I'd say no. Just dug down a few feet deeper than the ponds planned depth and compacted as the dam is built up.
I'm sure someone has a more technical answer.
But the way the soil is down here in Alabama we have plenty of clay.
If you are't lining it, then you need to go down to an impermeable layer--either bedrock or clay. Sepp goes down to bedrock so he doesn't have to use any liner clay--a huge deal since he is usually building LAKES (much bigger than the average pond).
"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
"Preach the Gospel always, and if necessary, use words." --Francis of Assisi.
"Family farms work when the whole family works the farm." -- Adam Klaus
We should throw him a surprise party. It will cheer him up. We can use this tiny ad: