Michigan environmental regulators have approved critical permits for a massive, first-of-its-kind tunnel designed to house the controversial Line 5 pipeline beneath the Straits of Mackinac, marking a major shift in the state's oversight of the project.

The Michigan Department of Environment, Great Lakes, and Energy (EGLE) announced the approvals on Wednesday, moving Enbridge Inc. closer to constructing the 4.5-mile Great Lakes Tunnel.

The decision departs from Gov. Gretchen Whitmer’s previous high-profile efforts to shut down the pipeline, which carries oil and natural gas liquids between Lakes Michigan and Huron.

Under the plan, Enbridge will use a boring machine to carve a pathway through rock 60 to 250 feet beneath the lakebed.

The company claims that placing the pipeline inside the concrete tunnel will virtually eliminate the risk of an oil spill in the sensitive waterway, where the existing dual pipelines have previously suffered damage from ship anchor strikes and worn protective coatings.

Enbridge spokesperson Juli Kellner called the state's approval "an important step forward" to secure regional energy supplies while protecting the Great Lakes.

However, the project faces fierce resistance from environmental and tribal groups. Opponents point to ongoing legal battles and a federal review process they argue has been rushed.

"This betrayal puts our Great Lakes at risk for the sake of a pipeline that serves foreign oil interests," said Beth Wallace, climate and energy director for the National Wildlife Federation.

Wallace noted that federal agencies have acknowledged the project could cause irreversible cultural and environmental damage.

Tribal nations have also condemned the fast-tracked oversight. Several Great Lakes tribes previously withdrew as cooperating agencies from the U.S. Army Corps of Engineers' review, alleging the federal government failed to honor treaty rights.

Tribal advocates also criticized a controversial land swap in Emmet County that allowed Enbridge to bypass a comprehensive historic review on culturally significant land.

The project is not yet fully cleared. Enbridge must still secure a federal permit from the Army Corps of Engineers and a separate wastewater discharge permit from Michigan regulators.