Tracy, your earlier suggestion for the pond on sandy soil is a good one. Bentonite mud from a drilling company will no doubt decrease filtration on a sandy bottom and the solution may be an acceptable one that provides what is sufficient for the poster's needs. I need to add my thumbs up to it.

Soda ash has been used for a long time to seal pond bottoms but the soil must have clays to work. As Snipe mentioned, it depends on the soil. In soils (with clays) where the clays are bound in granules that don't stick together well, the soda ash disperses the clays making them behave more like bentonite does. They become mobile and plastic. In a soil with little clay, the soda ash would offer much less and perhaps no benefit. An example of such soil is my father in law's soil which in every practical sense is almost nothing but sand and organics .

Where clays that are already dispersive are available for lining the pond, there is no need for any sealing additives at all. In these cases one might need to offset the clay's dispersive properties in order to lower turbidity.

Last edited by jpsdad; 01/11/21 10:05 AM.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers