I think I would still hammer that rock big time. We came from eastern Ky. and all they used to dig ponds was a bulldozer. They would push the dirt down from the dam and after they got the depth,they would bring the dirt back and build the dam. The only ones that would leak would be where they hit rock and didn't pack it good. No cores and they didn't compact the bottom. Soil was all clay.

Two ponds, 13 and 15 acres on the Mattaponi River.