Good questions, Jeff,
I think both of the coal bins are to serve railroad structures, not store locomotive coal or commercial coal. If you look at Chris Walker's enlargement of the same area, it appears that the far, smaller coal bin, with coal piled on the ground at the far end of the bin, is to serve the bunk house and section house to the left.
The larger bin in the foreground, cut into the hill side, probably served the depot. As such, there would be a need for only one set of doors, facing the siding. Coal would be unloaded into the bin from a gondola, later the station agent or section men would collect coal from the same doors (in a wheelbarrow or some such) and cart it across the tracks for the depot stoves.
At the far end of the depot platform seems a small two-door bi-gender privy for passenger use. I don't see any windows on this one either, Chris.
Jim Courtney
Poulsbo, WA