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-29- <br />r 1 <br />The modified LISLE requires a representative cross-section for determination <br />of the LS factor. It is believed that the cross-section shown in Tahle 6 is a <br />conservative basis for analysis of disturbed areas at the mine. The parameters <br />used in the headings of Table 6, including computational procedure, are discussed <br />in the Utah State (1976) handbook <br />R and K were determined from maps in the <br />handbook. <br />As seen in Table 6, under the proposed reclamation plan, the potential <br />erosion from Rienau t4ine is estimated as being approximately 351 tons/year from <br />the cross-hatched area on the west side of Highway 13 and 189 tons/year on the <br />east side--approximately 0.01 acre-foot/acre (assuming a unit weight of <br />100 lb/ft3). Sediment yields from the mine would be 0.05 acre-foot/acre disturbed-- <br />25 percent of the potential yield (0.2 a-f/acre) in the OSt1 regulations, assuming <br />n <br />no erosion control upstream from the settling ponds. <br />The analysis above suggests that 0.05 acre-foot/acre disturbed is a con- <br />servative estimate for dead storage. Table 7 summarizes size requirements for <br />each pond in each category - including potential mine drainage and runoff from <br />the coal storage area. <br />Table 7 - Settling pond storage requirements for Rienau t4ine <br />Estimated Storage Volume (Acre-feet) <br />Pond Location Upstream Area Mine <br />(Acres) 10-yr,24-hour Sediment Drainage Total <br />West side 13 0.52 0.65 -- 1.25 <br />East side 7 .28 .35 1.33 2.00 <br /> <br />