WASHINGTON (Reuters) - Enbridge's massive oil pipeline spill in Michigan in 2010 was caused by a complete breakdown of company safety measures, while its employees performed like "Keystone Kops" trying to contain it, the National Transportation Safety Board said on Tuesday.
The rupture of Enbridge's pipeline spilled more than 20,000 barrels of heavy crude into the Kalamazoo River in Michigan, in July, 2010.
"This investigation identified a complete breakdown of safety at Enbridge," NTSB Chairman Deborah Hersman said in a statement.
"Their employees performed like Keystone Kops and failed to recognize their pipeline had ruptured and continued to pump crude into the environment."
The NTSB said the main failure of the pipeline was due to multiple small "corrosion-fatigue cracks" that grew over time to create a breach in the pipe over 80 inches long.
The rupture, which spilled crude unchecked for 17 hours, has raised concern about pipeline safety in North America, including Enbridge's planned oilsands pipeline from Alberta to the British Columbia coast, as well as TransCanada's Keystone pipeline in the United States.
Enbridge said in a statement it believed its personnel were trying to do the "right thing" at the time.
"As with most such incidents, a series of unfortunate events and circumstances resulted in an outcome no one wanted," said Patrick Daniel, Enbridge's chief executive.
The U.S. pipeline regulator in early July slapped a $3.7 million fine on Enbridge, the largest it has ever imposed.
The Pipeline and Hazardous Materials Safety Administration, or PHMSA, said its probe uncovered two dozen regulation violations related to the leak on Enbridge's Line 6B near the town of Marshall, about mid-way between Detroit and Lake Michigan.
The accident shut down the pipeline for more than two months and spawned a massive clean-up that the company has estimated will cost more than $700 million.
Following the Enbridge spill and other major pipeline accidents, the Transportation Department enhanced its oversight last year.
Last December, Congress passed a pipeline safety bill that raised maximum fines and authorized an increase in the number of pipeline inspectors.