i don t know ur depth yet and it seems ur not sure yet if you just dug to the clay like i see many do and build up the sides like we do out in west texas and i have started here ur gonna need a few feet of clay i have been seeing where someone has been asking about bentonite clay and they are assuming it seals like clay its a chemical thing most people do not enter into in most topics drilling mud clay is ment to seal off permeable sandstone not sand ,, when it gets to sand layers down deep or just within the so called surface zone 300 to 1500 ft down if u hit sand or a wash out ur talking pumping in cotton, pecan hulls,,, to stop the wash out until the cement trucks get there if they must keep drilling most often ,, bentonite clay will build up a skin over say a sandstone this is to reduce loss not to seal a perment loss thats where a pond liner and or cement under sand,, i have seen only clay and i have several layers of clay down about a 100 foot step slpoe which is covered with what i call surface seeps ,, and yes i can dig down to pretty good depth and hit water if i am on a hill its just usualy right above clay layer and it can be clay or it you look really good a clay or fine fine sand,, a lot of so called sand is really a clay loom if you silt it out and clay does not matter if you are going to cover it or line it but if you are going to depend on the clay alone ,,, i have thrown in channel cat and the slim is supposed to close of leaks since they make a slime off the body and they like to back off and dig into holes in the edges of ur dam for example,,, if your depending on the rain and /or runing spring if you do not digg too deep and slpoe thesides right and seal off the upper top soil u should get a nice pond but clay is 75% aluminum and yes all ponds are clay,, yet we have an epidemic of dementia and alziemes so i am still out on this one,, i don t eat just any fish and im not here to scare everyone or argue about what i already know is a problem and my experience in the human body and the effects are limited i have heard that floride is pulling in the aluminum that is in everything into our bodies so that i ll leave for you all to hash out i know what my choices are going to be and i don t plan on changing them,, but for a nice fun hobby of catch and release and fun for the kids i run my ponds as nature laid them and they are a mix of all of the above but i am leaning towards liners over my clay covered with a few inches of sand and that liner may or may not be cement or food grade plastic,over cement or clay since even cement leaches out alkaloids that also kill the fish,, but to ask how much clay you need is a trick question since the dimensions are your first requirement and the type of clay ur gonna use,, my grey clay is and yours maybe really volcanic ash clay and its pretty good at draining since its chemicaly affected,, salt will seperate it its almost a bentonite type clay just not processed and sold to you at a steep mark up,, to know what your clay will do see if you can make it into balls and bowls,, let it dry does it stay in shape and brittle or does it crumble or never hole its shape,, you have white clay, its supposed to be really good and grey and read and all have diff properties and your water,, the fish and how you treat all of them will effect everything,, i have a nice 20 for deep dry hole on the front of the property that someone has build before i cam it never has held water,, the bottoms hold water due to its well below flood plain and its a swamp with a bout 3 foot of top soil over sand, i have watched my neighbor just sink 100000$ mid hill where i have my seeps and he has same seeps but he hauled at least 6 inches of clay in over all of his ,,,his is too big for liner i am building my newer ponds based on the liners i can find or the cement i want to afford, verses just hoping my clay and my shaping abilities will hold water
