I think around 1970 there was SN track from downtown Pittsburg to Concord near the Bart Yard. It was shortened back to Clyde around 1972 at the Weapons Station entrance where I think they had a connection but don't recall it ever being used. It stayed that way until 5 years-ish ago it was turned into a trail up to the now closed Port Chicago Highway at the Weapons Station gate. At the end Concord had no Industries, just a small 2 track yard with a ramp but thats a memory from when I was 12 years old. There were no industry's at Clyde and Port Chicago was bought out by the Navy and abandoned around 1968. They had a small station but I'm pretty sure there were no industries or regular customers. Heading towards Pittsburg there was what a I believe was a paint pigment plant that took shipments at least through the early 80's. Next was Mcavoy rd that has a siding to a small industrial building thats still there. Beyond that towards Pittsburg they had business but I'm not as familiar with the Pittsburg end as I was a Concord kid.
There is still existing SN track from Pt Chicago to Mcavoy that is long abandoned and I wonder why its still there. From Mcavoy towards Pittsburg there is some still an active chemical plant that still gets a fair amount of hoppers. Of course the Viaduct to the long gone ferry slip is still there, its full of water and garbage and looks pretty gritty. I'm really surprised the UP would leave this fairly high potential liability the way it is. I cant imagine a scenario where it would be used again.

SP 0-6-0, Big thanks for that shot. I was 10 years old then and lived next to the SN line in Concord and it was my introduction to railroading.