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0 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 <br />to 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 LISLE provides a basis for predicting the gross <br />erosion per acre from. an area on an annual basis. SEDCAD modeling, on the other hand, addresses <br />both runoff 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, LISLE provides a <br />reasonable basis for comparing sediment yield from undisturbed and reclaimed lands. The LISLE <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 LISLE 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)(.25)(6.2)(.049)(1.0) <br />= 2.28 x 0.9 = 2.05 tons per acre per year <br />• <br />R 30 SCS Map of R factors for Colorado <br />K 0.25 Trapper Permit C-81-010 Appendix Q <br />LS 6.2 SCS LS table; 510 feet, 15.7% <br />C 0.049 SCS C factor for Permanent Pasture, Rangeland, Idle Land, <br />and Grazed Woodland - 50% canopy cover (Permit No. C- <br />81-010, Table 2.3-13) - 55% effective cover, grass type <br />(Permit No. C-81-010, Table 4.4-2 ) <br />P 1.0 SCS P factor <br />11