Rio Grande SD50 5502 shoves on the rear of a coal train at Leyden, CO, early 1990s (Bob Jordan) Rio Grande SD50 5506 near Denver, early 1990s (Bob Jordan)
D&RGW 5506 making up the rear (or lead) of a switching move near Denver, early 1990s (Bob Jordan) D&RGW 5513 and four other units lead a coal train through the mountains, early 1990s (Bob Jordan)
There's no place on the Moffat that I know of where the main is separated by that much elevation from the siding. It's not Bond where the Craig Branch does divert from the SLC main on a 2% grade like this, though. Could this be Tennessee Pass? I know who will know, on a Facbook group of which I'm part. could I share the image there? This Bond, you can see twin mains on the lower line.
Well that's quite a way off then! But it is good to have that pinned down. Two views of Rio Grande F7A 5574 at Denver, circa 1970 (Bob Jordan)
Rio Grande F7A 5574 at Denver, circa 1970 (Bob Jordan) A mixed bag of Rio Grande power (a F7A, two SD9s, a F7B, a GP7/9 and another F-Unit) at Denver, circa 1970 (Bob Jordan)
Most railfans would call this a "Dog's Breakfast", but D&RGW fans know this lashup to be a "Perlman Mallet". Solid strings of matched F's on freights were not common in D&RGW country. Alfred Perlman, a D&RGW man in many roles up to executive VP, mixed lashups of solid F's up with GP7/9 and SD7/9 units to keep tonnage moving. Typical Perlman mallets were A-B-B-A Fs with an early Geep added for a total of 5 units.
Kind of like what the Milwaukee Road did, with two Joes and one or two GP9's, or an EF5 Boxcab set (4 motors) and a GP9. Those Geeps were originally nicknamed "Sputniks".
Rio Grande F7A 5731, Denver, CO, circa 1970 (Bob Jordan) The nose of Rio Grande F7A 5734 at Denver, circa 1970 (Bob Jordan)
As for an answer to your question, Minesweeper, not routinely unless in the shop for maintenance, is my guess. The fact is, the D&RGW had loads of tunnels, so soot and grime were a part of life.
It looks weird for a line that has "soot and grime as a part of life" to paint their stock in light colors.... But OK then, good for the wathering guys...
Rio Grande and Rock Island power meet at North Yard in Denver, circa 1970 (Bob Jordan) Rio Grande F7A 5741, Denver, CO, circa 1970 (Bob Jordan)
Rio Grande F7A 5764, Denver, CO, circa 1970 (Bob Jordan) Rio Grande F9A 5771, Denver, CO, circa 1970 (Bob Jordan)