Josh, I finally managed to dig out those back issues of MR and RMC. I have MR back as far as 1953, and RMC only as far back as the early '70's, so I have nothing on the early RMC articles, from March 1951, to January '58. The earliest reference in MR is April, 1962, and that is the article that I mentioned earlier. Subsequent articles, in both MR and RMC are mainly layout mini tours.
The article on the bridge is four pages, with some "in progress" shots of the model and a couple of prototype photos. The bridge is a multiple span through truss-type bridge supported by concrete piers, with a double track rail line on the main level and a highway on the top of the trusses. The model, based on the prototype Southern Pacific bridge over the Pit River Canyon, is built in O scale and is about 11' long. Most of the model photos show the site preparation - benchwork, building the surrounding terrain, and installation of sheet of glass used to model the "water". The lone photo showing the bridge itself under construction features a loco with a flatcar carrying bridge girders on the lower level of the bridge, and a mobile (truck-mounted) crane on the upper deck, hoisting a girder into place. There are lots of workers in the scene, which also includes a safety net made from a nylon stocking.
The construction of the terrain is quite interesting: 1"x4" benchwork, with burlap stapled over forms, then covered with house plaster mixed with an equal amount of shredded asbestos. After the terrain was coloured, real dirt and rocks from the prototype site were added, along with coloured sawdust "grass". Evidently, Mr. Humann was unaffected by the asbestos, as the last article catalogued, in the April '93 issue of RMC, shows him looking quite hale and hearty, with mention made that he was 80 years old.
His layout, built over a period of 42 years by him and his wife, was declared "finished" in this last article. It occupied a 36'x60' basement, and had over 900' of track. They also operated a full-size live steam railroad on their ranch, near Gerber, California. I don't know if this operation is still in existence, as both of their children were also quite involved in the operation.
Wayne
Wow thanks Wayne for all the info.