These are inbound and outbound Standard Oil refinery tracks, or the Richmond Belt as is was more formally known. Switching this extensive property was shared with the Espee, switching every 5 years. When this photo was taken, the Santa Fe had the contract. The Espee mini-hump yard is at the top of this photo. Between the two yards is the Indian Village, occupied by Laguna and Acoma Navajo workers brought out from New Mexico during WWII. It was still occupied during the period this photo was taken.

The "marshy" area you describe is not marshy at all, but a few decades of cleaning drywall (plaster board) remains from emptied bulkhead flats. This was a real headache and I don't knw how they got it cleaned up. The Indian Village and the drywall dump disappeared at about the same time.