2020-12-12_REVISION - C1981010

• Permit No: C1981010
• IBM Index Class Name: Revision
• Doc Date: 12/12/2020
• Doc Name: Proposed Decision and Findings of Compliance
• From: DRMS
• To: Trapper Mining Inc
• Type & Sequence: SL22
• Permit Index Doc Type: Findings
• Email Name: JLE
• Email Name: RAR
• Media Type: D
• Archive: No

Table 4. USLE Variables and Basis for Selection
Pre-mining
Variable Trapper's Trapper's Source Division's Comment
Selection
R 30 SCS Map: R factors for Colorado Reasonable, as per Trapper's
location on R factor map.
Trapper Permit C1981010 Appendix Q Section Reasonable, as per soil types of
K 0.25 XIII ,Table E3 bond release blocks delineated
on map M29.
LS 8.92 SCS LS Table, 748 ft, 17.5%Slope Reasonable based on the 17.5%
slope and 748 ft. slope length
Reasonable as per pre-mining
rangeland conditions and
C 0.05 SCS C factor table for specified conditions applicable C value tables 2.3-13
and 4.4-2.
Reasonable as per erosion
control practice factor,
P 1 SCS P factor table for specified conditions consistent with premiing
practice on bond release
blocks.
Table 4 cont. USLE Variables and Basis for Selection
Post-mining
Variable Trapper's Trapper's Source Division's Comment
Selection
R 30 SCS Map: R factors for Colorado Reasonable, as per Trapper's
location on R factor map.
Trapper Permit C1981010 Appendix Q Section Reasonable, as per soil types on
K 0.25 XIII bond release blocks delineated
on map M29.
LS 8.92 SCS LS Table, 748 ft. 17.55%Slope Reasonable based on the 17.5%
slope and 748 ft. slope length
SCS C factor table for permanent pasture,
rangeland, idle land and grazed woodland - Reasonable as per vegetation
C 0.033 data submitted with SL22
no canopy, 74.1 herbaceous cover,grass type
(Table 1.2-1 of bond release application. application (Table 1.2-1).
P 1 SCS P factor table for specified conditions Reasonable, as no control
practices were utilized.
SEDCAD Comparison: Trapper utilized baseline data for selecting SEDCAD 4 parameters for
modeling pre-mining conditions. Trapper utilized recent vegetative data in the bond release submittal
for modeling post-mining conditions. The parameters employed in the SEDCAD model and their
definitions are presented in the table below:
Permit Number C1981010
SL22 Page 13 of 18