Enbridge has proposed tunneling under the Straits of Mackinac for twin pipelines carrying light crude oil and natural gas liquids. They would replace the current Line 5 pipelines that run along floor of the Great Lakes.
Enbridge said the tunnel could be built, and the pipelines operated, with extremely little risk. The company said a spill within the tunnel would occur once in 663,000 years and, the risk of having it ignite would be once every 169 million years,
Experts for the Bay Mills Indian Community strongly disagree. Their testimony was recently posted online, raising important questions about the project’s risk.
Five takeaways follow.
The following points are drawn from testimony by Brian J. O’Mara, founder and Principal of Agate Harbor Advisors LLC, a consulting firm that provides technical support in the assessment and quantification of environmental risk and liabilities.
1. It’s a BIG pipeline: The proposed tunnel would be 21 feet in diameter and four miles long, said O’Mara, citing an Enbridge exhibit. “The tunnel will be open and accessible to allow for pipeline installation, pipeline maintenance, and inclusion of other third-party utilities. The pre-cast tunnel lining will be “composed of six segments and incorporates high-strength rubber gaskets to limit water leakage.”
2. There are two potential explosion risks: One risk is spilling the pipeline’s flammable contents, and having it ignite. It could escape from a pinhole leak or a full-blown rupture. A leak or rupture would come out with great force. The pipeline operates at 1,440 pounds per square inch (psi), significantly more than a fire hose (typically 116-290 psi).
The other risk comes from dissolved methane in groundwater. The groundwater could infiltrate the tunnel, potentially releasing methane. “The spark generated between a person’s finger and doorknob after walking across carpeting on a dry day produces significantly more energy than required to ignite a methane/air explosion,” O’Mara testified.
3. Tunnel explosions happen, O’Mara cited the 2001 fire in Switzerland’s Gotthard Road Tunnel and the 1971 fire in the Lake Huron Water Tunnel.In the Gotthard Road Tunnel fire temperatures exceeded 1200°C, damaging the concrete and causing a 300-meter tunnel collapse. (Two trucks collided in the tunnel and a short-circuit ignited the diesel-air mixture in the air.) In the Lake Huron Water Tunnel fire, a drill bit sparked and ignited a pocket of methane that accumulated in the tunnel during construction. “The resulting blast created a shock wave that traveled with a speed of 4,000 miles per hour” and a force of 15,000 pounds psi, “that tore through the tunnel, killing twenty-two men.”
4. O’Mara is concerned about a methane explosion in the Line 5 tunnel: “My concern is informed by my direct experience working on the Milwaukee Deep Tunnel Project—a project where three workers were killed following a methane explosion,” in 1988. “My concern is also informed by the fact that Enbridge has made statements that methane was not detected in the Straits, but that position is directly contradicted by its own Geotechnical Data Report.”
5. Enbridge’s fire readiness seems inadequate: Enbridge’s fire suppression plan for the Line 5 tunnel relies only on fire-resistant concrete and shutting down air flow to starve the fire of oxygen, O’Mara testified. “This plan ignores the fact that a fire in a tunnel usually reaches its peak temperature within 5 minutes. And even if the tunnel’s oxygen were sealed off, “there would be more than 6,500,000 cubic feet of air in the tunnel, which could provide enough oxygen for a fire to burn for well over two hours.”
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One attachment included with a separate testimony was a Jan. 17, 2019 agenda for Enbridge’s “Line 5 Straits Alternatives Evaluation” kick-off. It includes brief, candid, and revealing comments by Enbridge staff.
- It cited Paul Turner, Enbridge’s “Environment Lead Scope for Environmental Review of the Three Alternatives,” as saying “Doing Environmental Impact Report as opposed to an EA [environmental assessment] or EIS [environmental impact statement] because the latter have regulatory pull. When this is released to the public, we will try to follow all required criteria, but this will not be a formally regulated report.
- During a session on Tunneling Alternatives, the notes cite “Dan C.” saying “Not sure a HAZOP [Hazard and Operability Study] will give the state what it wants. It will identify concerns, but the state wants to hear ‘the HDD has a one in a million risk, tunneling has a one in 500000. “DynRisk talked about risk in terms of dollar value… Avoid that, and talk about risk in probability. … State doesn’t care about dollar value associated with risks” “Can include the cost in the decision, but don’t state it in terms of money.”
- During the same session, the notes cite “Adam” saying: “Do what we can with what we have, and try to de-risk it as much as possible.”
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