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Rule 6.5 <br />GEOTECHNICAL STABILITY EXHIBIT <br />JD -6 Mine Permit Amendment <br />M- 1977 -310 <br />Based on the apparent stability of many older, unreclaimed waste rock piles in the <br />immediate vicinity, a detailed slope stability analysis was not performed. Many of these <br />older mine waste rock piles have slopes as steep as 1.4H:1 V. The proposed final slope of <br />the JD -6 waste rock embankment is 2H:1 V. <br />In the twenty seven years of working at the mine yard and lower mine waste area no <br />surface springs or seeps have been noted. <br />The stability of the proposed slopes is calculated using estimated material properties and <br />the factor of safety calculation for cohesionless soils without seepage. The planned slope <br />of the reclaimed JD -6 mine waste embankment is 26 degrees. The material will consist <br />of blasted sandstone with an internal angle of friction of approximately 34 degrees. <br />Safety Factor = tangent of internal angle of friction/tangent of angle of material. <br />Therefore <br />Safety Factor = tan 34 tan 26 = .674/.500= 1.38 <br />The calculated safety factor of 1.38 is within the 1.3 to 1.5 safety factor traditionally <br />recommended for permanent slopes. <br />The JD -6 mine has been an underground random room and pillar mine using appropriate <br />blasting materials to advance the underground mining development drifts and to mine the <br />ore in the mine. The mine workings are located approximately 600 feet below the top of <br />Monogram Bench. When blasting is done it usually consists of three or four <br />headings /stopes consisting of approximately 100 pounds of explosives in each <br />heading/stope. To date there has been no indication that any off -site areas have been <br />adversely impacted by the blasting, and there is no indication that any areas should be <br />adversely impacted by the limited blasting done in the mine. <br />1 <br />