A 2010 pipeline rupture that dumped nearly a million gallons of oil into a Michigan waterway was blamed on operator negligence at a government hearing Tuesday. At the opening session of a hearing on the spill, National Transportation Safety Board head Deborah A.P. Hersman said Enbridge Energy Partners of Houston and operators of the pipeline detected the defect that led to the 2005 accident and failed to fix it, the Detroit Free press reported Tuesday. In July 2010 a 30-inch pipeline broke and more than 800,000 gallons of oil, and possibly as much as a million gallons, spilled into Talmadge Creek near Marshall. Last week federal regulators proposed a $3.7 million penalty against Enbridge, the newspaper said. \"Pipeline operators are required to have an integrity management program, which continually addresses the safety risk on their pipelines. In 2005 Enbridge detected the very defect that led to this failure. Yet for five years they did nothing to address the corrosion or cracking at the rupture site,\" Hersman said.