I really can not see the reason as to why you can not use a pump with a High banker.
I have had a really good look through the regulations and they explicitly state As such,
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Permitted tools and extent of diggings
Hand tools such as picks, shovels, hammers, sieves, shakers, electronic detectors and other similar tools can be used. No machinery is permitted.
You can collect from the surface or by digging, but you are not permitted to dig below 2m of the natural ground surface of land or below 0.5m in streams. Overhangs and tunnels are not allowed.
On road reserves, no digging is permitted but collection from existing exposures is allowed.
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This is stating that you may not use a machine to dig your ore. Also to me use of machinery
to process your ore is not allowed. In other words a motor driven implement like a Trommel.
A Banker is not a machine.
It is a static, Classifying device that relies on water flow and gravity.
There are no mechanically driven components.
The water pump is not giving any mechanical advantage. All it is doing is transferring water to the sluice for it
to statically process your hand collected ore.
Mind you, If it is a huge diesel driven plant, Even I would get up set about that as you are now entering into small scale mining as an example.
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I honestly think that a lot of the rangers are trying to cover their butt and say no to banking to scare people off and no one is willing to test it in court.