Sorry I can't help you much with this. The excavator who did our two ponds (and much other work for us) is no longer able to work due to Alzheimers. Of the two other excavators we have used since then, one is now disabled with a broken back (and if he wasn't, I wouldn't endorse him) and the other has only small equipment (mini-hoe, skidloader) which was sufficient for the work we had him due (culverts) but wouldn't do for a pond.
One possibility are (is???) The Ventura Brothers, who are out of Newark in Licking County. I do not have any idea if they do ponds, nor do I have experience with them, but they are the outfit that bought the heavy equipment from our favorite old excavator - so they should have the machinery. I do know that they have been in business for at least 20 years (maybe longer).
Good luck with your search. If you find someone who proves good, please let us know. There are at least two other Central Ohio members who have been looking for pond excavators. And you never know when I might decide I need another pond or two.
P.S. If possible, get references of prior ponds any prospects have done and check with the owners to see how the job went. If someone has done multiple ponds but they all leak due to improper dams, you don't want them. Fixing a dam that wasn't cored right may be possible, but will cost more than doing it right to start with.