Originally Posted by St.Stan
I was astounded by the size of the gravel bars along the sides of the creek past Red Dog. I'm assuming thats all eroding runoff from old hydraulic workings. Almost 150 years later and it's still there, amazing how destructive hydraulic mining was.
If you really want to know, that is not errosion SINCE hydraulic mining, that is the waste rock FROM the hydraulic mining. The source of that material you're seeing in Greenhorn Creek actually comes from the adjacent hydraulic mines from the next ridges over (in a different drainage).
By design many of the mines would "wash" that material from the walls within the "diggins" and once on the floor that slurry would be directed into a drain hole (or holes). Once it went into the drain hole it then flowed horizontally through the tunnel and was eventually deposited over into the next drainage. Those horizontal "drains" were essentially the giant sluce boxes and that is where the gold was recovered in the process. After that, all of the gravelly waste rock just accumulated in the drainage.
Warp ahead 70 years later and now that gravel material is once again being minded - but this time as an aggregate material. The ultimate plan is to try and return the creek bed back to a pre-hydraulic mining condition.