The NTSB also blamed “weak federal regulations” by the Pipeline and Hazardous Materials Safety Administration for the accident, which spilled at least 843,444 gallons of oil into a tributary of the Kalamazoo in Marshall, Mich. The oil spread into a 40-mile stretch of the Kalamazoo and a nearby wetlands area.
The NTSB said Enbridge had noticed cracks as early as 2005 but had failed to repair them.
“This accident is a wake-up call to the industry, the regulator, and the public,” NTSB Chairman Deborah A.P. Hersman said in a statement. “Enbridge knew for years that this section of the pipeline was vulnerable yet they didn’t act on that information.” She added that “for the regulator to delegate too much authority to the regulated to assess their own system risks and correct them is tantamount to the fox guarding the hen house.”
The spill began about 5:58 p.m. on July 25, 2010, when a 30-inch diameter pipeline ruptured. Twice, Enbridge workers tried to restart the pipeline after alarms about abnormal pressure in the line and 81 percent of the oil spilled over 17 hours after those alarms, the NTSB said.
“We believe that the experienced personnel involved in the decisions made at the time of the release were trying to do the right thing,” Enbridge’s chief executive, Patrick D. Daniel, said. “As with most such incidents, a series of unfortunate events and circumstances resulted in an outcome no one wanted.”
The case is being scrutinized by industry and environmental groups because it could threaten plans to build new pipelines to carry crude from Canada’s oil sands, or tar sands, into the United States. TransCanada’s controversial Keystone XL pipeline is one of the plans awaiting approval. Last month, the Environmental Protection Agency reopened the Kalamazoo for recreational use but said an area known as the Morrow Lake Delta would remain closed. It said there could be “temporary effects such as skin irritation” from “touching residual oil on the river or in the sediment.”
The NTSB, part of the Transportation Department, said the Enbridge pipeline break “was the result of multiple small corrosion-fatigue cracks that over time grew in size and linked together, creating a gaping breach in the pipe measuring over 80 inches long.”
Environmental groups say that the ingredients of crude from the oil sands could increase the number of pipeline leaks and that any spill would pose new cleanup problems because the bitumen in such crude oil sinks to the bottom of rivers and lakes instead of floating like that of conventional crude oils.