Don't be hard on yourself. I'd bet the majority of pond leaks are due to not properly compacting the whole pond basin, or not having good enough soil (i.e. clay) to compact in the first place. My pond? It's a combination of both of those things.

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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).