Investigation into Thursday’s Minneapolis gas blast under way

Published 12:20 pm Saturday, March 19, 2011

MINNEAPOLIS (AP) — Engineers dug up a 20-foot section of natural gas transmission line Friday as part of the investigation into what caused an explosion that sent flames high into the air and scorched parked cars.

State Office of Pipeline Safety spokeswoman Kristine Chapin said workers spent the night pumping water out of the hole in 60th street near Interstate 35W where the 20-inch gas line ignited about 8 a.m. Thursday, prompting the evacuation of an eight-block area for several hours. There were no injuries and only minimal damage to buildings.

She said the state would not release copies of its inspection reports of the line while the investigation was pending. Becca Virden, a spokeswoman for CenterPoint Energy, said the company would also not release its own inspection records.

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Virden said the 20-foot section of pipeline will be sent, along with other material from the scene, to a laboratory for analysis.

She said crews would then make temporary repairs so the hole could be filled and traffic could resume driving on 60th Street, but that could take a while. Because of the redundant design of the natural gas system in the area, no customers lost gas service during the fire or the repairs, she said.

Virden said no CenterPoint crews were working in the area before the explosion, ruling out one possible cause.

But there are many other possibilities, said Rick Kuprewicz, president of Washington-based Accufacts, a consulting company that specializes on pipeline operations and design in heavily populated area. He said he has investigated over 1,000 similar events over the past 40 years.

He said it was impossible to point to a single common cause for natural gas line explosions. “The only thing is that they are not accidents,” he said. “An accident is a random event.”

Instead, it’s usually multiple failures that somehow became linked and lead to disaster. Kuprewicz said factors including shifting ground, metal fatigue, bad welds, corrosion, damage by third parties and operator error.

Kuprewicz said compared to recent fatal explosions in near San Francisco and Allentown, Penn., Minneapolis was lucky.

“The good news is that no one died,” he said. “We still need to understand if this is a rare event or if there’s more here.”