2016-10-25_REVISION - C1981041 - Laserfiche WebLink

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SL -9 The Universal Soil Loss Equation will be used to calculate the soil loss from the reclaimed areas, and the shadscale reference area to determine if untreated drainage from the reclaimed mine site is contributing suspended solids in excess of premining levels. 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 LISLE calculations are obtained from the referenced Agronomy Note #50. The reclaimed areas are broken into seven separate areas for evaluation; Ponds 7, 9, Ponds 6 & 10, Pond 13 and associated permanent drainages, CBA Sump #1 CRDA Road and the G Substation, . 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 30 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 slopes and the adjacent natural slope. 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 derived from data from the U.S Department of Agriculture Soil Survey, Web Soil Survey, and is based on the soils classification of 15 -Cameo Fine Sandy Loam. SedCad was used to select the X' Factor. The K factor for the soil is 0.24 LS (length and percent slope) factors account for the length and percent slope. These factors are taken from Figure 4 of this document. 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, terrace or diversion , or (3) where water leaves the field The LS for the Reclaimed Areas are defined by the length and slope gradient within the distrubed area LS factors for the adjacent areas are drawn immediately adjacent to the disturbed area boundary for the reclaimed areas. Adjacent Area (CBA #2) - LS Factor The LS factor for the Adjacent area is based on an average 35H:1 V Slope and an average change in elevation of 4 feet and average length of slope is 139 feet based on two flow lines located in the adjacent area. Average Length 1390 Feet Average Slope 30% Percent Slope (S) 20% 3.0% 4.0% 120 0 210 0.300 0 430 139.0 "LS" Factor 0.319 140 0 220 0 320 0 460 CBA #2- LS Factor The LS factor for CBA #2 Area is based on an average 33H.1 V slope at an average change in elevation of 4 feet based on two flow lines cut through the reclaimed area. Average Length 130.0 Feet Average Slope 30% Percent Slope (S) 2.0% 3.0% 4.0% 120 0 210 0.300 0 430 130.0 "LS" Factor 0.310 140 0.220 0.320 0.460 Tab -9, Page 6 Revised 10/18/2016