Hurray! I’ve been back to digging the pond the last couple days, and today I finished the bottom layer! I hit clay soil at about 2 1/2 feet down, and went a little deeper in one spot. For those who were wondering about the water that showed up in the bottom, I learned, after consulting other folks, that it’s probably not really a bit deal. It might possibly lift the liner in the spring a small amount, but on the other hand, the water in the pond might have enough weight to counter that. In any case, over the last several days of not much rain, there is no standing water, though the soil I’ve dug out has been damp.
So I ended up with four levels: first level all around the edge for planting (at about 10 inches down), second for a step, plus another spot to plant pond lilies, third another step down, and fourth the very bottom. The bottom is about 2 ft. 10 inches feet deep, though more like 2 1/2 feet from the top of the water once filled, since there is an overflow channel about 4 inches down from the top. I decided to let the clay soil be my guide for stopping at that depth. The very thin white line you can see across the pond is my measuring-depth-device–a string anchored in the ground at each side, and then another string looped onto it, marked with knots at each foot, and weighted so it hangs down.
It has been a lot of hard work to do the final levels, because each damp shovel-full had to be carried up the steps to the top step to put it in the wheelbarrow. And then, when I wheeled it all to the mound where it was going, I had to shovel it onto the mound. (Eventually I will add compost to the mound, and plant some sort of ground cover.)
The next step will be to cut old carpet into strips, to layer over the ground to keep roots from coming through, and to protect the pond liner. And surprisingly, there were small bittersweet roots all the way down to the bottom level. I have a pile of old carpet that I collected from willing volunteers (via Freecycle and Buy Nothing) last week, that is sitting on the patio, waiting for me.
But for now, I am coming inside to rest, with sore muscles but a happy heart. It has been so satisfying to be digging down into the beautiful earth, imagining a place for water.