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• Snowcap Coal Company <br />Protection of the Hydrologic Balance <br />Pond 8 <br />STORM EVENTS <br />10 YEAR 24 HOUR EVENT 1.4 INCHES <br />25 YEAR 24 HOUR EVENT 1.9 INCHES <br />100 YEAR 24 HOUR EVENT 2.2 INCHES <br />The information presented for peak flow calculations is developed with the use of SEDCAD. <br />The output from SEDCAD follows this section. <br />The drainage areas are shown on Figure 6C, Roadside South Portal Post Mining <br />Topography. <br />The soil map, Exhibit 23 shows the soil type as 66 - "Torziorthents, Wann-Rods Outcrop° <br />and 4 "Bari Clapper complex". Generally the soil samples for this and other disturbance areas <br />indicates the soil is sandy to silty loam (Tab Section 9) which equates to a "B" soil group. Clapper <br />has a published soil group of "B" in Table B-1 of Peak Flows in Colorado. The following CN's <br />were used in the calculations: <br />• Disturbed Area - 86 - B Soil Group, fallow bare soil. Used for portion of lower parking area, <br /> slopes for new road <br />Asphalt - 98 - B Soil Group, bare. Used for mine bench parking area, buildings. <br />Sage Grass - 64 - B Soil Group, 20% cover. <br />Previously Disturbed - 77 - B Soil Group, medium cover. Used for reclaimed refuse <br /> pile, portion of lower parking area and reclaimed slopes. <br />Gravel - 85 - B Soil Group, gravel. Used for new access road <br />RUN-OFF VOLUME - -Pond 8 <br /> Precip Direct Runoff <br />Area Acres Curve # Amount Runoff Vol A-F <br />Asphalt 2.78 98 1.4 1.18 0.27 <br />Disturbed 5.73 86 1.4 0.43 0.20 <br />Sage Grass 22.67 64 1.4 0.01 0.02 <br />Prev. Disturbed 11.95 77 1.4 0.17 0.17 <br />Gravel 0.34 85 1.4 0.39 0.01 <br />TOTAL 43.47 0.68 <br />TOTAL REQUIRED WATER VOLUME - - A-F 0.68 <br />• <br />SCC RSS-1 07/06 <br />