{"id":14521,"date":"2026-07-22T07:30:59","date_gmt":"2026-07-22T11:30:59","guid":{"rendered":"https:\/\/www.autonocion.com\/us\/?p=14521"},"modified":"2026-07-22T06:09:35","modified_gmt":"2026-07-22T10:09:35","slug":"michigan-old-oil-pipeline-great-lakes","status":"publish","type":"post","link":"https:\/\/www.autonocion.com\/us\/michigan-old-oil-pipeline-great-lakes\/","title":{"rendered":"Michigan just cleared the way to bury a 73-year-old oil pipeline under the Great Lakes in a four-mile tunnel, dug by a machine 500 feet long, nearly two football fields, tended by divers who live in pressurized chambers for weeks 270 feet down"},"content":{"rendered":"

For most of the last decade, the fight over Line 5 has been a fight about a pipeline that mostly just sits there. Two 20-inch steel pipes, dropped onto the bottom of the Straits of Mackinac back in 1953, still push oil and natural gas liquids through the exact spot University of Michigan engineers<\/a> have called the worst possible place in the Great Lakes for a spill.<\/p>\n

On July 15, Michigan cleared the way to get those pipes off the lakebed. Two state agencies issued the permits Enbridge needs to bury a replacement segment inside a four-mile tunnel bored through bedrock under the Straits.<\/p>\n

The tunnel isn’t really the story here, though. The machine is. Because burying a pipeline under one of the Great Lakes takes a boring machine roughly 500 feet long, and as of today it hasn’t turned a single cutter.<\/p>\n

Two agencies signed off. The Army Corps hasn’t<\/h2>\n

The permits came from two Michigan departments on the same day. The Department of Environment, Great Lakes and Energy<\/a> (EGLE) reissued a wetlands and bottomlands permit after a roughly 16-month review, concluding that “the public and private need for the proposed activity outweighed other public interest criteria.” A short time later, the Department of Natural Resources granted a separate permit covering the project’s effect on rare plants and animals.<\/p>\n

EGLE had actually approved this same permit once before, back in 2021. It expired while the project sat tangled in state and federal court for years.<\/p>\n

None of that lets Enbridge start digging tomorrow. The project still needs a federal sign-off from the U.S. Army Corps of Engineers, and that hasn’t landed yet. Both sides expect it soon, according to the Associated Press, though “soon” is a word that has aged badly at almost every earlier stage of this thing.<\/p>\n

The backstory explains the pileup. Governor Gretchen Whitmer revoked Enbridge’s easement to use the Great Lakes bottomlands in 2020, the company kept operating the line anyway, and that case is still sitting in federal court. The Michigan Public Service Commission signed off on the tunnel itself in December 2023. The Army Corps only sped up its own review after President Trump’s energy emergency order pushed federal agencies to fast-track this kind of project.<\/p>\n

The machine that does the digging is about 500 feet long<\/h2>\n

Here’s what actually has to happen once the last permit clears. Enbridge’s contractors assemble a tunnel boring machine, or TBM, that runs about 500 feet front to back and carries thousands of individual parts. Assembly alone takes three to four months, according to Engineering News-Record<\/a>.<\/p>\n

The two firms Enbridge picked to build it, Barnard Construction and Civil and Building North America, have been signed on since 2024. They just haven’t been able to start.<\/p>\n

Once it launches from a site on the south side of the Straits, the machine grinds forward through limestone, rock and shale. As it goes, it sets one-foot-thick segments of reinforced concrete into place behind the cutterhead and seals them into rings, so the tunnel is basically dug and built in the same motion.<\/p>\n

Its target pace is up to 40 feet a day, five days a week. For four miles of bedrock, that adds up slowly, which is part of why this tunnel was originally supposed to be finished back in 2024.<\/p>\n

Boring under the Great Lakes is its own kind of hard<\/h2>\n

A four-mile tunnel under open water is not a normal dig. The bore is 21 feet across on the inside, sized to hold a single 30-inch pipe that replaces the two 20-inch lines on the lakebed. It runs through bedrock beneath the lake floor, as much as 100 feet down into the rock by Enbridge’s own description.<\/p>\n

And the water sitting on top of it is deep. The existing pipes drop to roughly 270 feet along the bottom of the Straits at the deepest point, per University of Michigan engineers. That’s the water the tunnel has to pass under without letting any of it in.<\/p>\n

So there’s a slurry plant at the surface to separate out the rock, clay and pebbles the machine pumps back, with the water cleaned and reused in the boring. And then there’s the part that sounds made up: saturation divers.<\/p>\n

Inspections and maintenance inside the tunnel get handled by divers who live in pressurized chambers on the surface for weeks at a stretch, then get lowered to the work in a pressurized habitat mounted at the head of the machine, per Engineering News-Record. It is a genuinely extreme way to babysit a drill.<\/p>\n

\n
\n
The tunnel<\/div>\n
4 miles<\/div>\n
21-foot inside diameter, bored through bedrock under the Straits of Mackinac.<\/div>\n<\/div>\n
\n
Boring machine<\/div>\n
~500 ft<\/div>\n
Length of the TBM, front to back. Thousands of parts, three to four months just to assemble.<\/div>\n<\/div>\n
\n
Dig pace<\/div>\n
40 ft\/day<\/div>\n
Target speed, five days a week, through limestone, rock and shale.<\/div>\n<\/div>\n
\n
The pipeline<\/div>\n
73 years<\/div>\n
Built in 1953. Line 5 carries about 540,000 barrels of oil and natural gas liquids a day.<\/div>\n<\/div>\n
\n
The price<\/div>\n
$500M \u2192 $750M+<\/div>\n
2018 estimate vs. 2022 estimate (IEEFA). Enbridge won’t give a current figure.<\/div>\n<\/div>\n
\n
PENDING<\/div>\n
What’s left<\/div>\n
Federal permit<\/div>\n
State permits came July 15. The U.S. Army Corps still has to sign off before boring can start.<\/div>\n<\/div>\n<\/div>\n

The bill went from $500 million to a number Enbridge won’t name<\/h2>\n

When the deal was struck in 2018, the tunnel carried a $500 million price tag. By 2022 that had climbed to at least $750 to $800 million, according to an analysis from the Institute for Energy Economics and Financial Analysis cited by Engineering News-Record. Enbridge’s spokesperson declined to give an updated figure.<\/p>\n

It’s a private investment, not taxpayer money, and Enbridge is quick to point that out. Michigan’s own conservation groups counter that the state could still be left holding financial liability if something fails inside the tunnel, which is a big part of why this fight has never really been about the pipe alone.<\/p>\n

The tunnel still has to get past its opponents<\/h2>\n

The permits were a loss for the people who have spent years trying to stop this. Within hours, the Bay Mills Indian Community said it would sue over the decision. Its president, Whitney Gravelle, tied the project to disturbed Native American burial grounds in the area: “Even in death we cannot know peace.”<\/p>\n

The Michigan League of Conservation Voters condemned the approval and argued the tunnel threatens tribal rights protected under the 1836 Treaty of Washington. Representative Rashida Tlaib and a long list of environmental groups lined up against it too.<\/p>\n

The safety argument cuts both ways, and that’s the uncomfortable part. State regulators concluded the tunnel is safer than leaving an aging pipeline exposed on the lakebed to anchor strikes, the same kind that have already dented Line 5 hardware twice without causing a spill. But engineers and tunnel-safety experts have warned the commission that a sealed tunnel carrying oil and natural gas liquids is also an enclosed space, where a leak and a spark could add up to an explosion.<\/p>\n

For its part, Enbridge calls the permits “an important step forward for a project designed to further protect the Great Lakes while helping ensure the uninterrupted flow of energy that supports Michigan and the region,” and maintains that Line 5 runs safely and reliably under federal standards.<\/p>\n

How it stacks up against the last few big bores<\/h2>\n

A 500-foot machine sounds enormous until you look at what’s already chewing through rock elsewhere in the country. The four TBMs headed under the Hudson for New York’s new rail tunnel run about 498 feet each<\/a>, and a 1,200-ton German-built machine is already grinding a sewage tunnel under the Potomac in Washington<\/a>.<\/p>\n

The cautionary tale is Seattle. Bertha, the 57.5-foot-wide machine digging under downtown, stalled a little past 1,000 feet into a roughly 1.75-mile dig and needed crews to sink a rescue pit from the street<\/a> to haul out and rebuild her cutterhead. That repair took two years. Under the Great Lakes, there is no street to dig down from.<\/p>\n

None of this puts a machine in the ground yet. Until the Army Corps signs the federal permit, the 500-foot TBM stays unbuilt, the contractors stay idle, and the two 20-inch pipes stay right where they’ve been since 1953: on the floor of the Straits, moving roughly 540,000 barrels a day through the worst place in the Great Lakes to spring a leak. The permits changed the paperwork. They didn’t move the pipe.<\/p>\n","protected":false},"excerpt":{"rendered":"

For most of the last decade, the fight over Line 5 has been a fight about a pipeline that mostly … <\/p>\n

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