The Hartwell interchanged originally with the 50 mile Elberton Air Line (also 3-foot gauge) between Elberton and Taccoa on SRR. After EAL was taken over by SRR (I think it was actually CofG), it was extended for a back door entry into Augusta.
I rode in the SW1200's cab once when I went up to ride the ex-Reader 2-6-2 and the crew gave us a cab ride switching freight cars instead. The SW1200 was ex-NYC.
The Hartwell had a "branch" that went all the way to Hartwell Dam during construction. They extended the main.
Contact me back channel if you want to get together and "be narrow minded".
Doug.