That's a pretty big city. I'd start by looking
here. They probably use nationwide channels. I checked my Master Frequency File book for Augusta, GA and it shows this:
Augusta Medical Center
KJN943
Paging - 164.175
Police Fire Engineering - 168.525 (input) 166.200 (output)
Engineering - 168.000
For FBI, search 163-164 and 167-168.
For DEA, search 417-420 (especially 418-419)
The book lists a possible FBI callsign of KEY382 for Augusta
US Marshals are usually on 163.200 and 164.600. Here in OKC they do a lot of simplex ops (talkaround). Customs is usually on 165.2375. You will find a lot of great info by reading the previous posts in the Federal forum. There's only like 19 posts so far so it won't take long to look through. Many federal agencies use the same freqs.
Also, have a look at
http://mt-fedfiles.blogspot.com/