I have been to the Yuba Gold Fields. It is administered by the BLM - Folsom office and located off of Hammonton-Smartville Road out in Linda. Go past the Western Aggregates facility (they operate one of the only dredges remaining in operation - you should see it) and follow the road, keep in mind the signs since there is private and BLM land side by side. You can check the BLM Folsom office website for a map.