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2. Provide an emergency spillway capable of passing runoff from the 100-year, 24-hour • <br />storm event; <br />3. Fro vitle adequate storage Ior sediment generated as determined f[cm Che Sedcad+ <br />computer pro9[am. <br />4, Provide a noncloogrnq dewaterinq device and principal spillway that wt11 provide <br />adeq ua[e detention time for the 10-year, 24-hour storm event and still allow a <br />method [o dewater the pond tlaan to the 100 percent sedrment s[o rage level in a <br />reasonable amo un[ of time. <br />H';d relogy The hydrd ogy of the watershed was analyzed utilize ng [he SEDCAD+ computer <br />program. SEDCAD~ is an onhanced PC version of the SEDIHOT II computer p[egram written by <br />Civil Software Design of Lexington, Kentucky. Tab 13, Attachment 13-1, contains a <br />listing and description of [he SEGCAD input va r[aoles. In performing this analys i's, the <br />characteristics of the mi nesite end [eclamatiun proc=lures along with or.-sit= sediment <br />contro'_ procedures were considered. Addendum, A, B, and C con[a rn, a complete Listing of <br />the SEDCAD+ inou[s and outputs fer the 10-year, 25-year, and the 100-year design storms. <br />Table 13-4A-1 contains the design hyd re logy summary. <br />TABLE 13-aA-1 <br />DESIGIJ H'l DROLOG'i SUi~AtAF'i <br />E'OUD 011 AS-BUILT <br />Description 10-Yr,°4-Hr '_5-'li,24-Hr 1i~0-Y r, C4-Hr <br />Pr ecrpiiation Depth 1. 7 in. 3. 1 in. 2. 5 in. <br />Inflow Rcnoff 'JC lunge 2 .54 ac-`.L 3. 78 ac-ft ... 36 ac-ft <br />Pond Vo 1um.=_ a*_ E'eak Sraye 4. 33 arf[ 5. 12 ac-f[ 5. 20 ac-f[ <br />Peak Stage Elevation 7006. 67 700P . 04 7008 .18 <br />Peak Inflow Raie 31. UB cfs 41. 81 cfs 52 .64 cfs <br />Fea Y. Dis r_harge Fate 4. 78 cfs 38. 10 cfs 50 .08 cfs <br />Input consists of precipitation amount (inched, watershed area lacres), time of <br />concentration (hours), runoff curve numUer ICU 1, representat i've particle-size <br />distributions of soils in the area, sedimen[ology information, spillway information, etc. <br />The drainage area for this sediment pond was measured on a 1"=400' topographic map (see <br />Exhibit 13-2 ',. <br />i 3-aA-2 F.e'~ri s_d 12i 12/97 <br /> <br />