The U.S. Army Corps of Engineers on Wednesday approved a controversial plan by Canadian energy company Enbridge to build a protective tunnel around its aging Line 5 oil pipeline running beneath the Straits of Mackinac.

The federal permit is critical for the Line 5 pipeline project, moving the $500 million-plus project one step closer to construction. 

It comes despite the corps' own environmental analysis in May, which concluded that tunnel construction could destroy wetlands, harm bat habitats, disturb aquatic life, and potentially trigger an underwater explosion.

The corps, which fast-tracked the project in April following an order from President Donald Trump to expedite energy projects, said Wednesday the application "complied with all applicable federal laws and regulations."

Adam Telle, assistant secretary of the Army for civil works, called the approval "a great success" that will "advance the President’s energy dominance agenda for America."

Enbridge now only needs a permit from the Michigan Department of the Environment, Great Lakes, and Energy. Environmentalists have been pressuring the state to deny the application.

The Line 5 pipeline has operated since 1953, transporting crude oil and natural gas liquids between Wisconsin and Ontario, Canada. A 4-mile segment runs along the bottom of the channel linking Lake Michigan and Lake Huron.

Concerns about a catastrophic spill escalated after Enbridge revealed in 2017 that coatings on the line were damaged. 

A 2018 boat anchor strike further stoked fears. Enbridge officials maintain the segment is structurally sound, but agreed to build the tunnel in a 2018 deal with then-Gov. Rick Snyder.

Conservationists and several Native American tribes have opposed the tunnel, demanding a complete shutdown of the pipeline. 

The project is entangled in multiple lawsuits, including challenges from Michigan Attorney General Dana Nessel and Gov. Gretchen Whitmer, both Democrats, who seek to stop the pipeline's operation in the straits.