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1 <br />2.05.3(4)(b) <br />1 <br />Calculations for Pond #1 are shown. in Figure 2.05.3(4)(b)-1. <br />Calculations for Pond #2 are shown in Figure 2.05.3(4)(b)-2. <br />Calculations for Pond #3 are shown in Figure 2.05.3(4)(b)-3. <br />' All calculations of runoff and sizes of sedimentation ponds <br />' were performed by a registered professional engineer. <br />Of the three sedimentation ponds in use, pond 1 and. ? will have <br />' short lives. Pond 1 will not be in existance shortly after <br />June 30, 1982, and pond 2. will last only until ARCO starts <br />construction of their freshwater pond. Sedimentation pond 3 <br />will exist during the entire period of reclamation and is <br />' discussed further below. <br />r^or calculations of all 3 ponds refer to Figure 2.05:3(4)(b)-la, <br />' 2.05.3(4)(b)-2a and 2.05.3(4)(b)-3a. Sediment removal requirements <br />are stated in the figures for all three ponds. <br />Sedimentation Pond #3. <br />The pond was designed for a total volume of 5,482 cubic feet or <br />' 0.126 acre-feet. The figure of 0.1 acre-feet/acre was used to <br />estimate the sediment yield. The dewatering device is currently <br />' in place at an elevation of 6,028. The base of the pond is an <br />elevation of 6,026. The capacity of the pond from elevation <br />' 6,026 to 6,028 is 8,700 cubic feet or 0.200 acre-feet. The <br />60$ sediment capacity is 5,220 cubic .feet or 0.120 acre-feet. <br />The toal sediment yield is 4,000 cubic feet for three years. For <br />' one year, this yield is 1,333 cubic feet or 0.031 acre-feet. Ldith <br />a 60~ sediment capacity of 5,220 cubic feet and a one year <br />' sediment yield of 1,333 cubic feet, the sediment will not need i:o <br />be cleaned out each year. The elevation of the 608 sediment level <br />' capaicty is 1.3 feet above the 6,026 elevation or at an elevation of <br />6,027.3. A wooden post with a sign and mar'c indicating the 608 <br />' sediment level will be installed in the pond to facilitate the <br />determenation of when to excavate the pond. <br />Ia 1 <br />' REVISEC May 15, 1981 <br />64 <br />