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REV103359
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Last modified
8/25/2016 1:14:11 AM
Creation date
11/22/2007 1:05:33 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Revision
Doc Date
10/1/2001
Doc Name
PHASE II BOND RELEASE APPLICATION SL-3
From
TRAPPER MINING INC
To
DMG
Type & Sequence
SL3
Media Type
D
Archive
No
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surface resulting from farming practices utilized in the area. For reclaimed surfaces, higher representative <br />• slope lengths for overland flows (300') are utilized to comparatively characterize the relatively smoother <br />surface conditions influencing the concentration of runoff flows from alfalfa/grass hay cropped areas. <br />Further distinctions between the reclaimed lands and pre-mining conditions are characterized using the <br />Control (C) and Support Practice (P) factor model input variables. The C factors used in the models are <br />obtained from the SCS Erosion Handbook, Water and Wind, 1988, and the SEDCAD 4 table for <br />Permanent Pasture, Rangeland, Idle Land, and Grazed Woodland utilizing <;over and canopy data as <br />appropriate. For pre-mining conditions, the "C" factor (0.20) for a winter wheat 8 fallow cropping <br />sequence utilizing minimum tillage practices and producing approximately SOLD lbs. of crop residue was <br />selected. The local NRCS office was consulted for assistance in selecting the appropriate cropping <br />sequence and crop residue estimates. For post-mining conditions, "C" values for permanent pasture, <br />rangeland, idle land and grazed woodland exhibiting no appreciable canopy are utilized along with the <br />actual herbaceous cover values existing on the reclamation as deterrined by direct transact <br />measurements. Support Practice (P) factors are chosen to describe the effects of contour farming <br />operations on the pre-mined lands (0.6) and the lack of conservation practice implementation on the <br />reclaimed areas (1.0). <br />• In both instances, the SEDCAD 4 models demonstrate the total sediment generated from the recaimed <br />blocks is less than the total sediment generated from the same blocks unifier pre-mining conditions. <br />These results are primarily ariributable to the different management practiceso employed in utilizing the <br />lands for alfalfa/grass hay production as opposed to wheat farming. <br />1.4.3 CONCLUSIONS - <br />Both the USLE and SEDCAD 4 evaluations demonstrate that existing conditions will result in equivalent or <br />lesser sediment contributions to surface runoff when compared with pre-mining levels as determined by <br />baseline data. Each methodology possesses certain strengths and limitations and each offers a distinct <br />and different view of the test required to meet Phase II criteria. The soil erodit~ility, C-factor and P-factor <br />variables are critical to both approaches along with the distinctions drawn regarding representative slope <br />lengths. For the SEDCAD 4 methodology, curve number selections are importemt as well. Both methods <br />account for and reflect the outstanding cover percentages established on the 1-rapper reclamation in the <br />areas being evaluated in addition to characterizing important distinctions in land management practices <br />which have acted to significantly decrease erosion and sediment transport from these reclaimed lands as <br />compared to pre-mining conditions. Trapper believes these demonstrations provide a sound basis to <br />conclude that equivalent or lesser sediment contributions as compared to baseline conditions can be <br />• expected from the reclaimed blocks addressed by this application. <br />11 <br />
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