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• PONDF.WK1 <br />LILLYLANDS INC. <br />PROTECTION OF THE HYDROLOGIC BALANCE <br />• <br />STORM EVENTS <br />10 YEAR 24 HOUR EVENT <br />25 YEAR 24 HOUR EVENT <br />100 YEAR 24 HOUR EVENT <br />1.6 INCHES <br />2.0 INCHES <br />2.4 INCHES <br />The run-off calculations presented below are calculated based <br />on the manual - Procedures for Determining Peak Flows in <br />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 <br />the ground cover <br />J-P woodland com <br />Sagebrush <br />Juniper Pinyon <br />vegetation study contained in Exhibit <br />for the sagebrush community and the <br />nunity are as follows: <br />Veg Litter Total Curve No. <br />24.3 15.7 40.0 51 <br />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 />• <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 <br />July 1992 <br />