NTSB report: Enbridge's response to Michigan oil spill was 'poor' The July 2010 oil spill near Marshall, Mich., though little-known by the public, was widely considered one of the worst inland oil spills in U.S. history. Now, the National Transportation Safety Board has released the results of a two-year investigation into the spill -- and Enbridge Energy Partners takes it on the chin. For starters, NTSB investigators said, Enbridge knew that its pipeline had been damaged five years before the spill. When the spill actually occurred, investigators said, the company's response was, in short, "poor." A break in the company's pipeline released about 1 million gallons of oil into a marsh that then seeped into the Kalamazoo River, closing down more than 30 miles for a two-year cleanup. Though severe, the spill was overshadowed by that summer's colossal BP oil spill in the Gulf of Mexico. "When we were examining Enbridge's poor handling to their response to this rupture, you can't help but think about the Keystone Kops," NTSB Chairwoman Debbie Hersman said Tuesday morning, according to Postmedia News. Previous NTSB investigative materials showed that company employees were unaware the pipe had broken open and was spilling oil, mistaking repeated alarms at a control center for a "column separation" instead of a spill. Rather, company employees thought they needed to pump more oil through the pipeline to get the flow started again rather than shutting the whole thing altogether. Shift changes at Enbridge added to the confusion as the leak stretched on for hours before it was discovered, with Marshall residents repeatedly reporting smelling a massive gas leak, many unaware a pipeline ran near the town. "Operator B2 [an Enbridge employee] said that it seemed as if there was something wrong about the situation," the NTSB recounted in one of its investigative findings released in May. "Operator B2 said to Operator B1 "whatever, we're going home and will be off for [a] few days." " Hersman, the NTSB head, also blamed weak regulation for allowing the company to exploit weaknesses in safety protocol for its pipelines. According to the Detroit Free Press, she said the federal Pipeline and Hazardous Materials Safety Administration "was ineffective in overseeing Enbridge's pipeline integrity management programs." Enbridge's latest quarterly filing with Canadian regulators - which euphemized the spill, calling it a "release" - said the company expects to pay for cleaning up underwater oil and further assessments and restoration of the area. As of March 31, the company estimated the spill cost at $765 million; 25 lawsuits have been filed against the company in federal and state courts. Arctic drilling: Groups challenge Shell oil-spill response plans Baby beluga whale dies after a rare and frantic Alaska rescue