Enbridge ship plans Line 5 tunnel preparation work in Straits of Mackinac

Evan James Carter
The Detroit News
Enbridge's Highland Eagle vessel stopped in Detroit on Wednesday, July 10, 2019, before heading to the Straits of Mackinac. The company plans to use the ship to collect rock samples along the lake bed where it wants to build a tunnel to house Line 5.

Detroit — Enbridge showed off Wednesday an exploratory vessel from the United Kingdom that is headed for the Straits of Mackinac to collect rock and soil samples in preparation for building a controversial tunnel to house Line 5.

The Canadian company expects the Highland Eagle — often used to investigate the sea bed for structures like off-shore wind turbines — to begin drilling for rock samples before the end of July, ending around the end of October.

The geotechnical work is part of the $40 million Enbridge plans to spend this year in the beginning phases of its construction of a $500 million utility corridor project to replace the oil and gas dual pipeline, an investment made even as the state challenges the agreement to build the tunnel. The company received permits in January from the state's environmental department to begin collecting the samples.

Democratic Attorney General Dana Nessel has asked the Michigan Court of Claims to order the shutdown and decommissioning of Line 5, arguing the 66-year-old oil pipeline's easement is a public nuisance and violates public trust and environmental laws. 

It followed Enbridge's legal filing asking the same court to rule its tunnel project agreement with the state is valid and enforceable. The company, which has said it could complete its project by 2024, said it could not meet the two-year Line 5 decommissioning deadline Democratic Gov. Gretchen Whitmer wanted.

Nessel in March opined that Enbridge’s agreement, established under Republican former Gov. Rick Snyder, was unconstitutional. Whitmer immediately halted state work on the project.

“Officials from the state worked in conjunction with our people to do a feasibility study around the tunnel, and they’ve concluded its feasible and a great idea," said Guy Jarvis, Enbridge executive vice president of liquids pipelines, referring to the Republican Snyder administration. "We’re committed to doing it, and the key issue is getting it done as fast as possible."

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The company emphasized Line 5 is critical to supplying the fuel needs of Michigan. In addition to oil, the pipeline supplies an estimated 55% of the state's propane needs, including about 65% of the propane needed in the Upper Peninsula and northern Michigan, according to Enbridge.

Conducting the geotechnical analysis this summer is critical to the designs of the tunnel and the tunnel boring machine, further regulatory applications and keeping the tunnel project on schedule, Jarvis said.

Enbridge plans to start construction by 2021 and start the tunnel's operation by 2024. Whitmer demanded that Line 5 be decommissioned by 2021.

Opponents have argued the pipeline presents an unjustifiable risk of leaking fuel, especially after a barge accidentally dropped an anchor in April 2018 that dented Line 5 but didn't cause a rupture. A fuel leak would damage the Great Lakes and surrounding environment, they said.

Critics also have suggested the tunnel project and enabling legislation passed in December were rushed. But Jarvis said the tunnel project is the result of “several years of intense work on this, dealing with the state and several agencies within the state.” A state-commissioned alternatives analysis study released in 2017 is one example of the long-term approach, he said.

When the Highland Eagle arrives in the Straits, it will take about 18 to 24 hours to calibrate equipment and make sure the drill rig on board is ready to begin drilling for rock samples, said Amber Pastoor, project manager for the Line 5 Replacement and Tunnel Project.

During its sediment collecting process, Enbridge said it plans to drill 24 holes into the Straits lake bed, which at its deepest point is about 270 feet deep. The proposed tunnel is estimated to be 100 feet below the lake bed.

The vessel will not drop anchor while drilling, instead using a dynamic positioning system with five thrusters under the ship to keep the vessel within 10 to 15 centimeters of the original position it began drilling, Pastoor said.

To guard the Great Lakes ecology, all fluids used during the drilling process as well as any sediment collected will be captured and not discharged into the Straits, she said.

Rock and soil samples will be analyzed on the vessel and the sedimentary data shared with geotechnical professors, giving insight into “the story of the history of the Straits," Pastoor said.

She also suggested the data from the samples would likely be made public after the tunnel is in service.