I have built two swimming pools that I sub contracted out; the second one I considered digging with my Kubota L-35. As one poster mentioned, a lot of hard hand labor in shaping maybe involved, which scared me away. The guys that dig with excavators for swimming pools are artists. It took them less than a half of days labor to dig a 24'x40'x9' pool and was ready for the rebar! This was a "mountain lake design" also. Another factor is working close to the banks edge, which could give way swallowing your new L-39, depending on soil type? As you try to dig from inside the hole, you will be challenged with traction trying to back out, even in 4wd. Unless things have changed price-wise in the past decade greatly; I would get some bids on the digout first, then see if it's worth doing it yourself. There is a mountain of dirt to be removed, and very time consuming with your L-39, but not impossible. The digging was the least expensive part! Even 100 yards will be 200+ trips. Good luck on your decision!