Protective Coating Gaps Found on Enbridge Pipeline


Last week, officials from Canadian company Enbridge Energy announced that they had discovered four spots where protective coatings had worn away from an underwater oil pipeline in Michigan’s Straits of Mackinac.

According to reports, crews noticed the spots while installing screw anchors to secure sections of its Line 5 in the channel.

About the Enbridge Pipeline

In July 2017, Michigan Pipeline Safety Advisory Board released an assessment of Enbridge Energy’s Line 5 liquid pipeline that looked at the risks related to keeping the current pipeline—which was built in the 1950s and crosses under the Straits of Mackinac—as well as alternatives, including new lines in or around the straits, a new pipeline elsewhere or a complete abandonment of the line.

The assessment was prepared by Dynamic Risk Assessments Inc.

According to Dynamic Risk, the biggest threats to the existing pipeline are anchor hooking, incorrect operations, vortex-induced vibration and spanning stress. A spill in the straits, the firm contends, would likely incur $100-200 million in costs, about 60% of that covering environmental cleanup. Those figures account for what Dynamic Risk calls “objective assessments of credible risks,” and not a worst-case scenario.

By June 2018, Enbridge Energy released its report to the state of Michigan on possible replacement of its Line 5 pipeline, concluding that a tunnel or an open cut with secondary containment would be feasible methods for replacing the 65-year-old liquids pipeline.

In the report, Enbridge says its study, performed by independent consultants, showed a tunnel created by a tunnel-boring machine could be a feasible method of installing a new pipeline to replace Line 5. Such a tunnel would have a 10-foot inside diameter and would stretch four miles long, 100 feet below the deepest part of the Straits.

A tunnel would cost $350-500 million, Enbridge says, and if this alternative were chosen, the dual 20-inch pipelines comprising the current Line 5 would be replaced with one 30-inch line. The concrete tunnel would be lined with precast concrete tunnel lining; the annulus outside the tunnel lining would be filled with cement grout.

The other alternative the company says could work would be an open cut with a secondary-containment pipeline around a new 30-inch Line 5. This approach would cost $250-300 million and would involve trenching the pipeline for the first half-mile or so from the shoreline, then laying the majority of the line on the lakebed with an engineered protective cover.

The pipe-in-pipe system would involve a 30-inch steel pipeline surrounded by a 36-inch secondary-containment line with low-friction spacer rings in the space between. The outer pipeline would be engineered to withstand pressures greater than the line’s operating maximum.

Although, a worst-case spill on Line 5, according to a risk analysis by Michigan Technological University, could affect more than 400 miles of shoreline on Lake Michigan and Lake Huron and come with a price tag of more than $1.8 billion.

A lawsuit filed at the end of August 2018 by the Environmental Law and Policy Center and the National Wildlife Fund alleged that a top Coast Guard official testified under oath in front of Congress the year before that the service was not adequately prepared for a worst-case spill on the line, though the Coast Guard does have a contingency plan in place to do just that.

In December, Michigan Senate voted to create the three-member Mackinac Straights Corridor Authority, an entity that would oversee the construction of the replacement pipeline and a new utility tunnel.

According to Crain’s Detroit Business, creating the panel is an essential step toward replacing the underwater pipeline. The project is slated to take seven to 10 years to complete, and the cost of replacing the pipeline could range from $350-500 million, all paid for by Enbridge, but owned by the Mackinac Bridge Authority.

However, in May 2019, the law to create the three-member Mackinac Straights Corridor Authority was ruled unconstitutional by the state attorney general. Gretchen Whitmer, Michigan’s current governor, asked for Attorney General Dana Nessel's legal opinion. In Whitmer’s view, the law is invalid. Earlier last year, Whitmer halted state agencies’ attempts to facilitate construction on the tunnel.

State legislature Republicans have dismissed Whitmer’s opinion, citing that a judge has already allowed the law to be as is.

The state attorney general’s communications director, Kelly Rossman-McKinney, noted that the attorney general thinks the opinion will be upheld. If that happens, though, consumer groups are likely to sue, according to the Engineering News-Record, given that Upper Peninsula residents oppose measures that would take Line 5 out of service without replacement.

At the beginning of March, Enbridge announced that it hired Arup (London) to design the tunnel and Great Lakes Tunnel Constructors—a partnership between Jay Dee Contractors Inc. (Livonia, Michigan) and Obayashi Corp. (Tokyo)—to build it.

At the time of the announcement, the company was still continuing to seek construction permits from the Michigan Department of Environment, Great Lakes and Energy and the U.S. Army Corps of Engineers.

In mid-May, the Corps Detroit district office announced it would begin accepting public comments on Enbridge’s proposal to build an oil pipeline tunnel beneath Michigan’s Straits of Mackinac. The comment period follows the submission of a complete project application.

"We have not scheduled a public hearing, but commenters to the public notice may request a public hearing," said Katie Otanez, a regulatory project manager for the corps' Detroit District said at the time. "The corps will determine whether a public hearing is needed based on whether a hearing is likely to result in information that could not otherwise be gained."

Once the project receives the green light, construction is scheduled to begin near year with a 2024 target completion date.

Protective Coating Issue

Located on the east segment of Line 5—which divides into two pipes when crossing the bottom of the straits—are four spots measuring less than 6 square inches in size where protective coatings have failed, revealing exposed bare metal.

“We immediately inspected the line with remotely operated vehicles and with divers and determined there are no integrity issues and Line 5 remains safe,” Enbridge spokesperson Ryan Duffy said.

Duffy adds that since the discovery, crews planned to repair the coatings within the following 10 days. However, the company plans to replace the underwater portion of Line 5 with a new segment that would extend through a tunnel to be drilled beneath the straits.

Enbridge is still currently waiting for necessary permits to break ground on the tunnel’s construction.


Tagged categories: Coating failure; Corrosion; Corrosion protection; Infrastructure; NA; North America; Oil and Gas; Ongoing projects; Pipeline; Pipelines; Project Management; Protective Coatings; Quality Control

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