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Enbridge concludes investigation into fatal pipeline explosion

Enbridge Energy has concluded its investigation into the Nov. 28, 2007, explosion that killed two Superior(Wis.)-based workers on one of its pipelines.

Steve Arnovich, 35, and David Mussatti Jr., 27, both of Superior, Wis., were working at the site of the explosion near the northwestern Minnesota community of Clearbrook when they were killed.

The federal office of pipeline safety, which is also investigating the explosion, has not released a final version of its own official report. A spokesman couldn't be reached Thursday night for information on when the office would conclude its investigation.

Enbridge's investigation found that a length of exposed pipeline was positioned at a degree that, when coupled with its engineered bend, resulted in insufficient anchoring, according to Enbridge spokeswoman Denise Hamsher.

When oil was re-injected into the pipe, that lead to a failure of the couplings that were holding the segments of pipe together before they were welded.

Oil was emitted from the coupling sites as a mist, which was then likely ignited by an open-flame heater that had been placed at the scene to warm the workers.

"This is not the fault of any employee or crew," Hamsher said.

Arnovich and Mussatti were most likely in the cab of a truck on the work site when the explosion occurred, Hamsher said. They apparently tried to flee the scene.

Hamsher said their deaths are the only employee deaths in the U.S. the company has experienced since it was founded in 1949.

Hamsher said Enbridge's investigation took fivemonths because Enbridge re-created the Clearbrook pipeline situation in a lab with the help of an outside engineering firm. The company studied the simulation to determine how the explosion happened.

"We realize that five months is a long time for an investigation, but we really wanted to take a look at this," she said.

Vicki Mussatti, David Mussatti Jr.'s mother, said she was satisfied with the company's explanation of what happened.

"Three generations of my family worked for Enbridge," she said Thursday evening from her home in Bessemer, Mich. "They've been very good to my family."

Elaine Arnovich, Steve Arnovich's mother, declined to comment Thursday night.

In February, federal office of pipeline safety spokesman Damon Hill said preliminary findings made it appear as though improper procedures were followed at the repair site.

Hamsher said Enbridge was following procedure, but will change its written procedures, employee training and repair equipment to prevent similar accidents from happening.

She said the company will probably continue using the open-flame heaters used at the accident site, but will probably position them differently.

The explosion occurred where the Enbridge pipeline crosses Clearwater County Road 3, about a mile south of Clearbrook, about 25 miles northwest of Bemidji.

The pipe was closed after the accident and reopened to pre-accident operating pressure Dec. 3, 2007.