An independent report released Thursday analyzes the risks of a worst-case scenario oil spill from Enbridge's Line 5.
Concern about Line 5 - which runs through the Straits of Mackinac - has grown after an anchor dented the 65-year-old pipeline in April.
The report says 400 miles of shoreline could be damaged by a spill - and it could cost the state up to $2 billion.
Drew Youngedyke works for the National Wildlife Federation's Great Lakes Regional Center.
He told Stateside he worries the report might underestimate the amount of time it would take Enbridge to find out about a spill - considering it took them 17 hours to detect one from a different pipeline in 2010.
"But even the numbers that are contained in this report are absolutely frightening"
But Enbridge - a financial supporter of Michigan Radio - says it has the technology to shut the line down within minutes of a pressure change.
Governor Snyder is expected to make a decision about the future of Line 5 by September.