What the hell is that thing?

I was fishing the North fork of the Willamette today and found a bunch of these things crawling around in some slow moving water.  I was curious, took some photos and video:

Anybody?  It looks like a caddis nymph on steroids with a shell of glued-together tiny rocks.  It was about an inch long and there were a whole bunch of them crawling around in that area.  I'm constantly amazed at the size of some of the bugs out here in OR.