Some leftover wire in the drift. There is a series of these supports working back into the tunnel. Probably supported a power line for lighting.
Bert Loper built this boat and then died in it at the age of 79 while running 24.5 mile rapid in 1949. He was a pioneer of running whitewater and likely knew his time was about up before leaving on his last trip. His companions found this boat farther downstream and moved it up above the high water mark to where it rests today. Bert's bones were found a bit later on farther down the river.