So this is going to be my third attempt at building a pond and getting it to hold water. I am in central Arkansas at the foothills of the ozark mountains. I have had two previous by two different pond builders and neither has came back to make good on their work. Both times no contract in writing so my question is to make sure I get reputable builder this time which I will going with a referral from Mr.Lusk is it a common practice for pond contractors to not provide a contract in writing with a guarantee or should a reputable contractor be willing to provide one?

From my understanding of it all, you will not get anyone to agree in writing to guaranty a pond will not leak. But best of luck to you on your pond building.

Were they properly cored and compacted?

The first time it was not properly cored...This time I will having heavy clay brought in to line the bottom and inside of dam.