The CEO lays it down:

"Well, first of all, I think this is well-known by now. We’re not on any Indian property at all, no Native American property. We’re on private lands. That's number one. Number two, this pipeline is new steel pipe. We’re boring underneath Lake Oahe. It's going to go 90 feet to 150 feet (27.5-45.7 m) below the lake's surface. It's thick wall pipe, extra thick, by the way, more so than just the normal pipe that we lay. Also, on each side of the lake, there's automated valves that, if in the very, very unlikely situation there were to be a leak, our control room shuts down the pipe, encapsulates that small section that could be in peril. So, that's just not going to happen. Number one, we’re not going to have a leak. I can’t promise that, of course, but that — no one would get on airplanes if they thought they were going to crash. And, number two, there is no way there would be any crude contaminate their water supply. They’re 70 miles (110 km) downstream.[92]