Report: Enbridge stopped and restarted pipeline during oil spill
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.
Inside Climate News reports on the NTSB report:
The accident began when operators were shutting down 6B as part of a routine procedure to allow the next shipment of oil to accumulate at the start of the line in Griffith, Ind. An alarm sounded and the pump station at Marshall automatically went into a local shutdown within minutes of the rupture, which investigators say occurred at 5:58 pm eastern time on July 25, 2010—a Sunday evening. But at 4 a.m. and again at 7:10 a.m., operators at Enbridge's control room restarted the line. During the first restart, technicians pumped oil under high pressure into the line for one hour; during the second restart, for at least 45 minutes.
Enbridge operators restarted the line because they had concluded that the alarms were being triggered by "column separation," or an air bubble in the line, and that the problem could be corrected by increasing the pumping pressure.
Here's how it was put in the NTSB report summary:
On the evening of Sunday, July 25 2010, at approximately 5:58 p.m., a 40-foot long pipe segment in Line 6B, located approximately 0.6 of a miles downstream of the Marshall, Michigan pump station, ruptured. The Line 6B is owned and operated by the Enbridge Energy Inc. (Enbridge). The Enbridge control center in Edmonton, Alberta Canada was in the final stages of executing a scheduled shutdown of their 30-inch diameter crude oil pipeline (Line 6B) when the rupture occurred. The initial and subsequent alarms associated with the rupture were not recognized as a line-break through two start-up attempts and over multiple control center shifts. Residents near the rupture site began calling the Marshall City 911 dispatch center to report odors at 9:25
p.m. on Sunday; however, no calls were placed to the Enbridge control center until 11:17 a.m. the following day. Once the Enbridge control center was notified, nearly 17-hours after the initial rupture, remote controlled valves were closed, bracketing the ruptured segment within a three-mile section.
About an hour prior to being notified of the spill, an Enbridge regional manager felt they would know if they had a spill on their hands saying, "it seems there is something else going around either with the computer or the instrumentation... you lost column and thing went out of hand. Do you want us to check; right now I am not convinced, we have not had any phone call, if it is a rupture someone is going to notice that and smell it."
At 11:17 a.m., they got the call from someone investigating smells in the area. The report states a gas employee alerted Enbridge to the spill:
At 11:17 a.m. the Enbridge control center Shift Lead C1 received a call on the emergency line from a consumer energy gas utility employee reporting of oil on the ground downstream of the Marshall station. The caller stated the oil was into the Creek and believed it belonged to Enbridge Energy pipeline. That there was lots of oil and that they got 20 gas leak calls and had tried to walk the line to see where the pipeline broke. Then stated the Creek color was black and he was located at 27 Southern Division Drive also called South Kalamazoo. The caller then asked Shift Lead C2 if they had local personnel and he responded yes. The caller re-iterated being located at south of Marshall. Shift Lead C2 stated that the control center would be giving the Enbridge Energy field personnel a call.
The NTSB is expected to release a final report on what caused the Enbridge oil spill later this summer.