Ed- as long as you have some kind of settling pond, or are far enough away from the waterway so that no turbid water enters the stream or water, you should be okay. IIRC, there is a set back provision on ESH waters, I want to say 300 ft, but not sure.
That being said, Oregon DEQ requires the 600 permit, which is the one they use for highbankers. Problem is, none are being issued at this time. They are rewriting it, and have been for the past several years, with no date forthcoming. Existing 600's are grandfathered in, and you can buy and transfer them.
If you do highbank, and no turbidity is evident, chances are you won't be bothered. I've seen several small bankers operating, and know the people. They can't get the permit. If asked they tell them about the catch 22.... Got to have, want to get, can't because not issuing. No tickets yet.
You're probably going to get into water right issues for pumping from a waterway if they want to push it.
End game is to eliminate all mining/prospecting in the state, then get the pan off the state flag.