Yes Dave that is it. The siding is of course Boulder Gorge siding. SVRy would typically install a turnout and a short bit of track for the logging companies. The loggers would build their track on from the short spur. Notice the spur on the map. The siding and spur are in the rest/picnic area that is just after you turn off the road going to the base of the dam. The spur leads to a bridge abutment that is still visible built out of logs pinned together. Across the river there is a farily long stretch of grade with tie mounds along the river ending short of the small side creek that was the source of water for the tower. This little creek is in the center of my photo looking across the river. SVRy historian Ron Harr has a photo taken looking across the top of a train stopped at the water tower that shows a cut of stock cars stored on the track across the river. Near as Ron and I can figure out from several sources, this spur was for a sawmill built on this small flat by a company called McMurtran and Shockley. They also had a lumber yard and I believe a planing mill down in Baker on the east side of the UP main in the area across from the Stoddard Mill. McMurtran and Shockley was bought out by Stoddard. I don't have the date at hand. Also Ron found a reference in an old newspaper that read something like "mill bridge at MP...washed out". As I recall we believed it coresponded to this location There is also another bridge abutment perhaps 100yds further downstream and a definite approach across the river. Following this grade, it appears to lead across the upper part of the flat and up the canyon. My wife and I followed a grade for probably 2-3 mile up country. About a mile up it split with one fork climbing onto a ridge and apparently ending. The fork in the bottom continued, but we tired of following it any further. Not far up this canyon in the area of where the water intake was, their appeared to have been a logging/mill camp site, with a large root cellar partially collapsed. Someone has also placer mined over on the other side, so there is much disturbance and it is a little hard to tell which excavation is related to rr and logging vs. mining.
On the map, there is a small square next to the water tank. This I believe is a telephone booth that is listed in the 1916 Structures Val. Report for the site.