The pipeline could have gone around the Missouri River easier than going under it twice. Then the only complaint would have been CO2 in the air rather than pollution of the last good source of clean water in the country. Welcome to the sociology of corruption.
Near the Missouri River are hilly river bluffs. A few miles east is the James River valley, which is flat as a pancake. There is already a pipeline from the Canadian tar sands going through the James River valley. The Dakota pipeline could have taken totally flat ground from Stanley North Dakota to Iowa with very little increase in length.
Opponents of the pipeline will not suggest going around, because then they would be promoting carbon dioxide in the air. For the sake of fraudulent science, they are avoiding a tolerable solution. Let the pipeline be built on flat ground away from the Missouri River. The James River has very little water flow and will not be polluted when the pipeline breaks due to the flat ground around it.
The surface of the Missouri River is 400 feet below the surface of the ground. That means a spill anywhere near it will run into the river.