Feasibility Study and Technical Report - Pretivm

Electrical power will be supplied to the portal building by four separate 4,160 V feedercircuits from the site main substation. Two feeders (six conductors, 500 MCM each) willsupply power to the 4,160 V distribution equipment located at the portal building. Theother two feeders (six conductors, 350 MCM each) will continue on through the portals tothe underground access declines, one feeder in the main access decline and one in theconveyor decline.The portal building 4,160 V switchgear will incorporate two main incoming circuitbreakers, a tie circuit breaker and suitable feeder circuit breakers. These will supplypower to a 2,500 kVA electric heater unit, two supply transformers, two 500 hp fandrives, a 400 hp conveyor drive, and other auxiliary equipment via a 300 kVA delta-wyestep down transformer with a 5 A continuous rated neutral grounding resistor. A 600 V,600 A motor control center will be supplied by the step down transformer to distributepower to various small horsepower motors and a lighting panel located at the portalbuilding.Each 4,160 V decline feeder will terminate at respective substations located at the 1,300crusher level and 1,320 shop level. A tie circuit will connect the two undergroundsubstations to allow for a redundant power feed system from either underground feeder;with 4,160 V isolating switches configured to allow all electrical equipment to be suppliedby either the main access decline feeder or conveyor decline feeder from the surface.Step down transformers located at the 1,300 and 1,320 Level substations will provide a600 V supply to various electrical loads at that level, including the crusher and mainconveyor feed system, sump pumps, lighting, etc.Additional 4,160 V feeders (three conductors, 500 MCM each), supplied from fuseddisconnects at the crusher and shops substations to both the VOK Zone and West Zoneworking levels, will provide power to portable substations to be used for development,pumping, ventilation, lighting, etc. Figure 16.24 is a schematic of the portal powerdistribution system.Pretium Resources Inc. 16-59 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC