Recent pipeline spills have made people aware that underwater oil pipelines carrying corrosive tar sands oil could pollute the Great Lakes.

Can we believe the claim that these pipelines have never leaked? How would they know? If the pipelines ran across the bridge, leaks would be visible. Putting the pipelines underwater allows leaks to go unnoticed. They are now planning to use robots to inspect the pipelines 4 times a year. That means 90 days between inspections. I suppose that until now inspections have been even more infrequent.