When I built my pond, I cored it because I thought that was important to stop it from leaking. Laying one layer of dirt over another creates a seam that would be easier for water to find a way through it then the virgin soil below the dam, or the compacted soil above.
After finishing it, I was in a discussion about it with a soils engineer who told me that the real reason to core a dam was that the weight of the dam is what holds it in place, and the core improves the integrity of the dam by locking it into place "AND" adding to it's weight.
Depending on how much water height you are holding back, dictates how much weight you need in the dam. The angles of the dam are figured in increasing the overall weight of the dam, and not some angle of holding back water.
The same is true with how much freeboard the dam has above the water. It's not so much to hold back extra water, but to increase the amount of weight of the dam to hold it in place.
I did it right, but for all the wrong reasons.
Eddie
