Column: Why the Enbridge Line 5 tunnel is a pipe bomb at the Straits  

April 8, 2022 4:11 am

Mackinac Bridge | Susan J. Demas

The sordid details of Enbridge’s Line 5 in Michigan reveal at least 33 spills, along with at least 3 anchor/cable strikes that had the potential to cause a massive oil spill.

We’ve been lucky. Incredibly lucky. But our luck will run out.

Enbridge proposes to build a tunnel for Line 5. They assure us — falsely — it will eliminate all hazards. The tunnel will, unfortunately, introduce new hazards — hazards that are even more insidious.

These hazards have been confirmed in a new study by Brian O’Mara (B.S. in geological engineering) and myself (M.S. in chemical engineering, P.E.).

Enbridge’s tunnel proposal has been fraught with issues from the start, including its failure to conduct enough lake bottom borings to appropriately assess the presence of methane and/or hydrogen sulfide. But even with their incomplete survey, methane was detected in 20% of the lake bottom borings and hydrogen sulfide is often found with methane. 

Both substances are explosive. Hydrogen sulfide is also extremely toxic. There’s’ a real-world example of that danger right here in Michigan: In 1971, 28 tunnel workers were killed when they hit a pocket of methane while building a tunnel under Lake Huron near Port Huron.

Even if we look past the alarming problems faced during construction, the risks don’t go away.  When highly volatile, flammable substances are transported in a pipeline inside a tunnel, engineers refer to the tunnel as a “confined space.”  The term is well chosen and very descriptive.

Enbridge ships propane and butane through the pipeline roughly 20% of the time.  When released, they form a vapor cloud that’s heavier than air.  The cloud will accumulate at the low point in the tunnel, awaiting a source of ignition which is always present.  

A single one-eighth–inch hole in the pipeline will release, within 19 minutes, propane equivalent to 345 pounds of TNT.  What will this do to the pipeline, the tunnel, nearby residences, and any vessels traveling above?  It will be an environmental and economic disaster. Even worse, there likely will be fatalities. 

Line 5 map | Laina G. Stebbins graphic

While the probability of an explosion/detonation is very low it remains finite, making the consequences horrendous. Engineers express this as: Risk = Consequences x Probability. The equation clearly states that Risk is made of two components, not just one. Risk cannot be ignored just because probability is low.  

By way of example, let’s consider the nuclear reactor disasters at Chernobyl and Fukushima. At these sites, and many others, they operated on the premise that since the probability was so low it could be ignored. There would never be a problem. They were wrong.

Without justification, the assumption has been made that since the pipeline is in a tunnel, there is nothing to worry about. The probability of a leak in the pipeline is so low a disaster will never happen.  In other words, we don’t need to worry about the consequences. 

It’s bad logic. And therein lies the fatal flaw. 

It is the sort of reasoning that led to the nuclear reactor disasters at Chernobyl and Fukushima, as well as numerous other disasters, such as the Port Huron tunnel disaster.

A leak of butane or propane inside the tunnel can occur. When that happens there will be a detonation or explosion.

The entire state of Michigan will be affected. Pollution of the Great Lakes, violation of tribal agreements, loss of tourism jobs, commercial and sport fishing ruined, beaches ruined, Mackinac Island “shut down” — the list goes on and on. Michigan, along with Wisconsin and Ontario, will pay the price.

We cannot afford to guess and find out. It will be catastrophic. The tunnel must not be built.


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Gary Street
Gary Street

Gary Street has a B.S. and an M.S. in Chemical Engineering and is a Registered Professional Engineer in Michigan. He spent 30 years at Dow Chemical in various engineering and management roles. The bulk of those years involved the resolution of environmental issues. After retiring from Dow, he co-founded Midland Engineering, a consulting firm. His work has involved a wide variety of environmental issues throughout the U.S. He recently presented several lectures on current environmental challenges at Michigan Tech, is the author of numerous technical papers, and co-author of the textbook, “Applied Chemical Process Design." He continues to work with several nonprofit environmental organizations.