2018-05-12 / News

Enbridge Line 5 Pipelines Dented in Event Related to Severed Electric Cables

By Stephanie Fortino


The dents (circled) on the east (left) and west pipes of Line 5 are shown in these photographs from a remotely operated vehicle. While the cause of the damage is still under investigation, the attorney general has alleged the damage was caused by an anchor from a passing tug. Pressure in the pipes has been reduced, and Enbridge is developing plans to reinforce the pipes soon. (Ballard Marine Construction photographs) The dents (circled) on the east (left) and west pipes of Line 5 are shown in these photographs from a remotely operated vehicle. While the cause of the damage is still under investigation, the attorney general has alleged the damage was caused by an anchor from a passing tug. Pressure in the pipes has been reduced, and Enbridge is developing plans to reinforce the pipes soon. (Ballard Marine Construction photographs) Enbridge Energy’s Line 5 twin pipelines that run beneath the Straits of Mackinac were dented in an event that is probably related to the damage that occurred to the nearby American Transmission Company (ATC) electric cables. Since the Coast Guard is still investigating the incident, the cause of the damage to the ATC cables and Line 5 has not been confirmed. While the pipelines are damaged, the structural integrity of the lines has not been compromised, according to Enbridge spokesman Ryan Duffy, but the pressure of oil flowing through the line was reduced Friday, April 27.

As part of the response to the damaged ATC electric cables, which resulted in the spill of about 600 gallons of mineral-based oil that contains dielectric fluid, Enbridge temporarily shut down Line 5 Tuesday, April 3. The Coast Guard advised the utility companies to inspect their own infrastructure in light of the damage to the ATC cables.

While Line 5 was initially shut down April 3, the leak detection and operating system data were evaluated. Wednesday, April 4, Enbridge sent caliper inspection tools through each pipeline. When the data the tool collected was reviewed, the company determined that the structural integrity of the lines was not affected, and the flow of oil was resumed that afternoon.

More testing occurred the following weekend. Saturday, April 7, Enbridge sent a high-resolution geometry tool through the lines. Mr. Duffy said the dents were confirmed Tuesday, April 10, based on the inspection that Saturday. Enbridge then notified the state and the Coast Guard of the damage. Mr. Duffy confirmed that the structural integrity of the pipelines was not compromised, following a review of the leak detection systems and other data, he said Wednesday, April 11.

The revelation of the dents in Line 5 does not affect the Coast Guard’s response to the ATC oil spill, said LT JG Sean Murphy Thursday, April 12.

“There’s no pollution risk” at Line 5, he said, so the Coast Guard’s priority remained cleaning up and monitoring the ongoing efforts at the ATC cables, which has since finished.

Wednesday, April 11, Governor Rick Snyder issued a statement indicating that the damage to both the ATC electric cables and Line 5 could have been caused by an anchor from a ship traveling through the Straits of Mackinac. An anchor strike has been identified as the highest risk to Line 5, he said, and he called for the Straits of Mackinac crossing of Line 5 to be replaced with a tunnel if feasible.

In a statement Friday, April 13, U.S. Senator Gary Peters said, “Yesterday, I was personally briefed by U.S. Coast Guard officials in Michigan on the damage to Line 5 caused by a vessel anchor strike in the Straits of Mackinac. Based on the limited information currently available, two segments of the pipeline will require repairs in the short-term, but a visual inspection is still needed to assess the full extent of the damage.”

Enbridge inspected Line 5 using inline inspection tools and a re- mote-operated vehicle/autonomous underwater vehicle machine later in April. Once more inspections are completed, Mr. Duffy said, Enbridge will begin repairing the damage in close coordination with the state ad the Pipeline and Hazardous Materials Safety Administration (PHMSA), the federal agency that oversees pipeline safety.

The company announced April 27 that it reduced the oil pressure in the line.

The pressure reduction is a “precautionary and prudent measure,” according to an Enbridge statement.

Enbridge reduced the pressure after consulting with PHMSA, federal guidelines, and state officials.

Despite the damage, the structural integrity of the pipelines is sound, Enbridge says.

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