Thanks for the replies guys.
John, I agree it should have been cut lower (someone else started to cut it, don't know who or why). The good news is they probably didn't get past sap wood.
So my plan after consulting with you guys: dig down and cut as low as I can, buck up under the burl (get a 6 or 7' section that includes the butt), buck up again at first limb (get a 9 or 10' section that includes burl), saw burl section down pith and examine burl area. If its sound, slab saw into planks. If not, cut away burl for turnings and pray there's figure in the rest.