The Lower Yard at Montour Junction - location of the blue print images, was re-configured, I'm guessing the 1930's. The Turntable was no doubt used to turn the Engine for the Passenger Train, and after the demise of Passenger Trains, its use was no longer needed. At Imperial there was the "wye" for turning before the "wye" at North Star. The original Main Track in the Lower Yard down to the P&LE was rebuilt eliminating the "Siding" seen in the blue prints. That siding was primarily used to hold the Passenger Trains between runs.
 
I have 2 very old 8x10's taken from under the overhead streetcar bridge near the P&LE showing the West End of the Lower Yard and Main Track Siding switch and lead to the yard tracks. These are dated 1917 and came from a Professional Photographer the railroad hired when a young boy was killed playing near the tracks and resulting lawsuit. The rebuilt Lower "New" Yard at Montour Junction had just 3 tracks...Main - New 1 and New 2. In the blue print showing the turntable - to the right you see the word "tank" and to the right of that a circle with a track ending in it.
 
If you have a older Montour RR Timetable, look at Station 5A. This was station 5A which was a ramp track for No 9 retail yard. Hoppers of coal were brought to Montour Junction and shoved up on the ramp for unloading. Residents who bought coal for heating in and around Coraopolis, no doubt purchased their coal from Pittsburgh Coal, No 9 retail Yard transloaded coal from railroad cars to delivery dump trucks.
 
And next to 3A in the turntable blue print you see the squares reading "Office". This was the location of the 2 homes the Montour Railroad used as General Offices from about 1915 to the late 1960's.
 
Gene P. Schaeffer