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<br /> <br />"_, <br />~. <br />The decision to select "medium" as the correct unit hydrograph <br />shape response, stemmed from conversations with Dr. Richard <br />Warner, author of SEDCAD and co-author of Applied Hydrology <br />and Sedimentology for Disturbed Areas. Attending Dr. Warner's <br />SEDCAD course last year afforded the opportunity to discuss <br />with him in quite some detail, the SEDCAD modeling of the <br />Colowyo Mine. Upon further discussion of Colowyo's specific <br />mining and reclamation practices, Dr. Warner felt, as did <br />MLRD, that the "slow" hydrograph response was not adequate. <br />Additionally, he felt that the "fast" hydrograph response was <br />also not adequate for Colowyo and is more representative of <br />deserts, pavement, or highly compacted disturbed soils. Hence <br />arose his recommendation to use the "medium" unit hydrograph <br />shape response. <br />35. SEDCAD Runs for Temporary Section 16 Ponds ~ <br /> <br /> The temporary Section 16 Pond has been deleted from the mine „_ ~,' <br /> plan. Reflecting this, Maps 12, 19, and 33A have been <br />~^~h <br />~ <br /> modified. Sediment control for this area will be handled by f <br /> the West Pit Pond which is adequately sized to account for <br /> this` area. <br />38. Mans 5 and 6. Mappincr Unit Letters <br /> The mapping unit letters tie to the letters used with the soil <br /> series further described in Section 2.04.9 Soils Resource <br /> Information. The letter designations were used by the Soil <br /> Conservation Service to indicate slope. For example a "D" <br /> indicates 3 to 12 percent slope and "E" indicates 12 to 25 <br /> percent slopes. The legends on both Maps 5 and 6 have been ~ ~, <br />~` <br />` <br /> corrected. " <br />'° <br /> ~I <br />j.~ <br />43. Minimum Topsoil Depth <br /> The appropriate changes have been made to page 4.06-3 to clear <br /> up any confusion regarding topsoil depth. <br />44. Sediment Load from Streeter Fill <br />The 0.96 tons/acre/year figure in earlier applications was <br />apparently a typographical error. The 3.17 tons/acre/year <br />figure currently reflects information contained in Exhibit 7, <br />Annexure F, Tipton and Kalmbach, page 5, January 14, 1982 <br />describing sediment yield for Streeter Gulch. Since the pond <br />was initially designed using this correct figure, no changes <br />are necessary. <br />45. Prospect Pond Access Road <br />The appropriate design plans and maps are included in Exhibit <br />7, Hydrology Information, Item 8, Design of Surface Runoff <br />Control Struc~ure=, ?armit Revision, 1991. <br />