What was the advantage of using hydraulic mining when mining for gold in the gold rush?

Answer 1

After the hydraulic giant was invented with a balance system to allow one operator to manage it, many large low and medium grade deposits of gold became feasible to mine. Heavy Equipment was extremely expensive to operate and to power, not to mention maintenance.

If adequate water was in the vicinity preferably moved by gravity hydraulic mining could become profitable. If was cheaper if the water pressure was generated by gravity through a stream dammed and piped to the working face rather than by mechanical pumps due to cost. Other considerations were a area usually a river to dump the tailing's in a gouge or steep valley also works but most always lead to a river.

Hydraulicking the ground was also used to remove overburden or barren ground so hydraulicking was employed to remove this layer and expose the gold bearing gravels below.

Many hydraulic mining operations both large and small were forced to shut down by changes in mining laws and WWII as there was a ban on mining except for select metals and minerals shut all of the operations down the majority of which never restarted. The areas where work stopped are good areas to employ metal detectors today as the hydraulic nozzles had tremendous amounts of force but only at the nozzle contact are and directly below. The hydraulicked floor of the pit or "cut" would wash a fair amount of the fine gold down but unless thoroughly cleaned of all pay would permit larger coarser gold to settle near the surface hidden.