I can't help with a contractor in the area, sorry. The only ponds that I know of that have little to no leaks are ones that have been built in good clay soil, or have had clay properly compacted 18"+ thick everyplace that the water would touch.

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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).