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2020-09-03_REVISION - C1981010
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2020-09-03_REVISION - C1981010
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Entry Properties
Last modified
9/4/2020 11:22:13 AM
Creation date
9/4/2020 8:37:22 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Revision
Doc Date
9/3/2020
Doc Name Note
Application & Revised Pages
Doc Name
Proposed Revision Materials
From
Trapper Mining Inc
To
DRMS
Type & Sequence
SL22
Email Name
RAR
JLE
Media Type
D
Archive
No
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1.4 Sediment Control Demonstration <br />According to CDRMS regulation 3.03.1(3)(b), Phase II bond release liability cannot be granted until the <br />applicant demonstrates that existing conditions will result in equivalent or lesser sediment contributions to <br />surface runoff when compared with pre -mining levels as determined by baseline data. <br />To demonstrate that runoff from each block will result in equivalent or lesser sediment contribution as <br />compared to baseline conditions Trapper is including two evaluations; Universal Soil Loss Equation <br />(USLE) calculations and a SEDCAD analysis. The USLE provides a basis for predicting the gross erosion <br />per acre from an area on an annual basis. SEDCAD modeling, on the other hand, addresses both runoff <br />and erosion estimates and provides results on the basis of single storm events. <br />1.4.1 Universal Soil Loss Equation <br />The Universal Soil Loss Equation (USLE) provides a mechanism to predict the gross annual erosion <br />occurring on a given area. The technique does not account for the deposition of eroded sediment within <br />the area being evaluated. Nonetheless, within the bounds of certain assumptions, USLE provides a <br />reasonable basis for comparing sediment yield from undisturbed and reclaimed lands. The USLE <br />calculations presented are based upon an approach applied by the Colorado Division of Reclamation, <br />Mining and Safety (CDRMS) to assess the Phase II sediment control criteria for reclaimed blocks <br />submitted under the SL -1 Bond Release Application. Previous calculations by the Division suggest the <br />sediment yield from reclaimed areas is approximately 10% higher than that occurring on undisturbed <br />areas. This assumption is utilized in this assessment. For the pre -mining block value, the USLE is <br />calculated as follows using the area -weighted average values applied to blocks according to range site <br />classification: <br />A(pre) = (R)(K)(LS)(C)(P) <br />= (30)(0.25)(8.92)(0.050)(1.0) <br />= 3.35 x 0.9 = 3.02 tons per acre per year <br />R <br />30 <br />SCS Map of R factors for Colorado <br />K <br />0.25 <br />Trapper Permit C-1981-010 Appendix Q <br />LS <br />8.92 <br />SCS LS table; 748 feet, 17.5% <br />C <br />0.050 <br />SCS C factor for Permanent Pasture, Rangeland, Idle Land, <br />and Grazed Woodland — 50% canopy cover (Permit No. C-81- <br />010, Table 2.3-13) — 55% effective cover, grass type (Permit <br />No. C-1981-010, Table 4.4-2 ) <br />P <br />1.0 <br />SCS P factor <br />11 <br />
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