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Watershed Analysis Rule 2.06.5(2)(d) <br />The above calculations demonstrate that the soil loss from the approved area is equal to <br />1.13 Acre-feet (three year sediment volume). The soil loss from the proposed area is <br />equal to 1.07 Acre-feet (three year sediment volume). Therefore, the proposed <br />configuration of the RSS area will reduce the amount of total suspended solids discharged <br />to the surface waters as compared to such discharges in the approved reclamation plan. <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 arid and <br />semiarid rangelands will be used to select the appropriate curve number. <br />The soil Map, Exhibit 23 shows the soil type as 66 "Torriorthents, Warm-Rock Outcrop" <br />• and "Banc Clapper complex". Generally the soil samples for this and other disturbance <br />areas indicates the soil is sandy to silty loam (Tab Section 9) which equates to a "B" soil <br />group. Clapper has a published soil group of "B" in the Table B-1 of Peak Flows in <br />Colorado. <br />Based upon the difference in configuration, the proposed area will generate more run-off <br />than the approved area. The 10-year storm (1.4") event would generate 0.05 inches of <br />runoff from the approved area and 0.17 inches of runoff from the proposed area. The <br />proposed facilities area totals approximately 48.9 acres, therefore runoff generated by the <br />approved and proposed area would be 0.21 and 0.69 acre-feet respectively. <br />The additional surtace runoff generated by the proposed area (0.48 AF) into the Colorado <br />River is insignificant when compared to the runoff generated from the entire Colorado River <br />drainage (2.8 million acre-feet per year). The additional surface runoff generated from the <br />proposed area will therefore not adversely affect the ecology of any surface water or any <br />existing or planned use of surface or ground water in the Colorado River Drainage <br />drainage. <br />• PR-03 A14-9-12 02/07 <br />