ExxonMobil has released information concerning the cause of a March 29 rupture in its Pegasus oil pipeline, which flooded a Mayflower, Ark., neighborhood and surrounding woodlands with more than a million gallons of dense Canadian tar sands oil.
According to the oil company, an independent metallurgical analysis of the 70-year-old pipeline determined that original manufacturing defects formed the root cause of its failure. Those defects included small hook cracks near the seam where the breach occurred.
“Additional contributing factors include atypical pipe properties, such as extremely low impact toughness and elongation properties across the … seam,” ExxonMobil said in a statement about the analysis.
ExxonMobil also said that neither external nor internal corrosion were found to be a contributing factor in the oil spill, which displaced dozens of families and sickened area residents.
Last month, the company reported that it had recovered all of the visible oil from the spill site, but that it would be several months before the cleanup is completed. Much of the oil went into a cove that feeds Lake Conway, which serves as a source of drinking water for the area. And, as the July 2010 Enbridge oil spill in Michigan demonstrated, when Canadian tar sands oil is spilled, it can be almost impossible to clean up.
Conventional oil, such as the crude that spilled during BP’s Deepwater Horizon disaster in the Gulf of Mexico, costs about $2,000 per barrel to clean up. But Canadian tar-sands dilbit is extremely dense and highly toxic and costs about $29,000 per barrel on average to clean up.
Arkansas Attorney General Dustin McDaniel, who along with the Environmental Protection Agency is suing ExxonMobil over the spill, said that that there is no distinction between the contaminated cove and the lake. The joint Arkansas-U.S. lawsuit seeks $45,000 per day in penalties to cover spill damages.
The spill caused the evacuation of 22 homes, sickened several Mayflower residents, and killed hundreds of animals.
In addition to the joint Arkansas-U.S. lawsuit, ExxonMobil faces a major class-action lawsuit. That complaint accuses the oil giant of willful negligence under Arkansas state law, and says the Pegasus pipeline was designed to haul light crude, not heavy Canadian dilbit. According to a report by DeSmogBlog published in the Huffington Post, that lawsuit “also reveals for the first time that the spill was just the biggest of 13 other spills preceding it, meaning it was not just a spill out of the blue.”