With the dewatering commenced and lots of holes to give feedback on how well things were going, gears shifted to cutting off any sources of the water problem.
The dam was first since the holes were most full closest to it. A quick inspection showed that the expansion joints that are filled with bitumen had cracked and were very capable of creating very large leaks if the dam was filled to the brim as it had been.
Quick solution was to pump most of the water out of the dam and to start repairing the bitumen joints.
This was accomplished by removing the grass, cleaning away the dust and algae, then painting the concrete with a first coat of bitumen based sealant. A membrane/cloth was then placed over the offending joint and coated with another coat of sealant.
A final coat was applied and then the wait of 10 days for curing.
Final result is water in the dam without leaks and able to irrigate the new trees.