Tom, when I saw you had posted, I expected some in depth information and wasn't disappointed! Thank you very much! Your information and photographs are extremely helpful. I had looked at Susan's web site several times before, but had never seen her information about the Atlas bridge. She documented the information in extreme detail. I already see lots of great ideas at just a cursory glance. Thank you for pointing me in that direction too.
https://slsprr.net/features/bridges1.htm
https://slsprr.net/features/bridges1drwgs.htm
I will look over all of this in greater detail in the days to come. There will be plenty of time to review information, ask questions, and gather materials, since I know I won't be starting this project until fall or winter.