Re: Deep enough .

By far the best source on the Clifton-Morenci mining railroads is Dave Myrick's Railroads's of Arizona, Volume III, entitled: Clifton, Morenci, and Metcalf Rails and Copper Mines (Trans Anglo Books, Glendale, CA, 1984). Over 300 pages of solid historical info, maps and photos.
Five of the 20" gauge locos still survive: One in Clifton, one at Morenci, one at Safford (disassembled??), and two in Phoenix. Not bad out of a total of 15. All were H. K. Porters, 0-4-0T to 0-4-4T in arrangement.
I visited in the early 1960's and got a look at old Morenci before the open pit gobbled it up. The pit itself was a big diesel and electric traction operation, remarkable in its own right. Myrick covers that, too.
Southwestern rail history is full of great subjects for study and modeling, if you look for them.
Vern