This is a traveling screen
View attachment 550059
The trash screen rotates up and out of the water to allow it to be cleaned of debris by non diving personnel. Works fine up the point that something jams in the screen, or the screen comes off the track. Divers work on them with the plant operating, we used to get the power company to throttle down in off peak hours, but it is a lot of water moving through that screen.
Most of the plants I have been in also has a metal grate in front of the screen to catch larger items.Along with a rake that can be lowered along the grate to pull up things caught in the grate, like a log, old boat parts, Jimmy Hoffa, etc.