2011-06-20_PERMIT FILE - C1981041

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RECLAIMED AREA - "C' FACTOR North Decline No appreciable canopy. Canopy is assumed to be the combined cover contributed by trees and shrubs. Based on the 2010 Vegetation Evaluation the combined tree and shrub cover totals 16.3 %. The percent ground cover for the reclaimed area shown on the preceding page is 55.9 %. Use figure 7 identified above and interpolate to determine the C factor for 55.9% cover. CANOPY NO APPRECIABLE CANOPY PERCENT GROUND COVER 40.0% 55.9% 60.0% No G 0.100 0.054 0.042 appreciable JAdacent C" Factor 0.05 canopy USING THE UNIVERSAL SOIL LOSS EQUATION A= RKLSCP A is the soil loss in Tons /Acre/Year Grease- wood Adjacent North Decline Reclaimed R = rainfall factor 20.00 20.00 K = soil erodibili factor - Torriorthents 0.37 0.37 LS = combined length slope factor 1.95 1.95 C = cropping management factor. "C" - Crop Management - Shadscale Canopy 11.3% Cover - Grass 4.9% Ground Cover 50.1% 0.071 "C" - Crop Management - SRDA Canopy 16.3% Cover - Grass 10.0% Ground Cover 55.9%1 0.054 P = erosion control practice factor 1 1.00 1.00 --SOIL LOSS CALCULATION AREA R I K LS, C P A Greasewood Reference Area 20 0.37 1.95 1 0.071 1.0 1.02 North Decline 20 0.37 1.95 1 0.054 1.0 0.78 I It can be seen from the above calculation that the revegetated area of the North Decline may loose about 0.78 tons per acre per year. The adjacent area may loose about 1.02 tons per acre per year to erosion. The above calculation demonstrates that untreated drainage from the reclaimed area contributes fewer suspended solids to streamflow or runoff outside the permit area than untreated drainage from the natural surrounding premining area. Pond 7 and two sumps receive drainage from the North Decline. Based on this demonstration, Pond 7 and the two sumps can be reclaimed. Pond 7 has never discharged, therefore, no quality analysis has been performed on the runoff to or from this pond. The disturbed area will not contribute additional suspended solids above natural conditions, and the quality of untreated drainage from the disturbed area will meet the State and Federal water quality standard requirements applicable after the sedimentation pond and treatment facilities are removed because the surrounding areas are very well vegetated and there is virtually no erosion or other stability issues. It is unlikely any significant runoff from the well vegetated reclaimed area will reach the Colorado River. The calculated runoff from the reclaimed area for the 10 year storm (1.4 ") event for Pond 7 is 0.23 AF (Appendix 13 -2), which is insignificant when compared to the average annual runoff generated from the entire Colorado River drainage (2.8 million AF per year). TR -61 A14 -12 -7 06/11