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Homestake Mining Company June 17,2019 <br /> Regular(112d)Operation Reclamation Permit Application Package <br /> The SRCE model inputs for the East Diversion Ditch are based on the following general scope of <br /> work(SOW) and assumptions: <br /> • Excavation included the excavation, placing, moisture conditioning, oversize segregation, <br /> and compacting of Structural Fill to reconstruct the ditch. The source of compacted fill was <br /> assumed to be local cut material from the ditch excavation. Quantities were estimated <br /> based on the difference between the existing ground topography and ditch design surface. <br /> • Geosynthetic Clay Liner (GCL) included the manufacturing, supply and installation. The <br /> work included packaging, shipping, freight, unloading, stockpiling, staging, retrieving GCL <br /> material from storage area, deployment, seaming, testing, and protecting the GCL from <br /> weather during construction. Wastage, overlap and material installed in the anchor <br /> trenches were considered incidental to the Work. Quantities were estimated using the <br /> design ditch width multiplied by the design ditch length, corrected for slope. <br /> • Import and Place Riprap included the crushing, screening, loading, hauling, placement <br /> and grading of the Riprap, including bedding material. The cost assumed that 50% of the <br /> Riprap would be salvaged from the existing ditch. The borrow source for the remaining <br /> 50% of the Riprap material was assumed to be the North Pit Northwest Pit Wall Layback. <br /> Quantities were estimated by multiplying the design cross section of the ditch by the <br /> design length of the ditch, multiplied by the Riprap thickness. <br /> Key SRCE Costing assumptions included the following: <br /> • The excavation equipment fleet was assigned as "Small' within the model, which <br /> corresponds with a Caterpillar 325C class Excavator. <br /> • Riprap is in the current ditch, so an excavated material condition factor of 0.8 (Hard to Cut) <br /> was used in the SRCE model to account for the resulting additional level of difficulty. <br /> 4.2.2. Landslide Crest Mitigation <br /> The SRCE model inputs for the Landslide Crest Mitigation were based on the following general <br /> SOW and assumptions: <br /> • Logging work included the logging and clear-cutting of trees prior to clearing and grubbing. <br /> There was no allowance for this in the cost estimate as the salvage value was assumed <br /> to exceed the contractor cost. <br /> • Clearing and Grubbing included clearing and grubbing as required to remove vegetation <br /> prior to regrading. Quantities were estimated using the Landslide Crest Mitigation area <br /> corrected for slope. <br /> Costs for the labor, equipment, and materials associated with the Clearing and Grubbing <br /> were obtained from RSMeans(2018). This assumes a crew and corresponding equipment <br /> comprised of one 1.5 cubic yard (CY) Hydraulic Excavator and operator, and two 12 CY <br /> Dump Trucks and drivers. <br /> • Regrading included minor recontouring and surface preparation to fill in the tension cracks <br /> and promote positive drainage. Quantities were estimated using the Landslide Crest <br /> Mitigation area corrected for slope, multiplied by an average depth of 5 ft. <br /> The grading equipment fleet was assigned as "Medium" within the model, which <br /> corresponds to a Caterpillar D8R class Dozer fleet. <br /> EXHIBIT L-RULE 6 4 12 (RECLAMATION COSTS)(Revised June 17,2019) Page 8 <br /> HOMESTAKE MINING COMPANY <br />