.
The findings released Monday by the National Transportation Safety Board (NTSB) noted that the two-person crew's foreman lacked the proper licensing and training "to work on the covered tasks" associated with moving the utility's meters.
The "contract helper," the foreman's son, lacked any training for pipe fitter work, failed to complete the required CenterPoint Energy qualifications program and had just roughly eight months' tenure with MMI at the time of the blast, the NTSB added.
"The probable cause of the natural gas explosion … occurred when a pipe fitting crew disassembled piping upstream of a gas service meter" that was off-limits to the workers, the agency concluded.
Specifically, the MMI workers were not qualified or authorized to demolish piping or work on an existing meter, the NTSB said. It was during that work that a valve was opened, leading to the uncontrolled release of gas and the subsequent explosion.