Yeah, that's too steep. You might want to think about cutting a part of the bank back to 3:1 then putting the liner in there. That will allow the equipment into the pond basin to pack dirt there. BTL Liners have some installation videos on their website.

www.hoosierpondpros.com

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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).