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<br /> <br />• demonstration. Resolution of these minor details will allow us to apply the <br />demonstration to several areas of rlie mine, thereby resolving pending <br />drainage control problems. <br />Response: Question VII.22 requests that the following changes be <br />made in the drainage design parameters: <br />• For premining conditions use Table 2.2d (Runoff curve <br />numbers for grid and semiarid rangelands) rather than <br />Table 2.2c (Runoff curve numbers for other agricultural <br />lands). <br />• For premining conditions use the sagebrush-grass rather <br />than brush or herbaceous vegetation category. <br />• Increase the premining slope length from 150 to 250 feet. <br />• In determining the CP (Control Practice) factor, include <br />herbaceous as well as woody cover in determining canopy <br />• cover percentage, and reflect all cover (herbaceous, <br />woody, litter, and rock) in determining percent ground <br />cover. <br />Revised drainage calculations have been completed incorporating the <br />requested changes. The revised calculations and methodology <br />discussion are included with these responses as Appendix A, Drainage <br />Design Information. <br />6) Be°sure that all hydrologic calculations are properly certifred. <br />Response: Certifications are required for diversion of perennial, and <br />intermittent drainages, and those ephemeral drainages with a drainage <br />area greater than one square mile above the diversion consistent with <br />Rule 4.05.4(2}. Design of all sedimentation ponds must also be <br />certified in accordance with Rules 4.05.06(7) and 4.05.9(8). <br />~~ <br />5- <br />