Frank, it sounds like a correction facility, but I do not know any federal prisons in this area, it may be coming form SC but I don't known of any federal prisons there either.
Barnwell SC has a state-owned facility for disposal of commercially-generated low-level radioactive waste. However, you are about 45 miles from Barnwell.
Are you able to hear a CC which may be associated with the freq? I.e., maybe one of these? 406.95000* 408.15000 408.55000