Feasibility Study and Technical Report - Pretivm

The filtrate from the pressure filter will be circulated back to the concentrate thickenerfeed well as dilution water. The overflow from the thickener will be pumped to theprocess water tank for re-use as process water.TAILINGS DISPOSALThe final tailings from the bulk rougher/scavenger flotation will be thickened prior tobeing pumped either to the backfill plant for underground backfilling or to the BrucejackLake for storage. Tailings management is further discussed in Section 18.0.The tailings handling equipment and facility will include:• one 20 m diameter high-rate thickener• one 2,000 mm diameter by 3,000 mm high mixing tank for the tailings that willbe discharged to Brucejack Lake• one backfill plant to produce the tailings paste for underground backfilling(tailings paste production is detailed in Section 18.0).• two slurry pumps.When the tailings are discharged to Brucejack Lake, the tailings thickener underflow willbe pumped to the tailings mixing tank where the tailings will be diluted to a solid densityof 35% w/w. When the tailings are backfilled to the excavated underground stopes, thewater from the water treatment plant or from Brucejack Lake will be sent to the mixingtank with the intent to maintain fluidization of the deposited tailings bed. The overflow ofthe thickener will be sent to process water tank.REAGENT HANDLING AND STORAGEPAX and MIBC will be added to the flotation process slurry stream to modify the chemicaland physical characteristics of mineral particle surfaces, and to enhance the floatabilityof the valuable mineral particles into the concentrate products. Flocculant will be usedas a settling aid for the flotation concentrate and tailings thickening. Anti-scalant will beadded as required to protect pipelines and process equipment. Hydrated lime will beused to prepare an alkaline solution for scrubbing.PAX will be shipped to the mine site in solid form. The reagent will be diluted to 10%solution strength in a mixing tank, and stored in a 1.50 m diameter by 1.50 m highholding tank. The solution will be added to the various addition points by meteringpumps. Fresh water will be used to make up the required solution strength.MIBC will be shipped to the plant as liquid in bulk tankers. The reagent will be stored in aholding tank and pumped in undiluted form to the points of addition using meteringpumps.Solid flocculant will be used for the Project. The flocculant will be prepared in thestandard manner in a wetting and mixing system to a dilute solution of less than 0.2%Pretium Resources Inc. 17-12 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC