Zandfontein UG2 TSF
The tailings have been deposited in the TSF from 1980 until 2013, when the mine went on Care and Maintenance. The material in the TSF was primarily derived from the processing of UG2 Chromitite ore. The tailings deposited in the TSF, originated as fines after milling and extracting the PGEs concentrates. Therefore the Cr2O3, PGEs and Au mineralisation that is now being targeted in the tailings, originates from within the UG2 chromitite seam itself. Some of the tailings were later reprocessed at Barplats to extract a limited amount of the Cr2O3 (an estimated at 1%-2% was processed) and PGEs (estimated at a grade of 0.2 g/t) and then re-deposited in the new front compartment of the tailings dam (Figure 9). The tailings also contain silicate material and minor amounts of base sulphide minerals or their oxidized products.

The average Cr2O3 and FeO contents (derived from 246 tailings samples) for the the Project are; 20.72% and 15.65% respectively. The average of Cr to Fe ratio on the TSF in Domain 101 is 1.35 and in Domain 102 1.28. The chromium oxide present in the tailings is in the form of chromite grains that have been liberated during the crushing and milling of the chromitite ore. The Au is expected to be present as very fine grained particles that were released after the oxidation of the primary sulphide minerals. It is assumed that the major silicate minerals present are pyroxene (enstatite/bronzite composition) and plagioclase feldspar (anorthite); these occur with chromite, the second major constituent. The PGEs are pre-dominantly associated with the silicate fraction and are expected to consist of Fe-Pt alloys, and the PGMs that are associated with Pt-Pd sulphides (cooperite and braggite) and Ru,Os,Ir sulphide (laurite) that were originally interstitial to the chromite grains and also a very minor portion of small platinum group minerals or alloys that are contained within the chromitite grains.

Barplats’ preference is not to establish a new TSF (Tailing Storage Facility) and so the strategy is for the tailings from the plant to be placed back onto the footprint of the existing TSF while it is being exploited. The TSF has been divided into six areas as part of a strategy to exploit the total volume of tailings material.

Hydraulic mining and Mechanical loading of material on the north-western section will start simultaneously. The associated tailings from the plant following processing will be re- deposited using the cyclone method.

Mechanical loading is necessary in the coarse area of the TSF where material is chemically bonded in layers, which is not able to be hydraulically broken down to the minus 3mm fraction, which is the maximum plant feed size.

Mining Methodology.
Modelling was used to determine the most suitable technique for mining the TSF. The methodology involves continual and simultaneous cleaning, construction, hydraulic mining and deposition activities.

Certain areas need to be excavated using mechanised equipment (i.e. coarser harder material) while other sections of the TSF can be mined hydraulically (i.e. finer softer material).

Mechanised Operations.
Coarse material will be excavated, using a dry mechanised mining method.

The mechanically mined material will be trucked to a scalping screen, which will dry screen the vegetation from the material, after which it will pass through a roller crusher that will ensure that all the material is screened to minus 28 mm.

The material will be pulped and pumped with a jet pump at a planned rate of 203 tph, to the central pumping station with a 3mm wet screen where it will be mixed with the hydraulically mined material.

At the central pumping station, the oversize material (+3 mm), from the test work, indicated to be approximately 50% of the mechanically mined material (100 tph), will pass through a scrubber in closed circuit with the 3mm screen.

The grizzly feeder screen will be set at 40mm and a roller crusher set at 10 mm to protect the booster pump which will transfer the slurry through HDPE pipes to the main slurry pump station.

Hydraulic Operations.
Hydraulic mining involves the material being hydraulically sluiced from the planned sections or blocks of the TSF and transferred in a slurry form to a collection sump via a system of drains or launders. A pump station is then used to pump the slurry to the plant.

The hydraulic sluicing is achieved by using track mounted high pressure water monitor guns (one operating and one on standby) to generate a slurry from the material, which has a specific gravity (SG) of 3.6 t/m3. The resulting slurry density is expected to fluctuate from 1.35 t/m3 to 1.80 t/m3. Water is moved through a series of pumps to increase the pressure of the water to approximately 275 kPa before it is directed through a network of pipes to the high-pressure monitor units on top of the TSF.

The slurry will flow through a launder system to a launder collection sump (on-dam catchment area) and collection barge vertical spindle pump.

A series of 110 kW satellite spindle pumps will be positioned to assist the flow. Static screens (+50 mm) will be used at the satellite pumps to remove debris and vegetation. The 12 m deep catchment area and launder will be created using an excavator. A floating “tripod” barge will be installed in the catchment area to include a vertical spindle pump for onward transfer of the slurry to the main slurry pump station.

Following completion of an upper bench, a second catchment sump will need to be established. Two vertical spindle pumps will be used on a barge system to feed the main transfer slurry pump station. The final cut will follow the same sequence of launder and mining the final footprint from the higher contour levels towards the lower contour levels.

The two satellite pumps will be placed inside the final cut catchment area as a sump and feed the main pump station with slurry. The collection sump, together with the high wall will act to safe guard against flooding of the pump station by collecting runoff water and barricading between the sump and pump station.

A Tailings Storage Facility (TSF) operator will be contracted to do the mining while Chrome Recovery Plant (CRP ) personnel will operate the CRP.

The CRP will remain within the existing processing complex. Its design is based on tried and tested technology and comprises the use of spiral concentrators (spirals), which are generally standard throughout the South African chrome industry. Wherever possible, existing equipment will be retained to reduce capital expenditure. The old spirals will, however, all be replaced with modern spirals to improve recovery and yield. The existing spiral structure will be retained with a few structural modifications. Existing sumps, pumps and pipelines will be upgraded and repositioned to cater for the increase in throughput to 240 ktpm.

The design takes cognisance of the following operating requirements:
- Metal accounting samplers will comply with international best practice;
- All pump boxes, sampler boxes, pipelines, and similar will support a wet, settled slurry density of 5.0 t/m3;
- All process pump boxes will be installed above ground level;
- All slurry sum ........