Thanks for the link. Over 6 decades old without a leak.
http://www.enbridge.com/InYourCommunity/PipelinesInYourCommunity/Enbridge-in-Michigan/Line-5.aspx
It is a multi-use line. They send propane through the same line as well.
One of the good things Rick Snyder did was put pipeline safety oversight in the hands of the State Attorney General and its proven to be an effective non adversarial relationship. Embridge, the DEQ and other relevant agencies conduct inspections together and all reports go directly to the AG’s office.
2 years ago during an inspection of the line under the straits they found two missing support struts. Not only did they replace the missing struts, they doubled the number of existing struts without being required to do so.