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The embankment of Pond 1 has been built of impermeable materials, <br />• and there has been no evidence of seepage. There is a difference <br />in elevation of 8' between the top of the dam and the lowest point <br />on the dam centerline (8202' - 8194'). The crest width varies from <br />8' - 17' and is no less than 8' wide. Embankment side slopes will <br />be stabilized against erosion with either vegetation or rock. <br />Sediment storage volume for 10 years of sediment of 0.81 acre feet <br />is provided in the design. Modelling with SEDCAD+ utilized a <br />rainfall factor (R) of 26.5. This portion of Jackson County is <br />located in a rainfall zone of 20. There are 4.33 inches of <br />precipitation between December and March, resulting in a snowmelt- <br />corrected R of 26.5. Sedimentology factors were derived from the <br />Phase II Bond Release documentation dated 8/16/90. <br />Peak flows were estimated for the drainage area consisting of the <br />undisturbed land west of the permit area (71.3 acres) and the <br />reclaimed area draining to the impoundment (26.7 acres). Both <br />areas were run with a curve number of 84 per the Phase II Bond <br />Release documentation dated 8/16/90. Three storms were run: the 5- <br />year 24-hour; the 10-year 24-hour and the 25-year 24-hour of 1.4", <br />1.6" and 2.0". <br />• The principal spillway has an 18" riser pipe located at 8196.26' <br />and an 18" barrel constructed of CMP. The adjustable weir will be <br />set between 8199' and 8196' to effect a difference in elevation of <br />1' to 3' from the invert crest of the emergency spillway at 8200'. <br />There is 3.5 acre feet of volume between the maximum sediment <br />storage level and the primary spillway set at 8199'. The 5-year <br />storm of 1.4" generates 3.12 acre feet of runoff and the 10-year <br />storm of 1.6" generates 4.14 acre feet of runoff. Design flow <br />through the primary spillway can handle a 10-year 24-hour event <br />without discharge over the emergency spillway. <br />The 25-year storm of 2.0" generates 6.41 acre feet of runoff. The <br />emergency spillway can safely pass the design flow of a 25-year, <br />24-hour storm of 15.41 cfs within the trapezoidal channel which has <br />a 16.5' bottom width and 6:1 (H:V) and 3.5:1 (H:V) side slopes. <br />The embankment of Pond 2 has been built of impermeable materials, <br />and there has been no evidence of seepage. There is a difference <br />in elevation of 10' between the top of the dam and the lowest pond <br />elevation (8216' - 8226'). The Crest width is 12' wide. Embank- <br />ment side slopes will be stabilized against erosion with either <br />vegetation or rock. <br />• Q-1 <br />