I am not an expert (like gehajake), but agree with his post.
I could only see an "excavator only" plan being viable if you are digging out a pond in nearly pure clay that is already impermeable prior to compaction.
Even then you still need to move the spoils piles out of the watershed that is supplying the pond. Alternatively, you could compact the spoils into some landscaping features, but then you still have bare clay! That needs to have top soil graded back over your clay piles and any other places your construction operations exposed bare clay. Otherwise you will have a very difficult time establishing a good groundcover vegetation to stop your erosion on those surfaces.
There are literally dozens of photos on Pond Boss of the hundreds of erosive channels cut into the clay of people's pond basins prior to the rains completely filling the ponds.
