Welcome to the forum! It looks like a pretty good sized project.

I'd do some reading on how to properly build a dam, core trench and all. My fear is that if you just use the dirt from pond #2 to rebuild the dam for pond #1, you might have it fail again. Do you know why it failed?

Proper compaction and proper soil moisture are some of the ingredients to building a pond the proper way (read that as in minimizing problems down the road).

If it was mine, I'd do a lot of digging for information as to what type of soils I had, and read up on pond construction. From my experience digging my own pond, the mini-excavator isn't near big enough.

With that said, I'm not a dirt guy, and I don't know the soils down your way.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).