TheFishGuy
( Insert something funny )
When I put my first liner in, because I didn't have enough slack, over the first few winters, along one side, the bank started to fill in, pulling at my liner. To stop this, which is similar to what you have going on, I lowered the water 6" below the area in question, then dug out the extra dirt that had slipped, but when I did this, I leveled the same area behind the liner and laid some brick, to stop any future sliding. This in essence, made my pond slightly narrower but more stable. I'm thinking you can do the same, and especially since you don't even have the water in yet, will be a lot easier.
Simply pull the liner back a bit off the 'short' edge. shovel some dirt in and tamp it to the side. You could also lay in some solid concrete slabs or create a pressure-treated (for ground usage) wood and create a verical wall. I'd just slide some of your extra dirt back in and tamp. Create a slope up to help everything stay in place. What you're doing is essentially putting back that part of your pond edge that you took out. When you do this, you'll see you now have extra liner as you've made your wall thicker and hence, the pond width/length shorter. It really isn't that hard to do, especially since you can get at everything without moving anything (except for pulling the liner back a bit so you can work).
Then of course, put the liner back. I'd think if you pack your new wall 6" thicker (pond 6" narrower), you'd gain the inches you need. See, as you fill, the water is gonig to pull the liner a bit anyhow, so you want some slack.
This is the way I'd do it as I'm not as confident in any seaming fixes.
Hope this helps.
sounds good! I do have a berm on one side I need to get rid of anyway,so I will just shove that dirt right down that darn hole.
hopefukly that will give me enough extra