My pond (about 30 X 30 ft.) was dug with a backhoe 20 years ago. The levee side (about 5 or 6 ft. high by 30 ft. long) is clay soil and was packed down by the backhoe. Over the years critters have dug into the levee wall from inside the pond, plus I've had some over-spill erosion.

I believe my current leak is actually seepage from critter burrowing. In the past I've managed to plug a few holes that I can see when the water is low in late summer. I'll do the same this year, probably in late July or August.

I'd also like to enhance the levee with a retaining wall to control burrowing. What would you suggest? Rip Rap? Concrete blocks? Something else. Aesthetics is somewhat secondary to cost.