Alluvial Operation

West Wits plans to use a combination of sluicing (hydraulicking) and earthmoving equipment for the alluvial operation at Derewo. They plan to move the matrix material and small gravel by high pressure water delivered to the mining face using water cannons and passing this material over multiple sluice boxes to recover the gold. Sluice boxes can effectively recover this gold due to its exceptionally coarse nature. If made long enough with riffles and a suitable matting base, the sluices would be able to recover any finer gold found in the upper levels of the gravels.

The boulders and larger sized gravel will be moved away from the mining face using a 20 tonne excavator and a 15 tonne wheel loader. The removed boulders and gravel will be placed below the sluice box outflow to build tailings retention dams and settling ponds to reduce the sediment load impacts in the Derewo River. The Derewo River constantly carries a high sediment load of black graphic clay and silt and as there are no agricultural areas downstream and therefore any increased sediment loading in the river should have negligible impact. An environmental impact statement was submitted by West Wits which it expects approval for in the coming weeks.

This proposed mining approach is considered appropriate for this size and type of gravels. The mining method is simple and relatively low cost which will allow mining of quite low grade provided economies of scale can be achieved.

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All gold coarse and easy captured by sluice boxes

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Schematic of Mining

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Alluvial mining at Porgera in the 1960’s

Next Steps

  1. A detailed survey of the entire mining area should be the next step before bulk sampling or mining begins.
  2. Alluvial development will form part of data compilation for hard rock source

The development strategy:

PHASE I – Commence mapping and sampling program and small scale hydraulic mining operation
PHASE II – Complete access road, dam construction and pipeline, commence large scale mining
PHASE III – Replicate existing operations on multiple mining sites
Environmental Impact Study submitted to local authorities and awaiting approval

West Wits anticipates beginning trial mining in December 2011 with the operation ramping up over the March quarter of 2012.