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-41- <br />achieve a safety factor of 1.3. In situations in which a static slope safety <br />factor of 1.3 cannot be achieved, the applicant proposes to backfill to that <br />configuration which will maximize the static slope safety factor of that <br />portion of the backfilled slope. Remaining portions of the exposed cut slopes <br />will be treated to achieve a surface which is as erosion ally and as <br />structurally stable as is possible. <br />In response to Division comment, the applicant developed typical backfilled <br />cross-sections, similar to the operational road cross-sections depicted in <br />Figure 2.2-23. The applicant's detailed backfilling and grading proposals are <br />supported by thorough stability analyses of the proposed backfill and grading <br />configurations for the haul road, portal bench and central facilities area. <br />The analysis demonstrated that the redesigned reclaimed configuration's static <br />slope safety factors exceed those of the predisturbance natural slopes. <br />The amended original permit application contained several deficiencies with <br />regard to the underground development waste pile, which have been remedied in <br />supplemental submittals. In response to the Division's Preliminary Adequacy <br />Review, the applicant has prepared and submitted an acceptable geotechnical <br />and stability analysis of the proposed 25,000 cubic yard underground <br />development waste pile. This analysis determined that the pile will achieve a <br />minimum static slope safety factor of 1.684, based upon conservative <br />assumptions of the waste material's strength. The applicant is also committed <br />to an inspection and certification program which conforms with the <br />requirements of Rule 4.09.1(11). The applicant's plan for the disposal of <br />underground development waste of the Munger Canyon Mine is in compliance with <br />the requirements of Rules 2.05.3(6) and 4.09. <br />As previously mentioned, Salt Creek Mining Company has proposed a 25,000 cubic <br />yard underground development waste disposal site to be located adjacent to the <br />Munger Canyon Mine. This waste rock pile will cover 2.6 acres and will be 35 <br />feet high (see Section 2.2.5 of Volume I of the application). Roof fall rock <br />from both the Munger Canyon and McClane Canyon Mines, along with rock slope <br />waste rock from Munger Canyon will be disposed of in this waste rock pile. <br />Surface runoff from the disturbed area will be collected in a sediment pond <br />for treatment. No springs discharge in the area to be covered by the waste <br />rock pile. An alluvial monitoring well, GW-6, has been installed below the <br />waste rock pile to monitor the effect of the structure on alluvial ground <br />water (see Hydrologic Balance: Ground Water section of the permit application). <br />The analyses of the Cameo roof and floor strata contained in Tables 2.1-4 and <br />2.1-5, Volume I of the McClane Canyon permit application indicate that the <br />strata associated with the Cameo seam have high sodium adsorption ratios (SAR) <br />and high pH's. These conditions indicate that the material may limit <br />revegetative success on the reclaimed waste rock pile unless the pile is <br />adequately covered with non-toxic soil and rock materials. Analyses of the <br />material to be generated by the rock slope, as required in original <br />Stipulation No. 1, will indicate whether or not material in the waste pile <br />will be toxic. If these analyses indicate the material is toxic, mitigation <br />will be required, as specified in Rule 4.14.3. <br />