My main reason for trimming up some of it is the matter of trying to pull the liner tight to follow the hole I dug. Around the top edges, it seems to want to pull tight across the curves, and there's no getting it to move right. I will of course be working with folding it more once I go to finalize everything, but I also think that trimming the liner back closer so I don't have 2 feet of excess hanging out will allow the rubber to stretch more and follow the shape closer.
I'm planning on bringing the water level right up even with ground level. To start, I'll place river rocks around the edge of the pond, on top of the liner. Then behind the liner I will build up a small bank of dirt to the height of the rocks and allow the excess liner to hang over the back side of this dirt bank. Finishing off with piling more river rocks on top of everything, I should end up with a rim 4-6 inches higher than the water line, and the edge of the pond will be finished by rocks that are sitting in the water.
I finished about 3/4 of the first leg of the water pipe trench today. Got final measurements and cut & glued the riser tubes. I need to finish the depth on the last bit, and then get the pipes for this last run of electrical so everything can be buried together.
I also had to dig around that sprinkler pipe that I found running under the lower pond. I ran through the different sprinkler zones, but could detect no water running through this pipe. I seem to be finding a lot of unused pipes as I'm digging around. I ran into another when I was digging the first electrical trench - in one spot it was split along one side and full of dirt. Obviously had never been used, so I just cut that one back out of my way. I can't imagine why there are so many extra pipes that seem to go nowhere.