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APPENDIX B <br />BOWIE NO. 2 MINE - COAL MINE WASTE DISPOSAL AREA <br />PROTECTION OF THE HYDROLOGIC BALANCE <br />STORM EVENTS <br />10 YEAR 24 HOUR EVENT 1.8 INCHES <br />25 YEAR 24 HOUR EVENT 2.1 INCHES <br />100 YEAR 24 HOUR EVENT 2.6 INCHES <br />The information presented for the 25 -year event peak flow calculations is developed <br />with the use of SEDCAD. The output data from SEDCAD follows this section. <br />The upland run -off areas are shown on Map No. 20 in Volume II. The run -off <br />curve numbers are developed based upon vegetation and soil types. Vegetation <br />data are presented in Volume III Exhibit 5 and shown on Map 3 in Volume li. <br />Soils data are presented in Volume III Exhibit 7 and shown on Map 4 in Volume IL <br />Ditches culverts and drainage plans are shown on Figure 2. <br />CURVE NUMBERS <br />Disturbed <br />Table 2 -2d -Runoff curve numbers for acid and semiarid rangelands <br />Cover Type - Herbaceous - mixture of grass, weeds and brush <br />Hydrologic Condition Poor <br />Soil Type - Loam C <br />Curve Number 87 <br />Previously Disturbed <br />The previously disturbed areas are the topsoil and coverfill stockpiles. <br />And the first bench of coal mine waste pile 92 <br />Table 2 -2d - Runoff curve numbers for and and semiarid rangelands <br />Cover Type - Herbaceous <br />Hydrologic Condition Good <br />Soil Type - Absarokee C <br />Curve Number 74 <br />Previously Disturbed <br />This area encompasses part of the drainage area for D -F4 that has <br />been previously disturbed, but now has a fair cover of vegetation. <br />Cover Type - Herbaceous <br />Hydrologic Condition Fair <br />Soil Type - Absarokee C <br />Curve Number 81 <br />TR -81 App. B -4 09/13 <br />