I see I was already beaten to the correction of how many buckets full it would take. Also, from spending 3 years digging my own pond (256' X 283' with an average depth of 7'6" - 20 feet deepest part) I can tell you that you most likely will end up needing to move over 200 buckets full to get what you want. I used a D6 6 way dozer, a Cat 955 high lift, a JD 790 excavator and 2 tri-axle dump trucks. However, your project isn't anything you can't do with your tractor. Just don't plan on doing it in a couple of hours.