Here's a site where you can get some of the permits you need in Oregon to prospect and more.
DEQ DEQ 600 (highbanker) permit
DEQ 700-PM Permit DEQ 600 (Highbanker) Instructions
DEQ 700-PM Instructions Timing for in Water Work
Department of State Lands Essential Salmonid Habitat Maps
Metal Detector Reviews DSL Report Form
Go to the link at bottom of this page for Oregon Prospecting Supplies & Detector Sales (Scroll Down) once there go to their Links Page.