A friend and I poked around the Roosevelt back in either the late 70's or early 80's. At the time it looked very similar to the photo posted here. The adit was not sealed at the time, and we walked for quite a distance back into the mountain, well beyond sight of the entrance. There had been trackage in the mine, but the rail had been removed. We came to a cave in that nearly, but not completely, blocked the main tunnel. We were able to look over the top of it and could see the track still in place beyond the cave in, along with a couple of feet of water. At that point we decided we had pushed our luck far enough, and should probably head out. There were many, many side tunnels passed. Looked to have been very extensive workings at the time. And yes, that pile of wood with metal hoops was indeed a wooden pipeline. It ran quite a distance along the mountainside in that area, but I never did find any details of what it was specifically for. I remember at the time you could see it quite well from the road and was amazed at how far it went.
Thanks for the posts about this, and I can't imagine the amount of work that would go into creating an accurate route like this for a simulator. Wow, just wow!
Kent