Hi Bill,
There is no information that I could locate on Fort Donaldson. However, I did do use one of my reference books to find out information on the Cumberland Hospital. It was located on Broad Street(which is now Boadway). As far as I can tell, Cumberland was a field hospital. My information on the Cumberland site came from James A. Hoobler's book Cities Under the Gun: Images of Occupied Nashville and Chattanooga. This book has a small photograph of the Cumberland Field Hospital. The photo is on page 22 with information under it. You can likely find the book somewere. From what the book says, the hospital held 2,304 beds. The site took up 30 acres of land.
Nathan