A range of mining productivity initiatives was considered as part of the Savannah FS Optimisation, with the objectives of increasing both the mining rate and the mined nickel grade. Of the initiatives evaluated, three key changes, compared to the Feasibility Study were adopted:
- Bogging rates in Savannah North have been increased from 1,000t per day to 1,200t per day by utilising remote technology to bog over shift change;
- Accelerated production in the early years, via the inclusion of a 20m wide vertical pillar in the upper portion of Savannah North, which facilitates the development of a 2nd mining front; and
- Removal of lower grade stopes (0.8 – 1.0% Ni) on the western side of the Upper Zone. This results in approximately 750,000t of material grading 0.9% Ni being removed from the mine plan. It is important to note that this material is not sterilised and remains accessible for mining at higher nickel prices.
Other mining productivity assumptions, including equipment selection, jumbo development rates, stope designs, and paste fill and curing times are unchanged from the Feasibility Study.
Panoramic’s geotechnical consultant (Beck Engineering Pty Ltd) has reviewed the optimised mine plan. The consultant has noted that the vertical pillar may be a source of seismicity/deformation, and that mining conditions in the stopes on the east side of the pillar are likely to worsen as the pillar is approached. Increasing the pillar width may help mitigate the risks.
The above changes to the mine plan result in a shorter mine life of 8.5 years compared to the Feasibility Study, but with an ore mining rate over LOM averaging 0.9Mtpa (Feasibility Study LOM average 0.8Mtpa).