2013-04-10_PERMIT FILE - C1981018A ‎(2)‎

• Permit No: C1981018A
• IBM Index Class Name: Permit File
• Doc Date: 4/10/2013
• Section_Exhibit Name: Section V. Mine Surface Facilities Reclamation Plan
• Media Type: D
• Archive: Yes

• C =Crop management factor
P =Control practice factor
The rainfall factor (R) used for the Deserado Mine was 30 which was obtained from Figure 1,
EPA -908, "Average Annual Value of Factor R."
The soil erodibility factor (K) was taken from the SCS area soils survey. Where K factors were not
available, a suitable value was obtained by using the material characteristics and using Figure 3,
EPA -908, "Nomograph for Determining Soil Erodibility - Factor "K" or from Appendix A Factors "K"
and "T ". EPA -908.
The length -slope factor (LS) was determined by measuring sub -area lengths and slope
percentages on a map of the drainage basins. The lengths and slopes were then used to obtain
the (LS) factors from Table 1 in EPA -908, "Values of the Topographic Factor'LS "'.
The crop management factor (C) and the control practice factor (P) were assigned the value of 1.0
for disturbed areas. This value corresponds to freshly denuded sites with no conservation
practices. Undisturbed areas were assigned values for (C) and (P) in accordance with their existing
vegetative cover from Table 4, EPA -908, "'C" Factors for Permanent Pasture and Rangeland" and
Table 6, EPA -908, "Determining Factor 'P"." The percentages of vegetative cover were taken from
• Section II -F, Vegetation Report.
Multiplying the factors R, K, LS, C and P yield the annual sediment yield A in tons per acre.
Multiplying A by the acres in the subarea (Ar) yields the annual sediment yield in tons.
•
A bulk density of 80 pounds per cubic foot was assumed for the settled solids. The estimated bulk
density was based on the formula d = We Pc + Wm Pm + Ws Ps where:
d = dry unit weight in pounds per cubic foot
Pc,Pm,Ps = percentages of clay, silt, and sand, respectively
Wc,Wm,Ws = coefficients for clay, silt, and sand, respectively
The above formula and coefficients were taken from "Design of Small Dams," Bureau of
Reclamation, 1974, pp. 778 and 779. The average percentages of clay, silt and sand for the project
area were estimated by a qualified geotechnical engineer during the field investigation for the soils
and foundation investigation for the project plant facilities.
The coefficients and percentages used were as follows:
Pc = 10 percent Pm = 50 percent Ps = 40 percent
We = 40 percent Wm = 72 percent Ws = 97 percent
d = 40 x.10 + 72 x .50 + 97 x.40 = 78.8
Mid -Term Review 2002 (812002) V -9