Okie, I think, after considrering everything, that I would probably go without the NRCS guy. I believe that I would get some Topo maps of the area and try to calculate my own watershed. Maybe find a Geologist to help. Then, I would find a dozer guy that knows how to shoot levels and grades; or maybe just hire an Engineer.
If you go over the guys head, he will, at best, be an unwilling participant.