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Study: 1.6% chance of Mackinac pipeline leak by 2053

Jonathan Oosting
Detroit News Lansing Bureau

Holt — There is a small risk of an oil spill from the 64-year-old dual pipeline running beneath the Straits of Mackinac, but a leak or rupture could significantly affect the Great Lakes, according to analysts contracted by the state of Michigan to assess potential energy delivery alternatives.

James Mihell, an engineer with Dynamic Risk Assessment Inc., told the public this week his firm projects a 1-in-60 probability of failure between now and 2053 for the section of Enbridge Energy Inc.’s Line 5 pipeline that runs through turbulent waters connecting lakes Huron and Michigan.

That amounts to cumulative odds of 1.6 percent over the next 35 years, Mihell said late Thursday during a public hearing on a 337-page alternatives assessment report the Calgary-based contractor prepared for release and review last week.

An Enbridge spokesman said Friday the company is still reviewing the preliminary report but downplayed the overall failure projections, noting the low odds analysts had identified for individual risks.

But a University of Michigan researcher who has also modeled Line 5 spill scenarios said the new findings add “to the ammunition the state has to shut down the pipeline,” should officials decide to do so.

Mihell discussed the failure probabilities during a question-and-answer session hours after environmental activists had accused Dynamic Risk of underestimating the potential impacts of a spill, arguing the alternatives assessment report “is the oil industry’s version of protecting the Great Lakes.”

But Mihell disputed any suggestion his firm was low-balling the risk.

“What we’re talking about are very significant consequences,” he said.

The report detailed threats that could increase the failure probability of the existing straits section of Line 5 — including mechanical damage, weather and incorrect operations — but concluded the passage of time was not a major risk itself.

While the experts did not recommend any particular action by the state, they described several “feasible” alternatives to the 4.5-mile straits section of the pipeline, including construction of a new trench or tunnel crossing at the same location.

Enbridge, which has consistently defended the integrity of the pipeline, said Thursday the report confirms that Line 5 “could safely operate well into the foreseeable future.” The straits section transports up to 540,000 barrels a day of light crude oil and natural gas liquids.

“What is important to note is that the alternatives analysis report found that time has had no bearing on the condition of the pipe,” Enbridge spokesman Ryan Duffy said in a Thursday statement. “Enbridge’s inspection, monitoring and modernization efforts continue to help Line 5 in the Straits operate safely and reliably.”

Threats analyzed

The most dominant threat to the pipeline, researchers said, is the risk of “anchor hooking” caused by the inadvertent deployment of anchors by ships traveling through the straits. Water flow around the pipeline and stress due to unsupported span lengths were deemed smaller risks that increased marginally through 2053.

In-line inspections performed for Enbridge and shared with the research team show “there is no evidence of any external corrosion” on either of the dual pipelines, Mihell said.

Duffy said Enbridge is still evaluating all the data in the preliminary report, but he noted low probabilities associated with top Line 5 risks identified in the report.

“The anchor strike risk was estimated at three to four events in 10,000 years, and incorrect operations risk was estimated at one in 10,000 years,” he said Friday. “The risk due to current vibration is estimated at one to two events in 100,000 years.”

A single spill could affect roughly 20 miles of Great Lakes shoreline, according to Dynamic Risk, primarily affecting Cheboygan, Emmet and Mackinac counties. The neighboring counties of Chippewa, Charlevoix and Presque Isle could also be affected, according to modeling by the researchers.

Activists with a group called Oil & Water Don’t Mix contend the report underplays the potential impact of a spill. They pointed to modeling by UM researchers suggesting more than 700 miles of shoreline on lakes Huron and Michigan could be vulnerable if the pipeline ruptures.

But the lead researcher on that report, UM hydrodynamics expert David Schwab, mostly praised the Dynamic Risk team on Thursday night.

“You didn’t candy-coat it,” Schwab said at the public hearing.

A spill or rupture could carry total economic costs of between $100 million and $200 million, including environmental damages, according to the report.

The straits analysis evaluated the impact of a full-bore rupture in one of the 20-inch diameter pipelines, or a 3-inch diameter leak that would release 2,600 barrels of oil within a 10-minute detection window or 4,500 barrels within 30 minutes. The models consider additional time for pump shutdown, valve closure and drainage time.

“$200 million for a light oil spill is a very large number, said Jack Ruitenbeek of H.J. Ruitenbeek Resource Consulting Limited, which worked with Dynamic Risk on the alternatives assessment report. “More than half of that is environmental damages. These are significant, significant damages.”

Marshall repeat ruled out

Line 5 safety skeptics point to the 2010 rupture of an Enbridge pipeline in Marshall that dumped more than a million gallons of heavy crude oil into the Kalamazoo River. The cleanup cost more than $1 billion, making it the most expensive inland oil spill in United States history.

The Kalamazoo River spill went undetected for 17 hours because control center staff mistakenly attributed the alarms as an indication of an incompletely filled pipeline, known as column separation, according to a 2012 federal accident report.

Column separation is the “Achilles’ heel” of any leak detection system in liquids pipelines, Mihell said, but it is not an issue for the straits section of Line 5.

“This is a section in pipeline that column separation cannot occur,” he said. “... So any alarm that gets triggered in this segment cannot be confused with a column separation event and therefore be misdiagnosed.”

The independent report was prepared for the state using money Enbridge set aside in an escrow account. When finalized, it is expected to inform future state decisions about the dual pipeline.

Attorney General Bill Schuette last week called for development of a time line to eventually shut down or replace the straits pipeline. Activists are urging immediate action, but business groups say closure could jeopardize a key conduit for energy delivery in the region.

About 150 people attended Thursday’s 4.5-hour informational meeting at Holt High School, where many auditorium seats were unfilled. It was the first of four sessions planned during a 30-day public comment period. Additional “feedback sessions” are scheduled for July 24 and 25 in Holt, Traverse City and St. Ignace.

Public comments can also be submitted online through or by mail to the Michigan Agency for Energy, Attn: Line 5 Pipeline Study, P.O. Box 30221, 7109 W. Saginaw Highway, Lansing, MI, 48917.

After the 30-day period concludes, the public will have another 15 days to reply to comments before a final version of the report is prepare for release, likely in the fall.

The state last month canceled a separate Line 5 risk analysis study, citing an undisclosed conflict of interest by an employee of the firm hired to perform the assessment. The Det Norske Veritas staffer had worked on another project for Enbridge after working on what was supposed to be an independent analysis for the state.