Scientific experts who have extensively reviewed Enbridge Energy’s proposed Great Lakes Tunnel Project for the Line 5 oil pipeline in the Straits of Mackinac, are raising red flags about the project.

Serious Red Flags about Enbridge Oil Tunnel Project

“Enbridge’s proposed Great Lakes Tunnel Project will likely encounter difficult geologic conditions including poor quality bedrock, fault zones, unconsolidated sediments, and high groundwater pressures,” said Brian O’Mara, a geological engineer and 30-year veteran of tunnel projects, including high-risk open water tunnels and tunnels in the Great Lakes region. “What Enbridge has submitted to the State of Michigan doesn’t come close to properly designing and preparing for a tunnel underwater. Plain and simple.”

O’Mara said one of the red flags in Enbridge’s proposal is the company took boring samples from the Straits of Mackinac every 950 feet – when the industry standard is every 50 feet to 200 feet. Failing to understand the underground rock and soil conditions could lead to massive problems for constructing a tunnel.

“What Enbridge has submitted to the State of Michigan doesn’t come close to properly designing and preparing for a tunnel underwater. Plain and simple.” - Brian O'Mara, geological engineer and 30-year-veteran of tunnel projects

Oppose the Line 5 Oil Tunnel“Enbridge wants to discharge five million gallons of wastewater into Lake Michigan every day that the tunnel is being constructed,” said Mike Wilczynski, who has more than 40 years of geological and environmental experience, including 12 years as a Senior Geologist for the former Michigan Department of Environmental Quality. “Enbridge hasn’t said how it will remove bentonite clay from the slurry prior to discharge. When mixed with water, bentonite will stick to everything it touches – killing off fisheries and destroying our drinking water – not to mention forming an impermeable barrier suspended on top of Lake Michigan for years to come.”

For a deeper dive into the analysis of Enbridge’s proposed Line 5 tunnel from these independent experts, read on for in-depth information from tunnel expert Brian O’Mara and geologist Mike Wilczynski.


Brian O’Mara

Brian O'MaraI have worked as a consultant on tunnel projects with the same type of rock formations and challenges as what exists under the Straits of Mackinac and what Enbridge will confront if it obtains permits to construct this proposed tunnel.

I have spent nearly 100 hours examining Enbridge’s geotechnical reports, geology of the Straits, and reviewed the standards for undertaking this kind of tunnel construction in open water.

It is impossible to sum up all the concerns, inconsistencies, deficiencies, and omissions in a few sound bites, but I can say that what has been submitted is in no way adequate for EGLE to complete a review, let alone approve.

Enbridge has significantly changed the project design in a manner that will cut their costs dramatically but also puts tunnel workers, nearby residents, and the environment at much greater risk.

The current design and plans have not been subject to a risk assessment. The previous risk assessment for the initial design is now invalid.

The risk assessment warned a poor geotechnical study was the greatest risk to the project's success and assumed that a thorough geotechnical program and seismic study would be completed. They were not.

The risk assessment cited that “good rock conditions and minimal groundwater inflow were anticipated.” However, the results of the studies completed after the risk assessment and earlier studies show this is not the case.

The risk assessment assumed no natural toxic gases would be present, but methane was found in the groundwater, and managing methane was not included in the Enbridge design.

The risk assessment assumed the tunnel would be constructed in entirely solid bedrock. The current plan includes tunneling in poor bedrock and the soft silts and clay that overly the bedrock.

Brian O'Mara submitted comments to the Mackinac Straits Corridor Authority in February 2022.

Tunnel in poor bedrock and/or tunneling in rock and sediments at the same time is the most difficult construction condition and can lead to tunnel failures with drastic consequences.

The risk assessment assumed the space around the pipeline inside the tunnel would be filled completely with cement to prevent leaks, explosions, and collapse of the tunnel.

This approach of sealing the tunnel with cement was selected because it was more in line with the objective of isolating the pipeline from the open water of the Straits - the current design will not have this protection.

This single design change represents the greatest risk and would make a catastrophic disaster much more likely to occur.

The initial design involved the construction of a straight-line tunnel at a shallow incline (upward) from a launch shaft on the south side of the Straits to an exit shaft at the north end. This is the standard and preferred method as it is safer for the workers and is the best way to manage groundwater infiltration.

The current design configuration is shaped like a broad “V” with the deepest point beneath the middle of the Straits, presenting safety risks to the workers. This change was also done to save costs.

This makes the middle of the tunnel the least accessible point and the hardest area to reach in case of a boring machine breakdown or flooding.

If there is a flood of water in the tunnel and the workers will be at higher risks because they either be in the deepest part of the tunnel when they’re mining downhill to the middle or they can be cut off by the water if they’re mining on the uphill side of the “V."

I’ve worked underground in many tunnels with high water pressures, and I would NOT want to be caught in a flood situation on either side of the “V!”

Enbridge’s proposed tunnel will certainly encounter difficult geologic conditions, including poor-quality bedrock, fault zones, unconsolidated sediments, and high groundwater pressures.

Enbridge concluded that constructing the tunnel was feasible and used three case studies as examples. However, two of these tunnels cost more than $1.2B. One of these tunnels isn’t completed and could cost more, and one of these was being constructed to replace a “failed” tunnel that had leaked its contents “for decades” upward and into the overlying surface water.

Just because it may be “feasible” to build the tunnel doesn’t mean you should do it. But if you try to build, it should be done correctly.

Enbridge prepared a table of similar tunnels that contained pipelines – only one of these tunnels has been completed in the US in the last 75 years and that tunnel crosses under what may be the most polluted river in the United States and is also a Superfund site.

Several worst-case scenarios could play out, including the possibility the boring machine could become disabled under the Straits, the tunnel could be abandoned, or tunnel operations could severely damage the existing Line 5 west pipeline by either direct contact or secondary settlement.

What Enbridge has submitted to the State of Michigan doesn’t come close to properly designing and preparing for an underwater tunnel.

Plain and simple.

I’ve worked on dozens of tunnels and shafts, including tunnels beneath open water, since 1987.

I’m not anti-tunnel by any means.

But my professional assessment is Enbridge’s proposal falls far short of what is needed.

I’ve outlined most of the major problems with the Enbridge permit proposal, and besides changing the tunnel design, the biggest failure is to undertake adequate boring samples in the Straits.

They have done just a fraction of what you would expect on a project of this size and magnitude.

Borehole SpacingThe rule of thumb is boring should happen every 50 feet to 200 feet.

Enbridge is relying on boring once every 950 feet.

The more borings you do, the better you understand the geology you will confront with your tunnel boring machine.

The more data, the better, yet Enbridge isn’t coming close to what they should have done.

This is particularly important when doing tunnel boring in the open water.

Especially when you have poor rock quality and a mixture of rock conditions as you do underneath the Straits.

If you fail to understand and plan for every rock and soil underground condition along your tunnel, the boring machine can suffer a failure and break down.

That’s what happened on an underground tunnel project in Milwaukee, Wisconsin.

The tunnel boring machine broke down in front of City Hall and got stuck in place.

Crews had to excavate an opening from above ground and pull the broken machine parts out for repair and replacement.

But that’s not an option in the open waters of the Straits.

You can’t reach the tunnel and the boring machine from the top like on land.

You would be forced to remove the entire machine from the tunnel boring entrance.

It could add months or even years to the project.

Ultimately, the tunnel might have to be abandoned altogether.

Enbridge does not even know if they will encounter bedrock in the middle of the Straits, and if bedrock is there, they won’t know how much of it is above the tunnel. Not knowing can create sinkholes during the boring process or blowouts of the bentonite slurry drilling fluid to the lake bottom.

The existing west Line 5 pipeline is nearly directly above the tunneling site, and a tunneling-caused sinkhole could result in catastrophic damage to the existing Line 5 pipeline, which would still be transporting 23 million gallons of oil daily through the Straits.

Data submitted by Enbridge in its permit application reveals the existence of dissolved methane in the groundwater, the aquifer underneath the Straits.

Milwaukee Tunnel DisasterIf groundwater infiltrates into the tunnel, methane dissolves into the air.

If there is a spark from a machine or other source, it would create a potential danger of explosion and pose a threat to the construction crew.

This happened on a Milwaukee tunnel I was working on, and three men were killed in 1989. An even worse disaster occurred near Port Huron when 22 men died from a methane explosion while constructing a tunnel that was five miles from shore in similar limestone bedrock under Lake Huron.

The construction of the tunnel and shafts will change groundwater flow patterns near these features because they must be “de-watered” to keep them dry during and after construction.

The tunnel and shafts act like large drains pulling in water from all directions. They will also likely cause lake water to be pulled into the surface aquifers and may also cause contamination from nearby environmental cleanup sites to move into drinking water wells. Without treatment, the water in these wells could present serious health hazards to residents.

Dewatering the tunnels and shafts may also damage nearby wetlands, which will also be stressed by the stormwater, wastewater, and solid waste generated during construction.

All of these risks must be considered when designing a tunnel project.
But it appears, from Enbridge’s permit filings, they have failed to undertake the required risk assessment.

The more I looked at Enbridge’s permit filings, the more I concluded that permitting this project at this point in time would be a huge mistake.

There are so many unanswered questions, making it premature for these permits to be reviewed by the state.

Mike Wilczynski

Mike WilczyniskiThe slurry, or drilling mud Enbridge plans to use in excavating the tunnel, is a big concern considering the 5 million gallons a day of wastewater Enbridge proposes discharging into Lake Michigan as part of its tunnel construction.

The slurry, or drilling mud, is a mix of bentonite clay, water, and additives and is often referred to as bentonite slurry or just slurry.

Bentonite is non-toxic to humans and an ingredient in various products we use daily.

However, when mixed with water, it could cause significant environmental harm if an accidental release were to occur.

As a hydrogeologist and former Senior Geologist with the former Department of Environmental Quality, Bentonite is a clay mineral I have studied extensively.

Based on my background, I can tell you Enbridge’s permit to discharge up to 5 million gallons of wastewater into the Great Lakes is unsafe, harms our waterways, and should be rejected.

Enbridge hasn’t said how it will store and treat this bentonite slurry to separate the bentonite clay from water before discharging it into Lake Michigan.

Sunoco Spills Drilling Fluid While Drilling Under Chester Creek (sandbags used to try to stop)
Sunoco Spills Drilling Fluid While Drilling
Under Chester Creek (sandbags used to try to stop)

What are Enbridge’s protocols to prevent an accidental release of bentonite slurry into Lake Michigan?

We don’t know.

There is nothing in Enbridge’s permit application to assure us Lake Michigan will be protected from this massive wastewater discharge.

What worries me most is a bentonite discharge into the Straits could be even worse than an oil discharge.

Bentonite is an expandable clay mineral that can stay suspended in water — almost forever.

It can stick to everything it touches and forms an impermeable barrier.

It can coat fish gills and kill the benthic community at the bottom of the Straits.

And most importantly, it pollutes our drinking water.

When oil is discharged into water, it floats and congeals on the surface and can be recovered.

Not so for bentonite that remains suspended in the lake water until it contacts and coats something.

What plans are in place to recover an accidental release of bentonite slurry?

Marys River near Albany a release of bentonite slurry used as a lubricant in a gas pipeline project.
Marys River near Albany, a release of bentonite
slurry used as a lubricant in a gas pipeline project.

A release can also occur during the boring of the tunnel in what is known as a frac out or during a release of bentonite slurry from the boring.

The reefs in the Straits make up 60% of the lower lakes fish breeding grounds, according to environmental experts with the Sault Tribe of Chippewa.

Losing that fishery would be catastrophic.

Losing our pristine Great Lakes to an accidental release of potentially dangerous bentonite slurry and its additives could create an unmitigated environmental disaster.

When I retired as a senior geologist with the former Department of Environmental Quality, my agency was already understaffed and lacked the scientific resources and knowledge to adequately fulfill its mission to protect the Great Lakes and Michigan’s environment.

My vacant position was never filled with an experienced geologist.

That’s also been the case with many other important positions once occupied by experienced scientists with the educational background and experience to protect our precious natural resources and —more importantly — human health.

Now, the agency is known as the Department of Environment, Great Lakes & Energy (EGLE), but little has changed except the name when it comes to being up to the job of being the public’s environmental watchdog.

This tunnel project is one of the most significant proposed Great Lakes environmental projects in Michigan’s history, if not the biggest.

The consequences of failing to protect the Great Lakes and eliminating risks to our environment are potentially catastrophic.

The existence of so many technical, risk management, and regulatory deficiencies at this stage of Enbridge’s proposal suggests the company has failed to properly plan, design, and ensure the safe construction and operation of this proposed tunnel.

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