NTSB Reports on Enbridge Kalamazoo Rupture

Among the conclusions reached by the National Transportation Safety Board (NTSB) in its review of the Enbridge Pipelines rupture near the Kalamazoo River in Michigan in July, 2010 are:

• The Line 6B segment ruptured under normal operating pressure due to corrosion fatigue cracks that grew and coalesced from multiple stress corrosion cracks, which had initiated in areas of external corrosion beneath the disbonded polyethylene tape coating;
• Enbridge's delayed reporting of the "discovery of the condition" by more than 460 days indicates that Enbridge's interpretation of the current regulation delayed the repair of the pipeline;
• 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;
• PII Pipeline Solutions' analysis of the 2005 in-line inspection data for the Line 6B segment that ruptured mischaracterized crack defects, which resulted in Enbridge not evaluating them as crack-field defects;
• The ineffective performance of control centre staff led them to misinterpret the rupture as a column separation, which led them to attempt two subsequent startups of the line;
• Although Enbridge had procedures that required a pipeline shutdown after 10 minutes of uncertain operational status, Enbridge control centre staff had developed a culture that accepted not adhering to the procedures;
• Had Enbridge operated an effective public awareness program, local emergency response agencies would have been better prepared to respond to early indications of the rupture and may have been able to locate the crude oil and notify Enbridge before control centre staff tried to start the line;
• Had Enbridge implemented effective oil containment measures for fast-flowing waters, the amount of oil that reached Talmadge Creek and the Kalamazoo River could have been reduced;
• Enbridge's failure to exercise effective oversight of pipeline integrity and control centre operations, implement an effective public awareness program, and implement an adequate postaccident response were organizational failures that resulted in the accidenct and increased its severity.

The NTSB also commented that, "contributing to the accident was the Pipeline and Hazardous Materials Safety Administration's (PHMSA) weak regulation for assessing and repairing crack indications, as well as PHMSA's ineffective oversight of pipeline integrity management programs, control center procedures, and public awareness."