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LODESTAR ENERGY, INC. <br />MUNGER CANYON MINE <br />Small Area Exemption #4 <br />Topsoil Storage Area <br />The run-off from the topsoil storage area has been contained in a small sediment trap <br />for many years. Vegetation has established over the years so untreated drainage from <br />the topsoil stockpile should contribute the same amount or fewer suspended solids to <br />streamflow or runoff outside the permit area as untreated drainage from the natural <br />surrounding pre-mining area. <br />The following SEDCAD demonstration shows that the existing grasses, estimated to <br />account for 15% cover, provide a grass filter that will limit total suspended solids <br />concentration in the run-off from the topsoil storage area to less than 0.5 ml/I. <br />Notes for SEDCAD 4 Calculation: <br />1. The topsoil pile is approximately 200-feet by 75-feet (0.34 acres) with an average <br />slope of 10%. <br />2. 10-Year 24-hour event 1.4". <br />3. The soil type is Loam shown on Figure 4.7-1. <br />4. The roughness coefficient of 0.02 was used. <br />5. An infiltration rate of 0.15 inches per hour was used which is in the low range for <br />Loam. <br />6. A grass stiffness factor of 20 was used which represents native grasses. <br />7. A curve number of 80 represents sagebrush with grass understory, soil type C. <br />The relatively high curve number was selected so the model generated run-off. <br />8. A K factor of 0.24 represents a loam or sandy loam. <br />9. A C factor of 0.35 represents brush. <br />10. The run-off only needs to pass through a grass filter 75-feet wide and 2-feet long <br />to reduce the TSS concentration to less than 0.5 ml/I. <br />ENGINEER'S CERTIFICATION <br />The calculations and informati~o~~iesented on pages M(viii)-4 through M(viii)-4vii were <br />prepared by me during the ~~tIRb6~rj~ 2002, and the information presented is true <br />and correct to the best ofk~~rd~A°oSN~~lq~~pd belief. <br />y <br />Engineer <br />19230 <br />M(viii)-4 4/02 <br />