[Mr.Shenanagins]

Sure you could use it, I personally use DynaDirt. It’s made of reed sedge peat and sand. I also mixed it in with some mineralized top soil I happened to have. I would make sure to cap it real good, either with some fine mesh or landscape material and then place your cap over it (sand/gravel). I put my dirt in fine media bags, enough to contain the dirt, but still allow the roots to penetrate. Root growth is something that many people underestimate, they will penetrate anything permeable with the help of gravity.