I have 100% confidence in the area being sealed to prevent it from happening again if it is dug out and packed at least 24" thick with clay that is placed in 6" thick lifts, compacted and repeated.

As for the fish stocking, if you won't have Largemouth Bass in there, I would ditch the regular Bluegills, and add a mix of 50/50 Redear Sunfish and Hybrid Bluegills. Can you stock Hybrid Striped Bass in your area of Ohio?