Additional safety provisions would be implemented on the existing pipeline while the tunnel is under construction. The measures include having staff present at Line 5 capable of shutting it down within 15 minutes if waves reach a certain height, setting aside $1.8 billion to be used in the event of a spill and installing cameras in the Straits of Mackinac to monitor ships in the area and prevent them from dropping their anchors.

The agreement was not a complete surprise. At a press conference two days prior to the announcement, Michigan Sierra Club chair Anne Woiwode said there was a "strong possibility" that Snyder would announce a deal with Enbridge within the next few weeks.

Sean McBrearty, a campaign organizer for Clean Water Action, said at that press conference that the construction of a new tunnel does not go far enough in protecting the Great Lakes.

“In the waning days of his administration, Governor Snyder is trying to fast-track approvals for Enbridge to build an oil tunnel through the straits of Mackinac. An oil tunnel through the most sensitive part of the Great Lakes ecosystem is not a solution,” McBrearty said. “Building a tunnel through the Straits of Mackinac would not only be unnecessary and take too long to complete, it would also come with a significant risk of explosion. If electrical utility lines are run through the tunnel as well, everything needed to create a massive explosion under the Straits would be present.”

Democratic Attorney General candidate Dana Nessel said she objects to continuing to run oil through the Great Lakes, noting that a potential spill could be the biggest in history.

“The only way we can truly protect the people who actually live in this state is to, firstly, shut down Line 5 and shut it down as quickly as possible. … I object as vigorously, as tenaciously as possible to building such a tunnel as we are hearing about now,” Nessel said. “Both the governor and the attorney general are shirking their responsibilities, their obligations in those capacities. It’s your job as (attorney general) to defend the public trust and defend our natural resources."

“You look at Governor Snyder, doesn’t he already have a sordid-enough legacy to leave this state when it comes to contaminated water,” Nessel said. “Does he really need to add this to his legacy?”

Snyder said in a statement that the deal announced Wednesday will “result in eliminating nearly every risk of an oil leak in the Straits and provide added protections to the Great Lakes.”