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factor for the embankment. This method satisfies both moment and force equilibrium of a given analysis. <br />For the worst case scenario, embankment geometry with the follow characteristics was used: <br />• Embankment Crest Width: 5 feet <br />• Downstream Slope Height: 9 feet <br />• Downstream Slope Angle: 2H:1V <br />• Upstream Slope Height: 8 feet <br />• Upstream Slope Angle: 2H:1V <br />• Height from Spillway Invert to Upstream Slope Toe: 5 feet <br />This geometry is illustrated by SLOPEW output shown on Figure 13-11.1, Stock Tank Stability, which is <br />found in Attachment 13-11. <br />The embankment will be constructed from spoil material produced during mining. This material is placed in <br />controlled lifts and compacted. Based on this fact, observations of the on-site spoil piles and typical strength <br />values for spoil material, the following strength properties were assigned to the embankment: <br />• Spoil: m = 38°, cohesion = 0 psi <br />• Unit Weight: 120 pcf <br />Based on the above stated assumptions, safety factor of 1.56 was calculated by the limit equilibrium <br />analysis. Rule 4.05.9(8)(b) states that the stock tanks require a factor of safety of 1.3. Therefore, these <br />structures should perform adequately during the life of mine. <br />As noted above, SCC plans to construct three additional stock tanks in the South Area. The stock <br />tanks will be located in the reclaimed area and are not primary sediment control structures. The <br />stock tank designs will meet the criteria specified in Rule 4.05.9. In addition, the impoundments will <br />comply with applicable State Engineers rules and regulations in anticipation that the postmining <br />landowner(s) will request that the stock tanks be retained as permanent postmining features. <br />In accordance with Section 35-49-107(2) C.R.S., embankments less than five feet in height and <br />impound less than two acre-feet of water are not regulated by the State Engineers Office. <br />Consequently, the water holding capacity will be less than two acre-feet and, the vertical height of <br />the embankments will be five feet or less, as measured from the upstream toe to emergency spillway <br />invert. The combined slope of all embankments will be less than 5H:1V, with no slopes greater than <br />2H:1 V. <br />Each stock tank will contain a single open channel spillway designed to safely pass the 25-year, 24- <br />hour precipitation event. The spillway will be constructed to have a minimum of one (1) foot of <br />freeboard. Riprap requirements were determined using the Pader Method and adding three (3) <br />inches to account for a conservative design. <br />PR-05 11 Revised 01/06 <br />