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three abandoned treatment ponds, none of which have any topsoil. The area of topsoil stripping is <br />therefore 2.4 acres. Only 1.6 acres is in Soil type AO-B. The remainder of the area is riverwash ma- <br />terial and has very little or no soil. The AO-B soil can be stripped to a depth of 18 inches, therefore <br />the amount of soil to be salvaged is 3872 cubic yards. The topsoil stockpile to store this material is <br />immediately west of the lake as shown on Map C-2. Some soil from this stripping will be used to <br />provide a root medium on the embankment of the lake facing the river. The area of this topsoiling is <br />approximately 20 feet x 680 feet long or 0.3 acre. The average placement depth is 14 inches, there- <br />fore, the total volume is 587 cubic yards. Therefore, the total stripped is 3872 cy - 587 cy for the em- <br />bankment, leaving 3285 cy for the stockpile. <br />The topsoil stockpile will have an average height of 6-10 feet and will be not be seeded since the <br />operation is so short-lived (three months) after which the soil will be replaced on the inside slopes of <br />[he lake and around the lake perimeter. No slopes of the stockpile will exceed 2.OH:1.OV. <br />7. Hydroloev and Sediment Control for Lake Mining <br />A- Disturbed water handline <br />The earlier section on river mining addresses the mnoff controls for the entire yard area. This <br />section addresses the lake area only. The lake area will be excavated around the existing sedi- <br />ment pond at the site, which, prior to lake excavation, is much larger than necessary to con- <br />tain the 100 year event. Since this pond will be expanded into the 4.7 acre lake, all drainage <br />from the site will enter the lake and will be allowed to seep into the ground. During mining, a <br />dewatering pump will be placed in the lake, which will deliver water to the long narrow set- <br />tlingbasin at the south edge of the property. This basin is 5100 square feet in size. It will be <br />excavated to a depth of 3.0 feet The material from the excavation will be separated into top- <br />soil and subsoil and will be stored at the adjacent stockpile area and used in reclamation. <br />Topsoil is expected to be 18-24" thickness. All drainage from the stockpile area will move <br />downhill into the lake. <br />The pump will discharge into the west side of the basin and the water will be allowed to <br />travel to the east side, where a V ditch cut 1.25 feet deep with 2:1 sideslopes will be made to <br />Thomas Pit 2/02 13 <br />