Exxon's 22-Foot Rupture Illustrates Tremendous Operating Pressure of Oil Pipelines

The rupture in the ExxonMobil pipeline that sent a river of oil through a suburban neighborhood in Mayflower, Ark. is now known to be 22 feet long and 2 inches wide. That's almost four times larger than the six-foot pipeline tear that sent more than one million gallons of Canadian dilbit into Michigan's Kalamazoo River in 2010, the worst accident of its kind in U.S. history.

The size and speed of the release through a long opening, thin as a mail slot, shines a spotlight on just how quickly oil pipeline accidents can turn into catastrophes. Between 200,000 and 420,000 gallons of heavy oil spewed out of the 65-year-old pipeline without warning on March 29, Good Friday afternoon, forcing the evacuation of 22 suburban homes.

Few Americans realize how much pressure is needed to operate a pipeline like the Pegasus, which moves more than 90,000 barrels a day of crude across four states, from Illinois to Texas. That's almost four million gallons of heavy oil being pushed over an 850-mile distance in a single day. 

When a rupture occurs, so much force is released that large amounts of oil can pour through the breach in minutes.

"People just don't gather how high these things can go," said Richard Kuprewicz, president of the pipeline consulting firm Accufacts Inc. "For the average person, they're just exotic pressures." But if pipeline operators drop their guard, he said, pipelines "can be highly destructive."

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