Assuming one layer is in fact clay, it looks to be ~33% of the solids. 10% clay, with excellent compaction will seal. So yes, 30%+, well compacted with a sheep's foot compactor will do well. Type of clay does matter also as some seal, swell, or contract more than others.
I'd suggest buying Mike Otto's book, "Just Add Water" and Bob Lusk's book, "Perfect Pond-Want One?". Good investments available through the home page here that are easy to understand, and can save you lots of money and frustrations!
To easily determine if clay is close to adequate get some that is damp, wad it into a oval or ball and squeeze it tightly. If it holds its shape when dropped on the ground, it could be a candidate for a pond bottom. Another hint is get a bucket or similar container, put several drain 3/8" - 5/8" holes in the bottom. Put a layer of clay on the bottom around 6 " thick and compact it with a appropriate tool such as a sludge hammer or ball bat. Fill the container with water and see how long it keeps water in the bucket. It should hold water for days if it is good compactable clay.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management
Thanks for all the great help. I took the box blade and made a small hole about a week ago at the proposed site. Its had a little over one inch of rain on it. Seems to be holding pretty good I guess. Met with NRCS this past Wed and he said they dont do soil test but the Health Dept that does septic tanks probably would. He said from just looking at the runoff and feeling the dirt that it looks like we shouldnt have any trouble at all. He did stress the importance of a well constructed core trench. I mentioned to him about incorporating Bentonite to the dirt when building and he said that if I was going to consider that, then he recommended calling the local coop and ask about a load of soda ash. Thanks
Mudball, the core trench is indeed important, but all the pond basin needs to be well compacted during construction. Don't fall into the myth that a 50,000 pound dozer will compact soils, as there is less PSI of pressure than a typical home refrigerator.
Spending a little on insurance in the way of proper bulding will save huge dollars if the pond leaks and needs to be redone.
I had a dirt pusher build a dam and the original build was $3800. The bills to "fix" all his mistakes topped $32,000.
Thanks for the reply. Yes I remember hearing about the compaction of a dozer several years ago and so I can imagine how that wouldnt help much in the way of a pond. Sorry you had that kind of trouble. Im sure you learned well from it. I cant afford to have those kind of issues. Whomever might build this pond must have a sheepsfoot roller, maybe even with aggressive fingers, if thats what they are called. Any thoughts on incorporating soda ash during the last part of construction and compaction ? Thanks
