We finished digging the hole, then added rocks to the bottom and wire mesh around the border to stabilize the walls.
We took a sturdy garbage lid and epoxied in the PVC pipe. TW painted both for me too. The handle on the lid was just glued and didn't last long with the dogs, we'll have to screw in a handle one of these days.
This is what is looks like. Our very own Poo Hole!