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PHMSA Proposes $3.7 million fine for Enbridge Spill in Michigan in 2010
The report then faults PHMSA for failing "to pursue findings from previous inspections and did not require Enbridge Incorporated (Enbridge) to excavate pipe segments with injurious crack defects."
Enbridge clearly made numerous mistakes before and after the accident. The NTSB said Enbridge's integrity management program was inadequate because it did not consider the following: a sufficient margin of safety, appropriate wall thickness, tool tolerances, use of a continuous reassessment approach to incorporate lessons learned, the effects of corrosion on crack depth sizing, and accelerated crack growth rates due to corrosion fatigue on corroded pipe with a failed coating.
But again, underlining the inadequacy of federal law, as it does in a number of instances, the NTSB cites the absence of a "uniform and systematic approach in evaluating data for various types of in-line inspection tools" which is "necessary to determine the effect of the interaction of various threats to a pipeline." That raises the question as to whether the PHMSA rules on risk assessment within IM programs are adequate to prevent the kinds of accidents that happened in Michigan.
The NTSB also cited a list of control room inadequacies, including a lack of training of personnel leaving them unable to correctly identify the cause of the Material Balance System (MBS) alarms. "Enbridge's control center staff placed a greater emphasis on the MBS analyst's flawed interpretation of the leak detection system's alarms than it did on reliable indications of a leak, such as zero pressure, despite known limitations of the leak detection system. Enbridge control center staff misinterpreted the absence of external notifications as evidence that Line 6B had not ruptured."