Hello F1sh,

I'm not one of the experts on this board, but have read enough to maybe impart a little guidance. Earthen dams must be keyed, compacted, and constructed of a correct soil composition. It would be very difficult to sufficiently compact your dam with an excavator alone, most of the pros reccomend a sheeps foot roller. What type of soil used in the dam, need correct mix of clay and dirt.

Many posts refer to "seasoning" of pond. Oftentimes ponds exhibit increased water loss early in their lives, and settle as time passes and the soils compact and saturate.

There art a ton of posts on pond building, check them out, very interesting.

Rgds,
Pedro