Here's the mystery. Google maps shows a bridge and I can find no reference on the Web to a derelict bridge anywhere near Piedra which has me wondering exactly which road were we on? The bridge in the picture above, to me, looks as the it may have been a railroad bridge: it's too narrow for a road bridge and the timbers look as though they may have been railroad ties. There was around 1910 - 1920 a railroad spur to a quarry in Piedra. Perhaps this is a remnant of that line and we were not on Pine Flat Rd at all? We were trying to get to the Corps campground without a lot of backtracking.