Guys, I think my intent was taken wrong here.. If starting a new pond basin in lean sandy clay or sandy loam, I can get a near 100% seal using my techniques as compared to using Bentonite. I can seal a 15' 1 acre pond for about 3,000$ for the material.
What I do after the seal is completed is what holds the pH steady. My pond is going into year 4. My pH is 7.8, my hardness runs about 120-140.
The trick is a 1 foot blanket of dirt over the top with riprap shores down to 3-4' in many areas, a lot of gravel and sand substrate.
My point of what I'm saying is there are other ways to seal a basin than bentonite alone. In my neck of the woods, the closest supply of high-end Bentonite has to be trucked out of Utah and besides not working good in a high fluctuation pond, it's cost makes it a bad option here. I think each area has soil types that bind in different ways with different compounds but the one constant is regardless of what is used, it has to be used properly, with proven installation/incorporation methods to have the best chance.