Hosty, my pond dam top did something similar. when a dam is built, the front of the dam is where they pack all the good clay. the back is where they put the secondary stuff to make the back slope. packs ok, but not as good as clay. clay will stick together, stay put. the back fill soil, after getting moist will then pack together, fill in the gaps. when it does that it settles. so it sinks/settles. mine did that. which is good, it packs the dam in tight. it can be a 2 year process sometimes. i had the dozer come back over, then used "gumbo" grade clay to relevel the top of the dam, and reroll over the back slope to further pack it. it's an expected process, unless you could afford to use a rolling vibrator heavy duty equipment during the dam building. hope this helps. mark
