Kencana underground gold mining done by PT. Nusa Halmahera Minerals (PT.NHM) which is a gold mining
company operating in the Gosowong-Halmahera island in Indonesian. Initially the company was mining with open
pit method in the Gosowong and Toguraci gold mine, then did the expansion of the mine area with a system of
underground mining in the Kencana area is ± 1 km to south Gosowong and Toguraci area is ± 3 km to west
Gosowong. From the results of evaluation of the technical feasibility, underhand cut and fill method (UCF) and the
long hole stope (LHS) selected for considerations include ; the cash flow is low, high recovery, technical mining
safer when dealing with poor rock conditions. The study was conducted at the location Kencana-1 Sublevel 9A Sill
and Sublevel 9A UC3 (mid stope) with long hole stope mining method, ore deposition thickness at this location is ±
50m at a depth of 285m below the ground surface. Drill holes for blasting through the production of made from
Sublevel 9A Sill to Sublevel 9A UC3 and open stoping done backwards with backfill cycle (Figure 1)