Regulatory and Legal Hurdles
The MDNR’s easement is not the only approval still pending. The U.S. Army Corps of Engineers must also issue a federal permit under the Clean Water Act before tunnel construction can legally start. Enbridge has stated it plans to begin work in 2024, but the combined weight of state and federal permitting requirements, along with active litigation, may push the timeline into 2025 or later. Lawsuits filed by the Bay Mills Indian Community and the National Wildlife Federation could produce court-ordered injunctions that halt the project entirely. Both groups oppose the tunnel and the continued operation of the existing Line 5 pipeline, which crosses the straits at the meeting point of Lake Michigan and Lake Huron. The older pipeline is the sole conduit for the energy resources that flow through the straits, and Enbridge has said it will keep operating until the tunnel is complete. That means the legal challenges and permit delays directly extend the lifespan of the current infrastructure, which has been in place for more than seven decades.
Economic and Energy Implications
The timeline for the tunnel carries significant economic stakes for the Great Lakes region and across the border into Canada. Line 5 transports 540,000 barrels per day of crude oil and natural gas liquids. That volume feeds refineries in Michigan, Ohio, Pennsylvania and Ontario, supplying the gasoline, jet fuel and propane that underpin wholesale fuel markets and home heating supplies in the Upper Midwest and eastern Canada. Any disruption to that flow would ripple through wholesale fuel markets and could affect propane availability for home heating during peak seasons. Enbridge has not disclosed how much of the tunnel’s estimated cost has already been spent on engineering and site preparation while it waits for the remaining approvals. The company has said it is proceeding with design work and supply chain contracts in parallel with the permitting process, but it cannot break ground until both the MDNR easement and the Army Corps permit are in hand. The MDNR’s decision will be the next major signal for the project’s schedule. Until that comes, the tunnel remains in regulatory limbo — permitted by the state in principle but not yet cleared to begin actual construction.
Background: The MDNR’s Role and the Pipeline’s Age
The proposed tunnel is an underground structure designed to house a replacement for the existing pipeline that crosses the Straits of Mackinac. The project involves land managed by the MDNR, a state agency that oversees forests, parks and recreation areas. The department’s origins trace to the late nineteenth century, when Michigan created a game warden position to regulate market hunting. By the early twentieth century, the legislature established a formal department and a commission to manage conservation. That deep institutional history now places the agency at the center of a modern energy infrastructure decision. Because the tunnel would replace an aging pipeline, the outcome directly affects the movement of crude oil and natural gas liquids that supply refineries in Ontario and several U.S. states. Delays in construction mean the older pipeline remains the sole conduit for these energy resources, extending the period during which the 71-year-old line operates under the straits. The project’s progress now hinges on a single agency’s decision, with the next regulatory milestone yet to be scheduled.
