For what it's worth... I had forgotten about this picture. It shows the foam packing I used to make up the main frame of part of my layout. I made two sections like this, each 5' long. That's a "G" scale trestle from my old outdoor layout you can see in the background.
What can I say, Homestake was a huge operation. I imagine they had to lower some very large things into the mine. Did you notice the relatively small guides on the side of the cage? The hoist house is still in operation lowering a similar cage. The Sanford underground laboratory personnel use it for what ever. Some 18" gauge tracks were retained for some use I am not aware of. I assume some rolling stock must also be in use.
I made a little progress around the new bridge area. Before the bridge goes in, scenery behind the bridge and the dry wash need to be finished. Trying to do this after the bridge is installed would be a pain in the butt.