Neo Tokyo,
I hope my design of the gravity dredge doesn't spark a run-on pipe at the local hardware stores. I do hope to build another one with this design. My first wasn't as glamorous as this one. I made it out of only one size the tubing until I got to the end, then inside of 6 feet I scaled up from 4 inches down to one and half inches. I was working just north of the bedrock on the East Fork San Gabriel River at Heaton Flats. If you haven't ever been there yet you'll like it. I really like the Reading, Red Bluff area where you live.
While driving truck for a trailer parts company, I made deliveries in your area from our factory here in Gardena. I was very young, just out of high school. As a kid living in Roseville my dad and I did some fishing upon the Feather River.