Feasibility Study and Technical Report - Pretivm

16.10 PASTE FILL DISTRIBUTIONP&C completed a feasibility level paste backfill distribution design for the Project. Theproposed paste fill distribution system transports the paste from the surface plant to theunderground stopes through a pipeline system. The paste was characterized throughlaboratory rheology testing on un-cemented paste samples. A summary of the pastedistribution system follows:• The paste fill distribution will require a two-stage pumping system. A positivedisplacement pump in the paste fill plant will provide paste to all of the WestZone (West Zone Upper and West Zone Lower) and the lower zones of the VOKZone (VOK, below the 1,330 Level). The paste plant pump will also feed abooster pump located near the crusher station at the bottom of the conveyorramp. This booster pump will pump paste up to the Galena Hill and the upperVOK Zone (1,330 Level and above).• The paste pumps will both be positive displacement piston pumps of 98 m 3 /hpeak capacity with a pressure rating of 120 bar. The nominal flow rate for thesystem will be 79 m 3 /h, with a nominal design supply rate of 112 dry tonnes perhour.• An underground booster pump station will be required to house the positivedisplacement pump, the pump hopper, and a water tank with a high-pressurepump for pipeline flushing. A smaller cubby adjacent to the station will berequired for the pump hydraulic packs.• Two large flush-out areas situated at low points in the system will be necessaryfor pipeline diversion during regular shutdown procedures and operation upsets.These will be sumps that can be mucked out regularly.• Instrumentation required to ensure controlled operation will include 10permanent pressure gauges; three permanent cameras and four mobilecameras for the pour points; automated diversion valves at the sumps, andintegrated process control with the paste fill plant.• Hydraulic modelling shows that this system will provide paste to the stopes at anominal yield stress of 248 Pa with a range of 109 to 375 Pa. This equates toan un-cemented paste percent solids of 75.5% solids by weight (ranging from 74to 77% solids by weight).• The piping specified for this distribution system is 8 in API 5L X52. The scheduleof the pipe varies with the pressure rating of the area: borehole casing and loopsin the upper VOK Zone levels will be Schedule 120, while the lower VOK Zoneand all the West Zone casing and loops will be Schedule 80. The main driftpiping (trunk) and level piping to the stopes will be Schedule 80 and Schedule40, respectively. Victaulic couplings will be used as the connection method.Pretium Resources Inc. 16-71 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC