Laserfiche WebLink
• For post-mining blocks, the USLE is calculated as: <br />-- - A(o~) =-(R)(K)(LS)(C)(P) - - - - - -- - - - <br />_(30)(.25)(1.7)(.010)(1.0) <br />= 0.13 tons per acre per year <br />- -R- - 30 -SCS Map of R-factors for Colorado - - - <br />K 0.25 Trapper Permit C-81-010 Appendix Q, Section XIII, Table E-3 <br />LS 1.7 SCS LS table (TR51, 1977); 300' slope length, 8% avg slope <br />- - -C ---0.010 -- SGS C-factor-for-Permanent Pasture, Rangeland, Idle Land, <br />and Grazed Woodland - no canopy, 85% herbaceous cover, <br />grass type (Table 1.2-1 of Bond Release submittal) <br />- P---- - 1.0 -SCSPfactor -- - - - <br />The USLE thus demonstrates that the existing condition of the reclaimed blocks results in equal or lesser <br />sediment contributions to surface runoff as compared to pre-mining conditions on an annual basis. <br />• 1.4.2 SEDCAD 4 <br />Trapper has developed site drainage and sedimentology models to estimate the total quantity of sediment <br />produced from a stone event for the runoff from each block under pre-mining end post-mining conditions. <br />The block drainage and sedimentology models were developed utilizing SEDCAD 4 for Windows, a <br />computer software program developed to assist in the evaluation of storm~vater runoff, erosion, and <br />sediment control management techniques. <br />To develop representative models of the pre-mining conditions in each block, baseline information from <br />the permit was utilized as input data in the SEDCAD 4 program. To develop comparative models <br />representing existing conditions for each block, the vegetation cover data outlined in Appendix 2 was <br />utilized as input into the SEDCAD 4 program with input parameters modified as appropriate in accordance <br />with this information. Given the irregular shapes of the blocks in relation to the topography and <br />recognizing that portions of individual blocks may fall within adjacent sub-watersheds, it is difficult to <br />develop specific pre and post-mining runoff models for each entire block. In order to develop <br />representative and comparable runoff models, typical twenty acre portions of each block were modeled <br />using the average slope and representative slope length for the entire block. A summary of the SEDCAD <br />4 program inputs and results for both the pre-mining and post-mining land wnditions are shown on Tables <br />• 1.4-1 and 1.4-2 respectively. The SEDCAD 4 computer printouts and input calculation sheets can be <br />found in Appendix 3. Input parameter references are also provided in Appendix 3. <br />8 <br />