Enbridge Releases Great Lakes Tunnel Animation


Canadian multinational energy transportation company Enbridge Inc. (Calgary, Alberta) recently released a new animation video showing what the Great Lakes Tunnel Project process and construction for the Line 5 tunnel replacement project in the Straits of Mackinac would look like.

The tunnel is expected to run beneath the Great Lakes channel linking Lakes Huron and Michigan.

About the Project

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.


Posted by Skip McCormic on Thursday, October 1, 2020

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.

However, 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, the 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.

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 seeking 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.

However, at the end of the month, Enbridge officials announced that while installing screw anchors to secure sections of its Line 5 in the channel they discovered four spots where protective coatings had worn away from the underwater oil pipeline.

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. Enbridge spokesperson Ryan Duffy reported at the time that the coatings would be repaired within 10 days following the discovery.

The following month, the 6th U.S. Circuit Court of Appeals overruled District Judge Mark Goldsmith’s ruling 2-1 that Enbridge had to comply with both the Endangered Species and National Environmental Policy Acts regarding its spill plans.

Previously, the company was sued by National Wildlife Federation for allegedly failing to prove that plans wouldn’t jeopardize endangered fish or wildlife and for not issuing an environmental impact statement. However, in the past five years Enbridge had submitted spill plans which were both approved by the federal Pipeline and Hazardous Materials Safety Administration.

Judges Amul Thapar and Joan Larsen stated in their majority opinion that Enbridge had met those standards and that the company plans to have enough personnel and equipment to respond to a worst-case discharge, as well as testing and drills.

Last month, the Michigan Public Service Commission held a virtual public hearing for comments on the proposed Enbridge Line 5 tunnel.

Proponents of the tunnel, which included state representatives, business leaders, members of the United Steelworkers Union in Ohio and Enbridge employees, depicted the plan as a compromise—one that mitigates the greatest risk of an oil spill in the Great Lakes by moving the pipeline from the lakebed. They argued that keeping that access to propane is vital for the region and would also preserve jobs in the safest way possible.

Critics, which include environmental groups, members from the Bay Mills Indian Community, other tribes, local landowners and Michigan residents aren’t convinced that the project has undergone sufficient environmental review and also look to the agreement’s 99-year lease, saying that the tunnel and pipeline would soon become obsolete.

The state is still collecting public comments and is slated to begin hearing testimony from legal challengers next year.

What Now

In a step-by-step animated video, Enbridge has released updated project information on how the company plans to build a four-mile tunnel beneath the Straits of Mackinac to house a new segment of the Line 5 pipeline.

According to the video, using a roughly 500-foot-long tunnel boring machine, the proposed tunnel will be built through rock, deep below the lake bed, in an effort to add further protection of Michigan waters, while also ensuring an uninterrupted supply of reliable, affordable energy.

The tunnel itself is reported to be made up of a reinforced concrete liner measuring one foot thick, with grout completing the seal. Pipe supports, complete with rollers, will be bolted along the inside of the tunnel walls. It also plans to be equipped with drainage, leak detection equipment and electronic communications.

Research into constructing the tunnel began in 2019 when various sediment and rock samplings were taken from the straits to establish design plans. Prior to construction, staging areas are expected to be placed at both the North and South shores of the straits, with a large, sheltered portal created on the South shore which will serve as the entry point for the tunnel boring machine.

A slurry separation plant is also planned for the South shore, where a mixture of rocks, pebbles, clay and water will be pumped out of the tunnel when excavation begins. Once separated, water will then be recycled back into the tunneling process.

As for the North shore, a vertical shaft is slated to be constructed, where the tunnel boring machine will be retrieved and dismantled after it made its way across the straits—an endeavor projected to take roughly two years, moving at an average of 40 feet a days five days a week.

Over the course of the construction, saturation divers will be used to perform regular inspection and maintenance because of the high hydrostatic pressure experienced during construction.

Once tunnel construction has commenced, Enbridge plans to assemble new segments of the Line 5 pipeline, which will be welded, inspected and coated all on the South side in a staging area prior to installation.

While the tunnel has been constructed to serve Line 5, put could accommodate third party utilities, according to Enbridge.

Project construction is expected to start in 2021.

Readers can watch the full video, here.


Tagged categories: NA; North America; Oil and Gas; Ongoing projects; Pipelines; Program/Project Management; Project Management; Tunnel

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