2011-06-20_PERMIT FILE - C1981041

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USING THE UNIVERSAL SOIL LOSS EQUATION A= RKLSCP A is the soil loss in Tons /AcreNear Shadscale Reference Adiacent RSRDA Reclaimed RSRDA BORROW Reclaimed R = rainfall factor 20.00 20.00 20.00 K = soil erodibili factor - Torriorthents 0.37 0.37 037 LS = combined length slope factor 15.92 14.22 1.316 C = cropping management factor: "C" - Crop Management - Shadscale Canop y 1 2.7% Cover - Grass 4.1% Ground Cover 44.4% 0.08724 "C" - Crop Management - RSRDA Canopy 2.8% Cover - Grass 0.0% Ground Cover 49.3% 0.073 "C" - Crop Management - Borrow Cano y 1 8.4% Cover - Grass 0.9% Ground Cover 30.0% 0.150 P =erosion control practice factor 1 1.00 1.00 1 1.00 I SOIL LOSS CALCULATION Shadsca a Reference Area 20 1 0.37 15.92 0.087 1.0 10.28 Roadside Refuse Disposal Area 20 1 0.37 14.22 0.073 1.0 7.68 Roa si e Refuse Disposal Borrow Area 20 1 0.37 1 1.316 0.150 1.0 1.46 I It can be seen from the above calculation that the revegetated area of the Roadside Refuse Disposal Area and the Roadside Refuse Disposal Borrow Area may loose about 7.68 and 1.46 tons per acre per year respectively to erosion. The Shadscale Reference Area which represents the baseline conditions may loose about 10.28 tons per acre per year to erosion. The above calculation demonstrates that untreated drainage from the reclaimed areas will contribute fewer suspended solids to streamflow or runoff outside the permit area than untreated drainage from the natural surrounding premining area. Ponds 8 and 9 receive drainage from the Roadside Refuse Disposal Area and the Roadside Refuse Disposal Borrow Area. Based on this demonstration, both ponds can be reclaimed. Ponds 8 and 9 have never discharged, therefore, no quality analysis have been performed on the runoff to or from these ponds. 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 ponds 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 areas will reach the Colorado River. The calculated runoff from the reclaimed areas for the 10 year storm (1.4 ") event is 0.68 AF for Pond 8 and 0.70 AF for Pond 9 (Appendix 13 -2). The runoff from this area 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 -4 06/20/11