One humorous thing here, the Mare Island quad has narrow gauge tracks running along the western side of the point. But if you look at the Richmond quad that track has the standard gauge track symbol.

I would guess that the narrow gauge would have moved from the manufacturing areas to storage areas and to transload points.

That track along the western shore doesn't really seem to go to a transload area so it's a mystery to me which quad is correct. That lead comes off the siding at Giant so the southern end of it is definitely standard gauged.

Maybe it was a standard gauged storage track in the closing years but was narrow gauged earlier and that never got corrected on the USGS quad for Mare Island.