A staging yard was there all the time.

I was looking for a spot to store more rolling stock, can't resist buying more, and was looking at the area under Patrick Creek.  There was a double cross over, (lots of trouble with it), that lead out of Grants Pass and into the tunnel under Patrick Creek.  The main line ran in the left of this tunnel and two storage tracks (Smith River) were on the right.  The cross over allowed for continuous running, with the rail on the right being the end of the line or Smith River, everything to the left is Grants Pass.

I removed the double cross over and put in three switches. I also added a run around track (the two tracks on the upper left) to represent the town of Smith River, the cross over (bottom right) allows continuous running, everything to the right is Grants Pass. The track at the bottom right (you can just see the switch) continues on to Crescent City and Smith River, if you go straight, or to Portland and Medford (on the Southern Pacific) if you go to the right.
I am thinking about block switching both tracks at Smith River.  There would be two slots for car cards, one for the Dock and one for the West Yard of which one would always be empty, arriving cars would go to the empty track and their cards to the correct slot and all the cars on the other track and their cards would be picked up. Portland could also be switched as a block, at the start of the day, the S.P. delivers all the cars from Portland and takes all the cars for Portland back.

The tracks under Patrick Creek are, from the left, Medford, on the S.P. (more on that later) the next switch divides the main line, left you go to Portland on the S.P. or on the main line to Crescent City and Smith River (this is the middle track) the next track (the right hand side track from the Smith River run a round) is divided into two storage tracks.  So there are five tracks under Patrick Creek, Medford, Portland, the main line, Smith River Dock and Smith River West Yard. The view below shows the fascia that covers the tracks under Patrick Creek

 

The fascia was cutout, to view the tracks under Patrick Creek.  Two shelves under this opening were set up as Medford.  Cars are brought in on the front track and five finger switched to Medford (the two shelves which hold 40 cars).  Any cars going to or coming from Medford go to the Grants Pass yard.  The car cards are kept with the cars in Medford.  When you want cars from Medford, they are five finger switched to the front track and the cards are put into the box for on line cars.  I move four cars into Medford and bring back 4 cars from Medford, thus the front track is always empty, except when switching Medford. All that space had been there all along, but it is half full already.