Access development from Savannah to first ore at Savannah North is approximately nine months, and full production from Savannah North is reached 15 months after commencement of development. Full production from Savannah and Savannah North can be maintained for 10 years based on the current mine plan.
Ore and waste haulage to surface is via the existing Savannah decline from the 1440 Level. A single decline development at Savannah North is assumed, with advance averaging 300m per quarter, equivalent to approximately 170m vertical development per year from 1340 Sublevel to 740 Sublevel. Jumbo development is capped at 500m per month, with a limit of 100m per heading per month. This development rate provides sufficient access to stoping areas without restricting production for the centre-out stoping sequence. Total lateral development rates reach a yearly maximum of 5.4km and are above 4.5km for four years. Three twin boom jumbos for decline and access development are initially required once sufficient work areas are established.
The mining schedule targets zones of higher nickel metal tonnes in early production years. The mining rate averages 0.8Mtpa over life of mine and averages 870ktpa in early years (maximum 900ktpa) to 750ktpa in later years of production. Production in later years may be supplemented from future resource growth. Three or more stopes are required to be in production simultaneously to achieve scheduled tonnes. Up to three loaders and seven 60t trucks are required to achieve the scheduled production rates.
Approximately 88% of production is derived via conventional long-hole open stoping and the balance from jumbo mining of development headings (Table 1).
Table 1 – Savannah FS – Mineralised material in the mining plan by mining method
Table 2 – Savannah FS – Mining schedule by year
The mining plan includes approximately 1.1% of material on a contained nickel basis classified as Inferred Resource, as shown in Table 8. The maximum annual contribution of contained nickel derived from Inferred Resources is 2.3%, in Year 10 of the mining plan (Figure 2).
There is a low level of geological confidence associated with Inferred Mineral Resources and there is no certainty that further exploration work will result in the determination of Indicated Mineral Resources or that the production target itself will be realised.
Table 3 – Savannah FS – Mineralised material in the mining plan by JORC category