The Michigan Public Service Commission approved a permit that would allow Enbridge to place a new section of Line 5 in the proposed tunnel.
The commission concluded that there is enough of a public need for the pipeline, and that the project meets the state's standards.
Commission chair Dan Scripps says a Line 5 oil spill in the Straits would be "catastrophic," and the tunnel is the best alternative to reduce the risk of a spill.
"I know some of you are disappointed with our decision, I acknowledge that, but I also want to assure you that your participation improved the process and result. The perspectives shared helps to crystallize our focus as we continued to dig into the evidentiary record."
During public comment, several people expressed their frustration with the decision, including Andrea Pierce from the Little Traverse Bay Bands of Odawa Indians.
"I have to tell you I am completely disgusted by your vote. Totally and completely. I am disgusted that these children have to sit here and feel hopeless. Hopeless. You know what it's like to be their ages and feel hopeless in our government? Seriously, you were supposed to protect our Great Lakes, protect us."
The tunnel still needs a federal permit from the Army Corps of Engineers before it can be constructed.
