Whats interesting to know about the old hydraulic mine sites with their billboards and walking trails highlighting the devastation done by miners. Is that previous generations preserved them as a living history lesson of sorts. Im sure they didn't intend them to be a right or wrong statement, but a lesson to be learned from and a nod to our industrious nature that has shaped our nation.
The irony of these examples of "permanently" scarred landscapes set in amongst the surrounding "pristine virgin forests" with their huge "old growth" timber, is that if you look up pictures of the time when these sites were in operation 100 plus years ago, you'd realize that the surrounding forests were treeless towns supporting populations of up to 5000 folks. The trees had all been cut and cleared to build the towns and provide the lumber for the buildings and miles and miles of water works needed to operate the mines. So if you ever get to go see one of these historical landmarks, look around and see the whole picture, not the highlighted version the current villanizing generation wants you to see. Despite our arrogance and best efforts of preservation and reclamation, when left alone mother nature always seems to reclaim the land and erase any trace of us.
If the tailings and mine dumps created by the mine where I worked, and from several other adjacent mines (likely over a cubic mile of excavation in total), were moved to the valley floor they would create a huge earthen dam (10 or more miles across the valley) and hopefully, a lake if we ever get some rain. Could solve a couple of area problems...Eliminate complaints about "what eyesores they are" and flood out the homes of the NIMBYS who moved there knowing they already existed and then complain about them! Green Valley, AZ, the new Atlantis!
So many interesting changes.
Well a good place to start your research would be to read the law that pretty much stopped hydraulicing,
California Public Resources Code
Section 3980-3985
3981. The business of hydraulic mining may be carried on within the
state wherever and whenever it can be carried on without material
injury to navigable streams or the lands adjacent thereto.
3982. "Hydraulic mining," as used in Section 3981, is mining by
means of the application of water, under pressure, through a nozzle,
against a natural bank.
Here's a video of an operation using a hydraulic monitor in the 1990's.
Also, in one of the Yukon Gold episodes, Cal uses one at his placer mine. That was only a couple of years ago.
They can be great tools to help excavate and move material.