2015-06-08_PERMIT FILE - C1996083 (12)

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Mine Reclaimed Drill Pads and Roads Reclaimed Total Perennial Cover+ Rock+ Litter 87.2% Perennial Cover: Grasses, Grasslikes 38.2% Forbs 17.8% Shrubs 1.3% Other - Rock 1.6% Litter 28.3% Total Perennial Cover+Litter 856% Cano Shrubs 1.3% Ground Cover at Surface 85.6 - 1.3 84.3% The Universal Soil Loss Equation will be used to calculate the soil loss from the reclaimed drill sites and roads and the adjacent areas to determine if untreated drainage from the reclaimed drill sites and roads are contributing suspended solids in excess of premining levels. The drill sites and roads will be deemed to be contributing fewer suspended solid than premining levels if the soil loss from the drill sites and roads are less than the adjacent areas. The following sediment volume calculation is prepared in accordance with U. S Department of Agriculture, Technical Notes, Agronomy Note #50, dated January, 1977 The maps and figures utilized in the USLE are obtained from the referenced Agronomy Note #50. USING THE UNIVERSAL SOIL LOSS EQUATION R (rainfall) factors are assigned by geographical regions based on weather data furnished by the U.S Weather Service. R values are based on rainfall amount, time, and intensity. In the mountains, R values were computed primarily for valley areas and have been increased to account for run-off from snow melt. The R factor of 40 used for this calculation is derived from an iso-erodent map, presented in the referenced Agronomy Note #50, and is the same for both the reclaimed and the adjacent areas. K (soil erodibility) factors are assigned to each soil series and they are used to predict the erodibility of a soil and its tolerance to erosion in relation to specific kinds of land use and treatment. Soils having the highest K value are the most erodible. The K value used for this calculation is picked from the U.S. Department of Agriculture Soil Survey, Paonia Area, Colorado, Parts of Delta, Gunnison and Montrose Counties. The area encompassed by this soil loss comparison is large and contains numerous soil types. A review of Map 4A (Soils NRCS/USFS) in the area east of Terror Creek shows large areas of soil types 2, 13, 38 and 39. Soil type 2 is Absarokee - Work loams, 6 to 25 percent slopes, soil type 3 is Beenom-Absarokee association, 20 to 60 percent slopes, Soil type 38 is Fughes loam, 15 to 25 percent slopes and soil type 39 is Fughes Loam, 25 to 65 percent slopes. The respective K vales for the soils are 0.37, 0.37, 0.20 and 0.20. The average of the four values is 0.28 and will be used for this calculation. LS (length and percent slope) factors account for the length and percent slope. These factors are taken from Figure 4. Length of slope begins at the top of the micro watershed. This is usually at the top of a hill, ridge, terrace or diversion. The length of slope is considered to end for a given field at one of the following places: (1) the point where the slope decreases to the extent that deposition occurs, (2) the point where runoff enters a well-defined channel, gully, terrace or diversion, or (3) where water leaves the field. Since the reclaimed drill pads and roads have be graded to approximate original contours, the LS factor for the reclaimed area and adjacent areas will be the same. It will be assumed the drill pad, drill roads and the adjacent areas have an length of 200 feet and a slope of 10% which yields a LS factor of 2.0. C (cropping - management) factors are the ratios of soil losses from lands cropped under specified conditions to the corresponding losses from tilled, continuous fallow. C factors for land uses other than cropland are included on Figures 7, 8, and 9. The percent ground cover is the primary item to consider because a slight change in the percent ground cover will result in a significant change in the erosion prediction. Figure 7 - "C" Factors for Permanent Pasture and Rangeland Volume IIIB, Tab 24 Page 2 TR -101 04/15