4:32 Michigan Radio's Lester Graham and Bridge Michigan's Kelly House explain the economics behind Enbridge Energy's Line 5 tunnel proposal. In the decade since Line 5 emerged as an issue of statewide concern, a debate about the pipeline's future that began with concerns about an oil spill in the Straits of Mackinac has morphed to include broad questions about how oil pipelines fit into the global energy transition. Credit Lester Graham / Michigan Radio As Canadian officials lobbied a Michigan Senate committee in March to keep the Line 5 pipeline open, Sen. Winnie Brinks (D-Grand Rapids) grew frustrated with a conversation that, up to that point, had focused mainly on the immediate economic and safety implications of a possible shutdown.