Our railroad is mostly in the explosives business, and shall be processing saltpeter which is also known as potassium nitrate. Saltpeter is used in gunpowder, and also makes a powerful fertilizer. More on the commodity later...
There isn't enough grade for an over and under layout, and I do want to run two locomotives at a time for spectator interest. That leaves one solution, two loops of track, one higher than the other. I start with the first track plan and its 10 1/2" radius curves.
My first try is to copy the lower level and paste it on top as an inverted loop.
The two straight sections on top will become a transfer station for bat poop (technical term!)
The beauty of On30 is that you can get really silly with the scenery. I'm putting in a steep canyon with a fast moving river, a small but navigable river and dock, and the cave itself higher up. The left hand side will be dual tunnels so that we can make the mountainside look bigger.
Tunnel portals have been added, including the cave mouth.
I've added the hopper/dumper transfer station up top, a small mine manager's office high on the mountain, and a very small station for passengers to get on the railroad. The two curves over the gorge will be spanned with steel trestles and a ton of rust!
Tight On30 layouts give rise to really weird track arrangements like this curve directly over the lower track. While it would be very odd to see this in real life, it just gives me a great opportunity to build some interesting steel supported track and add more rust. Add this to steep cliffs, rushing rivers and lots of gray boulders lined with thick, deciduous trees and you have a wonderful layout!
Time to make some benchwork!