Re: What is this?

Nah, Jason's right on if he's pinpointed the bridge on Google Earth correctly. The relocation bridge near Arboles is significantly south of this structure.

Here's the Navajo Reservoir Piedra River relocation bridge: link

And here's what it looks like (now with hiking trail deck on top, but still basically the same bridge):


Jason's structure, located as he said a few miles north of the new Piedra River bridge: link

I've never heard of a spur being run up that canyon along 151, but I'm not an expert in logging spurs down in that area. It certainly looks suspiciously like something of railroad origin, but I can't explain how it got there.