2016-12-19_PERMIT FILE - C1981038

• Permit No: C1981038
• IBM Index Class Name: Permit File
• Doc Date: 12/19/2016
• Section_Exhibit Name: Volume 8A - Soil Loss Comparison
• Media Type: D
• Archive: No

The Universal Soil Loss Equation will be used to calculate the soil loss from the reclaimed mine site, run -
of -mine area and the adjacent baseline area to determine if untreated drainage from the reclaimed mine site
and run -of -mine area are 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 USLE calculations
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 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 picked from the U.S.
Department of Agriculture Soil Survey, Paonia Area, and is based on the soils classification
of 33-Delson stony loam, 3 to 20 percent slopes for the ROM area and 34-Delson stony loam
20 to 60 percent slopes for the west mine and adjacent area. The K factors for both soils is 0.15.
LS (length and percent slope) factors account for the length and percent slope. These factors are taken
from page 6 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 Run -of -Mine and West Mine Areas are defined by the length and slope gradient within the
distrubed area. LS factors for the adjacent areas were developed in the area immediately adjacent to the
disturbed area boundary for the run -of -mine and west mine areas.
Oak Brush Adjacent Area (West Mine) - LS Factor
The LS factor for the Oak Brush Adjacent area is based on an average 3.5H:1 V Slope and an average
vertical height of 180 feet and average length of slope is 639 feet based on two flow lines located in the
adjacent area. The length of slope of run-off from the reference area was reduced to a length of 501.5 feet
to make it comparable to the west mine area.
Average Length 501.5 Feet
Average Slope 28.2%
Percent Slope (S)
25.0% 28.2% 30.0%
500 13.000 16.200 18.000
501.5 1 "LS" Factor 16.215
6001 14.000 17.200 19.000
West Mine - LS Factor
The LS factor for the West Mine Area is based on an average 3.7H:1 V slope at an average
vertical height of 134.6 feet based on six flow lines cut through the reclaimed area.
Average Length 501.5 Feet
Average Slope 26.8%
Percent Slope (S)
25.0% 26.8% 30.0%
500 13.000 14.800 18.000
501.5 1 "LS" Factor 14.815
6001 14.000 15.800 19.000
TR -58 Ate')" " Volume 8A - 2 03/14