Hi Jeff,
Glad to hear you found suitable clay to line the pond with. Hauling it should be cheaper than buying bentonite.
A dirt buggy will not compact as well as a sheepsfoot roller, but it will do an acceptable job of compaction when properly used. It should be fully loaded with dirt and used to run over the entire area several times. The idea is to apply and compact the clay in 6" lifts, either two or three, depending on the planned thickness of the finished liner.
In my opinion, there would be no difference in compaction capabilities of a motorized sheepsfoot roller and a tow behind sheepsfoot roller.
I would recommend that after the silt is removed, you plow or otherwise scarify the area to be lined to a depth of about 4". Then mix the first layer (lift) of clay with this 4" layer before you begin compaction. This should help insure a good bond between dissimiliar soil materials. No further mixing will be necessary for the additional lifts. However, if the previous lift has crusted over, it should be lightly plowed or scarified before applying the next lift.
I hope this helps.
Rick
