Feasibility Study and Technical Report - Pretivm

• mill building• water treatment plant• substation• garbage and incinerator• batch fuel tank• laydown• operations camp• detonator storage• explosives storage• Knipple Transfer Station.Earthworks, including rock blasting, will be required to create the pads. There may bepotentially acid generating (PAG) rock in the mill pad cut. Drainage from this area will becollected and treated. Rock excavated from this area is proposed to be subaqueous fillin the lower laydown area or waste deposited into Brucejack Lake. The pads will befinished with a gravel surface, and will drain to ditches. Despite the mountainous terrain,only minor retaining walls are proposed at this time.Pretivm provided Light Detection and Ranging (LiDAR) data on October 19, 2012, thatTetra Tech deemed to be within ±0.5 m vertical accuracy, which is appropriate for costingat this phase of development. Consideration was given to optimizing operations,providing sound structural foundation bearing capacity, and minimizing earthworksoperations. Proposed pad and road areas were designed and modelled in 3D to obtainapproximate final grades. Cut-and-fill volumes were then derived using computersoftware, and verified by model and cross-section checks. The cut-and-fill volumesaccounted for topsoil removal as well as shrinkage and swell factors. Overall, there is asurplus of material with the current design, which is largely attributed to the mill buildingpad area. The overall surplus of approximately 1.1 Mm 3 will be waste rock that isdeposited into Brucejack Lake.At this feasibility-level stage, Tetra Tech used the available geotechnical information forthe earthworks design and material take-offs. Tetra Tech assumed an average of100 mm of topsoil over 20% of the total disturbed area. Tetra Tech assumed that 25% ofcommon excavation was not suitable as fill and was taken to waste. The other 75% wasassumed acceptable for re-use if required. The rock surface was modelled but with verysparse data. As such, the rock surface is thought to be within ±2 to 3 m accuracy. TetraTech assumed that only 5% of the rock encountered will be rippable, with the remainingrock requiring blasting. BGC provided shrink and swell factors that range from a 7.5%shrinkage factor (bank cut of common excavation to compacted fill) to a 35% swell factor(bank cut of rock to loose stockpile or waste dump). Further geotechnical investigationand ground survey (to total station survey accuracy) should be undertaken as required fordetailed design and scope/price certainty.Pretium Resources Inc. 18-12 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC