OC MP62: On page 15 of Gordon Chappell's book "Logging Along the Denver & Rio Grande" there is a series of maps created by Ernie Robart. One of them details the Biggs Spur you refer to at MP 348.41. I states that , at that location, there was a residence, bunk house, cook house a sawmill and two sidings. There's no mention of a water tank.
Also, it's unclear which "replier" you're referring to in your post! If it was me, my listing clearly stated as being a list of the tanks as of 1949. Which was LONG after the time when the item you mention might have been there!
Rich