Enbridge Line 5 was put into operation in 1953 and at the time of this writing is a 63-year-old crude oil pipeline. Which is especially concerning because it was designed for a life span of 40-50 years and has vastly exceeded its intended life span. It has leaked at least 15 times since the 1980’s, which is further proof of this fact. Most alarmingly, a 5-mile stretch of this pipeline runs through the Straits of Mackinac, one of the most biologically sensitive regions on the planet since it links Lakes Michigan and Huron. Lakes Michigan and Huron form two of the “Great Lakes”, essentially the largest source of fresh surface water on the planet.
And a crude oil pipeline runs right through them.
This website offers a great overview of what the issues are: http://www.oilandwaterdontmix.org/problem.
Also, check out the Motherboard video below which offers excellent background and context for the Line 5 issue!