Feasibility Study and Technical Report - Pretivm

partially-heated buildings will either be founded below the design maximum frostpenetration depth, or embedded a minimum depth of 1 m and insulated with sufficientrigid polystyrene insulation, as specified in BGC’s design report (2013). Foundations willalso be setback a minimum of 10 m from the crest of fill slopes.Additional investigations (e.g. geotechnical drilling and test pit excavations) arerecommended for subsequent stages of design to further evaluate subsurface conditionswithin the footprints of the site facilities. Laboratory testing of rock and overburdensamples are also recommended to further evaluate the properties and behaviour ofthese materials. The recommendations provided in Table 18.1 will be re-evaluatedbased on the results of the investigations.18.2.3 SITE GRADINGRecommendations were provided for excavations and fills necessary to bring the site toits design elevations (BGC 2013). It is expected that the overburden can be excavatedwith conventional earth moving construction equipment. As excavations extend into thebedrock, more aggressive excavation equipment and/or blasting will likely be required.Based on the results of the site investigations, it is estimated that the upper 1 to 2 m ofbedrock may be rippable with a D9 bulldozer. Therefore, large excavations in bedrockwill be conducted primarily by controlled blasting.A summary of the recommended cut slope and fill slope angles is provided in Table 18.2Table 18.2Recommended Permanent Cut-and-Fill Slope AnglesItem 1 Material 2MaximumHeight (m)MaximumSlopeCommentsFill Slope Structural fill 15 2H:1V -Fill Slope Rock fill 15 2H:1V -Fill Slope General Fill 5 2H:1V -Fill Slope General Fill 15 2.5H:1V -Cut Slope Overburden 5 2H:1V May have to flatten below the water tableand/or provide drainageCut Slope Overburden 10 2.5H:1V May have to flatten below the water tableand/or provide drainageCut Slope Rock - Unbenched 15 0.5H:1V Spot bolting may be required based onfield engineer's reviewCut Slope Rock - Benched 60(refer tocomments)Refer tocomments6 m bench height, 5 m bench width,75° bench face angle; spot bolting may berequired based on field engineer's reviewNote:1All cut and fill slopes should be reviewed in the field by a qualified geotechnical engineer.2Materials are as per descriptions provided by BGC (2013).Final site grading will maintain positive drainage in the direction of natural drainage andwill direct water away from the structures. Permanent surface water control will also beprovided at the base of all excavation slopes to direct water away from the proposedfacilities and to allow the slopes to drain effectively.Pretium Resources Inc. 18-6 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC