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• PONDF.WK1 <br /> LILLYLANDS INC. <br /> PROTECTION OF THE HYDROLOGIC BALANCE 17 PPAWDuG <br /> 00 <br /> STORM EVENTS <br /> 10 YEAR 24 HOUR EVENT 1. 6 INCHES <br /> 25 YEAR 24 HOUR EVENT 2. 0 INCHES <br /> 100 YEAR 24 HOUR EVENT 2 .4 INCHES <br /> The run-off calculations presented below are calculated based <br /> on the manual - Procedures for Determining Peak Flows in <br /> L� Colorado - published by the Soil Conservation Service March <br /> 1984 . <br /> Curve numbers were developed using soil caracteristics and <br /> run-off control techniques. The soil types that are present <br /> -�, on the site are caracterized as having moderate permeability. <br /> According to the definition of the hydrologic soil groups, <br /> the soils on the site fall into the B hydrologic soil group. <br /> According to the vegetation study contained in Exhibit 5 <br /> the ground cover for the sagebrush community and the <br /> J-P woodland community are as follows: <br /> Veg Litter Total Curve No. <br /> Sagebrush 24.3 15.7 40. 0 51 <br /> Juniper Pinyon 25.3 16. 1 41.4 58 <br /> • Table 2-2d. - Run-off curve numbers for arid and <br /> semiarid rangelands - was used to pick the cuver numbers <br /> for the above two undisturbed vegetation communities. <br /> The table is from the second edition - June 1986 of the <br /> SCS manual referenced above. For simplication of the <br /> run-off calculations a curve number of 58 will be used <br /> for all of the undisturbed areas. <br /> The areas where the soil is void of vegetation because the <br /> topsoil has been redistributed is characterized as fallow <br /> ground and fallow ground with crop residue cover, or mulch <br /> in the case of a seeded and mulched area. Table 2-2b. - <br /> Runoff curve numbers for cultivated agricultural lands - <br /> shows that for fallow ground with crop residue, soil type <br /> B, good condition the curve number is 83 . Good condition <br /> is achieved by mulching the area to achieve a ground cover <br /> in excess of 20%. A curve number of 83 will be used for <br /> all disturbed areas. <br /> SEDIMENT POND F CAPACITY <br /> Sediment pond F is to be constructed in the southern <br /> portion of the mining area no. 3 . The new sediment <br /> pond F and the existing sediment pond B will <br /> contain the run-off from the area to be mined in <br /> the east half of section 33 , Mining Area No. 3 . <br /> 9-27 July 1992 <br />