Preventable Errors Led to Pipeline Spill, Inquiry Finds Preventable safety blunders by the pipeline operator Enbridge and lax regulation led to the disastrous 2010 rupture and oil spill in the Kalamazoo River in Michigan, federal investigators reported on Tuesday. The pipeline spewed 843,000 gallons of highly polluting oil sands crude into the river, soiling 35 miles of wetlands and waterways and sickening 320 people and nearly 4,000 animals. The agency investigating the spill, the National Transportation Safety Board, faulted the understaffed Pipeline and Hazardous Materials Safety Administration, the federal agency that polices pipeline safety, for weak and ambiguous regulations that it said enabled the disaster. The spill forces the board to "ask hard questions of this vital industry," the board's chairwoman, Deborah A.P. Hersman. "With more than 2.5 million miles of pipeline running through this country - enough to circle the earth one hundred times - we have to ask, "Are these companies representative of others?" If the answer is yes, we can expect to be back here again discussing the same issues with a different company," she said. Ms. Hersman spoke before the agency's investigators presented their report at a meeting of the transportation safety board. Its members voted unanimously to accept the findings and 19 safety recommendations. Those include revising federal regulations on identifying and fixing crack defects, conducting a comprehensive inspection of Enbridge's pipeline management program and requiring operators to train first responders in best practices for responding to oil spills. Enbridge's chief executive, Patrick D. Daniel, said Tuesday in a statement: "We believe that the experienced personnel involved in the decisions made at the time of the release were trying to do the right thing. As with most such incidents, a series of unfortunate events and circumstances resulted in an outcome no one wanted. Investigators concluded that Enbridge did not incorporate all available information in its evaluations of the safety of pipelines. The defect that caused the rupture was misclassified in 2005 as a "crack-like feature." Corrosion and cracks overlapped in many areas, but this was not considered in evaluations, it said. If these factors and others had been considered, "it is likely that the pipe section could have been excavated, and the accident prevented," said one of the investigators, Matt Fox. He said that intervals between inspections were too long because Enbridge's evaluations of pipeline conditions were flawed. A confluence of missteps also characterized the operator's response to the accident, investigators said. Multiple alarms sounded after the rupture, but employees misinterpreted the problem, concluding that a huge bubble was blocking the flow of oil. Twice they restarted the pipeline flow, pumping more crude through the rupture. It took 17 hours and three shifts for Enbridge employees to act, but only after a worker for a local utility company identified the leak. Emergency responders did not have information about the routes of the pipelines, which might have helped locate the spill when residents began calling 911 complaining of strange smells. Enbridge's closest spill-response contractor was out of state, more than 10 hours away, and the company did not have enough equipment and resources handy to handle the spill, the inquiry found. And the company's spill response plan was inadequate, investigators concluded. Last month the pipeline safety agency levied a $3.7 million civil fine against Enbridge for the spill. But the agency itself was a target of sharp criticism from investigators. They said that its rules required pipeline operators to ensure they had enough resources available for a "worst case" spill but specified no minimum level of personnel or equipment so that operators could follow best practices. The pipeline safety agency also lacks enough staff members to review spill-response plans properly and fails to conduct onsite audits of response procedures, the report said. It is unlikely that Enbridge's plan got more than a cursory review, it said. "Delegating too much authority to the regulated to assess their own system risk and correct them is tantamount to the fox guarding the henhouse," Ms. Hersman said. Yet she said the board had found no conclusive evidence that the substance spilled, a particularly thick crude known as bitumen, played a role in causing the rupture. Nonetheless, the cleanup has cost more than $800 million so far and is still ongoing because of the difficulty of removing bitumen from the river and marshes. The oil, which has the consistency of peanut butter, still coats much the riverbed.