A long running issue at the state level, the proposed Enbridge Line 5 Tunnel under the Mackinac Straits,, may be taking a twist, with a possible ‘plan B’ for the tunnel being suggested by the Army Corps of Enginneers during its review process. Here is an update on Line 5 as it stands today, prepared with the help of our MOTM ‘AI’ resources:
A late addition from federal regulators has added a new twist to the long-running debate over Enbridge Energy’s Line 5 replacement beneath the Straits of Mackinac.
The U.S. Army Corps of Engineers has released a supplemental environmental review that introduces a fresh alternative to Enbridge’s proposed concrete tunnel: installing a new pipeline through a narrow underground borehole using horizontal directional drilling. The option appeared quietly in mid-November, weeks before the Corps was expected to wrap up its permitting review.
Instead of the 21-foot-wide concrete tunnel Enbridge has been planning for years, the horizontal drilling method would use a borehole just large enough to pull a 30-inch pipeline through roughly four miles of bedrock beneath the Straits. Construction would still take a couple of years and require a long staging area on one side of the waterway, but it would eliminate the full-scale excavation needed for a tunnel.
Enbridge says the new option wasn’t their idea and doesn’t change their plans. “We are planning to build the tunnel,” a company spokesperson said this month, emphasizing that its pending application remains focused solely on the tunnel project. Environmental groups, meanwhile, blasted the sudden appearance of a new scenario, calling it a late-stage curveball that sidesteps technical and safety concerns raised in earlier tunnel reviews.
The Corps has not explained why the HDD option surfaced now or why it launched a new public comment window without its usual broad press announcement. What is clear is that the agency has pushed its final decision into next spring—another delay in a process that has stretched well past initial expectations.
The Line 5 replacement has become one of the most closely watched infrastructure stories in Michigan, balancing energy needs, environmental concerns, and Great Lakes protections. For Southwest Michigan readers, any shift in approach could eventually affect regional contractors, transportation routes, and even tourism traffic during construction seasons.
For now, the Corps is inviting the public to weigh in—again—before it makes its final call.
Civic Involvement Note for Readers
Public Comment Open Through Dec. 5
The U.S. Army Corps of Engineers is accepting public comment on the newly added horizontal drilling alternative for the Line 5 Straits crossing.
Online Public Meeting:
• Dec. 3 (virtual session hosted by the Army Corps)
Written Comments Accepted Through:
• Dec. 5
Full documents and instructions for submitting comments are available on the Army Corps’ Line 5 Tunnel EIS webpage and federal public docket.
