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Geotechnical Stability Exhibit (Rule 6.5): <br /> 83. Under Section 1 —Area Faults, the application describes an unnamed fault which passes <br /> through the eastern mining area, striking at a roughly NW-SE orientation. Based on the <br /> USGS Black Hawk quadrangle, this fault appears to be vertical, in which case, the <br /> primary risk to slope stability would be if the fault orientation was parallel to the <br /> anticipated hard rock benches. Initial stripping in mine phase 1 will expose any <br /> observable portion of this fault, allowing a geotechnical analysis to be performed. Please <br /> commit to submitting a Technical Revision to update the geotechnical stability exhibit <br /> with this information once it is obtained. <br /> A Technical Revision will be submitted to the Division to update the geotechnical stability exhibit <br /> once the unnamed fault is exposed and observable for additional study. <br /> 84. Under Section 2— Slopes Stability, the application states "sufficient buffers will be <br /> maintained to neighboring property lines"so that "buildings or other structures within 200 <br /> feet of the affected area will not be affected by mining excavation"and "maps C-2 <br /> through F-2 show these buffers". However, the Division could not find any mining <br /> setbacks on the figures mentioned. Please clarify if the applicant is referring to the "200' <br /> offset of DRMS Permit Boundary"which is depicted on these figures with a pink dotted <br /> line. Will any setbacks/buffers be maintained from the proposed permit boundary? If so, <br /> please ensure these setbacks/buffers are shown on the mining plan maps in Exhibit C. <br /> Setbacks will be maintained as shown on Exhibit C maps. In some cases, mining slopes will be <br /> within <20 feet of the permit boundary, while in others, mining will not encroach within —600-feet <br /> of the permit boundary. Based on these setbacks, the geotechnical exhibits demonstrate that no <br /> offsite impacts will occur. <br /> 85. Under Section 2—Mining Highwall, the application states "the colluvium covers the <br /> gneiss at an average depth of 160 feet"and "therefore, geotechnical information such as <br /> joint orientation will not be obtained until over 10 years into the life of the mine". Please <br /> clarify the mine phase during which this information will be collected. Additionally, please <br /> commit to submitting a Technical Revision to update the geotechnical stability exhibit <br /> with this information once it is obtained. <br /> Minor portions of bedrock beneath the colluvium will be exposed during phases 1 and 2 and <br /> more significant portions of the bedrock beneath the colluvium will not be exposed until phase 3. <br /> If necessary and as new geotechnical information is revealed, modifications to mining plans will <br /> be submitted as Technical Revisions. Once bedrock is exposed, and prior to any mining of said <br /> bedrock, the permittee will provided a Technical Revision based on observations of the bedrock <br /> (see Division question 83). <br /> 86. Under Section 2— Waste Rock Landform, the application provides the proposed final <br /> overall slope gradient for this feature, which is 2.2H:1 V, but does not provide the <br /> proposed operational slope gradient. Please provide the proposed slope gradient of <br /> each waste rock lift during operations (prior to reclamation). <br /> The WRL is being built at the angle of repose of the material, —1.OH:1.OV. Once a given WRL <br /> lift has reached capacity, it will be bull dozed into final position with a balanced cut and fill <br /> approach. However, the final overall slope is 2.21-1:1.0V. <br /> December 2021 27 Lewicki 81 Associates <br />