Web exclusive: Explosion threat leads to evacuation, road closure in Sunset Hills

Staff report

Authorities last week evacuated a handful of Sunset Hills residents and temporarily shut down a section of South Lindbergh Boulevard due to the possibility of an explosion.

Helium building up inside an MRI machine at SSM Imaging, 3825 S. Lindbergh Blvd., that was damaged in a tornado on New Year’s Eve posed a plausible but unlikely threat of an explosion, officials said.

Residents living on Court Drive near SSM Imaging were evacuated last Thursday evening, and a nearby section of South Lindbergh Boulevard was closed Thursday evening through Friday morning, when officials determined the threat was over.

Typically, helium slowly is vented from an MRI machine over a period of time, normally 96 hours, Sunset Hills Mayor Nolan said.

“Two issues arose,” he said of the SSM machine. “No. 1, it had been unplugged. It had not had power since the prior Friday (Dec. 31). So was helium escaping already? … No. 2, the vent pipe on the top of the building was folded over on itself …”

Noting helium is not a flammable gas, Nolan said, “We’re not talking about an explosion with lots of flames and fire. What we’re talking about is if the pressure builds up within the vent pipe far enough and then backs into the unit itself, we’re talking projectile …”

On Friday, workers removed the top of the vent pipe and Nolan said, “It was decided that we would just vent the gas … Except they couldn’t get to the MRI. So they knocked a hole in the back of building, put two technicians into the room with the MRI, turned the valve and let the gas (release) …”

Nolan said he later wanted an explanation of why it took nearly a week to learn the MRI machine posed a danger to the public. The SSM Imaging Center building inspected by the county and was “red tagged,” he said, meaning it was condemned and no one could enter it.

“So according to SSM, the SSM people got there on Monday (Jan. 3), looked at it and couldn’t go into the building. They called their insurance people, who got there on Tuesday (Jan. 4), who looked at the building and said we’re going to need a structural engineer to come in before we try to get to the MRI (machine),” Nolan said, noting a structural engineer examined the building Jan. 5 and “determined that it would be OK to get people in there. At which point, they went to GE and said: OK, we need you guys to start decommissioning the MRI.

“And that’s when they pulled out the book, looked at the possibility that pressure could build up on that vent pipe and notified the (Mehlville) fire chief, Tim White. I don’t think SSM had any intimate knowledge or any knowledge that that potential was there. And the potential was not in the MRI itself. It was pressure building up in the exhaust system …”

White told the Call the evacuation and road closure were necessary even though an explosion was unlikely.

“It was a really tough decision. I didn’t sleep all night thinking about it. I wanted to get all of those people back to where they belong,” White said. “I was just happy that it had a successful conclusion and that the public was safe … I just want the public to know that it was in their best interest. It was an inconvenience, but unfortunately a necessary inconvenience.”