There’s been water against a significant portion of the inside face of that earthen dam for the better part of fifty years. A cross section illustration of the dam’s construction that I saw indicated a fairly substantial concrete area running vertically through the middle of the dam also. I don’t think ground saturation is going to be the issue with this dam, bubbles or not. Erosion of spillways has been the issue and if it’s not contained, the top of the dam built onto that hillside will fail. That’s the problem. There’s also some conjecture that such a failure could possibly cascade into failure of the earthen dam itself, but I think that’s just catastrophizing due to overly involved online speculation.