I mixed in the rest of my informal
compost pile to form the
berm. I want it to drain, just drain slowly. so no, I didn't line it with the heavy clay stuff I dug out. I am not sure at this point wether the rocks will be
enough to prevent erosion of the high side wall. I suspect I may have to remove them and place some sort of weed barrier or liner just on the steep part to prevent erosion. After this rain fall I will evaluate the erosion factor, make it bigger and deeper and tweak the grade around it to better direct the water into it.