I took this photo last Monday. It's the Marmet Locks and Dam on the Kanawha River. This angle shows the hydroelectric plant at the abutment end of the dam. The hydro plant opened in 1935, according to a sign on the site.
I put the photo in a Facebook album, after which a Facebook friend added this comment:
"In the mid 70's, the air pollution was so bad up there that they used to say you had to have leather lungs and steel eyes to be a lock man at Marmet."
Here's another photo of the dam, emphasizing the piers and the rollers.
After I took these photos and saw them on my computer, I noticed that almost no water was flowing under the rollers. Most or all of it must have been coming through the hydroelectric plant.