Feasibility Study and Technical Report - Pretivm

1.7 MINING METHODSThe underground mine design supports the extraction of 2,700 t/d of ore via transverselonghole open stoping (LHOS) and longitudinal LHOS. Paste backfill and moderntrackless mobile equipment will be used. Mine access will be by a main decline from asurface portal close to the concentrator. A parallel decline will be dedicated to conveyingcrushed ore directly to the concentrator via a 650 m long conveyor. There will be a twoyearpre-production development period, with steady-state production being reached inYear 2 of a 22-year LOM. The highest value ore will be targeted in the early productionyears. Steady-state production from years 2 through 18 will average about 980,000 t/a.Geotechnical designs and recommendations are based on the results of siteinvestigations, and geotechnical assessments that include rock mass characterization,structural geology interpretations, excavation and pillar stability analyses, and groundsupport design.The groundwater flow system was conceptualized to provide inflow estimates to mineworkings. These estimates referenced results of site investigations and hydrogeologictesting and were used to size dewatering equipment and as input to the process waterbalance.During the pre-production period, most of the mobile equipment for development andstoping work will be supplied by the Owner and operated by a contractor. Key equipmentrequirements will include jumbos, load-haul-dumps (LHDs), haulage trucks, bolters,shotcrete sprayers, a long hole drill and a cable bolter. Raise development will becontracted out.Manpower will consist of technical staff, mining crews, mechanics, electricians, and othersupport personnel. Pre-production manpower will be supplied by contractor, except fortechnical support. Manpower attains 349 personnel at full production, with up to 163personnel on site at any given time.Infrastructure design is for a mine life over 20 years. Electric power use will bemaximized.The ventilation system is designed to meet BC regulations. Permanent surface fans willbe located at the portals of the twin, intake declines. All intake air entering the mine willbe heated above freezing point.Paste fill distribution design is based on a dual pumping system. A positive displacementpump in the paste fill plant will provide paste to all of the West Zone and the lower zonesof the VOK. The paste plant pump will also feed a booster pump located near the crusherstation at the bottom of the conveyor ramp and near to the main entrance to the VOKarea on the 1,330 Level.Ore will be trucked from working areas to an underground crusher and then transferredto surface via transfer belt to a 42 in main conveyor. Waste will be trucked to surfacewaste piles.Pretium Resources Inc. 1-10 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC