Hi Jeff.
You're describing an unusual dam. If the dam is truly 16' high and 16' thick, it a very skinny dam. Ideally, it should be 3-4 times thicker than it is high.
When you stand below the front of the dam, is it really 16' high? If that's the case, it will probably eventually collapse. If less than 16', that means some of the 16' depth is below the ground. Only the part above the ground is counted as dam height, and has water pressure behind it.
A good quick fix for the bulge is to widen and heighten the dam at that point. A few loads of clay rich dirt can work wonders to stabilize it. Increasing the height is very important, as the weight greatly speeds up soil stabilization and compaction. Even 2 feet of extra height can work wonders until it's stabilized. Once stabilized you can even out the grade.
