Brettski already described the tool I was thinking of but I should add that when digging my pond we found a 6" clay tile around 7' deep. This was surprising because these were hand dug. We are guessing that there had been an eroded ditch where they dug and then 200 years of farming filled it back in. The old tile was about 90% full of dirt and didn't appear to be functioning any longer. To be safe we dug out about 6' of the tile and packed the trench with clay.



"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." Stephen W. Hawking