Re: How tough would it be to make a sluice that recirculated it's own water?
I have battled this monster, Settling ponds and Run Time and everything in the middle.
Balance is the key, no matter how many filters you use or how many settling ponds you put into your circut. Recirc systems in the field always use bilge pumps for a reason. The fine materials we deal with in alluvial or elluvial deposits will eat the impeller out of a fountain pump in no time or you will have to consistently stop production to clean filters. 30% of the battle is classification. The larger materials you can keep out of your circut, the less water displacement( longer run time, more gold).
The next 30% is a mucking tray or dewater tray. This still falls under classification but provides the dual purpose of a smaller loss of water when mucking the system.
The next 30% is the pump placement and size of your water reservoir. The pump must be placed as high as possible, You will loss visibility, and that is the last 10% ( knowing your equipment is working, even though you cannot see nothing, but dirty silty water .
No matter what system you use, that is recreational and portable,they have there limitations of runtime. An efficient operator will no when it is time to settle and muck, and never exceed that threshold to have an optimum system.
One tip is use a syphon to remove overburden from your system,Let this material stratify and settle and pour back off the top.( once poured, tap the bucket repeatedly and let stand for a minute and pour again) Bring twice the water, so you may run a fresh batch while you are settling, Most area's where you will use this system, you will not bring your system to the material, but your material to your system or a combination of the two unless you can drive right to your deposit. If you look at actual run time, How many classified 5 gal buckets of material are you going to process in one production run.
3, maybe 5 ( 50 is a yard). Then realize the fact of water displacement because of settled muck and how many of those buckets can you fit into your reservoir, and how many times will you shut down to clean your system. I have seen older guys use a cement mixing black plastic pan to dump their tails to settle during production, but they always bring at least half again of water. I have seen some really cool bucket settling ponds right up to kiddie pools.
Point is, build your equipment site specific, change sites, make a new one. Come up with an operations plan. Many good deposits have been left to sit because of avail resources and transport. Many a good deposit.
Happy Thankgiving...
