A report released last week by the National Transportation Safety Board shows employees in an Enbridge control center located in Edmonton, Alberta did not know they were pressurizing a ruptured oil pipeline in Michigan.
Employees in the control center felt they were dealing with false alarms due to pressure losses in the pipeline after a planned shutdown.
The pressure losses were not due to "column separation" as some thought (air and vapor pockets between slugs of oil in the pipeline). They were caused by a break in the line.
The rupture led to the spill, and the continued pumping made it worse. More than 840,000 gallons of oil spilled, according to Enbridge.
However, the EPA estimates that more than 1 million gallons of thick, tar sands oil have been removed from Talmadge Creek and the Kalamazoo River so far. The spill is still being cleaned up nearly two years later.
The NTSB estimates the pipeline ruptured around 5:58 p.m. on Sunday, July 25, 2010. Enbridge officials didn't know they had a spill on their hands for nearly 17 hours after the initial break.
In fact, employees increased the pressure in the pipeline - twice.