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<br />III IIIIIIIIIIIII III <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Departmem of Natural Resources <br />1313 Sherman 51., Room 215 <br />Denver, Coloracb 80203 <br />Phone: 1}Oli 866-3567 <br />FA%:13031832-8106 <br />MEMO <br />Date: December 16, 1999 <br />Frotn: Tom Kaldenbach 1r~ <br />To: SL-02 file for Trapper Mining Inc., Permit C-81-010 <br />DIVISION OF <br />MINERALS <br />GEOLOGY <br />RECLAMATION <br />MINING•SAFETY <br />&II Owens <br />Governor <br />Greg E Watcher <br />EAecmrve DireUOr <br />Michael B. Long <br />Drvnion Dveclor <br />Re: Reasonableness of Trapper's selection of variables and parameters in USLE calculation <br />and SEDCAD runs (on pages ]0 - 14 of SL-02 submittal) <br />The following tables summarize my basis for concluding that Trapper selected reasonable <br />variables and parameters in the above-referenced Phase II bond release sedimentology <br />demonstration. <br />Table 1 -USLE calculation: Pre-minine <br /> <br />Variable Trapper's <br />Trapper's source Division's comment on <br />' <br /> selection Trapper <br />s selection _ <br />R 30 SCS map of R factors for Reasonable based on Trapper's <br /> Colorado location on the R factor m~___ <br /> Reasonable because the Division <br /> previously recognized the validity of <br />K 0.25 Trapper petmit C-81-010 the 0.25 value for Trapper's <br /> Appendix Q premining lands when Appendix Q <br /> was approved as part of [he permit <br /> a lication. <br /> Reasonable because a 15.7%n slope, <br />LS 6.2 SCS LS table; S l0 ft., 15.7%o 510 feet long accurately represents <br /> the re-minin draina es. <br /> SCS C factor for permanent <br /> pasture, rangeland, idle land, Reasonable because the selected <br /> and grazed woodland - 50%n <br />characteristics accurately represent <br />C 0.049 canopy cover (Permit C-81-010, the premining land use and <br /> Table 2.3-13) - 55% effective <br /> cover, grass type (Permit C-81- vegetation. <br /> 010, Table 4.4-2) <br /> Reasonable. No adjustment for <br />P 1.0 SCS P factor table conservation practices is appropriate <br /> because premining ground has not <br /> been worked. <br />Page 1 <br />