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VIII <br />• <br />~ ~ <br />LJ <br />Pond Design <br />As shown in Exhibit K, sediment pond HG-8 is in the area of the initial <br />mining. Exhibit U shows the details of the pond. The pond, as designed, <br />will hold a total of approximately 22.1 acre feet at the invert of the <br />emergency spillway. The storage volume is divided into three components as <br />shown on Exhibit U. These are 1) self-draining runoff storage (14.0 acre- <br />ft), 2) runoff storage that will require pumping (3.4 acre-ft), and 3) <br />sediment storage (3.7 acre-ft). Runoff draining into the pond will be <br />held for a minimum of 24 hours to allow clarification before being dis- <br />charged. As shown in the drawing, a liner of "B" horizon topsoil, a sandy- <br />clay soil found throughout the mine area, is used to prevent seepage into <br />spoil material. This liner material was suggested in Reference 3 and a <br />copy of the gradation and compaction curves is enclosed as Figure 1 of this <br />appendix. <br /> <br />