2013-04-08_PERMIT FILE - C1982057A (2)

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• Embankment Crest Width: 5 feet • Downstream Slope Height: 9 feet • Downstream Slope Angle: 2H:1 V • Upstream Slope Height: 8 feet • Upstream Slope Angle: 2H:1 V • Height from Spillway Invert to Upstream Slope Toe: 5 feet This geometry is illustrated by the SLOPE /W output shown on attached Figure 13- 1 1.1, Stock Tank Stability.. The embankments will be constructed from spoil material produced during mining. This material is placed in controlled lifts and compacted. Based on this fact, observations of the on -site spoil piles, and typical strength values for spoil material, the following strength properties were assigned to the embankment. • Spoil: 0 = 381, cohesion = 0 psi • Unit Weight: 120 pcf Based on the above stated assumptions, safety factor of 1.56 was calculated by the limit equilibrium analysis. Rule 4.05.9(8)(b) states that the stockponds require a safety factor of 1 .3. Therefore, these structures should perform adequately during the life of mine. In addition, stockponds will be located so that there are no potential safety hazards to downstream structures; therefore, if a failure did occur, ¢ there would be minimal risk to life and property. SUMMARY After completion, an as -built report will be prepared and certified for each stock tanks constructed and submitted to the Division. Upon final reclamation, if a stock tank is to remain as a permanent structure, the appropriate application forms for stock water tanks will be filed with the Colorado Office of the State Engineer and forwarded to the Division for approval. The Colorado Office of the State Engineer was contacted regarding jurisdiction of permanent stock water ponds. According to the Division Engineer and as stated in Section 35 -49- 107(2) CSR, any dams that are less than five feet high and impound less than two acre -feet of water would not fall under their jurisdiction. 2