I haven't checked for specific info on your topic, but I do know of a few good sites to begin with. They are good places to reference info on native american topics and they include many gov't links as well. Here they are:
There is a lot of info on the nuclear sites, which may or may not be of help. One site/study may be of help: http://www.em.doe.gov/bemr96 (USDOE 1996 Baseline Environmental Mgmt Rpt).
Have you obtained the federal facility locations (on map?) and overlain these over tribal lands (map) yet? I assume so. Anyway, just a few thoughts. I hope they help.