Exxon-Mobil lists "hook cracks" as a manufacturing defect leading to the rupture, but officials at Central Arkansas Water say that doesn't go far enough to explain how the rupture truly happened.
"They've identified contributing factors, but they have yet to be able to say what specific items led to the hook cracks and the atypical pipe properties leading to a rupture after being in the ground for 65 years," said John Tynan, public affairs for Central Arkansas Water.
But Aaron Stryk, Exxon-Mobil spokesperson, said the company doesn't need to specify an exact cause in their remediation plans.
"That's why we developed a plan that's designed to mitigate all of the threats associated with those potential mechanisms," said Stryk in a phone interview.
The oil company lists five potential hook crack "mechanisms" - one being "pressure cycle induced fatigue." But the report, just one sentence later says that other growth accelerators were analyzed and "pressure pulsations" were ruled out as a potential mechanism.
"Is it a causal factor or have they ruled it out," questioned Tynan. "That needs to be made clear and if it is a factor, clearly state it's a possible factor."
But what really irks Tynan and C.A.W. is on the next page of the report where Exxon makes this statement:
"If a significant number of pressure-reversal failures occur, EMPCo may decide to reduce the targeted test pressures in order to complete the testing in more efficient manner."
Central Arkansas Water believes that statement means Exxon-Mobil would prefer less-stringent testing for their pipelines. Stryk said it's the complete opposite.
"It's all having to do with ensuring that there's a consistent margin of safety," said Stryk, mentioning the statement referred to lowering pressure along the whole pipeline.
Stryk said the remediation plans that surfaced last week are not the final remedial work plans. He said they were still working closely with PHMSA to straighten it all out.