So i got the local guys out and they bore tested down to 8 feet at the 4 corners of where my pond is going. I have 20-28% clay down to 4 foot and 60% clay from 4 feet to 8 feet. I would like to dig the pond 8 foot deep and 2 acres so I would like to test the soil down to 12 feet in multiple spots to make sure I have a good base of clay for the bottom of the pond. One reason I am concerned is that the Govt. map shows a change in soil type right at the north edge of where my pond will sit. I am thinking more along the lines of measure twice and cut once.

I spoke to the local guy and his bore only reaches down to 8 feet. Anyone have a suggestion for a good tool I could buy and dig the holes myself?