Feasibility Study and Technical Report - Pretivm

• Samples of the lake bottom sediments should be collected so that laboratoryanalyses can be completed to assess this material’s composition, strength, andconsolidation behaviour. Quality sampling of lake bed sediments can be difficultto achieve, though, and may require specialized techniques/equipment. Ifpossible, the thickness of the sediments should also be evaluated throughdrilling or geophysical methods.• Stability analyses should be conducted on the waste rock pile. This will requirethe information on the lake bottom sediments previously recommended.• Construction procedures for the waste rock pile should be re-evaluated basedon the results of the stability analyses if considered necessary.• Sequencing of the waste rock and tailings deposition should be completed toprevent waste rock from being placed on top of the tailings that will bedeposited in the lake.• The minimum depth that waste rock can be submerged in the lake should befurther assessed.• Reclamation and/or mine closure plans should be developed for the waste rockpile.• The need for suspended sediment control measures should be evaluated.The estimated cost for the above-mentioned recommended work is $150,000.26.5.5 TAILINGS DELIVERY SYSTEMRescan recommends the following work for the tailings delivery system:• Numerical simulations predicting the effect of lake-turnover, wind mixing andflow-through on elevating suspended solids concentrations in the lake dischargecould include 3D modelling to fully include the effects of lake bathymetry andhorizontal circulation. Results of the simulations will inform the prescription ofsediment control methods that may need to be taken. The estimated cost forthis work is $50,000.• A comprehensive survey accuracy bathymetric survey of Brucejack Lake shouldbe completed before the detailed design of the tailings disposal system isfinalized. The estimated cost for this work is $50,000.• Tailings slurry rheology should be determined over a range of solidsconcentrations from at least as low as 35% solids by weight. The estimated costfor this work is $10,000.• An attempt should be made to refine the area that can be impacted byavalanches.Pretium Resources Inc. 26-8 1291990200-REP-R0012-02.1Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC