I'd say it's a very bad idea.
How big a bucket will you find in the very largest skid steers? Less than a yard, but lets pretend you can find one with a one yard bucket. You have to pick up that yard of dirt, carry it to the dam, drop it, spread it and compact it, then return for another load. The machine isn't designed for hauling dirt, just loading it, so it's very in-efficiant.
A decent sixed dozer can move from 3 to 6 yards at a time. For maximum dirt movement, you want one with a fixed blade. 6 way blades are a compromise for moving dirt as they also have to shape it.
The real question is how far do you have to move the dirt? The dozer will do a good job for a short distance, but after 300 feet, it's not a good idea either.
If further than that, you really need to consider a way to haul dirt. Dump truck and loader work well, but the best way is to get a belly scraper.
Do some measurements and figure out how far you have to move the dirt and how much dirt you need to move. If it's just a small dam that needs a few hundred yards, than you can do that with just about anything. If you need to move thousands of yards of dirt over any sort of distance, than you're just throughing money away doing it the hard way.
Good luck,
Eddie
