Feasibility Study and Technical Report - Pretivm

TRANSMISSION LINEAvalanche HazardThe preferred transmission line route begins at Long Lake, where a hydroelectricgeneration facility is currently being built, approximately 14 km north of Stewart, BC.Although the exact alignment has not been finalized, the line is proposed to follow a routeon the east side of the Salmon Glacier Valley to the proposed Knipple Transfer Stationarea. The line is then proposed to follow a route along a ridge on the southwest side ofthe Knipple Glacier to the mine site. An optional transmission line route for the Projectfollows the access road alignment from the BC Hydro Northern Transmission Line (NTL)at Highway 37.Initial analysis indicates that there is approximately 20 to 25 avalanche paths that affectthe preferred transmission line route, although they would only pose a hazard ifsupporting structures (towers) were built in avalanche paths, or conductors were lowenough to the ground. Potential consequences include damage to towers or conductors,and interruption of service to the mine. In addition, worker injury of fatality may occur ifthe line is built, or if maintenance if undertaken in avalanche hazard areas duringavalanche season. The final alignment of the transmission line (including specificstructure locations) is expected to be detailed during the next phase of the Project, andwill be assessed further for avalanches at that time.The optional transmission line alignment parallels the access road from the NTL adjacentto Highway 37, and is potentially affected by the same avalanches that affect the accessroad. There may also be additional paths that affect the line depending on the finalalignment. Potential consequences to the Project would be the same as theconsequences of avalanches reaching the preferred transmission line alignment.Static Snow ForcesIn addition to avalanche hazards, transmission line towers may be subject to forces ofsnow creep and glide, depending on their location on slopes. Although snow creep andglide are not fast moving events, they may generate forces that can exceed the bendingstrength of the tower or the strength of the foundation. If towers built on slopes are notdesigned to withstand these forces, potential consequences may include damage totowers and associated impact to conductors resulting in interruption of services to themine.18.7 TRANSMISSION LINEThe Project will be powered by electricity from the BC Hydro system. After reviewingpotential transmission routes, it was determined that the preferred route is from therecently constructed Long Lake Hydro Substation to the Project site. The feasibility of this50 km route was investigated by Valard, under contract to Pretivm, to provide afeasibility-level design, cost estimate, and an assessment of constructability for thetransmission line route. The full analysis of the transmission line is presented in Valard’sreport entitled “Brucejack Project – Transmission Feasibility Study and Cost Estimates”Pretium Resources Inc. 18-22 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC