Hi,
Just a couple thoughts...
Make sure the dozer takes time to compact the soil on the "dam" side...very important.
Also, a neighbor told me to keep the level of my pond up close to the top of the elevated side so that rodents can't burrow in and make dens...dens today, leaks tomorrow!
Following this advice had worked well for me. I don't have a large pond...about 80 x 60, but is does not leak!