REV07488

• Permit No: C1980006
• IBM Index Class Name: Revision
• Doc Name: APPENDIX E & F
• Type & Sequence: SL2
• Media Type: D
• Archive: No

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KERB COAL COMPANY -PARTIAL BOND RELEASE
HYDROLOGIC RECLAMATION EVALUATION
1.0 INTRODUCTION
As part of Phase II partial bond release application for the 720 Pit and Pit 1 reclaimed areas,
Montgomery Watson (MVt~ conducted a sediment yield analysis to determine if calculated sediment
yields for the reclaimed areas are comparable to or better than calculated sediment yields for
prentututg conditions. Major mine disturbance areas include; the Marr Pit area, which was reclaimed
and seeded prior to 1986; the 720 Pit area, which was reclaimed and seeded in 1995; and the Pit 1
area, which was reclaimed and seeded in 1996. The following sections Siimman~r the methodology
and assumptions used in the analysis and analysis results and conclusions.
2.0 METHODOLOGY AND ASSUMPTIONS
Seditnent yields for the major mine disturbance areas were determined for both premining and
rechumed conditions using actual vegetative cover data (reference area data for premining and
disturbed area data for reclaimed) and the Revised Universal Soil Loss Equation (RUSLE):
A=RKLSCP
Where: A= Average annual soil loss in tons/acre/yr
R= Rainfall factor R
K =soil erodibility factor
LS= Length slope factor
C= Cover management factor
P=Support practice factor
RUSLE was used in preference to SEDCAD+ because RLISLE focuses specifically on sediment
yields, where SEDCAD focuses on watershed hydraulics. In fact, SEDCAD+ uses an older and
slightly less accurate version of RUSLE to calculate sediment yields.
2.1 RAINFALL FACTOR IRI
The R factor is an expression of the erosivity of rainfall and runoff at a particular location. An
average annual R factor u needed when computing long-term erosion. MW used the same R factor
used in the existing Permit document which was detemained using the following equation:
Ro,,,,,,o~ = 27P, 6 - for a Type II storm
P_,b = 2-year, 6-hour precipitation in inches = 0.8 inches
R= 27 x (0.8)' z = 16.4
2.2 SOIL ERODIBILITY IKI
The K factor reflects the susceptibility of the soil material to erosion, the potential for sediment
transport, and the amount and rate of runoff given a panicular rainfall input, as measured under
standard conditions. For this analysis, MW used the K value from the existing permit document.
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