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n <br />LJ <br />Nodal results for preml of ng eondl tions reflect that no-mS nS ng related activities have <br />occurred within the watershed boundary, and that aasactated input parameeaca represent <br />exl sting conditions prior to arty mining activity. Assumptions for postmtni ng condt ti ons <br />that are reflected by the poabsi ni ng Tnput parameters Snclude: 1) A71 di sturbod areas <br />have been regraded, topsoilad and reseeded according to Crlterla outlined 7n this revi aed <br />permit application package; and 2) All temporary structures (007 pond, cul warts, et<.), <br />roads and other faeili ties have been removed antl reelaf med. <br />For both the premi ni ng end postmtnine swdel runs, the drainage area above the.007 pond was <br />delineated as one watershed. Dus to the relati valy small size of the drai nags area above <br />the pond, only one branch was eatabliahed Sn the Nateraheds for both pre- and postmT ni rig <br />eatlmates. Two junctions were eatah7i shad at the outlet of the wateraheda (loeati on of <br />the 007 pond), the ftrse to serve as the required junction on the one branch, the second <br />for providing a comprehenai ve outDut of the results. <br />Watershed areas and topograDfite measurements used to tleteref ne the Input Darameters for <br />both runs Here obtained iron 7:400 scale maps of the Nueia East Wining area (see Fxhf bf is <br />17-1 and 17-2). Tha postmi of ng topography map, Exhibit 20-10 Has used for calcul atirg <br />• posixri Wing input parameters that reflect basin charaeteristi es (average watershed slope, <br />time of concantrati on, etc.). A storm depth of 1.40 fnchea (5-year, 24-hour storm) With a <br />Type-il dtseri buts on was used for both pre- and poatni ni ng condl ti one. This storm value <br />was obtei Wed from the NOM Preei pitat:an Frequnncy Atlas of the Western Stares (NOM, <br />1973). <br />Hydrology input pe rametsra include watershed area, curve number end time of <oneent ration. <br />Curve numbers for pram{ Wing <ondi tt ons were eel acted by easi fining curve numbers to soda <br />and corresponding vegetation types mapped in the Nuela East ni nt ng area lsae Exhibit 9-3, <br />Tab 9, Soil Resources Survey, and ExhibTC 10-2, Tab 10, Vegatati on 8aselTne Survey). For <br />poet's{ ni ng eonditi ons, a curve number was estimated for two vegetation and soil types that <br />will be reestebli shad in the posbni nlrg watorahad above The 007 pond, irrigated pasture <br />(loam to sandy loam) and rangeland (loam to sanity loan). Curve numbers were easi fined to <br />each type accords ng to eri terla tar eel ectl ng eurw numbers outlined by the U.S. SoSI <br />Conservatt on Service and presented in design reports for each existing and proposed <br />aedtaient pond (see Attachments A through C, Tab 13, Fsciliti es). Table 17-27 presents the <br />soil and vegatati on types and aaaooiated curve number asst grmenta used to deterwf ne each <br />weighted average curve number for the 007 watershed. The Darcant areal di atri burl on of <br />17-03 Revt sad 04/11/AB <br />\I <br />REVISED MARCH 2006 Attachment 2.05.6(3)-2-95 <br />