Pigs do well turning compost when left with it in a confined area. Also, when confined in an area that needs rooting, they will sometimes root more than a foot deep. This will take care of weed problems such as thistles.
Pigs have reportedly been used to seal a pond. E.g. consider a pond that has a fair amount of water running in it, but never gets full. The plan would be to fully drain the pond, divert the water, put a fence around the pond and run pigs in there for a month or two. The theory is that shape of a pigs hoof packs the soil so tight that water cannot penetrate (another reason to not have pasture pigs: apparently the water on the pasture will start to run off instead of soak in). So when we take the pigs out, the pond should be completely sealed and fill properly.
Speculative idea: Using this same idea... creeks sometimes dry up in patches, and the water runs underground. To bring this water to the surface, it seems that the wisest thing to do would be to run pigs in the creek during the time that the creek is dry (or near dry).
For pictures, check out: pigs turning compost at richsoil.com.
For more information from people with experience with pigs, check out the thread at: permies.com