Long time browser, new member/poster here. I am developing several natural water table ponds on my property. I am aware of the issues and opinions regarding these, after several test holes and observations my situation appears to be the following. Solid clay anywhere from almost surface to 30' deep. In the low areas that I am digging out there is several inches to 1 ft of black muck then 1 to 3 ft of what appears to be a fine gray sandy material, then a brown sand that starts out soft and gets harder and darker as I dig and eventually hit clay, depth varies. The water appears to flow through the ground of my property through this grey sandy soil which is in all of the low areas. This soil is the oddest thing, it feels like sand when dry, if submerged in water it is soft and you will bury a piece of equipment quickly, if you place this soil on top of drained brown sand it holds water. So in the spring the water table is high filling the low spots then recedes leaving the water on top of the grey sandy soil and the muck. If you dig through the muck and grey soil it will drain into the sandy soil below. This grey sandy looking soil has small brittle white chucks in it old seashells, limestone, etc? not sure. I have asked some of my neighbors about it and the one old timer says it is from when Michigan had the great forest fires years ago. FIL says it is just sand mixed with clay. Anyway Any thoughts on what kind of soil this is or if anyone has any experience with it.

Dave

From your description, I'd say it's sand mixed with clay. But maybe provide some pics if possible.

I agree with JohnnyBoy, probably sand mixed with clay.

What matters the most is HOW it is mixed. Based on your description, there are probably clay laminations (layers) in that soil. In some situations very thin clay layers are capable of sealing pure sands that exhibit greater than 25% porosity and excellent permeability.

Even more importantly, experimental results always trump theoretical results. If it holds water in situ, then DO NOT disturb that horizon in the places where you want it to seal your pond. (It is possible that once you disrupt the current layers, you will not be able to re-seal those layers - no matter how much compaction you use.)

Good luck on your new pond projects!