If you look at old photos on various Facebook pages, scrap metal yards played a major role in railfan hobby world. But now all the scrapyards are gone from the Bay Area. What happened that made this happen in terms of environmental regulations, which is likely cause? What and where were the last yards open?

There was yard in Benicia north side of the bridge.

Would scrap metal ever see a resurgence to the point that a new yard could be built in Bay Area with possibly satellite yards to collect scrap via rail and shuttle to central consolidation yard?

What about garbage trains? Southern Pacific?