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• Watershed Analysis Rule 2.06.5(2)(d) <br />Rule 2.06.5)(2)(d)(ii) <br />The above rule requires the total volume of flows from the permit area, during every <br />season of the year, will not vary in a way that adversely affects the ecology of any surface <br />water or any existing or planned use of surface or ground water. <br />The volume of flow from the disturbed and reclaimed area can be estimated using runoff <br />curve numbers presented in the handbook, Procedures for Determining Peak Flows in <br />Colorado, Soil Conservation Service. Table 2-2d., Runoff curve numbers for avid and <br />semiarid rangelands will be used to select the appropriate curve number. <br />Both the reclaimed and the pre-mined area have fair ground cover. The soil type in the <br />area is Saraton-Agua Fria complex which is hydrologic soil group C. The cover type for <br />the reclaimed area will be herbaceous which yields a curve number of 81. The cover type <br />for the pre-mined area is Pinyon juniper which yields a curve number of 73. <br />Based upon the difference in curve numbers, the reclaimed area will generate more run-0ff <br />than the pre-mined area. The 10-year storm (1.8") event would generate 0.02 inches of <br />runoff from the pre-mined area and 0.04 inches or runoff from the reclaimed area. The <br />reclaimed facilities area totals approximately 40.8 acres, therefore runoff generated by the <br />• pre-mined and reclaimed area would be 0.07 and 0.14 acre-feet respectively. <br />Stevens Gulch, an ephemeral stream, drains approximately 5,080 acres (permit page 49) <br />which is over 124 times larger than the reclaimed area. The additional surface runoff <br />generated by the reclaimed area is therefore insignificant when compared to the runoff <br />generated from the entire Stevens Gulch drainage. The additional surface runoff <br />generated from the reclaimed area will therefore not adversely affect the ecology of any <br />surface water or any existing or planned use of surface or ground water in the Stevens <br />Gulch drainage. <br />Rule 2.06.5)(2)(d)(iii) <br />The Division's approval of this plan should suffice for the appropriate State environmental <br />agencies approval of the plan. <br />• April 98 <br />4xiii <br />l R-zB~Rn,-o3 <br />f)PP,eoVED Iz~~y~9~ <br />