urban, a core trench is in the center of a dam, and a "trench is dug into good quality clay. The "core" runs the entire length of the dam, from just above the full pool line, through the dam, and up the other side. This trench is filled in "lifts" of about 6 inches thick, and compacted with each layer being stitched together until above the full pool line. If your damn just had dirt piled on top of existing soil, water fill seep through and under the dam.
As for the person repairing your park lake, I have known a few great dirt movers that do as an engineer says on what, where, and how the earth is moved, but without someone telling them, they are clueless on how a pond is built properly.
Also, tracked equipment is by design, NOT compacting soil. It take wheeled earthmovers or a sheepsfoot roller/vibratory unit to get true compaction.
Finally, bentonite needs to be disced into marginal soils about 12 inches deep, and then compacted to seal. Pouring it in loose, I have never seen help seal.
Last edited by Rainman; 07/11/17 06:46 PM.
