I had trees on the dam and back of the dam of my 1/4 acre pond, plus lots of large trumpet vines. We dozed the trees off the dam, cut the ones behind, and reworked the pond completely inside. We did not rework about 2/3 of the dam. I fear roots were left inside the dam, and even with the clay packed on the pond side of the dam, the pond is still leaking, and seems to be getting slightly worse with time. If I had to do over, the entire dam would have been reworked, at least from the core inward toward the water line.