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2023-09-05_REVISION - C1981010
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2023-09-05_REVISION - C1981010
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Entry Properties
Last modified
9/6/2023 8:42:16 AM
Creation date
9/5/2023 9:38:52 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Revision
Doc Date
9/5/2023
Doc Name Note
Application & Revised Pages
Doc Name
Proposed Revision Materials
From
Trapper Mining Inc
To
DRMS
Type & Sequence
SL24
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 /> Ave)= (R)(K)(LS)(C)(P) <br /> = (30)(0.25)(8.11)(0.050)(1.0) <br /> =3.04 x 0.9=2.74 tons per acre per year <br /> R 30 SCS Map of R factors for Colorado <br /> K 0.25 Trapper Permit C-1981-010 Appendix Q <br /> LS 8.11 SCS LS table; 719 feet, 16.7% <br /> C 0.050 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 1.0 SCS P factor <br /> 11 <br />
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