Hundreds of people turned out last week to pepper local officials and employees of Enbridge, Inc. about the 60-year-old oil pipeline running under the Mackinac Straits. They wanted to know what’s being done to prevent underwater leaks, and how a rupture would be contained before it gravely damaged one of Michigan’s most beautiful places. By the end of the meeting it was clear that opponents had more questions than Enbridge managed to answer.