janine9620 said:
Do you think if there was a cave in it would be able to push the plywood into the pond?
Yes, otherwise, it wouldn't cave in.
I want to go just a lil less than the 4 feet width.
Do you mean depth, or are you wanting a 4' x 4' pond?
I was thinking of bracing with rebar metal steaks in front, then the carpet over them.
I really don't have the knowledge or experience to give you a solid answer on this, but I think that with heavy plywood and enough rebar, it might hold, at least until the rebar rusts away or the plywood rots or your pond is empty for some reason and it rains. There's a reason why they don't build houses this way, though, eh?
It might help to replace loose soil with crusher run (aka "crush and run" -- the gravel they put under roadbeds). Once you tamp it down, it generally won't move much. But be very cautious about using crusher near the surface. It's too sharp for the liner and way too alkaline for the fish.
With the clay we have here, it's usually the bottom that gives way, rather than the top. Is that how it is with your soil?
I've heard of people stabilizing the soil in mid-depth ponds with some kind of weak concrete mix. But I don't think that's going to work for for straight, vertical walls. Cinder block would, if done properly.
I gather you're on a tight budget for this project, but consider the value of your time. You could put a lot of hours into this and have it fall apart on you, requiring even more hours to fix. Better to get it right the first time, even if you have to wait until you can buy or scrounge what you need.
